Ileal digestibility of amino acids in wheat distillers dried grains with solubles for pigs

In recent years, policies encouraging the production of ethanol from cereals have resulted in increased production of distillers dried grains with solubles (DDGS). Unlike corn, DDGS nutritional value and its variability for pigs is poorly described for wheat DDGS. Seventeen wheat DDGS samples were obtained from seven plants in Europe. Each sample was analysed for chemical composition and 10 representative samples were analysed for amino acids (AA) concentration and their standardized ileal digestibility (SID) in pigs. Luminance (L) of the DDGS was also measured. Results indicate a rather stable crude protein (CP; N×6.25) concentration (326–389 g/kg DM; average: 361 g/kg DM) but the AA profile was variable among samples. Lysine (lys) concentration was the most variable with values ranging between 0.83 and 3.01 g/100 g CP. Only 76% of total lys was available if measured by the fluoro dinitro benzene procedure and 85% was available when measured by the furosine procedure. The SID of lys was also highly variable (0.09–0.83) with the lowest values observed for the three samples that had a low lys concentration in CP. These latter samples had also a high occurrence of Maillard reaction products and low L values (<50). Consequently, both lys:CP (r = 0.63) and SID of lys (r = 0.68) were positively related with L. The data indicate that lys SID can be accurately predicted from lys:CP according to a quadratic (R2 = 0.86) or a linear-plateau model (R2 = 0.80; breakpoint for 1.9 g lys/100 g CP and a 0.68 plateau SID value). The SID of other AA was less variable than that observed for lys. The results of the current trial indicate that variability in lys concentration and its SID represent a major concern when wheat DDGS are fed to pigs. The combination of low lys content in CP and low SID of lys in dark DDGS suggests not including such type of ingredient in feeds for pigs.