Effets de l'extrusion du blé ou de l'orge sans ou avec l'addition des carbohydrases, sur les performances, digestibilité des nutriments, bien-être et qualité de la viande chez le poulet de chair

The aim of this study was to evaluate the effect of wheat and barley extrusion, in combination or not with carbohydrases, on the performance, apparent ileal digestibly (AID) of nutrients, welfare and some meat quality parameters of broiler chickens from 0 to 39 days. A total of 1920 one-day old male broiler chickens were allocated in 48 pens at 40 chickens per pen (10 chickens per m2). The experimental design was a complete randomized block design with a factorial arrangement of treatments 2 x 2 x 2 (2 cereals: wheat-barley; 2 process: raw-extruded; addition or not of enzymes carbohydrases; xylanase for wheat diets and Beta-glucanase for barley diets), with 6 replicates of 40 birds for a total of 240 birds per treatment. Cereals were extruded at 105-135 degrees C with 13-15 per cent water addition. Cereals were included into the experimental diets at 63-69 per cent (wheat) and 55-62 per cent (barley), and then feeds were pelleted. Performance from 0-14, 14-29 and 29-37 days; water per feed intake ratio from 29-32 days; the AID of energy, protein and amino acids; and the intestinal viscosity at 21 days were measured. The sticky droppings; the litter quality; the feather cleanness; the incidence of pododermatitis and tibiotarsal dermatitis and some welfare indicators were measured. At the end of the trial, carcass yield and some meat quality parameters were also determined (pH 15 minutes and 24 hours post-mortem, cooking loss and tenderness). Several interactions between cereal extrusion, cereal enzyme, extrusion enzyme and cereal extrusion enzyme were found for several variables. Wheat and barley extrusion increased the intestinal viscosity, and the increase was greater with barley than wheat (cereal extrusion, P smaller than 0.001). Extrusion increased also water per feed intake ratio (P smaller than 0.05). Wheat extrusion increased AID of energy (P smaller than 0.05) and it had no effect on protein and amino acids digestibility, expect for the glutamic acid which was reduced (P smaller than 0.05). Barley extrusion reduced the AID of energy, protein and amino acids (P smaller than 0.05). Wheat extrusion had no significant effect on performance of chickens, while barley extrusion impaired feed conversion ratio (P smaller than 0.05). Xylanase supplementation to the extruded wheat diet increased the AID of energy and amino acids (P smaller than 0.05), except for arginine, lysine, methionine, threonine, alanine and tyrosine. Beta-glucanase supplementation to the extruded barley diet increased the AID of energy and amino acids (P smaller than 0.05), except for histidine, arginine, aspartic acid and cysteine, and also the protein AID. Xylanase supplementation to extruded wheat diet greatly reduced the feed consumption (11.7 g per day) and weight gain (5.7 g per day) (P smaller than 0.05) from 0-37 days. Xylanase supplementation also reduced feed intake and weight gain in birds receiving the raw wheat based diet (8.2 g per day and 4.4 g per day for feed intake and weight gain, respectively) (P smaller than 0.05). Barley extrusion impaired litter quality and feather cleanness (P smaller than 0.05) and increased the incidence and the severity of pododermatitis (P smaller than 0.05), and Beta-glucanase supplementation improved them (P smaller than 0.05). Enzyme reduced the percentage of birds showing severe pododermatitis (score 4) (P smaller than 0.05). Beta-glucanase supplementation to barley diets increased carcass yield (P smaller than 0.05) and the increase was higher with extruded barley than raw barley. Wheat extrusion and Beta-glucanase supplementation to the barley extruded diet decreased the pH 15 min post-mortem of Pectoralis major muscle, and barley extrusion reduced the ultimate pH (P smaller than 0.05). Barley extrusion or enzyme addition, but not the combination, increased cooked meat tenderness. Under the conditions of the present experiment, wheat or barley extrusion did not allow to improve performance of broiler chickens. The combination of extrusion and enzyme addition did not bring any additional improvement, despite the positive impact on nutrient digestibility, intestinal viscosity, litter quality and pododermatitis reduction observed