Resynchronization of estrus in beef cattle: ovarian function, estrus and fertility following progestin treatment and treatments to synchronize ovarian follicular development and estrus

The objective was to optimize rebreeding of nonpregnant, previously inseminated beef cattle. In Experiment 1, 43 cows received a used intravaginal progesterone-releasing insert (IVPRI; Days 0-7) 12.3 d after ovulation and received concurrently no treatment, 100 microg gonadotropin releasing hormone...

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Bibliographic Details
Published in:Canadian veterinary journal 2007, Vol.48 (1), p.49-56
Main Authors: Colazo, M.G, Kastelic, J.P, Small, J.A, Wilde, R.E, Ward, D.R, Mapletoft, R.J
Format: Article
Language:English
Subjects:
Administration, Intravaginal
Animals
beef cows
Breeding - methods
Cattle - physiology
controlled internal drug release devices
Drug Implants
estradiol
Estradiol - analogs & derivatives
Estradiol - pharmacology
estrus
estrus synchronization
Estrus Synchronization - methods
Female
female fertility
Fertility - drug effects
gonadotropin-releasing hormone
Gonadotropin-Releasing Hormone - pharmacology
heifers
Insemination, Artificial - veterinary
melengestrol
Melengestrol Acetate - pharmacology
ovarian development
Ovarian Follicle - drug effects
Ovarian Follicle - growth & development
ovaries
ovulation
Pregnancy
Pregnancy Rate
progestational hormones
progesterone
Progesterone - pharmacology
Progestins - pharmacology
Random Allocation
rebreeding
Reproduction - drug effects
Reproduction - physiology
Scientific
Time Factors
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Summary:The objective was to optimize rebreeding of nonpregnant, previously inseminated beef cattle. In Experiment 1, 43 cows received a used intravaginal progesterone-releasing insert (IVPRI; Days 0-7) 12.3 d after ovulation and received concurrently no treatment, 100 microg gonadotropin releasing hormone (GnRH), 1 mg estradiol cypionate (ECP), or 150 mg progesterone. Emergence of a new ovarian follicular wave was most synchronous (P < 0.0001) in the GnRH group. In Experiment 2, 675 heifers were given GnRH or no treatment on Day 0, fed melengestrol acetate (MGA; 0.5 mg/head/d) from Days 0-5 (Day 0 = 13-14 d after timed insemination; TAI), given 0.5 mg ECP or nothing on Day 7, and reinseminated 6-12 h after onset of estrus. Estrus was more synchronous (P < 0.05) in heifers given GnRH versus no treatment on Day 0. In Experiment 3, 317 TAI heifers were resynchronized with either MGA or a used IVPRI with or without ECP on Day 7; estrus was more synchronous (P < 0.05) and pregnancy rates were higher (54.1% versus 39.2%, P < 0.05) in heifers given a used IVPRI than those fed MGA. For resynchronization of heifers, pregnancy rates were not significantly improved with GnRH treatment, but were higher with a used IVPRI than with MGA.
ISSN:0008-5286