Effects of selenium supplementation on growing-finishing swine

Data was collected on forty-eight Duroc pigs during the fall of 1974 at the University of Tennessee Agricultural Experiment Station, Knoxville, Tennessee to determine the effect of selenium supplementation on growing-finishing swine. Pigs were randomly allotted, six pigs per pen in eight pens, with four treatments and two reps per treatment. Treatment rations were control, control + Zn-Pro, control + Se (0.1ppm), and control + Zn-Pro + Se. Pigs were weighed every two weeks from time on test to market weight of 220 pounds (weighed weekly as they approached 220 pounds). When pigs were weighed, feed consumption was measured to determine feed efficiency. A blood sample for each pig was taken before test, and every twenty-eight days thereafter to determine the percent in vitro red blood cell uptake of ⁷⁵Se and the stable selenium in the whole blood and blood plasma. It was found that there was a 4% decrease in the hematocrit reading after incubation as compared to freshly drawn pig blood. This was attributed to the dilution of the dosing solution that, when added to the sample, caused alterations making the erythrocytes more permeable causing shrinkage. The percentage in vitro ⁷⁵Se RBC uptake was not affected by treatment. Plasma levels for pigs supplemented with selenium increased throughout the experiment, being greater than the unsupplemented groups. But, this increase was only slight and non-significant for treatment means. Whole blood selenium increased about 0.03 to 0.05 ppm for supplemented selenium pigs for the first month, with no increase by the unsupplemented pigs. But, this increase was overcome the second month by the unsupplemented pigs as they reached levels comparable to the supplemented pigs. By statistical analysis, these treatment means were non-significant. No increase was observed in average daily gain or improvement in feed efficiency due to selenium or zinc proteinate supplementation. Selenium blood levels increased to similar levels, whether selenium was added to the ration or not. Therefore, it is possible to assume that the basal ration contained sufficient levels of selenium, and that the addition of 0.1 ppm selenium to this ration had no harmful effect on the pigs, and gave no advantage to the growing-finishing swine.