Problems with current ruminal starch degradation estimates (e.g. in sacco technique - excessive initial losses; rate of passage studies - expense and time consuming) render them unsuitable for routine use. These together with inaccurate starch assays (Krystallidou and Mould, 2004) and inappropriate rumen outflow kinetics, combine to produce a questionable data. Considering the role of starch in the nutrition of high producing dairy cows and its impact on the rumen fermentative environment, a system that accurately predicts both the extent and site of starch degradation would be of strategic importance. It was hypothesised that starch degradation in vitro is likely to be similar if not identical to that of the rumen. Thus starch outflow kinetics can be calculated using the difference between expected (in vitro ) and assayed rumen levels following a discrete starch meal. Further, the administration of an appropriate marker, with outflow kinetics similar to starch, will allow effective ruminal starch degradation to be estimated from in vitro data, using intact animals offered different feeding regimes