THE DIGESTIBILITY OF CELL-WALL POLYSACCHARIDES FROM WHEAT (BRAN OR WHOLE GRAIN), SOYBEAN-MEAL, AND WHITE LUPIN MEAL IN COCKERELS, MUSCOVY DUCKS, AND RATS

The digestibility of nonstarch polysaccharides (NSP) were measured in cockerels. Muscovy ducks, and rats by using four diets where the only sources of NSP were wheat bran (Diet B), whole wheat grain (Diet W), soybean meal (Diet S), or white lupin meal (Diet L). The four diets contained similar amounts of crude protein (24.4%), lipids (5.2%), and NSP (6.9%). The proportions of water-soluble NSP in total NSP were 11.1% (Diet B), 19.7% (Diet W), 8% (Diet S), and 11.5% (Diet L). The NSP contents of feed and excreta were determined by measuring their individual sugars, using gas-liquid chromatography of alditol acetate derivatives. The digestibility values of NSP ranged from 21.9% (Diet W) to 13% (Diet L) for cockerels, from 18.7% (Diet W) to 7.9% (Diet L) for ducks, and from 85.7% (Diet L) to 44.1% (Diet B) for rats. These results suggest that cockerels and ducks were only able to digest the water-soluble fraction of the nonstarch polysaccharides. The pectic polymers, which were major components in water-insoluble NSP of Diets S and L, were digested to a high extent by the rats. The digestible-energy (DE) values, calculated for the birds from the apparent metabolizable-energy values corrected for nitrogen retention (AMEn), were very similar when cockerels and ducks were compared; the differences between bird species did not exceed .23 MJ per kg of dry matter. In all cases, the DE values were higher for rats than for birds. These results suggested that the main factor responsible for the differences in DE values between rats and birds was the ability to digest NSP, which was higher for the rats than for the birds.