Regulated ReleaseTM (RR) is a patented liquid feed technology designed to reduce costs associated with protein supplementation. By causing the rate of ammonia release to mimic that of feed protein, through complexing urea and sugars, RR allows urea to act as a cost-effective ammonia source. However as molasses is used as the carrier it is difficult to demonstrate the efficacy of this technology using standard feed evaluation methodologies such as the artificial fibre bag technique of Ørskov et al. (1980). However the Reading Pressure Technique (RPT, Mauricio et al., 1999) can evaluate such feeds in vitro and the opportunity was therefore taken to examine the ability of RR to alter the rate and extent of fermentation by comparing a blended molasses with three RR molasses-based liquid feeds. As the majority of the CP in these feeds originates from urea rather than true protein, little if any gas will be produced from CP degradation. It was therefore hypothesised that an alteration in measured gas production, relative to that of Stockmol 20, would be due to the influence of RR technology limiting carbohydrate fermentation.