Investigating the Effects of Reducing the Level of Vitamin Supplements in the Diet of Ross 308 Broilers

 Optimal nutrition occurs only when poultry efficiently use the nutrients in the feed for growth, health, reproduction and survival. Vitamins should be present in sufficient amounts in the diet due to their vital functions in the animal's metabolism and the optimal utilization of other nutrients.

Five hundred one-day-old 308 Ross strain chicks (male and female) were distributed in a completely randomized design with 5 treatments, 5 replications and 20 chicks per replication. Dietary treatmets are included five levels of vitamin supplementation: 1) control (100% recommended values of strain Ross 308 catalog), 2 to 5) 90%, 80%, 70% and 60% recommended values. During the 42 days of the experimental period, performance was recorded at the end of each period (ages 10, 24 and 42 days). Evaluation of humoral immune response was performed using SRBC injection at 35 days of age. Cellular immune response was assessed at 37 days of age by hypersensitivity test. At 42 days of age, ten birds per treatment were bled to count white blood cells and then the birds were slaughtered, and the relative weights of different parts of the carcass were measured.

The suggested level of 80% vitamin supplement had no significant effect on performance including feed intake, FCR, survival percentage and production index (p<0.05). By reducing the level of vitamin supplement, the length of jejunum and the percentage of wings and spleen decreased in the experimental treatments (p<0.05), but the percentage of carcass and other components were not affected (p>0.05). Antibody titer in response to SRBC injection, cellular immune response and the number of white blood cells were not affected in level of 80% vitamin supplement, although the level of 80% vitamin supplement significantly reduced IgG titer and heterophil percentage (p<0.05).

In general, the results showed that it is possible to reduce the level of vitamins in the diet of broiler chickens by 20% without negatively affecting the performance and responses of cellular and humoral immunity.