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Study on incidence of lamb morbidity and mortality and associated risk factors in the mixed crop-livestock production system of Gewata District, Kaffa zone, southwestern Ethiopia

Study on incidence of lamb morbidity and mortality and associated risk factors in the mixed... Lamb morbidity and mortality cause significant loss in a smallholder production system. A longitudinal prospective survey was conducted on 408 randomly selected farmers located in six purposefully selected kebeles in Gewata woreda from June 2020 to July 2021 to determine the incidence of morbidity and mortality in lambs and to identify risk factors. For this purpose, 408 lambs from the Gewata district’s mixed crop-livestock production system were examined every day from birth to three months of age. The data was analyzed using the Kaplan-Meier (K-M) method, the log-rank test, and Cox proportional hazards regression. Results showed that the cumulative incidence of all- cause of morbidity and mortality at the end of three month was 12.86% (95% CI: 10.26–16.13%), and 6.86% (95% CI: 5.03–9.35%), respectively. Diarrhea was the leading cause of morbidity and mortality, accounting for 49.33 and 50% morbidity and mortality, respectively. Pneumonia was the second most frequent cause of morbidity and death. In the K-M hazard analysis, the greatest risk of lamb morbidity and mortality was observed during the first month of life, and then the risk decreased significantly as the lamb grew. Of the 17 potential risk factors studied, the multivariable Cox proportional hazards regression model showed that lamb sex, birth weight, umbilical care, time and method of colos- trum feeding were the five predictors that were significantly associated with a higher risk of morbidity, whereas birth weight, lambing difficulty, dams’ parity, method and time of colostrum feeding were the five predictors that were significantly associated with a higher risk of mortality. Moreover, a higher risk of morbidity was observed in lambs with methods of colostrum feeding after birth (HR = 3.158; p = 0.000) and with variations in birth weight (HR = 1.418; p = 0.003). Similarly, the mortality risk was 4.926 (p = 0.047), 4.023 (p = 0.012), and 3.206 (p = 0.000) times higher in lambs with lambing difficulties, at the time of colostrum feeding, and by the method of colostrum feeding, respec- tively. According to this research, lamb morbidity and mortality rates in the study area are significantly high which has a great impact on the replacement stock and production. Hence, awareness should be created among farmers concerning improved lamb management practices. Keywords Gewata, Incidence, Lamb, Morbidity, Mortality, Ethiopia *Correspondence: Haben Fesseha haben.senbetu@wsu.edu.et Full list of author information is available at the end of the article © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. The Creative Commons Public Domain Dedication waiver (http:// creat iveco mmons. org/ publi cdoma in/ zero/1. 0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Fesseha et al. Animal Diseases (2023) 3:11 Page 2 of 13 Khan et  al. 2006). To completely appreciate the causes of Introduction lamb morbidity and mortality, it is also necessary to com- Ethiopia has approximately 30.7 million heads of sheep prehend the associated risk factors (Fentie et  al. 2016; and is Africa’s second-largest sheep population (Central Hadgu et  al. 2021; Mohammed et  al. 2020; Hordofa et  al. Statistical Agency 2019). Sheep breeds are widely spread 2021). Genetic, environmental and management factors across the country’s diverse ecosystem, ranging from were the most important determinants of lamb mortality subalpine to dry lowlands, as well as production practices and morbidity. These include lamb’s birth weight, sex, dam (Gizaw et al. 2007; Tibbo 2006). Short-tailed, long-tailed, parity and age, colostrum immunoglobulin transfer, lamb- thin-tailed, and fat-tailed sheep are among the 14 tradi- ing season and year, dam body weight during lambing, and tional sheep populations of the country and are divided litter size (Hadgu et  al. 2021; Fogarty et  al. 2000; Dalton into four major groups based on tail type (Galall 1983). et al. 1980; Sawyer et al. 1977; Wiener et al. 1983). Additionally, using a microsatellite DNA marker, Ethio- The Kaffa zone has a large potential for a small rumi - pian researchers found nine breeds and six genetically nant population kept by smallholder farmers as a sole diverse sheep breed groupings that are scattered across or supplementary source of cash income (Ortiz 1983). the nation in various agroecology and production meth- Although small ruminant production provides food secu- ods (Gizaw et al. 2007; Solomon et al. 2008). rity for sheep producers, disease, poor nutrition, poor In Ethiopia, mixed crop-livestock production accounts animal production systems, reproductive inefficiency, for 75% sheep population, while pastoral and agro-pasto- management constraints, inadequate veterinary care, ral farming accounts for the remaining 25%. They oper - and lamb mortality have a great impact on smallholder ate on a large production system with minimal effort and producers. Lamb morbidity and mortality are one of the produce the lowest carcass weight compared to other most evident constraints to sheep producers’ profitability East African countries (Solomon et  al. 2008). Due to in most countries, resulting in a shortage of replacement ecological, economic and cultural variations, the aim of stock. The rate of survival of lamb produced determines maintaining sheep varies from place to place. They are, the success of any breeding program, as well as the future however, by and large, save for exceptional makes use of of sheep production. For farmers and cattle herders to together with earnings generation, meat, milk, skin, wool, get the most out of their livestock resources, it’s critical manure, security, gifts and non-secular rites (Edea et  al. to develop efficient livestock production that can pre - 2010). vent losses of young stock. Hence, the major cause of One of the major production challenges affecting sheep lamb stock morbidity and mortality should be identified and goat productivity is the high pre-weaning mortal- and estimated to develop a sustainable control program. ity of young lambs and kids (Singh et al. 2009). The term Keeping these aspects in view, the current study was con- “preweaning mortality rate” (PWMR) refers to the num- ducted to assess the incidence of morbidity and mortality ber of lambs that die between birth and weaning, includ- from birth to weaning and potential risk factors in lambs ing neonatal mortality (International livestock center for of the Gewata district, Kaffa zone, southwestern Ethiopia. Africa 1998), especially in the neonatal stage (from birth through the first 28d of life), which is the most essential for lambs (Gokce et  al. 2014). The study on Ethiopian Results highlands revealed that a high level of neonatal lamb Descriptive epidemiology mortalities was recorded both on-station (46.3%) and on- In this study, 408 farmers in a mixed crop-livestock pro- farm (51.5%) (Bekele et  al. 1992a), whereas the study of duction system with at least one lamb less than 3 months Rift Valley areas of Ethiopia showed that 46.8% prewean- of age in their flock were interviewed from six kebeles of ing kids death and 30.3% neonatal kid death, especially Gewata district, Kaffa Zone, Southwest Ethiopia. Of the till 1 month of age (Fentie et al. 2016). 408 respondents, 81.86% were men, while 18.14% were In Ethiopia and other parts of the world, lamb mortal- women. The age categories of the respondents in the ity can only be reduced by recognizing and addressing 18–30 years, 31–40 years, and 41–50 years age groups the underlying causes (Kirk and Anderson 1982), such as were 46.32, 33.58, and 15.20%, respectively. The remain - infectious conditions (pneumonia, liver fluke, diarrhea and ing age groups were above, and regarding this age dis- pneumo-enteritis) and non-infectious conditions (starva- tribution of the respondents, the majority were grouped tion/chilling exposure complex, stillbirths/dystocia, mis- by productive age. The level of education is the most mothering, low birth weight, breed, ewe’s age, neonate’s basic criterion for determining a society’s standing. A immunity gained through colostrum, dam’s parity and literate community is more capable of comprehending lamb’s sex, injury and poisoning) (Fentie et al. 2020; Hadgu and completing various agricultural activities. The find - et  al. 2021; Islam et  al. 2015; Lorenz et  al. 2011; Moham- ings revealed that 17.16 and 27.94% respondents were med et  al. 2020; Binns et  al. 2002; Hordofa et  al. 2021; F esseha et al. Animal Diseases (2023) 3:11 Page 3 of 13 illiterate and read and write, respectively. Others, 28.18 during the second and third months of life, and then and 12.75% had completed elementary and secondary the risk decreased significantly as the lamb grew older education levels, respectively, and the remaining 4.17% (Table 3). were above secondary (Table 1). Of the total sampled lamb, 54.17% were male and Causes of morbidity and mortality 45.83% were females. A significantly high number of Diarrhea was the leading cause of morbidity and mor- owners care for umbilical (66.91%) and fed colostrum tality accounting for 49.33 and 50.00% morbidity and by suckling (56.13%) within 6h (51.72%). Regarding mortality, respectively. Pneumonia was the second most the birth type, the highest number (57.87%) were born frequent cause of morbidity and death. Table  4 lists the twice, and the least number was born triple (2.94%). other prevalent causes of lamb morbidity and mortality. Moreover, 60.78% lambs were born with lambing dif- ficulty, 85.54% dams’ parity was multiparous, and the Risk factors for lamb morbidity and mortality highest number of lambs was weighted between 3.1– Univariable analysis 3.5 kg (34.80%). In this study, 78.68% were sampled In this study, the effect of six kebeles host and man - in the wet season, 54.17% were managed under poor agement factors on lamb morbidity and mortality was hygiene, and 72.55% was mixed with other weaned lamb assessed using the Log-rank test, and potential predictors in the flock (Table 1 ). for the final multivariable analysis were selected based on the results. From there, the variables with p-values less than 0.25 were selected for the multivariable analysis of Lamb morbidity and mortality rate the risk factors, totaling 12 variables for morbidity and 11 Of the 408 lambs that were observed in this study, disease variables for mortality (Table 5). incidences and deaths in the study lamb were recorded up to three months of age, after which no morbidity or Multivariable analysis mortality events were noted. As a result, the data were truncated after three months and accordingly the over- Lamb morbidity rate The incidence rate of lamb mor - all morbidity and mortality rates are calculated as 12.86 bidity was found to be significantly (p  < 0.05) impacted cases per 100 lamb months and 6.86 cases per 100 lamb by lamb sex, birth weight, Umbilical care, method and months at risk, respectively. The highest morbidity and time of colostrum feeding in the final multivariable Cox mortality (18.60 and 8.69) were observed in Bako-Shuta regression analysis model. Accordingly, compared to and Wodiyo, respectively. Similarly, the lowest morbid- their counterparts, lamb sex (HR = 0.265), and umbili- ity and mortality (4.17 and 0) were observed in Buta, and cal care (HR = 0.473) had a lower risk of morbidity. In Bako-Shuta, respectively. Besides, morbidity and mortal- contrast, the method of colostrum feeding had the high- ity of lamb based on origin or kebele were presented