Enzyme assisted ensiling of alfalfa with enzymes by solid substrate fermentation
Introduction
Alfalfa contains a low amount of fermentable carbohydrates and has a large buffer capacity that prevents fast lactic acid fermentation with the necessary pH drop. Ensiling may be improved by wilting and/or with silage additives. Earlier chemical additives (inorganic and organic acids and their salts, formalin, nitrate and nitrite compounds, etc.) were used, lately biological additives have gained acceptance. These are safer for human and animal health and the environment (Bolsen and Heidker, 1985).
Newer biological silage additives contain special homofermentative lactic acid bacteria (LAB) and cell wall degrading enzymes, which provide carbohydrate for LAB (Weinberg and Muck, 1996). The high cost of commercial enzymes has so far prevented the widespread use of such combined additives. A cheap enzyme source is needed for the economic viability of this technology. Recently, we obtained good results in the ensiling of sweet sorghum with LAB and an in situ crude enzyme prepared on extracted sweet sorghum pulp by SSF (Schmidt et al., 1997).
The purpose of the present study was to apply an SSF crude enzyme to alfalfa ensiling and to determine if enough fermentable carbohydrates are produced during ensiling to help a rapid lactic acid fermentation and the production of a stable silage.
Section snippets
Substrate
Alfalfa was harvested by hand, then wilted for one experiment. The wilted and non-wilted alfalfa came from different harvests. Both wilted and non-wilted alfalfa was finely chopped to 0.5–1.0 cm particles with normal farm equipment. The nutrient composition of wilted and non-wilted alfalfa were:Nutrient Non-wilted alfalfa Wilted alfalfa Dry matter (DM) (g/kg) 215.3 307.3 Crude protein (g/kg DM) 256.0 220.1 Crude fat (g/kg DM) 16.6 15.3 Crude fiber (g/kg DM) 255.6 247.1 Ash (g/kg DM) 97.6 81.3 Nitrogen-free
Lactic acid fermentation
The LAB silage additive was beneficial only for wilted alfalfa (Table 1). There was more lactic acid, less acetic acid and less NH3 with faster pH drop compared with control. This agrees with the observation of other authors with alfalfa and grass ensiling Anderson et al., 1989, Kennedy et al., 1989, Tengerdy et al., 1991, McDonald et al., 1991, Schmidt et al., 1993, Hristov, 1993.
The combined treatment of LAB + enzyme (both commercial and crude SSF enzyme) further improved the fermentation
Acknowledgements
This research was supported by a US–Hungary Science Cooperation Grant, NSF INT-8722686, by a NATO Linkage Grant LG 920571 between the US and Hungary, by a US–Hungary Joint Board Grant No. 307/92 and in part by Hungarian projects OTKA T 023063, OTKA T 029387 and FKFP 0516/1999.
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