The objectives of this study were to investigate the effects of extrusion on the chemical compositions, surface structure, and molecular structure of brewer’s spent grain (BSG), as well as to determine the digestible energy (DE), metabolizable energy (ME), apparent total tract digestibility (ATTD) of nutrients and energy, and amino acid (AA) digestibility of extruded BSG when fed to growing pigs. Firstly, we determined the changes in chemical compositions and molecular structure of both non-extruded and extruded BSG. In Exp. 1, eighteen growing pigs were fed three different diets including one corn-soybean meal basal diet and two experimental diets containing 20% BSG with or without extrusion. Feces and urine were collected to determine the ATTD of nutrients and energy, DE, and ME of extruded or non-extruded BSG. In Exp. 2, eighteen growing pigs were fed three different diets including 30% BSG with or without extrusion, and an N-free diet. Ileal digesta was collected through the slaughter method to determine the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA of extruded or non-extruded BSG. The results showed that extrusion reduced the neutral detergent fiber, hemicellulose and cellulose contents in BSG, and increased the Arg, Asp, Glu, Ser, Tyr, total indispensable AA and total AA contents of BSG, altered the surface structure of BSG, increased the peak absorbance in amide I and amide II height, amide II and amide (I+II) area, α-helix height, decreased β-sheet height, and weakened band intensities in cellulosic compounds (CELC) area, structural carbohydrates (SCHO) area, carbohydrates area (CHO) peak 2 and 3 height, the area ratio of CELC: CHO and CELC: SCHO. Moreover, DE and ME values and ATTD of energy, dry matter, crude protein, acid detergent fiber, neutral detergent fiber, cellulose and hemicellulose increased (P < 0.05) when pigs were fed extruded BSG diets. The AID and SID of Arg, His, Lys, Val and Gly increased, whereas the AID and SID of Ile and Leu decreased when pigs were fed extrusion diets (P < 0.05). Our study found that the ATTD of nutrients and AA digestibility in pigs were positively correlated with the molecular structure of proteins, and negatively correlated with the molecular structure of carbohydrates (P < 0.05). These findings suggested that extrusion had the potential to improve the nutrient digestibility of BSG by altering its chemical compositions, surface structure, and molecular structure.

中文翻译：

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挤压可以改善啤酒渣的分子结构对生长猪能量含量和氨基酸消化率的负面影响


本研究的目的是研究挤压对啤酒渣 （BSG） 化学成分、表面结构和分子结构的影响，以及确定挤压 BSG 的消化能 （DE）、代谢能 （ME）、营养物质和能量的表观总消化率 （ATTD） 和氨基酸 （AA） 消化率喂养生长猪时。首先，我们确定了非挤出和挤出 BSG 的化学成分和分子结构的变化。在实验 1 中，18 头生长猪饲喂了三种不同的日粮，包括一种玉米豆粕基础日粮和两种含有 20% BSG 的实验日粮，有或没有挤压。收集粪便和尿液以确定挤压或非挤压 BSG 的营养物质和能量的 ATTD、DE 和 ME。在实验 2 中，18 头生长猪饲喂了三种不同的日粮，包括 30% BSG（含或不不含挤压）和不含 N 的日粮。通过屠宰法收集回肠消化物，以确定挤压或非挤压 BSG 的 AA 的表观回肠消化率 （AID） 和标准化回肠消化率 （SID）。结果表明，挤压降低了BSG中性洗涤纤维、半纤维素和纤维素含量，增加了BSG的Arg、Asp、Glu、Ser、Tyr、总不可缺少AA和总AA含量，改变了BSG的表面结构，增加了酰胺I和酰胺II高度、酰胺II和酰胺（I+II）面积的峰吸光度， 纤维素化合物 （CELC） 面积、结构碳水化合物 （SCHO） 面积、碳水化合物面积 （CHO） 峰 2 和 3 峰高度、CELC：CHO 和 CELC：SCHO 的面积比α螺旋高度降低，β片高度降低，条带强度减弱。 此外，当猪饲喂膨化BSG日粮时，能量、干物质、粗蛋白、酸性洗涤纤维、中性洗涤纤维、纤维素和半纤维素的DE和ME值以及ATTD增加（P < 0.05）。饲喂挤压日粮时，Arg、His、Lys、Val 和 Gly 的 AID 和 SID 增加，而 Ile 和 Leu 的 AID 和 SID 降低 （P < 0.05）。本研究发现，猪营养物质的 ATTD 和 AA 消化率与蛋白质的分子结构呈正相关，与碳水化合物的分子结构呈负相关 （P < 0.05）。这些发现表明，挤压有可能通过改变 BSG 的化学成分、表面结构和分子结构来提高其营养物质消化率。