الفهرس 
Introduction
Effect of dietary iron on layer performance and egg iron contentOnly 14 pages are availabe for public view
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Abstract
The current experiment was conducted to evaluate the effect of high dietary levels of trace elements (iron and zinc) and vitamins (A and E) single or combined on productive laying performance in terms of feed consumption, feed conversion and egg production as well as egg traits. In addition, it demonstrated the patterns of minerals and vitamins deposition in the egg yolk.
A total number of 130 Mandarah laying hens (Egyptian local strain) at 24 weeks of age were randomly distributed into 13 equal groups, each of 10 hens. Birds in the first group (control) were fed on ad libitum basal control diet containing 16.62% crude protein and 2801.4 ME/Kg diet (50mg/kg Fe, 35mg/kg Zn, 3000 IU vitamin A/kg and 10 mg vitamin E/kg diet) provided through the vitamin and mineral premix. For birds in the second and third groups, ferrous sulphate (22% Fe) were added to the basal control diet to contain 100 and 200 mg Fe/kg diet, respectively. In the fourth and fifth groups, birds were fed on the basal control diet but fortified with 70 and 140 mg Zn/kg diet respectively in the form of Zn oxide (80% Zn). Diets containing 15,000 and 30,000 IU vitamin A/kg were fed to hens in groups 6 and 7, while birds in the 8th and 9th groups were fed on the basal diet supplemented with 50 and 100 mg vitamin E/kg diet. In 10th and 11th groups, hens were fed on basal experimental diet supplemented with a combination of high dietary levels of both vitamin A and E (15,000 IU vitamin A and 50 mg vitamin E/kg in group 10 and 30,000 IU vitamin A and 100 mg vitamin E/kg in group 11). Birds in group 12 were fed on basal diet containing 100 mg Fe, 70 mg Zn, 15,000 IU vitamin A and 50 mg vitamin E/kg, while the diet of laying hens in the 13th group was fortified with 200mg Fe, 140mg Zn, 30,000 IU vitamin A and 100 mg vitamin E/kg. Weekly and cumulative feed intake, egg number, weights, mass, and feed conversion of laying hens fed different experimental diets during the three experimental period intervals (24-28, 28-32, and 32-36 weeks) and during the whole experimental period (24-36 weeks)were recorded.
During the whole experimental period (24-36weeks), results revealed that:
• Feed intake of layers fed high levels of Fe (100&200mg/kg diet) and Zn (70 &140 mg/kg diet) was decreased by about 2.39%, 3.82%, 0.93% and 1.24% respectively in comparison to control.
No clear difference in the feed intake between hens in the control group and those fed diets supplemented with high levels of vitamin A (15,000&30,000 IU/kg diet) and vitamin E (50& 100mg /kg diet) in groups 6, 7, 8 and 9. The highest feed intake (8089 g) was noticed in the sixth group which fed on diet supplemented with 15,000 IU vitamin A/kg diet, while layers in the 3 rd group fed on diet supplemented with 200 mg vitamin E/kg recorded the lowest value (7711g).
• Egg number and egg production were increased in all treated groups. The best egg number value and egg production percentage (61.1&72.74% ) were recorded in layers in the fifth group fed on diet supplemented with 140 mg zinc /kg, followed by the eighth group which fed on diet supplemented with 50 mg vitamin E/kg (60.9&72.5% ) compared to control (57.2&68.1%).
• No significant (P≤0.05) differences were observed in egg weights between layers in all the treated groups and control.
• Egg mass of layers were significantly increased in all the treated groups in comparison with control. The highest egg mass value (2711g) was noticed in layers fed on diet supplemented with 15,000 IU vitamin A/kg in the sixth group, whereas the lowest value (2560g) was observed in layers fed on diet supplemented with 200 mg Fe/kg in the third group.
• The best feed conversion ratios were scored in layers fed on diets supplemented with 140mg Zn/kg , 100mg Fe/kg, and 50mg vitamin E/kg (2.93, 2.94, and 2.95 respectively)
• Eggshell percentages were significantly higher in layers fed on diet supplemented with 70mgZn/kg than those fed diet supplemented with 140mg Zn/kg. Egg yolk percentages were significantly increased in layers fed on diet supplemented with vitamin E (50&100mg/kg), while albumin percentages were decreased.
• Results revealed that increasing dietary Fe level from 50 to 100 and 200 mg/kg (P<0.05) improved yolk iron content by 12.96 % and 15.82 % respectively, compared to control. The highest concentration of Fe in egg yolk was found in groups 12&13 (135.3& 134.3 mg/100 g yolk). Addition of high levels of vitamin A and vitamin E in single or in combination had no significant (P<0.05) effect on yolk Fe concentration.
• The concentration of Zn in egg yolk was significantly (P<0.05) increased in the eggs of hens fed diets supplemented with 70 & 140 mg Zn/kg by about 6.46 and 9.96% than that recorded by control. An improvement in egg yolk Zn content was observed in groups 12 and 13 (71.0 & 69.0 mg/kg yolk) compared with control (67.0mg/kg yolk). Hens fed diets fortified with 100 & 200 mg Fe/kg recorded the lowest values of yolk Zn content (67.0 &66.3 mg/kg yolk). The levels of yolk Zn of the vitamin A & E supplemented groups (6&7, 8&9, 10&11) were close to the level of the control one.
• Egg yolk retinol was increased from 27.62 IU/g in the un-supplemented control group to 37.34 & 39.66 IU/g (35.19% and 43.59%) for hens fed 15000 and 30000 IU vitamin A/kg diet respectively (groups 6&7). Increasing the level of dietary vitamin E in the 8th and 9th groups showed a trend to reduce the yolk retinol content by about 4.34, 8.76 % for 50 and 100 mg vitamin E/kg diet in comparison with control group. The combination between vitamin A and E (groups 10 and 11) and also Fe, Zn, vitamin A & E (groups 12 and 13), a significant (P<0.05) increase in egg yolk retinol was observed in the four groups (36.48, 38.37, 35.13 and 37.89 IU/g yolk) compared to control (27.62 IU/g yolk). No significant (P<0.05) differences in the egg yolk retinol content were observed among Fe and Zn supplemented groups (2, 3, 4 and 5) and control.
• Egg yolk α-tocopherol values were significantly (p≤0.05) higher (171.12, 208.17, 210.18, 159.18, 212.19 and 180.5 µg/g of yolk) in vitamin E supplemented groups (8, 9, 10, 11, 12 and 13) compared to control (45.93).
• from the obtained results, it is recommended that supplementation layer hen diets with 200mg Fe and140 mg Zn/kg to give Fe and Zn/kg to give Fe and Zn enriched eggs. Also, addition 15000 IU vitamin A and 100 mg vitamin E/ kg layer diet enriched their eggs by these vitamins.
The current experiment was conducted to evaluate the effect of high dietary levels of trace elements (iron and zinc) and vitamins (A and E) single or combined on productive laying performance in terms of feed consumption, feed conversion and egg production as well as egg traits. In addition, it demonstrated the patterns of minerals and vitamins deposition in the egg yolk.