A computationally feasible test day model with separate
first and later lactation genetic effects
G.R. Wiggans and M.E. Goddard
Animal Genetics and Breeding Unit, University of New England,
Armidale, NSW, Australia and Animal Improvement Prgarms Laboratory,
Agricultural Research Service, USDA, Beltsville, MD, USA
Proceedings of the New Zealand Society of Animal Production, 1996,
56: 19-21
In a two step analysis test day effects were estimated within herd with
adjustment for across herd effects and then the adjusted data were analysed
across herd. Genetic effects were defined for each of 10 months in milk
within first and later lactation and for milk, fat and protein giving 60 traits.
The rank of the genetic (co)variance matrix (G) was reduced to 6 such that
G retained the information to evaluate the selection objective. A
repeatability model allowed for multiple lactations with each lactation,
conceptually, expressing all 60 traits, but missing observations for 30 or
more. A canonical transformation was applied to create uncorrelated traits.
Missing values were replaced by their expectations at each round. Because
of the rank reduction, only 6 canonical traits were solved for. This system
should make evaluations more stable by removing biases due to genetic
differences in persistency and rate of maturity.
Keywords: NZSAPAB;
Test day model; canonical transformation; multi-trait; milk yield.
Download abstract in text format
Last Updated 18-03-1997
