Effects of dietary zinc supplementation on hen performance, ammonia volatilization, and nitrogen retention in manure

This investigation was undertaken to evaluate the effects of dietary ZnSO4 supplementation on ammonia volatilization and nitrogen retention in hen manure. One hundred twenty, 45-wk-old commercial Leghorn laying hens were sequentially fed diets with 1000, 2000, and 3000 ppm Zn as ZnSO4 (Zn-1000, Zn-2000, and Zn-3000), then followed by two control dietary periods with 114 ppm Zn (Control-1 and Control-2) for a total of five consecutive eight-day experiment periods, respectively. When hens were fed the 1000 and 2000 ppm Zn treatment diets, room ammonia levels were significantly reduced compared to the control diets. Dietary Zn treatments reduced the decomposition of uric acid, resulting in an increase in manure total-N retention compared to the control fed birds. The 1000 ppm Zn supplement had no adverse effects on hen body weight, feed consumption, egg production, egg weight, albumen height, or shell thickness. However, hens fed the diet containing 3000 ppm Zn had significantly depressed body weight, feed consumption, egg production, egg weight, and shell thickness. Zinc levels of egg contents increased linearly as dietary Zn levels increased. These levels in eggs would not be a problem for human consumption because these are much less than the daily Zn recommended dietary allowance. Although land application of such manure will not cause environmental problems or crop toxicity, proper monitoring of soil and crop Zn levels and effective nutrient management planning would be well advised.