The Use of Near Infrared Analysis for In Situ Studies

¹ Department of Animal Science, University of Padova, Agripolis, 35020 Legnaro, Italy

This study evaluated the use of near infrared reflectance spectroscopy to estimate the chemical composition of feed residues after in situ ruminal incubation. Residues of three alfalfa hays (n = 93) and three alfalfa pellets (n = 93) obtained after ruminal exposure were analyzed for dry matter, crude protein, neutral detergent fiber, acid detergent fiber, and acid detergent lignin by wet chemistry and were also scanned with a near infrared monochromator instrument. A calibration was calculated that combined hay and pellet samples (n = 60). Validation tests were performed using the remaining feed residues. The coefficients of determination and standard errors (percentage of dry matter) of the validation tests for crude protein, neutral detergent fiber, acid detergent fiber, and lignin were of 0.95 and 0.92, 0.96 and 1.68, 0.95 and 1.56, and 0.99 and 0.48, respectively. Similar statistics were obtained using the SELECT algorithm of sample selection; a further 30% reduction was observed in the number of samples that were used for calibration. Kinetics of ruminal degradation and effective degradabilities that were calculated based on chemical composition of the residues as determined by wet chemistry or estimated by near infrared reflectance spectroscopy were not significantly different for 68 out of 71 means. Differences in ruminal kinetics caused by the different forages were also unaffected by method of residue analyses. Near infrared reflectance spectroscopy allowed a reduction in the number of necessary laboratory analyses of feed residues without affecting the results of in situ studies.

Key Words: near infrared • in situ degradation • alfalfa

Submitted on January 2, 1997
Accepted on June 5, 1997