The objectives of this study were to investigate the effects of morphological characteristics on shearing force, the relationship between shearing force vs chemical composition, and shearing force vs in situ digestibility of alfalfa stem(Legume grass), lolium perenne (Gramineous grass) stem, sweet potato (Vine crop) vines and ginger (Economical crop) stem. According to stem biological characteristics, researches on alfalfa and lolium perenne were based on the whole stems, meanwhile, researches on sweet photo vines was based on segments(Top, Middle and Bottom segments), and ginger stems was based on segments(Top and Bottom segments), too. Shearing force, dimaeter and linear density of stem were measured. Moisture, NDF, ADF, lignin, cellulose and hemicelluloses contents were analyzed. Three Xiao Wei sheep were used to determine in situ digestibility of DM and NDF. The important factors that effected shearing force and the relationship between shearing force and in situ digestibility of DM and NDF were studied by compare analysis and linear regression.The studies of alfalfa and lolium perenne stem showed that linear densities and shearing forces of alfalfa and lolium perenne stem increased as their diameter increased(P < 0.05). There were positive correlations between shearing force and diameter, linear density(P < 0.01) and a positive correlation was also found between shearing force and stem thickness of lolium perenne(P < 0.01). Shearing forces increased as lignin contents increased of alfalfa and lolium perenne stems(P < 0.05). There were positive relationships between lignin content and shearing force (P < 0.01). In situ digestibility of DM and NDF decreased as shearing force increased of both alfalfa and lolium perenne. A negative correlation was found between shearing force and dry matter (DM) digestibility (P < 0.05), and there was also a negative correlation between shearing force and NDF digestibility (P < 0.05) of alfalfa stem. However, correlations between shearing force and in situ digestibility of DM and NDF of lolium perenne stem were not significant(P > 0.05). Diameter and linear density were more important than chemical composition in affecting shearing force of alfalfa and lolium perenne stem. There were positive relationships between lignin content and shearing force. In situ digestibility of DM and NDF of alfalfa and lolium perenne stem decreased with increasing shearing force, and negative correlations were found between shearing force and DM digestibility, NDF digestibility in alfalfa stem.The shearing force of top segment was smaller than middle segment and bottom segment of sweet photo vines(P < 0.05). Shearing force of all segments increased as their diameters, linear densities increased. Positive relationships were found between shearing force and diameter, linear density(P < 0.01). Moisture content decreased and lignin content increased as sweet photo vines ageing. Negative relationships between shearing force and moisture content, and positive correlations between lignin content and shearing force of all segments were found in this study. In situ digestibility of DM and DNF decreased as sweet photo vines ageing. However, the linear correlations between shearing force and in situ digestibility of DM, DNF were not significant. Diameter and linear density were important factors effected shearing force. Lignin was the chemical composition which effected shearing force. In situ digestibility decreased with increasing shearing force, but the linear correlations were not significant in sweet photo vines.Shearing force, long axis, minor axis and sectional area of top sgement were smaller than bottom segment of ginger stem. Shearing force increased as inceasing long axis. There were posotive relationships between shearing force and long axis(P < 0.01), sectional area(P < 0.01). Positive correlations between lignin content and shearing force of all segments were found(P < 0.05). In situ digestibility of DM and DNF of top segment were higher than bottom segment. Negative relationships between shearing force and in situ digestibility of DM and DNF of all segments were found. Shearing force of ginger stem were effected by long axis and sectional area. There were positive relationships between lignin contents and shearing force ginger stem. Negative correlations were found between shearing force and DM digestibility, NDF digestibility in ginger stem.The results showed that there were significantly relationships between shearing force and morphological characteristics. Lignin content was the most important chemical composition in affected shearing force. Correlations between shearing force and in situ digestibility of DM and NDF differs from different forages. Negative correlations were found between shearing force and DM digestibility, NDF digestibility in alfalfa stem and ginger stem, and shearing force could be used to predict the forage value of alfalfa stem and ginger stem. In situ digestibilities of DM and NDF decreased with increament of shearing force, but the linear correlations were not significant in lolium perenne stem and sweet photo vines. |