Equine Luteinizing Hormone Profile Characteristics: Effects of Sampling Interval, Method of Analysis, Reproductive State, Gonadotropin-Releasing Hormone and Foal Removal
Sargent, Gayla Fletcher
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https://hdl.handle.net/2142/70042
Description
Title
Equine Luteinizing Hormone Profile Characteristics: Effects of Sampling Interval, Method of Analysis, Reproductive State, Gonadotropin-Releasing Hormone and Foal Removal
Author(s)
Sargent, Gayla Fletcher
Issue Date
1987
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Biology, Veterinary Science
Abstract
Studies in several species have indicated that luteinizing hormone (LH) profile characteristics vary with reproductive state. LH profiles may change rapidly, with pulses often occurring on an hourly or even more frequent basis. Only recently have these transitory changes been examined in mares. The results from the studies in this thesis identified characteristics of the LH profile in pony mares during different reproductive states and as influenced by gonadotropin-releasing hormone (GnRH) and the suckling stimulus, and delineated some appropriate methods for LH pulse analysis.
Cyclic and postpartum pony mares were utilized. Blood was collected every 15 or 30 minutes by jugular venipuncture and plasma subsequently assayed for LH concentrations.
Several methods were employed for pulse analysis. A modified Pulsar program (Merriam and Wachter, 1982; Gitzen and Ramirez, 1986) was selected as the most appropriate method for equine LH pulse analysis.
Number of LH peaks and peak frequency increased linearly as sampling interval decreased. Four-hour or greater sampling periods provided adequate data for analysis of LH pulse characteristics requiring multiple peaks.
A 20 (mu)g dose of GnRH induced a LH pulse similar to endogenous patterns. Only maximum LH differed, being greater in GnRH-treated mares.
Estrous mares had more LH peaks and greater frequency than diestrous mares. Other examined pulse characteristics were similar. Both groups exhibited episodic release of LH, as did postpartum mares.
Short-term foal removal had no apparent effect on interval from parturition to subsequent estrus and ovulation.
In summary, equine LH profiles changed as frequently as every 30 to 60 minutes, with pulse frequency being greater during the follicular phase than during either the luteal phase or the early postpartum period. Equine LH pulse characteristics were effected by method of analysis, sampling interval, and sampling period. Endogenous LH pulses could be provoked with injection of low doses of GnRH. Suckling did not appear to modify the pulse characteristics of equine LH.
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