The effect of the 1B/1R translocation and endosperm texture on amino acid digestibility in near-isogenic lines of wheat for broilers

Four near-isogenic lines of wheat were employed to compare the effects of e ndosperm texture (hard v. soft) and the presence or absence of the 1B/1R tr anslocation on amino acid digestion as determined with young broilers. Whea t samples were incorporated into diets at rates of inclusion of 250, 500 an d 750 g/kg, with wheat as the only protein source. Diets included a mineral /vitamin mixture (50 g), oil (50 g) and were made up to 1000 g with a 50:50 starch:glucose mixture. Titanium dioxide was included at 5 g/kg as an iner t marker. Each of the 12 diets was fed to 6 pairs of growing male (Ross) ch ickens for 3 days. Samples of ileal digesta were obtained from the birds fo llowing slaughter at 21 or 22 days of age and analysed for amino acid and t itanium dioxide content. True and apparent digestibility coefficients were determined by regressing the amount of dietary apparently digestible amino acid in the diet against the rate of wheat inclusion and extrapolating the response to 1000 g and 0 g wheat/kg. The ordinate intercept was assumed to represent endogenous losses. Both the presence of the translocation and har d endosperm texture were associated with decreases in the apparent digestib ility of amino acids, although the latter characteristic was not as importa nt. As examples, for methionine the translocation was associated with a dec rease in the coefficient of digestibility from 0.872 to 0.802 and a change in endosperm texture from soft to hard was associated with a decrease from 0.845 to 0.829.