الفهرس 
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Calcium homeostasis in the laying hensOnly 14 pages are availabe for public view
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Abstract
This study was conducted at the Poultry Research Farm, Faculty of Agriculture, Assiut University from January to April 2018. The aim of the work was to study the effect of split feeding system on egg production and egg quality of Dandarawi layers at their late phase of egg production cycle.
A total of 100 Dandarawi Layers (12 months old) were divided into two groups (50 birds each) and housed in 10 floor pens. Each pen was supplied with laying nest of 4 holes each. Each group was divided into 5 replicates (10 hens each). The first group was kept as control and fed one diet throughout the day (regular diet with optimum level of energy, protein and calcium). Whereas, the second group was fed according to split feeding system by having access to two diets throughout the day. The first diet (high energy, high protein and low calcium) offered from 6 am to 6 pm, and the second diet (low energy, low protein and high calcium) offered from 6 pm to 6 am. The diet offered throughout the daily hours was higher by 10% energy, 23 % protein and lower by 50% calcium than the diet offered throughout the night hours. The experiment lasted for four months at the layers’ age between 12 to 16 months. body weight, body weight change, feed consumption, feed conversion ratio, egg production traits, egg quality traits (external egg quality- internal egg quality) were recorded, estimated or calculated.
The results could be summarized as follows:
• Split feeding system did not result in any significant change in BW during the experiment period from 12 to 16 month of age.
• Feed consumption was significantly decreased by 16.1 % and feed conversion ratio was significantly improved by 25 % by following split feeding system.
• Split feeding system had led to saving of 20 % of the consumed feed cost.
• Egg number produced by split fed hens increased by 9.47 % in the overall period than their controls.
• Egg mass produced by split fed group exceeded the control group by 9 %.
• Egg laying rate of the split fed group did not significantly differ from the control group; however, it was numerically higher (49.34 % vs. 45.06 % ).
• There were no significant differences in egg external traits (specific gravity, index) between split feeding and control groups.
• No significant differences were detected for yolk traits (weight, percent , index , color) between the split fed and control groups.
• Albumin weight, albumin height and Haugh units of the eggs produced by split-fed hens were significantly higher than those produced by their controls
• Although, egg shell weight, percent, thickness and breaking strength were not significantly different from control for the overall period (12-16 months); however they were significantly better for the egg produced by split-fed hens in the fourth month (15-16 month).
• Shell weight per unit surface area (SWUSA) was not significantly different in the eggs produced by both groups.
• Although , there was no significant influence of split feeding on shell %, eggshell thickness, eggshell breaking strength and shell weight per unit surface area (SWUSA) (mg/cm2) during the overall experimental period ; however , there was a significant improvement in their characters at the fourth month. Therefore, it may be conducted that split feeding system may have accumulated effect on eggshell traits that may be more effective and more obvious at the very end of the laying cycle.
Moreover, the effect of split feeding system on egg shell quality may be more pronounced in commercial layers that produce much more eggs than Dandarawi layers.
Also, it would be expected that the response of local strains to split feeding on shell quality might be slight since they possess genetically stronger eggshell than the commercial layers.
Eventually , relying on the results of this study, it could be concluded that split feeding of Dandarawi layers at 4 months of their late phase of egg laying cycle has led to significant decrease in feed consumption by 16 % , improve in feed conversion ratio by 25 % , and saving in feed cost by 20 %. Also, it showed a trend toward increasing egg number by 9.47 % , and increasing egg mass by 9 %. Moreover, it also has resulted in some improvements in eggshell quality at the very late phase of laying cycle (15-16 month of age).