ROLE OF MATERNAL AND CYTOPLASMIC EFFECTS IN EARLY CALF GROWTH IN A CLOSED BREEDING NUCLEUS ANGUS HERD

Abstract

Maternal and cytoplasmic inheritance was investigated in a closed Angus herd. Observed traits were birth weight, weaning weight, adjusted body weight, average daily gain, hock length and scrotal circumference. Each animal in the herd was traced to one of 18 female founders. Data was analyzed with a model including contemporary group, gender and the random effects of animal, maternal, permanent environment, and cytoplasmic line. Ratios of cytoplasmic to phenotypic variances ranged from 0.000 ± 0.002 to 0.005 ± 0.006. Genetic maternal variances had ratios ranging from 0.044 ± 0.046 to 0.156 ± 0.029. Desired genetic gains indexes were computed for all traits. Inclusion of the cytoplasmic information in the index resulted in small reductions in genetic gains in direct and maternal values that can be compensated for a corresponding increase in cytoplasmic breeding value. Selection for cytoplasmic effects will lead to increased inbreeding unless new variation is created by mutations.