Additive Breed and Heterosis Effects for Individual and Maternal Influences on Feedlot Gain and Carcass Traits of Angus, Brahman, Charolais and Crossbred Steers

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Abstract
Angus (A), Brahman (B) and Charolais (C) bulls were mated in all combinations to A, B, C, and reciprocal firstcross AB, AC and BC females in a 3 X 6 design. A total of 455 steer progeny and their carcasses were evaluated for additive breed and heterosis effects on individual and maternal influences. The traits measured were average daily gain (ADG), chilled carcass weight (CCW), thickness of fat over the rib eye (FOE), rib eye area/100 kg carcass weight (RER), Warner-Bratzler shear (WB) and USDA carcass quality grade (QG). The steer progeny were fed an average of 174 d from shortly after weaning until slaughter at an average age of 439 d. Mean values for the various traits were 976 g for ADG, 240.1 kg for CCW, .77 cm for FOE, 27.9 cm2 for RER, 5.12 kg for WB and 14.5 for QG. The additive genetic effects for the Angus breed were positive for FOE (P<.05), RER and QG (P<.01) and nonsignificantly negative for ADG, CCW and WB. Brahman breed effects were positive for FOE (P<.01) and WB (P<.01) while negative for ADG (P<.01), CCW (P<.01), RER (P<.01) and QG. Additive effects for the Charolais breed were positive for ADG (P<.01), CCW (P<.01) and RER (P<.01) while being negative for FOE (P<.01), WB (P<.01) and QG (P<.05). Individual heterosis effects for reciprocal AB, AC and BC crosses, respectively, were 163 (P<.01), 36 and 91 (P<.01) g for ADG; 37.4 (P<.01), 16.0 (P<.01) and 24.5 (P<.01) kg for CCW; .18 (P<.01), −.07 and .01 cm for FOE; −1.46 (P<.05), .10 and −.63 for RER; −.69 (P<.05), .15 and −.08 kg for WB and .12, −.43 and .43 (P<.05) for QG. Additive maternal effects for Angus dams were nonsignificant for all traits. Effects for Brahman dams were significantly positive for RER and negative for ADG and FOE. The additive maternal effects for Charolais dams were significantly positive for FOE and negative for RER. Significant maternal heterosis effects were observed only for CCW and FOE (P<.01) for firstcross AB dams and for CCW (P<.05) in AC dams. Copyright © 1982. American Society of Animal Science . Copyright 1982 by American Society of Animal Science

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