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

This study set out to investigate the efficiency of long-term estrus synchronization protocols and ovulatory follicle dynamics in ultrasonographically monitored Santa Inês ewes during lengthening (LD; September−October) and shortening photoperiods (SD; April−May), and the transitional period (TP; Ja...

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Bibliographic Details
Published in:Theriogenology 2016-02, Vol.85 (3), p.452-460
Main Authors: Oliveira, M.E.F., Ayres, H., Oliveira, L.G., Barros, F.F.P.C., Oba, E., Bicudo, S.D., Bartlewski, P.M., Fonseca, J.F., Vicente, W.R.R.
Format: Article
Language:English
Subjects:
Administration, Intravaginal
Animals
Climate
Corpus Luteum - diagnostic imaging
Dinoprost - administration & dosage
Estrous Cycle
Estrus synchronization
Estrus Synchronization - methods
Ewe
Female
Ovarian Follicle - growth & development
Ovary - diagnostic imaging
Ovary - physiology
Ovulatory follicle
Photoperiod
Progesterone
Progesterone - administration & dosage
Progesterone - blood
Seasons
Sheep - physiology
Time Factors
Ultrasonography
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Summary:This study set out to investigate the efficiency of long-term estrus synchronization protocols and ovulatory follicle dynamics in ultrasonographically monitored Santa Inês 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 Inês 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 (P4)-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 PGF2α. 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 
ISSN:0093-691X
1879-3231
DOI:10.1016/j.theriogenology.2015.09.024