Effect of Feeding Thiouracil to Swine on the Rate of Gain and Weight of the Thyroid Gland

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Abstract
Addition of 0.25% thiouracil to the ration of growing Hampshire and Duroc Jersey swine depressed the growth rate. The controls made a total gain per pig of 74 lb. as compared to 38 lb. by the animals fed thiouracil in a 51-day period. Thiouracil did not appear to reduce the rate of gain during the first 9-18 days of the feeding trial, but a progressive reduction in the rate of gain was observed thereafter. The feed intake and feed efficiency was also lower for those animals fed thiouracil. The Duroc Jersey hogs consumed a larger amt. of feed than the Hampshires and attained higher gains as well as a higher efficiency of feed utilization. Carcass studies failed to reveal any gross differences in the commercial cuts, between the control animals and those fed thiouracil. Ingestion of 0.25% thiouracil in the ration significantly increased the wt. of the thyroid gland. 17 days after cessation of treatment the increased wt. of the thyroid still persisted, but the wt. of the gland of the groups fed thiouracil was lower than observed for animals killed 10 days after the feeding of the drug was discontinued. Histological examination of the thyroid glands of the animals that had been fed thiouracil showed an increase in height of the epithelium, greatly reduced colloid content, and an increase in size of the follicles.