Yari Mojtaba, Valizadeh Reza, Nnaserian Abbas Ali, Jonker Arjan, Yu Peiqiang
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, S7N 5A8, Canada.
Department of Animal Science, Ferdowsi University of Mashhad, Mashhad 91775-1163, Iran.
Asian-Australas J Anim Sci. 2017 Nov;30(11):1575-1589. doi: 10.5713/ajas.16.0756. Epub 2017 Mar 21.
This study was conducted to determine molecular structures related to carbohydrates and lipid in alfalfa hay cut at early bud, late bud and early flower and in the afternoon and next morning using Fourier transform infrared spectroscopy (FT/IR) and to determine their relationship with alfalfa hay nutrient profile and availability in ruminants.
Chemical composition analysis, carbohydrate fractionation, in situ ruminal degradability, and DVE/OEB model were used to measure nutrient profile and availability of alfalfa hay. Univariate analysis, hierarchical cluster analysis (CLA) and principal components analysis (PCA) were conducted to identify FT/IR spectra differences.
The FT/IR non-structural carbohydrate (NSCHO) to total carbohydrates and NSCHO to structural carbohydrate ratios decreased (p<0.05), while lignin to NSCHO and lipid CH3 symmetric to CH2 symmetric ratios increased with advancing maturity (p<0.05). The FT/IR spectra related to structural carbohydrates, lignin and lipids were distinguished for alfalfa hay at three maturities by PCA and CLA, while FT/IR molecular structures related to carbohydrates and lipids were similar between alfalfa hay cut in the morning and afternoon when analyzed by PCA and CLA analysis. Positive correlations were found for FT/IR NSCHO to total carbohydrate and NSCHO to structural carbohydrate ratios with non-fiber carbohydrate (by wet chemistry), ruminal fast and intermediately degradable carbohydrate fractions and total ruminal degradability of carbohydrates and predicted intestinal nutrient availability in dairy cows (r≥0.60; p<0.05) whereas FT/IR lignin to NSCHO and CH3 to CH2 symmetric stretching ratio had negative correlation with predicted ruminal and intestinal nutrient availability of alfalfa hay in dairy cows (r≥-0.60; p<0.05).
FT/IR carbohydrate and lipid molecular structures in alfalfa hay changed with advancing maturity from early bud to early flower, but not during the day, and these molecular structures correlated with predicted nutrient supply of alfalfa hay in ruminants.
本研究旨在利用傅里叶变换红外光谱（FT/IR）测定在苜蓿初花期、盛花期和初花期下午及次日上午刈割的苜蓿干草中与碳水化合物和脂质相关的分子结构，并确定它们与苜蓿干草营养成分及反刍动物可利用性之间的关系。
采用化学成分分析、碳水化合物分级、瘤胃原位降解率和DVE/OEB模型来测定苜蓿干草的营养成分及可利用性。进行单因素分析、层次聚类分析（CLA）和主成分分析（PCA）以识别FT/IR光谱差异。
随着成熟度的增加，FT/IR非结构性碳水化合物（NSCHO）与总碳水化合物的比率以及NSCHO与结构性碳水化合物的比率降低（p<0.05），而木质素与NSCHO的比率以及脂质CH3对称与CH2对称的比率增加（p<0.05）。通过PCA和CLA可区分三种成熟度苜蓿干草中与结构性碳水化合物、木质素和脂质相关的FT/IR光谱，而通过PCA和CLA分析，上午和下午刈割的苜蓿干草中与碳水化合物和脂质相关的FT/IR分子结构相似。FT/IR NSCHO与总碳水化合物的比率以及NSCHO与结构性碳水化合物的比率与非纤维碳水化合物（通过湿化学法）、瘤胃快速和中度可降解碳水化合物组分以及碳水化合物的总瘤胃降解率和奶牛的预测肠道营养可利用性呈正相关（r≥0.60；p<0.05），而FT/IR木质素与NSCHO的比率以及CH3与CH2对称拉伸比率与奶牛苜蓿干草的预测瘤胃和肠道营养可利用性呈负相关（r≥-0.60；p<0.05）。
苜蓿干草中FT/IR碳水化合物和脂质分子结构随成熟度从初花期到初花期增加而变化，但在一天内无变化，且这些分子结构与反刍动物苜蓿干草的预测营养供应相关。
