Effects of different levels of vitamin premix in finisher diets on performance, immuno-competence and meat lipid oxidation of chickens fed on corn-soybean meal

; *; ; ; The present study was carried out to examine the effects of a vitamin premix (VP) reduction or withdrawal from finisher diet (29-43 days) on performance, immuno-competence, and characteristics of leg bones and meat lipid oxidation of chickens fed on corn-soybean meal based diet. A total of 900 male broiler chickens (Ross 308) were allocated to five treatment groups (0, 33%, 66%, 100% and 133% VP), with nine replicates per treatment group. At 29 and 36 days of ages, four birds from each replicate were injected with sheep red blood cells (SRBC). The cell-mediated immunity was determined via phytohemagglutinin (PHA) and 1-chloro 2-4-dinitrobenzen (DNCB) at 34 and 42 days of ages. At 33, 38 and 43 days of age, 42 days of ages, and two birds of each replicate were slaughtered and bone parameters measured. The oxidative stability was evaluated by thiobarbituric acid reactive substances (TBARS) on the thigh samples that were stored for 90 day at -80 ?C. The results showed that reduction or withdrawal of VP from diets at different time points of the finisher period did not affect performance, immunocompetence and characteristics of leg bones. Results of TBARS showed that lipid peroxidation of the treatment without VP was significantly higher than of the other treatments when slaughtered at 43 days of age. Finally, the results of this study demonstrated that it is not possible to reduce the VP in finisher broilers’ diets without negative effects on meat quality during the time of freezing.