Morphology and chemical composition of pearling fractions from kernels of hulless barleys and other cereal grains and the nutritional significance of arabinoxylans from the barleys in the diets of young pigs

Causal factors for differences in feeding value between Falcon and Bear hulless barleys were investigated. The barleys were pearled to yield AX-rich fractions and digestibility, metabolism and performance trials were conducted to examine the nutritional significance of Arabinoxylans (AX) in the diets of young pigs. Results of morphology and chemical composition studies of the pearling fractions from both barleys, showed essential nutrients, AX and acid detergent fiber (ADF) were more concentrated in the pericarp/testa, aleurone and germ than in the endosperm cell wall and starchy endosperm of whole kernels (Wk). Bear fractions and Wk contained more essential nutrients and less AX and ADF than those of Falcon. The in vitro dry matter disappearance (IVDMD) of the outer fractions of Bear was higher (P < 0.05) than of those of Falcon. There were correlations (P < 0.05) between total AX, and water-soluble AX of fractions of both barleys, and their respective gastric IVDMD (r = --0.62 and --0.90), ileal IVDMD (r = --0.83 and --0.61) and total IVDMD (r = --0.83 and --0.84). Compared to the Wk, feeding diets based on the AX-rich fractions of Falcon (FF) or Bear (BF) decreased (P < 0.05) the percentage digestibility of ADF (26.2 vs. 35.9 for Falcon, 47.6 vs. 50.8 for Bear), and AX (72.0 vs. 76.8 for Falcon, 74.0 vs. 77.7 for Bear). The digestibility of beta-glucans was not affected by diet. The AX-rich fraction diets were lower (P < 0.05) than the Wk diets in DE, kcal/kg (3281 vs. 3433 for Falcon, 3360 vs. 3568 for Bear) and ME, kcal/kg (2937 vs. 3148 for Falcon, 3036 vs. 3278 for Bear). Feeding the whole kernel diets of Falcon or Bear resulted in higher (P < 0.05) daily feed intake than feeding the FF and BF diets. Daily feed intake, daily gain and gain-to-feed ratio (G/F) were not different (P > 0.05) when the pigs were fed the FF or BF diets. Xylanase supplementation decreased (P < 0.05) feed intake and increased G/F of pigs fed the BF diet but not that of those fed the FF diet. These results suggest that AX decrease utilization of energy, digestibility of fiber components, and performance in young pigs fed hulless barley based diets, especially when fed the Falcon cultivar.