Composition and amino acids ileal digestibility of wheat distillers dried grains and solubles in pigs: Sources of variability

In recent years, policies encouraging the production of ethanol from corn or wheat have stimulated an increased production of distillers dried grains with solubles (DDGS) whose nutritional value for pigs is little described. Seventeen wheat DDGS samples were obtained from 7 different plants in Europe from July to September 2007. Each sample was analyzed and 10 representative samples were measured for amino acids (AA) content and their standardized ileal digestibility (SID) in pigs. Lightness score (L) of each DDGS was also measured. Our results indicate a rather stable crude protein content (32.6 to 38.9% DM basis; average: 36.1% DM basis) whereas lysine was the most affected AA with contents ranging between 0.82 and 3.00% of crude protein (CP; N*6.25). In addition, lysine SID was also variable (9 to 82%) with the lowest values observed in DDGS with low lysine level in CP. In fact, samples with low lysine content in CP and low SID of lysine had low lightness values (L<50) and a subsequent high occurrence of Maillard reactions. Consequently, both lysine content (R=0.63) and lysine SID (R=0.68) values were positively correlated with lightness and DDGS samples that were lighter in colour had higher total and digestible AA levels. Our data indicate that lysine SID can be accurately predicted from lysine content in CP with a quadratic model (R-2=0.87) or a linear-plateau model (R-2=0.80 with a breakpoint for lysine content in CP of 1.9% and SID at plateau of 68%). This also suggests that wheat DDGS with lysine content in CP lower than 1.9% should be avoided in pig diets. (C) 2010 Elsevier B.V. All rights reserved.