title: Colour score as a guide for estimating the protein value of corn gluten feed.
abstract: 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(*2) scores and digestible N.
  
  
  CONCLUSIONS
  Colour could potentially be used to quickly predict the nutritive value of CGF, particularly digestible N, a key parameter when formulating rations.
authors: REQUIMTE, Departamento de Geociências, Ambiente e Ordenamento do Território, Faculdade de Ciências, Universidade do Porto, 4485-661 Vairão VC, Portugal. rita.cabrita@mail.icav.up.pt
authors: Ana Rita J
authors: AR
authors: Cabrita
authors: Margarida R G
authors: MR
authors: Maia
authors: Marisa
authors: M
authors: Freitas
authors: José Manuel F
authors: JM
authors: Abreu
authors: António J Mira
authors: AJ
authors: Fonseca
mesh_terms: D000821:Animal Feed; D000818:Animals; D003116:Color; D004043:Dietary Fiber / Q000032:analysis*; D004044:Dietary Proteins / Q000032:analysis*; D005983:Glutens / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis; D009753:Nutritive Value; D010940:Plant Proteins / Q000032:analysis*; D025341:Principal Component Analysis; D012044:Regression Analysis; D003313:Zea mays / Q000737:chemistry*
chemical_list: D004043:Dietary Fiber; D004044:Dietary Proteins; D010940:Plant Proteins; D005983:Glutens; D009584:Nitrogen