School of Life Science and Engineering, Foshan University, Foshan, China; Department of Animal and Poultry Science, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, Canada.
Department of Animal and Poultry Science, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, Canada.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Jun 15;234:118220. doi: 10.1016/j.saa.2020.118220. Epub 2020 Mar 9.
The objective of this study was to evaluate the effects of heating process on protein molecular structure from ruminal degradation residues in cool-climate adapted faba bean seeds in relation to crude protein (CP), in situ degradation kinetics, rumen protein degradation and intestinal protein digestion parameters in dairy cows. Seeds of six faba bean varieties with low (Snowbird, Snowdrop, 219_16) and normal tannin (Fatima, 346_10, SSNS_1) were collected from three different locations, and were heated 3 min by microwave irradiation (MI, dry heating) or heated 1 h by steam pressure toasting (SP, moist heating) or kept raw as a control. Heat treated samples were used for rumen incubating 24, 12, 8, 4, 2, 0 h(s) in two replicate runs and then residues from 12 h of rumen degradation were used for three steps in vitro technique for determining intestinal protein digestion. Attenuated total reflectance Fourier transforms infrared spectroscopy (ATR-Ft/IRS) was used for analyzing protien molecular structure of residual faba bean seeds. The results showed that SP increased the intensities of amide I, amide II, α-helix and β-sheet but decreased amide I to amide II height and area ratio, α-helix to β-sheet height ratio from 12 and 24 h of ruminal degradation, and MI decreased all the intensities of amide I, amide II, α-helix and β-sheet and ratios except amide I to amide II area ratio of residues from 24 h of ruminal degradation. Additionally, the intensities of amide I, amide II, α-helix and β-sheet had a unique pattern of increasing first and then decreasing with the increasing ruminal digestion time for SP treatment, while amide I to amide II height and area ratio, α-helix to β-sheet height ratio were declining. For the MI groups, this pattern was not observed and the intensities were rather consistent across the digestion process. Rumen protein degradation parameters including rumen bypass crude protein (BCP) or rumen undegradable protein (RUP) and rumen degradable protein (RDP) closely correlated with protein molecular structure of to peak heights, areas and ratios. Regression equations based on residual protein molecular structure presented a good estimation power for soluble fraction (S, R = 0.79), degradable fraction (D, R = 0.805), BCP (R = 0.941), RUP (R = 0.941) and RDP (R = 0.811). Overall, heat-induced changes in rumen residual protein molecular structures were related to CP, in situ degradation kinetics, rumen protein degradation and rumen protein digestion parameters.
本研究旨在评估在与粗蛋白（CP）、原位降解动力学、瘤胃蛋白降解和奶牛肠道蛋白消化参数相关的情况下，加热过程对凉爽气候适应的蚕豆种子瘤胃降解残渣中蛋白质分子结构的影响。从小麦蚕豆品种（Snowbird、Snowdrop、219_16）和普通单宁（Fatima、346_10、SSNS_1）中收集了六个品种的蚕豆种子，然后用微波辐射（MI，干热）加热 3 分钟或用蒸汽压力烤（SP，湿热）加热 1 小时，或作为对照保持原样。将加热处理的样品在两个重复运行中进行 24、12、8、4、2 和 0 小时（s）的瘤胃孵育，然后使用三步体外技术对 12 小时瘤胃降解后的残渣进行肠道蛋白消化。采用衰减全反射傅里叶变换红外光谱（ATR-Ft/IRS）分析残余蚕豆种子的蛋白质分子结构。结果表明，SP 增加了酰胺 I、酰胺 II、α-螺旋和β-折叠的强度，但降低了 12 和 24 小时瘤胃降解时酰胺 I 与酰胺 II 的高度比和面积比，以及 MI 降低了所有酰胺 I、酰胺 II、α-螺旋和β-折叠的强度以及除 24 小时瘤胃降解残渣的酰胺 I 与酰胺 II 面积比以外的所有比值。此外，SP 处理后，酰胺 I、酰胺 II、α-螺旋和β-折叠的强度呈现先增加后减少的独特模式，而酰胺 I 与酰胺 II 的高度比和面积比以及α-螺旋与β-折叠的高度比呈下降趋势。对于 MI 组，没有观察到这种模式，并且整个消化过程中强度相当一致。瘤胃蛋白降解参数，包括瘤胃可通过粗蛋白（BCP）或瘤胃未降解蛋白（RUP）和瘤胃可降解蛋白（RDP），与蛋白质分子结构的峰值高度、面积和比值密切相关。基于残余蛋白质分子结构的回归方程对可溶部分（S，R=0.79）、可降解部分（D，R=0.805）、BCP（R=0.941）、RUP（R=0.941）和 RDP（R=0.811）具有很好的估计能力。总体而言，瘤胃残留蛋白质分子结构的热诱导变化与 CP、原位降解动力学、瘤胃蛋白降解和瘤胃蛋白消化参数有关。
