Warm or heating forage is one of those common winter issues that can creep up almost unnoticed. Even when the weather feels cold enough to keep everything quiet, yeasts and moulds will quickly become active once air reaches the clamp. As soon as that happens, the silage starts to heat, energy is burnt off, and unwanted microorganisms begin to grow. This often leads to lower intakes, lower milk yields, reduced DLWG, and at times proper digestive problems in stock.
With forage stocks tight on many farms this winter, it is worth taking a closer look at the clamp to make sure every tonne is working for you rather than disappearing into thin air.
Why Silage Heats, Even in Winter
Heating kicks off the moment oxygen reaches the silage surface. Once exposed, yeasts come back to life, multiply, and burn off valuable nutrients as heat. Cold weather might slow this down, but it certainly does not stop it. The usual triggers tend to be things like a loose sheet that is not held down firmly, rough faces where air can creep in, slow feedout or taking too big a bite at once, shoulders that have been left open to rain or wind, or even carrying warm, unstable silage into the TMR. Every hour the clamp is heating, it is losing ME, and your livestock will feel the effects.
Early Signs That Silage Is Heating
Most farmers notice the knock on effects before realising the clamp is warming up. The obvious clues include silage that feels warm or slightly steamy in the hand, a sweet or yeasty smell that is a bit out of place, cows backing off the ration or picking around it, milk fat slipping, dung looking looser than normal, and any patches of mould, especially the white yeast you see on top and down the sides. You might also see warm spots developing in the TMR a few hours after mixing. Even a small rise in temperature can point to quite a bit of nutrient loss.
Clamp Face, Keeping It Tight, Clean and Safe
A neat, firm, and vertical face is still the best line of defence against air getting in. Avoid clawing or digging silage out, as this leaves the face ragged. A shear grab or block cutter gives a much cleaner finish. Only remove what you expect to feed within twenty-four hours and aim to take roughly 15 to 30 cm per day to stay ahead of spoilage.
Sheet Integrity, Winter Weather’s Quiet Threat
Wind can undo a well-made clamp surprisingly quickly in December. It is worth checking that top sheets are properly weighted with gravel bags rather than tyres on their own. Small holes should be patched straight away, as even a tiny tear can let in surprising amounts of air. Make sure side sheets are still tucked and pulled tight and keep an eye on rain pooling on top as this stretches and weakens the plastic. A quick tidy of the sheet often saves a lot of forage.
Shoulder Management, The Most Exposed Area
Shoulders are usually the first place to heat. Taking clean, vertical cuts right up against the wall helps protect them. Avoid scooping material from the sides and keep the side sheets held down firmly. If shoulder waste crops up year after year, it may be worth looking at stabilisers or additives during clamp building. Losses from the shoulders often account for half of total clamp waste, so tightening this up can make a real difference.
Controlling Heating at Feedout
Silage that has been well made can still heat once mixed if it sits for too long. Regular push ups help, especially for high yielding cows that rely on steady intakes. Try not to mix warm or obviously mouldy patches into the TMR and consider stabilisers such as potassium sorbate based products if heating continues through winter. Keeping the mixer wagon clean reduces yeast build up and keeps the ration more stable.
Final Thoughts
If the clamp is getting hot, you are losing energy, dry matter, and money without realising it. Winter clamp management rarely needs big investment, but a few small changes to how the face is handled, how the sheets are looked after, and how feedout is managed usually pays back very quickly. A cooler clamp gives better forage, more settled cows, and feed costs that are a little easier to live with during the long winter months.