Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada.
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; Department of Animal Nutrition, The University of Agriculture Peshawar, 25130, Peshawar, Pakistan.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Feb 15;191:303-314. doi: 10.1016/j.saa.2017.10.022. Epub 2017 Oct 14.
Protein solubility, ruminal degradation and intestinal digestibility are strongly related to their inherent molecular makeup. This study was designed to quantitatively evaluate protein digestion in the rumen and intestine of dairy cattle, and estimate the content of truly metabolizable protein (MP) in newly developed cool-season forage corn cultivars. The second objective was to quantify protein inherent molecular structural characteristics using advance molecular spectroscopic technique (FT/IR-ATR) and correlate it to protein metabolic characteristics. Six new cool-season corn cultivars, including 3 Pioneer (PNR) and 3 Hyland (HL), coded as PNR-7443R, PNR-P7213R, PNR-7535R, HL-SR06, HL-SR22, HL-BAXXOS-RR, were evaluated in the present study. The metabolic characteristics, MP supply to dairy cattle, and energy synchronization properties were modeled by two protein evaluation models, namely, the Dutch DVE/OEB system and the NRC-2001 model. Both models estimated significant (P<0.05) differences in contents of microbial protein (MCP) synthesis and truly absorbable rumen undegraded protein (ARUP) among the cultivars. The NRC-2001 model estimated significant (P<0.05) differences in MP content and degraded protein balance (DPB) among the cultivars. The contents MCP, ARUP and MP were higher (P<0.05) for cultivar HL-SR06, resulting in the lowest (P<0.05) DPB. However, none of the cultivars reached the optimal target hourly effective degradability ratio [25gNg/kg organic matter (OM)], demonstrating N deficiency in the rumen. There were non-significant differences among the cultivars in molecular-spectral intensities of protein. The amide I/II ratio had a significant correlation with ARUP (r=-0.469; P<0.001) and absorbable endogenous protein (AECP) (P<0.001; r=0.612). Similarly, amide-II area had a weak but significant correlation (r=0.299; P<0.001) with RUP and ARUP, and with AECP (P<0.001; r=0.411). Except total digestible nutrients and AECP, the amide-I area did not show significant correlations with DVE/OEB and NRC predicted protein fractions. This study shows that molecular spectroscopy can be potentially used as a rapid tool to quantify protein molecular makeup and screen the protein nutritive value of forage corn.
蛋白质的溶解度、瘤胃降解率和肠道消化率与其内在的分子结构密切相关。本研究旨在定量评估奶牛瘤胃和肠道中的蛋白质消化情况，并估计新开发的冷季饲用玉米品种中真正可代谢蛋白质（MP）的含量。第二个目标是使用先进的分子光谱技术（FT/IR-ATR）定量评估蛋白质内在分子结构特征，并将其与蛋白质代谢特性相关联。本研究评估了 6 个新的冷季玉米品种，包括 3 个先锋（PNR）和 3 个海兰（HL），分别为 PNR-7443R、PNR-P7213R、PNR-7535R、HL-SR06、HL-SR22、HL-BAXXOS-RR。本研究采用荷兰 DVE/OEB 系统和 NRC-2001 模型对代谢特性、奶牛 MP 供应和能量同步特性进行了建模。两个模型均估计出品种间微生物蛋白（MCP）合成和真正可吸收瘤胃未降解蛋白（ARUP）的含量存在显著差异（P<0.05）。NRC-2001 模型估计出品种间 MP 含量和降解蛋白平衡（DPB）存在显著差异（P<0.05）。HL-SR06 品种的 MCP、ARUP 和 MP 含量较高（P<0.05），导致 DPB 最低（P<0.05）。然而，没有一个品种达到最佳的目标每小时有效降解率[25gNg/kg 有机质（OM）]，表明瘤胃存在氮缺乏。品种间蛋白质分子光谱强度无显著差异。酰胺 I/II 比值与 ARUP（r=-0.469；P<0.001）和可吸收内源性蛋白（AECP）（P<0.001；r=0.612）显著相关。同样，酰胺-II 面积与 RUP 和 ARUP 以及 AECP 呈弱但显著相关（r=0.299；P<0.001）。除了总可消化养分和 AECP 外，酰胺-I 面积与 DVE/OEB 和 NRC 预测的蛋白质分数均无显著相关性。本研究表明，分子光谱学可作为一种快速工具，用于定量评估蛋白质的分子结构，并筛选饲用玉米的蛋白质营养价值。
