Tylosin and Chlortetracycline for the Prevention of Liver Abscesses, Improved Weight Gains and Feed Efficiency in Feedlot Cattle

Four feedlot experiments with 1829 cattle were completed in 1973 evaluating 75 mg tylosin and 70 mg chlortetracycline (CTC) per head per day in medium to high concentrate rations. Continuous administration of these antibiotics reduced the incidence of liver abscesses and improved average daily gain and feed conversion. Liver condemnation for control cattle was 56.2%; chlortetracycline, 44.2%; and tylosin, 18.6%. Average daily gain for control cattle was 2.43 lb (1.10 kg); chlortetracycline, 2.51 lb (1.14 kg); and tylosin, 2.57 lb (1.17 kg). Feed conversion ratio for control cattle was 8.21; chlortetracycline, 8.14; and tylosin, 7.87. Analysis of incidence of liver abscesses indicated that tylosin controlled liver abscesses more effectively than chlortetracycline (P <.001). Both antibiotics reduced the incidence of liver abscesses (P < .001) when compared to cattle receiving no antibiotics. An analysis of the effect of severity of liver abscesses on total average weight gain performance of control cattle demonstrated that total weight gains of cattle with slight or moderate liver abscesses were not affected.