Research On Animal Production

  This experiment was conducted to evaluate the effects of different levels of zinc on performance, egg quality traits and some blood parameters under normal rearing condition. Ninety six 70-weeks-old laying hens were used in a completely randomized design with 4 treatments, 4 replicates and 6 hens in each replicate in 10 week period. Treatments were 4 different levels of zinc (40, 70, 100, 130 mg zinc/kg diet) that was supplied in the form of zinc sulfate. Blood samples were collected through brachial vein at the end of experiments. Results of the experiment indicated that birds were fed on diets containing 130 mg zinc/kg diet and diets containing 40 mg zinc/kg diet showed the highest and the lowest hen-day egg production (P<0/05). Average egg weight was highest in 130 mg zinc/kg diet during the experiment (P<0/05). Increasing the level of zinc, reduced feed intake and improved feed conversion ratio (P<0/05). The treatment containing 100 mg zinc/kg diet showed the best Performance. Increase haugh unit, in hens fed 130 mg zinc/kg diet, was higher than the others treatments (P<0/05). Eggshell quality was significantly affected by treatments (P<0/05). The levels of glucose, cholesterol and LDL were significantly decreased in hens fed on diets containing 130 mg zinc/kg diet (P<0/05). Also with the increase of zinc, serum triglycerides decreased, so that treatment with 100 mg zinc/kg diet showed the lowest triglycerides concentration (P<0/05). The results of this experiment showed that increasing the level of zinc can improve performance and egg quality of layers.