EFFECT OF LIMESTONE SIZE PARTICLES ON IMPROVING EGGSHELL AND BONE PHYSICAL AND MECHANICAL CHARACTERISTICS AT THE PEAK OF EGG PRODUCTION IN GOLDEN MONTAZAH CHICKEN

Abstract

This study investigated the influence of different particle sizes of limestone in Golden Montazah layers diets on physical and mechanical properties of egg production, eggshell quality and breaking strength of tibia from 32 to 44 weeks of age. Limestone consisted of fine (F> 0.6 mm) and coarse (C>2.8mm-4.5mm). All hens take a basal ration of the same composition. The differences between the four equal groups were in the replacement percent of fine pulverised limestone by granular limestone, of coarser particle size. The control group takes the basal diet with only pulverised limestone as a calcium supplement. In the diet ration of the second group, 60% of the pulverised limestone was replaced with granular limestone, in the third group percent 80 % and in the last group 100% of fine limestone replaced with coarse particles of limestone. Significantly higher breaking force (31.69N), shell weight (5.65 g), shell thickness (0.46 mm) were found for eggs from the fourth group of hens than for eggs from the control group (29.46 N; 5.33 g ; 0.37 respectively). Tibia breaking strength was significantly higher (350.66 N) than those in control group (252.82 N). The results obtained in our investigation showed some possibilities of eggshell quality improvement using limestone of coarser particle size as a Ca supplement in the hen diet. Replacing 60-100% of fine limestone by coarser particle size limestone had positive effects on eggshell quality.