Influence of Sample Dividing Method on Forage Quality as Determined by Nirs
Forage samples collected in the field are normally dried, coarsely ground, and subdivided to minimize time and expense required for secondary grinding, facilitate ease of sample handling, and reduce space needed for sample storage. The objective of this research was to determine the efficacy of four sample dividing methods to produce uniform subsamples for near infrared reflectance spectroscopy (NIRS) analysis. Sample dividing methods were: (1) quarter sectioning with a straight edge, (2) use of a gravimetric dividing apparatus, (3) mixing in a blender then dividing by quarter sectioning, and (4) mixing in a blender and dividing with a gravimetric dividing apparatus. Dividing method efficacy was evaluated by comparison of subsample quality. Average coefficients of correlation (r) between subsamples obtained using the divider apparatus were 0.97 and 0.08 for crude protein (CP) and acid detergent fiber (ADF), respectively. These r values were 4 and 6% higher for CP and ADF, respectively, than those obtained using the quarter sectioning method. However, r of the quarter sectioning method averaged for both CP and ADF improved nearly 7% by mixing the sample before dividing. The gravimetric dividing apparatus was superior to the quarter sectioning method in uniformly dividing both mixed and unmixed forage samples.
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