Embryo Survival from Gossypol-Fed Heifers after Transfer to Lactating Cows Treated with Human Chorionic Gonadotropin

Abstract

Objectives were to determine the effects of gossypol exposure during early embryo development on embryonic survival after transfer of frozen and thawed embryos to lactating dairy cows treated with human chorionic gonadotropin (hCG). Holstein cows (n = 269) were either treated or not treated with 3,300 IU of hCG on d 5 of the estrous cycle and received an embryo collected from heifers fed or not fed gossypol. Embryo donor heifers consumed either 0 or 12 g/d of free gossypol for 76 d prior to embryo collection, resulting in mean plasma gossypol concentrations of 0 and 7.38 microg/mL, respectively. Embryos were transferred on d 7 of the estrous cycle and pregnancy diagnosed 21 and 35 d later. Progesterone was analyzed in plasma collected on d 5 and 12 of the estrous cycle. Treatment with hCG increased the total luteal area on d 12 (818.0 vs. 461.1 mm2) because of increased number of corpora lutea (2.0 vs. 1.0) and increased area of the original corpora lutea (522.7 vs. 443.5 mm2). Plasma progesterone concentrations were similar between treatments on d 5, but increased by d 12 in hCG-treated cows (6.46 vs. 4.78 ng/ mL). Pregnancy rates on d 28 and 42 were not affected by hCG. However, after transfer into lactating cows, embryos collected from heifers not fed gossypol resulted in higher pregnancy rates at 28 d (33.3 vs. 23.1%) and 42 d (29.6 vs. 20.2%) of gestation compared with embryos collected from heifers fed gossypol. Our data suggest that the negative effects of gossypol on fertility are mediated by changes in embryo viability in spite of similar grade quality at transfer.

Characteristics and retention of luteal structures, extended postinsemination cycle, progesterone, and pregnancy-specific protein B in serum after human chorionic gonadotropin treatment of dairy cows

“…Concentrations of progesterone were elevated by hCG and pregnancy status compared with saline controls and lack of pregnancy in the present study, respectively, corroborating similar reports in lactating dairy cows Galvão et al, 2006;Stevenson et al, 2007) and in dairy heifers (Schmitt et al, 1996a). Although we did not detect increased progesterone in cows in which hCG failed to produce new luteal structures, previous studies reported that progesterone secretion by original CL was enhanced (Stevenson et al, 2007).…”

“…Frequency of hCG-induced luteal structures in the present study was consistent with the findings of the latter 2 studies. Incidence of ≥2 new luteal structures in our study (17.2%) was independent of the number of pretreatment CL and pregnancy status but was slightly less than that reported in other lactating dairy cows (24.8%; Galvão et al, 2006). Although the level of milk production was not associated with ovulatory response to hCG , cows enrolled in the present study averaged more than 46 kg of ECM per day, and those producing greater than 46 kg of ECM were less likely to form new luteal structures after to hCG.…”

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

“…Chagas e Silva and Lopes da Costa (2005) reported no effect of hCG treatment on d 7 on P/ET in dairy heifers; however, pregnancy loss was not reported in that study. In addition, treatment with hCG 5 d after ovulation did not affect P/ET for lactating Holstein cows receiving ET 7 d after induction of ovulation (Galvão et al, 2006). In mature beef cows, treatment with hCG at ET 7 d after ovulation increased P/ET, but no difference was noted in pregnancy loss (Wallace et al, 2011).…”

Gossypol as undesirable substance in animal feed - Scientific Opinion of the Panel on Contaminants in the Food Chain

“…The embryo diameter was significantly and dose dependently reduced. These effects of gossypol were also observed in dairy cows receiving embryos from heifers fed gossypol (Galvao et al, 2006), which suggests that negative effects in early embryo development persist during maintenance of pregnancy.…”