Effects of addition of previously fermented juice prepared from alfalfa on fermentation quality and protein degradation of alfalfa silage

https://doi.org/10.1016/j.anifeedsci.2009.03.001Get rights and content

Abstract

Potential effects of previously fermented juice (PFJ) as a silage additive on fermentation quality and protein degradation of alfalfa silage were investigated. The PFJ was made from alfalfa juice which was anaerobically stored for 2 days. All silages were prepared in mini-silos of 100 ml polypropylene centrifuge tubes. Treatments included four variations: (1) nothing added (control); (2) inoculant of lactic acid bacteria (LAB, “Fast Sile”); (3) addition of previously fermented juice with 2 ml/kg fresh matter (FM) (PFJ2); (4) addition of previously fermented juice with 5 ml/kg FM (PFJ5). Results suggest that silage treated with LAB and PFJ, regardless of addition level, had better fermentation quality than the control silage as evidenced by lower pH and NH3-N concentrations, as well as higher lactic acid production (P<0.05) and less protein degradation as suggested by the low NPN production (P<0.05). In addition, the efficiency of PFJ on alfalfa fermentation quality and protein degradation was more than that of LAB, but there were no differences between PFJ2 and PFJ5 on fermentation quality, although PFJ5 resulted in lower (P<0.05) proteolysis. Results indicate that previously fermented alfalfa juice not only enhances fermentation quality, but also inhibits protein degradation of alfalfa silage and is an effective silage additive.

Introduction

Legumes have long been regarded as difficult to ensile because of their low sugar content and high buffering capacity (McDonald et al., 1991). Previous studies suggested that inoculation of lactic acid bacteria at ensiling could improve fermentation of legume silage by accelerating production of lactic acid to cause acidic conditions to occur as rapidly as possible (Tengerdy et al., 1991, Rooke and Kafilzadeh, 1994). Other studies, however, did not show similar results (Ely et al., 1982, Lindgren et al., 1983). For example, Ohshima et al., 1997a, Ohshima et al., 1997b reported that addition of forage juice that had been stored for 2 days anaerobically (i.e., previously fermented juice, PFJ), could multiply lactic acid bacteria, stimulate lactic acid production, and improve fermentation quality of alfalfa silage. Because PFJ was prepared by culturing microorganisms adherent to grass particles, the efficacy of PFJ on improving fermentation may be more effective than with lactic acid bacteria inocula. Many researchers have also reported that addition of PFJ in grass silages can improve silage quality (Ohshima et al., 1997b, Tamada et al., 1999, Masuko et al., 2002).

It has been demonstrated that the nutritive value of ensiled legume forage is limited by the extensive protein degradation that occurs in many forages during ensiling (McKersie, 1981, Albrecht and Muck, 1991). Proteolysis during fermentation results in extensive degradation of native plant proteins to non-protein N (NPN), which consists principally of ammonia N (NH3-N), free amino acid N (FAA-N) and peptide-bound AA N (Peptide-N) (Ohshima and McDonald, 1978). NPN often accounts for more than half of the total N in alfalfa silage (Muck, 1987) and can result in inefficient N utilization by ruminants (Broderick, 1995). Effects of treatment with additives, such as formic acid, formaldehyde and sulphuric acid on inhibiting protein degradation during ensiling have been studied (Nagel and Broderick, 1992, Vagnoni et al., 1997). While PFJ as a good source of lactic acid bacteria for direct cut silage, and its stimulating effect on fermentation has been identified by many researchers (e.g., Ohshima et al., 1997b, Nishino and Uchida, 1999), there is limited information on protein degradation and NPN formation of PFJ treated forage.

This experiment was completed to evaluate the potential of applying various amounts of PFJ on the fermentation quality and protein degradation of alfalfa silage, and compare effects of PFJ with those of lactic acid bacteria inocula.

Section snippets

Alfalfa forage

Third cut alfalfa (Medicago sativa L.) harvested at an early bloom stage from experimental plots at the Chinese Agricultural University was chopped with a domestic cutter to 1–2 cm lengths. The characteristics of the forage are in Table 1.

Preparation of PFJ

The PFJ was prepared from alfalfa by mixing chopped herbage with five volumes of distilled water and macerating for 30 s using a high-speed blender. The macerate was filtered through two layers of cheesecloth, and aliquots of filtrate were collected in glass

Fresh forage and PFJ

The alfalfa used was a typical legume (Table 1) with a high buffering capacity and a low WSC content (McDonald et al., 1991). The epiphytic lactic acid bacteria count of the fresh forage was 8.32 × 104 cfu/g of fresh matter. After 2 days of anaerobic incubation, PFJ made from alfalfa had a low pH and a large number of lactic acid bacteria.

Silage pH

Silage pH was affected (P<0.01) by additive, ensiling time and there was an additive × ensiling time interaction (Table 2). Application of LAB and PFJ reduced the

Discussion

From the characteristics of the alfalfa in this experiment, its buffering capacity (i.e., 460 meq/kg DM) was higher than that of typical gramineae forage (Woolford, 1984), and the WSC content of 49.4 g/kg DM was lower than the 60–70 g/kg DM recommended theoretical requirement to achieve well-preserved fermentation (Smith, 1962). Thus the alfalfa used was typical of legumes with a high buffering capacity and a low WSC content.

Silage pH is one of main factors that influence the extent of

Conclusion

Our study shows that previously fermented juice (PFJ) can be used as a good source of lactic acid bacteria for direct cut alfalfa silage. Also, its effect as a fermentation stimulator may be comparable, or even better, than commercial bacterial cultures. Moreover, it was also demonstrated that PFJ can effectively inhibit plant protein degradation during ensiling to decrease NPN production. Further research is needed to investigate factors which influence the effective of PFJ and the synergetic

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