Effects of Using Ground Eggshells as a Dietary Calcium Source on Egg Production Traits, Hatching Performance and Eggshell Ultrastructure in Laying Hens

A 10 wk trial was conducted to investigate the effect of using ground, sterilized eggshell as a calcium source in the diet of laying hens. Egg production, egg and eggshell quality, hatching characteristics and eggshell ultrastructure were evaluated. A total of 144 hens aged 25 wk were housed in floor pens, located in a conventional open-sided layer shed. The birds were randomly divided into three groups, each group represented by four replicates, consisting of twelve birds each. Group 1 (Control) was provided with a layer ration that contained all the calcium carbonate as fine limestone, whereas Groups 2 and 3 were placed on a layer diet with 50 and 100%, respectively, of the limestone substituted with ground eggshells. The birds were given free access to food and water, and exposed to a 16L:8D photoperiod daily. Throughout the entire 10 wk test period, body weight, egg production, egg weight and egg quality of the three bird groups were not significantly (P > 0.05) different. Eggshell weight, eggshell thickness and egg specific gravity were not affected by the treatment diets. Hatching performance was determined at 4 and 8 wk after feeding the experimental diet. There were no significant differences in average fertility, hatchability, egg weight loss, chick yield and hatchling weight among the bird groups. In addition, there were no significant differences between treatments in growth and livability of chicks aged 1 wk. Scanning electron microscopy was used to study the morphology of the eggshell. The photographs illustrated a little variation in the formation of the mammillary layer of the shell produced by hens fed diets containing eggshell calcium. Neither density nor diameter of the mammillary knobs were affected by the treatments. The results indicated that eggshells can be fully utilized as a calcium source in layer diets without detrimental effects on productive performance, fertility, hatchability, chick quality and the fine structure of the eggshell.