Abstract

PEREIRA, Luiz Carlos et al. Economic evaluation of puberty induction of nulliparian Nellore heifers using intravaginal device and melengestrol acetate. Acta Agron. [online]. 2019, vol.68, n.3, pp.205-212. ISSN 0120-2812.  https://doi.org/10.15446/acag.v68n3.66190.

The present study evaluates the economic viability of puberty induction in nulliparous Bos taurus indicus Nellore breed heifers using an intravaginal device of fourth-use and melengestrol acetate (MGA®). The experiment was undertaken in the Nossa Senhora Aparecida Farm, Terenos city, Mato Grosso do Sul, Brazil, and was utilized a completely randomized experimental design in a 2 x 3 factorial scheme. Two age classes were included in the study, which were divided into 348 precocious (early-cycle) heifers, aging 16-18 months, weighting an average of 264.6 kg and 543 conventional-cycle heifers aging 24-26 months averaging 346.8 kg. The three treatments were as follows: control without the induction of follicle formation (treatment 1); treatment 2: induction with an intravaginal implant (intravaginal implantation with a fourth-use progesterone implant on Day 0, withdrawal on Day 12, and application of 1 ml of intramuscular estradiol cypionate [ECP®]); and treatment 3, 2.3 g of MGA® during 12 days with supplement followed by 1 ml of intramuscular ECP® at the end of the treatment. Heifers induced via implantation had a higher rate of ovarian activity (presence of corpus luteum) during the early cycle (63.8% animals) while the conventional cycle (72.4%). This effect influenced the frequency of early stage anestrus (56%). Among the treatments evaluated, 72% of control heifers had no ovarian activity (absence of corpus luteum). In the group with implant induction the conception rates were 65.5% and 62.4% in early and conventional-cycle females, respectively. Puberty induction in Nellore heifers provides a high economic return. The protocol revealed highest efficiency compared to the control group.

Keywords : Estrus induction; fertility; reproductive efficiency; economic return; pregnancy rate.

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