The effects of sepiolite in broiler chicken diets of high, medium and low viscosity. Productive performance and nutritive value

Productive and digestive parameters (feed:gain conversion rates, whole-tract digestibility, intestinal viscosity and kinetics of digesta flow) were determined in broiler chickens fed on three diets of different viscosities, maize (low viscous), wheat–barley (medium viscous) and maize–10 g/kg carboxymethyl cellulose (maize–CMC, high viscous) based. The three diets were supplemented with 0, 10 and 20 g/kg of sepiolite (EXAL® UE-562), respectively, to examine how soluble non-starch polysaccharides per se influence nutrient digestion, and the extent to which sepiolite supplementation (10 or 20 g/kg) could improve dietary OM digestibility and AME content. Broiler chickens fed on maize and barley-wheat showed higher (p<0.001) live weights (664 and 672 g, respectively) at 22 days of age than those fed on maize-CMC (597 g). Significant differences were also observed in the voluntary intake and feed:gain conversion rates. No significant differences were observed in the productive performance of the animals associated with the sepiolite supplementation. Sepiolite increased significantly the organic matter digestibility, in line with decreases in the water-relative viscosity determined in the jejunum, and changes in the kinetics of digesta flow. Sepiolite decreased mean retention time in the whole gastrointestinal tract and small intestine with medium and high viscous diets (barley–wheat, maize–CMC) and prolonged these times with the low viscous diet. No significant relationships were observed between the changes in the retention time of the digesta and the digestibility values estimated after sepiolite supplementation. A likely contribution of other digestive mechanisms, such as changes in the digesta viscosity or microbial activity could be involved.