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Near Infrared Reflectance Spectroscopy Prediction of Quality from Masticated Temperate Forage Species

AgResearch Grasslands, Private Bag 11008, Palmerston North, New Zealand

J. C. Burns^* and D. S. Fisher

USDA-ARS and Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695

J. P. Muller and K. R. Pond

Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695
Dep. of Animal Science, North Carolina State Univ., Raleigh, NC 27695

^* Corresponding author.

Masticated forage provides information related to the quality and fractionation characteristics of a ruminant's diet. This study reports the use of near infrared reflectance spectroscopy (NIRS) to predict the in vitro dry matter disappearance (IVDMD), in vitro organic matter disappearance (IVOMD), and ceil-wall concentrations of particle size fractions and the whole masticate of temperate forages. Esophageal extrusa samples, with saliva retained, were obtained from fistulated steers (Bos taurus) that were intermittently grazing tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), and ryegrass (Lolium 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-ram residue. Masticates, quickfrozen in liquid N2, were subsequently lyophilized and dry sieved into seven particle size fractions and, along with a whole-masticate subsample, were scanned for NIRS analyses. A single broad-based calibration encompassing all experimental factors predicted quality constituents within acceptable limits of precision for this methodology. Standard errors of cross-validation (SECV) were 6 g kg^–1 for organic matter, 16.0 g kg^–1 for IVDMD, 16.2 g kg^–1 for IVOMD, 14.8 g kg^–1 for neutral-detergent fiber (NDF), and 14.3 g kg^–1 for ash corrected NDF. Separate calibrations for each species x sample time combination resulted in little reduction in SECV. Sample numbers used in calibration could be reduced to = 7% of total samples with SECV of 16.3 g kg,^–1 for IVDMD. Masticate quality constituents of temperate species were satisfactorily predicted by NIRS when obtained from a wide range of seasonal and plant variation.

Received for publication February 4, 1993.