Abstract
Data collected at the Fort Keogh Livestock Research Laboratory on 912 male calves (M) and 954 heifer calves (F) in years 1967 through 1977 were used to estimate the amount of heterosis in two-way (2W) and three-way (3W) rotational crossing systems and advantages of a beef × beef composite (BC) resulting from crossing straightbreds (SB), Hereford (H), Angus (A) and Charolais (C). In conjunction with the main study, 161 male calves and 191 heifer calves produced from matings of crossbred beef × Brown Swiss sires and dams were used to compare performance of a beef × dairy composite (BSC) with the other rotational crossing and beef composite groups. All calves were raised on native range and were weaned at an average age of 193 d. Percent increases over SB shown by 2W, 3W and BC calves combined over three generations were: 3.3, 3.6 and 5.2, respectively, for birth weight; 4.4, 6.6 and 6.7 for 205-d weaning weight; 4.8, 7.3 and 7.1 for average daily gain birth to weaning; 2.0, 2.9 and 2.6 for weaning score. These estimated increases over SB were all highly significant. For gain from birth to weaning and 205-d weight, 3W was superior (P<.01) to 2W. For all growth traits, BC exceeded (P<.01) 2W but the performances of BC and 3W were similar. The weaning scores for 2W, 3W and BC calves were similar and were only 2.5 percentage points higher than scores from SB calves. The heterosis levels in each system were maintained from the first to the third generation. As sire breeds in 2W and 3W rotations, H and C consistently exceeded (P<.05 to P<.01) A for most growth traits. In 2W, the AC and HC backcross dams produced calves with heavier (P<.01) birth and weaning weight than AH backcross dams. The BSC calves were heavier (P<.01) at birth and gained faster from birth to weaning than those of 2W and 3W rotations and BC, but weaning scores of BSC calves were 3.0 percentage points lower (P<.01) than the beef crosses.
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