in est risk of morbidity (HR = 3.158) (Table  6). The final Table 2. model was tested for the proportional hazards assump- tion and found not to violate the assumption (global test: Kaplan‑Meier survival analysis Chisq = 10.77; df = 16; p = 0.8235). The cumulative survival probability of lamb to all-cause morbidity by colostrum intake time and mortality by Lamb mortality rate The final multivariable Cox haz - dams’ parity is showed in Figs.  1 and 2, respectively. ard regression analysis model revealed that among the To better visualize the cumulative survival probabil- assessed potential risk factors,  such as birth weight, ity or incidence of morbidity or mortality from birth to lambing difficulty, dams’ parity, method, and time of three months of life, the same data were also presented colostrum feeding all had a statistically significant using the K-M life table (Table  3). The K-M survival (p < 0.05) impact on the lamb mortality rate. In compari- curves show a significant decrease at end of each month son to their counterparts, the mortality risk was lower with a constant across respective months in the survival in the birth weight of lamb (HR = 0.379), and dams’ par- probability of lamb with increasing age. Disease events ity (HR = 0.223). On the other hand, lamb from a ewe were recorded in all age groups. with lambing difficulty exhibited a higher mortality risk Using the Kaplan-Meier method, we calculated the risk (HR = 4.926) (Table 6). The final model was tested for the of morbidity and mortality at the end of each month until proportional hazards assumption and found not to vio- the lambs were three months old. As a result, the great- late the assumption (global test: Chisq = 7.37; df = 16; est risk (hazard) of morbidity and mortality was observed p = 0.9656). Fesseha et al. Animal Diseases (2023) 3:11 Page 4 of 13 Participatory investigation of causes of lamb morbidity Table 1 Respondents’ feedback on their demography, lambs’ health, and management in the mixed crop-livestock production and mortality in the study area system of Southwest Ethiopia During the focus group, key informants’ discussion was local names, in order of importance, experience with Variable Category Frequency Valid percent (%) lamb health problems and methods of prevention and control, key health issues for each level, and diseases or Origin/Kebele Wodiyo 115 28.19 conditions that cause illness and death in lambs. Identify- Imicho 89 21.81 ing and ranking area sheep production limits, ranking or Dumo 62 15.20 prioritizing morbidity and mortality causes, and discuss- Boka-Shuta 28 6.86 ing sheep morbidity and mortality time trends (seasonal Alargeta 46 11.27 calendar). In terms of lamb health concerns, the research Buta 68 16.67 area’s preventative and control methods were not thor- Owner age (years) 18–30 189 46.32 oughly tested. The participants stated that during lamb 31–40 137 33.58 diseases, they did not pay attention to sick lambs due to 41–50 62 15.20 > 50 20 4.90 a lack of knowledge and the distance to an animal health Sex (owner) Male 334 81.86 facility where the sick lamb might be treated. Female 74 18.14 As discussed during focus group discussion (FGD) and Education status Illiterate 70 17.16 key informants, major health problems in the study area Read and write 114 27.94 were infectious diseases and insufficient facilities for vet - Elementary 155 28.18 erinary services were major animal health problems in Secondary 52 12.75 the area. Diseases or diseases causing factors and death Above 17 4.17 in lambs were identified and ranked in the study area. Flock size 2–4 136 33.33 Importance and local name: Diarrhea (#1), Pneumonia 5–7 145 35.54 (#2), Dysentery (#3), endoparasites (#4), and conception. > 8 127 31.13 (#5) (Table  7). Diseases, shortage of animal health pro- Lamb sex Male 221 54.17 fessionals, shortage of drugs, and vaccination time were Female 187 45.83 enumerated as constraints of sheep production in the Birth type Single 160 39.22 study area. Twice 236 57.84 According to FGD and key informants, infectious dis- Triple 12 2.94 ease (1st), mismothering starvation exposure (2nd), Birth weight (kg) ≤2 28 6.86 predator (3rd), management (4th), and unknown causes 2–2.5 39 9.56 (5th) were identified and ranked as the causes of lamb 2.6–3 97 23.77 morbidity and mortality in the study area. The wet season 3.1–3.5 142 34.80 and dry season were responsible for lamb morbidity and ≥3.6 102 25.00 mortality in the research region, according to temporal Lambing difficult Yes 160 39.22 patterns (seasonal calendar). The causes of lamb mor - No 248 60.78 bidity and mortality in the study area were discussed by Dams’ parity Primiparous 59 14.46 Multiparous 349 85.54 focus group discussants and key informants during the Season of birth Wet 321 78.68 dry season because of a lack of available feeds for ewes Dry 87 21.32 to produce enough milk for lambs. In the wet season, the Hygiene Poor 221 54.17 pasture was contaminated by floods and the season was Good 187 45.83 favorable for microorganism multiplication (Table 7). Mixing of different Yes 296 72.55 weaned lamb No 112 27.45 Discussion Umbilical care Yes 273 66.91 The mortality and morbidity of lambs before weaning are No 135 33.09 major factors in reducing profitability by causing signifi - Method colostrum feed Suckling 229 56.13 cant losses in sheep production, which negatively affects Hand feed 98 24.02 sheep and livestock production (Hadgu et  al. 2021). In Not feed 81 19.85 the current study, the cumulative incidence of all-cause of Time of colostrum feeding ≤ 6 hrs 211 51.72 morbidity and mortality observed was 12.86 and 6.86%, 6-12 hrs 164 40.20 respectively. This finding is the first incidence report on ≥12 hrs 33 8.09 lamb morbidity and mortality in the study area. F esseha et al. Animal Diseases (2023) 3:11 Page 5 of 13 Table 2 Morbidity and mortality rate of lamb in the mixed crop-livestock production system of Southwest Ethiopia based on origin Origin No. of  lamb at risk No. of cases Time at risk (months) IR /100 lamb month 95% CI for IR Morbidity Wodiyo 115 24 161 14.91 9.99–22.24 Imicho 89 19 129 14.73 9.39–23.09 Dumo 62 10 88 11.36 6.11–21.12 Boka-Shuta 28 8 43 18.60 9.30–37.20 Alargeta 46 10 66 15.15 8.15–28.16 Buta 68 4 96 4.17 1.56–11.10 Total 408 75 583 12.86 10.26–16.13 Mortality Wodiyo 115 14 161 8.69 5.15–14.68 Imicho 89 11 129 8.53 4.72–15.39 Dumo 62 4 88 4.55 17.06–12.11 Boka-Shuta 28 – 43 – Alargeta 46 3 66 4.55 1.47–14.09 Buta 68 8 96 8.33 4.167–16.66 Total 408 40 583 6.86 5.03–9.35 IR Incidence rate, CI Confidence Interval Additionally, there are methodological differences According to the K-M hazard analysis, the risk of between earlier studies conducted in Ethiopia and other morbidity and mortality in lamb varied concerning the studies when estimating the lamb morbidity or mortality potential risk factors considered. As a result, the lambs rate. It is challenging to link differences in the cumula - with different colostrum feeding methods had the high - tive incidence of morbidity and mortality between the est risk of morbidity (HR = 3.158), followed by variations current study and previous studies to variations in geo- in birth weight (HR = 1.418), umbilical care (HR = 0.473), graphic and management conditions because of method- lamb sex (HR = 0.265), and colostrum intake time ological differences in the calculation of the cumulative (HR = 0.251). Similarly, lambs with difficult lambing incidence. This means that the current study looked at a had the highest risk of mortality (HR = 4.926) com- wide range of potential risk factors for lamb morbidity pared to lambs born normally at all follow-up times, fol- and mortality. As a result, multivariable Cox regression lowed by the first time of colostrum intake (HR = 4.023), analysis revealed that lamb sex, birth weight, Umbilical method of colostrum feeding (HR = 3.206), birth weight care, method, and time of colostrum feeding were risk (HR = 0.379), and dams’ parity (HR = 0.223). Delay in factors for lamb morbidity, while birth weight, lambing consuming colostrum, help with lambing, and other fac- difficulty, dams’ parity, method and time of colostrum tors are all responsible for the higher risk of morbidity feeding were risk factors for lamb mortality. and mortality in the first month. This research showed that the mortality rate was higher in lambs who give birth to three lambs than in twins and single births. This research was supported by pre - vious findings that showed that the kind of birth had a substantial impact on lamb survival, with single births exceeding multiple births (Ortiz 1983; Ricordeau et  al. 1990; Gizaw et  al. 1995). Lambs of recurrent births as a result of physiological starvation of the uterus are often fragile and underweight, and this condition is even more problematic if the female does not produce enough milk (Awgichew 2000). Similarly, the effect of lamb birth weight on lamb mor - tality was consistent with several previous works by Fig. 1 K-M survival curve of all-cause morbidity in lamb based on Gizaw et  al. 2007 and Mukasa-Mugerwa et  al. (Gizaw colostrum intake time Fesseha et al. Animal Diseases (2023) 3:11 Page 6 of 13 to 90% if lambs were born with a birth weight of 2 kg or more. Early-age/parity ewes are not matured, and they require nutrition for ewe growth and lactation require- ments. The lambs’ mammary development is also not complete, which will result in poor mothering capacity and survivability. These results coincided with the find - ings of Mukasa-Mugerwa et al., (Mukasa-Mugerwa et al. 1994), who reported that the survival rates of lambs were higher in the fifth and sixth parities, with a trend toward an increase in survival from the first to the sixth parity, and the general trend for increasing survival rate with increased parity may be due to an increase in dam Fig. 2 K-M survival curve of all-cause mortality in lamb based on weight and, as a result, a large quantity of milk produced Dams’ parity in ewes with increased parity. While the ewe’s milk sup- ply and mothering skills improve with parity, there is a point at which the dam’s conditions and ability to nurture et  al. 2007;  Mukasa-Mugerwa et  al. 1994), who reported the lamb decrease (Mukasa-Mugerwa et al. 1994). On the that the likelihood of survival decreases significantly other hand, Gizaw et  al., 1995 revealed that parity did when a lamb weighs less than 2 kg. Lambs with low birth not have a significant role in lamb survival  (Gizaw et  al. weight cannot survive in harsh climates because of their 1995). low energy storage and reduced ability to regulate body In this study, sex was not a risk factor for morbidity and temperature. Heavier lambs have increased chances of mortality in lambs. The higher mortality in male lambs early survival (Morel et  al. 2008). Mukasa-Mugerwa and than in female lambs in this research was comparable his colleagues, (Mukasa-Mugerwa et  al. 1994) investiga- with the previously reported studies (Vatankhah and tion showed that a neonatal survival rate can increase up Talebi 2009; Ahmed et  al. 2010; Abdelqader et  al. 2017). Table 3 Kaplan-Meier estimate of the hazard of morbidity and mortality in lamb from birth to three months Age interval Number of lamb No. of Censored Hazard Survival Cumulative Std. error 95% CI for Hazard (months) at risk cases number probability incidence Morbidity 0–1 211 44 0 0.1618 0.8503 0.1497 0.0243 0.1141–0.2094 1–2 164 27 0 0.3086 0.6230 0.3770 0.0587 0.1936–0.4236 2–3 25 4 0 0.2051 0.5071 0.4929 0.1020 0.0052–0.4051 Mortality 0–1 197 28 0 0.1029 0.9021 0.0979 0.0194 0.0649–0.1410 1–2 140 9 0 0.1029 0.8138 0.1862 0.0342 0.0357–0.1700 2–3 31 3 0 0.1538 0.6976 0.3024 0.0886 0.0000–0.3274 Table 4 Major causes of morbidity and mortality in the 408-lamb monitored in southwestern