176 Whole-grain fiber composition modifies phosphorus digestibility in grower pigs

Abstract

Abstract Increased fermentable carbohydrates in cereal grains due to more amylose in starch or β-glucan in fiber may increase endogenous losses including for P, and thereby reduce apparent total tract digestibility (ATTD) of P. This study assessed effects of barley cultivars varying in chemical composition on apparent ileal digestibility (AID) and ATTD of P and Ca, and standardized total tract digestibility (STTD) of P compared with wheat. In a 6 (period) × 5 (diet) Youden square, 7 ileal-cannulated barrows (27.7 kg initial BW) were fed diets containing 80% of 1 of 5 grains differing in amylose, β-glucan, and fiber: 1) high-fermentable, high-β-glucan, hull-less barley (HFB); 2) high-fermentable, high-amylose, hull-less barley (HFA); 3) moderate-fermentable, hull-less barley (MFB); 4) low-fermentable, hulled barley (LFB); and 5) low-fermentable, hard red spring wheat (LFW). Diet STTD of P was calculated by correcting ATTD for the basal endogenous P loss using a constant value of 190 mg P/kg DM intake. Whole grains contained between 8.5 to 16.3 µmol/g DM phytate (any salt of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate); InsP6) and 1.6 to 3.0 g/kg DM InsP6-P. Data were analyzed using a mixed model with diet as fixed effect, and pig and period as random effects. On DM basis (g/kg), diets contained 131 to 286 g neutral detergent fiber, 8.8 to 85.4 g β-glucan, and 8.1 to 8.9 g total P. The MFB, LFB, and LFW had greater (P < 0.001) AID of P than HFB and HFA, and MFB had greater (P < 0.05) ATTD or STTD of P than HFB. The LFW had greater (P < 0.05) ATTD of Ca than LFB, whereas diet did not affect (P > 0.05) AID of Ca. In conclusion, whole grains high in fermentable fiber, e.g. β-glucans, in specific hull-less and hulled barley cultivars decreased diet digestibility of P and Ca.