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Journal of Dairy Science Vol. 65 No. 1 72-80
© 1982 by American Dairy Science Association ®
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Effects of Thyroprotein on Excretion of Polychlorinated Biphenyls by Lactating Cows1

L. B. Willett and T-T. Y. Liu

Department of Dairy Science, Ohio Agricultural Research and Development Center, Wooster 44691

ABSTRACT

Lactating dairy cows were fed 50 mg daily of commercially available polychlorinated biphenyl Aroclor 1254 for 20 days. Upon withdrawal of this from the ration, groups were given 0, 2 g/100 kg, or 4 g/100 kg body weight of thyroprotein (Protamone) for 57 days. Animals that continued to lactate were studied for an additional 70 days. The average concentration of polychlorinated biphenyls in milk fat on day 20, the last day of dosing, was 6.01 ± .6 ppm. Declines of concentrations in cows not fed thyroprotein were described by a two-component first order equation with half-lives of 5.7 and 68 days. Thyroprotein feeding provided a nearly dose responsive increase in heart and respiration rate and also weight losses among treated animals. Milk and fat production was increased in most animals; however, stage of lactation appeared to influence magnitude of response. Thyroprotein increased clearance of polychlorinated biphenyls during the thyroprotein feeding phase of the study. By day 52 daily excretion by control animals averaged 1.09 mg/day compared to 1.39 and 1.87 for animals receiving 2 or 4 g/100 kg body weight of thyroprotein. Withdrawal of thyroprotein resulted in a sharp decline in excretion of polychlorinated biphenyls from thyroprotein treated animals. On experimental day 98, control animals had an average daily excretion of .87 mg compared to .67 and .59 for the 2 and 4 g/100 kg body weight of thyroprotein groups.

FOOTNOTES

1 Approved for publication as Journal Article No. 27-81 of the Ohio Agricultural Research and Development Center, Wooster 44691.






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Copyright © 1982 by the American Dairy Science Association ®.