In situ and mobile bag methodology to measure the degradation profile of processed feeds in different segments of the equine digestive tract

The purpose of this review paper is to outline developments in the use of the mobile bag and in situ porous bag techniques for use in nutrition studies with equines. Adaptation of these techniques, combined with mathematical modelling of feed degradation profiles and estimates of digesta passage allow the in vivo quantitative partition of feed degradation amongst the major segments of the equine digestive tract. Measurement of dry matter effective degradability values in the small intestine (pre-caecal), caecal and colonic segments of the equine digestive tract for four fibre feeds is described. Digesta passage rates pre-caecally, in the caecum and in the total tract of equines are also briefly discussed. Examples of how these methods can be used to assess the degradation of forage components in the total tract of equines and the effects of feed processing on feed degradation profiles in the small intestine of equines are also given. In order to ensure that optimum, balanced and healthy equine diets can be formulated in practice, further studies are now required to capitalise on the development of this methodology. Comprehensive experiments should now be undertaken using defined animals and dietary conditions that partition degradation of individual feed constituents in a wide range of common equine feeds across each of the major segments of the equine digestive tract. Partitioning protein digestion between different segments of the equine digestive tract would be particularly beneficial.