Performance and Immunocompetence of Broilers As Affected By Dietary Zinc, Protein Level and Phytase Supplementation During Summer Season

A. A. Ghazalah , A. S. Abd El-Hakim*, A. M. M. Atta, Amira M. Refaie*

Animal production Deptartment, Faculty of Agriculture, Cairo University, Giza, Egypt.

 *Animal Production Research Institute, Agriculture Research Center, Dokki, Egypt.

 Abstract: Two experiments were performed under hot environmental temperature of summer season in Egypt, where, environmental temperature ranged between 31 to 36 OC and relative humidity from 50 to 59%. A total number of 224 (Exp.1) and 288 (Exp.2) unsexed week old Hubbard broiler chicks were used. The birds were randomly distributed into 7 treatments for (Exp.1) and 9 treatments for (Exp.2) of 32 chicks each, in 4 replicates. Two sources of zinc (Zincoxida as inorganic and Biozink as organic form) were used each at 3 levels being 40, 80 and 120 mg Zn/kg (Exp.1) in addition to the control diet which contains 40 mg zinc/kg diet. In the second experiment, the best level of each source of zinc obtained from Exp.1 were used at two levels of dietary protein (recommended and low) with or without phytase supplementation (500 FTU/kg) in addition to control group. The recommended protein levels were 21 and 19% while the low levels were 19 and 17% for starter-grower and finisher periods, respectively.In both experiments, the chicks were fed the control diet for 7 days then distributed into different treatments. Although Biozink (the organic form) added at 80 mg/kg recorded significantly the highest digestibility of CP and NFE however, OM digestibility did not affected by zinc source and level. Comparing to the control group, Zincoxida at 40 mg/kg and Biozink at 80 mg/kg recorded significantly better values of live body weight and feed conversion. Both treatments decreased significantly respiration rate and recorded the highest titer against SRBC. Addition of phytase at 500 FTU/kg of diet with recommended or low CP level and supplemented with either Zincoxida at 40 mg/kg or Biozink at 80 mg/kg recorded significantly better values of CP, CF, NFE and OM digestibility, as well as better values of body weight gain and feed conversion, compared to the control. However, those fed low CP diets exhibited significantly lower respiration rate and higher antibody production, compared to the control. Economically, chicks fed the recommended CP diet supplemented with Zinoxida at 40 mg/kg (Exp.1) or those on the low CP diet with Zincoxida at 40 mg/kg and phytase at 500 FTU/kg (Exp.2) gave the best efficiency values under summer season condition in Egypt.