Effect of three different fixed-time AI protocols on follicular dynamics and pregnancy rates in suckled, dual-purpose cows in the Ecuadorian Amazon

Abstract

El desempeño reproductivo es crucial para la rentabilidad de la producción doble propósito en la Amazonía Ecuatoriana. Evaluar tres protocolos para Inseminación Artificial a tiempo fijo (IATF) en vacas en lactancia de doble propósito. Vacas Pardo Suizo en lactancia (n=301) recibieron 2 mg de benzoato de estradiol (EB) y un dispositivo intravaginal con 0,5 g de progesterona (P4) el Día 0 y fueron asignadas aleatoriamente en tres grupos. Las vacas del grupo EB recibieron 500 µg de cloprostenol(PGF2α) y se les retiró el dispositivo el Día 7, y recibieron 1 mg de EB el Día 8. Las vacas del grupo ECP fueron tratadas como las del grupo EB, excepto que recibieron 0,5 mg de cipionato de estradiol (ECP) en el día del retiro del dispositivo (Día 7) en lugar de EB el Día 8. En las vacas del grupo J-Synch, el retiro del dispositivo y la administración de PGF2α se realizaron el Día 6. Todas las vacas fueron IATF el Día 9 y las del grupo J-Synch recibieron 100 µg de gonadorelina en ese momento. Aunque el diámetro del folículo dominante y del CL fueron mayores (P<0,05) en las vacas del grupo J-Synch, las tasas de preñez a la IATF no difirieron entre los grupos (EB: 51,0%, ECP: 53,0% y J-Synch: 59,4%). Los tres protocolos probados se pueden aplicar con éxito en vacas de doble propósito amamantando.Reproductive performance is crucial for profitability of dual-purpose cow-calf production in the Ecuadorian Amazon. To evaluate three different fixed-time artificial insemination (FTAI) protocols in suckled, dual-purpose cows in the Ecuadorian Amazon. Lactating, Brown Swiss cows (n=301) received 2 mg estradiol benzoate (EB) and an intravaginal device containing 0.5 g of progesterone (P4) on Day 0. They were allocated randomly into the following three treatment groups: Cows in the EB group received 500 μg cloprostenol (PGF2α), and P4 devices were removed on Day 7, and 1 mg EB was administered on Day 8. Cows in the ECP group were treated as those in the EB group, except that they received 0.5 mg estradiol cypionate (ECP) at the time of P4 device removal on Day 7 instead of EB on Day 8. Cows in the J-Synch group had the P4 device removed and PGF2α administered on Day 6. All cows were FTAI on Day 9; cows in the J-Synch group also received 100 μg gonadorelin at that time. Although the diameter of the dominant follicle and the resulting CL were greater (P<0.05) in cows in the J-Synch group, pregnancies per AI did not differ (P>0.2) among groups (EB: 51.0%, ECP: 53.0% and J-Synch: 59.4%). The three protocols tested were applied successfully in suckled, dual-purpose cows with no differences in pregnancies per AI.