The current study was conducted to determine the chemical composition and gas production properties of different nut hulls that were included to almond, peanut and walnut hulls. In this experiment, in a completely randomized design, three different nut hulls, after drying, were ground to pass a 2 mm sieve and used for determination of chemical composition and in vitro gas production. Results showed that there were no differences among treatments for DM and EE level (P>0.05). But, the CP, NDF, ADF, and Ash content in peanut hulls was significantly higher than almond and walnut hulls (P<0.05). Also, the hemicellulose content of almond hulls was higher than peanut and walnut hulls (P<0.05). The volume of gas produced during 96 h for almond hulls was significantly higher than peanut and walnut hulls (P<0.05). Also, the potential gas production (b) of almond hulls was higher than other treatments (P<0.05). But, the constant rate of gas production (c) was same for all treatments (P>0.05). Besides, the OMD, NEl, ME, and SCFA content of almond hulls was significantly higher than peanut and walnut hulls (P<0.05). Overall, it seems that of these agricultural by-products, although all three have high levels of fiber, but the nutritional value of almond hulls was higher than other hulls.

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