EGGSHELL CALCIUM EFFECTS ON EGG QUALITY AND CA DIGESTIBILITY IN FIRST-CYCLE OR 3RD-CYCLE LAYING HENS

Dried eggshell products from two egg breaker plants were compared to v arious sources (limestone and oyster shell) and combinations of fine- and large-particle calcium in two age groups of laying hens: third-cyc le Babcock B300 and first cycle DeKalb Deltas. Particle size measureme nts of the two dried eggshell products indicate a size pattern similar to fine- or medium-particle limestone. The amount of large (> 4.0 mm) particles found in the eggshell products were minimal, less than 5%. Dried eggshell as the sole calcium source compared to combinations of limestone and oyster shell showed no significant effect on feed intake , egg production, or egg weight in the first-cycle hens. Rate of egg p roduction was decreased in one of the eggshell treatments in the older third-cycle hens without any change in feed consumption or egg weight . Egg specific gravity decreased more in older hens fed the eggshell a nd fine-particle limestone calcium sources. Egg specific gravity was i mproved when the diet included large-particle calcium from either lime stone or oyster shell. Dietary calcium digestibility was greatest for the fine limestone and ground eggshell treatment groups. Calcium from eggshells is highly available to support egg production in laying hens but should be combined with a large-particle calcium source to suppor t optimal eggshell quality.