Digestible fibre to ADF ratio and protein concentration in diets for early-weaned rabbits

To evaluate the effects of three ratios of digestible fibre (DF = hemicelluloses and pectins) to ADF (1.1, 1.3 and 1.5) and two levels of crude protein (CP, 16% and 17%) on digestive efficiency, growth performance, health status, and meat quality, from early-weaning (26 d of age) to slaughter (74 d) 246 rabbits were given ad libitum access to six diets according to a 3x2 factorial arrangement. Increasing DF/ADF linearly increased DM, fibre fraction and energy (59.9 vs. 62.3 vs. 65.9%, P<0.01) digestibility and daily weight gain (42.4 vs. 43.2 vs. 45.2 g/d; P=0.02) and improved feed conversion (P<0.01), without affecting slaughter results, carcass and meat quality. Total caecal VFA concentration increased (51.3 vs. 66.9 and 66.0 mmol/l; P<0.01) as DF/ADF raised from 1.1 to 1.3 and 1.5. Increasing dietary protein improved DM and nutrient digestibility and feed conversion (P<0.01), as well as slaughter dressing percentage (61.2 vs 61.8%, P=0.03). Dietary protein concentration did not modify caecal content characteristics or carcass and meat quality. A higher mortality (P=0.05) was measured in rabbits fed diets at 1.1 DF/ADF (27.1%) in comparison with rabbits fed diets at 1.3 (14.3%) and 1.5 (17.1%). However, feeding the highest DF/ADF diets, mortality raised up to 23.9% with the 16% CP diet, while was only 11.4% with the 17% CP diet.