Diurnal changes in the methane concentration in the rumen headspace of cannulated cattle

Abstract

The study investigated the diurnal chance in the methane gas percentage in the headspace of the rumens of four beef cattle (average body weight, 556 kg) with rumen cannulas. The cattle were housed individually in metabolic stalls and fed a basal diet twice daily in equal amounts at 0900 and 2100 h. At baseline, rumen gas samples were collected every hour from the morning until the evening feeding on seven different days over a 10-day period. At each sampling, three syringe needles were passed through the ruminal cannula stopper to collect the gas samples. After the baseline sampling period, three 2-mm nylon mesh bags, containing 9 or 10 pieces (20 g, atypical round shape, 3~5mm thick) of sliced rhubarb root, were placed at three different depths in the rumen of each animal for 20 days (after treatment), and gas samples were collected on nine different days. The nylon bags were removed from the rumen immediately after the last sampling. Gas in the recovery phase was collected on four different days over a 21-day period. There was considerable variation in the methane gas concentration in the rumen headspace in individual animals, on different sampling days, at each baseline sampling time. Nevertheless, diurnally, the methane concentration at each baseline was high for 6 h after the morning feeding and low for the next 6 h before the evening feeding. Compared with the mean methane concentration at baseline, the concentrations were significantly lower (p < 0.01) after treatment and in the recovery phase; also the rate of methane recovery differed among animals. This experiment provides evidence that the methane gas percentage in the headspace of the rumens of cannulated animals is a useful tool for in sacco screening of anti-methanogenic feed additives or plant material.