Effect of Type of Protein on the Response of Young Dairy Calves to Aureomycin with Data on the Intestinal Microflora

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Abstract
A study was made of aureomycin supplementation to calves receiving a 27-37% level of soybean meal, cottonseed meal or degossypolized cottonseed meal in the calf starter. 36 purebred male calves (18 Holsteins and 18 Jerseys) were divided into 3 groups. One-half of each received the antibiotic starting at 4 days of age. 50 mg. of crystalline aureomycin HC1 were added daily in the milk for 27 days; the calf starters which contained a 1% level of an aureomycin supplement were fed at 8 days of age. The remaining animals in each group served as controls. All calves were weaned from milk at 30 days of age. At 16 weeks of age the calves on the soybean oil meal starter plus aureomycin showed the best gains. An increased feed efficiency was also obtained on this ration. Fecal samples were obtained biweekly from representative calves on all rations until they were 9 weeks of age. The'' following bacterial counts were made: Aerobic, anaerobic, carrot-liver shake tubes (lactics?), coliforms, enterococci, and H2S-producing anaerobes. All counts were considerably higher while the calves were receiving milk than after weaning. The bacteria in the carrot-liver medium were not typical lactics after the calves were weaned. There were wide variations between samples from different calves on the same ration. No correlation between the numbers of any group of bacteria and the presence of aureomycin in the diet was found.