This experiment was conducted to investigate effect of adding different levels (0, 2, 4 and 6%) of barley on potato plant silage degradability were studied by In vitro gas producing technique. Gas production test with mixtures of filtered rumen liquid of three Holstein male cattle rumen in times of 2, 4, 6, 8, 16, 24, 48, 72 and 96 hours were performed. Chemical compositions for dry matter, crude protein, NDF were27, 10.16, and 34%, respectively. The results showed that gas volume at 16h incubation (for different treatments), were 33.6d, 36.6c, 40.6b and 42.6a ml/200mg DM for potato plant silage. The gas production from soluble fraction (a4%), and from insoluble fraction (b4%), rate constant of gas production during incubation (c4%) and the potential gas production (a+ b4%) contents of potato plant silage were 20.9a (ml/200mg DM), 54.2a (ml/200mg DM), 0.046a (ml/h) and 67.4a(ml/200mg DM), while for level control were 10.6d (ml/200mg DM), 47.3c (ml/200 mg DM), 0.04b (ml/h) and 57.9d (ml/200 mg DM).This study demonstrated that the potato silage barley (PSBa),have the potential to use as out se of forage for ruminal nutrition.

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