The effect of equine chorionic gonadotropin on follicular size, luteal volume, circulating progesterone concentrations, and pregnancy rates in anestrous beef cows treated with a novel fixed-time artificial insemination protocol

Abstract

The objective was to determine the effects of eCG given on the day of, or 2 days before removal of an intravaginal progestin device, on ovarian follicle diameter, luteal volume, serum progesterone (P4) concentrations, and pregnancy per insemination in a fixed-time AI (FTAI) protocol. Lactating, anestrous, multiparous Bos taurus cross beef cows, 40 to 60 days postpartum, were given estradiol benzoate (2 mg im) and a progestin intravaginal device containing 250 mg of medroxyprogesterone acetate on Day 0 and cloprostenol (0.265 mg) on Day 6. Intravaginal devices were removed on Day 8 and GnRH (100 μg im) was given on Day 9, with timed AI 16 hours later. In experiment 1, cows were randomly assigned to receive 400 IU im eCG on Day 6 (eCG6; N = 8) or Day 8 (eCG8; N = 8), or to not receive eCG (control; N = 8). Dominant follicle diameter on Day 9 in the eCG6 group (10.0 ± 0.5 mm) was larger (P < 0.05) than in the eCG8 (8.6 ± 0.2 mm) or control (8.5 ± 0.4 mm) groups. Corpora lutea (CL) in all cows in the control group underwent premature luteolysis within 10 days after ovulation. Luteal volumes and P4 concentrations 10 and 15 days after ovulation were higher (P < 0.05) in the eCG6 group than in the eCG8 group. In experiment 2, the eCG6 (N = 121) and eCG8 (N = 125) protocols were compared in lactating anestrous cows that underwent FTAI. Pregnancy rate was higher (P < 0.05) in the cows that received eCG on Day 6 (27.3%; 33/121) than on Day 8 (16.0%; 20/125). Furthermore, CL volumes and P4 concentrations were higher (P < 0.05) in the eCG6 group (5784.0 ± 857.3 mm(3) and 8.1 ± 1.3 ng/mL, respectively) than in the eCG8 group (3220.9 ± 505.1 mm(3) and 4.5 ± 0.7 ng/mL, respectively). We concluded that eCG given 2 days before progestin removal in this FTAI protocol for anestrous beef cows increased diameter of the dominant follicle, luteal volume, serum P4 concentrations, and pregnancy rates.

Application of low dose of equine chorionic gonadotropin at acupoint Hou Hai for fixed-time artificial insemination in beef cows

“…The most recent studies have indicated that eCG can effectively stimulate follicle growth, ovulation, and luteinization mediated by the increased availability of LH (MURPHY, 2012;TORRES-JÚNIOR et al, 2016). Which, consequently, may result in acceptable pregnancy rates after FTAI in cows (SALES et al, 2011), as well as in heifers (SÁ FILHO et al, 2010b) treated with 400 IU in P 4 device removal, which was also observed in present study, even using eCG dose much lower than that studied by Sá Filho et al (2010b).…”

Resynchronization of ovulation with new and reused intravaginal progesterone‐releasing devices without previous pregnancy diagnosis in Bos taurus indicus cows subjected to timed‐artificial insemination

“…Oliveira et al (2016) demonstrated that Bos taurus indicus cows with POF dimensions >11.0 mm resulted in higher P/AI than in the cows carrying follicles smaller than 11.0 mm. Therefore, POFs with bigger dimensions might generate larger corpora lutea and consequently lead to higher production of progesterone, which is essential to pregnancy maintenance in cattle (Tortorella et al, 2013). We observed that the diameter of the POF in the resynchronization phase was larger in the pregnant cows (Ø13.2 mm [GRN, GRU]; Figure 3) than in the non-pregnant cows (Ø12.6 [GRN; p = 0.06]; Ø11.3 [GRU; p = 0.003]), consistent with the reports of Oliveira et al (2016).…”

Equine chorionic gonadotropin drives the transcriptional profile of immature cumulus‐oocyte complexes and in vitro‐produced blastocysts of superstimulated Nelore cows

“…Several protocols using FSH (Barros & Nogueira, ; Barros & Nogueira, ; Baruselli et al, ; Coelho, Esper, Alvarez, Vantini, & Junior, ; Dias, Costa et al, ; Dias, Khan, Sirard, Adams, & Singh, ; Mundim et al, ) or eCG (Baruselli, Reis, Marques, Nasser, & Bo, ; Duffy et al, ; Fatima et al, ; O'Hara et al, ; Pessoa et al, ; Scanlon et al, ; Small, Colazo, Kastelic, & Mapletoft, ; Sousa, Mendes, Campos, Baruselli, & Papa, ) are being tested individually or in combination by replacing the last two FSH doses by eCG (Barcelos et al, ; Barcelos, Satrapa, Nogueira & Barros, ; A. C. Oliveira et al, ). The main benefits of eCG use are an increase in the occurrence of estrus, pregnancy rates (Pessoa et al, ) follicular size, corpus luteum volume, and circulating progesterone concentrations in beef cows and heifers (Dorneles Tortorella et al, ; O'Hara et al, ). Moreover, the increased proportion of larger follicles that contained oocytes showed a greater rate of fertilization and a lower rate of polyspermy (Ribas et al, ).…”

“…C. Oliveira et al, 2011). The main benefits of eCG use are an increase in the occurrence of estrus, pregnancy rates (Pessoa et al, 2016) follicular size, corpus luteum volume, and circulating progesterone concentrations in beef cows and heifers (Dorneles Tortorella et al, 2013;O'Hara et al, 2016). Moreover, the increased proportion of larger follicles that contained oocytes showed a greater rate of fertilization and a lower rate of polyspermy (Ribas et al, 2018).…”