Desempenho reprodutivo de fêmeas bovinas submetidas a IATF

Abstract

Hormonal protocols are fundamental for the success of current reproductive programs, since they manage to leverage productive rates to better levels of economic return to the producer. Studying and understanding how the variables inherent to the animal alter the result of the protocols allows for ever better results in the field. The body condition score has been studied as one of the main variables related to the pregnancy rate. The objective of this study was to evaluate the performance of bovine females submitted to a TAI protocol. The study was carried out through the analysis of productive data from three beef cattle properties, of Zebu breed pattern, located in the Southwest of Paraná. Females were divided into categories: heifer, primiparous and multiparous; and also classes: lactating and non-lactating; being submitted to the same hormonal protocol, which consisted of implantation of 1.0 g of progesterone on D0, together with 2.0 mg of estradiol benzoate; on D8, 0.5 mg of sodium cloprostenol, 1.0 mg of estradiol cypionate and 300 IU of equine chorionic gonadotropin were administered; and on D10, insemination was performed, with the application of 2.5 mL of a GnRH analogue in animals that did not show acceptance of mating. There was difference in average weight between categories, with weights 294.9; 340.1 and 365.9 kg, respectively for heifers, primiparous and multiparous. The pregnancy rate was similar between categories, being 45.0%, 41.3% and 50.3% for heifers, primiparous and multiparous. respectively. Separating females into lactating or non-lactating, the body condition score and pregnancy rate were similar, 2.81 and 3.16 points, respectively, and 48.9% and 46.6% for pregnancy rate, cited in same order. The use of GnRH in animals that did not show signs of estrus was necessary in 22.1%, 19.1% and 18.4% of heifers, primiparous and multiparous respectively, with a pregnancy rate of 34.8%, 32.3% and 43.3% for the same categories. As for the classes of bovine females, the pregnancy rate was 32.3% for non-lactating cows and 38.6% for lactating cows. The use of GnRH occurred in 15.3% of the cows without the presence of the calf and in 20.7% of the cows that were lactating. The use of TAI did not change the reproductive performance of bovine females of different categories, although adult cows had higher body weight. Cows without the presence of the calf have better body condition, but do not show improvement in reproductive rates compared to lactating cows. The category of bovine females or the occurrence of lactation do not change the frequency of GnRH use as well as the reproductive rates of females submitted to the TAI protocol.