Dietary Influences on Eructation and Related Ruminal Phenomena in Cattle

Abstract

On a diet of alfalfa tops, eructation rate and volume, as determined by the tracheal transection technique, were so depressed in 3 steers and 2 cows that a positive intrarumen pressure was maintained for 130 minutes after feeding. Only a slight increase in pressure, which lasted for 70 minutes, was measured when oat hay was fed the night preceding alfalfa tops ingestion. A subatmospheric intrarumen pressure was found during the oat hay trials. An eructation occurred on almost every secondary rumen contraction during the oat hay trials. The frequency of the secondary contractions, as well as the total number of rumen contractions, was significantly (1% level) higher during the tops trials than when oat hay was fed. There was no increase in eructation frequency coinciding with the increase in the number of secondary rumen contractions during the alfalfa tops trials. An excellent correlation (r = 0.96) was found between the ratio of secondary to primary rumen contractions and intrarumen pressure. On essentially equivalent TDN intakes, the total gas eructated was greater on the tops than on the oat hay diet. Frothy rumen ingesta were noted after the completion of the alfalfa tops trials. Acute legume bloat probably results from a rapid rate of gas formation, accompanied by a frothing of the ingesta which physically prevents eructation.