Silage and Hay - a deeper look

Silage and Hay are stored grass.

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Grass can be stored for use in winter in a number of ways:

  1. Silage. Grass contains 1%-5% of free sugar. This can be fermented anaerobically into a lactic fermentation (same preservation method as yoghurt) that will remain stable for years or even decades. Suitable for fertile grassland and usually made from high quality leafy grass before or at the start of flowering (yes, grass has flowers). Ideally grass should be cut, allowed to dry a little to 75% moisture content, and then chopped and taken to the store (silo) and compacted and sheeted with polythene sheet to exclude air.

    Under these circumstances there will be no liquid loss (effluent) and the intake is excellent. Unfortunately this is a near impossibility in most years in the UK. Consequently farmers are usually forced to ensile wetter material and accept some liquid loss. The effluent is highly damaging to watercourses (surface and subterranean) and MUST be collected and either spread thinly on the land or fed back to cattle, who seem to regard it as a tasty, and sometimes mildly alcoholic, drink (it is high in protein).

    Silage can be self-fed by cattle or cut and taken to them. It should have a characteristic and pleasant smell.

  2. Haylage (also typically silage made from maize or wholecrop cereals). This usually has a moisture content of 75% to 55%, for arable crops this is the moisture content at cutting, for grass it involves the first few operations of hay. No effluent, high intakes if well made, but dreadful if the weather is poor. Apart from wholecrop cereal silage it is largely confined to arid areas, typically continental, where it is invariably fed by some automated mechanical system of variable reliability.

  3. Hay. A very high risk operation in the UK and in practice only viable for low fertile situations where the bulk of crop /Ha is quite moderate and preferably downright low. The grass is almost invariably cut well into flowering or even seeding to reduce the amount of water that needs to be removed by the sun. The crop is cut and then repeatedly spread during the day and rowed up at night until the moisture content is reduced to under 15%, and preferably near 10%. It is then baled and carted to the stack. A thin stemmy crop can be turned into hay in 48 hours under hot conditions, but a thick leafy crop can take weeks. Very high risk in a UK situation and because rain during making severely reduces quality (despite re-drying) due to fungal attack and leaf loss, a wet spell during making can result in the whole crop being lost and turned into very expensive manure. The latter is woefully common.

    A variant, "barn dried hay" is when the hay is field dried to about 70% moisture and then baled and the bales stacked in a shed and cold air blown through until it is under 10% moisture content. This is very expensive, commands premium prices, and is much more reliable. It is very rare these days. The bales are usually light and loose.

    If hay is stacked in a barn too wet then the stack has a propensity for spontaneous combustion and several burn down this way each year. Overwet hay is also full of fungal spores which cause 'farmer's lung' to those handling them subsequently.

    Seeds hay is the (very stemmy indeed) hay left after a grass (usually in an arable situation) has been combined for seed. Usually looks good (and so popular with petkeepers) but is of poor if not abysmal quality.

    All in all hay is a vale of tears.