Prediction of the apparent metabolizable energy content of fats fed to broiler chickens.
1991
Wiseman J. | Salvador F. | Craigon J.
Soybean oil and tallow acid oil were blended in the ratio 75:25, 50:50, and 25:75 to give 3 blends (A, B, and C) of increasing free fatty acid (FFA) content but decreasing ratio of unsaturated to saturated fatty acids (U:S). Tallow and soybean acid oil were blended in similar proportions to give three blends (D, E, and F) of increasing FFA content and increasing U:S ratio. The six fats were incorporated into a basal diet at rates of 40, 80, and 120 g/kg. Experimental diets were evaluated for apparent available fat (AAF) with broilers aged 1.5 and 7.5 wk of age. The AAF of fats was calculated from extrapolation of the regression of AAF of diets to rate of inclusion of fats. The AME of fats was determined as the product of AAF and gross energy. Increasing FFA content but reducing U:S ratio lowered the AME giving 31.1, 28.7, and 21.7 MJ/kg (1 MJ = 239 Mcal) and 33.2, 31.5, and 28.4 MJ/kg, respectively, for A, B, and C for young and old birds. Corresponding data for D, E, and F (increasing FFA content and U:S ratio) were 27.7, 28.0, and 29.4 MJ/kg and 31.8, 32.9, and 33.3 MJ/kg, respectively, for young and old birds. Data generated, together with results from previous reports, were subject to regression analysis. The AME of fats could be predicted from knowledge of U:S ratio and FFA content with equations accounting for 816 and 925 of the variation in AME values for young and old birds, respectively.
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