Rumen degradation ratios, available protein, and structural and non-structural carbohydrates: Comparison of frost-damaged wheat with normal wheat

Abstract

In this study, rumen degradation ratios and characteristics of estimated structural carbohydrates (SC), non-structural carbohydrate (starch: ST), and crude protein (CP) in the frost-damaged wheat were determined in dairy cows, using Tamminga’s Rumen Degradation Ratio System. The rumen degradation ratios were compared with the optimum ratio range. Measured ruminal degradation characteristics were soluble fraction (S: ST and CP), undegradable fraction (U: SC and CP), lag time (T0: SC and CP), and rate of degradation (Kd: SC, ST, and CP) of the insoluble but degradable fraction (D: SC, ST, and CP). The results for the S, U, and D fractions and for T0 and Kd were used to calculate the subsequent parameters of the rumen degradation ratios. The overall test weight losses of the frost-damaged wheat were around 24%. The measured characteristics showed significant (P < 0.05) differences between the normal and frost-damaged wheat: (1) rumen available insoluble N (EN), SC (ESC), and ST (EST) were 14 vs. 11 (P < 0.05), 133 vs. 254 (P < 0.05), and 441 vs. 326 g kg-1 DM (P < 0.05), respectively, for the normal and frost-damaged wheat; (2) rumen available soluble N (SN), SC (SSC), and ST (SST) were 3 vs. 6 (P < 0.05), 0 vs. 0, and 86 vs. 84 g kg-1 DM (P > 0.05), respectively; and (3) total rumen available N (FN), SC (FSC) and ST (FST) were 17 vs. 17 (P > 0.05), 139 vs. 254 (P < 0.05), and 527 vs. 410 g kg-1 DM (P < 0.05), respectively. Degradation ratios were calculated based on the measured characteristics. The ratio between rumen available insoluble N and carbohydrates (EN/ECHO = 18 vs. 24 g kg-1, P < 0.05) was significantly lower for the frost-damaged than for the normal wheat. The frost-damaged wheat had numerically higher rumen available soluble N/carbohydrate ratio (SN/SCHO = 89 vs. 35 g kg-1, P > 0.05) and same total rumen available N/carbohydrate ratio (FN/FCHO = 25 vs. 25 g kg-1) than the normal wheat. These results indicated that the normal and frost-damaged wheat differed in degradation characteristics; however, both exhibited a rumen fermentation ratio FN/FCHO within the optimal range (25 to 33 g N kg-1 CHO). Key words: Optimal rumen fermentation, degradation ratio, frost-damaged wheat