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Summary The growth-promoting effect of aureomycin added to a calf ration which provided 15 to 20% of body weight daily of milk and a milk replacement mixture for the first 30 days was determined with 28 Jersey and 35 Holstein calves. The average gains of the aureomycin-fed calves exceeded those of the control calves during the milk feeding period as well as after weaning, but the differences were not statistically significant because of the wide variations in gains within each group. These results indicate that on a liberal milk feeding regime for calves growth stimulation due to aureomycin will not be attained consistently.

Summary Sixty-two pairs (33 Jersey and 29 Holstein pairs) of milking cows were used to compare aureomycin supplementation with a control ration for a 12-wk. period. Treated cows were fed at the rate of 10mg. per 100lb. body weight. Seventeen pairs were continued on the experiment for 17 wk. and another eight pairs for 6 mo. The differences between the two groups of cows in milk production and body weight changes were not significant at the 5% level. The cows receiving aureomycin showed no obvious advantage in resistance to mastitis, foot rot, or other bacterial disturbances throughout the study.