Effects of administration of human chorionic gonadotropin or progesterone before maternal recognition of pregnancy on blastocyst development and pregnancy in sheep. Academic Article uri icon


  • A series of four experiments with 258 ewes was conducted to determine whether blastocyst size could be altered before normal luteolysis and, if so, how this affected fertility. In Exp. 1 and 2, nonmated and mated ewes, respectively, were treated with hCG (100 IU), progesterone (12 mg), or vehicle on d 11.5 (d 0 = onset of estrus). In Exp. 3 and 4, field trials were conducted to compare the effects of either hCG or progesterone treatment on d 11.5 on subsequent pregnancy rates. In Exp. 1, hCG transiently increased (P < .01) concentrations of progesterone and estradiol in plasma, whereas progesterone treatment increased only plasma progesterone. Neither hCG nor progesterone affected the duration of the estrous cycle. In Exp. 2, d-13 blastocysts were longer (3.5 +/- 1.6 vs .8 +/- .5 cm; Mean +/- SE; P < .05), and concentrations of protein and interferon tau (IFN tau) in uterine flushings were greater (10.7 vs 1.2 micrograms; P < .05) in hCG than in vehicle-treated ewes. Progesterone treatment did not affect blastocyst development. In Exp. 3, pregnancy rates tended to be greater (P < .10) in ewes given hCG than in those given vehicle (44/47; 94% vs 40/48; 83%); however, administration of progesterone in Exp. 4 had no effect on pregnancy rates (P < .14; 41/45; 91% vs 37/46; 80%; control ewes). These results indicate that treatment with hCG on d 11.5 stimulated uterine secretions and conceptus growth sufficiently to influence pregnancy rates.

published proceedings

  • J Anim Sci

author list (cited authors)

  • Nephew, K. P., Crdenas, H., McClure, K. E., Ott, T. L., Bazer, F. W., & Pope, W. F.

citation count

  • 45

complete list of authors

  • Nephew, KP||C├írdenas, H||McClure, KE||Ott, TL||Bazer, FW||Pope, WF

publication date

  • February 1994