| Autor: |
M E, Wehrman, M S, Roberson, A S, Cupp, F N, Kojima, T T, Stumpf, L A, Werth, M W, Wolfe, R J, Kittok, J E, Kinder |
| Rok vydání: |
1993 |
| Předmět: |
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| Zdroj: |
Biology of reproduction. 49(2) |
| ISSN: |
0006-3363 |
| Popis: |
The objectives of this study were to determine the effects of dose of exogenous progesterone (P4) prior to artificial insemination on concentrations of 17 beta-estradiol (E2) and on conception rates in bovine females. Heifers (n = 100) and cows (n = 100) received P4-releasing intravaginal devices (PRIDs) to produce two different circulating concentrations of P4. All animals received a single PRID 10 days before (Day-10) the start of the breeding season (Day 0). In animals that received the low dose of P4 (1 PRID, target concentration of 2-3 ng/ml of plasma), the original PRID remained in place for 10 days. In animals that received the larger dose of P4 (2 PRIDs, target concentration of 5-8 ng/ml of plasma), an additional PRID was inserted on Day -9. To maintain concentrations of P4 in the 2-PRID group, the PRIDs inserted on Days -10 and -9 were replaced with new PRIDs on Days -5 and -4, respectively. Prostaglandin F2 alpha (25 mg) was administered to all animals on Days -9 and -3 to remove the endogenous source of P4. Following PRID removal, animals were artificially inseminated 12 h after signs of behavioral estrus were observed. A treatment-by-day interaction (p0.0001) was observed for concentrations of P4 in circulation of both heifers and cows. Animals that received 2 PRIDs had greater (p0.001) concentrations of P4 by Day-8 of treatment than animals that received 1 PRID. In cows that received 1 PRID, concentrations of E2 increased 2.4-fold from Day-10 (6.8 +/- 1.0 pg/ml) to Day-2 (16.7 +/- 1.4 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS) |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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