Effects of processing method, steaming duration and roller setting distance on ruminal degradability of barley grain

Whole barley kernel because of its intact pericarp is resistant to bacterial attachment in the rumen and digestion by ruminants. Therfore, barley processing is required to make its endosperm, encased within indigestible pericarp and hull layers, accessible to the microbial population in the rumen. This study was carried out to evaluate the effects of processing method (grinding vs. steam flaking) using completely randomized design and to investigate the impacts of steaming duration, roller setting, and interaction between steaming duration and roller setting on ruminal degradability of barley grain dry and organic matter in a 3 x 2 completely randomized factorial design.
Five grams (DM basis) of processed barley, ground barley using a hammer mill with a standard screen size of 3 mm (GB) or steamflaked barley (SFB) using 3 steaming times including of 35, 45 or 55 min. and 2 roller setting distances of 0.3 or 0.4 mm for each steaming time, were weighed into bags (10 × 20 cm) made of polyester (pore size, 50 m). Triplicate nylon bags were placed in the rumen of a non-lactating Holstein dairy cow for 0, 2, 4, 8, 16, 24, and 48 h, respectively, for each sample. The incubation was repeated three times. Residues of dry matter (DM) and organic matter (OM) per incubation time were analyzed using SAS software.
Processing method changed the density of GB (616 g/L), SFB (285 g/L on average) compared to whole barley grain density (684 g/L). Increasing the extent of barley flaking decreased the density from 390 to 180 g/L, and kernel thickness from 1.5 to 1.0 mm. Grinding of barley versus steam-flaking on average increased DM and OM disappearance (%) and raised (P Results of this study showed that processing method could change barley grain density, particle size and its distribution on sieves. Grinding versus flaking increased the effective degradability of grain DM and OM. Ruminal DM and OM degradability of barley grain could be manipulated by varying the duration of steaming and the distance of roller setting.