Ethiopia Causes Morbidity (N = 75) Mortality (N = 40) No. of cases Percentage (%) No. of cases Percentage (%) Diarrhea 37 49.33 20 50.00 Pneumonia 22 29.33 13 13.25 Mismothering exposure 6 8.00 – – Management problem 2 2.67 4 10.00 Unknown cause 5 6.67 3 7.50 Predator 3 4.00 – – F esseha et al. Animal Diseases (2023) 3:11 Page 7 of 13 Table 5 Univariable analysis of risk factors for lamb morbidity and mortality using Log-rank test No Variable Morbidity Mortality Chisq p Chisq p 1 Address ( Wodiyo/Imicho/Dumo/Boka-Shuta/Alargeta/Buta) 9.21 0.1009 6.16 0.2910 2 Owner age (18–30/31–40/41–50/> 50) 18.75 0.0003 0.86 0.8342 3 Sex (owner, Male/Female) 0.01 0.9152 1.49 0.2229 4 Education status (Illiterate/Read and write/Elementary/Secondary/Above) 17.59 0.0015 7.52 0.1109 5 Flock size (2–4/5–7/> 8) 4.97 0.0835 0.72 0.6989 6 Lamb sex (Male/Female) 0.09 0.7603 2.42 0.1195 7 Birth type (Single/Twice/Triple) 6.69 0.0352 28.50 0.0000 8 Birth weight (kg) (≤2/2–2.5/2.6–3/3.1–3.5/≥3.6) 12.13 0.0164 95.04 0.0000 9 Lambing difficult (Yes/No) 6.14 0.0132 2.65 0.1035 10 Dams’ parity (Primiparous/Multiparous) 3.02 0.0821 18.08 0.0000 11 Season of birth ( Wet/Dry) 3.34 0.0677 0.16 0.6853 12 Hygiene (Poor/Good) 0.09 0.7603 2.42 0.1195 13 Mixing of different weaned lambs (Yes/No) 0.14 0.7035 1.43 0.2320 14 Umbilical care (Yes/No) 0.53 0.4647 0.14 0.7063 15 Method colostrum fed (Suckling/Hand feed/Not feed) 86.25 0.0000 50.87 0.0000 16 Time of colostrum feeding (< 6 hrs vs 6-12 hrs vs > 12 hrs) 26.86 0.0000 7.55 0.0229 17 Causes of morbidity and mortality (Diarrhea/Pneumonia/Mismothering expo- 14.08 0.0151 6.09 0.2971 sure/Management problem/Unknown cause/Predator) Table 6 Risk factors associated with the incidence of all-cause morbidity and mortality in lamb under three months of age in multivariable Cox proportional hazard regression model Risk factor Morbidity Mortality HR p 95% CI for HR HR p 95% CI for HR Lamb sex (Male/Female) 0.265 0.000 0.137–0.510 – a – b b Birth weight (kg) (≤2/2–2.5/2.6–3/3.1–3.5/≥3.6) 1.418 0.003 1.127–1.784 0.379 0.000 0.257–0.557 Lambing difficult (Yes/No) – a – 4.926 0.047 1.024–23.700 Dams’ parity – a – 0.223 0.007 0.075–0.668 Umbilical care (Yes/No) 0.473 0.028 0.243–0.921 – a – b b Method of colostrum feeding (Suckling/Hand feed/Not feeding) 3.158 0.000 2.202–4.528 3.206 0.000 1.900–5.407 b b Time of colostrum feeding (< 6 h/ 6-12 h/12 hrs) 0.251 0.000 0.138–0.457 4.023 0.012 1.361–11.887 NB: a: p > 0.05; b < 0.05 Table 7 Identified lamb disease during FGD in the study area Local name Amharic name English name Signs of the disease Rank (Kafficho) Oshiyoo Yesambamich Pneumonia Coughing, labor breathing 1st Goociyee biiyo Tekimat Diarrhea Watery diarrhea 2nd Michichino Yemiyasimit Dysentery Bloody diarrhea 3rd Kashingito Tilatil Internal parasite Emaciation, eggs on feces 4th Maace shuuiyoo Hod dirket Constipation Dry feces 5th Rank Ranking of lamb diseases based on the frequency of occurrences by animal owners Fesseha et al. Animal Diseases (2023) 3:11 Page 8 of 13 However, Turkuson et  al. (Turkson and Sualisu 2005) in current study, Hadgu 2021 reported that lamb morbidity Ghana reported higher mortality for female lambs. This and mortality were 27.3% and 32.5%, respectively (Hadgu disparity has been attributed to sex-related variables that et al. 2021). In contrast to the current study, malnutrition have yet to be identified according to Mandal et al. (Man - (31.3%) followed by diarrhea (24%) and respiratory prob- dal et al. 2007). lems (21.3%) was the most common cause of lamb mor- The lambing season has an insignificant (p > 0.05) effect tality. Neonatal diarrhea in lambs is considered a cause of on the lamb morbidity and mortality rate in all age inter- lamb death, and Pasteurella spp., Salmonella spp., E. coli, vals and higher lamb mortality was recorded during the and Helminthes are possible causative agents of these dry season (11.54%) than in the wet season (10.69%). In diseases (Smith 1977). line with the current study, previous research found that Diarrhea was the leading sign of death in lambs in lambs born during the rainy season have lower mortality approximately 50% cases. Pneumonia is the second most than lambs born during the dry season (Armbruster et al. important disease responsible for morbidity and mortal- 1991). The lower lamb mortality rate during the rainy ity in lambs. This result is in agreement with the findings season may be owing to better feed supplies along with of Mukasa-Mugerwa, Njau and Gama, who reported that better shelter, whereas the higher death rate during the respiratory infections represented 54% causes of neonatal dry season may be due to increasing disease pressure and lamb mortality, (Mukasa-Mugerwa et al. 2000; Njau et al. feed shortages. 1988; Gama et al. 1991). Moreover, a study carried out by The value of colostrum was recognized by a large Tibbo (Tibbo 2006) indicated that respiratory disease is percentage of respondents (64%) who allowed unre- the single most important cause of sheep mortality in the strained nursing of lambs, while a minor percentage of Central Highlands of Ethiopia. In other studies by Bekele, respondents (36%) restricted suckling. After 6 to 12h (Bekele et  al. 1992a; Bekele et  al. 1992b), the etiologies after delivery, the neonate’s ability to absorb immuno- involved were multifactorial, and 100 % respondents in globulin begins to deteriorate (Radostits et  al. 2007). To the study area were not measured to treat and prevent ensure a successful transfer of passive immunity and the disease due to less attention given to lambs and a lack colostrum immunoglobulins, it is suggested that the of awareness and distance of veterinary service to bring lamb be allowed to properly drink the dam’s colostrum sick lambs in the study area. within the first 2 days after delivery (Singh et  al. 2009). FGD was conducted with key informants, and the par- The mortality rate of lambs was reduced through the use ticipants identified and ranked the following diseases and of separate lambs, care for the lambs, administration of conditions such as infectious disease (1st), mismothering colostrum within 12 h of age, and early supplementation starvation exposure (2nd), predator (3rd), management of the young. Used, but the mortality rate is still higher (4th), and unknown causes (5th) as the causes of lamb than in other studies. However, this is lower than the pre- morbidity and mortality in the study area. According to viously reported prevalence of 40% in the Ebinat woreda Berhan, lambs born during the dry season had a greater National Regional State of Amhara in northwestern Ethi- death rate than lambs born during the rainy season  (Ber- opia (Woldemariam et al. 2014). han and Van Arendonk 2006). Through its effect on feed In this study, keeping neonates and ewes near the availability, the seasonal influence on lamb mortality has home garden away from the rest of the herd for 1 week been well documented. This is because sheep in the tropics had a significant effect on mortality rates in pre-weaning and Ethiopia, in particular, rely mostly on natural grassland lambs (p  > 0.05), and in herds with newborn sheep and grazing and agricultural residue, both of which are sea- ewes, more deaths were found. It was kept with the rest sonal in availability and quality. In Ethiopia, feed is supe- of the herd. This may be due to the high risk of poor care, rior in terms of both quality and quantity during the rainy injury, exposure to predators, and insufficient intake of season, while the opposite is true during the dry season. colostrum. When the newborn lambs are not immuno- The study’s main strength was that it attempted to logically competent, there is a greater risk of contracting analyze the causes of morbidity and mortality in lambs, contagious diseases by running with the flock. This result as well as the factors that contribute to this, whereas its is in agreement with Sharif et al. (Sharif et al. 2005), who main drawback was that it did not determine the bacte- reported that if lambs were not segregated from adult rial causes of lamb mortality and morbidity and solely animals, they were more likely to die. The isolation of dis - based on the survey than laboratory finding support. Fur - eased animals from the flock aids lamb survival by reduc - thermore, because this research was conducted with a ing the danger of infectious disease transmission. smaller sample size, a smaller geographical coverage, and Diarrhea was the most important cause of morbidity over a shorter period, it was difficult to include all poten - (49.33%) and mortality (50.00%) in lambs. In line with the tial risk variables for mortality and morbidity. F esseha et al. Animal Diseases (2023) 3:11 Page 9 of 13 Fig. 3 Map of Gewata district, Arc GIS, 2020 In conclusion, to reduce lamb mortality and morbid- Conclusion ity, an appropriate package should be created and imple- The mortality and morbidity of lambs are the most criti - mented. Husbandry strategies that can reduce the loss cal production issues that severely influence sheep pro - of young stock be made more widely known to livestock ductivity in the study area. The current study found that owners. It is necessary to establish and implement proper lamb morbidity and mortality rates in Gewata woreda veterinarian service and disease detection mechanisms. are high due to a variety of variables that influence lamb As a result, all of these can help to lessen the various risk morbidity and mortality. Factors such as lamb sex, birth factors and their negative impacts. Moreover, further weight, umbilical care, method and time of colostrum extensive examinations of lamb morbidity and mortality feeding were risk factors for lamb morbidity, while birth should be conducted to assess the actual effect of lamb weight, lambing difficulty, dams’ parity, method and time morbidity and mortality on sheep production in the of colostrum feeding were risk factors for lamb mortal- research region. ity at all ages, whereas birth season had did not affect morbidity. Infectious diseases such as diarrhea and pneumonia were the leading cause of lamb mortality fol- Methods lowed by mismothering, predators, management issues, Study area and unknown reasons. Diarrhea, pneumonia, dysentery, This study was conducted in the Gewata district of Kaffa internal parasites, and constipation were found to be the Zone, southern Ethiopia, it is located about 600 km most common lamb diseases in the study area. Diseases, and 869 km from Addis Ababa. From an agroecologi- a lack of animal health specialists, a lack of medications, cal point of view, the Gewata region is 10% lowland and the period between vaccinations were all listed as (< 1,500 m.a.s.l), 55% mid-altitude (1,500–2,300 m.a.s.l), restrictions to sheep production in the study area. Fesseha et al. Animal Diseases (2023) 3:11 Page 10 of 13 and 35% highland (> 2,300 m.a.s.l). The altitude is Where SE is the standard error. between 1400 m and 2,700 m above sea level. Gewata By considering the standard error of 0.05 with a 95% woreda is located between 34°45′ to 36°10′ east longi- coefficient interval, N = 0.25/0.05 = 100. However, 408 tude and 5°40′ to 7°40′ north latitude (Fig.  3). The aver - animal owners participated in the questionary sur- age annual temperature is 13 to 36 degrees Celsius and vey from the six kebeles during the survey to increase the annual rainfall is 900 to 1400 mm. Beekeeping and precision. mixed crop production are the main sources of income The number of participants was selected on a house - for the majority of the population. The main crops grown hold basis from the six study sites. These six sites/kebe - in the region are grains such as wheat, barley, teff, leg - les were selected since they were the main target site of umes, maize, and