**Background:** Sheep husbandry is vital for smallholder livelihoods in sub-Saharan Africa, but production is constrained by suboptimal animal health and poor management. Preventive herd health management—including proper nutrition, biosecurity, monitoring, and strategic breeding—can improve ewe health, lamb survival, and weight gain. Ethiopia has over 40 million sheep, and the Amhara region is densely populated with small ruminants. This study aimed to monitor lamb weight gain and mortality and identify associations with ewe age, health, lamb health, and management practices in intervention and control villages in the Menz area.
**Methods:** This longitudinal study enrolled 208 lambs from 206 ewes in 143 flocks across seven villages (three intervention, four control) from September 2019 to May 2020. Lambs were examined by a veterinarian within 7 days of birth (median 5 days) and weighed; clinical signs were recorded for both lambs and ewes. Lambs were followed monthly for weight and mortality. Farmers completed a questionnaire on management practices, scored into categories (disease prevention, mating, gestation, lambing, first week care, second week to 5 months). Associations with weight gain were analyzed using multilevel mixed-effects linear regression with stepwise backward elimination (p<0.05 retained). Mortality associations were assessed with univariable Fisher's exact test and logistic regression; multivariable analysis was not performed due to low mortality.
**Key Results:** At initial visit, 38% of lambs had at least one clinical sign (most common: diarrhoea 22.1%), and 29.6% of ewes had clinical signs (most common: respiratory 10.3%). Mean lamb weight at first visit was 3.2 kg; mean weight gain was 3.1 kg at 1 month and 9.2 kg at 5 months.
For weight gain from 0 to 1 month (n=192), significant positive associations were found with: intervention village (coefficient 0.89, 95% CI 0.38–1.41, p=0.001), ewe age 2–4 years (0.30, 0.04–0.56, p=0.002), ewe age >4 years (0.51, 0.21–0.81, p=0.001), ewe BCS >2 (0.37, 0.11–0.63, p=0.005), ewe fleece cleanliness >2 (0.68, 0.17–1.19, p=0.009), and ewe genital discharge (0.45, 0.04–0.85, p=0.030). Significant negative associations were: ewe abnormal udder (−0.65, −1.14 to −0.16, p=0.009), lamb respiratory signs (−0.35, −0.68 to −0.02, p=0.035), lamb gastrointestinal signs (−0.32, −0.58 to −0.06, p=0.016), lamb umbilical cord inflammation (−0.56, −1.08 to −0.05, p=0.033), and farmer education (non-governmental/unfinished primary) (−0.51, −0.82 to −0.19, p=0.002).
For weight gain from 0 to 5 months (n=179), significant positive associations were: ewe age 2–4 years (0.93, 0.31–1.55, p=0.003) and disease prevention score 11–20 (0.82, 0.07–1.57, p=0.032). Significant negative associations were: female lamb sex (−0.54, −1.02 to −0.05, p=0.030), lamb respiratory signs (−0.86, −1.62 to −0.10, p=0.026), and gestation score 11–20 (−0.90, −1.62 to −0.18, p=0.014).
LAMB MORTALITY
13 lambs (6.3%) died during follow-up; 46% died before the first follow-up. Causes included diarrhoea (n=3), respiratory disease (n=3), neurological disease (n=1), bee sting (n=1), sudden death (n=5), and unspecified (n=1). Univariable analysis showed mortality was associated with lower birth weight (coefficient −0.54, p=0.022), respiratory signs at initial visit (OR 5.79, p=0.003), and higher combined management score (OR 3.41, p=0.038). Mortality was lower in intervention vs control villages (5.4% vs 7.4%) but not statistically significant (p=0.552).
**Clinical Implications:** This study demonstrates that preventive herd health interventions—particularly those improving ewe nutrition and health, and managing lamb diseases early—can significantly enhance lamb weight gain and reduce mortality in resource-poor settings. The first month of life is critical; lambs with respiratory, gastrointestinal, or umbilical signs, or born to ewes with udder abnormalities, are at risk for poor growth. Interventions such as ensuring adequate ewe body condition (BCS >2), managing udder health, and implementing disease prevention strategies (vaccinations, anthelmintics, biosecurity) are associated with improved outcomes. The low overall mortality (6.3%) compared to previously reported rates (up to 50%) suggests that even modest management improvements can have substantial impact. These findings are relevant across sub-Saharan Africa where similar production systems exist.