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Effects of Dietary NaF on Dairy Cows. II. Effects on Milk Production¹

Department of Biochemistry, University of Wisconsin, Madison

ABSTRACT

A study of the tolerance of lactating cows to added dietary increments of a soluble fluoride (NaF) over a 5 1/2-yr. period has been made. The results indicate that under adequate nutritional and husbandry conditions, levels of 50 p.p.m. of fluorine fed as NaF produced no direct deleterious effect upon milk secretion. Sustained fluorine ingestion, with average intake levels of 1.5, and peak intakes of 1.7 or more, mg. of F/kg body weight, led to a reduction of milk and butterfat production in certain cows, as the result of anorexia toward NaF-containing feed, which was accompanied by excessive weight loss and stiffness in the legs. These results indicate further that the effect of fluorine fed in the form of NaF on milk production was a secondary effect conditioned by a curtailed feed intake. The cows in this study tolerated 30 p.p.m. fluorine in their ration, whereas 40 p.p.m. was apparently near the marginal zone of tolerance and 50 p.p.m. in the ration resulted in the development of fluorine toxicosis. The addition of calcium reduced the toxicity of the added NaF.

A latent period of from 2 to 5 yr. elapsed between the time the fluorine effects were first noticed on the incisor teeth and the development of other physiologic effects, including the inhibition of milk production. Thus, these studies contribute further evidence to show that the development of fluorine toxicosis is a function of the duration of exposure (time), as well as of level of ingestion. Prolonged dry periods allowed sufficient recovery from debilitating fluorosis for subsequent normal lactation and milk production.

¹ Published with the approval of the Director of the Wisconsin Agricultural Experiment Station. Supported in part by a grant fron the Aluminum Company of America, Pittsburgh, Pennsylvania, on behalf of itself and the Aluminum Laboratories, Ltd., the American Smelting and Refining Co., the Kaiser Aluminum and Chemical Corp., the Monsanto Chemical Co., the Reynolds Metal Co., the Tennessee Valley Authority, the U. S. Steer Corp. of Delaware, and Westvaco, Chemical Division of Food Machinery and Chemical Corp.

² Present address: Virginia Polytechnic Institute, Blacksburg, Virginia.