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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Comparison of two timed artificial insemination system schemes to synchronize estrus and ovulation in Nellore cattle

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Author(s):
Ferraz Junior, Marcos V. C. ; Pires, Alexandre V. ; Biehl, Marcos V. ; Santos, Marcelo H. ; Barroso, Jose P. R. ; Goncalves, Jose R. S. ; Sartori, Roberto ; Day, Michael L.
Total Authors: 8
Document type: Journal article
Source: Theriogenology; v. 86, n. 8, p. 1939-1943, NOV 2016.
Web of Science Citations: 5
Abstract

The aim of this study was to evaluate the reproductive performance of 411 Nellore cows (198 nulliparous, 80 primiparous, and 133 multiparous) submitted to the 5dCO-Synch + P4 or 7dEB + P4 systems. The 5dCO-Synch + P4 system consisted of insertion of an intravaginal progesterone (P4) insert and 100 mu g of GnRH (intramuscularly {[}i.m.]) on Day 0. On Day 5, the P4 insert was removed, and two doses of 25 mg of PGF(2 alpha) (i.m.) were administered 6 hours apart. Cows not detected in estrus until 55 hours after insert removal received 100 mu g of GnRH i.m. 17 hours later (i.e., 72 hours after P4 removal). The 7dEB + P4 system consisted of insertion of a P4 insert and 2 mg of estradiol benzoate (i.m.) on Day 0. On Day 7, the P4 insert was removed and 25 mg of PGF(2 alpha), 0.6 mg of estradiol cypionate, and 300 IU of eCG were administered i.m. In both systems, artificial insemination (AI) was performed according to estrus detection (i.e., cows detected in estrus until 55 hours after insert removal were inseminated at 55 hours and cows detected in estrus later or those not detected in estrus were inseminated at 72 hours). Estrus-detection risk was greater (P < 0.05) in 7dEB + P4 (80.4%) than 5dCO-Synch + P4 system (36.4%). Progesterone concentration 10 days after AI was greater (P < 0.05) in 7dEB + P4 than 5dCO-Synch + P4 system in primiparous and multiparous but did not differ between systems in nulliparous cows. Pregnancy per Al was greater (P < 0.05) in 7dEB + P4 (49.7%) than 5dCO-Synch + P4 (35.4%) system. Primiparous had lower estrus-detection risk (25.0%), ovulation risk (76.6%), and pregnancy per AI (28.7%) than multiparous or nulliparous cows. In conclusion, reproductive performance was reduced with the 5dCO-Synch + P4 in comparison with the 7dEB + P4 system in Nellore cows. Moreover, the reproductive traits observed for primiparous cows indicate that more attention is required when timed AI programs are started early after calving. (C) 2016 Elsevier Inc. All rights reserved. (AU)

FAPESP's process: 12/01345-9 - Pharmacological manipulation of the estrous cycle in Nellore cows: I - Effect of doses of PGF2a for luteolysis on days 5 and 7 of the estrous cycle. II - Effect of replacement of GnRH by EB, in the 5 Co-Synch program, at estrus detection and distribution
Grantee:Alexandre Vaz Pires
Support Opportunities: Regular Research Grants