Variation Laws And Correlations Of Shearing Force And Feed Nutritional Characteristics Of Crop Straws

Corn stalk, wheat straw and rice straw harvested in maturation stage and wheat straws atdifferent storage time were selected to study the correlations of shearing force values and feedcharacteristics including morphological index, nutrition compositions and ruminaldegradation. Feasibility of evaluating the nutritional value of crop stalks with shearing forcevalues was analysed.Shearing force, diameter, thickness, linear density （weight per unit length of stem）, andnutrition compositions of corn stalk, wheat straw and rice straw harvested in maturation stagewere measured. Ruminal degradation of dry matter （DM）, neutral detergent fiber （NDF） andacid detergent fiber （ADF） of straws were determined with nylon bags method. The resultsshowed that there were significant differences of shearing force, morphology index （lineardensity, diameter and thickness） and shearing force/linear density among three straws （P <0.05）. Positive correlations between shearing force and linear density, diameter, and thicknesscould be seen in three straws （P <0.001）. Correlation between linear density and shearingforce of three straws is highest （P <0.05）. Moreover, sensitivity of shearing force for lineardensity in corn stalk is higher than that in the other two straws. Correlations between shearingforce and nutrition compositions and ruminal degradation of DM and NDF were differentamong three straws （P <0.05）. It was more accurate to forecast ruminal degradation of NDFwith shearing force than the other nutrition compositions of straws. Shearing force wasappropriate for predicting the nutrients content and their ruminal degradations in corn stalkand rice straw.600wheat straws （Jimai22） were randomly selected and placed in a cool and ventilatedplace. Samples were collected in the1^st,15^th,30^th,45^th,60^thday after harvest to measureshearing force, morphological characteristic, nutrition compositions. Ruminal degradation ofDM, NDF and ADF of wheat straws were determined by nylon bags method. The results demonstrated that linear and quadratic effects of storage time on all the tested morphologicalcharacteristics were significantly correlative （P <0.0001）. As storage time goes on, all thetested nutrients and their ruminal degradations of wheat straws were linearly （P <0.0001） andquadratically （P <0.0001） correlative except ADF content which had a linearly correlativetrend （P=0.086） and ruminal degradation of ADF which had no significant correlative.Significant correlations were determined in linear effect of shearing force on morphologicalcharacteristics （P <0.0001）, and linear density and diameter were the more sensitive predictorthan stem thickness for shearing force. There were strong correlations between storage timeand all the measured physical characteristics （shearing force, morphological characteristicsand shearing force adjusted by morphological characteristics）（P <0.0001）. Nutritioncompositions were linearly correlative with shearing force and shearing force adjusted bymorphological characteristics （P <0.01）. Moisture, DM, OM and CP content had intensivelycorrelations with shearing force and adjusted shearing force （P <0.0001）. The linearcorrelation between ruminal degradations of DM and NDF and shearing force and adjustedshearing force were evidently （P <0.0001）. The positive correlations were strong betweenruminal degradations of DM and NDF and different storage time （P <0.0001）. There werevarying degrees correlations between shearing force and storage time, nutrition compositionsand ruminal degradations of DM and NDF, and shearing force was appropriate for predictingruminal degradations of NDF.In conclusion, there were correlations between shearing force and nutritioncharacteristics of the three crop straws. Nutrition compositions, morphological indexes andrumen degradations of nutrients （DM, NDF and ADF） can be predicted by shearing force tovarying degrees. The shearing force, nutrition compositions and their rumen degradations ofwheat straw are still dynamic with storage time after harvest. Correlation could be foundbetween shearing force and nutrition characteristics of wheat straws. Nutrient content,morphological index and rumen degradations of DM and NDF could be predicted by shearingforce to varying degrees. Shearing force can be applied as an indicator of nutritive value ofcorn stalk and rice straw more suitable than wheat straw. The sensitive of predicting thenutritive value of crop straws with shearing force was different among crops. Shearing forceshould be applied according to storage time when it was used to forecast the feed value of wheat straws.