Some Effects on the Rumen Micro‐organisms of Overfeeding a High Barley Ration

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Abstract
Summary.: When the barley ration fed to a heifer was increased from a steady rate of 3 × 1·7 kg/24 h to 10 kg within 7 h, the animal became lethargic and scoured, and rumen movement ceased. These clinical symptoms were accompanied by gross changes in the bacterial flora of the rumen. Lactobacilli increased from 1·3 × 104/ml to 1·96 × 109/ml and comprised 60–65% of the total viable count, displacing the usual ‘barley type organisms’ (bacteroides and Gram negative vibrio types) as the predominant organisms. At the same time rumen lactic acid concentration rose to 912 mg/100 ml and the pH value fell from 5·7 to 4·5. After recovery of the animal and reintroduction of restricted feeding the ration was slowly increased until it reached a daily level approximating to the amount taken during the period of rapid feeding. The ration of a second animal was similarly increased. The animals showed no ill effects; lactobacilli comprised only 0·19 and 1·17%, respectively, of the total viable counts, rumen lactic acid was < 5 mg/100 ml and the rumen pH values were 5·2 and 5·5 for the 2 animals. Bacteria of the genus Bacteroides predominated in both rumina.