he objective was to test the hypothesis that increasing choice white grease (CWG) and adding a fat emulsifier to diets increase growth performance of pigs. The second objective was to determine the CWG equivalence of the fat emulsifier. Four diets contained corn, soybean meal, and distillers dried grains with solubles and 4 levels of CWG (i.e., 0, 2, 4, or 6 %). Two additional diets contained 0 or 2 % CWG and a fat emulsifier. A total of 192 pigs (initial weight = 29.9 ± 2.4 kg) were fed ad libitum for 28 days and allotted to the 6 diets with 2 pigs per pen (n = 16). Average daily gain (ADG), average daily feed intake (ADFI), and gain to feed (G:F) were calculated. Data were analyzed using the Proc Mixed of SAS. The statistical model included diet as fixed variable. Linear and quadratic effects of increasing CWG were tested and linear regression equations were developed. The CWG equivalence was then back-calculated using G:F of pigs fed the fat emulsifier diets. Overall, increasing CWG in diets increased (linear; P < 0.05) ADG and G:F of pigs, but ADFI was not affected. Supplementation of the emulsifier increased (P = 0.026) ADG of pigs without affecting ADFI or G:F. Regression analysis indicated that G:F increased (P < 0.05) by 0.00678 for each percentage unit change of CWG inclusion in diet, and G:F of pigs fed the fat emulsifier diets was similar to the G:F of pigs fed diets containing −1.1 % or 6.8 % CWG for the diets containing 0 and 2 % CWG, respectively. In conclusion, growth performance of pigs was improved by CWG and fat emulsifier. The effects of the fat emulsifier were close to 0 when no fat was used, which indicated that the presence of fat with saturated fatty acids is needed to obtain a response to the emulsifier. Although outside the range, G:F of pigs fed the 2 % CWG diet with the emulsifier was equivalent to G:F of pigs fed 6.8 % CWG diet, which suggests that the emulsifier may contain the energy equivalent to 4.8 % CWG (i.e., 343 kcal of net energy).
