Effect of different levels of vitamin premix during finisher period on broiler on performance and immunocompetence in battery cage and floor systems

摘要

Two trials were conducted to evaluate the withdrawal or reduction of vitamin premix from diets of finisher period (29 to 42 days of age) on broiler performance and immunocompetence. Trial 1 was conducted as a completely randomized design with 4 treatments of 6 replicates and 5 chicks in each batter}' cage system. Trial 2 was conducted with 4 treatments of 6 replicates and 18 chicks in pen floor system. The diets were formulated based on wheat and barley, and dietary treatments were: T1 = based diet without vitamin premix, T2= based diet with 33.33% vitamin premix, T3 = based diet 66.66% vitamin premix, T4 = based diet 100% vitamin premix (Control Group). On day 34, two birds from each replicate were selected and antibody responses to inoculated sheep red blood cells were determined. The cell-mediated immunity was determined via phj'tohemagglutinin (PHA) and dinitrochlorobenzene (DNCB). Results of trial 1 showed that there were no significant differences in the bird’s performance with reduction orw'ithdrawal of vitamin premix from diets in 29-35 days among the experimental groups, but in 36-42 days of age. the performance of the group of the birds fed with diet without vitamin premix (TI) was significantly lower than other groups (P < 0.05). Results of trial 2 showed that vitamin premix reduction and withdrawal from 29 d of age did not impair body weight, feed intake and feed conversion ratio during the final period of broilers (29-42d). The results of two trials demonstrated that immunocompetence response was not affected by treatments in finisher period. The results of tlie present study indicated that in the battery cage system it's possible to reduce dietary vitamin premix during finisher period but withdrawal can negatively affect performance of broilers. While in the floor system it is possible to withdraw vitamin supplements from finisher diets.