anise. The main livestock raised in the the project of the Bonga breeding center. Moreover, the region is cattle (105,558), sheep (25,948), goats (21,748), households were chosen based on criteria such as acces- horses (9,629), mules (1,012), donkeys (1,193), chickens sibility, the presence of greater than two lambs, the live- (123,070), and hives (82,969) (GDLFO 2020). stock-crop mixed production system, animal owners’ experience in extension programs, and owners’ willing- Study subjects and animals ness to participate in the study. Smallholder farmers in selected districts were the tar- get populations. They were chosen at random fashion Data collection methods and sources from six kebeles (peasant associations) (PA). The Indig - Data were obtained from primary and secondary data enous breed of sheep also known as the “Bonga” breed/ sources used during the study period. Primary data were type were the study animals. The study involved birth- collected through semi-structured interviews, FGD, farm to-weaning lambs kept under extensive, semi-intensive, observations and  408 purposively selected households. traditional systems of small-scale mixed crop-livestock During the interview, major causes of lamb morbidity production. The age of the lamb was estimated from and mortality were assessed. available birth records and dentition, and eight tem- porary incisors develop during the first month of life. Observational study and clinical examination Health of each lamb was determined through detailed The study involved monitoring lamb morbidity and physical and clinical examination. mortality in selected six sites during the study period. All lambs in the selected flock were strictly monitored starting from birth to weaning age. The regular follow- Study design up and clinical examinations were done by veterinar- A longitudinal prospective survey was employed from ians who were working in the breeding center as well June 2020 to July 2021 on 408 randomly selected farm- as animal health extension workers assigned by the Dis- ers located in six purposively selected kebeles in Gewata trict Agricultural Office. Veterinarians visited the lambs woreda, to determine the cumulative incidence of mor- every month, and the investigators performed emer- bidity and mortality in lambs and to identify potential gency visits in addition to routine visits when there was risk factors. These were intended to collect a one-year a need for a health evaluation of the lambs in response data set (June 2020 to July 2021) of lamb morbidity and to a request from flock owners. Every day, animal health mortality. Traditional survey methodologies, as well as extension workers visited the research animals and participatory epidemiology tools and data collection and recorded their health status using a recording format. interpretation concepts, were used in the study. Lamb During the farm visit, lambs with apparent signs of ail- owners who own animals took part in determining the ment were subject to a detailed clinical examination. A reasons and assessing the effect of lamb morbidity and change in vital signs (rectal temperature, heart rate, res- mortality, as well as other limits on sheep productivity. piratory rate, the color of mucous membranes, palpa- Dates of birth, birth weight, sex, type of birth, and date tion of superficial lymph nodes, skin condition, joints, of death of lambs were gathered from the animals’ data and feet examination, depressed mentation, poor suckle recording book of the community-based Bonga sheep reflex, weakness and recumbency) discovered during the breed improvement cooperatives. examination was documented on a predetermined for- mat. Moreover, lambs’ health was evaluated via objective Sample size determination and sampling methods criteria of appetite, fecal consistency, hydration status, The sample size was determined using Arsham for - and behavior. After these detailed clinical and physical mula (Arsham 2005). examinations, animals were categorized as “apparently 0.25 healthy” or “diseased” (Hadgu et  al. 2021; Mohammed N = SE et al. 2020). F esseha et al. Animal Diseases (2023) 3:11 Page 11 of 13 Questionnaire survey and focus group discussion spreadsheet for later data management and analy- A semi-structured questionnaire was developed to collect sis using STATA 13 statistical software. Morbidity and information on the potential factors associated with the mortality rates were calculated using the true incidence risk of lamb morbidity and mortality in the study area. The rate, which was defined as the number of new cases of questionnaire was pre-tested and administered in person diseased cases/mortality that occurred during the fol- to the farmer if one was available, or to an animal health low-up period divided by the number of lamb months- worker most responsible for animal management. The at-risk (Sullivan 2016). For the morbidity rate, the time at information gathered includes variables at the lamb and risk was measured from the start of the study until the flock levels, as well as other farm management practices. lamb developed a clinical sign of any illness. Further- Focus group discussion (FGD) was conducted using a more, a lamb that had one illness was considered to be purposive sampling technique with farmers having indig- at risk for another. The mortality risk time was calculated enous knowledge of animal disease experience to acquire from the time a lamb is enrolled in the study (soon after relevant information. A total of 54 participants were birth) until death from any cause occurs. A lamb with selected (each focus group with six participants with a a disease condition was also considered to be at risk of total of nine FGDs from six kebeles). Interviews with death. Lamb who dropped out (lost to follow-up) from key informants (Site animal health assistance and animal the study before the end of the observation period or who production experts) were used purposively. Addition- remained event-free (morbidity or mortality) at the end ally, the diseases that affect lambs in the area, as well as of the observation period were censored, which is known their local names, seasons of occurrence, and traditional as right censoring. treatments for lamb ailments, are all discussed during Time-to-event data were analyzed using non-par- the FGD. Finally, FDG were used to rate illness severity ametric and semi-parametric methods. The Kaplan- and age groups in distinct lamb diseases with recognized Meier (K-M) lifetable analysis, a popular non-parametric local names. Secondary data were also gathered from the approach, was used to compute and describe in tabular district livestock and fishery office and extensively pub - form the cumulative survival probability and cumulative lished data at the study site (Supplementary file). incidence of lamb morbidity and mortality from birth to three months of age. Furthermore, the K-M curves were used to plot cumulative survival data based on age Description of the variables groups and exposure factors studied. The survival prob - Outcome variable: The morbidity or mortality of lambs ability was calculated using the K-M approach and the from birth to three months is the outcome (dependent formula in Eq. (1) or response) variable for this study. Because the variables are dichotomous (yes or no), they were labeled with a 1 if (1) the event of interest occurred, and a 0 if it did not occur where St is survival probability past interval t; Nt is the during the study’s observation period. number at-risk during interval t; and Dt is the number Independent variables: The current study consid- of disease events or deaths during interval t. The cumu - ers sex, lambing season, weaning age, flock size, birth lative incidence, or cumulative failure probability, was weight lambing difficulty, dam’s parity number, umbili- easily calculated as 1-St using the K-M approach. Censor- cal care (yes/no), a mix of the lamb of different ages, ing was assumed to be independent of the likelihood of time lamb ingested their first colostrum meal, method developing the outcome event, and survival probabilities of colostrum feeding, hygiene, and farmers’ educa- were assumed to be comparable in participants recruited tional status as potential independent variables or pre- early and late in the study (non-informative censoring). dictors of lamb morbidity and mortality. The month The log-rank test was used to statistically test the hypoth - in which the study lamb was born is referred to as the esis that there is no difference in the survival curves lambing season. Thus, months with short to heavy rain between the groups of categorical predictors studied and (April–August) are labeled “wet season,” while months to determine whether the predictor should be included in with no rain (September–March) are labeled “dry the final model. To select a variable for the multivariable season.” model, a P value cut off at 0.25 from the log-rank test was used as a criterion. A multivariable Cox proportional hazards regres- Data analysis sion model, a semiparametric approach, was used to Data from questionnaire interviews and focus group analyze risk factors associated with lamb morbidity discussions were entered and stored in an MS Excel Fesseha et al. Animal Diseases (2023) 3:11 Page 12 of 13 Availability of data and materials and mortality. The utilized Cox proportional hazards The data will be provided upon the request of the corresponding author. regression model is denoted by Eq. (2) Declarations (2) Ethics approval and consent to participate where h(t) is the expected hazard at time t, h0(t) is the The Institutional Review Board of Wolaita Sodo University (IRB) has approved the ethical approval of the current study. The purpose of the study was com- baseline hazard, X1, X2, Xp are the predictors (or inde- municated to the participants and informed consent was obtained using oral pendent variables), and β1 þ β2 þ…. βp are the coeffi - informed consent approved by the institutional ethics committee. Throughout cients for each independent variable. The baseline hazard the investigation, identifiers such as personally identifiable information have been excluded and kept confidential. Photos and videos of study participants is the risk that exists when each independent variable is were kept anonymous. Participation in the study was completely optional. equal to zero. The Cox model analyzes the time to event Those who do not want to participate or wish to end their participation have about multiple factors at the same time and provides esti- been given the freedom to do so. mates of the strength of the effect (hazard ratio, HR) for Consent for publication each constituent factor. The final model was constructed Not applicable. by stepwise backward elimination of variables that were Competing interests not significant at the 5% level. Potential confounders All authors declare no competing conflicts of interest. were controlled at every stage of model construction. A variable was considered a confounder if the coefficients Author details School of Veterinary Medicine, Wolaita Sodo University, Wolaita Sodo, Ethio- of the remaining variables changed by 20%, and these pia. Gewata District Animal Health Expert, Kaffa Zone, Bonga, Ethiopia. were kept in the model even if they were not significant. The Cox proportional hazard model assumed that the Received: 22 November 2022 Accepted: 5 March 2023 hazards are proportional, which means that the relative hazard remains constant over time with different predic - tors or covariate levels (49). We used the Schoenfeld and References scaled Schoenfeld residuals to test the proportionality Abdelqader, A., R. Irshaid, M.J. 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Study on incidence of lamb morbidity and mortality and associated risk factors in the mixed crop-livestock production system of Gewata District, Kaffa zone, southwestern Ethiopia

