Rotational Crossbreeding of Beef Cattle: Preweaning Traits by Generation

Abstract

Three successive generations of crossbreeding involving the Angus (A), Brahman (B) and Hereford (H) breeds in all possible two-breed-of-sire rotational crosses were evaluated in the Everglades of south Florida. Contemporary straightbred and crossbred progeny were produced each generation. The three successive generations of crossbred dams included first crosses (Fl), reciprocal first backcrosses (1/4-3/4 breed combinations) and reciprocal second backcrosses (3/8-5/8 combinations). The traits considered were birth weight, weaning condition score, weaning weight and the ratio of annual production to cow weight. Heterosis levels for the Brahman crosses (AB and BH) were highly signifiant and positive for all traits with values pooled over generations averaging 14.5% for birth weight, 10.5% for condition score, 17.5% for weaning weight and 24.5% for annual production/cow weight. Corresponding values for AH crosses were −3, 3 (P<.01), 5 (P<.01) and 5%, respectively. Heterosis levels, averaged over all crosses, for generations 1 through 3, were 7, 10 and 11%, respectively, for birth weight; 9, 5 and 10% for condition score; 15, 9 and 17% for weaning weight; and 28, 13 and 14% for annual production/cow weight. The two-breed rotations included in this study were effective in maintaining relatively high levels of heterosis for three generations. The average level of heterosis pooled over all crosses and generations was 18% (P<.01) for annual production/cow weight. The performance of each of the crossbred groups surpassed that of any of the straightbred groups by 3 to 50%.