Precaecal amino acid digestibility of different wheat cultivars in broilers

It was the objective of this study to determine the variability in precaecal digestibility of amino acids in 3 wheat cultivars in broilers when a xylanase was included in the diet. Also, the xylanase effect on the digestibility of amino acids from the Alidos cultivar was studied, because this cultivar had a high concentration of soluble non-starch polysaccharides. Three-week-old broilers were fed diets with 300, 500 and 700 g/kg wheat for 7 days. Six replicated pens of 12 broilers were used per treatment. Digesta was collected from the terminal ileum to determine the viscosity of the digesta and digestibility. The digestibility of amino acids from wheat was calculated by linear regression analysis. Significant effects of wheat inclusion levels on digesta viscosity were detected only when the diet was not supplemented with xylanase. In the presence of xylanase supplementation, amino acid digestibility of wheat was on a high level. The digestibility ranged from 83 to 91% for lysine, 85 to 93% for methionine, 78 to 92% for threonine, and 84 to 95% for valine. For the other amino acids, the differences were in a similar range. The differences between cultivars were not statistically significant. When Alidos cultivar was used without supplemented xylanase, the digestibility of essential amino acids was reduced by 9%-units on average. This difference was statistically significant for most of the amino acids studied. It was concluded that, although xylanase supplementation can reduce the antinutritive properties of pentosans in wheat and equalise digesta viscosity, a variation in amino acid digestibility of wheat between cultivars remains. The positive effect of xylanase on amino acid digestibility of wheat containing high levels of pentosans was confirmed.