The influence of feeding diets containing different calcium-phosphorous ratios on the laying hen

Six experiments were conducted to determine the influence of feeding diets containing different calcium-phosphorus (Ca:P)ratios at different times on the laying hen. Feeding a diet containing 0.75% P from 6 a.m. to 11 a.m. and a diet containing 1.50% P from 3 p.m. to 8 p.m. decreased serum calcium in three or four experiments and decreased specific gravity of eggs in four of four experiments, when compared to that of the birds fed the control diet which contained 0.75% P during both time periods. Specific gravity of eggs from hens fed a diet containing 0.75% P from 6 a.m. to 11 a.m. and a diet containing 0.33% P from 3 p.m. to 8 p.m. was increased in three of four experiments. Although the differences are not significant, with one exception, the trend in the experiments indicate that the level of P in the diet and time of intake can influence shell quality and serum calcium. The dietary treatments had no significant influence on feed consumption, egg production or egg weight during any of these experiments. It was postulated that the adverse or beneficial effect on specific gravity of eggs and serum calcium as a result of feeding diets containing various CaP ratios was due to the influence on calcium absorption and/or bone resorption.