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

Abstract

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 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(*2) scores and digestible N. Colour could potentially be used to quickly predict the nutritive value of CGF, particularly digestible N, a key parameter when formulating rations.