Use of injectable P4 associated with an intravaginal P4 device for early resynchronization of beef cattle submitted to three TAIs in 48 days

• Autor(a) principal: Júnior, Gilmar Arantes Ataide
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/10/10131/tde-20012021-140737/
• topic: Body condition score; Doppler ultrasonography; Eficiência reprodutiva; Escore de condição corporal; Progesterona de curta ação; Reproductive efficiency; Ressincronização; Resynchronization; Short-acting progesterone; Ultrassonografia Doppler

We aimed to evaluate the follicular dynamic and pregnancy rate (P/AI) of beef cattle submitted to resynchronization 13 days after a TAI using a P4 device associated or not with short-acting injectable progesterone (iP4). In Exp. 1, 28 Nelore suckled cows and 25 heifers were submitted to an ovulation synchronization protocol (Day 0 = expected estrus). On Day 13, animals were split into two treatments, namely control (only P4 device; 15 cows and 13 heifers) and iP4 (P4 device + 100 mg iP4; 13 cows and 12 heifers), and submitted to daily ovarian ultrasonography (US) exams and blood collection, from Day 13 to Day 22. On Day 22, the P4 devices were removed, and animals with detected luteolysis by the US had the ovulation induced by E2 cypionate treatment. In Exp. 2, 760 cows and 498 heifers were submitted to a 1ª TAI on Day 0. On Day 13 and Day 22, animals were split into control and iP4 treatments and submitted to the same procedures done in Exp. 1. Also, non-pregnant animals received the 2ª TAI on Day 24, and on Day 37 were resynchronized using the opposite treatments 1ª resynchronization procedure. On Day 37, a pregnancy diagnosis was performed in animals with an active CL on Day 22. Those with potential pregnancy loss between Day 22 and Day 37 were also resynchronized on Day 37. The 3ª TAI was performed on Day 48. The confirmatory PD of the 2ª and 3ª TAIs were performed on Days 61 and D85, respectively. In Exp. 1, the time and synchrony of follicular wave emergence did not differ between treatments and parity. The dominant follicle was larger in cows than in heifers on Day 22 and Day 24, and in the control treatment on Day 24 (P<0.05). Increased P4 concentrations were detected on Day 14 (P<0.05) and Day 15 (P=0.08) in the iP4 treatment. P4 concentrations reduced gradually between Day 14 and Day 22 (P<0.05), and luteolysis occurred earlier (P=0.07) in cows than in heifers. In Exp. 2, the overall P/AI for 2ª and 3ª TAIs, regardless of parity, was greater (P<0.05) in the iP4 than the controls (43% [178/411] vs. 38% [148/387]). The P/AI tended to be greater (P=0.09) in iP4-treated heifers than control heifers (44% [73/167] vs. 38% [61/160]), but did not differ between iP4-treated cows (43% [105/244]) and control cows (38% [87/227]). In conclusion, the 100 mg short-acting iP4 treatment associated with the intravaginal P4 device is effective in increasing the plasma P4 concentration, but does not impact the synchrony of the follicular wave emergence. Animals treated with iP4 presented improved P/AI.