Rapid degradation of barley grain (BG, Hordeum vulgare) starch in the rumen can seriously impair rumen26 fermentation efficiency. Some strategies to curb the negative effects of grain feeding and hamper dysfermentation27 rely on the usage of phytogenic substances or organic acids. In order to process BGs, they steeped in 5% lactic acid28 (BGLA), oregano (BGORE) or thyme (BGTHY) extracts for 48 h. Therefore, an in situ study was conducted to assess29 the effect of either processed barley grain (BG) or unprocessed BG (control; BGCTRL) on ruminal degradation30 kinetics (a; soluble fraction, b; potential degradable fraction, c; fractional degradation rate) and effective rumen31 degradability (ERD) of dry matter (DM), crude protein (CP) and starch. In vitro trials with a 2 × 2 × 4 factorial32 design were also used to assess the effect of diets which contained intact or processed BGs with different CP [16033 (P16) vs 170 (P17] g/kg DM,) and ruminal protein degradability percentages [90 (low degradability; LD) vs 11534 (high degradability; HD) g/kg DM] on rumen gas production characteristics (b; asymptotic gas volume, c; the35 constant rate of gas production), yield of microbial crude protein (MCP) and effective utilizable crude protein in the36 duodenum (EuCP). In vitro trials were also used to assess the effect of diets which contained intact or processed37 BGs with different CP [160 (P16) vs 170 (P17] g/kg DM,) and ruminal protein degradability percentages [90 (low38 degradability; LD) vs 115 (high degradability; HD) g/kg DM] on rumen gas production characteristics (b;39 asymptotic gas volume, c; the constant rate of gas production), microbial crude protein (MCP) and effective40 utilizable crude protein in the duodenum (EuCP). In situ data demonstrated that BGLA compared with BGCTRL had41 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 vs42 0.64, P=0.01). The treatment of BGs with the plant extracts, however, was not able to change the in situ parameters43 relatively to BGCTRL. Results of the in vitro trials indicated that diets containing processed BG had higher MCP44 when compared with BGCTRL (19.74 vs 15.85 mg/ 250 mg DM, P<0.01). Lactic acid and ORE-treated barley45 decreased the gas production constant rate (c; mL/ h) and gas volume after 2 h compared with BGCTRL (P≤0.05). Our46 study revealed that processed BG can alter the rumen starch degradation pattern, rumen gas production parameters47 and increase MCP and EuCP.

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