Fiber in Animal Nutrition

61 5.1 Introduction Many petfood formulas contain powdered cellulose, but the cellulose fibers may differ in length, diameter, chemical composition andwater-binding capacity. Preparations may consist of lignocellulose or purified cellulose. Fibrillated cellulose that forms an insoluble fiber network can be produced by modern and sophisticated milling technology. Cellulose fiber can be added to petfood as nutrient and/or functional ingredient. As nutrient, cellulose may support healthy gut mobility and function. As functional ingredient, cellulose at higher inclusion levels provides specific health benefits be- yond basic nutrition. Technological func- tionality of cellulose lies in improving the food’s texture. A relatively low dietary level of cellulose meets the fiber intake that accommodates optimum feces quality, which might relate to comforting gut mobility. Higher cellulose levels are found in low-calorie products such as light and weight-reduction foods. Likewise, petfoods intended for hairball, dental and diabetes control are enriched with cellulose. For petfood labeling, the analysis of crude fiber is used as quantitative measure. The analytical method yields variable proportions of dietary cellulose, hemicelluloses and lignin, whereas it may exclude other fibers.The crude fiber content of many cellulose preparations is around 70%. Regular dry dog and cat foods contain between 1.5 and 4% crude fiber, whereas wet foods have concentrations of 0.3 to 1%. The crude fiber content of veterinary, weight-reduction diets for dogs in dry form can be as high as 20%. 5.2 Cellulose 5.2.1 Cellulose as nutrient In truncated form, the National Research Council (2006) states that although dietary fiber is not a required nutrient, it is directly involved in maintaining gut health of dogs and cats. This view is substantiated by the observations that the diarrhea caused by fiber-free diets is nullified by supplemental cellulose. The basis of this beneficial cellu- lose effect is unknown, but it could relate to normalizing gut motility, enhanced water absorption by the hind gut, water binding by cellulose in feces or a combination. Anyhow, adding cellulose to a fiber-free diet elevates the dry matter content of feces. Dogs fed f iber-free diets consisting of partially purified proteins, hydrogenated vegetable fat, minerals, vitamins and sucrose had diarrhea, making fecal col lections difficult (Mabee and Morgan, 1950). It was helpful to feed cellulose two or three days preceding as well as during the collections. In another dog study, a fiber-free semipurified diet containing 40 % a lbumin caused severe diarrhea which was overcome by incorporating of 10% cellulose and 10% agar into the diet (Morgan et al., 1951). Wichert et al. (2002) fed dogs on an es- sentially fiber-free, wet diet consisting of cooked greaves, cooked starch, sunflower oil and a mineral-vitamin supplement. On the fiber-free diet, the dogs’ feces had a liquid/ pasty appearance. The feces became solid/ Fiber in Dog and Cat Nutrition Anton C. Beynen © ERLING Verlag