Methods of fertility enhancement and control of beef females
Favero, Raymond Jeffery
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https://hdl.handle.net/2142/22423
Description
Title
Methods of fertility enhancement and control of beef females
Author(s)
Favero, Raymond Jeffery
Issue Date
1992
Doctoral Committee Chair(s)
Kesler, Darrel
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
Chemistry, Pharmaceutical
Biology, Veterinary Science
Language
eng
Abstract
Experiments were conducted to investigate the methods of improving reproductive performance of estrous synchronized beef females. All females were initially synchronized with Syncro-Mate B$\sp\circler$ (SMB). The SMB treatment procedure consists of an intramuscular injection of norgestomet and estradiol valerate and a norgestomet impregnated hydron ear implant that was left in situ for 9 days. All females were artificially inseminated approximately 47 hours after implant removal. In the first series of experiments, norgestomet impregnated silicone implants were administered on day 9 or 12 and removed on day 21 after the initial SMB timed artificial insemination (AI). This treatment resulted in an increase in the calving rate to the initial SMB timed AI in beef heifers (P $<$.01), but had no effect on calving rates of post-partum beef cows. Following implant removal on day 21, the interval to estrus was uniform in treated females than in non-treated females (P $<$.05). Fertility at the return estrus of the non-pregnant females was not affected by treatment. In later experiments it was determined that following norgestomet impregnated silicone implant removal on day 21, non-pregnant females could be artificially inseminated 47 hours after implant removal. In another series of experiments, the effect of gonadotropin releasing hormone (GnRH) administration to estrous synchronized beef females was evaluated. GnRH administered by osmotic or bioerodable delivery systems at the time of norgestomet implant removal decreased calving rates in some studies and had no effect in others. GnRH administered at 30 hours after norgestomet implant removal either as a gelatin based ear implant or a gelatin implant housed in a projectile delivery system, improved calving rates of timed inseminated females. Norgestomet impregnated silicone implants were substituted for hydron implants into the conventional SMB procedure without affecting calving rates. The injectable portion of the SMB procedure was incorporated into a pellet and attached to the silicone implant, which improved the calving rates of cows (P $<$.05). Mounting activity, as monitored by KaMaR Heatmount Detectors$\sp\circler$, prior to a SBM timed AI was associated with the calving rates of cows (P $<$.05). Serum progesterone concentrations on day 21 after an SMB timed AI were 82.5% accurate in predicting subsequent calving.
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