The nutrients profile, ruminal degradability and fermentability of bitter vetch (BV) seed as an alternative home-grown protein source in comparison with soybean meal (SBM) for ruminants were determined using chemical composition, in sacco and in vitro techniques. The measured nitrogen fractions in this study were non-protein nitrogen (NPN), buffer soluble crude protein (BSCP), neutral detergent insoluble crude protein (NDICP) and acid detergent insoluble crude protein (ADICP). In Sacco DM and CP degradability values were estimated, using four steers equipped with permanent ruminal fistula. In vitro gas production of samples was conducted according to the standard procedures. Results revealed differences between two feeds in term of basic chemical composition. In crude protein (CP) fractions, BV seeds had a higher non-protein nitrogen and buffer soluble CP fraction than SBM, while the neutral detergent insoluble CP and acid detergent insoluble CP fractions did not differ between two feeds. In Sacco rapidly degradable fraction (a), degradation rate (c), potential degradability (PD) and effective degradability (ED) for dry matter (DM) content did not differ between two feeds while the slowly fermentable fraction (b) of the DM was significantly higher for BV. The in Sacco ‘a’ and ‘ED’ parameters for CP content were significantly higher for BV seeds than those for SBM, whereas, the ‘b’ fraction was significantly greater in SBM, but the ‘c’ and ‘PD’ fractions were similar. During the incubation period the gas production potential (fraction b) was significantly (P<0.05) higher in BV than that for SBM. Calculated organic matter digestibility for both feeds was similar while calculated metabolize energy content was significantly higher for SBM than that for BV. It was concluded that BV seeds can be considered an alternative feed and a suitable source of nutrients for ruminant animals in Iran.

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