Secondary Corpora Lutea Induced by hCG Treatment Enhanced Demi‐Embryo Survival in Lactating High‐Yielding Dairy Cows

Abstract

Using a novel in vivo model considering a low developmental competence embryo (demi-embryo) and a subnormal fertility recipient (lactating high-yielding dairy cow), this experiment evaluated the effect of human chorionic gonadotrophin (hCG) treatment at embryo transfer (ET) on embryonic size at implantation, embryonic survival and recipient plasma progesterone (P4 ) and bovine pregnancy-specific protein B (PSPB) concentrations until day 63 of pregnancy. Embryos were bisected and each pair of demi-embryos was bilaterally transferred to recipients (n = 61) on day 7 of the oestrous cycle. At ET recipients were randomly assigned to treatment with 1500 IU hCG or to untreated controls. Higher (p < 0.01) pregnancy rates on days 25, 42 and 63, and embryo survival rate on day 63 were observed in hCG-treated cows with secondary CL than in hCG-treated cows without secondary CL and in untreated cows. Pregnancy rates and embryo survival rate were similar in hCG-treated cows without secondary CL and untreated cows. Embryonic size on day 42 was not affected by treatment with hCG, presence of secondary CL and type of pregnancy (single vs twin). Presence of secondary CL increased (p < 0.05) plasma P4 concentrations of pregnant cows on days 14, 19 and 25 but not thereafter and of non-pregnant cows on days 14-21. Treatment with hCG and presence of secondary CL had no effect on plasma PSPB concentrations, which were higher (p < 0.05) in twin than in single pregnancies. In conclusion, secondary CL induced by hCG treatment at ET significantly increased plasma P4 concentrations, the survival rate of demi-embryos and the pregnancy rate of high-yielding lactating dairy cows. Embryos were rescued beyond maternal recognition of pregnancy, but later embryonic survival, growth until implantation and placental PSPB secretion until day 63 of pregnancy were not affected by treatment or presence of secondary CL.

Effect of equine chorionic gonadotropin treatment during a progesterone-based timed artificial insemination program on reproductive performance in seasonal-calving lactating dairy cows

“…A variety of strategies can be used to increase peripheral P4 concentrations. These can be broadly classified as strategies that stimulate increased endogenous P4 production or strategies that rely on administration of exogenous P4 and include (1) manipulation of follicular development to increase the size of the preovulatory follicle and hence the size of the subsequent CL (Baruselli et al, 2012;Mesquita et al, 2014;Ramos et al, 2015); (2) direct stimulation of CL development with luteotropic agents (Maillo et al, 2014;Sánchez et al, 2018); (3) induction of accessory CL using appropriately timed administration of GnRH or human chorionic gonadotropin (Santos et al, 2001;Stevenson et al, 2007;De Rensis et al, 2010;Torres et al, 2013). Exogenous P4 supplementation has been achieved through injections (Garrett et al, 1988;Geisert et al, 1991;Pugliesi et al, 2014) or P4-containing devices (Stevenson et al, 2007;Carter et al, 2008;O'Hara et al, 2014O'Hara et al, , 2016.…”

Effect of treatment with human chorionic gonadotropin 7 days after artificial insemination or at the time of embryo transfer on reproductive outcomes in nulliparous Holstein heifers

“…To date, many studies have tested the effect of treatment with hCG after AI on pregnancies per AI (P/AI) or pregnancy loss with mixed results. In cows, treatment with hCG on d 5 (Schmitt et al, 1996;Santos et al, 2001;Nascimento et al, 2013), 7 (Sianangama and Rajamahendran, 1992;Dahlen et al, 2010;Wallace et al, 2011;Torres et al, 2013a), and 14 (Sianangama and Rajamahendran, 1992) increased P4 concentrations; however, effects on pregnancy outcomes and pregnancy loss varied. Pregnancy outcomes for heifers treated with hCG have varied even more; P/ AI increased after treatment with hCG on d 4 (Breuel et al, 1989) and 7 (Chagas e Silva and Lopes da Costa, 2005;Torres et al, 2013b), whereas no difference was reported in other studies when beef heifers were treated with hCG on d 4 (Breuel et al, 1990), 5 (Funston et al, 2005), or 6 (Funston et al, 2005).…”

The ovulatory response to human chorionic gonadotropin administration on day 4 post timed artificial insemination improved fertility in repeat breeder cows

“…The success of inducing endogenous progesterone source which is determined by ovulatory response to post-TAI administration of hCG on days 5-7 is accepted as adequate, with response rates of 60 to 100% in lactating dairy cows (Santos et al 2001;Nascimento et al 2013;Torres et al 2013), but the response to hCG on day 4 post TAI has not yet been documented. In the present study, the response to hCG administration on hCG4 and hCG5 included repeat breeder cows treated with hCG administration on day 4 or 5 post TAI, respectively.…”