Puberty attainment and reproductive performance of yearling Bos indicus-influenced heifers after two sequential treatments with progesterone

Hormonal adjustments for fixed-time artificial insemination and physiologic variables influence in the reproductive performance of >i<Bos indicus>/i< heifers

“…The aim of this study was to evaluate the effects of different hormonal adjustments in TAI protocols in physiologic response and reproductive performance of 13 to 17 months old Nelore heifers besides of the impact of some heifer's characteristics that could be relevant in the success of the young heifers breeding programs. There are studies establishing the well none benefits of the presence of CL before any hormonal treatment (considered as pubertal), one of those benefits reported is the higher expression of estrus of pubertal heifers when compared with those that did not have CL presence (considered as prepubertal) (Pubertal: 68.1% vs. prepubertal: 39.5%) leading to a better P/AI in heifers (Pubertal: 46.6% vs. prepubertal: 30.0%) [35], results partially supported for this study, having a higher LF diameter on D -2 and on D0 within the heifers group with CL on Day -9, having no influence on the expression of estrus as described above, nonetheless there was a relevant difference of 11.9% points for P/IA on Day 60 for heifers with CL presence at the P4 implant insertion, considering the CL presence could be considered as a puberty indicator of heifers, indicating a better reproductive status and functionality of the hypothalamuspituitarygonadal axis [22,36], also heifers with CL on Day -9, tended to present a reduced pregnancy loss, possibly due to the better embryo quality of the cycling heifers [37] or a previous exposition to high levels of endogenous or pharmacologic estradiol concentration, derived from the first TAI protocol that the heifers received, influencing the uterine tissues, having a possible positive impact on the uterine environment [38].…”

>b<Monitoramento da ciclicidade de novilhas Nelore submetidas a protocolos hormonais com progesterona aos 14 meses de idade>/b<

“…Além disso, o grupo 0P4 demonstra que a diferença energética da dieta do período 1 para o período 2 não foi suficiente para influenciar no desenvolvimento folicular.O plano nutricional do primeiro período do estudo foi proposto para que as novilhas atingissem o PC em que comumente é observado a puberdade em novilhas Nelore (DAY; NOGUEIRA, 2013). Além disso, novilhas mais pesadas tem melhor resposta ovulatória a protocolos hormonais(MARTINS et al, 2021), o que favoreceu a alta taxa de ovulação aos protocolos hormonais. As novilhas foram submetidas à elevado GMD fazendo com que acumulassem gordura subcutânea.…”