A 2X4 factorial design experiment was performed including two sources of zinc (inorganic or organic). The inorganic Zn was provided as zinc oxide 72% and organic Zn was provided as Bioplex Zn, a chelated Zn proteinate that contained 10% Zn (Bioplex, Alltech Inc). The inorganic or organic zinc were added to the basal diet containing 22.21 mg zinc /Kg diet completed to 35(NRC, 1994), 70, 105 and 140 mg Zn / Kg diet. A total number of 240 laying hens and 24 cocks of Inshas strain (local strain) of 24 weeks old was used to study the effect of sources and levels of Zn addition to birds rations on their productive performance, reproductive traits, immune response to SRBC and economic efficiency. Birds were randomly distributed into eight equal groups (30 hens and 3 cocks each). Each group was subdivided into three replicates (10 hens and 1 cocks each) laying hens of each group nearly equal in average body weight (1430.55± 19.95) and average daily egg production. The experiment period extended from 24 to 36 weeks of age, during hot summer season (from June to September, 2008). The average minimum and maximum ambient temperatures ranged between 23.6 and 34.7 0C, relative humidity from 31.8 to 80.7% and temperature-humidity index (THI) from 21.64 to 33.52% underInshas, Sharkia Province, Egypt.
Results obtained showed that feed conversion, egg production% , egg mass )24 - 28 weeks of age(, semen ejaculate volume (ml), percentages of sperm motility and sperm-cell concentration and antibody titer against SRBC'S were improved significantly (P<0.05) ,while dead spermatozoa(%) were decreased significantly (P<0.05) for birds fed diets contained organic zinc as compared to those fed zinc oxide. Laying hens fed diets contained 105 mg Zn/Kg diet recorded best values of feed conversion, egg production(%), egg mass, fertile eggs (%), hatchability/total eggs (%) and hatchability/ fertile eggs (%) values while the lowest values were recorded with layers fed diets containing 35 mg Zn oxide /Kg diet. Inshas cocks fed 105 mg Bioplex Zn / Kg diet showed the highest sperm cell concentration and lowest in dead sperm percentages as compared with other treatment groups which, improved the positive and direct effect on the viability of sperm and consequently affect the rate of cock fertility. Heamoglobin, serum zinc and yolk zinc were higher (al most significantly) for layers fed diets contained at levels 105 or 140 Zn mg/ Kg as compared with those fed other levels of Zn at the end of experimental period. Generally, zinc from Bioplex Zn improved titer against SRBC'S better than zinc from Zn oxide.
In conclusion, diets supplemented with organic zinc at the level of 105 mg Zn/ Kg diet improved most physiological productive and reproductive traits of Inshas strain under hot summer condition in Egypt.