Current pressures to extensify agricultural systems are leading to more emphasis on incorporating legumes, such as white clover, into swards thus reducing the amount of fertiliser nitrogen used. Cattle fed clover rich diets often receive poloxalene (Bloat guard ®, Agrimin Limited) as a feed additive to prevent bloat. Poloxalene is a surfactant, reducing surface tension of bubbles caught in froth, and thus reducing foam formation in the reticulo-rumen. The n-alkane technique (Dove and Mayes 1991) to measure intake is widely used in grazing experiments. Alkanes are saturated hydrocarbons found in the waxy cuticle of plants, which are used as internal markers to estimate herbage intake and to determine dietary composition in grazing ruminants. Animals are typically dosed with a controlled release bolus (CaptecTM FERNZ, New Zealand) containing an even-chained synthetic alkane (C32). Mean daily dry matter intake is calculated using the assayed release rate of C32 and the concentrations of C32 and C33 in herbage and faeces (Dove and Mayes, 1991). Given that poloxalene is a surfactant, it could potentially interact with the n-alkanes and therefore invalidate the technique. The aim of this experiment was to investigate the effect of including poloxalene in the diet on the n-alkane concentration in faeces from dairy cattle.