Zinc supplementation: its effect on egg production, feed conversion, fertility, and hatchability.

Studies were conducted over four layer years using Single Comb White Leghorn hens, 24 to 68 weeks of age, to observe the effects of zinc supplementation of a corn-soybean meal layer ration on egg production, feed conversion, fertility, and hatchability. Pullets were housed in floor pens; 20 birds per pen. New Hampshire cockerels were used as sires. Treatments were the basal corn-soy-based diet (28 or 34 ppm zinc by analysis) with the following supplemental zinc levels (as the carbonate): 0, 10, 20, or 40 ppm. Feed, water, and crushed oyster shell were supplied ad libitum in all trials. No consistent production effects due to zinc supplementation were observed. Egg production, feed intake, and feed conversion were not improved by zinc supplementation. Fertility and hatchability, likewise, were not improved by zinc supplementation. The chicks produced showed no significant differences in 3-week body weights. However, the chicks produced from hens on the 28 ppm zinc (control) diet showed an increased incidence of zinc-related feather fraying. There was a significant (P less than .05) increase the first two laying trials and a numerical increase the last two trials. Thus it appears that 28 ppm of zinc, naturally supplied, is adequate for egg production, fertility, hatchability, and growth of progeny.