Findings on the Calcium Metabolism in Organisms of Laying Hens

This study was conducted to investigate the effects of various amounts of calcium in the diet on the activity of digestive enzymes in the duodenum and blood plasma of laying hens. There was recorded a reverse relation between the activity of duodenal digestive enzymes with trypsin in plasma and the amount of calcium in the biological fluids. When the amount of calcium in the diet of birds increased from 3.0 to 3.4%, crude fat rose by 5.0%, and when increasing the calcium content up to 5.4%, the digestibility tended to decrease by 0.5% compared to the optimal value. Digestibility of crude cellulose decreased with the increase of calcium in the diet of laying hens. Despite the same digestibility of crude protein in the intestine, the optimal content of calcium in the diet of chickens (3.4%) was achieved by maximizing the use of nitrogenous substances exceeding values of other groups by 30.0 (3.0% calcium) and 25.7% (5.4% calcium). When increasing the amount of calcium in the diet, most of the calcium excreted with litter, there was also a growing excretion of calcium through eggs. Thus, the data obtained can serve as the basis for the development of feed additives with different levels of calcium in them.