Abstract
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, im) 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, im) 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 PGF2α (25 mg, im) at the time of insert removal, followed by EB (1 mg, im) 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, PGF2α 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.
Original language | English |
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Pages (from-to) | 573-583 |
Number of pages | 11 |
Journal | Theriogenology |
Volume | 52 |
Issue number | 4 |
DOIs | |
State | Published - Sep 1999 |
Bibliographical note
Funding Information: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, im) 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, im) 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 PGFrcr (25 mg, im) at the time of insert removal, followed by EB (1 mg, im) 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 terminamd the growth of the largest ovarian follicle (~5 mm in diameter) at device insertion in 16/16 and 14115c ows 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 I,2 and 3, respectively (PXl.05). Pregnancy rates at 39 d post insemination were 60,50 and 51% for Treatments 1,2 and 3, respectively (P>O.O5). 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 260 days post partum at insemination (43,59 and 54%, respectively). Treatment with progesterone inserts for 5 or 7 d, PGFza at the time of insert removal and 1 mg EB 30 h later induced the high degree of synchrony of e&us and ovulation necessary for fixed-time insemination. aa 1999 ty Elseviar science Inc. Key words: cattle, pregnancy, fixed-time insemination, postpartum Acknowledgments: We thank W. L. Ferrell for AI and managemento f animals, M. R. Weaver for management of animals and Dr. H. Hafs for critical review of this manuscript. Hormones used were generously provided by InterAg Division of DEC International, Hamilton, NZ, through Dr. H. Hafs. This work is published with the approval of the Director of the WV Agricultural and Forestry Experiment Station as Scientific Paper No. 2709 from the Division of Animal and Veterinary Sciences. Supported by Hatch Project 321 (NE161).
Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
Keywords
- Cattle
- Fixed-time insemination
- Postpartum
- Pregnancy
ASJC Scopus subject areas
- Small Animals
- Food Animals
- Animal Science and Zoology
- Equine