Digestible fiber to ADF ratio and starch level in diets for growing rabbits

To evaluate the effect of digestible fibre (DF, hemicelluloses+pectins)/ADF ratio (1.0 and 1.3) and starch level (12, 15, and 18%) on health status, digestive physiology, growth performance, and carcass traits, 246 rabbits weaned at 27 d were fed until slaughter (76 d) with six diets formulated according to a bifactorial arrangement (2 DF/ADF ratios by 3 starch levels). Increasing DF/ADF improved DM digestibility (P<0.01), but did not affect growth performance, caecal content characteristics and slaughter traits. Increasing starch level improved digestibility efficiency and conversion index (P<0.001), decreased ileal mucosa villi height (P=0.04), without affecting growth performance, caecal fermentation and slaughter results. The increase of DF/ADF ratio tended to reduce mortality (25.0 vs 17.6%; P=0.11), whereas the raise of starch greatly increased mortality (from 6.9 to 43.1%; P<0.001) and sanitary risk (from 13.9 to 63.9%; P<0.001).