• DOI:10.3168/JDS.S0022-0302(93)77589-X
• Corpus ID: 23456406

Postinsemination administration of receptal: follicular dynamics, duration of cycle, hormonal responses, and pregnancy rates.

@article{Stevenson1993PostinseminationAO,
  title={Postinsemination administration of receptal: follicular dynamics, duration of cycle, hormonal responses, and pregnancy rates.},
  author={Jeffrey S. Stevenson and A. P. Phatak and Immo Rettmer and R. E. Stewart},
  journal={Journal of dairy science},
  year={1993},
  volume={76 9},
  pages={
          2536-47
        }
}

• J. Stevenson, A. Phatak, +1 author R. Stewart
• Published 1 September 1993
• Biology, Medicine
• Journal of dairy science

In experiment 1, concentrations of LH, FSH, and progesterone, but not estradiol-17 beta, in blood serum were increased during 6 to 12 h after injection of 8 micrograms of receptal (GnRH agonist) administered on d 11 to 14 after estrus (d 0) and at first AI compared with saline treatment in lactating Holstein cows. Beginning 2 to 3 d after injection of receptal, concentrations of progesterone were increased for 3 d in nonpregnant cows and for 12 d in pregnant cows compared with controls of similar pregnancy status. Number of ovarian follicles determined by ultrasonography during 10 d after receptal was reduced, specifically those with antral diameters of > or = 10 mm. The dominant follicle in both groups began to decrease in diameter on the day following treatment, but the next dominant follicle began to increase in diameter 2.3 +/- .7 d later in receptal-treated cows than in controls, accounting for an increase in cycle duration of 2.5 +/- .8 d. In Experiment 2, a double-blinded study was conducted in eight herds in which cows (n = 1013) were AI at first detected estrus after 50 d postpartum and assigned randomly to receive either saline or 4, 8, or 12 micrograms of receptal on d 11 to 14 after first AI. Pregnancy rates were improved in one herd at all doses of receptal, but dose responses were inconsistent in remaining herds. A greater proportion of cows given receptal than controls returned to estrus after 24 d. Administration of a potent GnRH agonist altered number and distribution of ovarian follicles, increased cycle duration, and increased concentrations of progesterone without a consistent increase in pregnancy rates.