Enterococcus faecium EM41 is an isolate from ostrich faeces. It produces a thermo-stable proteinaceous substance, bacteriocin (enterocin) EM41 with the highest inhibition activity in late logarithmic phase of growth (25 600 AU/ml). This strain and its enterocin have not been previously tested in animals. Lohmann Brown laying hens (aged 45 weeks) were involved in this model/pilot experiment, divided into 3 groups 6 birds in each. E. faecium EM41 applied was a variant treated with rifampicin (109 cfu/ml, dose 400 μl/animal/day) to differentiate it from the other enterococci. Partially-purified enterocin EM41 (Ent EM41, dose 40 μl/animal/day) and its producer were applied to water for 21 days. The experiment lasted 35 days. Sampling was performed at days 0-1, 21 (3 weeks of additive application), 35 (2 weeks after cessation of additive application) from every bird. E. faecium EM41 sufficiently colonized the intestinal tract of laying hens from the initial concentration 109 cfu/g, its count reached 4.30 log cfu/g at day 21. PCR genotypization confirmed the identity of the EM41 strain with the species Enterococcus faecium. E. faecium EM41 and its enterocin EM41 showed antimicrobial effects demonstrated by reduction of coagulase-positive and coagulase-negative staphylococci, coliforms, Pseudomonas spp., Aeromonas spp. and Campylobacter spp. The hens were Salmonella spp. free. After administration of both additives, phagocytic activity was stimulated with a significant increase. The additives did not negatively influence biochemical and haematological parameters or weight gains.
