Estimates of genetic Parameters for growth of Kenya Boran cattle using Random Regression models

Abstract

Data consisting of 18 884 weight records collected from 1 273 Boran cattle from birth to 24months of age were used to estimate genetic parameters for growth of Boran cattle using random regression (RR) models under a situation of small herd size and inconsistent recording. The RR model fitted quadratic Legendre polynomials of age at recording for additive genetic and permanent environmental effects. Direct heritability and permanent environmental variance as a proportion of phenotypic variance fluctuated during the early ages but stabilised at intermediate to later ages; the estimates ranged from 0.11 to 0.33 and 0.18 to 0.83, respectively. Genetic correlation estimates were positive ranging from 0.10 to unity. The estimates declined with increase in lag between the age points. Phenotypic correlation pattern was erratic between early ages, negatively low (-0.02) between the extreme data points and moderate to highly positive (>0.50) between intermediate and later points with prominent spikes along the diagonal. Conditions of small herd sizes and inconsistent recording notwithstanding, RR models have potential to model growth of Boran cattle.