Antibiotics in Dairy Cattle Nutrition. III. Effects of Different Levels of Aureomycin Intake upon the Growth and Well-Being of Dairy Calves, and the Association of Differences with Changes in Environment

Abstract

Summary Thirty Holstein and Jersey calves 4 days old were divided randomly by breed and sex into three groups. Calves in one group (control) received a basal ration only; calves in the second group received, in addition, Lederle's Aurofac in amounts, calculated to supply 15 mg. of aureomycin daily per 100 lb. weight; calves in the third group received 45 mg. of aureomycin per 100 lb. weight. The experiment was conducted in a barn that had not housed calves previously, and the results were compared with those of an experiment in which the calves were fed a 15 mg. level of aureomycin and raised in an old barn that had proved unfavorable for calf raising. In the new quarters, in which sickness was not as great a problem, both levels of aureomyein feeding reduced the incidence of infection. Calves fed no aureomycin in the new quarters grew as rapidly as calves fed aureomycin in the old quarters. However, aureomycin-fed calves in the new quarters grew at a significantly faster rate than the control animals. It was found that the 45-mg. level of aureomycin was more effective than the 15-mg. level in controlling the types of infections encountered. During the period of 1 to 25 weeks of age, average growth rate of both breeds considered together was increased significantly by the 15-mg. level of aureomycin feeding. Another statistically significant increase resulted when the level of aureomycin was increased to 45 mg., but the growth rate was not in proportion to the increased aureomycin. In the Jersey breed the 45-mg. level of feeding was more effective than the 15-mg. level, but in the Holsteins 15 mg. was the more effective. Holstein calves receiving 45 mg. failed to show any growth advantage over the control calves. For the period of 1 to 16 weeks, calves receiving 15 mg. of aureomycin consumed 19% more hay, and those receiving 45 mg. consumed 38% more, than the controls. These differences were not statistically significant. The differences in grain intake followed the same trend but were not as great and also were not significantly different. The calves receiving 45 and 15 mg. of aureomycin used less total digestible nutrients and less digestible protein per pound of gain than the control calves. These differences were not statistically significant.