Effect of Chlortetracycline on Nutrient Utilization by Dairy Calves

Summary Sixteen male dairy calves were used to study the effect of chlortetracycline, fed at a level of 80mg. per calf daily, on growth and nutrient utilization. The average weight gain during the 16-wk. experiment was 164lb. for the antibiotic-fed calves and 145lb. for the controls. Conventional digestion trials conducted during the fifth, eighth, and 11th weeks of the experiment gave little evidence that chlortetracycline has any effect on ash or nitrogen retention or upon the apparent digestibility of cellulose, protein, or dry matter. Neither observations on the disposition of orally administered Ca 45 nor data from a concurrent total calcium balance study conducted during the 12th wk. gave any substantial evidence that chlortetracycline has any effect on calcium utilization. Measurement of bone growth, by use of radioautographs, from the time of Ca 45 administration to sacrifice of the animals demonstrated that the greater weight gains of the antibiotic-fed calves were paralleled by greater skeletal development. The increased growth of the calves receiving the antibiotic was associated with increased feed consumption.