Calving performance records (965,417) from purebred American Angus herds throughout the United States were used to study dystocia and early calf mortality during the period from 1972 to 1985. A sample of 53 (n = 83,467) herds was used to establish reasonable limits on the expected frequency of dystocia and mortality within and among herds that have good reproductive management programs and to verify the frequencies of scores in all other herds (n = 4,130) reporting calving performance information. The data were analyzed by logistic regression models. Dystocia and perinatal mortality, to a lesser extent, were found to be more frequent in heifers than in cows. The odds of unassisted births vs births with major difficulty were 11.58 times greater in cows than in heifers. In heifers, the odds of an unassisted birth increased with age of dam and decreased with birth weight of calf. At a baseline age of 22 mo the odds of an unassisted birth for calves weighing 30 and 40 kg were .13 and .02 times lower than the odds for calves weighing 20 kg. Alternately, at 29 mo, the odds of an unassisted birth for heifers producing a 20-kg calf were 4.53 times greater than at 22 mo. Survival of calves to 24 h in heifers was primarily affected by birth weight. Heifers producing calves at intermediate weights of 29 kg had higher odds of producing live calves at all ages. Considering all heifers calving at 22 to 29 mo relative to 20-kg calves, the odds for survival to 24 h were 3.83 times greater for 29-kg calves and lower by a factor of .52 for 40-kg calves.

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RESUMO -Foram analisadas doze características quantitativas das carcaças de 162 machos bovinos inteiros pertencentes aos grupos Caracu (Ca), Charolês (Ch), 3/4Ca+1/4Ch, 3/4Ch+1/4Ca, 5/8Ca+3/8Ch e 5/8Ch+3/8Ca, nascidos no período de 1988 a 1993. As médias para idade e peso ao início do período de confinamento, duração do confinamento, idade e peso ao abate foram, respectivamente, 712 dias, 362 kg, 99 dias, 811 dias e 489 kg. Durante o confinamento, os animais receberam silagem de milho à vontade e uma ração concentrada (79% NDT, 17,8% PB) fornecida à base de 1% PV/animal/dia. Os resultados mostraram que os grupos Ch e Ca não diferiram quanto ao peso de carcaça quente, ao rendimento de carcaça quente, às porcentagens de costilhar e gordura e ao peso da porção comestível da carcaça (PCC). O Ch superou o Ca para a área da seção transversal do músculo Longissimus dorsi (AML), o escore de conformação da carcaça (CONF) e as porcentagens de serrote e músculos. Animais Ca apresentaram maior espessura de gordura de cobertura e maiores porcentagens de dianteiro (PED) e ossos que os do grupo Ch. Houve resposta heterótica para PCQ, AML, CONF, PCC e PED. As duas gerações avançadas de cruzamentos alternados Ch x Ca foram superiores à média das raças paternas para PCQ, AML, CONF, PCC e PED. O cruzamento alternado Ch x Ca produz animais com características de carcaça superiores às dos Charolês e Caracu puros.Palavras-chave: Charolês, Caracu, cruzamentos, carcaça Carcass Traits of Charolais, Caracu and Reciprocal Crosses Finished in FeedlotABSTRACT -Twelve quantitative carcass traits of 162 Charolais (Ch), Caracu (Ca), 3/4Ca+1/4Ch, 3/4Ch+1/4Ca, 5/8Ca+3/8Ch and 5/8Ch+3/8Ca, born from 1988 to 1993, were analyzed. Averages for age at the beginning of the confinement period, initial weight, length of confinement period, final age and final weight were, respectively, 712 days, 362 kg, 99 days, 811 days and 489 kg. During the confinement period, the animals were fed corn silage ad libitum and a concentrate diet (79% TDN, 17,8% CP) offered on the basis of 1% LW/animal•day. The results showed that the groups Ch and Ca did not differ with respect to hot carcass weight (PCQ), dressing percentage (RCQ), side cut percentage (PEC), fat percentage (PEG) and weight of edible portion (PCC). Charolais animals were superior to Ca animals for Longissimus dorsi area (AML), conformation score and for the percentages of saw cut (PES) and lean tissue (PEM). Caracu animals showed higher fat thickness (EGC), and higher percentages of forequarter (PED) and bones (PEO) than those of the Ch group. There was heterotic response for PCQ, AML, conformation score, PCC and PED. The averages of the two-advanced crisscross Ch x Ca generations were higher than the parental averages for PCQ, AML, conformation score, PCC and PED. Rotational crossbreeding of Charolais and Caracu produces animals with superior carcass characteristics than the purebred Charolais and Caracu.

Foi analisado o desempenho ponderal pré-desmama de bezerros Nelore (N), Guzerá x N (GN), Red Angus x N (RN) e Marchigiana x N (MN), oriundos de um experimento de cruzamentos realizado na Estação Experimental do IAPAR de Paranavaí, nascidos no período de 1985 a 1998, produzidos por meio de inseminação artificial, em duas estações anuais de nascimento (janeiro a abril e julho a dezembro). Foi utilizado o método dos quadrados mínimos para análise de 721 observações de pesos ao nascimento (PNT) e 686 de pesos à desmama (PDS) e ganho médio diário de peso do nascimento até a desmama (GMD<FONT FACE=Symbol>_</FONT>ND). Para PNT, o efeito de classe de datas julianas com intervalos de dez dias entre classes mostrou-se mais útil para explicar variações de épocas de nascimento do que o mês de nascimento, cuja influência foi muito grande para PDS e GMD<FONT FACE=Symbol>_</FONT>ND. Para as três características avaliadas, houve importante efeito (linear e quadrático) da idade da vaca (dias) mãe do bezerro, bem como dos efeitos fixos de raça do touro ou grupo genético, ano de nascimento do bezerro e sexo do bezerro. A interação grupo genético x sexo do bezerro foi efeito importante para PNT, PDS e GMD<FONT FACE=Symbol>_</FONT>ND. O efeito aleatório de touro dentro de grupo genético foi importante para PNT, PDS e GMD<FONT FACE=Symbol>_</FONT>ND. As médias dos quadrados mínimos e respectivos erros-padrão, sempre na seqüência N, GN, RN e MN, foram: 28,5 ± 0,38 kg, 29,0 ± 0,44 kg, 29,4 ± 0,46 kg e 31,3 ± 0,47 kg, para PNT; 141,3 ± 1,47 kg, 147,6 ± 1,61 kg, 167,5 ± 1,72 kg e 162,0 ± 1,89 kg, para PDS; 0,510 ± 0,007 kg, 0,540 ± 0,008 kg, 0,627 ± 0,008 kg e 0,583 ± 0,009 kg, para GMD<FONT FACE=Symbol>_</FONT>ND.

Calving performance records from the American Angus Herd Improvement Registry files were used to estimate variance components for calving ease and survival to 24 h. Genetic parameters for direct and maternal effects were estimated by using a sire-maternal grandsire model. Data included two independent samples of 19 and 34 herds with complete calving information. Maternal variance for calving ease was much larger than the variance for the direct effect of the sire. Maternal heritability for calving ease was .27 and .20 in the two samples of herds, respectively. Heritabilities for direct effects were .21 and .07. The genetic correlations between direct and maternal effects were -.93 and -.80. There was little genetic variation in survival at birth. Parameter estimates were within the allowable parameter space in the sample of 19 herds. Heritability for the direct effect of the sire on survival was .04. Maternal heritability was .09, and the direct-maternal correlation was -.85.