Definition of season in animal model equation of Nili-Ravi buffaloes

Khan, M. S.; Bhatti, S. A.; Asghar, A. A.; Chaudhary, M. A.; Bilal, M. Q.

doi:1997.10.1.70

Article

Animal Reproduction and Physiology

Asian-Australasian Journal of Animal Sciences 1997;10(1): 70-74.
https://doi.org/10.5713/ajas.1997.70 Published online February 1, 1997.

Definition of season in animal model equation of Nili-Ravi buffaloes

M. S. Khan, S. A. Bhatti, A. A. Asghar, M. A. Chaudhary, M. Q. Bilal

Abstract

Data on 2,571 lactation records of Nili-Ravi buffaloes from four institutional herds and four field recording centers were analyzed under an animal model to see the effect of season definition on the error variance of the fitted model. Herd-year-season(HYS) was the main fixed effect along with permanent environment, breeding value and residuals as the random effects. All known relationships among the animals were considered. The error variance differed for various HYS combinations. It was minimum when then months were not grouped into seasons. The four or Five season scenarios were better than the two season scenarios. The average number of lactations represented in a HYS combination varied widely from 6 to 28. Very few subclasses for a given HYS combination warrants the use of fewer seasons for animal model evaluation of buffaloes.

Keywords: Buffaloes; Season Definition; Animal Model; Error Variance