Effect of pre-weaning selection on estimates of genetic parameters and breeding values for post-weaning growth rate of beef bulls on test |
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Authors: | M L Mashiloane K A Nephawe A Maiwashe D Norris J W Ngambi |
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Institution: | (1) Department of Animal Production, University of Limpopo, Private Bag X 1106, Sovenga, 0727, South Africa;(2) Limpopo Department of Agriculture, Private Bag X 9487, Polokwane, 0700, South Africa;(3) ARC-Livestock Business Division, Animal Production Institute, Private Bag X2, Irene, 0062, South Africa |
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Abstract: | Data on South African Angus cattle consisting of 45 259 records on weaning weight (WWT), 4 360 records on average daily gain
from on-farm test (ADG-D) and 1 118 from centralized test (ADG-C) were analyzed to evaluate the effect of pre-weaning selection
on estimates of genetic parameters and subsequent estimated breeding values (EBV) for post-weaning average daily gain. (Co)variance
components and genetic parameters for weaning weight (WWT), ADG-C and ADG-D were estimated by REML procedures fitting three
different animal models. Model 1 was a univariate model of WWT, ADG-C or ADG-D and did not account for the effect of pre-weaning
selection on post-weaning ADG. Model 2 was a two-trait model of WWT and either ADG-C or ADG-D. Model 3 was a multi-trait animal
model including WWT, ADG-C and ADG-D. Estimates of heritability for ADG-C were 0.39 ± 0.080, 0.42 ± 0.060 and 0.44 ± 0.010
from Model 1, 2 and 3 respectively. Corresponding estimates for ADG-D were 0.18 ± 0.020, 0.19 ± 0.020 and 0.21 ± 0.020 respectively.
Rank correlations based on EBVs for ADG-C for all bulls were 0.92, 0.83 and 0.94 for Model 1 vs. Model 2, Model 1 vs. Model
3, and Model 2 vs. Model 3, respectively and they indicated a possible re-ranking of bulls when including or excluding a correlated
pre-weaning trait. Rank correlations for ADG-D also followed a similar trend. Inclusion of pre-weaning information in genetic
analysis for post-weaning average daily gain is necessary to account for selection at weaning. |
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