Batch-to-batch variation in carbohydrates molecular structures, nutritive value and biodegradation characteristics in corn coproducts

This study investigated batch-to-batch variations in carbohydrates 1) chemical profile; 2) Cornell Net Carbohydrate and Protein System (CNCPS) carbohydrates subfractions; 3) in situ ruminal degradation kinetics of neutral detergent fiber (NDF); and 4) molecular structure spectral characteristics of carbohydrates (structural carbohydrates, SCHO; cellulosic compounds, CELC; total carbohydrates, TCHO and non-structural carbohydrates, NSCHO) in corn byproducts. The second aim was to correlate the variations in carbohydrates molecular structures with carbohydrates nutritional traits. The corn byproducts selected in this study were corn gluten feed, corn germ, corn germ cake and corn gluten meal. The preprocessed corn kernels were used as control. The results revealed large differences in carbohydrate chemical composition (P < 0.001), CNCPS subfractions (P < 0.001) and rumen degradation kinetics of NDF (P ≤ 0.01) between preprocessed corn kernels and the byproducts. The contents of NDF and non-fiber carbohydrates varied (P ≤ 0.01) among the three batches of corn kernels and the byproducts. Except SCHO area, all the carbohydrates molecular spectral bands areas and ratios differed (P < 0.001) between the preprocessed corn kernels and the byproducts. Significant batch-to-batch variations were observed for different spectral parameters of the byproducts. Regression equations based on carbohydrate spectral data gives relatively good prediction power for carbohydrates chemical profile (P < 0.001; R² = 0.55-0.80), CNCPS subfractions (P < 0.001; R² = 0.62-0.86) and ruminal degradation characteristics of NDF (P < 0.001; R² = 0.78-0.89). In conclusion, batch-to-batch variation was observed in nutritional values of carbohydrates in corn byproducts, and carbohydrates molecular structures spectral data might potentially be used to predict nutritive values of corn and corn byproducts for dairy cows.