Dietary Fibres: Their Analysis in Animal Feeding, and Their Role in Rabbit Nutrition and Health

Two centuries ago Heinrich Einhof develops the so-called Weende method (crude fibre), to first deals with the fibre content of the feeds for ruminants, and proposes to isolate a residue called the "crude fibre". Then, dietary fibres concepts evolve and differ in animal feeding compared to human nutrition and health. Animal nutritionists deals with various fibres sources, often from whole plants (forages, by products of seeds processing, etc.), and recovers a larger range of polysaccharidic components, including other polymers, such polyphenolic (lignins, tannins) or polylipidic compounds (cutins). Dietary fibres are generally defined as the polysaccharides and associated substances resistant to mammal enzyme digestion and absorption that can be partially or totally fermented in the gut. However, today this topic is still subjected to very active research, because of the complexity of the physical structure and chemical composition of the plant cell walls, and in the wide and different physiological effects of these different constituents. The importance of dietary fibres in animal feeding is due to its influence on rate of passage, mucosa functionality and its role as substrate for gut microbiota that relates to performances and digestive health. Our review will consider briefly the definition and structure of the different classes of fibres and of cell wall constituents, followed by a description of some analytical methods employed for animal feeds. Secondly the nutritional role and impact of fibres intake on digestive health will be described for the growing rabbit. The fibres in the rabbit feed are essential to reduce the risk of digestive trouble after weaning, and the requirements are defined in term of quantity and quality of the fibres fractions: a minimal level of lignocellulose "ADF" (18%) and lignins (>5%), balanced with a maximum quantity of digestible fibres "DgF" (ratio DgF/ADF below 1.3).