Effects of Processing Methods and Agronomic Variables on Carotene Contents in Forages and Predicting Carotene in Alfalfa Hay with Near-Infrared-Reflectance Spectroscopy

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Abstract
Six studies were to determine effects of drying method, stage of maturity, freezing and thawing, and 5 agronomic variables on carotene contents of forages and to evaluate near-IR reflectance spectroscopy for predicting carotene content in baled alfalfa hay. Microwave dried samples had the highest carotene among all drying methods tested. As drying time increased, carotene decreased. Storage in a refrigerator at 2.degree. C for 3-4 wk reduced carotene. The higher the initial carotene, the greater was the decrease. Thawing caused the most degradation of carotene, with the reduction continuing as thawing time was extended. Carotene contents were not changed if fresh samples were frozen or refrigerated for 24 h or held for 4 h at room temperature and light. Carotene was affected by species, light, N fertilization and interaction of light .times. N fertilization. Prediction equations by IR reflectance with correlations were developed for carotene. Correlations tended to increase if samples were from the same sources and preparation methods. The microwave-dried samples did not fit the equation when combined with samples from other methods. Calbration (78) and 29 unknown samples of field-cured, baled alfalfa hay from 4 intermountain states were collected. Splitting calibration data into low and high carotene gave satisfactory predictions for the unknowns.