The Effect of Thyroprotein (“Protamone”) on Milk Production and on Some of the Constituents of the Milk and Blood of Dairy Cows

The feeding of “Protamone” at the rate of 1 gram per 53 pounds of body weight to dairy cows resulted in the following observations: An increase in milk production which was dependent, to a large extent, upon the nutrient intake of the cow. This increase was followed by a rapid decline to below the normal level after termination of “Protamone” feeding. Considerable individual variation was noted in milk production responses. No changes in butterfat percent due to “Protamone” were found. A decrease in body weight and increases in pulse and respiratory rates. No changes in milk or blood plasma, carotene, or ascorbic acid. Frequent decreases in both blood and milk vitamin A of individual “Protamone” fed cows were observed. These results are not sufficiently consistent to be conclusive but indicate that prolonged “Protamone” feeding may affect the vitamin A requirements. No change in milk total protein. A marked decrease in milk thiamin during “Protamone” feeding at both levels of nutrient intake employed. During the control periods thiamin increased to above normal levels. No change in the riboflavin content of the milk occurred during the period of normal grain feeding but a decrease did occur in the experimental group during the period in which grain feeding was limited. This decrease was followed by a rapid increase during the control period. While these changes in both riboflavin and thiamin occurred within the normal range, as indicated by the control group, they may be indications that deficiency levels may be encountered in prolonged “Protamone” feeding. Basal metabolism tests on rats fed exclusively on milk from “Protamone” fed cows indicated that if the hormone is secreted by the mammary gland it is in amounts too small to detect by this method. The possibility of the existence of thiamin and riboflavin deficiency during long periods of “Protamone” feeding is discussed. Vitamin A deficiency might likewise result from “Protamone” feeding if the dosage is too high and when fed during the winter months when the Vitamin A intake is likely to be low. In view of these results it would seem that great care should be exercised in feeding “Protamone” to dairy cows until more is known of its physiological effect on the cow. The greatest possibility for its use may lie in the treatment of hypothyroid 3 individuals rather than in general feeding to all milking cows in the herd. This involves the development of a technique for readily determining the state of thyroid metabolism in the individual cow.