The Effect of Rumen Inoculations on the Digestibility of Roughages in Young Dairy Calves

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Abstract
A series of balance trials were conducted to determine if calves inoculated with cud material from older cattle and fed rations high in roughage would be able to digest dry matter, cellulose and protein more efficiently than would calves similarly fed but uninoculated. Five inoculated and five uninoculated Jersey calves first were fed for 14 days on a ration of limited whole milk and alfalfa hay ad libitum. During this period, the calves which were inoculated digested a statistically significant higher percentage of the cellulose and dry matter ingested than the calves which were uninoculated. However, this appreciable difference in digestibility between inoculated and uninoculated calves disappeared when some of these calves were later placed on rations of either alfalfa hay or grass clippings only. No statistically significant differences were noted in the apparent digestibility of protein between inoculated and uninoculated calves on any of the rations used. The small, though consistent, difference in protein digestibility of approx. 2% in favor of the inoculated group in each series of trials may be attributed to the digestion of protozoa protoplasm. A calf freed of all or almost all of the characteristic indicator rumen micro-organisms by heavy grain feeding, when placed on a ration of alfalfa hay, showed a marked decrease in digestibility of cellulose in comparison with a similarly treated calf in which the characteristic rumen micro-organisms reappeared, possibly due to natural re-inoculation. These results are interpreted to mean that when roughage constitutes the entire dry feed, cud inoculations aided in providing micro-organisms which digested cellulose somewhat more efficiently than did micro-organisms which became established in the uninoculated calves. The inoculations were observed to stimulate hay consumption at an earlier age than when no inoculations were given.