The objective of this study was to investigate the effect of treatment of whole barley grain (WBG) with sodium hydroxide (NaOH) on in vitro rumen gas production parameters and microbial protein synthesis. Experimental treatments included untreated whole barley grain (BControl) and treated barley grain with NaOH ‏ water (35 g ‏ 220 ml/kg DM WBG) for 30 days (BNaOH). In vitro gas production technique was used to determine the gas production parameters of the samples. Furthermore, gas volume, apparent substrate degradability of barley grain (ASD), true substrate degradability of barley grain (TSD) and microbial N at t1/2 for two treatments were measured. The amount of produced gas at each time of incubation in each glass serum bottle was taken as the gas production parameter. Results of the in vitro technique revealed that alkali treatment of WBG caused a significant increase in the asymptotic gas volume (b) versus BControl (113.71 and 162.86 ml, respectively). Constant rate of gas production (c) significantly decreased by BNaOH compared with BControl (0.018 and 0.034 ml/h, respectively). No effects of NaOH treatment were observed on ASD and TSD of whole barley grain. However, rumen microbial-N yield considerably ( p , 0.05) built up (from 1.922 to 4.087 mg) from the treatment of barley with NaOH. The finding of the present study leads us to conclude that treatment of WBG with NaOH improved in vitro gas production parameters and microbial protein synthesis.

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