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In Vitro Dry Matter Disappearance and Cell-Wall Concentrations of Flaccidgrass Masticates Predicted by Near Infrared Reflectance Spectroscopy

Escuela de Ciencias Agrarias, Universidad Nacional, Heredia, Costa Rica

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

USDA-ARS and Dep. of Crop Science

K. R. Pond

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

^* Corresponding author.

The degree of ingestive mastication of the diet selected from the pasture canopy by grazing ruminants and the quality of the resulting particles are related to animal performance. This study was conducted to determine if near infrared reflectance spectroscopy (NIP.S) could be used to predict quality of freeze-dried esophageal extrusa (including saliva) and extrusa particles separated by size. Masticates of flaccidgrass (Pennisetum flaccidum Griseb.) were obtained from a rotational grazing experiment in 1987 and 1988 at the start (initial) of grazing and after 3 d (final) of grazing. Masticates were freeze-dried and dry-sieved to give seven particle classes. Best NIPS prediction equations were obtained for the whole masticates (not sieved) and sieved classes when the total data set (whole masticate plus sieved classes) were separated into year and initial vs. final day of grazing. Standard errors of calibration (SEC) for predicting vitro dry matter disappearance (IVDMD), in vitro organic matter disappearance (IVOMD), and neutral-detergent fiber (NDF) ranged from 14.3 to 26.9 g kg^-1 for masticates at initial grazing and from 17.9 to 28.2 g kg^-1 on the final day of grazing. Standard errors of validation (SEV) slightly exceeded SEC ranging from 13.5 to 28.7 g kg^-1 for masticates at initial grazing and from 19.4 to 28.1 g kg^-1 for masticates on the final day of grazing. Whole masticate samples only, from both the initial and the final day of grazing, gave similar SEC (ranging from 17.6 to 21.0 g kg^-1) and SEV (ranging from 16.9 to 19.9 g kg^-1) as those obtained from the total data set. These SEV are acceptable for analytical purposes and show that NIPS can be used to predict IVDMD, IVOMD, and NDF of esophageal extrusa from flaccidgrass pastures.

Received for publication October 27, 1990.