Lamb Survival and Ewe Longevity in Kenya’s Semi-Arid Lands: A Case of the Red Maasai and Dorper Sheep

Lamb survival and ewe longevity are vital to maintaining flock size in any sheep production system, especially in arid and semi-arid lands where animals battle harsh climates and limited forage. In this analysis, Cox and Weibull hazard models were used to analyse data from 6313 lambs and 2003 ewes born between 2003 and 2022 to assess pre- and post-weaning lamb survival to yearling age, as well as ewe longevity up to 6 years. The models use hazard functions to account for all the information available from animals that survive and live past a given time. They also consider time-dependent variables and non-normality of the data since survival data is heavily skewed. Pre-weaning mortality was lower (5%) than post-weaning mortality (17%), with Dorper breeds showing the highest post-weaning mortality (24%). Non-genetic factors like season of birth, birth weight, and type of birth significantly affected the risk of mortality. Heritability estimates for pre-weaning survival (0.10–0.14) were moderate, indicating selection potential. The F1 cross (50% Dorper–50% Red Maasai) outperformed the 75% Dorper crosses in both lamb survival and ewe longevity. These findings present opportunities for targeted breeding and management to boost flock sustainability, reduce economic losses, and support pastoral livelihoods in climate-vulnerable regions.