Colour score as a guide for estimating the protein value of corn gluten feed

BACKGROUND: Dry corn gluten feed (CGF) is a raw material commonly included in compound feeds, particularly for ruminant animals. Its colour can vary from yellow–light brown to dark brown. A general assumption is that darker CGF has a low nutritive value for animals due to heat‐damaged protein. This study aims to evaluate the use of colour as a practical guide for estimating CGF protein value. RESULTS: Results indicate great variability in the physical and nutritional properties among 28 sources of CGF. Principal component factor analysis was used to reduce a large number of variables into fewer numbers of factors. First factor aggregated 1/ Z and acid detergent insoluble N content in opposition to X , Y , e L , and L   *   2. Second factor aggregated a , a *, neutral detergent fibre and soluble crude protein (CP) contents in opposition to ash and CP contents, and digestible N and in vitro organic matter digestibility. Multiple regression analysis also showed that physical appearance (colour) was related to nutritional properties, stronger relationships being found between a , a * and L   *   2scores and digestible N. CONCLUSION: Colour could potentially be used to quickly predict the nutritive value of CGF, particularly digestible N, a key parameter when formulating rations. Copyright © 2011 Society of Chemical Industry