Hormonal responses of lactating dairy cattle to TRH and ACTH in a shade management system within a subtropical environment

H. Roman-Ponce, W. W. Thatcher, R. J. Collier, C. J. Wilcox

Research output: Contribution to journalArticle

11 Scopus citations


Lactating cows (64) were balanced by breed (54 Holstein and 10 Jersey) and assigned randomly to shade (S) or no shade (NS) management treatments for a continuous 20 wk trial beginning 5-5-76. A sub-sample of Holstein cows, five S and five NS, were fitted with jugular catheters 84 days after initiation of experiment. Thyrotropin Releasing Hormone (TRH; 100 μg) was administered intravenously at 1200 h to evaluate prolactin responses. Two days later each cow received intravenously 200 IU of ACTH at 1100 h to compare acute corticoid responses to ACTH. Mean prolactin response to TRH was greater for NS cows (291 vs 169 ng/ml; P < .01) as was peak plasma concentrations at 20 min (467 vs 267 ng/ml; P < .01). Mean corticoid response to ACTH injection was less for NS cows (52 vs 70 ng/ml; P < .10). Corticoid concentrations of plasma in both treatments had declined 65% by 7 h postinjection. These endocrine differences may be associated with thermoregulation and/or metabolic adjustments of cows exposed to different environmental systems of management during a seasonal period of thermal stress.

Original languageEnglish (US)
Pages (from-to)131-138
Number of pages8
Issue number2
StatePublished - Aug 1981


ASJC Scopus subject areas

  • Small Animals
  • Food Animals
  • Animal Science and Zoology
  • Equine

Cite this