Influence of Dietary Zinc, Corn Oil and Cadmium on Certain Blood Components, Weight Gain and Parakeratosis in Young Pigs

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Abstract
Forty virus-pneumonia-free Yorkshire growing pigs were used in each of two experiments to study the effects of supplemental Zn, corn oil and Cd on body weight gain, incidence of parakeratosis and levels of certain blood constituents. In experiment 1, when part of the corn in the diet of 3-week-old pigs was replaced by glucose so as to reduce the Zn concentration from approximately 33 ppm to 24 ppm, there was no reduction in weight gain but an 80% incidence of parakeratosis occurred. There was no parakeratosis among pigs fed diets containing no glucose or among those fed the low-Zn diet supplemented with corn oil. Blood glucose level was not significantly affected by diet, but serum cholesterol tended to be elevated after 4 weeks and 6 weeks in pigs fed added corn oil. Serum alkaline phosphatase was greatly reduced (P< .01)after 4 and 6 weeks in pigs fed the low-Zn diets, but there was no effect of added corn oil on this constituent despite the absence of parakeratosis. In experiment 2 no parakeratosis was observed, even when the Zn concentration was reduced to 22 ppm by replacement of corn with glucose. The failure to produce parakeratosis was probably associated with the older age (8 weeks) at the beginning of the experiment, which allowed body storage of Zn from the Zn-fortified postweaning diet. There was no significant effect of level of Zn or corn oil on weight gains, but the addition of 154 ppm Cd to the low-Zn diet resulted in reduced weight gains during the first 3 weeks and subsequent steady weight loss. The addition of 52 ppm Zn to the high-Cd diet resulted in less severe weight loss. Serum alkaline phosphatase was significantly (P<.01) reduced after 4 and 6 weeks in pigs fed low-Zn diets, regardless of the corn oil or Cd level. The failure of Cd to produce symptoms of Zn deficiency in pigs fed low-Zn diets despite severe weight loss indicates that its main action in the pig is not an antagonism of Zn.