Thermoactinomyces vulgaris

Thermoactinomyces vulgaris is a thermophilic bacterium known as a primary agent of organic matter degradation during the storage of agricultural commodities. Rather than infecting living plants, this microorganism thrives in harvested biomass, utilizing heat-generating processes to dominate microbial communities within hay, straw, and stored grain.

The host substrates for this organism include a wide range of harvested forage and feed crops. Whenever moisture levels exceed safety limits, this bacterium colonizes plant material, leading to significant nutrient losses. It is particularly prevalent in densely packed hay bales and improperly cured forage that cannot dissipate internal metabolic heat.

Symptoms of infestation are primarily characterized by severe self-heating, with internal temperatures often rising above 60°C. Affected material changes color to brown or black, becomes brittle, and emits a musty, pungent odor. A whitish or greyish layer of bacterial spores is often visible on the surface of the degraded plant stalks and leaves.

Development and spread are triggered by conditions of high humidity combined with poor aeration. As other microorganisms initiate the heating process, Thermoactinomyces vulgaris rapidly multiplies, sustaining and intensifying the heat production. This self-perpetuating cycle can continue until the biological material becomes severely scorched or combusts.

The economic impact and harmful effects are significant:

• Loss of protein and dry matter in fodder.
• Increased risk of farmer's lung disease (respiratory allergy).
• Fire hazards due to spontaneous combustion in storage.
• Reduction in feed palatability and animal performance.

Protection and preventive measures focus on moisture management and storage technology. Producers should ensure that hay and grain are dried to moisture levels below the threshold of 15-18% before storage. Implementing continuous temperature monitoring and utilizing proper aeration systems in barns are crucial steps to prevent bacterial proliferation and maintain feed quality.