Effects of barley endosperm amylose and β-glucan content and hull processing on nutrient digestibility and growth performance in weaned pigs.

Barley endosperm contains mostly fermentable fiber (resistant starch including amylose and β-glucan). Instead, barley hull contains non-fermentable fiber whose fermentability might be increased by steam explosion. Barley fiber may benefit gut health and thereby enhance growth performance. The objective was to study effects of feeding barley endosperm with different amylose and β-glucan content and hull processing on diet digestibility and growth performance of weaned pigs. In nine randomized complete blocks, 216 weaned pigs housed in 54 pens were fed six diets containing 58% of either low amylose and β-glucan (LAB) or high amylose and β-glucan (HAB) barley endosperm, plus 8.5% of either (untreated) oat hull, (untreated) barley hull, or steam-exploded (StE) barley hull starting 1 week post-weaning for two 14-day phases. Diets provided 2.3 Mcal net energy (NE)/kg, and 5.5 g or 5.1 g standardized ileal digestible Lys/Mcal NE for phase 1 or phase 2, respectively. Data were analyzed as a 2 × 3 factorial arrangement with endosperm and hull as main effects. The hull-less barley grain with HAB endosperm contained 7.8%-unit more amylose and 1.5%-unit more β-glucan than dehulled barley with LAB endosperm. Microscopic images showed that steam explosion disturbed the structure of barley hull. In phase 1, endosperms and hulls interacted for diet apparent total tract digestibility (ATTD). Diet ATTD of gross energy (GE) and crude protein (CP) were greater (P < 0.05) for LAB than HAB endosperm when diets contained oat or barley hull, but not StE barley hull. In phase 2, diet ATTD of GE and CP were greater (P < 0.05) for LAB than HAB endosperm; diet ATTD of GE was greater (P < 0.05) for StE barley hull than barley hull; diet ATTD of GE and CP were lower (P < 0.05) for barley hull than oat hull. For the entire trial (d 0-28), an interaction (P < 0.05) was observed for average daily feed intake (ADFI). The ADFI of pigs was lower (P < 0.05) feeding HAB than LAB endosperm when combined with StE barley hull in diets. Average daily gain (ADG) was lower (P = 0.001) for pigs fed HAB than LAB endosperm, but ADG did not differ among hulls. Gain-to-feed did not differ between endosperms or among hulls. In conclusion, feeding diets with high amylose and β-glucan barley endosperm reduced diet total tract digestibility and weaned pig growth performance. Steam explosion of hulls increased diet digestibility in phase 2 but did not increase growth performance in weaned pigs.