Rivero M Jordana, Alomar Daniel, Valderrama Ximena, Le Cozler Yannick, Velásquez Alejandro, Haines Deborah
Escuela de Agronomía,Facultad de Recursos Naturales,Universidad Católica de Temuco,Temuco 4780000,Chile.
Instituto Producción Animal,Facultad de Ciencias Agrarias,Universidad Austral de Chile,5090000 Valdivia,Chile.
J Dairy Res. 2016 Aug;83(3):345-51. doi: 10.1017/S0022029916000364.
The objective of this study was to compare the prediction efficiency of IgG concentration in bovine colostrum by NIRS, using liquid and dried (Dry-Extract Spectroscopy for Infrared Reflectance, DESIR) samples by transflectance and reflectance modes, respectively. Colostrum samples (157), obtained from 2 commercial Holstein dairy farms, were collected within the first hour after calving and kept at -20 °C until analysis. After thawing and homogenisation, a subsample of 500 mg of liquid colostrum was placed in an aluminium mirror transflectance cell (0·1 mm path length), in duplicate, to collect the spectrum. A glass fiber filter disc was infused with another subsample of 500 mg of colostrum, in duplicate, and dried in a forced-air oven at 60 °C for 20 min. The samples were placed in cells for dry samples to collect the spectra. The spectra in the VIS-NIR region (400-2500 nm) were obtained with a NIRSystems 6500 monochromator. Mathematical treatments, scatter correction treatments and number of cross-validation groups were tested to obtain prediction equations for both techniques. Reference analysis for IgG content was performed by radial immunodiffusion. The DESIR technique showed a higher variation in the spectral regions associated with water absorption bands, compared with liquid samples. The best equation for transflectance method (liquid samples) obtained a higher coefficient of determination for calibration (0·95 vs. 0·94, respectively) and cross validation (0·94 vs. 0·91, respectively), and a lower error of cross validation (9·03 vs. 11·5, respectively) than the best equation for reflectance method (DESIR samples). In final, both methods showed excellent capacity for quantitative analysis, with residual predictive deviations above 3. It is concluded that, regarding accuracy of prediction and time for obtaining results of IgG from bovine colostrum, NIRS analysis of liquid samples (transflectance) is recommended over dried samples (DESIR technique by reflectance).
本研究的目的是比较近红外光谱法（NIRS）分别采用透反射和反射模式对液态和干燥（用于红外反射的干提取物光谱法，DESIR）牛初乳样品中IgG浓度的预测效率。从2个商业化荷斯坦奶牛场采集的157份初乳样品在产犊后1小时内收集，并在-20°C下保存直至分析。解冻并匀浆后，将500mg液态初乳的子样品一式两份放入铝镜透反射池中（光程长度为0.1mm）以采集光谱。将另一个500mg初乳子样品一式两份注入玻璃纤维滤盘，并在60°C的强制通风烘箱中干燥20分钟。将样品放入用于干燥样品的池中以采集光谱。使用NIRSystems 6500单色仪获得可见-近红外区域（400-2500nm）的光谱。测试了数学处理、散射校正处理和交叉验证组数量，以获得两种技术的预测方程。通过径向免疫扩散法进行IgG含量的参考分析。与液态样品相比，DESIR技术在与吸水带相关的光谱区域显示出更高的变化。透反射法（液态样品）的最佳方程在校准（分别为0.95对0.94）和交叉验证（分别为0.94对0.91）方面获得了更高的决定系数，并且交叉验证误差（分别为9.03对11.5）比反射法（DESIR样品）的最佳方程更低。最终，两种方法均显示出出色的定量分析能力，剩余预测偏差均高于3。得出的结论是，就预测准确性和从牛初乳中获得IgG结果的时间而言，建议对液态样品进行NIRS分析（透反射）而非干燥样品（通过反射的DESIR技术）。
