As feed evaluation methods for ruminants move towards a more dynamic approach of assessing nutrient supply, in order to reflect the complex nature and microbial intervention in the digestion process in ruminant animals, it is becoming increasingly important to predict the rate, extent and site of digestion. Presently the main method for measuring feed degradation is the in situ polyester bag technique. However, it is now known that this method is not appropriate for starch rich feeds due to the loss of fine particles. An alternative approach is to measure the rumen fermentation kinetics using the gas production technique as this may also give a better estimate of energy available for microbial growth. An experiment was undertaken to study the influence of feed processing on the fermentation profiles of ruminant feeds using an automated gas production system.