Effect of Probiotic and Formic Acid on Immune System of Broilers

The effects of probiotic (Protexin) and formic acid were studied on humoral and cellular immunity in 200 Cobb broiler chicks in a completely randomized design of with 4 treatments and 5 replications (10 observations per replicate). Control group (C) did not receive any other than the base treatment. The chicks in the second (P), third (F) and forth (P+F) groups were fed with feed, which contained 0.1 g/kg Protexin, 0.8% formic acid vs. 0.1 g/kg Protexin + 0.8% formic acid in their diets, respectively. Daily feed intake weight gain. and feed conversion rates were recorded. The birds were immunized with Sheep Red Blood Cells (SRBC) on days 8 and 22 of age while serum antibody levels (produced in response to SRBC) being assessed through Hemagglutination Assay Technique on days 21, 28, 35, and 42. Skin response to Phytohemagglutinin-P (PHA-P) injected intradermally on day 16 was recorded 24 and 48 h following after injection. The weights of thymus and bursa of fabricius were also recorded following slaughter. The results indicated that daily feed intake and feed conversion rates decreased in the treatment groups (P<0.05). Groups P and P+F increased in mean of total anti-SRBC titer (P<0.05). IgG and IgM titers were not affected by experimental groups. Protexin and formic acid increased cellular immunity upon PHA-P injection after 24 and 48 h (P<0.05). Thymus and bursa of Fabricius weights increased in treatment groups (P<0.05). It is concluded that protexin improved cellular and humoral immunity; formic acid improved cellular immunity but not the humoral immunity. Synergism effect of protexin and formic acid was not observed.