INCLUSION OF GRAPE POMACE, IN SUBSTITUTION FOR ALFALFA HAY, IN DIETS FOR GROWING RABBITS

Four diets were formulated to study the effect of a progressive substi tution of grape pomace (GP) for alfalfa hay (AH) at the rates 0, 100, 200 and 300 g/kg total weight. The control diet contained 500 g AH and 192 g acid-detergent fibre per kg dry matter (DM). In experiment 1, 3 2 Californian X New Zealand White rabbits were used to determine dieta ry nutrient apparent digestibility. The inclusion of GP decreased the apparent digestibility of crude protein (P < 0.001) and energy (P < 0. 05). However, the digestible energy (DE) contents of the diets were si milar because GP had a greater gross energy content than AH. In experi ment 2, 3 rabbits given the same diets as in experiment 1 were used to determine several digestive and productive traits and chemical body c omposition (at 2.0 kg live weight). Dietary inclusion of GP linearly d ecreased ammonia (P < 0.01), total volatile fatty acid concentration ( P < 0.001) and the molar proportion of acetate (P < 0.05) in the caecu m. Starch content in the ileal and caecal contents was low but linearl y increased (P < 0.05) with increasing dietary concentration of GP. Th e average daily gain (from weaning at 30 days of age to 2.0 kg live we ight) was not significantly affected (P > 0.10) by the diet, but the r atio gain: food linearly decreased (P < 0.001) with the GP inclusion. Dietary inclusion of GP linearly increased (P < 0.10) the fat content of the empty body of the rabbits. The efficiency of utilization of die tary DE and protein for growth were calculated by the comparative slau ghter method, using the chemical body composition data of 22 suckling rabbits slaughtered at 30 days of age for the initial body composition . The efficiency of utilization of DE was not influenced by dietary GP inclusion, but GP linearly increased (P < 0.01) digestible crude prot ein utilization. The decrease in crude protein apparent digestibility may be the main reason that gran: food ratio was impaired in diets con taining GP substituted for AH.