Fiber in Animal Nutrition

9 fiber methods according to Englyst et al. (1982) and Englyst and Cummings (1988) and the total dietary fiber method according to Prosky et al. (1984) were used. In human nutrition some further methods were prac- ticed (Spiller, 2001). All these methods inclu- ded a spectrumof several polysaccharides and further substances like ash, lignin and others. They are so called conventional or proximate methods, that means, reproducible results were only achieved by strictly following the analytical procedure. Analytical procedures were standardized, validated and published in analytical handbooks (AOAC, 2016; VD- LUFA, 2012; EC, 2009). Otherwise when the same samples are analysed by different laboratories this can lead to a surprisingly wide scatter of estimates. 1.2.1 Crude fiber The oldest definition andmethod is the crude fiber which was firstly discussed 200 years ago and which was included in the analytical characterization of feedstuffs by Henneberg and Strohmann (1859), a procedure which was called Weende analysis later on. Crude fiber is the loss on ignition of the dried residue remaining after digestion of a sample with 1.25% sulfuric acid and 1.125% sodium hydroxide solutions under specific conditions.The principle of themethod is that a finely ground air dried sample of the feed is extracted with ether to remove lipids and that this sample is then extracted successively with boiling acid and alkali. The residue is filtered off and washed. After drying and weighing, the residue is ashed and the residual 1.1 Introduction The definition of dietary fiber in the literature is variable. It is dependent on the nutritio- nal and physiological aspects and is closely related to the analytical methods. There are also different aspects between human and animal nutrition (De Vries and Rader, 2005; EFSA, 2010; Lunn and Buttriss, 2007; Spiller, 2001). A very common definition is that it is composed by polymeric carbohydrates from the plant cell wall including non carbohydrate compounds like lignin, which are not or only marginally digested in the small intestine. For human nutrition the US Food and Nu- trition Board defines “total dietary fiber” as the sum of “dietary fiber” consisting of non-digestible carbohydrates and lignin that are intrinsic in intact plants, and “functional fiber” consisting of isolated, non-digestible carbohydrate components with demonstrated beneficial physiological effects to humans (EFSA, 2010). An updating of the definition of dietary fiber may have impact on analytical issues. A further consequence may also be changes in the database of feed composition. 1.2 Analytical Methods Because of its heterogeneous nature, die- tary fiber is difficult to measure by direct instrumental means or by simple and direct methods, either chemical or gravimetric (De Vries and Rader, 2005). For animal nutrition analytical methods for fiber analysis were focused mainly on the crude fiber and the methods for neutral and acid detergent fiber according to van Soest et al. (1991). Especially for pet food also total Dietary Fiber and Analytics Hans Schenkel © ERLING Verlag