Aureomycin as a Protein-Sparing Agent and its Influence on Minimum Starter Protein Level Satisfactory for Normal Growth of Dairy Calves

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Abstract
SUMMARY Sixty two-day-old Holstein and Jersey calves were raised to 86 days of age on a limited milk-hay-starter system to determine (a) whether aureomycin spared dietary- protein, and (b) the mininmm starter protein level satisfactory for normal growth Of aureomycin-fed calves reared on a limited milk-hay-starter system. Five starters ranging from 6.3 to 14.2% protein were fed with and without aureomycin. The antibiotic did not spare dietary protein in this experiment, but did F, ive satisfactory gains on a starter containing at least 2% less protein than the starter required to give similar gains with- out aureomycin. Normal weight gains were made by calves on the 12.2 and 14.2% pro- tein starters when aureomycin was fed. Significant increases in average daily gain, height at withers, heart girth, and starter consumption were obtained when aureomycin was fed. The antibiotic had no significant effect on apparent digestibility of any of the nutrients in the ration, nitrogen retention, blood levels of plasma protein, urea nitrogen or nonprotein nitrogen; however, aureomycin tended to lower slightly the blood levels of urea and nonprotein nitrogen. Aureomycin gave a slight but nonsignificant depres- sion in rectal temperature. Calves on the'12.2 and 14.2c~ protein starters had signifi- cantly higher coefficients of apparent digestibility of crude protein, and the 14.2% protein groups had significantly greater nitrogen retention than did calves on the 6.3% protein starters.