A High Roughage System for Raising Dairy Calves Based on the Early Development of Rumen Function. III. Effect of Rumen Inoculations and the Ratio of Hay to Grain on Digestion and Nitrogen Retention

Abstract

The digestibility of protein, dry matter, and cellulose and N retention were studied in rumen inoculated and uninoculated calves and in calves fed various types of hay and grain in the ratios of 4:1, 3:2, and 2:3. Cud inoculations increased the apparent digestibility of protein in a calf when a low protein, poor-quality hay ration was fed or when the chief source of protein was alfalfa hay. Increased protein through heavier grain feeding did not result in a difference in protein digestibility between cud inoculated and uninoculated calves. N retention was not significantly affected by rumen inoculations. Alfalfa and mixed clover-timothy hay fed in combination with a mixture of corn and soybean oil meal in the ratio of 4 parts hay to 1 part grain resulted in the low N retention of 7.45 g./day/100 lb. of body wt. When hay-grain ratios of 3:2 and 2:3 were fed, the avg. retention was 11.87 and 12.87 g. of N/100 lb. of body wt./day, respectively. The avg. daily N retention for the 2 types of hay was approx. the same even though the apparent digestibility of alfalfa hay was markedly higher than that of the mixed clover-timothy. The digestibility of cellulose was less when the 2:3 ratio of hay to grain was fed than when either 4:1 and 3:2 ratios were fed, regardless of the type of hay used. Calves changed abruptly from 2:3 to a 4:1 ratio digested cellulose equally as well as as control calves fed continuously on a 4:1 ratio. The implications of these results are discussed in relation to rumen physiology and their appln. to the high roughage system of calf feeding.