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Seventy two rabbits (Hycole, (♂+♀) 5 weeks old) were divided into 2 experimental (EG) and one control (CG) group. The feed mixture A in control (CG) did not contain any coccidiostat. In the first experimental group (EG1) was tested a complete granulated mixture B enriched with 30 g dry extract Eleutherococcus senticosus per 100 kg mixture. The animals were fed mixture B in combination with probiotic strain Enterococcus faecium EF AL 41 applied orally at a dose (10 9 CFU. ml-1) 500 μl per animal in drinking water during 21 days. In the second group (EG2) was tested complete granulated mixture B. The experiment lasted 42 days. Body weight and feed consumption were registered weekly. Samples of faeces were taken at days 1, 21 and 42 to monitor the counts and effect of natural substances. Blood samples were also taken to check biochemical parameters using commercial kits. The samples for microbiological analyses were treated by the standard microbiological method according to ISO with appropriate media. Results presented in this study introduce different mechanisms of action for different classes of feed additives and how these may influence the observed live performance benefits. Application of Eleutherococcus extract in combination with EF AL 41 strain in rabbits was beneficial for performance. Additives reduced counts of S. aureus and Clostridium-like sp in faeces. Bioactive substances can be beneficial for animal health as was repeatedly confirmed by our results (mortality in EG1- 12%, EG2 - 8% compared to CG- 17%).

Enterococcus faecalis isolates from chourico (traditional Portugal fermented sausage) were studied here with the main impact on bacteriocin production. In bacteriocin-producing strains phenotypic antibiotic profile was tested to check if they are sensitive or resistant. Lactic acid production ranged from 0.581 mmol/L up to 0.783 mmo/L. Enterococci grew sufficiently in the medium with 1% concentration of oxgall/bile. From 14 E. faecalis, bacteriocin substances (Bs) by 8 strains were found to inhibit the growth at least 1 indicator of 27 (inhibitory zones-10 to 18 mm) by the qualitative method. The effect of Bs of 8 active E. faecalis strains was tested also by the quantitative method; Bs of 6 E. faecalis inhibited the growth at least of 1 indicator; E. faecalis P06/7, P06/13, P06/16 inhibited the growth of Enterococcus avium EA5, Listeria innocua LMG13568, Staphylococcus aureus SA5 (activity: 100 to 1600 AU/ml). The highest activity (1600 AU/ml) showed Bs produced by P06/16 against LMG13568. Taking into account the antibiotic sensitivity and activity in the strain itself, the most promising strains for detailed bacteriocin studies are E. faecalis P06/16, P06/7, P06/13 which are mostly antibiotic sensitive and bacteriocin active.