ESTIMATION OF DIRECT AND MATERNAL BREED EFFECTS FOR PREDICTION OF EXPECTED PROGENY DIFFERENCES FOR BIRTH AND WEANING WEIGHTS IN 3 MULTIBREED POPULATIONS

Direct and maternal breed effects on birth and 200-d weights were esti mated for nine parental breeds (Hereford [H], Angus [A], Braunvieh [B] , Limousin [L], Charolais [C], Simmental [S], Gelbvieh [G], Red Poll [ R], and Pinzgauer [P]) that contributed to three composite populations (MARC I = 1/4B, 1/4C, 1/4L, 1/8H, 1/8A; MARC II = 1/4G, 1/4S, 1/4H, 1 /4A; and MARC III = 1/4R, 1/4P, 1/8H, 1/4A). Records from each populat ion, the composite plus pure breeds and crosses used to create each co mposite, were analyzed separately. The animal model included fixed eff ects of contemporary group (birth year-sex-dam age), proportions of in dividual and maternal heterosis and breed inheritance as covariates, a nd random effects of additive direct genetic (a) and additive maternal genetic (m) with covariance (a,m), permanent environment, and residua l. Sampling correlations among estimates of genetic fixed effects were large, especially between direct and maternal heterosis and between d irect and maternal breed genetic effects for the same breed, which wer e close to -1. This resulted in some large estimates with opposite sig n and large standard errors for direct and maternal breed genetic effe cts. Data from a diallel experiment with H, A, B, and R breeds, from g rading up and from a top cross experiment were required to separate br eed effects satisfactorily into direct and maternal genetic effects. R esults indicate that estimation of direct and maternal breed effects n eeded to predict hybrid EPD for multibreed populations from field data may not be possible. Information from designed crossbreeding experime nts will need to be incorporated in some way.