Effects of dietary protein levels and multienzyme supplementation on growth performance and markers of gut health of broilers fed a miscellaneous meal based diet

The current study investigated the effects of dietary protein levels and multienzyme supplementation on the growth performance, subclinical necrotic enteritis, intestinal mucosal barrier and microflora of broilers fed diets containing meals of cottonseeds, rapeseeds, peanuts and sesame. A total of 480 one-day-old male Cobb broilers were assigned to a 2 × 2 factorial arrangement of treatments with 6 replicated pens of 20 birds each. Experimental factors included two dietary protein levels at 205 or 225 g/kg, and without or with multienzymes. The multienzymes contained phytase, protease and xylanase at 1000, 2000 and 2000 U/kg of feed, respectively. The trial lasted for 21 days. The high protein diet increased (P < 0.05) small intestinal lesions, duodenal mucin 2 secretion, ileal counts of C. perfringens and E. coli, but decreased (P < 0.05) secretary IgA (sIgA), polymeric Ig receptor (pIgR), ileal counts of Lactobacilli and Bifidobacteria. Multienzymes increased (P < 0.05) feed intake, body weight gain, pIgR, sIgA, and ileal counts of Lactobacilli and Bifidobacteria and decreased (P < 0.05) intestinal lesions, serum a-toxin antibodies, mucin 2 expression and ileal count of C. perfringens, but the magnitude of the effect of multienzymes was dependent on the protein level in the diet (interaction, P < 0.05). It can be concluded that diets containing high nonconventional protein can increase the incidence of subclinical necrotic enteritis, while supplementing multienzymes can decline this risk in broilers.