Milk from ewes is characterized by a high fat content and ratio of fat to protein, but for most full fat type cheeses the high fat content is a disadvantage as the excess is lost in the whey. Trans-10, cis-12 conjugated linoleic acid (CLA) has been shown to be a potent inhibitor of milk fat synthesis in dairy cows and more recently in sheep (Sinclair et al., 2005), and therefore represents a suitable management tool to reduce fat yield. In addition to a reduction in milk fat output, under some circumstances trans-10, cis-12 CLA results in an increase in milk and milk protein yield, particularly when the animal is under supplied with dietary energy. The objectives of this study were to examine the effects of supplementing dairy ewes with a rumen protected source of trans-10, cis-12 CLA at a high and low level of energy intake on milk fat synthesis, energy metabolism and cheese yield.