Methods to Induce and Synchronize Ovulation and to Enhance Corpus Luteum Function and Fertility in Beef Females (Postpartum Cows, Heifers)
Do Valle, Ezequiel R.
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https://hdl.handle.net/2142/70034
Description
Title
Methods to Induce and Synchronize Ovulation and to Enhance Corpus Luteum Function and Fertility in Beef Females (Postpartum Cows, Heifers)
Author(s)
Do Valle, Ezequiel R.
Issue Date
1986
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
Agriculture, Animal Culture and Nutrition
Abstract
A competitive inhibition double antibody enzyme immunoassay (EIA) for determining plasma levels of progesterone in beef females was developed using a horseradish peroxidase labelled progesterone conjugate and polysterene tubes. The sensitivity of the assay was 5 pg and 84% of the progesterone spiked to samples was recovered, which was similar to recovery of tritiated progesterone spiked samples (83%). The first antibody (anti 11-alpha-hydroxy progesterone hemisuccinate : bovine serum albumin) had a high specificity for progesterone and the intraassay and interassay coefficients of variation of pooled samples were 7.9% and 13.8%, respectively. Samples assayed by both RIA and EIA were in excellent agreement (r = 0.96).
The effects of GnRH and its method of administration on the incidence of ovulation, subsequent corpus luteum function and fertility at timed insemination of beef heifers synchronized with norgestomet and PGF-2 alpha were determined. Plasma levels of progesterone, determined by EIA were utilized to determine reproductive status, ovulation response and luteal function. GnRH, but not its method of administration, improved ovulation response in anestrous heifers without reducing ovulation response in cyclic heifers. The incidence of short luteal phases was low (4.3%), regardless of treatment and reproductive status. GnRH, but not its method of administration improved calving rates to timed insemination for all heifers, from 29.2% to 47.6%.
The effects of short term calf removal, GnRH and its method of administration were also determined in postpartum suckled beef cows synchronized with norgestomet and PGF-2 alpha. It was demonstrated that GnRH, but not its method of administration, was highly effective in enhancing ovulation response and fertility in postpartum suckled cows (anestrous and cyclic). GnRH improved calving rates to timed insemination for all cows from 31.3% to 43.8%. The incidence of short luteal phases was low for both anestrous (8.7%) and cyclic cows (2.6%) and no effects of GnRH or its method of administration could be detected. Short-term calf removal alone or associated with GnRH had no effect on ovulation response, corpus luteum function and fertility at timed insemination.
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