Effects of progesterone and human chorionic gonadotrophin administration five days postinsemination on plasma and milk concentrations of progesterone and pregnancy rates of normal and repeat breeder dairy cows.
Treatment with a progesterone-releasing intravaginal device between days 5 and 12 after estrus elevated (p less than 0.05) plasma progesterone concentrations between days 6 and 8 in comparison with controls. Treatment with injectable progesterone (200 mg) on days 5, 7, 9 and 11 postestrus did not increase plasma progesterone concentrations over controls. The administration of 1500 IU human chorionic gonadotrophin (hCG) on day 5 after estrus resulted in a sustained increase (p less than 0.01) in plasma progesterone concentrations from day 8 until day 20 when measurements ceased. Pregnancy rates, as a result of artificial insemination (AI) at the pretreatment estrus, in these treatments (n = 12-14 each), were unaffected by any of the treatments and ranged from 57.1 to 75.0% at 45-60 days post-AI. In a field trial, of 36 repeat breeder cows treated with 1500 IU hCG 5.5 days after insemination, 47.2% were pregnant at 60 days, whereas 39.5% of saline-treated controls were diagnosed pregnant. Treatment with hCG significantly (p less than 0.05) increased milk progesterone concentrations over controls on days 14 and 20 after insemination.
Walton
J S
JS
Department of Animal and Poultry Science, University of Guelph, Ontario.
Halbert
G W
GW
Robinson
N A
NA
Leslie
K E
KE
D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle / Q000097:blood / Q000502:physiology*; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D003692:Delayed-Action Preparations; D005260:Female; D005298:Fertility / Q000187:drug effects*; D007267:Injections / Q000662:veterinary; D007315:Insemination, Artificial / Q000662:veterinary; D008892:Milk / Q000032:analysis; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D011374:Progesterone / Q000008:administration & dosage / Q000032:analysis / Q000097:blood / Q000494:pharmacology*; D011897:Random Allocation
D006063:Chorionic Gonadotropin; D003692:Delayed-Action Preparations; D011374:Progesterone