Reproductive programs for beef cattle: incorporating management and reproductive techniques for better fertility

Abstract

This review summarizes strategies to increase overall pregnancy rates to TAI protocols, and potential areas for improvement in reproductive management of Nelore cows. Low BCS at calving and postpartum BCS loss negatively impacted percentage of pregnant females to TAI, with primiparous cows being the most sensitive to the effects of low BCS during the postpartum period. The current reproductive management recommended for replacement heifers (with TAI on day 0) consist of intravaginal progesterone device insertion from day -35 to -23, 0.6 mg i.m. injection of estradiol cypionate on day -23, insertion of another intravaginal progesterone device and 2.0 mg i.m. injection of estradiol benzoate on day -11, 12.5 mg i.m. injection of dinoprost tromethamine on day -4, intravaginal progesterone device removal and 0.6 mg i.m. injection of estradiol cypionate on day -2, and TAI on day 0. Supplementing corn for 41 days after the first TAI of the breeding season increased pregnancy to a second AI in primiparous cows, increased final proportion of pregnancy in primiparous cows, but decreased the final proportion of pregnancy in mature cows. In turn, supplementing melengestrol acetate or Ca salts of PUFA during the expected time of luteolysis was beneficial to pregnancy rates. Vaccinating cows against BoHV-1, BVDV, and Leptospira spp., particularly when both doses were administered before TAI, improved cow reproductive performance. Cow temperament has direct implications not only on reproductive efficiency of B. indicus females, but also on overall production efficiency in cow-calf system based on B. indicus cattle. Lastly, concentration of pregnancy-associated glycoproteins was driven by the ability of pregnancy maintenance and by sire used at TAI, whereas exploring this relationship might be interesting to improve sire fertility regarding late embryonic loss in Nelore females.

Impacts of estrus expression and intensity during a timed-AI protocol on variables associated with fertility and pregnancy success in Bos indicus-influenced beef cows1

“…If these cows are removed from the analysis, pregnancy rates to AI remained similar (P = 0.42) between HIESTR and LWESTR cows (75.0% vs. 68.9% of pregnant cows/total cows, respectively; SEM = 5.7). Alternatively, pregnancy rates to timed-AI were already elevated in LWESTR cows based on research efforts using similar cattle and timed-AI protocol as herein (Vasconcelos et al, 2017), which could have limited the fertility benefits of high-intensity estrus. The 6% to 8% improvement in pregnancy rate to timed-AI in HIESTR cows could be considered biologically relevant, but would require at least 400 cows/estrous characteristic group (G*power 3 software; Faul et al, 2007) to yield a statistical difference (P ≤ 0.05) compared with LWESTR cows.…”

Efeito De Diferentes Métodos De Indução À Puberdade Sobre a Resposta Reprodutiva Em Novilhas Nelore

“…A puberdade ocorre quando a fêmea apresenta o primeiro estro com ovulação viável e crescimento de corpo lúteo funcional, além de manifestar todos os eventos de comportamento de cio (PERRY, 2016;SOUZA et al, 2018;ARAUJO et al, 2019).…”

Efeito De Estratégias Anti Luteolíticas Sobre a Fertilidade De Novilhas De Corte / Effect of Antiluteolytic Strategies to Improve Fertility in Heifers

“…Para que a bovinocultura de corte brasileira atinja patamares de altos níveis de eficiência, áreas como a reprodução e a genética devem ser melhoradas (Baruselli et al, 2006). Na área da reprodução, muito tem sido desenvolvido em termos de estratégias farmacológicas que possa maximizar as taxas de prenhez (Vasconcelos et al 2017).…”