Fiber in Animal Nutrition

Fiber in Rabbit Nutrition 54 “DF”, correspondingmainly to hemicelluloses (HC) and insoluble pectins (WIP). HC are a group of several polysaccharides, estimated by difference between NDF & ADF (see table 25). Quantitatively HC constitute 10–25% of the DM in forages and agro-industrial by-products (brans, oilseeds and legume seeds, hulls and pulps) and about 2–12% DM of grains and roots. The WIP are in dicotyledonous plants, such as in legume seeds (4–14%DMin soybean, pea, faba bean, white lupin), and also in fruits and pulps. Finally, water-soluble polysaccharides and oligosaccharides are usually in low level in ingredients for animal feeding. For instance, soluble hemicelluloses such as arabinoxylans (in wheat, oat and barley) range between 2–4% DM, and β -glucans range between 1–3%DM in barley or oat. Oligosaccharides such as α -galactosides are found in lupin, pea or soya seeds (5–8%DM). But the most important fraction of SF is soluble pectic substances, that could reach from 10 to 40% DM, in pulps of fruits or beets. 4.4 Impact of fibers on digestion and performances The importance of fibers is due to effects on intake, rate of passage and role as substrate for caecal microbiota (Combes et al., 2013). But, for the growing rabbit one of the main challenges is to provide fiber recommenda- tions for digestive trouble prevention and without a too large impairment of perfor- mance (growth, feed efficiency). 4.4.1 Dietary fibers level and intake regulation of the growing rabbit. The domestic rabbit fed a pelleted balanced diet is able to regulate its feed intake to reach a constant DE (digestible energy) intake when the dietary DE concentration ranges between 9.0 and 11.5 MJ/kg (figure 11). But a higher correlation is obtained with the Acid Detergent Fiber (ADF) level when between 10 and 25% in a diet. The voluntary feed intake is more related to the dietary ADF level because of the low digestion of this fraction, and probably because the ADF level Figure 11: Feed intake of the growing rabbit, according to the ADF or the digestible energy content of the diet DFI: daily feed intake measured between weaning (4 weeks) and 11 weeks old 140 120 100 80 60 140 120 100 80 60 1700 2200 2700 3200 DFI g/d DFI g/d Intake and dietary digestible energy level (DE) Intake and dietary lignocellulose level (ADF) y = -0.029x + 186.6 R 2 = 0.65 y = -0.079x2 + 5.05x + 49.0 R 2 = 0.92 DE (kcal/kg as fed) ADF level in diet (g/100g) 5 10 15 20 25 30 © ERLING Verlag