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

Abstract

Early rumen function was studied in 71 Jersey calves fed pelleted high roughage mixtures (2 parts hay to one part grain) from 3 days to 16 weeks of age.. The establishment of rumen-indicator microorganisms, total steam volatile fatty acids in the rumen, rumen pH, and in vitro cellulose digestion were used as measures of rumen development. The effects of rumen (cud) inoculations, chlortetracycline, and supplementing high roughage pellets with a combination of molasses, monocalcium phosphate, distillers solubles, and brewers yeast were also studied using a factorial type of experimental design. In all calves fed high roughage pellets, the development of rumen function was characterized by a rapid rise in rumen volatile fatty acids to a maximum at 6 weeks of age, relatively low rumen pH values, the absence of Hay II indicator microorganisms, and a gradual increase in the ability of rumen contents to digest cellulose with advancing age of the calf in vitro. No important differences affecting early rumen fermentation were noted from feeding chlortetracycline; a molasses, calcium monophosphate, distillers solubles, and brewers yeast supplement, or different levels and sources of protein. However, in vitro tests showed that including chlortetracycline in the basal high roughage pellet reduced propionic acid yield. Feeding either chlortetracycline or molasses-containing supplements to calves suppressed in vitro cellulose digestion slightly. This difference was more marked when supplemented pellets were digested in vitro with a standard inoculum. Rumen-inoculated calves were observed to have high average ratings for rumen protozoa, but nearly all of uninoculated calves remained free of rumen protozoa until 16 weeks of age. Inoculations also increased the average rating of Hay I indicator microorganisms and in vitro digestion of cellulose by rumen microorganisms. Inoculating resulted in higher rumen levels of butyric acid and lower propionic acid, but reduced the rumen pH during the age period of 2-5 weeks.