Effects of starch and protein sources, heat processing, and exogenous enzymes in starter diets for early weaned rabbits

Eight isonutritive diets were factorially arranged (2×2×2) to study the effect of substituting wheat and soyabean meal with peas, enzyme supplementation (0 vs 1 g/kg of an enzyme complex) and heat treatment of wheat and peas (raw vs processing) in diets of early weaned rabbits. Experimental diets were fed ad libitum in the starter period (25–39 days). Subsequently, a common feed was fed until 60 days of age. A feeding trial was conducted to measure effect of experimental diets on growth performance in 392 rabbits. A digestibility trial was carried out from 35 to 39 days of age in 64 animals. Ileal starch and crude protein (CP) concentrations were determined at 35 days of age with 144 rabbits (ileal samples were grouped in pairs resulting in nine replicates per diet). Wheat–soyabean meal diets showed higher coefficient of total tract apparent digestibility (CTTAD) of dry matter (DM), neutral detergent fibre (NDF), CP and starch than peas-based diets (by 1.9%, P=0.067; 13.5%, P=0.007; 3.0%, P=0.027; 0.3%, P=0.026, respectively). Enzyme addition improved CTTAD of DM, NDF and CP by 2.7%, P=0.008; 11.7%, P=0.013 and 2.4%, P=0.063 and heat processing by 2.3%, P=0.021; 13.7%, P=0.005 and 2.3%, P=0.087, respectively. Both heat processing and enzyme addition reduced ileal starch concentration from 54.6 to 41.2 g/kg DM (P<0.032). Wheat–soyabean meal showed lower ileal starch and CP concentration than peas-based diets: 36.0 vs 59.7 and 108 vs 118 g/kg DM, P<0.033, respectively. Pea-based diets showed lower average daily gain (ADG) and feed efficiency in the starter period than those based on wheat and soyabean meal (37.0 vs 38.5 g and 0.586 vs 0.571, P<0.021), but no differences were found at the 25–60-day period. Enzyme supplementation increased ADG by 3.1%, P=0.079 and feed efficiency by 3.7%, P=0.002 in the starter period and decreased mortality in the starter (from 7.8 vs 3.7%, P=0.083), and the whole fattening period (13.9 vs 6.9%, P=0.041). Heat processing led to a higher feed efficiency in the starter (0.588 vs 0.569, P=0.004) and over the whole fattening period (0.395 vs 0.387, P=0.017). The results indicate that (i) pea-based diets lower performance in the starter, but not over the whole fattening period than wheat–soyabean based diets and (ii) digestive capability of young rabbits is limited, so that enzyme supplementation and heat processing improve the performance of rabbits on starter diets.