Effects of season and ovarian status on the outcome of long-term progesterone-based estrus synchronization protocols and ovulatory follicle development in Santa Ines ewes under subtropical conditions

Author(s)

Oliveira, M. E. F. ^[1] ; Ayres, H. ^[1] ; Oliveira, L. G. ^[2] ; Barros, F. F. P. C. ^[1] ; Oba, E. ^[3] ; Bicudo, S. D. ^[3] ; Bartlewski, P. M. ^[4] ; Fonseca, J. F. ^[5] ; Vicente, W. R. R. ^[1]

Affiliation

^[1] Sao Paulo State Univ, Coll Agr & Vet Sci, Dept Preventat Vet Med & Anim Reprod, Sao Paulo - Brazil

^[2] Sao Paulo State Univ, Coll Agr & Vet Sci, Dept Clin & Vet Surg, Sao Paulo - Brazil

^[3] Sao Paulo State Univ, Fac Vet Med & Anim Sci, Dept Anim Reprod & Vet Radiol, Sao Paulo - Brazil

^[4] Univ Guelph, Ontario Vet Coll, Dept Biomed Sci, Guelph, ON N1G 2W1 - Canada

^[5] Brazilian Agr Res Corp Embrapa Goats & Sheep, Coronel Pacheco, MG - Brazil

• Document type: Journal article
• Source: Theriogenology; v. 85, n. 3, p. 452-460, FEB 2016.
• Web of Science Citations: 6

Abstract

This study set out to investigate the efficiency of long-term estrus synchronization protocols and ovulatory follicle dynamics in ultrasonographically monitored Santa Ines ewes during lengthening (LD; September-October) and shortening photoperiods (SD; April May), and the transitional period (TP; January). In addition, the influence of ovarian status (e.g., size of antral follicles and/or presence of corpora lutea) at the outset of the estrus synchronization protocols on the ensuing development of ovulatory follicles was examined. Seventy sexually mature Santa Ines ewes were subjected to one of the two estrus synchronization regimens; on Day 0 (random day of the estrous cycle or anovulatory period), the ewes were fitted with an intravaginal progesterone (P-4)-releasing (controlled intrauterine drug release {[}CIDR]) device, which was left in place for 14 days (G-1CIDR, n = 35) or replaced on Day 7 (G-2CIDR, n = 35), and received an intramuscular injection of 10 mg of PGF2 alpha. The ewes allocated to the G-1CIDR group had mean serum P4 concentrations less than 2 ng/mL during the last 4 days of the synchronization protocol. There were no differences (P > 0.05) in mean ovulation rates between the two protocols tested nor among the ewes varying in ovarian status or studied at different times of the year, but ovulations occurred 12 hours later in the TP compared with the SD period (P < 0.05). Ovulatory follicles emerged earlier (P < 0.05) in the G-1CIDR group than in the G-2CIDR group (Day 8.3 +/- 0.5 vs. 9.2 +/- 0.4) and during LD (Day 7.1 +/- 0.6) compared with the TP (Day 9.1 +/- 0.6) and SD (Day 9.9 +/- 0.5 of the protocol). In conclusion, the replacement of CIDR devices prevented the occurrence of lower-than-normal luteal phase levels of P4 at the end of the 14-day estrus synchronization protocol. However, although this procedure and seasonal influences altered certain growth characteristics of ovulatory follicles, there were no effects of these factors on the mean ovulation rate. (c) 2016 Elsevier Inc. All rights reserved. (AU)

• FAPESP's process: 08/05503-2 - Viability of the superovulation started in the emergence of the first and last follicular wave on ciclicidade, transiton and anoestrus periods in Santa Inês sheep
• Grantee: Wilter Ricardo Russiano Vicente
• Support Opportunities: Regular Research Grants
• FAPESP's process: 08/01665-8 - FOLLICULAR DYNAMICS IN USE IN ESTRUS SYNCHRONIZATION AND SUPEROVULATION PROTOCOLS IN SANTA INES EWES
• Grantee: Maria Emilia Franco Oliveira
• Support Opportunities: Scholarships in Brazil - Doctorate