AI Article Synopsis
- The study analyzed production records of nearly 836,000 Ontario Holsteins from 1958 to 1990 to investigate how age and month of calving interact with the year of calving on milk and fat production.
- Significant interactions were found between age and year for milk and fat production, but not for fat percentage; only a few month-year interactions were significant for specific age groups.
- The results suggest that when evaluating genetic performance, it’s important to consider the interactions between age, month, and year of calving instead of just adjusting for age and month in the model.
Article Abstract
Production records of 835,789 Ontario Holsteins calving between 1958 and 1990 were used to determine the presence of an interaction of the age and month of calving of cows with the year of calving for production of milk and fat and fat percentage. An animal model was employed including the effects of herd-year-season of calving, interaction of age and month of calving with year of calving, animal additive genetic effects, and permanent environmental effects. Tests for interactions of age with year within months of calving were significant for production of milk and fat, but not for fat percentage. Tests for interactions of month with year within age groups were significant for only a few age groups in the second and third parties. The implication of these findings on genetic evaluation is that an interaction of age and month of calving with year of calving should be included in the animal model for genetic evaluations rather than preadjusting production for age and month of calving.
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| http://dx.doi.org/10.3168/jds.S0022-0302(93)77723-1 | DOI Listing |
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