Follicular growth, estrus and pregnancy after fixed-time insemination in beef cows treated with intravaginal progesterone inserts and estradiol benzoate.
An experiment was performed to compare the effects of 3 short-term treatments with progesterone and estradiol benzoate (EB) on follicular growth, synchrony of estrus and pregnancy rate after fixed-time insemination in lactating postpartum beef cows. In Treatment 1 (n = 46), each cow received a progesterone-containing intravaginal insert for 7 d with injection of EB (2 mg, i.m.) at the time of device insertion. In Treatment 2 (n = 46), the insert was used for only 5 d with injection of EB (2 mg, i.m.) at the time of insertion. Cows in Treatment 3 (n = 47) received an insert for 5 d with no EB at the time of insertion. Each cow in the 3 groups received PGF2 alpha (25 mg, i.m.) at the time of insert removal, followed by EB (1 mg, i.m.) 30 h later. The cows were then inseminated 28 to 30 h after treatment with EB (58 to 60 h after insert removal). Treatment with 2 mg EB terminated the growth of the largest ovarian follicle (> 5 mm in diameter) at device insertion in 16/16 and 14/15 cows in Treatments 1 and 2, respectively. Estrus was detected within an 8-h target period (48 to 56 h after insert removal) in 93, 87 and 81% of cows in Treatments 1, 2 and 3, respectively (P > 0.05). Pregnancy rates at 39 d post insemination were 60, 50 and 51% for Treatments 1, 2 and 3, respectively (P > 0.05). The pregnancy rates did not differ between cows that were anovulatory or those that had ovulated before the initiation of treatments (54%), or among cows that were 28 to 40, 41 to 60 or > 60 days post partum at insemination (43, 59 and 54%, respectively). Treatment with progesterone inserts for 5 or 7 d, PGF2 alpha at the time of insert removal and 1 mg EB 30 h later induced the high degree of synchrony of estrus and ovulation necessary for fixed-time insemination.
Bridges
P J
PJ
Division of Animal and Veterinary Sciences, West Virginia University, Morgantown 26506, USA.
Lewis
P E
PE
Wagner
W R
WR
Inskeep
E K
EK
D000282:Administration, Intravaginal; D000818:Animals; D000858:Anovulation; D002417:Cattle; D015237:Dinoprost / Q000494:pharmacology; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects / Q000502:physiology*; D005260:Female; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*
D011374:Progesterone; D004958:Estradiol; D015237:Dinoprost