Abstract:

【Objective】 The objectives of this study were to investigate the relationships of shearing force with morphological characteristics, chemical compositions, and in situ degradability in 48 h of alfalfa (Medicago sativa L.) stem and Dongmu-70 rye grass (Secale cereale L.) stem. 【Method】 The diameter, length,weight and linear density of stem were measured after sample collection. Shearing force was measured. Meanwhile, the content of moisture were measured, neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, cellulose and hemicellulose were measured. Three Xiaowei sheep were used to determine in situ degradability in 48 h of DM and NDF of alfalfa stem and rye grass stem. 【Result】 The results showed that linear density, shearing force and lignin content of alfalfa stem increased as diameter increased. There were positive relationships of shearing force with diameter, linear density, and lignin content of alfalfa stem (P＜0.01). A negative correlation was found between shearing force and moisture content (P＜0.01). Negative correlations also were found between shearing force and DM degradability, NDF digestibility of alfalfa stem (P＜0.05). Linear density, stem thickness, ADF, lignin and moisture content increased when rye grass stem increased. There were positive relationships of shearing force with diameter, linear density, stem thickness, ADF, lignin and moisture content of rye grass stem (P＜0.05). In situ degradability of rye grass stem decreased with increasing shearing force, but the linear correlations were not significant (P＞0.05). 【Conclusion】 The results showed that the variance in stem shearing force of Alfalfa and rye grass are due to a combination of factors, including changes in chemical composition, morphological characteristics. DM and NDF degradability of alfalfa stem had negative relationships with shearing force. Shearing force could be used as an indicator of forage stem nutritive value. There were no negative relationships between shearing force and DM, NDF degradability of rye grass.

Key words: alfalfa')">alfalfa, Dongmu-70 rye grass, shearing force, morphological characteristic, chemical compositions, in situ degradability