الفهرس 
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Abstract
The present study was undertaken to determine the effects of feeding diets containing high nutrient concentrations on laying performance and egg quality of Bovans White laying hens during the summer season in Egypt. Two hundred hens were randomly distributed into five equal experimental groups, each composed of five replications. Hens were maintained at community cages (8 birds/cage) and subjected to similar hygienic and managerial conditions. A corn-soybean meal-based diet, containing 17.40% crude protein, 2880 kcal/kg of metabolizable energy, 4.35% calcium, 0.43% nonphytate phosphorus, 0.84% lysine, 0.41% methionine, and 0.70% methionine plus cysteine, was formulated in mash form and used as a control. The concentration of nutrients was increased to be 102.5, 105, 107.5 and 110% of those present in the control diet through some dietary manipulations, thus five mash experimental diets were formulated and fed to hens. The laying performance was evaluated in terms of egg production rate, egg weight, daily egg mass, daily feed intake and feed conversion ratio during three 28-day periods, from 44 to 56 weeks of age. An egg quality test was also performed to determine the effects of feeding the high-nutrient-density diets on egg components and some exterior and interior parameters of egg quality at the last week of study. At the first 4-week period, feeding the high-nutrient-density diets had no significant effect on laying performance of hens but daily feed intake was inconsistently affected. At the second period, hens fed high-nutrient-density diets achieved significantly higher egg production rate (EPR) and daily egg mass (DEM) compared with the control group while egg weight (EW), daily feed intake and feed conversion ratio (FCR) were not affected. At the third period, hens fed 105 and 107.5% diets consumed significantly more feed and displayed higher EPR and DEM than those of other dietary treatments but EW and FCR were not affected. Feeding the high nutrient density diets produced significant improvements in egg weight, yolk index and Haugh units compared with their control counterparts while percentages of egg components, shell weight per unit surface area (SWUSA), egg shape index and yolk color score were not affected. It is concluded that increasing dietary nutrient density up to 110% of the recommended requirements of Bovans White laying hens can positively affect some egg quality traits but had inconsistent effect on their productive performance under Egyptian summer conditions.