Effect of human chorionic gonadotropin on luteal function and reproductive performance of high-producing lactating Holstein dairy cows.

Abstract

The objectives were to evaluate effects of human chorionic gonadotropin (hCG) (3,300 IU i.m.) administered on d 5 after AI on CL number, plasma progesterone concentration, conception rate, and pregnancy loss in high-producing dairy cows. Following the synchronization of estrus and AI, 406 cows were injected with either hCG or saline on d 5 after AI in a randomized complete block design. Blood sampling and ovarian ultrasonography were conducted once between d 11 and 16 after AI. Pregnancy diagnoses were performed on d 28 by ultrasonography and on d 45 and 90 after AI by rectal palpation. Treatment with hCG on d 5 resulted in 86.2% of the cows with more than one CL compared with 23.2% in controls. Plasma progesterone concentrations were increased by 5.0 ng/mL in hCG-treated cows. The presence of more than one CL increased progesterone concentration in hCG-treated cows but not in controls. Conception rates were higher for hCG-treated cows on d 28 (45.8 > 38.7%), 45 (40.4 > 36.3%), and 90 (38.4 > 31.9%) after AI. Treatment with hCG improved conception rate in cows losing body condition between AI and d 28 after Al. Pregnancy losses were similar between treatment groups. Treatment with hCG on d 5 after AI induces accessory CL, enhances plasma progesterone concentration, and improves conception rate of high-producing dairy cows.

Physiological and practical effects of progesterone on reproduction in dairy cattle

“…When hCG or GnRH is administered on day 5 after AI, there is generally formation of an accessory CL and increased P4 during the mid-luteal phase (Fricke et al, 1993;Santos et al, 2001). In our recent study we found that 93% of dairy cows treated with hCG on day 5 had ovulation .…”

“…However, circulating P4 remained lower, even after hCG treatment, in lactating cows compared with normally ovulating heifers. Eight studies that evaluated the effect of hCG on P4 concentrations from days 4 to 7 after AI in lactating dairy cows reported significant increases in circulating P4 concentrations after treatments with different doses of hCG: 3300 IU (Schmitt et al, 1996;Santos et al, 2001), 2500 IU (Stevenson et al, 2007b;Vasconcelos et al, 2011); 1500 IU (Walton et al, 1990;Hanlon et al, 2005; Kendall et al, 2009) or 1000 IU (Rajamahendran and Sianangama, 1992). Thus, treatment with hCG on day 5 after AI produces a consistent, fairly rapid (3 days delay) increase in circulating P4 in lactating dairy cows.…”

Exogenous hormonal manipulation to increase reproductive efficiency in dairy cows

“…Although other studies (WILTBANK et al, 1956;JOHNSON et al, 1958;SANTOS et al, 2001;LARSON et al, 2007) have shown benefits of supplemental P4 after AI, in the present study, no effect was observed on the fertility of dairy cows. In fact, an interaction and a tendency for interaction between supplementation of P4 and parity was observed on the P/AI at d 32 and pregnancy loss, respectively.…”

“…Supplemental P4 has been used before and after AI (WILTBANK et al, 1956;ROSS;FOURT, 1958;LARSON;BUTLER;CURRIE, 2007;MONTEIRO et al, 2014) either by the use of intravaginal P4 implants (WILTBANK et al, 1956;JOHNSON et al, 1958;LARSON et al, 2007;MONTEIRO et al, 2014) or by induction of accessory corpus luteum (CL) (SANTOS et al, 2001;NASCIMENTO et al, 2013). This strategy has been associated with increased pregnancy/AI (P/AI).…”

Consequences of eight consecutive applications of equine chorionic gonadotropin on ovarian follicle development and ovulation in bos indicus cows

“…Even though it was not observed an increase in preovulatory follicle size it was observed a larger Cl. an increase in progesterone concentration has also been described as a positive effect of the eCG (SaNtOS et al, 2001;BaRUSEllI et al, 2004;MaRQUEZINI et al, 2014). the eCG acts increasing the number of lutheal cells and mitochondrias that in turn increases pregnenolone synthesis (RIGOGlIO et al, 2013).…”