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.
