The role of dietary fats in efficiency of ruminants.

Fat increases energetic efficiency in lactating cows by increasing total energy intake, by generating ATP more efficiently (ATP/unit energy expended) than volatile fatty acids or protein, by direct incorporation into product, and by promoting nutrient partition toward milk production. Factors that limit utilization of large amounts of fat by ruminants include inhibitory effects on ruminal fermentation, lower intestinal absorption at high intake, low contribution to total oxidation of nutrients, and sensitivity to nutrient imbalance, causing reduced energy intake. Research has resolved many problems associated with effects on ruminal fermentation; research in the future may improve fat digestibility and reduce limits of oxidation. Effect of high fat on regulation of feed intake has received little attention.