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The degradation of lactic acid under anoxic conditions was studied in several strains of Lactobacillus buchneri and in close relatives such as Lactobacillus parabuchneri, Lactobacillus kefir, and Lactobacillus hilgardii. Of these lactobacilli, L. buchneri and L. parabuchneri were able to degrade lactic acid under anoxic conditions, without requiring an external electron acceptor. Each mole of lactic acid was converted into approximately 0.5 mol of acetic acid, 0.5 mol of 1,2-propanediol, and traces of ethanol. Based on stoichiometry studies and the high levels of NAD-linked 1, 2-propanediol-dependent oxidoreductase (530 to 790 nmol min(-1) mg of protein(-1)), a novel pathway for anaerobic lactic acid degradation is proposed. The anaerobic degradation of lactic acid by L. buchneri does not support cell growth and is pH dependent. Acidic conditions are needed to induce the lactic-acid-degrading capacity of the cells and to maintain the lactic-acid-degrading activity. At a pH above 5.8 hardly any lactic acid degradation was observed. The exact function of anaerobic lactic acid degradation by L. buchneri is not certain, but some results indicate that it plays a role in maintaining cell viability.

Aerobic deterioration of silages is initiated by (facultative) aerobic micro‐organisms, usually yeasts, that oxidize the preserving organic acids. In this study, a Lactobacillus buchneri strain isolated from maize silage was evaluated for its potential as a bacterial inoculant that enhances aerobic stability of silages. In four experiments, chopped whole crop maize (30–43% dry matter (DM)) was inoculated with Lact. buchneri and ensiled in laboratory silos. Uninoculated silages served as controls. Analysis of silages treated with Lact. buchneri at levels of 103−106 cfu g−1 after about 3 months of anaerobic storage showedthat acetic acid and 1‐propanol contents increased with inoculum levels above 104 cfu g−1,whereas lactic acid decreased. Propionic acid, silage pH and DM loss increased withinoculum levels above 105 cfu g−1. Time course experiments with maize inoculated with Lact. buchneri at 4 × 104−2 × 105 cfu g−1 showed that up to 7–14 d after ensiling, Lact. buchneri had no effect on silage characteristics. Thereafter, the lactic acid content of the inoculated silages declined and, simultaneously, acetic acid and, to a lesser extent, propionic acid and 1‐propanol, accumulated. Inoculation reduced survival of yeasts during the anaerobic storage phase and inhibited yeast growth when the silage was exposed to O2, resulting in a substantial improvement in aerobic stability. The results indicate that the use of Lact. buchneri as a silage inoculant can enhance aerobic stability by inhibition of yeasts. The ability of the organism to ferment lactic acid to acetic acid appears to be an important underlying principle of this effect.

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In animal nutrition, incubation of feed samples with CO2/HCO3-buffered rumen fluid is used to predict the nutritional values of the feed. During fermentation, volatile fatty acids (VFAs) are produced, which release CO2 from the buffer through their H + ions. This indirect gas production amounted to 20.8 ml gas per mmol VFA. By incubating glucose, rice starch and cellulose, the relationship between direct and indirect gas production in relation to fermentation kinetics was studied. The total amount of gas formed was found to be dependent on the composition of the fermentation end-products formed. This could be described by: ml g a s = M v ' m m o l H A c + 2 M v . m m o l H B + 0 . 8 7 M v . m m o l Tot. VFA where H A c = acetic acid; HB = butyric acid;and Mv = molar gas volume. No clear relationship was found between the rate of fermentation and total gas production. From rice starch more total gas was produced than from glucose and cellulose, which were fermented faster and slower, respectively.

SummaryAcetic acid bacteria were isolated from maize silages and from samples of maize silage exposed to air. The isolates apparently belonged to the genus Acetobacter. By inoculating maize silage with strains of acetic acid bacteria isolated from silage and by monitoring the development of the microbiota of samples exposed to air it was demonstrated that acetic acid bacteria can be responsible for the onset of aerobic deterioration of maize silage. However, acetic acid bacteria and yeasts often developed simultaneously in uninoculated silage samples exposed to air. In all experiments ethanol was oxidized to acetic acid followed by a rapid oxidation of lactic and acetic acids when ethanol was depleted.

Not coincidentally, deliberative policy analysis has been practiced often in cases that in a very essential sense involve value dissent and major uncertainties: cases of what Beck, Giddens and others have designated reflexive modernisation'. Deliberation, under such circumstances, is to support a synthesising kind of judgment across existing differentiations and distinctions, that is a process of judgement in which assumptions, knowledge claims, distinctions, roles and identities, normally taken for granted, must be critically scrutinised. Thus, existing institutions tend to provide inadequate guidance for such`reflexive design'. In this paper, we shed some light on this challenge by telling and reviewing the story of Programme 348:`Future Livestock Production Systems' for the reflexive modernisation of Dutch agriculture, following major crises in the country's husbandry sector. Although an institutional arrangement had been created that was rather favourable to reflexive design, the programme encountered significant difficulties, which we argue are rooted in the institutions that have emerged throughout agricultural modernisation over the past century. We then use Wenger's insights on`communities of practice', as a framework to both understand how established institutions could manifest themselves in P348's reflexive arrangement, and how these difficulties have been dealt with in more or less successful ways. With the insights thus gained, we wish to contribute to the still underdeveloped literature on reflexive design in the trail of recent work by Forester and Fischer.

Due to intensive fertilizer application most silage crops contain appreciable amounts of nitrate. During silage fermentation the nitrate is completely or partially degraded. End-products are ammonia and nitrous oxide with nitrite and nitric oxide occurring as intermediates. Factors that influence nitrate degradation and the levels of end products and intermediates found in silages are reviewed. The role of plant nitrate reductase and of enterobacteria, clostridia and lactobacilli in nitrate catabolism and the significance for silage quality are discussed. Attention is paid to silofiller's disease, an illness of farm workers that is caused by inhalation of oxides of nitrogen, and to the occurrence of nitrosamines in silages.