NEAR-INFRARED REFLECTANCE SPECTROSCOPY PREDICTION OF QUALITY FROM MASTICATED TEMPERATE FORAGE SPECIES

Masticated forage provides information related to the quality and frac tionation characteristics of a ruminant's diet. This study reports the use of near infrared reflectance spectroscopy (NIRS) to predict the i n vitro dry matter disappearance (IVDMD), in vitro organic matter disa ppearance (IVOMD), and cell-wall concentrations of particle size fract ions and the whole masticate of temperate forages. Esophageal extrusa samples, with saliva retained, were obtained from fistulated steers (B os taurus) that were intermittently grazing tall fescue (Festuca arund inacea Schreb.), orchardgrass (Dactylis glomerata L.), and ryegrass (L olium perenne L.). Grazing was initiated at canopy heights of 100, 200 , and 300 mm during spring and fall of two consecutive years. Samples were collected at the start of grazing at each canopy height and after defoliation to a 50-mm residue. Masticates, quick-frozen in liquid N- 2, were subsequently lyophilized and dry sieved into seven particle si ze fractions and, along with a whole-masticate subsample, were scanned for MRS analyses. A single broad-based calibration encompassing all e xperimental factors predicted quality constituents within acceptable l imits of precision for this methodology. Standard errors of cross-vali dation (SECV) were 6 g kg(-1) for organic matter, 16.0 g kg(-1) for IV DMD, 16.2 g kg(-1) for IVOMD, 14.8 g kg(-1) for neutral-detergent fibe r (NDF), and 14.3 g kg(-1) for ash-corrected NDF. Separate calibration s for each species x sample time combination resulted in little reduct ion in SECV. Sample numbers used in calibration could be reduced to ap proximate to 7% of total samples with SECV of 16.3 g kg(-1) for IVDMD. Masticate quality constituents of temperate species were satisfactori ly predicted by MRS when obtained from a wide range of seasonal and pl ant variation.