Improved Limestone Retention in the Gizzard of Commercial Leghorn Hens

Abstract

Dietary limestone solubilization in laying hens improves if retention time is prolonged in the gizzard. To determine the minimum dietary particle size of limestone that can be retained in the gizzard, equal quantities of four different sizes of limestone particles were mixed with a layer diet devoid of limestone and fed to molted hens for 1h. Limestone particles retained in crop, gizzard and intestine were recovered and separated into the four test particle sizes.A greater (P < .001) quantity of limestone was recovered from the gizzard when a 5g mixture comprised of four particle sizes (1.25g each) was fed than when 5g of the smallest (.71 to .84 mm) size particle was fed, indicating that small particles pass through the gizzard relatively quickly. The comparison of amounts of four test particle sizes recovered from gizzard when fed in equal proportions revealed that significantly greater quantities of medium, large and extra large sized limestone particles were recovered than the small particles. In the intestine, however, a significantly higher quantity of small particle limestone was recovered compared to the three larger particle sizes. This retention pattern of limestone particles in the gizzard and intestine indicates that the medium particle size (average size of 1.01 mm) is the minimum particle size required to significantly improve its selective retention in the gizzard of commercial leghorn hens.