Estimation of genetic parameters and genetic trends for growth, reproductive, and survival traits of Bonga sheep using multi-variate animal model

Abstract

The community-based breeding program was introduced to enhance the productivity of Bonga sheep. Data evaluating animals’ potential regarding key traits was gathered from 2009–2021. This study estimated covariance components and genetic parameters for growth (birth, weaning, and six-months weight), reproductive (lambing interval, annual reproductive rate, litter size at birth and weaning, litter weight at birth and weaning), and survival (0–3, 3–6, and 0–6 months) traits using a multivariate animal model. The Average Information Restricted Maximum Likelihood method in WOMBAT was used for growth and reproductive traits, while Derivative-free MUltivariate analysis was employed for survival traits. The results revealed that the additive heritability for growth, reproductive, and survival traits ranged from 0.15–0.26, 0.06–0.08, and 0.10–0.17, respectively. The variance ratio of maternal permanent environment for growth traits ranged from 0.07–0.25, while that of animal environment for reproductive traits ranged from 0.33–0.45. Maternal genetic heritability for birth, weaning, and six-months weights were 0.14, 0.19, and 0.19, respectively, while it ranged from 0.01–0.14 for reproductive traits. Additive genetic correlations among growth traits ranged from 0.04–0.79, and from 0.36–0.62 between growth and reproductive traits. Low to high additive genetic correlations (0.002–0.537) were recorded between growth and survival traits. Significant (P<0.001) and positive genetic trends were observed for most reproductive traits, though annual genetic trends were low. Moderate additive heritability for growth traits indicates potential for genetic improvement via selection, while the pronounced environmental impact on reproductive and survival traits suggests the need for improved management practices in addition to selection. The presence of positive genetic correlations of growth traits with reproductive and with survival traits suggests that selecting for improved weaning/six-month weight has the potential to enhance ewe productivity and lamb survival. This highlights the importance of considering both growth and reproductive/survival traits in breeding programs to achieve optimal outcomes in sheep production.