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Abstract

Lamb morbidity and mortality cause significant loss in a smallholder production system. A longitudinal prospective survey was conducted on 408 randomly selected farmers located in six purposefully selected kebeles in Gewata woreda from June 2020 to July 2021 to determine the incidence of morbidity and mortality in lambs and to identify risk factors. For this purpose, 408 lambs from the Gewata district’s mixed crop-livestock production system were examined every day from birth to three months of age. The data was analyzed using the Kaplan-Meier (K-M) method, the log-rank test, and Cox proportional hazards regression. Results showed that the cumulative incidence of all- cause of morbidity and mortality at the end of three month was 12.86% (95% CI: 10.26–16.13%), and 6.86% (95% CI: 5.03–9.35%), respectively. Diarrhea was the leading cause of morbidity and mortality, accounting for 49.33 and 50% morbidity and mortality, respectively. Pneumonia was the second most frequent cause of morbidity and death. In the K-M hazard analysis, the greatest risk of lamb morbidity and mortality was observed during the first month of life, and then the risk decreased significantly as the lamb grew. Of the 17 potential risk factors studied, the multivariable Cox proportional hazards regression model showed that lamb sex, birth weight, umbilical care, time and method of colos- trum feeding were the five predictors that were significantly associated with a higher risk of morbidity, whereas birth weight, lambing difficulty, dams’ parity, method and time of colostrum feeding were the five predictors that were significantly associated with a higher risk of mortality. Moreover, a higher risk of morbidity was observed in lambs with methods of colostrum feeding after birth (HR = 3.158; p = 0.000) and with variations in birth weight (HR = 1.418; p = 0.003). Similarly, the mortality risk was 4.926 (p = 0.047), 4.023 (p = 0.012), and 3.206 (p = 0.000) times higher in lambs with lambing difficulties, at the time of colostrum feeding, and by the method of colostrum feeding, respec- tively. According to this research, lamb morbidity and mortality rates in the study area are significantly high which has a great impact on the replacement stock and production. Hence, awareness should be created among farmers concerning improved lamb management practices. Keywords Gewata, Incidence, Lamb, Morbidity, Mortality, Ethiopia *Correspondence: Haben Fesseha haben.senbetu@wsu.edu.et Full list of author information is available at the end of the article © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. The Creative Commons Public Domain Dedication waiver (http:// creat iveco mmons. org/ publi cdoma in/ zero/1. 0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Fesseha et al. Animal Diseases (2023) 3:11 Page 2 of 13 Khan et  al. 2006). To completely appreciate the causes of Introduction lamb morbidity and mortality, it is also necessary to com- Ethiopia has approximately 30.7 million heads of sheep prehend the associated risk factors (Fentie et  al. 2016; and is Africa’s second-largest sheep population (Central Hadgu et  al. 2021; Mohammed et  al. 2020; Hordofa et  al. Statistical Agency 2019). Sheep breeds are widely spread 2021). Genetic, environmental and management factors across the country’s diverse ecosystem, ranging from were the most important determinants of lamb mortality subalpine to dry lowlands, as well as production practices and morbidity. These include lamb’s birth weight, sex, dam (Gizaw et al. 2007; Tibbo 2006). Short-tailed, long-tailed, parity and age, colostrum immunoglobulin transfer, lamb- thin-tailed, and fat-tailed sheep are among the 14 tradi- ing season and year, dam body weight during lambing, and tional sheep populations of the country and are divided litter size (Hadgu et  al. 2021; Fogarty et  al. 2000; Dalton into four major groups based on tail type (Galall 1983). et al. 1980; Sawyer et al. 1977; Wiener et al. 1983). Additionally, using a microsatellite DNA marker, Ethio- The Kaffa zone has a large potential for a small rumi - pian researchers found nine breeds and six genetically nant population kept by smallholder farmers as a sole diverse sheep breed groupings that are scattered across or supplementary source of cash income (Ortiz 1983). the nation in various agroecology and production meth- Although small ruminant production provides food secu- ods (Gizaw et al. 2007; Solomon et al. 2008). rity for sheep producers, disease, poor nutrition, poor In Ethiopia, mixed crop-livestock production accounts animal production systems, reproductive inefficiency, for 75% sheep population, while pastoral and agro-pasto- management constraints, inadequate veterinary care, ral farming accounts for the remaining 25%. They oper - and lamb mortality have a great impact on smallholder ate on a large production system with minimal effort and producers. Lamb morbidity and mortality are one of the produce the lowest carcass weight compared to other most evident constraints to sheep producers’ profitability East African countries (Solomon et  al. 2008). Due to in most countries, resulting in a shortage of replacement ecological, economic and cultural variations, the aim of stock. The rate of survival of lamb produced determines maintaining sheep varies from place to place. They are, the success of any breeding program, as well as the future however, by and large, save for exceptional makes use of of sheep production. For farmers and cattle herders to together with earnings generation, meat, milk, skin, wool, get the most out of their livestock resources, it’s critical manure, security, gifts and non-secular rites (Edea et  al. to develop efficient livestock production that can pre - 2010). vent losses of young stock. Hence, the major cause of One of the major production challenges affecting sheep lamb stock morbidity and mortality should be identified and goat productivity is the high pre-weaning mortal- and estimated to develop a sustainable control program. ity of young lambs and kids (Singh et al. 2009). The term Keeping these aspects in view, the current study was con- “preweaning mortality rate” (PWMR) refers to the num- ducted to assess the incidence of morbidity and mortality ber of lambs that die between birth and weaning, includ- from birth to weaning and potential risk factors in lambs ing neonatal mortality (International livestock center for of the Gewata district, Kaffa zone, southwestern Ethiopia. Africa 1998), especially in the neonatal stage (from birth through the first 28d of life), which is the most essential for lambs (Gokce et  al. 2014). The study on Ethiopian Results highlands revealed that a high level of neonatal lamb Descriptive epidemiology mortalities was recorded both on-station (46.3%) and on- In this study, 408 farmers in a mixed crop-livestock pro- farm (51.5%) (Bekele et  al. 1992a), whereas the study of duction system with at least one lamb less than 3 months Rift Valley areas of Ethiopia showed that 46.8% prewean- of age in their flock were interviewed from six kebeles of ing kids death and 30.3% neonatal kid death, especially Gewata district, Kaffa Zone, Southwest Ethiopia. Of the till 1 month of age (Fentie et al. 2016). 408 respondents, 81.86% were men, while 18.14% were In Ethiopia and other parts of the world, lamb mortal- women. The age categories of the respondents in the ity can only be reduced by recognizing and addressing 18–30 years, 31–40 years, and 41–50 years age groups the underlying causes (Kirk and Anderson 1982), such as were 46.32, 33.58, and 15.20%, respectively. The remain - infectious conditions (pneumonia, liver fluke, diarrhea and ing age groups were above, and regarding this age dis- pneumo-enteritis) and non-infectious conditions (starva- tribution of the respondents, the majority were grouped tion/chilling exposure complex, stillbirths/dystocia, mis- by productive age. The level of education is the most mothering, low birth weight, breed, ewe’s age, neonate’s basic criterion for determining a society’s standing. A immunity gained through colostrum, dam’s parity and literate community is more capable of comprehending lamb’s sex, injury and poisoning) (Fentie et al. 2020; Hadgu and completing various agricultural activities. The find - et  al. 2021; Islam et  al. 2015; Lorenz et  al. 2011; Moham- ings revealed that 17.16 and 27.94% respondents were med et  al. 2020; Binns et  al. 2002; Hordofa et  al. 2021; F esseha et al. Animal Diseases (2023) 3:11 Page 3 of 13 illiterate and read and write, respectively. Others, 28.18 during the second and third months of life, and then and 12.75% had completed elementary and secondary the risk decreased significantly as the lamb grew older education levels, respectively, and the remaining 4.17% (Table 3). were above secondary (Table 1). Of the total sampled lamb, 54.17% were male and Causes of morbidity and mortality 45.83% were females. A significantly high number of Diarrhea was the leading cause of morbidity and mor- owners care for umbilical (66.91%) and fed colostrum tality accounting for 49.33 and 50.00% morbidity and by suckling (56.13%) within 6h (51.72%). Regarding mortality, respectively. Pneumonia was the second most the birth type, the highest number (57.87%) were born frequent cause of morbidity and death. Table  4 lists the twice, and the least number was born triple (2.94%). other prevalent causes of lamb morbidity and mortality. Moreover, 60.78% lambs were born with lambing dif- ficulty, 85.54% dams’ parity was multiparous, and the Risk factors for lamb morbidity and mortality highest number of lambs was weighted between 3.1– Univariable analysis 3.5 kg (34.80%). In this study, 78.68% were sampled In this study, the effect of six kebeles host and man - in the wet season, 54.17% were managed under poor agement factors on lamb morbidity and mortality was hygiene, and 72.55% was mixed with other weaned lamb assessed using the Log-rank test, and potential predictors in the flock (Table 1 ). for the final multivariable analysis were selected based on the results. From there, the variables with p-values less than 0.25 were selected for the multivariable analysis of Lamb morbidity and mortality rate the risk factors, totaling 12 variables for morbidity and 11 Of the 408 lambs that were observed in this study, disease variables for mortality (Table 5). incidences and deaths in the study lamb were recorded up to three months of age, after which no morbidity or Multivariable analysis mortality events were noted. As a result, the data were truncated after three months and accordingly the over- Lamb morbidity rate The incidence rate of lamb mor - all morbidity and mortality rates are calculated as 12.86 bidity was found to be significantly (p  < 0.05) impacted cases per 100 lamb months and 6.86 cases per 100 lamb by lamb sex, birth weight, Umbilical care, method and months at risk, respectively. The highest morbidity and time of colostrum feeding in the final multivariable Cox mortality (18.60 and 8.69) were observed in Bako-Shuta regression analysis model. Accordingly, compared to and Wodiyo, respectively. Similarly, the lowest morbid- their counterparts, lamb sex (HR = 0.265), and umbili- ity and mortality (4.17 and 0) were observed in Buta, and cal care (HR = 0.473) had a lower risk of morbidity. In Bako-Shuta, respectively. Besides, morbidity and mortal- contrast, the method of colostrum feeding had the high- ity of lamb based on origin or kebele were presented in est risk of morbidity (HR = 3.158) (Table  6). The final Table 2. model was tested for the proportional hazards assump- tion and