Carbohydrate composition, in vitro digestion, and effects of xylanase and phytase on nutrient and energy digestibility by pigs in grains and grain coproducts

coproducts;digestibility;fiber;in vitro;non-starch polysaccharides;phytase;pigs;xylanase

Jaworski, Neil ; Stein ; Hans H.

关键词: coproducts;    digestibility;    fiber;    in vitro;    non-starch polysaccharides;    phytase;    pigs;    xylanase;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/42214/Neil_Jaworski.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Four experiments were conducted to determine carbohydrate composition, in vitro digestion, and effects of xylanase and phytase on ileal and total tract digestibility of nutrients and energy in grains and grain coproducts. The objective of Exp. 1 and Exp. 2 was to determine the efficacy of xylanase and phytase supplementation to growing swine diets based on corn, soybean meal, distillers dried grains with solubles (DDGS), and wheat bran. In Exp. 1, the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of energy and nutrients in ileal cannulated growing pigs were determined. Four diets were formulated to meet the pig’s AA requirements using a low amount of crystalline AA, whereas 3 additional diets were formulated to contain greater amounts of crystalline AA. The 4 low-AA diets included the control diet that contained no phytase or xylanase, the phytase diet that contained 500 phytase units (FTU)/kg of phytase, and 2 diets that contained 500 FTU/kg of phytase and 2,000 or 4,000 xylanase units/kg. The 3 high-AA diets contained 500 FTU/kg of phytase and 2,000, 4,000, or 8,000 xylanase units/kg. Results indicated phytase added to the low-AA diets improved (P < 0.05) the AID of CP, Ca, P, and most AA by 2.2, 13.9, 9.4, and approximately 2%, respectively, compared with the control diet. Phytase also improved (P < 0.05) the ATTD of Ca and P by 18.1 and 13.8%, respectively, compared with the control diet. Xylanase added to the low-AA diets improved (P < 0.05) the AID of DM, GE, and NDF by 2.3, 1.9, and 5.8%, respectively, compared with the phytase diet. In Exp. 2, a 42-d growth assay was used to determine the growth performance of 288 pigs fed the same diets used in Exp. 1 with the exception that the diet with 8,000 units of xylanase was not used. No improvements in growth performance due to supplementation of phytase and xylanase to the diets were observed, indicating that the increases in digestibility of nutrients and energy by using xylanase and phytase in Exp. 1 were not large enough to improve growth performance. In Exp. 3, the carbohydrate composition of 12 U.S. swine feed ingredients was determined to classify the amount of available substrate for carbohydrase supplementation. The 12 ingredients included 3 grains (corn, sorghum, and wheat), 3 coproducts from the dry grind industry (corn DDGS and 2 sources of sorghum DDGS), 4 coproducts from the wet milling industry (corn gluten meal, corn gluten feed, corn germ meal, and corn bran), and 2 coproducts from the flour milling industry (wheat middlings and wheat bran). The parent grains (corn, sorghum, and wheat) contained greater amounts of starch and less non-starch polysaccharides (NSP) compared with the 9 coproducts, except corn gluten meal. The concentration of soluble NSP was minimal in all ingredients. Results indicated that there are substantial amounts of NSP in these ingredients, which indicates that NSP-degrading enzymes such as xylanase may be effective in improving the nutritional value of these ingredients. Exp. 4 was conducted to determine in vitro ileal and total tract digestibility of DM and NSP in the 12 feed ingredients used in Exp. 3. In vitro ileal digestibility of NSP was close to zero in all feed ingredients, indicating that pepsin and pancreatin enzymes have no effect on degradation of NSP. However, a strong correlation (R2 = 0.97) between in vitro ileal digestibility of DM and NSP concentration in the feed ingredients was observed, which indicates that in vitro ileal digestibility of DM may be used to estimate NSP concentration in feed ingredients. In vitro total tract digestibility of NSP ranged from 6.5% in corn bran to 55.0% in corn germ meal, which indicates that NSP composition in each ingredient plays an important role in determining the extent of NSP fermentation, as well as exogenous enzyme degradation. As a consequence, the amount of enzyme supplementation and energy value of each ingredient is influenced by the composition of the NSP fraction.