Effect of zinc toxicity in laying white leghorn pullets and hens

Two experiments involving 124 Single Comb White Leghorn (Hy-Line) laying pullets and hens were conducted to determine the effect of zinc toxicity on bird performance. Twenty milligrams of zinc per gram of diet fed for 5 days significantly lowered fertility and hatchability of pullet eggs collected 14 to 28 days after the 5-day zinc feeding period. Zinc significantly depressed body weight on the day 5 of zinc feeding and significantly lowered egg poroduction from 0 to 4 weeks of test. Egg production from 4 to 12 weeks, feed conversion from 0 to 12 weeks, final body weight, and livability were not significantly affected. Hens fed the supplemental zinc for five days had depressed egg production from 0 to 4 weeks. Egg production from 4 to 12 weeks, feed conversion, final body weight, and livability were not significantly affected. Compared to their respective controls, 2% supplemental zinc fed for 5 days significantly improved hen but not pullet egg weight. Hen eggs collected 28 days after hens received the zinc diet contained significantly less potassium, copper, and zinc than the controls.