Further Observations on the Effect of Protein upon Roughage Digestion in Cattle

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Abstract
Five series of digestion trials were conducted to study the influence of protein upon roughage digestion in cattle. Protein levels were varied by substituting dried skimmilk for mineralized starch in three series. In two of the three series corncobs were fed as the sole roughage and in the third series clover hay was fed. In the fourth and fifth series, ration protein was varied by adding skimmilk powder directly to corncobs in one instance, and to a constant mixture of corncobs and starch in the other. Improvement in roughage digestion occurred in every series with dried skimmilk additions where starch formed a part of the ration. Little or no improvement in corncob digestion was noted with dried skimmilk additions when no starch was fed. The conclusion seems apparent that the protein requirement for efficient roughage digestion in cattle is extremely low when roughages are fed in the absence of starch or starchy grains. When starch forms a part of the ration the need for protein supplement, dried skimmilk, is increased in maintaining roughage digestion. Further study is needed as to the exact method by which starch increases the protein supplement needs for efficient roughage digestion in ruminants.