found not to violate the assumption (global test: Kaplan‑Meier survival analysis Chisq = 10.77; df = 16; p = 0.8235). The cumulative survival probability of lamb to all-cause morbidity by colostrum intake time and mortality by Lamb mortality rate The final multivariable Cox haz - dams’ parity is showed in Figs.  1 and 2, respectively. ard regression analysis model revealed that among the To better visualize the cumulative survival probabil- assessed potential risk factors,  such as birth weight, ity or incidence of morbidity or mortality from birth to lambing difficulty, dams’ parity, method, and time of three months of life, the same data were also presented colostrum feeding all had a statistically significant using the K-M life table (Table  3). The K-M survival (p < 0.05) impact on the lamb mortality rate. In compari- curves show a significant decrease at end of each month son to their counterparts, the mortality risk was lower with a constant across respective months in the survival in the birth weight of lamb (HR = 0.379), and dams’ par- probability of lamb with increasing age. Disease events ity (HR = 0.223). On the other hand, lamb from a ewe were recorded in all age groups. with lambing difficulty exhibited a higher mortality risk Using the Kaplan-Meier method, we calculated the risk (HR = 4.926) (Table 6). The final model was tested for the of morbidity and mortality at the end of each month until proportional hazards assumption and found not to vio- the lambs were three months old. As a result, the great- late the assumption (global test: Chisq = 7.37; df = 16; est risk (hazard) of morbidity and mortality was observed p = 0.9656). Fesseha et al. Animal Diseases (2023) 3:11 Page 4 of 13 Participatory investigation of causes of lamb morbidity Table 1 Respondents’ feedback on their demography, lambs’ health, and management in the mixed crop-livestock production and mortality in the study area system of Southwest Ethiopia During the focus group, key informants’ discussion was local names, in order of importance, experience with Variable Category Frequency Valid percent (%) lamb health problems and methods of prevention and control, key health issues for each level, and diseases or Origin/Kebele Wodiyo 115 28.19 conditions that cause illness and death in lambs. Identify- Imicho 89 21.81 ing and ranking area sheep production limits, ranking or Dumo 62 15.20 prioritizing morbidity and mortality causes, and discuss- Boka-Shuta 28 6.86 ing sheep morbidity and mortality time trends (seasonal Alargeta 46 11.27 calendar). In terms of lamb health concerns, the research Buta 68 16.67 area’s preventative and control methods were not thor- Owner age (years) 18–30 189 46.32 oughly tested. The participants stated that during lamb 31–40 137 33.58 diseases, they did not pay attention to sick lambs due to 41–50 62 15.20 > 50 20 4.90 a lack of knowledge and the distance to an animal health Sex (owner) Male 334 81.86 facility where the sick lamb might be treated. Female 74 18.14 As discussed during focus group discussion (FGD) and Education status Illiterate 70 17.16 key informants, major health problems in the study area Read and write 114 27.94 were infectious diseases and insufficient facilities for vet - Elementary 155 28.18 erinary services were major animal health problems in Secondary 52 12.75 the area. Diseases or diseases causing factors and death Above 17 4.17 in lambs were identified and ranked in the study area. Flock size 2–4 136 33.33 Importance and local name: Diarrhea (#1), Pneumonia 5–7 145 35.54 (#2), Dysentery (#3), endoparasites (#4), and conception. > 8 127 31.13 (#5) (Table  7). Diseases, shortage of animal health pro- Lamb sex Male 221 54.17 fessionals, shortage of drugs, and vaccination time were Female 187 45.83 enumerated as constraints of sheep production in the Birth type Single 160 39.22 study area. Twice 236 57.84 According to FGD and key informants, infectious dis- Triple 12 2.94 ease (1st), mismothering starvation exposure (2nd), Birth weight (kg) ≤2 28 6.86 predator (3rd), management (4th), and unknown causes 2–2.5 39 9.56 (5th) were identified and ranked as the causes of lamb 2.6–3 97 23.77 morbidity and mortality in the study area. The wet season 3.1–3.5 142 34.80 and dry season were responsible for lamb morbidity and ≥3.6 102 25.00 mortality in the research region, according to temporal Lambing difficult Yes 160 39.22 patterns (seasonal calendar). The causes of lamb mor - No 248 60.78 bidity and mortality in the study area were discussed by Dams’ parity Primiparous 59 14.46 Multiparous 349 85.54 focus group discussants and key informants during the Season of birth Wet 321 78.68 dry season because of a lack of available feeds for ewes Dry 87 21.32 to produce enough milk for lambs. In the wet season, the Hygiene Poor 221 54.17 pasture was contaminated by floods and the season was Good 187 45.83 favorable for microorganism multiplication (Table 7). Mixing of different Yes 296 72.55 weaned lamb No 112 27.45 Discussion Umbilical care Yes 273 66.91 The mortality and morbidity of lambs before weaning are No 135 33.09 major factors in reducing profitability by causing signifi - Method colostrum feed Suckling 229 56.13 cant losses in sheep production, which negatively affects Hand feed 98 24.02 sheep and livestock production (Hadgu et  al. 2021). In Not feed 81 19.85 the current study, the cumulative incidence of all-cause of Time of colostrum feeding ≤ 6 hrs 211 51.72 morbidity and mortality observed was 12.86 and 6.86%, 6-12 hrs 164 40.20 respectively. This finding is the first incidence report on ≥12 hrs 33 8.09 lamb morbidity and mortality in the study area. F esseha et al. Animal Diseases (2023) 3:11 Page 5 of 13 Table 2 Morbidity and mortality rate of lamb in the mixed crop-livestock production system of Southwest Ethiopia based on origin Origin No. of  lamb at risk No. of cases Time at risk (months) IR /100 lamb month 95% CI for IR Morbidity Wodiyo 115 24 161 14.91 9.99–22.24 Imicho 89 19 129 14.73 9.39–23.09 Dumo 62 10 88 11.36 6.11–21.12 Boka-Shuta 28 8 43 18.60 9.30–37.20 Alargeta 46 10 66 15.15 8.15–28.16 Buta 68 4 96 4.17 1.56–11.10 Total 408 75 583 12.86 10.26–16.13 Mortality Wodiyo 115 14 161 8.69 5.15–14.68 Imicho 89 11 129 8.53 4.72–15.39 Dumo 62 4 88 4.55 17.06–12.11 Boka-Shuta 28 – 43 – Alargeta 46 3 66 4.55 1.47–14.09 Buta 68 8 96 8.33 4.167–16.66 Total 408 40 583 6.86 5.03–9.35 IR Incidence rate, CI Confidence Interval Additionally, there are methodological differences According to the K-M hazard analysis, the risk of between earlier studies conducted in Ethiopia and other morbidity and mortality in lamb varied concerning the studies when estimating the lamb morbidity or mortality potential risk factors considered. As a result, the lambs rate. It is challenging to link differences in the cumula - with different colostrum feeding methods had the high - tive incidence of morbidity and mortality between the est risk of morbidity (HR = 3.158), followed by variations current study and previous studies to variations in geo- in birth weight (HR = 1.418), umbilical care (HR = 0.473), graphic and management conditions because of method- lamb sex (HR = 0.265), and colostrum intake time ological differences in the calculation of the cumulative (HR = 0.251). Similarly, lambs with difficult lambing incidence. This means that the current study looked at a had the highest risk of mortality (HR = 4.926) com- wide range of potential risk factors for lamb morbidity pared to lambs born normally at all follow-up times, fol- and mortality. As a result, multivariable Cox regression lowed by the first time of colostrum intake (HR = 4.023), analysis revealed that lamb sex, birth weight, Umbilical method of colostrum feeding (HR = 3.206), birth weight care, method, and time of colostrum feeding were risk (HR = 0.379), and dams’ parity (HR = 0.223). Delay in factors for lamb morbidity, while birth weight, lambing consuming colostrum, help with lambing, and other fac- difficulty, dams’ parity, method and time of colostrum tors are all responsible for the higher risk of morbidity feeding were risk factors for lamb mortality. and mortality in the first month. This research showed that the mortality rate was higher in lambs who give birth to three lambs than in twins and single births. This research was supported by pre - vious findings that showed that the kind of birth had a substantial impact on lamb survival, with single births exceeding multiple births (Ortiz 1983; Ricordeau et  al. 1990; Gizaw et  al. 1995). Lambs of recurrent births as a result of physiological starvation of the uterus are often fragile and underweight, and this condition is even more problematic if the female does not produce enough milk (Awgichew 2000). Similarly, the effect of lamb birth weight on lamb mor - tality was consistent with several previous works by Fig. 1 K-M survival curve of all-cause morbidity in lamb based on Gizaw et  al. 2007 and Mukasa-Mugerwa et  al. (Gizaw colostrum intake time Fesseha et al. Animal Diseases (2023) 3:11 Page 6 of 13 to 90% if lambs were born with a birth weight of 2 kg or more. Early-age/parity ewes are not matured, and they require nutrition for ewe growth and lactation require- ments. The lambs’ mammary development is also not complete, which will result in poor mothering capacity and survivability. These results coincided with the find - ings of Mukasa-Mugerwa et al., (Mukasa-Mugerwa et al. 1994), who reported that the survival rates of lambs were higher in the fifth and sixth parities, with a trend toward an increase in survival from the first to the sixth parity, and the general trend for increasing survival rate with increased parity may be due to an increase in dam Fig. 2 K-M survival curve of all-cause mortality in lamb based on weight and, as a result, a large quantity of milk produced Dams’ parity in ewes with increased parity. While the ewe’s milk sup- ply and mothering skills improve with parity, there is a point at which the dam’s conditions and ability to nurture et  al. 2007;  Mukasa-Mugerwa et  al. 1994), who reported the lamb decrease (Mukasa-Mugerwa et al. 1994). On the that the likelihood of survival decreases significantly other hand, Gizaw et  al., 1995 revealed that parity did when a lamb weighs less than 2 kg. Lambs with low birth not have a significant role in lamb survival  (Gizaw et  al. weight cannot survive in harsh climates because of their 1995). low energy storage and reduced ability to regulate body In this study, sex was not a risk factor for morbidity and temperature. Heavier lambs have increased chances of mortality in lambs. The higher mortality in male lambs early survival (Morel et  al. 2008). Mukasa-Mugerwa and than in female lambs in this research was comparable his colleagues, (Mukasa-Mugerwa et  al. 1994) investiga- with the previously reported studies (Vatankhah and tion showed that a neonatal survival rate can increase up Talebi 2009; Ahmed et  al. 2010; Abdelqader et  al. 2017). Table 3 Kaplan-Meier estimate of the hazard of morbidity and mortality in lamb from birth to three months Age interval Number of lamb No. of Censored Hazard Survival Cumulative Std. error 95% CI for Hazard (months) at risk cases number probability incidence Morbidity 0–1 211 44 0 0.1618 0.8503 0.1497 0.0243 0.1141–0.2094 1–2 164 27 0 0.3086 0.6230 0.3770 0.0587 0.1936–0.4236 2–3 25 4 0 0.2051 0.5071 0.4929 0.1020 0.0052–0.4051 Mortality 0–1 197 28 0 0.1029 0.9021 0.0979 0.0194 0.0649–0.1410 1–2 140 9 0 0.1029 0.8138 0.1862 0.0342 0.0357–0.1700 2–3 31 3 0 0.1538 0.6976 0.3024 0.0886 0.0000–0.3274 Table 4 Major causes of morbidity and mortality in the 408-lamb monitored in southwestern Ethiopia Causes Morbidity (N = 75) Mortality (N = 40) No. of cases Percentage (%) No. of cases Percentage (%) Diarrhea 37 49.33 20 50.00 