A comparison of waxy versus non-waxy wheats in diets for weaner pigs: effects of particle size, enzyme supplementation, and collection day on total tract apparent digestibility and pig performance

An experiment with a 2 × 2 × 2 factorial arrangement of treatments was conducted to examine effects of wheat (waxy versus non-waxy), particle size (mean particle size 580 μm versus 920 μm), and supplementation of enzyme (with or without xylanase + β-glucanase) on the coefficient of total tract apparent digestibility (CTTAD) measured at both 7 and 21 days after weaning. Waxy wheat contained less crude protein (CP), less starch, a lower amylose:amylopectin ratio, more non-starch polysaccharide (NSP), and had a higher in vitro extract viscosity than non-waxy wheat. Pigs fed the waxy wheat had a higher CTTAD of starch (P < 0.05) and tended to have a higher CTTAD of crude protein (P = 0.058). The reduction in particle size significantly increased the CTTAD of starch (P < 0.001). The CTTAD of gross energy (GE) was not influenced by different wheat type or particle size. The enzyme improved the CTTAD of starch (P < 0.01) and tended to improve the dietary digestible energy (DE) content (P = 0.056), but not that of other dietary components. However, the efficacy of the enzyme on DE content tended to influenced by a wheat by enzyme interaction (P = 0.069), such that the enzyme more effectively improved DE content with the waxy wheat (16.3 MJ/kg dry matter (DM) versus 15.6 MJ/kg DM) compared to the non-waxy wheat (15.8 MJ/kg DM versus 15.8 MJ/kg DM). The CTTAD of CP was influenced by a particle size by enzyme interaction (P < 0.01), such that enzyme supplementation increased the CTTAD of CP in a larger particle-sized diet (0.74 versus 0.72), while it decreased the CTTAD of CP in a finer particle-sized diet (0.71 versus 0.75). The CTTAD of CP but not starch and gross energy was increased at 21 days compared to that at 7 days after weaning. No significant effects of wheat, particle size, and enzyme were observed on daily gain, feed intake, and feed efficiency, although a wheat by enzyme interaction for daily gain (P < 0.05) and a wheat by particle size × enzyme interaction for feed intake (P < 0.05) were observed. In conclusion, waxy wheat, a smaller particle size, and enzyme supplementation were beneficial for starch digestibility, and weaned pigs increased their ability to digest protein with increasing age.