Volatile fatty acids, proxies for methane production in ruminant animals

Abstract

Determining enteric methane, produced by grazing extensively managed cattle is practically impossible. The objective of this study was to determine enteric methane yield from beef cows using VFAs as proxies. A total of 24 cows were randomly selected for the study. The animals were grouped and identified according to their parity: P1-P4. Rumen liquor samples were collected every fortnight for 12 months through a stomach tube, and VFA analysis was done using gas chromatography. The effect of parity and season (wet, dry and cold) on the mean concentrations of the VFAs and methane was analysed. Parity and season were considered as fixed factors while each individual cow was regarded as a random variable. The result indicates that parity and season influenced (P < 0.05) the acetate, isobutyric and isovaleric acid concentrations. A Parity x season interaction significantly influenced the propionate, butyric and valeric acid production (P < 0.05). There was an interaction (P < 0.05) between parity and season on methane production, animals in P3 had the highest methane values compared to other parities during the wet and cold seasons. It can be concluded that parity and season influence VFA and methane production, and VFAs can be used to predict enteric methane production for grazing animals.