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Effects of estradiol and progestins on follicular regression before, during, and after follicular deviation in postpartum beef cows.

Author(s): Siqueira LC, Oliveira JF, Rovani MT, Ferreira R, Borges LF, Goncalves PB

Affiliation(s): Laboratory of Biotechnology and Animal Reproduction - BioRep, Federal University of Santa Maria, Department of Large Animal Clinical Sciences, 97105-900 Santa Maria, RS, Brazil.

Publication date & source: 2009-03-01, Theriogenology., 71(4):614-9. Epub 2008 Nov 1.

The objective was to evaluate the effect of estradiol benzoate (EB), in association with three progestin protocols, on ovarian follicular regression of suckled beef cows treated at three stages of follicular development (pre-deviation, deviation, or post-deviation). Thirty-six suckled beef cows (60-90d postpartum, given 125mug cloprostenol on two occassions, 12h apart). Forty-eight hours after the first cloprostenol treatment, all follicles >5mm were ablated and transrectal ultrasound scanning (8MHz) was performed every 24h until Day 7 (Day 0=treatment). When the largest follicle reached a designated diameter of 5-7, 8-10 or >10mm, cows were randomly allocated to receive 2mg of EB im in association with an intravaginal device containing 250mg of medroxyprogesterone acetate (MPA) with or without 100mg of progesterone (P(4)) given im, or an intravaginal device containing P(4) (3x3 factorial design). Treatments induced follicular regression in all cows, independent of follicular stage or treatment. There was no interaction between progestin treatment and follicular stage, nor was there any difference in the time of follicular regression or new wave emergence among follicular stages. Treatment with MPA plus P(4) delayed follicular regression. In conclusion, EB in association with various progestins induced regression of growing follicles and emergence of a new follicular wave in postpartum beef cows, regardless of the stage of follicular development.

Page last updated: 2009-02-08

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