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Prediction of dry matter, crude protein degradability, and amino acid composition of corn silage and grass silage by near infrared reflectance spectroscopy (NIRS) Swift, Mary Lou

Abstract

This research program was designed to meet three objectives. The first was to ascertain the feasibility of using near infrared reflectance spectroscopy (NIRS) to predict ruminal degradability of dry matter (DM) and crude protein (CP) in corn silage (CS) and CP degradability in grass silage (GS) as determined by the in situ technique. The second objective was to develop calibration models to predict intestinal disappearance of DM and CP in CS and intestinal digestibility of CP in GS as determined by the mobile bag technique. The last objective was to investigate the feasibility of using NIRS to predict the essential amino acid (AA) composition of CS and GS. In situ data showed substantial variation in soluble and degradable DM and CP fractions as well as AA composition of CS. Based on the RPD statistic used to evaluate calibration equations, NIRS provides a viable option for the prediction of soluble DM and CP for CS, effectively degraded CS CP and CS CP disappearance from the intestinal and total digestive tract. It was not possible to produce robust calibration equations to predict rates of CS DM or CP degradability. Further study is required to ascertain the usefulness of NIRS in predicting AA composition of CS. Interpretation of spectral data showed that DM solubility and degradability of CS is linked to N-H bonding. There was a strong relationship between soluble DM, potentially degradable DM and effective degradability of CS CP. A review of the major wavelengths used in each calibration model indicated that fiber did not play a major role in CS DM digestibility. For the GS study, samples were classified according to increasing content of neutral detergent fiber (NDF) as this constituent is related to plant maturity. The content of soluble CP in GS significantly (P0.05) in potentially degradable CP. Likewise the rate of degradation of the potentially degradable CP fraction did not change according to NDF content. The amount of nominally undegradable CP from GS significantly (P

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