We tested new types of probiotics for chickens in 14 independent experiments. Using hundreds of chickens, efficacy of 22 different mixtures was tested and compared. Unifying feature of the tested mixtures was that all contained different representatives of genus Bacteroides and family Veillonellaceae. Although initial aim of this study was to identify a mixture of the most effective composition, finally we ended up with a conclusiom that if the mixtures contain representatives of genus Bacteroides and family Veillonellaceae, species and strain composition is not that important. The tested mixtures increased chicken resistance to infection with Salmonella approx. 50 times. The more interesting was the effect against spread of Salmonella among chickens by a mere contact. In such experiments, the tested probiotic mixtures decreased spread of infection more than 1000 times. The tested mixtures increased also chicken resistance to Campylobacter jejuni thought the protective effect was not as high as against Salmonella. The paper can be read in full here.