Drought-delayed silage: hitting 72-75% DMD targets this winter

Milking cows need silage at 72-75% dry matter digestibility (DMD), but after a two-month drought delayed fertiliser and pushed a large share of cuts past mid-September, many farms are heading into winter with forage that will fall well short of that mark.

The chain of cause is straightforward. Drought held back fertiliser applications, which held back the cut. Grass then grew fast once rain returned, but daylight was already well back by harvest, and much of the silage in the yard came in relatively poor in quality as a result.

The core problem is sugar. Farms want to see sugars above 3% at cutting to achieve good fermentation, and that target is near impossible in mid- to late September — never mind October-cut silage. Sugars such as glucose are broken down by bacteria, producing lactic acid as a by-product. That lactic acid does the preserving. No sugars, no preservation.

What does poor fermentation actually cost?

The penalties stack up fast. Low-sugar silage preserves badly, which means low DMD, undesirable nutritional values and ultimately more waste — enough, in some cases, to give a false sense of security when farmers calculate the winter fodder budget. What looks adequate in the pit can shrink considerably once refusals and spoilage are counted.

Farmers will still have to make the best of what is in the yard. That means feeding strategically, and it starts with one cheap, decisive move.

Why silage testing comes first

Every farm should have its silage tested before it enters the diet. Testing saves money in the long run because it allows targeted feeding — matching concentrate and mineral rates to what the forage actually contains, rather than what the farmer assumes it contains.

The results should be used to ration silage by class of stock. First-cut silage will more than likely be the best quality in the yard, and it should be reserved accordingly.

The working targets, per the guidance:

• Milking cows: DMD of at least 72-75%. Keep the best first cut for the milking herd in spring, or for winter milkers.
• Dry cows needing moderate body condition score (BCS) gain: can be managed at 68-70% DMD.
• Energy (UFL): 0.83-0.88 UFL for milking cows and young stock.
• Crude protein (CP): above 14%. Lower DMD and/or lower nitrogen (N) application will pull CP down.
• PDIE (metabolisable energy supply, determined by UFL and CP levels): ideally 80g/kg.
• Intake value (indicates silage intake potential): over 105g/kg for cows milking through the winter.

Which numbers flag the milk fever risk?

Potassium (K) content deserves close attention. High-K silage fed from two weeks pre-calving increases the chances of milk fever. The threshold: K should sit below 2.2% pre-calving and during lactation, while readings over 2.4% — the safe direction on the other side of the range cited — pose no risk on that measure. It's a simple line on the lab report, but it maps directly to calving-season health outcomes.

Why the five-week fermentation window matters

With weather turning and grass growth falling back, silage will soon return to the diet — but only after fermentation has finished. Allow a minimum of five weeks between cutting date and feeding. Silage cut in the first 10 days of October should not be touched until mid-November.

There's a balance at play here. Silage cut with low dry matter (DM) in October will not store well, so farmers should aim to feed those pits early — in the dry period, or from mid-November once fermentation has completed — rather than holding them deep into the winter.

How should concentrates and minerals change?

When feeding late-cut silage, alter concentrate and mineral feeding rates to match the silage test results. The rule is simple: low-DM silage requires more concentrates to hold the diet's energy and protein balance.

Teagasc has also advised farms to feed on a regular daily basis, ensuring fresh silage is continuously placed in front of stock, with refusals regularly removed to prevent high volumes of wastage. Daily discipline at the feed face, not one-off management, is what limits losses on poor-quality forage.

What should farmers watch next?

The immediate action for any farm with October-cut forage in the yard: get the test booked now, match rations to the lab sheet rather than the calendar, and hold anything cut after early October until at least mid-November. Watch K levels closely in the fortnight before calving, and adjust concentrate rates upward where DM comes back low — the fodder budget that looked safe on paper depends on it.