Effect of increasing lignin in isoenergetic diets at two soluble fibre levels on digestion, performance and carcass quality of growing rabbits

Abstract To assess the effect of increasing dietary lignin in isoenergetic diets at two soluble fibre (SF) levels on digestion, performance and carcass quality of growing rabbits, four diets were formulated according a 2 × 2 factorial design: low SF-low lignin (LSF/LL), low SF-high lignin (LSF/HL), high SF-low lignin (HSF/LL) and high SF-high lignin (HSF/HL). On average, in HSF diets SF was increased by 49 g/kg DM, mainly replacing starch (−53 g/kg DM), and in HL diets lignin was increased by 40 g/kg, mainly reducing starch (-78 g/kg DM), with increasing EE (+31 g/kg DM). Two hundred and sixty crossbred weaned rabbits (35 days old) were assigned to the experimental diets, individually housed and fed ad libitum until 63 days of age. Digestibility (from 49 to 53 days old), growth performance (from 35 to 63 days old), carcass quality (at 63 days old) and caecal environment (at 63 days old) were studied in 12, 65, 45 and 16 rabbits per diet, respectively. High SF diets showed higher CTTAD of fibrous fractions (+0.206±0.011, +0.207±0.015, +0.214±0.011 and +0.167±0.015 for aNDFom, ADFom, hemicelluloses and cellulose, respectively, P