A total of 1,210 growing gilts (initially 102.4 lb, PIC) were used in a 28-day study in
a commercial research facility to determine
the effects of added synthetic amino acids, with decreasing amounts of fat, on growth
performance of growing pigs. Pigs were fed one of four experimental diets based on cornsoybean meal: 1) control (3% added fat, no synthetic amino acids), 2) 2.38% added fat and high concentrations of synthetic amino acids; 3) 1.90% added fat and high concentrations of synthetic amino acids, and 4) 1.43% added fat and high concentrations of synthetic amino acids. The amounts of added fat were chosen to equalize the energy content of the diet, according to a modified ME basis, with the ME value of soybean meal being set at 95, 90, and 85% of the ME of corn in Treatments 2, 3, and 4, respectively. Overall (d 0 to 28), pigs fed diets containing high concentrations of synthetic amino acids tended to have decreased ADG (P<0.09) and poorer F/G (P<0.11) than those of pigs fed the control
diet. Linear and quadratic trends for ADG, ADFI, and F/G, with decreasing amounts of
added fat, were not significant. The results of this study indicate that decreasing the amount of added fat when high concentrations of synthetic amino acids are added to the diet causes a numerically reduced ADG and poorer F/G.
