When applied to male Trakiiska tunkorounna lambs of initial weight 18.6 kg in the course of 90 days at concentrations of 6 g, 12 g, and 24 g per ton of forage slinomycin brought about a rise of liveweight and average weight gain in the treated animals (for the weight gain 12.2, 16.7, and 19.4 per cent, respectively, as against the controls). The conversion rate (intake per kilogram of weight gain) was by 9.7, 16.6, and 22.2 per cent, respectively, higher. The intake of forage progressively dropped when offering higher concentration of the antibiotic, particularly during the second half of the experimental period. Highest was the effect of adding 24 g salinomycin to a ton of forage. Salinomycin induced no essential changes in the slaughter indices and in the content of cyanocobalamin in the meat. However, cyancobalamin was found to be at a higher level in the liver.