O objetivo deste estudo foi buscar associação entre a taxa de prenhez após inseminação e natalidade com marcadores moleculares ligados aos genes do receptor para IGF-1, LHβ, Leptina e receptores do FSH e LH. Utilizaram-se 249 vacas adultas Aberdeen Angus, das quais 199 foram submetidas a protocolos distintos para a IATF, seguida pelo repasse com touros, e 50 vacas formaram o grupo controle representado pelo acasalamento com touros. Foram avaliados o escore de condição corporal (ECC) e o escore de condição ovariana (ECO) ao início da estação reprodutiva. O ECC influenciou a taxa de natalidade, respectivamente de 55,6%, 75,8% e 82,4% (P<0,05) para os animais com ECC menor que 2,5, entre 2,5 a 2,9, e maior ou igual a 3,0, por ocasião da estação reprodutiva. Os marcadores relacionados ao gene do receptor para o IGF-1 (AFZ-1 e HEL5) mostraram associação com a taxa de natalidade. Vacas homozigóticas para o marcador AFZ-1 apresentaram 84,4% de natalidade em comparação às heterozigóticas, com 71,5% (P<0,05). A presença do alelo*161 para o marcador HEL5 foi negativa sobre a natalidade, respectivamente de 33,3% e 76,5% para vacas com e sem esse alelo (P<0,05). Esses resultados demonstram uma importante associação entre os marcadores envolvidos com o receptor para o IGF-1 e desempenho reprodutivo de vacas Angus.

The association between the reproductive performance, expressed by pregnancy rate at fixed timed artificial insemination and birth rate in the subsequent season in beef cows, and molecular markers linked to genes for IGF-1 receptor, LHβ, leptin, and FSH and LH receptors were evaluated. Data from 249 Aberdeen Angus adult cows were used in this study. One hundred and ninety-nine cows were subjected to four different protocols for FTAI, followed by clean-up bulls and 50 cows formed the control group, matted only with bulls for 90 days during the mating season. Body condition score (BCS) and ovarian condition score (OCE) were evaluated at the beginning of the breeding season. The birth rate in the following year was 75.5%, with no treatments influence. The BCS has influenced the birth rate, respectively 55.6%, 75.8% and 82.4% (P<0.05) for animals with BCS less than 2.5; 2.5 to 2.9; and greater than or equal to 3.0, at the beginning of the breeding season. The markers related to IGF-1 receptor gene (AFZ-1 and HEL5) were associated with the birth rate in beef cows. Cows homozygous for AFZ-1 marker showed 84.4% of birth rate, while heterozygous cows showed 71.5% (P <0.05). The presence of allele *161 to the HEL5 marker was negative on birth rate. Cows with this allele had only 33.3% of birth rate, while cows without this allele had 76.5% of birth rate (P <0.05). These results demonstrate a significant association between the markers involved with the IGF-1 receptor and reproductive performance of Aberdeen Angus beef cows.

Foram avaliados o desempenho e as características de carcaça de 36 novilhos Brahman (Bh), Brangus (Bg) e Hereford adaptado (He), terminados em pastejo com suplementação (PSu) ou em confinamento (Conf). Os animais foram abatidos quando apresentavam espessura de gordura maior do que 4mm. Na dieta do Conf, a relação volumoso:concentrado foi de 60:40 (com base na matéria seca), continha 13% de proteína bruta (PB) e 62% de nutrientes digestíveis totais (NDT). O capim-mombaça continha, em média, 7% de PB e 54% de NDT, e o suplemento 24% de PB e 76% de NDT. Foi observada diferença (P<0,05) no sistema de terminação para o ganho de peso médio diário, com 1,200kg/cab/dia para Conf e 0,675kg/cab/dia para Psu. Os novilhos Bh e Bg pesaram, em média, 445,8kg, e o rendimento da carcaça quente foi de 58,4%, valores maiores que os 399,1kg e 55,4% obtidos pelos animais He. A área de olho de Longissimus foi maior para os animais Bg, 76,42cm². A maciez, 3,71 vs 4,89, e a espessura de gordura subcutânea, 4,64 vs 3,39, foram melhores nos animais terminados em Conf do que nos animais em Psu, respectivamente.

The productive performance and carcass of the 36 Brahman (Bh), Brangus (Bg) and adapted Hereford (He) steers finished on feedlot (FD) or on rotational grazing with supplementation system (GS) were evaluated. The animals were slaughtered when the subcutaneous fat thickness was over 4mm. The feedlot diet had a forage: concentrate of 60:40 (in dry matter) 13% crude protein (CP), 62% of NDT. The mombaça gras CP level was 7% and 54% of NDT. The supplement had supplied 24% of CP and 76% of NDT. A significant difference was observed for the average daily gain, being 1,200kg/head/day for FD steers and 0.675kg/head/day for GS steers. The effect of breed on slaughter weight was observed, being 445.8kg for Bh and Bg and 399.19kg for He. The hot dressing percentage was higher for Bh and Bg than for He, 58.4% vs 55.4%. The rib eye area was higher for Bg, 76.42cm² and tenderness measured by the shear force was lower for FD steers, at 3.71 than for GS steers, at 4.89. The subcutaneous fat thickness was higher for FD steers, at 4.64 than for GS steers, at 3.39mm.