Origin of Abomasum Gas in the Cows with Displaced Abomasum

Abstract

The gas composition of the rumen and the abomasum were investigated in 71 cows including 25 cows with displaced abomasum. The ratio of methane (CH₄) to CO₂ in the abomasum gas was higher than that in the rumen. In the incubated mixtures of fresh rumen fluid, CH₄ was detected at a high concentration, while a small amount of CO₂ and CH₄ was found in incubated mixtures of fresh abomasum fluids. Hence, it was suggested that the gas in the abomasum originated not from the abomasum itself but from the rumen. In cows fed with mixed roughages and concentrates, the rumen CO₂:CH₄ ratio was higher compared with cows fed with roughages alone. Marked changes in rumen gas composition were presumed to be associated with changes in abomasum gas composition. Consequently, it is possible that feeding a large quantity of concentrates may increase the flow rate of the ingesta through the forestomach, so that the return rate of gas separated from the ingesta in the abomasum to the forestomach may also increase. Therefore, the frequent accumulation of a large amount of gas with concomitant changes in the total volatile fatty acid (VFA) concentration in the abomasum caused abomasal atony and subsequently displaced abomasum.