High Roughage System for Raising Calves Based on the Early Development of Rumen Function. VIII. Effect of Rumen Inoculations and Chlortetracycline on Performance of Calves Fed High Roughage Pellets

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Abstract
In 3 experiments, 86 Jerseys and 17 Holsteins were used to study effects of rumen inoculations, chlortetracycline and other feed supplements, on growth and digestion of calves fed high roughage pellets. The effect of feeding high roughage pellets of different composition, and of rumen inoculations, on the establishment of rumen microorganisms, rumen volatile fatty acids, artificial rumen digestion, and rumen pH are presented in a companion paper. Feeding high roughage pellets (basically, 2 parts one-half inch ground alfalfa hay and one part a simple grain mixture made into pellets one-fourth inches in diameter) resulted in earlier dry feed intake, earlier rumen function, and more rapid growth than was observed in previous experiments, in which loose hay and grain were fed separately in a 2:1 ratio. Growth and feed intake were enhanced when chlortetracycline was included in the pellets. Little effect was observed when chlortetracycline was fed in the milk to 7 weeks, then administered by mixing in 1 lb. of warm water from 7 to 16 weeks. No benefit was observed from the combined effects of adding molasses, distillers solubles, calcium phosphate, and brewers yeast to the basal high roughage pellets in 2 experiments. Reducing the total protein of the basal high roughage pellets from 14.3 to 12.3% by replacing all of the soybean meal with corn resulted in retarded growth and lower feed intake in both Jerseys and Holsteins. Replacing approximately one-half the alfalfa hay with good timothy hay in the basal pellets had no appreciable effect on growth or feed consumption, despite somewhat lower digestibility of dry matter and cellulose in the pellets that contained timothy hay. No significant differences in performance of rumen-inoculated calves compared to uninoculated calves were measured. There was a tendency, though the differences were not statistically significant, for uninoculated calves to perform better than those that were inoculated. Rumen (cud) inoculation in relation to high roughage system for raising calves is discussed.

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