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Journal of Dairy Science Vol. 57 No. 2 193-197
© 1974 by American Dairy Science Association ®
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Effect of Thyroid Status on Digestive Tract Fill and Flow Rate of Undigested Residues in Cattle1

J. K. Miller, E. W. Swanson, W. A. Lyke, B. R. Moss2 and W. F. Byrne3

Comparative Animal Research Laboratory, Oak Ridge, Tennessee 37830
and Department of Animal Science, University of Tennessee, Knoxville 37901

ABSTRACT

Retention of feed residues in the digestive tract was determined in 16 thyroid intact cows and 12 cows with severe iodine-131 thyroid irradiation damage, 4 of which had been fed 8 g thyroprotein daily for 60 days. Recoveries during 6 to 10 daily doses of a nonabsorbed marker (cerium-141, cerium-144 praseody-mium-144, or scandium-46) in feces were: thyroid intact cows, 76.6; thyroid damaged cows, 54.4; and thyroid damaged cows fed thyroprotein, 78.4% of the total dose. Corresponding recoveries from the digestive tract at slaughter were marker, 21.5, 43.5, and 18.9% of the total dose and dry matter, 1.6, 2.5, and 1.7 kg per 100 kg body weight. Single oral doses of cerium-144 praseodymium-144 were used as a marker to follow movement of feed residues through digestive tracts of two intact and two thyroid damaged cows. The flow rate constant for thyroid damaged cows was less than half that for intact cows. Thyroprotein fed daily for 70 days raised plasma thyroxine to the normal range, increased feed intake, and reduced feed retention to near normal in thyroid damaged cows. Thyroprotein caused only slight changes in cows with previously normal thyroid function.

FOOTNOTES

1 Research sponsored by the U.S. Atomic Energy Commission under Contract No. AT-40-1-GEN-242 with the University of Tennessee.

2 Present address: Animal and Range Sciences Department, Montana State University, Bozeman 59715.

3 Present address: Route 4, Powell, Tennessee 37849.






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