Impact of breed, body score and animal category on the pregnancy rate of bovine females under IATF management

Abstract

This study evaluate the impact of the reuse of the intravaginal progesterone implant (DIP), the body condition score and the racial composition on the pregnancy rate of Nelore and Angus heifers (F1) and Nelore cows of different categories submitted to different protocols of TAI, from a database of 3,093 females submitted to the same hormonal induction protocol and from the mating season of a commercial farm in the north of Minas Gerais. The racial com- position influenced the pregnancy rate of heifers, with rates of 55.11% for Nellore heifers and 64.36% for ½ Angus, showing that the ½ Angus breed has 1.55 times more chances of successful gestation compared to the breed Nellore. There is no effect of the progesterone implant until the third use on the pregnancy rate of the heifers evaluated. The increase of one unit in the body condition score on the scale of 1 to 5 implies 1.9109 or 91.09% times more success in pregnancy. The category of calving cows did not significantly affect the pregnancy rate in the evaluated herd, with pregnancy rates of 58.1%, 62.8%, 77.7% and 62.9% for primiparous, early primiparous, secondary and multiparous, respectively. The introduction of ½ Angus heifers to explore the effects of heterosis and complementarity between breeds is a viable alternative. Cows, when well managed in the postpartum period, obtain pregnancy rates higher than that observed in the national average.