Grass is the main energy feed for cattle but it declines in digestibility and intake during the summer months and loses about 20% nutrients during ensiling and feeding in winter. Grass is also low in minerals and this has implications for cattle health and performance. It is thus essential to use supplements to boost digestibility and intake of grass and subsequently the performance of cattle. This study compared the effect of two supplements which are marketed as molasses based feed blocks (Booster with 12% crude protein or CP and HIPRO with 28%: CRYSTALYX) on the in vitro dry matter (DM) degradation of barley straw (Straw) and grass nuts (Grass). These blocks contained same energy (13MJ ME/kg DM) but different amounts of sugars (33-35%), oil (6-8%) and minerals (20 to 28%) and thus were considered appropriate for use as feed supplements to compensate for the deficits of nutrients that the cattle can face when consuming grass or straw. These forages represent a range of forage quality that can be found in the UK.