Related Experiment Videos
Genetic relationships between calving interval and body condition score conditional on milk yield
J E Pryce1, M P Coffey, S H Brotherstone
1Animal Breeding and Genetics Department, Scottish Agricultural College, Edinburgh, UK. jpryce@lic.co.nz
Journal of Dairy Science
|July 31, 2002
Summary
Dairy cows with lower body condition scores (BCS) have longer calving intervals (CI), a problem worsened by high milk production. Maintaining BCS during selection may reduce CI increases but won't improve fertility.
Area of Science:
- Animal Science
- Dairy Cattle Genetics
- Reproductive Performance
Background:
- Body condition score (BCS) is a key indicator of dairy cattle energy status.
- BCS is heritable and genetically linked to reproductive performance.
- There is interest in incorporating BCS into selection indexes for fertility.
Purpose of the Study:
- To assess the genetic covariance between BCS and fertility (calving interval, CI), accounting for milk yield.
- To understand how BCS and milk yield influence reproductive performance in dairy cattle.
- To evaluate the impact of selection strategies on BCS, milk yield, and CI.
Main Methods:
- Utilized calving interval (CI) as the measure of reproductive performance.
- Calculated genetic correlations between BCS and CI before and after adjusting for milk yield.
- Applied selection index theory to model the effects of different selection strategies.
Main Results:
- The genetic correlation between BCS and CI was -0.48 before and -0.22 after adjusting for milk yield.
- Lower BCS is associated with longer CI, especially in high-producing cows.
- Selecting for milk yield alone increases milk production but also increases CI and decreases BCS.
Conclusions:
- Restricting genetic change in BCS while selecting for milk yield can reduce the rate of CI increase but does not improve fertility.
- Selection strategies must consider the complex interplay between BCS, milk yield, and reproductive performance.
- Further research is needed to develop economically driven selection indexes that balance these traits for improved dairy cattle profitability.