Effects of dietary soluble fibre level and protein source on growth, digestion, caecal activity and health of fattening rabbits

From weaning (34 d of age) until slaughter (76 d), 216 hybrid rabbits were divided into six experimental groups and fed ad libitum six iso-protein (CP: 15.9% as-fed), iso-starch (9.1%) and iso-ADF (21.4%) diets formulated in a bi-factorial arrangement, with three soluble fibre levels (LS: 5.8% vs. MS: 7.4% vs. HS: 8.5%) and two protein sources (Soy: soybean meal vs. Sun: sunflower meal). The increase in dietary soluble fibre level linearly increased (PL<0.001) in vivo digestibility of dry matter (from 55.4 to 61.3%), gross energy and fibre fractions (from 14.8 to 25.7% for acid detergent fibre; from 40.3 to 49.2% for insoluble hemicelluloses; from 85.0 to 93.9% for soluble fibre). Replacing soybean with sunflower meal tended to decrease crude protein digestibility (73.1 vs. 72.6%, P=0.058) and reduced acid detergent fi bre digestibility (22.0 vs. 18.4%, P<0.001), while improving ether extract digestibility (69.3 vs. 70.8, P<0.001). The nutritive values of the experimental diets increased with soluble fibre level (digestible energy from 9.0 to 9.9 MJ/kg) regardless of the protein source. Intestinal mucosa traits at 56 d of age were not affected, while caecal pH linearly decreased (from 6.19 to 5.97; PL=0.017) with increasing dietary soluble fibre. During the trial, health problems were moderate (mortality 3.4% and morbidity 15.6%) and not affected by feeding treatments. With increasing soluble fibre level, rabbit daily weight gain and final live weight linearly increased (PL=0.045) and feed conversion improved (from 3.55 to 3.30, PL<0.001). Protein source did not affect intestinal traits or growth performance. Slaughter results and meat quality were unaffected by feeding treatments.