RESUMO
The use of protective, probiotic cultures in poultry farming may serve as a useful strategy to improve food product safety from the beginning of the food chain and thus to protect consumer health. The objective of this study was to investigate the effect of the probiotic strain Bifidobacterium longum PCB133 on innate and adaptive immune responses in turkeys beginning at 2 wk of age, under farming conditions. The vaccination efficiency against Newcastle disease virus served as the primary endpoint. At 2 wk of age, male turkeys (British United Turkey Big 6 strain) were randomly assigned to the control (n = 25) or probiotic group (n = 25). Turkeys in the probiotic group received the probiotic B. longum PCB133 (at least 3 × 10(7) cfu/d) incorporated into the daily feed ration for 5 wk, until slaughter at 7 wk of age. At the beginning of the probiotic intervention, birds in both groups were vaccinated against Newcastle disease. Birds were weighed weekly throughout the intervention period, and finally blood sera and heparinized blood were collected for immune function tests (lymphocyte proliferation, phagocytosis, respiratory burst), and for the determination of Newcastle disease virus antibody titers. No effects on BW gain and on the proliferation of blood lymphocytes were elicited by the 5-wk intervention with the probiotic. Concerning the primary endpoint of the study (i.e., specific antibody production as a response to vaccination against Newcastle disease), no adjuvant effect of the probiotic could be determined. In addition, innate immune functions tested were not significantly affected. In conclusion, first scientific evidence on the application of the probiotic strain B. longum PCB133 in turkeys beginning at 2 wk of age does not support an improvement in live performance, humoral immunity, or innate immunity.