Pregnancy rate in lactating Bos indicus cows subjected to fixed-time artificial insemination and treated with different follicular growth inducers

Abstract

-The objective of this experiment was to evaluate the effects of replacing eCG with FSH or FSH/LH on the diameter of ovulatory follicles (DOF) and the pregnancy rates (PR) of lactating Bos indicus cows subjected to a synchronization of ovulation protocol and fixed-time artificial insemination (FTAI) based on progesterone, estradiol benzoate (EB), PGF2α, and estradiol cypionate (EC). On day 0, primiparous and multiparous Nellore cows (n = 329) at 68 days postpartum were body condition scored (BCS) and received a P4 implant (PRIMER 1.0 g P4) plus 2 mg EB intramuscularly (IM). At day 8, the implant was removed, and 250 μg cloprostenol were injected IM along with 0.5 mg EC. At the time of implant removal, the animals were divided into one of four treatments: cows received (G1) 1 mL of saline solution IM (Control; n = 80); (G2) 300 IU eCG IM (ECG300; n = 84); (G3) 15 mg FSH IM (Folltropin; n = 82); and (G4) 30 IU FSH/LH IM (Pluset; n = 83); all cows were subjected to FTAI 48-54 h after implant removal (day 10). Transrectal ultrasonography was performed to measure the DOF to FTAI and to estimate the pregnancy rate on day 35. A statistical analysis examined the effects of the treatment, technician, semen, BCS, calf age and parity on PR to FTAI. There was no significant difference in PR and DOF among the treatment groups (G1, 41.3%, 13.1 mm; G2, 46.4%, 14.5 mm; G3, 46.3%, 14.2 mm; and G4, 48.2%, 14.3 mm), but PR was higher in multiparous than in primiparous cows. Commercial FSH solutions (Pluset or Folltropin) do not promote increases in PR or DOF of lactating Nellore cows and are equal to eCG in promoting growth in preovulatory follicles and elevating the PR in Nellore cows with a moderate BCS subjected to a progesterone-based FTAI protocol with EC.

Effect of equine chorionic gonadotropin on pregnancy rate in Brown Swiss cows under high altitude conditions

“…Definitely, there is enough evidence in the literature that the inclusion of eCG in an FTAI does not improve the fertility rate in cattle with a good BCS. Binelli et al (2009) mentioned that the eCG effectiveness varies with the BCS and Nogueira et al (2014) observed that the BCS had a positive effect on the probability of pregnancy using eCG in an FTAI. Ferreira et al (2013) indicated that the differences observed in the inclusion of eCG in FTAI might be explained by the corresponding inequalities in BCS.…”

“…Equine Chorionic Gonadotrophin (eCG) has been used in procedures of fixed-time artificial insemination (FTAI) in cattle to try to improve the fertility rate because it produces, among other effects, an increase of follicular growth (Murphy 2012;Núñez-Olivera et al 2014). The application of 400 IU of eCG has shown that it can be a good treatment to increase fertility, especially in beef breeds (Menchaca et al 2013;Nogueira et al 2014); nevertheless, in dairy cattle results have been contradictory (Pulley et al 2013).…”

Effect of follicular growth promoters on timed artificial insemination in dairy cows.

“…Los resultados encontrados en el presente estudio corroboran los datos encontrados por otros autores (15), quienes, trabajando con vacas Nelore, no encontraron diferencias en las tasas de preñez al usar eCG como promotor del crecimiento folicular (46.4%) o FSH (46.3%) comparado al control (41,2%). Por otro lado, algunos autores, comparando el uso de eCG y FSH en vacas Cebú, encontraron tasas de preñez de 55.9 y 51.4% respectivamente, que diferían significativamente de las vacas control, con una tasa de preñez de 38.9% (8).…”

“…Se ha informado que eCG es superior a FSH para estimular las tasas de preñez en vacas; sin embargo, otros autores informaron que no hubo diferencias en el uso de FSH y eCG en vacas sometidas a IATF (7,22). Dichos autores también informaron que el eCG tiene un efecto en la FSH y en la LH, y tiene una vida media más larga, permaneciendo activo en la sangre durante más tiempo, de cinco a siete días después de su administración (15). La FSH utilizada en el presente estudio, por otro lado, contenía el 87% de FSH, y su metabolismo parece ser rápido, ya que, después de la administración intramuscular, la vida media y la desaparición de la FSH se estimaron en 5 y 12 minutos, respectivamente (23,24).…”

<b>Impacto da qualidade espermática sobre a fertilidade <i>in vivo</i> em bovinos:</b> contribuição de marcadores mitocondriais e subpopulações espermáticas

“…Alguns autores demonstraram que o sêmen utilizado na IATF tem um grande impacto sobre a TP (CORREA; PACE; ZAVOS, 1997;ANDERSSON et al, 2004;SÁ FILHO et al, 2009;OLIVEIRA et al, 2013OLIVEIRA et al, , 2014NOGUEIRA et al, 2014). A diminuição da fertilidade é uma condição multifatorial, portanto, muito difícil de diagnosticar.…”