Very low protein, amino acid-supplied diet for heavy broiler rabbits: effects on nitrogen metabolism, and digital evaluation of excreta and products.

A very low protein diet (A, 15.9% DM) for the fattening of heavy broiler rabbits was supplied by the four available synthetic amino acid and compared to a control feed (C, 19.7% DM) in a study carried in metabolism cages with 12 (6+6) rabbits controlled at 81-84 days, then slaughtered at 87 days. The diets were anisoproteic, but isoenergetic and isofibrous. The low protein supply produced strong reduction in Blood Urea (-32%) and in Urea Urine (-37%) thus in the N-urinary emission (-29%; P<0.12). In the gastro-intestinal trait, however, N-feed was on average less utilized by the A group and refused (N faeces +20%; P<0.2). This findings appear to be biased because an exceptionally late growth in the Control group (50 vs. 40 g/d) provided by a push in glucose, unreal with respect to the growth trial (30.1 vs. 36.8 g/d) corroborated by favorable environmental conditions, resulting in a 29% higher N-retention for C a value clearly and strongly overestimated. Digital evaluation of fresh urine and faeces were able to discriminate the groups, while less or nothing the live, or the carcass or meat.