Determining the Optimal Pattern of Vitamin Supplementation in Diets Containing Wheat Waste by Estimating the Performance and Immune Responses of Broiler Chickens

In the past, vitamins were considered as unknown growth factors, but during the twentieth century, their structure and nature were gradually discovered. These compounds are necessary to maintain the integrity of the tissues and general health of the body. Broiler chickens are unable to synthesize vitamins (except vitamin C) or have the ability to make limited amounts of them (group B and K2). For this reason, vitamins should be added to broiler feed as a supplement. Vitamins interact with other nutrients in various ways. The main reference for vitamin requirements in broilers is the National Research Council (NRC, 1994). The recommended amounts ensure conditions where there are no severe deficiencies. Applying the NRC recommendations cannot guarantee the genetic potential of today's birds. Because these values were taken from old studies and using pure feeds in laboratory conditions. Due to the dependence of Iran's poultry industry on the import of vitamins, unfortunately, in recent years, few studies have been conducted in the country on the appropriate pattern of adding vitamins to the diet of broiler chickens. Therefore, it is necessary to examine the lower levels than the recommendation of the Ross 308 strain catalog (Aviagen, 2019) as the dominant strain of the country and to propose an optimal model for different regions that does not have a negative effect on the performance and safety traits and to reduce the need to import this strain. It will also follow the products.

The aim of this study was to determine the optimal pattern of vitamin supplementation in diets based on corn, wheat waste and soybean meal on production traits, carcass characteristics and immune responses of broilers from 1 to 42 days of age in Fars province. A total of 500 Ross 308 broilers with similar mean weight (mixed sex) were distributed in a completely randomized design with five treatments, five replications and 20 chickens per replication. Experimental treatments included five levels of vitamin supplementation: 1) control (100% of the recommended values of Ross 308, 2019 strain catalog), 2) 90% of the recommended values of Ross 308, 2019 strain catalog, 3) 80% of the recommended values of Ross 308, 2019 strain catalog, 4) 70% of the recommended values of Ross 308, 2019 strain catalog and 5) 60% of the recommended values of Ross 308, 2019 strain catalog. At the end of each period, the feed consumption and body weight of the birds were recorded with a digital scale with an accuracy of ±0.01. At the age of 39 days, blood was drawn from the vein under the wing of two birds from each experimental unit, with a syringe containing EDTA anticoagulant, and the blood sample was quickly transferred to the laboratory in a flask containing ice for differential counting of white blood cells. At the end of the 42nd day of rearing, two birds from each experimental unit were slaughtered to measure the relative weight percentage of carcass components. To measure the humoral immune response, the injection of 0.5 ml sheep antigen (SRBC) at the age of 21 days was used. CBH skin hypersensitivity test was also used to measure cellular immune response.

The highest and lowest mean body weight gain and feed intake belonged to the vitamin pattern of 100 and 60% of the recommendation of Ross 308 strain, respectively (P<0.01). The best feed conversion ratio and production index belonged to the vitamin pattern up to 90% of the Ross strain recommendation (P<0.01). The highest and lowest percentages of pectoralis muscle (22.2% and 19.2%) were related to the pattern of 100 and 60% of vitamin supplementation recommended by the Ross strain (P<0.01). The effect of reducing vitamin supplementation on cutaneous basophil hypersensitivity (CBH), serum antibody level against SRBC and percentage of heterophils, lymphocytes and heterophil to lymphocyte ratio was not significant.

There was no significant difference between the functional indices and most importantly the production index of treatment 1 (100% vitamin pattern) and treatment 2 (90% vitamin pattern). Carcass traits and indicators related to humoral and cellular immune systems did not show significant differences too. As a result, a 10% reduction in the level of vitamin supplementation compared to the recommended level of the Ross 308 catalog is possible and suggested for raising broiler chickens. The final result is that in the breeding conditions of Fars province poultry farms, it is possible to reduce the level of vitamin supplements in diets containing wheat waste up to 90% of the recommendation of Ross 308 strain compared to the control diet.