Effects of dietary inclusion level of a mixture of probiotic cultures and enzymes on broiler chickens immunity response.

The current study was conducted to analyse the effect of a mixture of probiotic cultures and enzymes (Probio Enzyme, XVET GmbH, Germany) on the immune response and weight of central lymphoid organs and liver in broilers. A total of 270 male chickens were randomly divided into nine groups, with three replicates of 10 birds each. Treatment groups were fed for either 22 or 42 days with different levels of Probio Enzyme 250, 500, 750 and 1000 g/ton, whereas the control group fed a basal diet without Probio Enzyme. To analyse the effects of dietary supplementation on broilers humoral immune response, the antibodies titres for avian influenza (AI) and Newcastle disease virus (NDV) and to the sheep red blood cells (SRBC) challenge were assayed in birds from each experimental unit, along with the assessment of the weight of the main lymphoid organs and liver. The addition of the Probio Enzyme mixture did not significantly affect the titres of the antibodies against AI and NDV at day 42, despite the wide individual variation observed specially on the antibody titres at day 33. Treatments affected the production of IgG after the second challenge with SRBC (P = 0.003), which was transposed to the correspondent total Ig titres (P = 0.044). Conversely, a lower birds' body weight (BW) was found in the majority of treated groups compared to control (P = 0.031). The spleen was the only lymphoid organ showing differences in the absolute and relative weight (P = 0.003 and P = 0.001, respectively). No differences were found in thymus and Bursa of Fabricius weights. In conclusion, broilers treated with Probio Enzyme showed a satisfactory immune response compared with control, despite the wide variation found after the first vaccine challenge against AI. Moreover, the probiotic mixture dose and duration modulated differently the immune response and the spleen weight, unaffecting the central lymphoid organs weight.