Abstract

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.

GR, Wiggans, and ME Goddard

Proceedings of the New Zealand Society of Animal Production, Volume 56, , 19-21, 1996