Efeito da indução de puberdade em novilhas de corte sobre a taxa de gestação ao final da estação de monta

Abstract

The brazilian beef cattle breeding has consolidated itself in the world ranking of production and export of beef, having then great economic relevance. However, extensive breeding and low technological investment compromise zootechnical rates, thus requiring innovations in animal breeding and genetic improvement to increase productivity. The profitability of the breeding activity is based on the calving of one calf per cow per year, so it is crucial that the female becomes pregnant early. Therefore, the age at which the first conception occurs is crucial to productivity and the age at puberty is the main factor that establishes the competence of the female in her first breeding season. To optimize reproductive results of heifers, it is suggested to perform puberty induction, which consists in the use of pharmacological protocols with the purpose of inducing cyclicity of females, so that they are cyclic at the beginning of the reproductive season and possibly conceive. In this study, data were collected regarding the induction of puberty of 86 Nelore heifers, with an average age of 14 months, belonging to the herd of a beef cattle ranch located in the state of Goiás. The injectable progesterone (1.0 ml, Sincrogest®, Ouro Fino) was the drug used as puberty inducing agent, with subsequent execution of ovulation synchronization protocol for fixed-time artificial insemination (FTAI). In D0 the females were implanted with an intravaginal progesterone device (CIDR®, Zoetis) of slow release (3rd use), in association with the intramuscular administration of estradiol benzoate (2.0 ml, Gonadiol®, Zoetis). After 7 days (D7), heifers received an intramuscular injection of prostaglandin (2.5 ml, Lutalyse®, Zoetis). At D9, the intravaginal progesterone devices were removed, along with intramuscular administration of prostaglandin (2.5 ml, Lutalyse®, Zoetis), estradiol cypionate (0.3 ml, ECP®, Zoetis) and equine chorionic gonadotropin (1.5 ml, Novormon®, Zoetis). Fixed-time artificial insemination (FTAI) occurred on D11. From the total of females, 60 animals became cyclic (69.8%) and 59 animals became pregnant, causing a gestation rate at the end of the breeding season of 68.6% with 3 FTAIs. As an aid to the induction of puberty, the transrectal ultrasonography allowed the evaluation of the effectiveness of the protocol and responsiveness of the female. It is concluded that the induction of puberty influenced the reproductive efficiency of the herd.