Effect of enzyme addition on the digestibilities of cell wall polysaccharides and oligosaccharides from whole, dehulled, and ethanol-extracted white lupins in chickens

Instituto del Frio, Departamento Metabolismo y Nutricion, Jose Antonio Novais, 10, 28040 Madrid, Spain. abrenes@if.csic.es

Three experiments were conducted to examine the effects of a commercial enzyme preparation on chicks performance and digestibilities of nonstarch polysaccharides (NSP), raffinose (R), stachyose (S), and total oligosaccharides (O) in diets containing whole and dehulled lupin and ethanol-extracted dehulled lupin meal. Ethanol extract was also used to produce a rich oligosaccharide fraction. In the first experiment, the dehulling treatment and the addition of enzyme to the diet improved (P < 0.05) weight gain (24 and 15%), feed-to-gain ratio (13 and 9%), dry matter retention (32 and 8%), apparent protein digestibility (6 and 3%) and ileal digestibilities of raffinose (19 and 119%), stachyose (85 and 204%), and total oligosaccharides (68 and 178%), respectively. In addition, enzyme treatment improved (P < 0.05) excreta digestibility values for NSP (from -1.7 to 5.5%), R (from 64.6 to 92.6%), S (from 48.8 to 82.4%), and O (from 55.8 to 83.5%). In the second experiment, extraction of the ethanol soluble components from dehulled lupin decreased (P < 0.0001) weight gain (51%), and increased (P < 0.0001) feed consumption (34%), feed-to-gain ratio (32%), relative gizzard weight (14%), and the relative ceca length (20%). The addition of the isolated fraction of oligosacharides to the corn-extracted lupin diet (7.5 and 15%) yielded performance values similar to those obtained with the unextracted dehulled lupin. The addition of enzymes to the diets significantly improved the weight gain (11%) and feed to gain ratio (6%), and decreased relative gizzard weight (12%) and relative ceca length (7%). Ileal digestibilities of R, S, and O were considerably lower than corresponding excreta digestibilities. The excreta digestibility of NSP and excreta and ileal digestibilities of R, S, and O were lower (P < 0.05) in chicks fed the lupin diet containing the high concentration of extract compared with those fed the same diet containing the lower concentration of extract. Enzymes, when added to the diets, increased (P < 0.05) the digestibilities of R, S, and O with the relative effects being much greater for ileal than excreta samples. In the third experiment, the ethanol extract (7.5 and 15%) added to a corn-soybean diet improved weight gain, feed consumption, and feed-to-gain ratio by 19, 13, and 6%, respectively. Ileal digestibilities of R, S, and O were low (< 45%), especially in chicks fed the diets containing the high amount of added oligosaccharide fraction. There was no effect of enzyme addition on the performance parameters. However, supplemental dietary enzymes improved (P < 0.05) ileal and excreta digestibilities of oligosaccharides from 15.6 and 68.6% to 52.3 and 84.8%, respectively. In summary, dehulling greatly improved the nutritional value of lupin, while removal of the ethanol soluble materials, including raffinose and stachyose considerably decreased its value. The oligosaccharide fraction does not seem to have an antinutritive effect and the addition of enzymes increased the digestibilities of NSP, raffinose, and stachyose but did not significantly improve chick performance.

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