White Leghorn hens in egg production were fed rations that contained 0, 3, 6, 9, 12, or 15% yellow grease. True metabolizable energy (TME) and nitrogen-corrected apparent metabolizable energy (AMEn) values of the rations were determined, and these data were used to estimate the TME and AMEn of yellow grease. An inverse relationship was observed between the level of yellow grease supplementation and the TME and AMEn values of this fat source. The TME and AMEn of yellow grease were 11,567 and 9,367 kcal/kg, respectively, when the supplemental level was 3%. Corresponding values when yellow grease constituted 15% of the ration were 8,907 and 8,653 kcal/kg, respectively. Variation in fatty acid composition of total dietary fat and associated changes in the TME and AMEn of yellow grease are discussed.
