Development of Rumen Function in the Dairy Calf. II. Effect of Diet upon Characteristics of the Rumen Flora and Fauna of Young Calves

Abstract

Twenty-four male calves were placed, at an average age of 3.5 days, on diets representing liberal and limited milk-feeding programs. The calves on limited milk were further divided into those receiving aureomycin in the concentrate mix and those not receiving it. In addition, a group of calves received only milk for 8 of the 12 wk. of the experiment. Rumen samples were taken weekly and analyzed for color, odor, consistency, total bacteria, aerobic bacteria, morphologically characteristic organisms, protozoa, the levels of niacin, biotin, and riboflavin, cellulose digestion, and the amounts of the lower fatty acids (C.~-C~). For calves fed solid feeds, the general pattern of rumen function development seemed to be a sharp fall in the aerobic bacteria within the first 3 wk., an increase in the total numbers of bacteria, and the establishment of protozoa. The rumen acids were at adult levels by 6 wk. of age; whereas, the protozoal and bacterial numbers approached this point a little later. The establishment of adult-type organisms and cellulose digestion were slowest to develop and were hindered by aureomycin and liberal milk feeding. Biotin, niacin, and riboflavin levels increased up to 7 wk. of age, with an indication of synthesis early in life.