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


     

J. Anim Sci. 1968. 27:677-683.
© 1968 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 Hahn, L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Yousef, M. K.
Right arrow Articles by Hahn, L.

Effect of Ruminal Heating on Thyroid Function and Heat Production of Cattle1

M. K. Yousef2, W. D. Robertson2, H. D. Johnson2 and L. Hahn3

University of Missouri and U.S. Department of Agriculture, Columbia

Abstract

The hypothesis that ruminal heating decreases thyroid function and metabolic rate comparable to the decreases obtained by exposure of the whole animal to heat was tested. During the investigation, four nonlactating cows with rumen fistulas were kept at a thermoneutral temperature. At this temperature, the rumen was heated with hot water circulating through stainless steel coils placed in the rumen via the fistula. The effect of ruminal heating on thyroid was studied by the thyroxine I131 disappearance rate (K) and PBI. Heat production was measured with an indirect calorimeter. Ruminal heating significantly decreased K and heat production. Respiratory rates and rectal temperatures were not affected using the exogenous heat load of 125 kcal./hr. but were increased by the 300 kcal./hr. heat load. Heating the rumen is suggested as exerting its effect by one or both of the following mechanisms: (a) by stimulating the "central warmth detectors" through impulses from the nerve endings in the rumen to depress the TRF; (b) by alteration of the requirement of the tissues for thyroid hormone. The latter may occur indirectly by a modification of some substrate level which in turn decreases thyroid function via the feed-back mechanism.

Footnotes

1 Contribution from the Mo. Agr. Exp. Sta. Journal Series No. 5217. Approved by the Director.

2 Dairy Husbandry Department.

3 Agricultural Engineering Research Division.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1968 by the American Society of Animal Science.