Pneumonia 22 29.33 13 13.25 Mismothering exposure 6 8.00 – – Management problem 2 2.67 4 10.00 Unknown cause 5 6.67 3 7.50 Predator 3 4.00 – – F esseha et al. Animal Diseases (2023) 3:11 Page 7 of 13 Table 5 Univariable analysis of risk factors for lamb morbidity and mortality using Log-rank test No Variable Morbidity Mortality Chisq p Chisq p 1 Address ( Wodiyo/Imicho/Dumo/Boka-Shuta/Alargeta/Buta) 9.21 0.1009 6.16 0.2910 2 Owner age (18–30/31–40/41–50/> 50) 18.75 0.0003 0.86 0.8342 3 Sex (owner, Male/Female) 0.01 0.9152 1.49 0.2229 4 Education status (Illiterate/Read and write/Elementary/Secondary/Above) 17.59 0.0015 7.52 0.1109 5 Flock size (2–4/5–7/> 8) 4.97 0.0835 0.72 0.6989 6 Lamb sex (Male/Female) 0.09 0.7603 2.42 0.1195 7 Birth type (Single/Twice/Triple) 6.69 0.0352 28.50 0.0000 8 Birth weight (kg) (≤2/2–2.5/2.6–3/3.1–3.5/≥3.6) 12.13 0.0164 95.04 0.0000 9 Lambing difficult (Yes/No) 6.14 0.0132 2.65 0.1035 10 Dams’ parity (Primiparous/Multiparous) 3.02 0.0821 18.08 0.0000 11 Season of birth ( Wet/Dry) 3.34 0.0677 0.16 0.6853 12 Hygiene (Poor/Good) 0.09 0.7603 2.42 0.1195 13 Mixing of different weaned lambs (Yes/No) 0.14 0.7035 1.43 0.2320 14 Umbilical care (Yes/No) 0.53 0.4647 0.14 0.7063 15 Method colostrum fed (Suckling/Hand feed/Not feed) 86.25 0.0000 50.87 0.0000 16 Time of colostrum feeding (< 6 hrs vs 6-12 hrs vs > 12 hrs) 26.86 0.0000 7.55 0.0229 17 Causes of morbidity and mortality (Diarrhea/Pneumonia/Mismothering expo- 14.08 0.0151 6.09 0.2971 sure/Management problem/Unknown cause/Predator) Table 6 Risk factors associated with the incidence of all-cause morbidity and mortality in lamb under three months of age in multivariable Cox proportional hazard regression model Risk factor Morbidity Mortality HR p 95% CI for HR HR p 95% CI for HR Lamb sex (Male/Female) 0.265 0.000 0.137–0.510 – a – b b Birth weight (kg) (≤2/2–2.5/2.6–3/3.1–3.5/≥3.6) 1.418 0.003 1.127–1.784 0.379 0.000 0.257–0.557 Lambing difficult (Yes/No) – a – 4.926 0.047 1.024–23.700 Dams’ parity – a – 0.223 0.007 0.075–0.668 Umbilical care (Yes/No) 0.473 0.028 0.243–0.921 – a – b b Method of colostrum feeding (Suckling/Hand feed/Not feeding) 3.158 0.000 2.202–4.528 3.206 0.000 1.900–5.407 b b Time of colostrum feeding (< 6 h/ 6-12 h/12 hrs) 0.251 0.000 0.138–0.457 4.023 0.012 1.361–11.887 NB: a: p > 0.05; b < 0.05 Table 7 Identified lamb disease during FGD in the study area Local name Amharic name English name Signs of the disease Rank (Kafficho) Oshiyoo Yesambamich Pneumonia Coughing, labor breathing 1st Goociyee biiyo Tekimat Diarrhea Watery diarrhea 2nd Michichino Yemiyasimit Dysentery Bloody diarrhea 3rd Kashingito Tilatil Internal parasite Emaciation, eggs on feces 4th Maace shuuiyoo Hod dirket Constipation Dry feces 5th Rank Ranking of lamb diseases based on the frequency of occurrences by animal owners Fesseha et al. Animal Diseases (2023) 3:11 Page 8 of 13 However, Turkuson et  al. (Turkson and Sualisu 2005) in current study, Hadgu 2021 reported that lamb morbidity Ghana reported higher mortality for female lambs. This and mortality were 27.3% and 32.5%, respectively (Hadgu disparity has been attributed to sex-related variables that et al. 2021). In contrast to the current study, malnutrition have yet to be identified according to Mandal et al. (Man - (31.3%) followed by diarrhea (24%) and respiratory prob- dal et al. 2007). lems (21.3%) was the most common cause of lamb mor- The lambing season has an insignificant (p > 0.05) effect tality. Neonatal diarrhea in lambs is considered a cause of on the lamb morbidity and mortality rate in all age inter- lamb death, and Pasteurella spp., Salmonella spp., E. coli, vals and higher lamb mortality was recorded during the and Helminthes are possible causative agents of these dry season (11.54%) than in the wet season (10.69%). In diseases (Smith 1977). line with the current study, previous research found that Diarrhea was the leading sign of death in lambs in lambs born during the rainy season have lower mortality approximately 50% cases. Pneumonia is the second most than lambs born during the dry season (Armbruster et al. important disease responsible for morbidity and mortal- 1991). The lower lamb mortality rate during the rainy ity in lambs. This result is in agreement with the findings season may be owing to better feed supplies along with of Mukasa-Mugerwa, Njau and Gama, who reported that better shelter, whereas the higher death rate during the respiratory infections represented 54% causes of neonatal dry season may be due to increasing disease pressure and lamb mortality, (Mukasa-Mugerwa et al. 2000; Njau et al. feed shortages. 1988; Gama et al. 1991). Moreover, a study carried out by The value of colostrum was recognized by a large Tibbo (Tibbo 2006) indicated that respiratory disease is percentage of respondents (64%) who allowed unre- the single most important cause of sheep mortality in the strained nursing of lambs, while a minor percentage of Central Highlands of Ethiopia. In other studies by Bekele, respondents (36%) restricted suckling. After 6 to 12h (Bekele et  al. 1992a; Bekele et  al. 1992b), the etiologies after delivery, the neonate’s ability to absorb immuno- involved were multifactorial, and 100 % respondents in globulin begins to deteriorate (Radostits et  al. 2007). To the study area were not measured to treat and prevent ensure a successful transfer of passive immunity and the disease due to less attention given to lambs and a lack colostrum immunoglobulins, it is suggested that the of awareness and distance of veterinary service to bring lamb be allowed to properly drink the dam’s colostrum sick lambs in the study area. within the first 2 days after delivery (Singh et  al. 2009). FGD was conducted with key informants, and the par- The mortality rate of lambs was reduced through the use ticipants identified and ranked the following diseases and of separate lambs, care for the lambs, administration of conditions such as infectious disease (1st), mismothering colostrum within 12 h of age, and early supplementation starvation exposure (2nd), predator (3rd), management of the young. Used, but the mortality rate is still higher (4th), and unknown causes (5th) as the causes of lamb than in other studies. However, this is lower than the pre- morbidity and mortality in the study area. According to viously reported prevalence of 40% in the Ebinat woreda Berhan, lambs born during the dry season had a greater National Regional State of Amhara in northwestern Ethi- death rate than lambs born during the rainy season  (Ber- opia (Woldemariam et al. 2014). han and Van Arendonk 2006). Through its effect on feed In this study, keeping neonates and ewes near the availability, the seasonal influence on lamb mortality has home garden away from the rest of the herd for 1 week been well documented. This is because sheep in the tropics had a significant effect on mortality rates in pre-weaning and Ethiopia, in particular, rely mostly on natural grassland lambs (p  > 0.05), and in herds with newborn sheep and grazing and agricultural residue, both of which are sea- ewes, more deaths were found. It was kept with the rest sonal in availability and quality. In Ethiopia, feed is supe- of the herd. This may be due to the high risk of poor care, rior in terms of both quality and quantity during the rainy injury, exposure to predators, and insufficient intake of season, while the opposite is true during the dry season. colostrum. When the newborn lambs are not immuno- The study’s main strength was that it attempted to logically competent, there is a greater risk of contracting analyze the causes of morbidity and mortality in lambs, contagious diseases by running with the flock. This result as well as the factors that contribute to this, whereas its is in agreement with Sharif et al. (Sharif et al. 2005), who main drawback was that it did not determine the bacte- reported that if lambs were not segregated from adult rial causes of lamb mortality and morbidity and solely animals, they were more likely to die. The isolation of dis - based on the survey than laboratory finding support. Fur - eased animals from the flock aids lamb survival by reduc - thermore, because this research was conducted with a ing the danger of infectious disease transmission. smaller sample size, a smaller geographical coverage, and Diarrhea was the most important cause of morbidity over a shorter period, it was difficult to include all poten - (49.33%) and mortality (50.00%) in lambs. In line with the tial risk variables for mortality and morbidity. F esseha et al. Animal Diseases (2023) 3:11 Page 9 of 13 Fig. 3 Map of Gewata district, Arc GIS, 2020 In conclusion, to reduce lamb mortality and morbid- Conclusion ity, an appropriate package should be created and imple- The mortality and morbidity of lambs are the most criti - mented. Husbandry strategies that can reduce the loss cal production issues that severely influence sheep pro - of young stock be made more widely known to livestock ductivity in the study area. The current study found that owners. It is necessary to establish and implement proper lamb morbidity and mortality rates in Gewata woreda veterinarian service and disease detection mechanisms. are high due to a variety of variables that influence lamb As a result, all of these can help to lessen the various risk morbidity and mortality. Factors such as lamb sex, birth factors and their negative impacts. Moreover, further weight, umbilical care, method and time of colostrum extensive examinations of lamb morbidity and mortality feeding were risk factors for lamb morbidity, while birth should be conducted to assess the actual effect of lamb weight, lambing difficulty, dams’ parity, method and time morbidity and mortality on sheep production in the of colostrum feeding were risk factors for lamb mortal- research region. ity at all ages, whereas birth season had did not affect morbidity. Infectious diseases such as diarrhea and pneumonia were the leading cause of lamb mortality fol- Methods lowed by mismothering, predators, management issues, Study area and unknown reasons. Diarrhea, pneumonia, dysentery, This study was conducted in the Gewata district of Kaffa internal parasites, and constipation were found to be the Zone, southern Ethiopia, it is located about 600 km most common lamb diseases in the study area. Diseases, and 869 km from Addis Ababa. From an agroecologi- a lack of animal health specialists, a lack of medications, cal point of view, the Gewata region is 10% lowland and the period between vaccinations were all listed as (< 1,500 m.a.s.l), 55% mid-altitude (1,500–2,300 m.a.s.l), restrictions to sheep production in the study area. Fesseha et al. Animal Diseases (2023) 3:11 Page 10 of 13 and 35% highland (> 2,300 m.a.s.l). The altitude is Where SE is the standard error. between 1400 m and 2,700 m above sea level. Gewata By considering the standard error of 0.05 with a 95% woreda is located between 34°45′ to 36°10′ east longi- coefficient interval, N = 0.25/0.05 = 100. However, 408 tude and 5°40′ to 7°40′ north latitude (Fig.  3). The aver - animal owners participated in the questionary sur- age annual temperature is 13 to 36 degrees Celsius and vey from the six kebeles during the survey to increase the annual rainfall is 900 to 1400 mm. Beekeeping and precision. mixed crop production are the main sources of income The number of participants was selected on a house - for the majority of the population. The main crops grown hold basis from the six study sites. These six sites/kebe - in the region are grains such as wheat, barley, teff, leg - les were selected since they were the main target site of umes, maize, and anise. The main livestock raised in the the project of the Bonga breeding center. Moreover, the region is cattle (105,558), sheep (25,948), goats (21,748), households were chosen based on criteria such as acces- horses (9,629), mules (1,012), donkeys (1,193), chickens sibility, the presence of greater than two lambs, the live- (123,070), and hives (82,969) (GDLFO 2020). stock-crop mixed production system, animal owners’ experience in extension programs, and owners’ willing- Study subjects and animals ness to participate in the study. Smallholder farmers in selected districts were the tar- get populations. They were chosen at random fashion Data collection methods and sources from six kebeles (peasant associations) (PA). The Indig - Data were obtained from primary and secondary data enous breed of sheep also known as the “Bonga” breed/ sources used during the study period. Primary data were type were the study animals. The study involved birth- collected through semi-structured interviews, FGD, farm to-weaning lambs kept under extensive, semi-intensive, observations and  408 purposively selected households. traditional systems of small-scale mixed crop-livestock During the interview, major causes of lamb morbidity production. The age of the lamb was estimated from and mortality were assessed. available birth records and dentition, and eight tem- porary incisors develop during the first month of life. Observational study and clinical examination Health of each lamb was determined through detailed The study involved monitoring lamb morbidity and physical and clinical examination. mortality in selected six sites during the study period. All lambs in the selected flock were strictly monitored starting from birth to weaning age. The regular follow- Study design up and clinical examinations were done by veterinar- A longitudinal prospective survey was employed from ians who were working in the breeding center as well June 2020 to July 2021 on 408 randomly selected farm- as animal health extension workers assigned by the Dis- ers located in six purposively selected kebeles in Gewata trict Agricultural Office. Veterinarians visited the lambs woreda, to determine the cumulative incidence of mor- every month, and the investigators performed emer- bidity and mortality in lambs and to identify potential gency visits in addition to routine visits when there was risk factors. These were intended to collect a one-year a need for a health evaluation of the lambs in response data set (June 2020 to July 2021) of lamb morbidity and to a request from flock owners. Every day, animal health mortality. Traditional survey methodologies, as well as extension workers visited the research animals and participatory epidemiology tools and data collection and recorded their health status using a recording format. interpretation concepts, were used in the study. Lamb During the farm visit, lambs with apparent signs of ail- owners who own animals took part in determining the ment were subject to a detailed clinical examination. A reasons and assessing the effect of lamb morbidity and change in vital signs (rectal temperature, heart rate, res- mortality, as well as other limits on sheep productivity. piratory rate, the color of mucous membranes, palpa- Dates of birth, birth weight, sex, type of birth, and date tion of superficial lymph nodes, skin condition, joints, of death of lambs were gathered from the animals’ data and feet examination, depressed mentation, poor suckle recording book of the community-based Bonga sheep reflex, weakness and recumbency) discovered during the breed improvement cooperatives. examination was documented on a predetermined for- mat. Moreover, lambs’ health was evaluated via objective Sample size determination and sampling methods criteria of appetite, fecal consistency, hydration status, The sample size was determined using Arsham for - and behavior. After these detailed clinical and physical mula (Arsham 2005). examinations, animals were categorized as “apparently 0.25 healthy” or “diseased” (Hadgu et  al. 2021; Mohammed N = SE et al. 2020). F esseha et al. Animal Diseases (2023) 3:11 Page 11 of 13 Questionnaire survey and focus group discussion spreadsheet for later data management and analy- A semi-structured questionnaire was developed to collect sis using STATA 13 statistical software. Morbidity and information on the potential factors associated with the mortality rates were calculated using the true incidence risk of lamb morbidity and mortality in the study area. The rate, which was defined as the number of new cases of questionnaire was pre-tested and administered in person diseased cases/mortality that occurred during the fol- to the farmer if one was available, or to an animal health low-up period divided by the number of lamb months- worker most responsible for animal management. The at-risk (Sullivan 2016). For the morbidity rate, the time at information gathered includes variables at the lamb and risk was measured from the start of the study until the flock levels, as well as other farm management practices. lamb developed a clinical sign of any illness. Further- Focus group discussion (FGD) was conducted using a more, a lamb that had one illness was considered to be purposive sampling technique with farmers having indig- at risk for another. The mortality risk time was calculated enous knowledge of animal disease experience to acquire from the time a lamb is enrolled in the study (soon after relevant information. A total of 54 participants were birth) until death from any cause occurs. A lamb with selected (each focus group with six participants with a a disease condition was also considered to be at risk of total of nine FGDs from six kebeles). Interviews with death. Lamb who dropped out (lost to follow-up) from key informants (Site animal health assistance and animal the study before the end of the observation period or who production experts) were used purposively. Addition- remained event-free (morbidity or mortality) at the end ally, the diseases that affect lambs in the area, as well as of the observation period were censored, which is known their local names, seasons of occurrence, and traditional as right censoring. treatments for lamb ailments, are all discussed during Time-to-event data were analyzed using non-par- the FGD. Finally, FDG were used to rate illness severity ametric and semi-parametric methods. The Kaplan- and age groups in distinct lamb diseases with recognized Meier (K-M) lifetable analysis, a popular non-parametric local names. Secondary data were also gathered from the approach, was used to compute and describe in tabular district livestock and fishery office and extensively pub - form the cumulative survival probability and cumulative lished data at the study site (Supplementary file). incidence of lamb morbidity and mortality from birth to three months of age. Furthermore, the K-M curves were used to plot cumulative survival data based on age Description of the variables groups and exposure factors studied. The survival prob - Outcome variable: The morbidity or mortality of lambs ability was calculated using the K-M approach and the from birth to three months is the outcome (dependent formula in Eq. (1) or response) variable for this study. Because the variables are dichotomous (yes or no), they were labeled with a 1 if (1) the event of interest occurred, and a 0 if it did not occur where St is survival probability past interval t; Nt is the during the study’s observation period. number at-risk during interval t; and Dt is the number Independent variables: The current study consid- of disease events or deaths during interval t. The cumu - ers sex, lambing season, weaning age, flock size, birth lative incidence, or cumulative failure probability, was weight lambing difficulty, dam’s parity number, umbili- easily calculated as 1-St using the K-M approach. Censor- cal care (yes/no), a mix of the lamb of different ages, ing was assumed to be independent of the likelihood of time lamb ingested their first colostrum meal, method developing the outcome event, and survival probabilities of colostrum feeding, hygiene, and farmers’ educa- were assumed to be comparable in participants recruited tional status as potential independent variables or pre- early and late in the study (non-informative censoring). dictors of lamb morbidity and mortality. The month The log-rank test was used to statistically test the hypoth - in which the study lamb was born is referred to as the esis that there is no difference in the survival curves lambing season. Thus, months with short to heavy rain between the groups of categorical predictors studied and (April–August) are labeled “wet season,” while months to determine whether the predictor should be included in with no rain (September–March) are labeled “dry the final model. To select a variable for the multivariable season.” model, a P value cut off at 0.25 from the log-rank test was used as a criterion. A multivariable Cox proportional hazards regres- Data analysis sion model, a semiparametric approach, was used to Data from questionnaire interviews and focus group analyze risk factors associated with lamb morbidity discussions were entered and stored in an MS Excel Fesseha et al. Animal Diseases (2023) 3:11 Page 12 of 13 Availability of data and materials and mortality. The utilized Cox proportional hazards The data will be provided upon the request of the corresponding author. regression model is denoted by Eq. (2) Declarations (2) Ethics approval and consent to participate where h(t) is the expected hazard at time t, h0(t) is the The Institutional Review Board of Wolaita Sodo University (IRB) has approved the ethical approval of the current study. The purpose of the study was com- baseline hazard, X1, X2, Xp are the predictors (or inde- municated to the participants and informed consent was obtained using oral pendent variables), and β1 þ β2 þ…. βp are the coeffi - informed consent approved by the institutional ethics committee. Throughout cients for each independent variable. The baseline hazard the investigation, identifiers such as personally identifiable information have been excluded and kept confidential. Photos and videos of study participants is the risk that exists when each independent variable is were kept anonymous. Participation in the study was completely optional. equal to zero. The Cox model analyzes the time to event Those who do not want to participate or wish to end their participation have about multiple factors at the same time and provides esti- been given the freedom to do so. mates of the strength of the effect (hazard ratio, HR) for Consent for publication each constituent factor. The final model was constructed Not applicable. by stepwise backward elimination of variables that were Competing interests not significant at the 5% level. Potential confounders All authors declare no competing conflicts of interest. were controlled at every stage of model construction. A variable was considered a confounder if the coefficients Author details School of Veterinary Medicine, Wolaita Sodo University, Wolaita Sodo, Ethio- of the remaining variables changed by 20%, and these pia. Gewata District Animal Health Expert, Kaffa Zone, Bonga, Ethiopia. were kept in the model even if they were not significant. The Cox proportional hazard model assumed that the Received: 22 November 2022 Accepted: 5 March 2023 hazards are proportional, which means that the relative hazard remains constant over time with different predic - tors or covariate levels (49). We used the Schoenfeld and References scaled Schoenfeld residuals to test the proportionality Abdelqader, A., R. Irshaid, M.J. 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Journal

Animal DiseasesSpringer Journals

Published: Apr 14, 2023

Keywords: Gewata; Incidence; Lamb; Morbidity; Mortality; Ethiopia

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