The Effect of Different Dietary Calcium Levels on Calcium Metabolism in Laying Hens

Abstract The experiment was carried out on four groups of Hy-Line var. Brown hens (n = 350 each) fed on diets which provided 2.49, 3.07, 3.78 and, respectively, 4.15 g% calcium (Ca) during the laying period. Consequently, mean daily Ca intake was 2.74, 3.38, 4.16 and 4.60 g/cap., respectively. Ca metabolism was assayed at 20 weeks of age (start of the laying), 36 weeks of age (the peak of the laying) and 68 weeks (the end of the laying period). A significant part of the ingested Ca was not absorbed. The percentage of Ca exonerated by feces was higher at the start of the laying and lowers in the peak of laying and at the end of the laying period. The amount of Ca exonerated as unabsorbed Ca increases as the amount of ingested Ca increases inside of each age level. It was found also an increase of the Ca content of the egg shell according the Ca intake statistically significant (P<0.05) in 36- and 68-wk.-old hens, but not in 20-wk.-old hens. Blood plasma Ca showed significantly higher values in 3.38-, 4.16- and 4.60-g/day-Ca-intake groups when compared by 2.74-g/day-Ca-intake group (P < 0.05) but the level of increasing showed lowest values in hen groups with highest intake of Ca. The daily eggshell Ca export strongly correlates with the amount of daily Ca intake in 36-wk.-old hens and 68-wk.-old hens: r = +0.72 and +0.84, respectively, but no correlation was found in 20-wk.-old hens (r = -0.74, negative correlation). The results showed a limited physiologic capacity of the Ca absorption in hen, the Ca surplus being lost. Dietary Ca level should be closely correlated with the laying level of hens.