🌾 Silage

Silage (also called ensilage) is green fodder kept without air. The crop is chopped, packed down hard and covered, and bacteria turn its sugars into acids, mostly lactic acid. That acid is the preservative, and the feed keeps for months. Corn is the best crop for the job, but grasses, alfalfa, small grains and sorghum are ensiled too.

Moisture decides everything. North Carolina State Extension says never to ensile above 70% moisture (below 30% dry matter), because of seepage and the wrong kind of fermentation. Corn is cut at 30–35% dry matter and packed at once, while alfalfa and grasses are wilted first. The first day is aerobic. Then fermentation runs from a week to more than a month, and pH falls from about 6.0 to 3.8–5. If you open a silo before 3 to 6 weeks, you are too early.

Haylage differs from silage only in water. High-moisture silage has up to 30% dry matter. Medium silage has 30–40%, and haylage or wrapped bales roughly 40–60%.

Silage can be a problem for cheese. If the crop is too wet or soil gets in (cut too low, or carried in on tractor tyres), clostridia multiply and butyric acid appears, whereas good corn silage has none. Their spores in milk cause late blowing in hard cheeses such as Grana Padano, a defect that shows up during ripening. In a 2023 study, cheese made from milk with under 200 spores per litre avoided it or had much less.

In 1945 the Finnish chemist Artturi Virtanen won the Nobel Prize in Chemistry. His 1932 method acidified hay with hydrochloric and sulfuric acids and kept the protein and vitamins. Cows could give nutritious milk all year without imported feed. Winter feeding of cows still rests on that idea.