Ruminal and post-ruminal barley grain digestion and starch granule morphology under three heat methods

Abstract

This study was designed to investigate the effect of three heating methods on the ruminal and post-ruminal nutrient degradability and starch granule morphology of barley grain (BG - Hordeum vulgare). Treatments were Control (CG): without processing; Roasted (RG): roasted BG for 300 s at 130°C; Microwaved (MG): irradiated BG for 120 s at 1200 W; and Steam flaked (SG): BG misted for 30 min under steam flow of boiling water and flaked. Gas production and in situ techniques were used to evaluate the ruminal degradability of treatments, and a modified three-step method was utilised to estimate the total-tract digestibility. Morphological changes of starch granules were determined by field emission scanning electron microscopy (FESEM). Ruminal gas production and dry matter disappearance were increased (p < .05) in SG vs. CG. Heat processing had different effects on starch and crude protein degradability; however, starch degradability increased (p < .05) from CG to SG. Post-ruminal disappearance of dry matter in CG was greater (p < .05) than other treatments. These results validated by FESEM images that explained high barley grain degradability in relation to the number of holes on the surface of starch granules. Heat processing can enhance ruminal and post-ruminal utilisation efficiency of barley grain, resulting in improvement of total-tract digestibility.