NONSTARCH POLYSACCHARIDES AND BROILER PERFORMANCE ON DIETS CONTAINING SOYBEAN-MEAL AS THE SOLE PROTEIN-CONCENTRATE

The total water-soluble and water-insoluble non-starch polysaccharides (NSP) were determined in seven soyabean meals processed in Australia, three soyabean meals processed in the U.S.A., and one sunflower meal processed in Australia. Sunflower meal had a higher content of total NSP than any of the soyabean meals, due mainly to increased concentrations of cellulose and xylose in the insoluble NSP and uronic acids in the soluble NSP. Galactose and fucose concentrations were much greater in the insoluble NSP of soyabean meals. Soyabean meals processed in the U.S.A. had lower concentrations of total NSP, cellulose and xylose than equivalent meals processed in Australia. Broiler chickens fed diets containing soyabean meal as the sole dietary protein concentrate grew significantly more poorly than broilers fed isoenergetic and isonitrogenous diets in which approximately 25% of the soyabean meal was replaced with sunflower meal. There was a significant (P < 0.05) negative correlation (r2 = 0.57) between the water-soluble xylose content of the soyabean meals and the improvement in growth observed with sunflower meal supplementation. Multi-enzyme preparations designed to act on soyabean meal NSP substrates failed to induce any improvement in the growth of broilers fed soyabean meal diets. The poor performance of broilers fed the soyabean meal diets did not appear to be related to inadequate processing or to the NSP content or composition of the soyabean meals. Measurement of free sugars in the supernatant of the digesta in the ileum indicated that the stachyose derived from the oligosaccharides of soyabean meals appeared to exert an antinutritive effect when soyabean meal was present at high concentrations as the sole protein concentrate in broiler diets.