Zinc Toxicity in Ruminants. II. Effect of High Levels of Dietary Zinc on Gains, Feed Consumption and Feed Efficiency of Beef Cattle

Abstract

Three experiments were conducted to determine the zinc toxicity threshold in feeder cattle and to characterize the toxicity symptoms. Zinc levels of 0.9 gm. per kg. of diet provided as ZnO caused reduced gains and lowered feed efficiency. Zinc levels of 0.5 gm. per kg. of diet and lower had no detrimental effects. Although there was no significant difference in the toxicity threshold between steers and heifers, the magnitude of the effect on steers was greater as the dietary zinc levels were increased. Zinc levels of 1.7 gm. per kg. of diet and higher caused reduced feed consumption and depraved appetite, characterized by excessive salt and other mineral consumption and wood chewing.