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A total of 96 pigs (initially 35.11 kg) were used in a study of 214-d to determine the effect of standardized ileal digestible (SID) tryptophan to large neutral amino acids (LNAA) ratio on growth performance of finishing pigs. Pens of pigs were balanced by initial weight and randomly allotted to 1 of 4 dietary treatments in a completely randomized design with 4 pigs per pen and 6 replications per treatment. Experimental diets were fed in 2 phases: early finishing phase (35 to 48 kg BW) and late finishing phase (83 to 98 kg BW), with a common diet fed in between. Dietary treatments included: (1) a corn-soybean meal-based diet without dried distillers grains with solubles (DDGS), (2) a corn-soybean meal-based diet with 45% DDGS, (3) a corn-soybean meal-based diet without DDGS but supplemented with similar amounts of LNAA as the diet containing 45% DDGS, and (4) the LNAA-supplemented diet with added crystalline tryptophan to increase the SID tryptophan:LNAA ratio. The diets were formulated in a similar manner for the late finishing phase with the exception that DDGS were lowered to 30% of the diet. In the early finishing period (35 to 48 kg BW), pigs fed 45% DDGS diet had poorer F/G (2.48 ± 0.07) compared with pigs fed the other diets (ranged from 2.15 to 2.22; P = 0.01); however, no differences were found in other response criteria. During the late finishing period (83 to 98 kg BW), pig growth performance was not affected by dietary treatment.
These results suggest that the high level of LNAA relative to tryptophan in diets containing 30% DDGS or greater may not be responsible for the apparent increase in the tryptophan requirement of finishing pigs seen in previous studies.
S Nitikanchana, MD Tokach, SS Dritz, JL Usry, JM DeRouchey, RD Goodband, JR Bergstrom, J L Nelssen. 2011. Determining the effect of the ratio of tryptophan to large neutral amino acids on the growth performance of finishing pigs. Swine Day Kansas State, 174 - 181.
