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

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11 Scopus citations

Abstract

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
JournalTheriogenology
Volume16
Issue number2
DOIs
StatePublished - Aug 1981

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ASJC Scopus subject areas

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

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