Steers (n = 125) of known percentage Angus (A) and Brahman (B) breeding (A = 31, 3/4A:1/4B = 32, 1/2A:1/2B = 31, 1/4A:3/4B = 31) were slaughtered after being fed as calves during the cool period of the year or fed as yearlings during the warm period of the year. Steers were slaughtered at equivalent outside fat thickness as monitored visually and with real-time ultrasound. Warner-Bratzler shear (WBS) force increased and sensory panel tenderness decreased as percentage Brahman increased. Loin muscle characteristics indicated that differences in tenderness between breed groups were not attributed to cold shortening effects or differences in amount or integrity of connective tissue. Fragmentation values suggested that breed group tenderness differences probably resulted from differences in the muscle fiber component. A 10-d postmortem aging study revealed a differential breed group response to postmortem aging, suggesting that breed groups differed in amount and(or) activity of naturally occurring proteolytic enzymes in muscle tissue.

Steers (n = 165) of known percentage Brahman (B) and Angus (A) breeding were used to study effects of breed group (A, 3/4A:1/4B, 1/2A:1/2B, 1/4A:3/4B), age-season of feeding (calves fed during the cool season vs yearlings fed during the warm season) and slaughter end point (less than .90, 1.0 to 1.15, 1.27 to 1.40, greater than or equal to 1.5 cm of adjusted fat over the ribeye) on feedlot performance and carcass characteristics. The 1/2B and 3/4B steers had heavier (P less than .05) initial and final feedlot weights than the A and 1/4B steers and higher (P less than .05) unshrunk ADG than the A steers did. Breed types did not differ for feed efficiency. Yearling steers fed in the warm season had higher (P less than .05) unshrunk ADG than calves fed in the cool season, but ADG calculated on an empty-rumen basis did not differ between the two age-seasons of feeding. Calves fed in the cool season were more efficient (P less than .05) than yearlings fed in the warm season when efficiency was expressed on an empty-rumen basis; however, on a live weight basis there was no difference in feed efficiency. No breed group by age-season of feeding interactions on performance were detected. Slaughter end point did not significantly affect feed efficiency on an empty-rumen basis. The 1/2B and 3/4B steers had smaller ribeye areas (REA) per 100 kg hot carcass and lower marbling scores than the 1/4B and A steers. Yearlings fed in the warm season produced heavier carcasses (P less than .05) than calves fed in the cool season. As s.c. fat thickness at slaughter increased, hot carcass weight and numerical yield grade increased, whereas REA per 100 kg of hot carcass decreased. Marbling also increased as fatness increased up to about 1.5 cm subcutaneous fat.

A 2-yr study was conducted to evaluate the effects of a high-energy creep feed, preweaning zeranol implants and breed type on calf and cow performance. Two hundred calves sired by Brahman and Romana Red bulls out of Angus and Angus x Brown Swiss reciprocal crossbred (F1) dams were stratified by breed type and sex to three creep treatments: no creep feed (NC); long-term creep (LC), creep-fed from 56 to 210 d of age (weaning); and short-term creep (SC), creep-fed from 146 to 210 d of age. Alternate calves within sex, breed type and creep treatment were implanted with 36 mg of zeranol at an average of 56 d and reimplanted 90 d later. The LC and SC calves had heavier (P less than .001) 210-d weights than NC calves (264 and 257 vs 231 kg, respectively), and the LC calves were heavier (P less than .001) at 146 d than NC calves. The LC calves had higher (P less than .001) ADG from 118 to 210 d of age and higher 146 and 210-d condition scores than did NC calves. Pregnancy rate was not affected (P greater than .46) by creep treatment of calf. Zeranol implants increased (P less than .01) 146- and 210-d weights (184 vs 175 kg and 259 vs 243 kg) and ADG during all periods to weaning. Brahman-sired calves had higher (P less than .005) 146- and 210-d weaning weights and frame scores than Romana Red-sired calves.(ABSTRACT TRUNCATED AT 250 WORDS)

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A total of 132 steers, produced over a two-year period in a diallele crossbreeding program in which Angus (A) , Brown Swiss (BS) , and A x BS reciprocal F-| crossbred cows were bred to bulls of the same three breed-types, were group-fed by breed-type to about 1 cm outside fat. The mathematical model used to determine main and interaction effects included breed of sire, breed of dam, year, and all two-way interactions, plus initial feedlot age and outside fat as covariates. Maternal and individual components of heterosis and additive breed effects were estimated. Additive effects for the Angus breed were expressed as deviations from the Brown Swiss. Maternal additive effects of the Angus breed on initial weight, slaughter weight, weight per day of age, warm carcass weight, and warm carcass weight per day of age were significant and negative. Individual additive effects for the Angus were negative and significant for all feedlot traits except average daily gain, and were significant for all carcass traits except ribeye area per 100 kg warm carcass and percentage of kidney, pelvic and heart fat Maternal heterosis effects were significant and in the desirable direction only for initial feedlot weight (P<.05), slaughter age (P<.10), and days on feed (P<.01). Individual heterosis effects were significant only for carcass maturity (-5.5 of a score) and marbling (.95 of a degree) Angus-sired steers had lighter initial and slaughter weights and weight per day of age than those sired by Brown Swiss bulls. Angus-sired steers were also younger at slaughter, required fewer days on feed , and consumed less dry matter than Brown Swiss-sired steers. Angus-sired steers also produced younger, lighter-weight carcasses with smaller ribeyes , less weight per day of age, more marbling, lower cutability, and with higher tenderness ratings. Steers sired by F-j bulls were intermediate to the parent breeds in the above traits, but did not differ significantly from Angus-sired steers for initial weight, weight per day of age, carcass weight per day of age, or tenderness, or from Brown Swiss-sired steers for yield grade and marbling score. Breed of dam effects were very similar to those for breed of sire. Breed of sire by breed of dam interaction effects were significant for days on feed, slaughter age, marbling score, and Warner-Bratzler shear value.