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Studies on Parakeratosis in Swine

United States Department of Agriculture¹

Abstract

The relationship between zinc and calcium contents of the diet and the incidence of both severe parakeratosis and depressed rate of growth was demonstrated in an experiment involving 8 lots of 6 pigs each. Feeding a basal diet containing 32 p.p.m. of zinc with a calcium content of 0.48% produced mild to moderate parakeratosis in 3 of 6 pigs. An increase in calcium content (0.67 or 1.03%) at the same (32 p.p.m.) zinc level produced severe parakeratosis in all pigs (2 lots of 6 each). The addition of zinc oxide to increase total zinc content of the diet to 44 p.p.m. reduced the incidence of parakeratosis from 3 of 6 to 1 of 6 animals affected at 0.48% calcium, from 6 of 6 to 2 of 6 affected at 0.67% calcium, and from 6 of 6 to 4 of 6 animals affected with 1.03% calcium in the diet. The further addition of zinc oxide to increase total zinc content to 80 p.p.m. in the diet completely prevented parakeratosis on the two levels of calcium tested (0.67 and 1.03%). Rate of gain proved to be a sensitive indicator of occurrence, severity, and duration of parakeratosis. Depression of appetite and rate of gain were usually observed before skin lesions appeared and the first noticeable symptoms of recovery were improved appetite and dramatic increases in weight.

Pigs with acute parakeratosis showed marked improvement within the first week after changing from 32 p.p.m. of zinc in the diet to 80 p.p.m. and within 28 days were normal except that some of the scabs and encrustations had not shed completely. Definite lesions indicative of parakeratosis appeared in 3 out of 6 pigs 28 days after they were shifted from 80 p.p.m. of zinc to 32 p.p.m. of zinc in the diet.

The results indicate that, in diets for growing pigs which contain up to 1.0% calcium, the minimum zinc content for prevention of parakeratosis is between 44 p.p.m. and 80 p.p.m.

Studies on blood chemistry, while not conclusive, provide preliminary data for further study of the probable mechanisms involved in production of parakeratosis. The results suggest that parakeratosis may depress levels of hemoglobin, serum inorganic phosphorus, and blood sugar and in addition may cause a shift in albumin-globulin ratio. Pigs receiving the lower levels of zinc (32 or 44 p.p.m.) exhibited extremely variable serum alkaline phosphatase activity as compared with pigs on the high zinc diet.

¹ Animal and Poultry Husbandry Research Branch, Agricultural Research Service, Agricultural Research Center, Beltsville, Maryland.

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