Effects of long‐acting injectable progesterone supplementation at early dioestrus on pregnancy maintenance in beef and dairy recipient cattle

Abstract

We tested in the present study the hypothesis that supplementation with long‐acting P4 (iP4) at different times of the initial dioestrus improves pregnancy rates in dairy and beef recipients submitted to fixed‐time embryo transfer (FTET). Recipients from commercial farms had their oestrous cycle synchronized with an E2/P4‐based protocol in three experiments (Exp. 1 to 3). In Exp. 1, dairy heifers (n = 76) and cows (n = 104) were randomly assigned to two experimental groups: the control group (n = 89) and the iP4D4 group (n = 91). For Exps. 2 and 3, suckled beef recipients were used. In Exp. 2, recipients were assigned to two experimental groups: Control group (n = 147) and iP4D7 group (n = 144); whereas in Exp. 3, recipients were randomly assigned to three experimental groups: Control group (n = 85), iP4‐D4 group (n = 86) and iP4D7 group (n = 81). Recipients in the iP4D4 and iP4‐D7 groups received an i.m. administration of 150 mg iP4, on D4 or D7 (D0 was the day of expected oestrus). On D7, all recipients were evaluated by transrectal ultrasonography and those that had a CL received a fresh or vitrified in vitro‐produced embryo. In Exp. 2 and 3, the CL area was also determined by ultrasonography at the time of FTET. The pregnancy diagnosis was performed at 30 days in Exp. 1, 57 days in Exp. 2, and between 40 and 72 days of pregnancy in Exp. 3. In Exp. 1, the pregnancy rate did not differ (p > .1) between the Control group (38.2% [34/89]) and iP4D4 group (49.5% [45/91]); yet, a parity effect indicated a greater (p < .05) pregnancy rate in heifers (57.9% [44/76]) than cows (30.8% [32/104]). In Exp. 2, the pregnancy rate was greater (p < .05) in the iP4D7 group (45.0% [65/144]) than in the Control group (34.0% [50/147]). Also, a greater (p = .08) pregnancy rate was observed for recipients with a small CL (≤2.75 cm2) that were treated with iP4 on the day of FTET than the control recipients (46.4% [32/69] vs. 32.6% [28/86]). In Exp. 3, no significant effects (p > .1) of the treatment group or CL size were detected on pregnancy rates at days 30 and 60. In conclusion, the beneficial effects of iP4 supplementation at early dioestrus on pregnancy maintenance may vary according to the experimental conditions, but its use at the time of FTET can be used as an alternative to enhance the fertility of beef recipients in challenging conditions in commercial herds.

Use of long-acting injectable progesterone in fixed-time artificial insemination protocols

“…Esta técnica descarta a necessidade da observação de cio, otimizando assim a mão de obra, pois as inseminações serão programadas e realizadas por lote o que resulta em uma padronização do rebanho e consequentemente a obtenção de lotes de bezerros uniformes. Uma das principais vantagens do emprego da IATF é de induzir a ciclicidade em vacas que se apresentam em anestro, obtendo ganhos na taxa de concepção do rebanho (Laurindo Neto et al, 2024;Pugliesi et al, 2013Pugliesi et al, , 2019.…”

“…A criação e utilização de implantes intravaginais representaram um avanço significativo na administração controlada de P4 por um período determinado. Isso permitiu a retirada do dispositivo e, consequentemente, uma diminuição estratégica dos níveis de progesterona o que torna possível induzir a ovulação com o uso de estradiol após a remoção dos implantes Laurindo Neto et al, 2024;Loiola et al, 2018). Embora o implante de P4 apresente inúmeras vantagens também devemos nos atentar a alguns fatores, sendo eles, a probabilidade de transmissão de doenças como vaginite, endometrite, Rinotraqueite Infecciosa Bovina (IBR) e Diarreia Viral Bovina (BVD), causando vários danos econômicos (Loiola et al, 2018).…”