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Estimation of genotype×environment interactions, in a grass-based system, for milk yield, body condition score, and body weight using random regression models
- Berry, D.P., Buckley, F., Dillon, P., Evans, R.D., Rath, M., Veerkamp, R.F.
- Livestock production science 2003 v.83 no.2-3 pp. 191-203
- Holstein, body condition, body weight, cobalt, dairy cows, feed quality, feeding level, genetic correlation, genetic variance, genotype-environment interaction, grazing intensity, lactation, livestock production, milk yield, regression analysis, variance
- (Co)variance components for milk yield, body condition score (BCS), body weight (BW), BCS change and BW change over different herd-year mean milk yields (HMY) and nutritional environments (concentrate feeding level, grazing severity and silage quality) were estimated using a random regression model. The data analysed included records from 7478 multiparous upgraded Holstein–Friesian dairy cows. There were G×E interactions for BCS across all environments and for BW change across different concentrate levels and silage quality environments. There was a three-fold increase in the genetic standard deviation (S.D.) for BCS change to day 60 of lactation (CS60-5) and a doubling of the genetic S.D. for BCS at day 5 (CS5) as silage quality improved. The genetic variance for CS60-5 increased as concentrate level increased and as grazing severity became tighter. There was significant re-ranking of animals for milk yield, CS5 and CS60-5 over the different HMY environments; genetic correlations fell to −0.60 between extreme HMY environments for CS60-5 and were as low as 0.41 for CS5 across different HMY environments.