Effects of different wet distillers' grains ratios on fermentation quality, nitrogen fractions and bacterial communities of total mixed ration silage

Abstract

Objective: Wet distiller's grains (WDG) are rich in crude protein, yet challenging to preserve. Nevertheless, incorporating WDG into total mixed ration (TMR) silage holds promise for enhancing fermentation quality. This study investigated the effects of varying WDG proportions on nitrogen composition, fermentation quality, and microorganisms in TMR silage.

Methods: Three TMR formulations were prepared: (1) 0% WDG (T0), (2) 15% WDG (T15), and (3) 30% WDG (T30) were ensiled for 7, 15, 30 and 60 days.

Results: After 7 days of ensiling, butyric acid was detected in T0 and T15 groups, while T30 exhibited significantly lower levels (p < 0.05). Both T15 and T30 treatments led to improved V-scores of TMR silage. Non-protein nitrogen (NPN) production was slower in T30, with significant increases observed in NPN levels for T0 and T15 after 30 days (p < 0.05). However, the abundance of Clostridium was extremely low in the present study. Protein degradation and and butyric acid production may be attributed to Weissella.

Conclusion: The fermentation quality of TMR silage is always decreasing during storage, so its storage time should be minimized. Incorporating 30% WDG reduced abundance of Weissella, resulting in less protein degradation and better fermentation quality in TMR silage.

Keywords: Bacterial community; Fermentation quality; Nitrogen fraction; Proteinase activity; Total mixed ration silage; Wet distillers’ grains.

Fig. 1

The variation in V-score during the ensiling of total mixed ration (TMR) silage. V-score is used to indicate silage quality based on volatile fatty acid and ammonia-nitrogen contents. T0, T15, and T30 represent TMR with 0%, 15%, and 30% wet distillers’ grains (dry matter), respectively. Bars indicate the standard errors of the means. Significant differences between means within the same treatment (a, b, c, d) or within the same storage period (A, B, C) are denoted by different superscripts (p < 0.05)

Fig. 2

The dynamics of proteinase activity (a) and the levels of nitrogen fractions (b) during the ensiling of total mixed ration (TMR) silage. Error bars represent the standard errors of the means. DM, dry matter; TN, total nitrogen; NPN, non-protein nitrogen; Peptide-N, peptide nitrogen; AA-N, amino acid nitrogen; NH₃-N, ammonia-nitrogen. T0, TMR with 0% wet distillers’ grains (DM); T15, TMR with 15% wet distillers’ grains (DM); T30, TMR with 30% wet distillers’ grains (DM)

Fig. 3

Variations in the overall bacterial relative abundance (a) and significant bacterial genera (b) in total mixed ration (TMR) silage. Significant differences between means within the same treatment (a, b, c) or within the same storage period (A, B) are indicated by different superscripts (p < 0.05). Error bars represent the standard error of the means. T0, TMR with 0% wet distillers’ grains (dry matter, DM); T15, TMR with 15% wet distillers’ grains (DM); T30, TMR with 30% wet distillers’ grains (DM)

Fig. 4

Alpha diversity indices (a) and PCA plots (b) of total mixed ration silage throughout ensiling. Error bars represent the standard errors of the means. T0, 0% wet distillers’ grains; T15, 15% wet distillers’ grains; T30, 30% wet distillers’ grains

Fig. 5

Heatmap depicting Spearman correlation analysis between bacterial community composition, fermentation parameters, and nitrogen fractions. NPN, non-protein nitrogen; Peptide-N, peptide nitrogen; AA-N, amino acid nitrogen; NH₃-N, ammonia nitrogen. *p < 0.05; **p < 0.01