Effect of anti-stress feed additive on immune responses and blood parameters of three commercial broiler strains under heat stress conditions

This study was conducted to investigate the effects of anti-stress feed additive containing probiotic Protexin®, vitamin C and betaine in three commercial broiler strains on immune responses, some blood parameters and oxidative stability of breast muscle under heat stress conditions. A total of 720 one-day-old broiler chicks were used in a completely randomized design as a 2×3 factorial arrangement consisting 2 levels of additive (with and without) and three broiler strains (Arbor Acres, Ross 308 and Cobb 500) with 6 treatments, 4 replicates and 30 birds in each replicate. The birds were exposed to heat stress (37 °C) for 8 hours daily from 22 to 42 days of age. In addition of performance parameters, humoral immune response was measured by intravenous administration of 5% sheep red blood cell (SRBC) suspension and primary and secondary antibody titers were determined. At 42 day of age, blood samples were collected to measure blood serum parameters including total protein, cholesterol, triglyceride, HDL and LDL. The heterophile to lymphocyte ratio and also glutathione peroxidase and super oxide dismutase enzyme activities were evaluated at 42 day of age. Among the evaluated parameters, only LDL concentration was affected by experimental strains (p < 0.05) and the minimum serum LDL concentration was observed in Arbor Acres strain. Generally, the strain and feed additive used in this experiment had no significant effect on immune response and breast muscle oxidative stability of heat-stressed broilers.