Effect of Feed Additives on Calcium Requirement, Calcium Retention and Shell Calcification in the Laying Hen

Calcium retention studies were undertaken with 14-month-old Single Comb White Leghorn hens at summer temperatures to determine the optimal ration calcium level for maximum retention and shell calcification. Thereafter, the effects of three ration additives, arsanilic acid (Pro-Gen) 90 ppm, neomycin sulfate (Pre-mix) 200 ppm, and bacitracin (Fortracin) 200 ppm, on calcium retention and shell quality were studied at near-optimal ration calcium (2.66%). Results indicated that 2.66–2.70% ration calcium was adequate for hens laying at rates of 75–80%, but a somewhat higher level (e.g., 3.15%) will ensure better quality eggshells. The hens receiving a level of 2.40% ration calcium displayed a significantly higher (P < 0.01) percent calcium retention but a significantly lower (P < 0.01) eggshell quality than did the hens receiving the 3.15% ration calcium. The groups fed 2.66 and 3.15% calcium displayed significantly higher (P < 0.05) calcium retention per egg laid than did the groups fed 2.40 or 2.91% ration calcium. Calcium retained per egg laid was increased by the additives, but the increases were not significant (P < 0.05).