INFLUENCES OF CALCIUM LEVELS WITH LIMESTONE PARTICLE SIZE ON LAYING PERFORMANCE , AND EGGSHELL QUALITY TRAITS OF LAYERS

Abstract
The current study estimated the influences of nutritive calcium levels besides limestone particle size upon performance , egg production and egg quality in first-cycle of Golden Montazah layers. Experimental scheme was completely randomized in 3x4 factorial arranging (three Ca levels – 2.8, 3.0 or 3.2%, in addition four particle size distributions – (100% fine" F" , 50% fine plus 50% coarse "C" , 25% "F" and 75% "C", or 100% " C" ) Totalizing 12 treatments including three replicates with eight birds each. Limestone size was ranged from fine (F >0.6 mm) to coarse ( 1.9 <.C < 2.8 mm). There was a significant influence of dietary calcium levels with particle sizes or the interaction between the two influences on feed intake (g/hen/day ), egg production % , calcium intake and feed conversion. Particles of limestone were significant effect on eggshell quality including density , shell breaking strength, thickness, eggshell (%) as well as EWSA . Eggshell breaking strength was enhanced when replacing fine limestone by 75% and 100% of coarser limestone substitutions . Shell thickness was significantly higher in 3 or 3.2% Ca groups compared with 2.8% Ca group. The main effect of Limestone particles size generally improved egg shell quality with increasing coarsity inclusion level. Limestone particle size significantly affected internal egg quality traits. Regardless of calcium levels , while limestone particle size is consider , best performance results of egg production, eggshell quality plus some of internal egg quality were obtained by replacing fine limestone by 75% and 100% of coarser limestone particle size . In conclusion, the addition of calcium at level (3.0 - 3.2%) with supplying of coarse limestone (1.9mm< C <2.8mm) by 75 - 100% improves the performance of laying hen