Related Experiment Videos
Genotype x environment interaction for grazing versus confinement. I. Production traits
J F Kearney1, M M Schutz, P J Boettcher
1Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
Journal of Dairy Science
|February 6, 2004
Summary
Genotype x environment interaction (GxE) in US Holsteins shows minimal impact on production traits between grazing and confinement systems. While some sire reranking occurs, separate genetic evaluations are not yet justified for these management systems.
Area of Science:
- Animal Genetics and Breeding
- Dairy Science
- Agricultural Systems
Background:
- Dairy herd management systems, specifically grazing versus confinement, can influence the expression of genetic potential in Holstein cattle.
- Understanding genotype x environment interaction (GxE) is crucial for accurate genetic evaluations and breeding strategies in diverse management settings.
Purpose of the Study:
- To investigate the presence and magnitude of genotype x environment interaction (GxE) for milk, fat, and protein production traits in US Holstein populations.
- To compare the performance of sires' daughters in grazing herds versus confinement herds and assess the implications for genetic evaluations.
Main Methods:
- Utilized linear regression of mature equivalent yields on sire's Predicted Transmitting Abilities (PTA) for milk, fat, and protein in grazing and confinement herds.
- Estimated heritabilities and genetic correlations using a bivariate animal model and restricted maximum likelihood (REML).
- Calculated product-moment and rank correlations between sire estimated breeding values (EBVs) derived from each environment.
Main Results:
- Regression coefficients for PTA were lower in grazing herds (0.76-0.78) compared to confinement herds (0.96-0.99), suggesting potential overestimation of daughter differences by current PTA in grazing systems.
- Heritabilities ranged from 0.2 to 0.25 with small differences between environments. Genetic correlations were high (0.88-0.91), indicating substantial genetic similarity across systems.
- Rank correlations between sire EBVs from the two environments were moderate (0.59-0.66), with a mean rank change of 27 for the top 100 sires, indicating some sire reranking.
Conclusions:
- While a genotype x environment interaction exists for Holstein production traits between grazing and confinement systems, it is not substantial enough to warrant separate genetic evaluations.
- Current sire PTA may overstate expected daughter differences in grazing herds due to lower regression coefficients.
- The observed sire reranking suggests that management systems influence trait expression, but overall genetic merit remains largely consistent across environments.