عنوان مقاله [English]
An experiment to compare different sources and levels of zinc on carcass, tibia, antioxidant status of serum, meat quality and immune system on 480 broilers in a completely randomized design with a factorial arrangement (4 × 3) with five replications and 8 chicks were performed in each replicate. Zinc sources included sulfate, oxide and organic complex of zinc and methionine levels were zero, 60, 120 and 180 mg/kg feed. At the end of the experiment, the data were analyzed using the GLM procedure of SAS software and the Tukey test was used to compare the means with a 95% probability level for the main effects (zinc sources and its levels) and the interactions between them. The effect of different levels of zinc on weight percentage of spleen, pancreas and bursa fabricius was significant (P<0.05). The results showed that the effect of source and level of zinc on serum malondialdehyde was significant; So that the treatment containing organic sample of zinc had the lowest amount of serum malondialdehyde and also increasing the level of zinc application in the diet caused a significant decrease in serum malondialdehyde. Meat moisture in the treatment containing organic zinc sample had a significant increase compared to oxide treatment, also higher levels of zinc caused a significant increase in meat moisture (P<0.05). Water holding capacity and pH indices were not affected by different sources and levels of zinc. As with the results obtained for serum malondialdehyde, the amount of malondialdehyde in meat was affected by experimental treatments so that the use of organic zinc sample as well as the use of the highest level of zinc in the feed (180 mg/kg) significantly (P<0.05) reduced the concentration of malondialdehyde in meat after slaughter of birds. Different sources and levels of zinc in the feed had no effect on the trend of changes in the response of the immune titer against gumbo and bronchitis. At high levels of zinc in the diet, lymphocyte counts decreased and heterophils increased; Also, the ratio of heterophils to lymphocytes at the level of 180 mg/kg was significantly higher than the level of 120 mg/kg (P<0.05). In addition, different sources and levels of zinc and their interactions on the overall SRBC titer were also insignificant.