The Metabolizable Energy Determination of Fats and Oils in Broiler Chickens.

Four trials using chicks were conducted to measure the metabolizable energy (ME) of fats, oils and combinations of these using a relatively fat free basal diet. The objective was to determine if ME values for fats and oils could be measured which did not exceed their gross energy values. The effects of fecal drying temperature on ME, level of fat or oil inclusion on ME, reference source (glucose or soybean oil) and response of sex on ME were also studied. In Trial 1 the ME of soybean oil (SBO) and tallow at 5, 10, and 15% replacement were calculated based on glucose of SBO as the reference material. No differences were noted when ME values were measured based on glucose or SBO as a reference material. The 10% level of fat or oil inclusion had a significantly higher ME than the 5 or 15% level of inclusion. Trial 1 also evaluated the effect of varying fecal drying temperature on ME measurement. The ME value measured at 70 C for SBO (9.92 kcal/g) was significantly higher than the observed value for SBO at 105 C (9.44 kcal/g). Metabolizable energy values for tallow and blends of SBO and tallow were measured in Trial 2. Results indicated that ME of diets containing only tallow were statistically lower than the SBO:tallow blends of 2:8 and 4:6. The ME of the 6:4 and 8:2, SBO:tallow blends, were statistically higher than all others. The ME values measured for the energy scoures in Trial 2 were equal to or less than their respective National Research Council-77 (NRC-77) values within the exception of the 6:4 (SBO:tallow) blend, which was statistically higher than its calculated NRC-77 value. In trials 3 and 4, ME values measured for fish oil, lard and olive oil were all observed to be less than their calculated NRC-77 values. ME values for poultry fat and coconut oil were measured to be equal to their NRC-77 values. Male and female chicks were observed to utilize energy sources different only in Trial 4. The ME value of the females was 7.63 kcal/g whereas the male ME value was 7.25 kcal/g