|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/1996
Publication Date: N/A
Citation: N/A Interpretive Summary: Some beef cattle producers have an interest in comparing individual bulls of different breeds for use in their herds. One method of across-breed evaluation is to use crossbred records where several breeds are represented, such as the GPE project at MARC as a basis for across-breed adjustment factors to add to within-breed genetic evaluations. Another approach is to use field records to directly compare breeds in herds with more than one breed. The research reported in this paper shows that separating calf breed effects (direct genetic) and cow breed effects (maternal genetic) from field data may not be possible. This paper demonstrates in a study of three composite (cross-bred) populations at MARC that direct and maternal breed effects probably cannot be estimated from typical field collected records of crossbred beef cattle. Records from all- way crosses of the foundation breeds and from a top cross experiment were needed to satisfactorily separate the breed direct and maternal effects. Such records are not usually available from beef producers. The results indicate records from a designed crossbreeding experiment may be necessary to develop appropriate procedures for comparing direct and maternal genetic values of pairs of bulls of different breeds.
Technical Abstract: Direct and maternal breed effects on birth and 200-d weights were estimated 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, 1/4H, 1/4A). Records from each population, the composit plus pure breeds and crosses used to create each composite, were analyzed separately. The animal model included fixed effects of contemporary group (birth year-sex-dam age); proportions of individual and maternal heterosis and breed inheritance as covariates; and random effects of additive direct genetic (a) and additive maternal genetic (m) with covariance (a,m), per- manent environment, and residual. Sampling correlations among estimates of genetic fixed effects were large, especially between direct and maternal heterosis and between direct and maternal breed genetic effects for the same breed, which were close to -1. This resulted in some large estimates with opposite sign and large standard errors for direct and maternal breed genetic effects. Data from a diallel experiment with H, A, B and R breeds, from grading up and from a top cross experiment were required to separate breed effects satisfactorily into direct and maternal genetic effects. Results indicate that estimation of direct and maternal breed effects needed to predict hybrid EPD for multibreed populations from field data may not be possible. Information from crossbreeding designed experiments will need to be incorporated in some way.