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Follicle Stimulating Hormone Pattern and Luteal Function in Ewes Receiving Bovine Follicular Fluid during Three Stages of the Estrous Cycle^1,2,

West Virginia University³ Morgantown 26506-6108

Abstract

The objectives of this study were to determine 1) the ability of charcoal-extracted bovine follicular fluid (bFF) to suppress endogenous follicle stimulating hormone (FSH) at various stages of the estrous cycle and 2) the effects of suppression of FSH on luteal function and lengths of the current and subsequent estrous cycles. Twenty-six mature ewes were assigned randomly to receive 5 ml of either bFF or saline, subcutaneously, at 8-h intervals on d 1 through 5 (bFF n=6; saline n=3), d 6 through 10 (bFF n=6; saline n=3) or d 11 through 15 (bFF n=6; saline n=2) of the estrous cycle (d 0=estrus). Blood was collected daily beginning at estrus and continued until the third estrus (two estrous cycles) or 40 d; more frequent samples were collected 2 h prior to initiation of treatment (0600), hourly for the first 8 h of treatment, then every 4 h until 0800 on the first day after treatment, and finally at 1600 and 2400 on that day. Plasma concentrations of FSH were lower (P<.001) in bFF-treated than in saline-treated ewes. Treatment with bFF reduced (P<.05) plasma concentrations of progesterone during the current but not during the subsequent estrous cycle. Treatment with bFF did not affect plasma concentrations of estradiol-17β. Administration of bFF on d 11 through 15 of the estrous cycle lengthened the interval from the decline in progesterone to estrus and the inter-estrous interval by approximately 3 and 4 d, respectively. Treatment with bFF reduced luteal function in the current cycle when given during any of the treatment periods, while suppression of FSH by bFF treatment on d 11 through 15 lengthened the follicular phase of the estrous cycle.

¹ Published with the approval of the Director of the West Virginia Agr. and For. Exp. Sta. as scientific article no. 2040. Supported by Hatch Project 224 (NE-72).

² The authors thank Dr. G. D. Niswender, Colorado State Univ. for the ovine LH antisera (GDN #15); Dr. L. E. Reichert, Jr., Albany Med. College for the purified ovine LH (LER 1374-A) used for iodinations, Dr. D. J. Bolt, USDA Beltsville, MD, for the reagents used to assay ovine FSH; Dr.,R. L. Butcher, West Virginia Univ., Obstet. and Gynecol, for the antisera to progesterone and estradiol-17β; Dr. Scott Pore, West Virginia Univ., Microbiol., for performing cultures of bovine follicular fluid.

³ Div. of Anim. and Vet. Sci.