Resposta reprodutiva de vacas de corte associada a marcadores moleculares relacionados à fertilidade

Abstract

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.