Journal of Animal Science, Vol 72, Issue 11 2948-2954, Copyright © 1994 by American Society of Animal Science

JOURNAL ARTICLE

Follicular dynamics, embryo production, and hormonal responses in Brahman heifers following sympathetic stimulation

B. B. Carpenter, T. D. Forbes, M. Carpena, A. Rocha, H. Rodriguez and R. D. Randel
Texas Agricultural Extension Service, Ft. Stockton.

The purpose of this experiment was to characterize adrenal and ovarian responses to N-methyl-beta-phenethylamine (NMP) or ACTH. Thirty-three heifers with functional midcycle corpora lutea were placed on a 4-d superovulation regimen. They were injected twice daily with FSH-P and either saline (Control), ACTH (80 IU), or NMP (1 mg/kg BW). An initial blood collection preceded jugular delivery of saline, NMP, or ACTH, i.m. delivery of FSH and PGF2 alpha (d 3), and ultrasound (d 1 to 4). A second blood collection was made 6 min after treatment. Sampling continued daily until d 13. Embryos (age 6 to 7 d) were collected and evaluated. Concentrations of cortisol (posttreatment minus pretreatment) were greatest (P < .05) in NMP- and ACTH-treated heifers. Treatment did not affect mean numbers of small (< 4 mm), large (> 8 mm), or total follicles on d 2 to 4. Heifers receiving NMP had fewer medium follicles (4 to 8 mm) on d 2 and 3, and ACTH-treated heifers had fewer medium follicles on d 4 (P < .07). Mean estradiol concentrations on d 2 to 4 were unaffected by treatment (P > .32). Following PGF2 alpha, time to onset of standing estrus was less (P < .05) in Control than in ACTH- and NMP-treated heifers (41.4 vs 47.9 and 58.9 h, respectively). A greater frequency (P < .05) of reproductive anomalies (no estrus; no ovulation [i.e., progesterone < 1 ng/mL]; luteal failure [i.e., progesterone < 1 ng/mL but embryos recovered]) occurred in NMP (5/11) than in Control (0/10) or ACTH (2/10) heifers.(ABSTRACT TRUNCATED AT 250 WORDS)