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Starch and fiber characteristics of barley influence site of energy digestion in ileal-cannulated grower pigs
Chemical components of cereal grains such as amylose, β-glucan (BG), and total dietary fiber (TDF) may influence energy digestion in the gut. The objective was to determine the association between composition of barley and wheat and the site of energy digestion in pigs. Seven ileal-cannulated barrows were allotted to a 6 (periods) × 7 (diets) Youden square. Five cereal grain diets included (% amylose, β-glucan, and TDF): 3 hulless-barley cultivars: diet 1, CDC Fibar (0, 10, 22); diet 2, CDC Hilose (13, 7, 18), diet 3, CDC McGwire (11, 5, 15); 1 hulled barley, diet 4, Xena (12, 4, 17); and 1 hard red spring wheat, diet 5, Utmost (12, 1, 14). Two reference diets, an N-free and a protein-energy mix, were included to calculate ingredient digestibility. Test diets included 80% cereal grain and were fed at 2.5 × maintenance. Feces and ileal digesta were sampled after a 5-d adaptation. The AID of GE, DM, and starch was lowest (P < 0.05) for Fibar (43, 42, 73%) and Hilose (48, 47, 69%) vs. McGwire (68, 67, 84%), Xena (65, 64, 92%) and Utmost (78, 80, 93%). In contrast, hindgut fermentation of GE, DM, and starch was greatest (P < 0.05) for Fibar (45, 46, 26%) and Hilose (48, 41, 30%) vs. McGwire (23, 23, 16%), Xena (17, 16, 8%), and Utmost (11, 14, 7%). Thus, Fibar and Hilose did not differ (P > 0.05) in ATTD of DM and GE from Utmost. McGwire had the greatest (P < 0.05) ATTD of DM and had a greater (P < 0.05) ATTD of GE than Fibar, Hilose, and Xena but equal to that of Utmost (P < 0.05). Specifically, ATTD of DM was 90 vs. 87, 88, 81, and 88% and ATTD of GE was 91 vs. 88, 88, 83 and 89%, respectively, for McGwire vs. Fibar, Hilose, Xena, and Utmost. Starch ATTD did not differ among cereal grains (P > 0.05). Hulled barley, Xena, had an ATTD of GE and DM lower (P < 0.05) than all other cereal grains. Thus, the DE was lower (P < 0.05) in Xena than all other cereal grains, which did not vary (P > 0.05). In conclusion, a greater content of amylose, BG, and TDF in cereal grains decreased energy digestion in the small intestine and increased hindgut fermentation of energy, which may support maintaining pig gut health.
Keywords: grain, starch, fiber