Tylosin is a macrolide antibiotic with a bacteriostatic effect (inhibiting the synthesis of the bacterial proteins) against Gram-positive and some Gram-negative microorganisms Streptococcus spp., Staphylococcus spp., Erysipelothrix spp., Corynebacterium spp., Brachyspira, Serpulina (Treponema) hyodysenterae, Borrelia, Spirochaeta spp., Campylobacter (Vibrio) coli, Pasteurella spp., Brucella spp., Ricketsia spp., Mycoplasma spp., some large viruses, including also some anaerobic microorganisms (Fusobacterium spp., Bacteroides spp.), etc. It is active against Chlamidia spp. as well. Tylosin does not act antimicrobially directly on the bacteria of the family Enterobacteriaceae E. coli, Salmonella spp., but reveals an antiadhesive activity (hindering their adhesion on the intestinal vili, their penetration through the intestinal mucous membrane and impeding their colonization's phase as well). Tylosin proves also an anticoccidial activity mostly against Eimeria tenella. It also improves weight gain and feed conversion efficiency. Applied orally, the antibiotic is absorbed by the gastrointestinal tract not so intensively in comparison with the tartrate, but it penetrates in the target organs and tissues. Excretion is mainly through urine and bile, milk (in lactating animals) and eggs (in egg-producing poultry). It is compatible with tetracycline, sulphonamides, spectinomycin and the common dietary components of the feeds. Prevention of vertical transmission of mycoplasma Superior egg quality Increases egg production Superior chicken quality Increases hatchability Superior feed efficiency