J. Anim Sci.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J. Anim Sci. 1966. 25:150-156.
© 1966 American Society of Animal Science
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Yousef, M. K.
Right arrow Articles by Johnson, H. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Yousef, M. K.
Right arrow Articles by Johnson, H. D.

Calorigenesis of Dairy Cattle as Influenced by Thyroxine and Environmental Temperature1

M. K. Yousef and H. D. Johnson2

University of Missouri, Columbia

Abstract

Four Holstein cows were used to determine the influence of thyroxine on calorigenesis. The objective of this study was to determine the calorigenic action, latent period, biological effective time and peak metabolic response at different environmental temperatures. Injection of L-thyroxine at 18° and at 32° C. increased "resting or standing" metabolism, pulse rate and lactation. The latent period was 2 to 3 days and 1 to 2 days at 18° and 32° C, respectively. The biological effective time was found to be 4 to 5 days and 5 to 6 days at the comfort zone and under exposure to heat, respectively. The rate of thyroxine metabolism is slow in cattle and decreases progressively under hot conditions. The results suggest that estimates of thyroxine secretion rate are too low when calculated by blood methods and too high when the in vivo thyroid measurement technique is used. High temperature (32° C.) decreased pulse rate, oxygen consumption, milk production and feed intake and increased rectal temperature and respiration rate, indicating a serious disturbance in the cow's thermal equilibrium.

Footnotes

1 Contribution from Missouri Agricultural Experiment Station. Journal Series No. 2980. Approved by the Director.

2 Dairy Husbandry Department.

3 L-thyroxine was kindly supplied by H. L. Fevold, Travenol Laboratories, Inc., Morton Grove, Illinois.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1966 by the American Society of Animal Science.