Evaluation of genetic relationship between milk yield and weaning weight in Nguni cattle

Abstract

Weaning weight and milk production are traits of economic importance in beef production and knowledge of their genetic relationship is of importance for genetic improvement. While indigenous cattle constitute a big percentage of the beef cattle population in South Africa, limited research has been done to investigate the genetic relationship between milk production and weaning weight in this type of cattle. The objective of this study was to estimate the genetic relationship between weaning weight and milk yield in Nguni cattle. Milk yield data (n = 125) were collected from 116 Nguni cows using the weigh-suckle-weigh technique from Mara Research Station located in Limpopo Province and Loskop South Farm located in Mpumalanga Province. Weaning weight data (n = 19,065) were obtained from stud Nguni cattle from 146 herds distributed throughout South Africa. Milk yield data was collected on average once per month from birth to weaning at about seven months. Editing of the data to remove observations beyond 3 standard deviations was conducted using Statistical Analysis Software. Estimates of (co)variance components for milk yield and weaning weight were calculated using PEST and VCE software. The average weaning weight, age of the calf at weaning and 24-h milk yield was 158.94 kg, 210 days and 5.25 kg/day respectively. Phenotypic variance for weaning weight and milk yield were 284.80 kg2 and 2.33 kg2 respectively. The phenotypic correlation between weaning weight and milk yield was 0.47 ± 0.025. Estimates of heritabilities from univariate analysis for milk yield, direct and maternal weaning weight were 0.16 ± 0.299, 0.48 ± 0.038 and 0.25 ± 0.025 respectively. Estimates of heritabilities from multivariate analysis for milk yield, direct and maternal weaning weight were 0.22 ± 0.238, 0.47 ± 0.039 and 0.25 ± 0.029 respectively. Estimates of genetic correlations for milk yield and maternal weaning weight, milk yield and direct weaning weight, direct and maternal weaning weight were 0.97 ± 0.063, -0.71 ± 0.416 and -0.56 ± 0.247 respectively. The results of the current study indicate that maternal weaning weight is genetically highly predictive of milk yield in Nguni cattle. It could be concluded that selection for milk production could be successfully achieved by selecting for maternal weaning weight since measuring milk yield directly could prove to be difficult under practical production setting.