Effect of Processed Barley Grain on in vitro Rumen Fermentation and Fate of Nitrogen Metabolism.

Rapid degradation of barley grain (BG, Hordeum vulgare) starch in the rumen can seriously impair rumen fermentation efficiency. Some strategies to curb the negative effects of grain feeding and hamper dysfermentation rely on the usage of phytogenic substances or organic acids. In order to process BGs, they were steeped in 5% lactic acid (BGLA), oregano (BGORE) or thyme (BGTHY) extracts for 48 h. Therefore, an in situ study was conducted to assess the effect of either processed BG or unprocessed BG (control; BGCTRL) on ruminal degradation kinetics (a; soluble fraction, b; potential degradable fraction, c; fractional degradation rate) and effective rumen degradability (ERD) of dry matter (DM), crude protein (CP) and starch. In vitro trials with a 2 × 2 × 4 factorial design were also used to assess the effect of diets which contained intact or processed BGs with different CP [160 (P16) vs. 170 (P17)] g/kg DM,) and ruminal protein degradability percentages [90 (low degradability; LD) vs. 115 (high degradability; HD) g/kg DM] on rumen gas production characteristics (b; asymptotic gas volume, c; the constant rate of gas production), yield of microbial crude protein (MCP) and effective utilizable crude protein in the duodenum (EuCP). In situ data demonstrated that BG_LA compared with BG_CTRL had significantly lower fractions of “a” (0.22 vs. 0.26, P=0.03) and “c” (0.10 vs. 0.17, P<0.01) and ERD of starch (0.53 vs. 0.64, P=0.01). The treatment of BGs with the plant extracts, however, was not able to change the in situ parameters relatively to BG_CTRL. Results of the in vitro trials indicated that diets containing processed BG had higher MCP when compared with BG_CTRL (19.74 vs. 15.85 mg/250 mg DM, P<0.01). Lactic acid and ORE-treated barley decreased the gas production constant rate (c; mL/h) and gas volume after 2 h compared with BG_CTRL (P≤0.05). Our study revealed that processed BG can alter the rumen starch degradation pattern, and rumen gas production parameters and increase MCP and EuCP. [ABSTRACT FROM AUTHOR]