Carbohydrates in alfalfa-timothy mixtures predicted with near infrared reflectance spectroscopy equations developed for single species

Abstract

Our objective was to evaluate the feasibility of using near infrared reflectance spectroscopy (NIRS) equations previously developed with a calibration set that included samples of both timothy and alfalfa to predict carbohydrate fractions in mixed samples of both species. Timothy and alfalfa mixed samples were prepared with the alfalfa proportion ranging from 0 to 100%, with increments of 4%. With previously developed NIRS equations based on samples of single species of timothy and alfalfa, concentrations of total ethanol soluble carbohydrates (TESC), starch, and neutral detergent soluble carbohydrates (NDSC) of the mixed samples were predicted successfully, but concentrations of organic acids (OA) and neutral detergent soluble fiber (NDSF) were unsuccessfully predicted. Adding 13 mixed samples to the initial calibration set of around 110 samples of pure timothy and alfalfa samples improved the accuracy of already successful predictions for TESC, starch, and NDSC, and resulted in a successful prediction for NDSF in timothy and alfalfa mixtures.Key words: Near infrared reflectance spectroscopy, sugars, Phleum pratense, Medicago sativa