Differentiation of mixtures of co-product blend with barley grain based on Fourier transform infrared attenuated total reflection molecular spectroscopy: Carbohydrate molecular spectral profiles and nutritive characteristics in dairy cattle

The objectives of this study were to (1) differentiate mixtures of a co-product blend (70:30% mixture of wheat:corn before bioethanol fermentation) from bioethanol processing with barley grain based on Fourier transform infrared attenuated total reflection molecular spectroscopy with cluster analysis, (2) elucidate the effects of the co-product blend on the molecular structure spectral profile and nutritive characteristics of the hull-less barley carbohydrate (CHO) in dairy cattle, and (3) quantify the relationship between the CHO molecular structure spectral profiles and CHO nutritive characteristics of the mixtures in dairy cattle. The parameters assessed for CHO molecular structure spectral profiles included molecular spectral peak area and height intensities of lignin, structural CHO (STCHO), cellulosic compounds, and total CHO. The parameters assessed for CHO nutritive characteristics included the CHO nutrient profiles, CHO subfractions, energy values, and rumen-fermentable organic matter supply. Hull-less barley grains and the co-product blend were mixed according to the ratio of 100:0 (B100), 75:25, 50:50, 25:75, and 0:100 (BD100). The results showed that when the co-product blend was included at the different ratios, the predicted rumen-fermentable organic matter supply in the rumen was significantly decreased from 632 (B100) to 518 g/kg of dry matter (DM; BD100). The effective degradable dry matter in the rumen and the effective degradable starch in the rumen were also significantly decreased from 672 and 482 g/kg of DM (B100) to 475 and 43 g/kg of DM (BD100), respectively. By using Fourier transform infrared attenuated total reflection spectroscopy, we identified were significant changes in the spectral profiles of the CHO molecular structure in terms of lignin, STCHO, cellulosic compounds, and total CHO spectral peak area and height and their ratios. Pearson analysis results suggested strong correlations between lignin peak area, cellulosic compound area, and total CHO peak area and CHO nutrient profiles except energy values (net energy for lactation at 3 times maintenance intake, net energy for maintenance, and net energy for gain). No correlation was observed between STCHO peak area and CHO nutrient profiles in the mixture samples.