Ovarian and Pituitary Responses of Seasonally and Postpartum Anestrous Ewes to Gonadotropin Releasing Hormone
Vincent, Douglas Lee
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https://hdl.handle.net/2142/70010
Description
Title
Ovarian and Pituitary Responses of Seasonally and Postpartum Anestrous Ewes to Gonadotropin Releasing Hormone
Author(s)
Vincent, Douglas Lee
Issue Date
1983
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)
Agriculture, Animal Culture and Nutrition
Abstract
In the first experiment, seasonally anestrous ewes were treated with saline or gonadotropin releasing hormone (GnRH) either intramuscularly in saline, subcutaneously in carboxymethylcellulose or subcutaneously in a gelatin capsule. Ewes were bled for progesterone determination prior to treatment and up to 13 days after treatment. Ewes were classified into one of four progesterone categories: cyclic, transient increase, prolonged increase, or no response. More ewes were classified as having a prolonged increase in progesterone in the GnRH in gelatin capsule-treated ewes (40%) than in the saline-treated controls (0%). GnRH in gelatin capsule-treated ewes, classified as having a prolonged increase in progesterone, had greater (P (LESSTHEQ) .05) progesterone concentrations than other GnRH-treated ewes that were classified in the prolonged increase in progesterone category.
In the second experiment postpartum ewes that lambed in the spring and fall were treated with pregnant mare serum gonadotropin (PMS) or saline on day 12 postpartum followed by 250 (mu)g GnRH either intravenously in saline or subcutaneously in a gelatin capsule 24 h later. Eight postpartum ewes were treated with vehicle only in the spring (4) and fall (4) and served as controls. Blood was collected on days 1, 4, 7, 10 and 13 to 19 postpartum for progesterone determination. Blood for LH was collected on day 13 just prior to GnRH or vehicle treatment and hourly thereafter for 12 h. Mid-ventral laparotomy was done on day 16 postpartum to evaluate ovarian responses to treatment and to flush oviducts for eggs. A second laparotomy was done 3 days later to check ovarian status. Sixty percent of ewes treated with GnRH had ovulated compared to 13% of vehicle treated ewes by day 16 postpartum. GnRH in a gelatin capsule (250 (mu)g) increased the number of ewes ovulating from which ova were recovered, increased corpora lutea diameter on day 16 postpartum, increased peak LH concentrations, and the duration of the GnRH induced LH release over the same dose of GnRH injected intravenously. Progesterone concentrations following induced ovulation with GnRH in a gelatin capsule were greater than progesterone concentrations in ewes ovulating following intravenous GnRH.
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