Given the high cost of concentrate feed and that there are ample supplies of silage on farms, a number of farmers have questioned the potential economics of storing cattle over the winter on a silage-only diet.

While this will help control winter feed costs, the impact this decision will potentially have on cattle performance must also be considered.

A silage-only diet should only be considered where there is an adequate supply of high-quality silage to last the group of animals all winter.

If silage is of moderate quality, animal performance will be poor. While there is a chance of making up some of this weight gain through compensatory growth, it will be vital to get animals back out to grass next March.

However, there are other factors to bear in mind if considering a forage-only diet, or reducing concentrate levels this winter.

Top-quality silage alone will not sustain high levels of weight gain if store cattle are overstocked in slatted sheds.

Also, it is worth remembering cattle will consume an extra 5kg to 6kg freshweight of silage for every 1kg of concentrate removed from the normal winter diet. This should be factored in when calculating how long fodder reserves will last.

Forage analysis

If a forage-only diet is being considered, it is crucial that silage is analysed to determine its feed value.

A follow-up analysis should be taken midwinter as feed value will change as you move through the pit.

High-quality silage will have a dry matter content above 25%, a metabolisable energy (ME) of at least 11.5MJ and crude protein levels between 14% and 16%. The D-value should be 72 and above.

Where D-value slips into the mid 60s and below, the silage will have a higher fibre content, which will limit cattle intakes, and ultimately animal performance.

Weight gain targets

For store cattle that will return to grass next spring, the target should be to achieve a daily liveweight gain of between 0.5kg and 0.7kg/day over the winter. Falling below this target simply extends the period the cattle are on the farm and could ultimately hit final carcase weights. Going above target will limit subsequent performance at grass.

High-quality silage fed to healthy cattle with good genetic potential, and with adequate lying/feeding space, should be capable of sustaining that weight gain without concentrate being offered.

For good-quality silage (D-value around 70), feeding 0.5kg to 1kg/day of ration should ensure animals hit target.

But for every 2% drop in D-Value below 70, concentrate levels should increase by 0.5kg/day to achieve the outlined weight target.

In all these situations, it is also important these animals get out to grass early next spring to avail of compensatory growth.

Cost benefit

While the silage season is now over on most farms, and there is no longer anything that can be done to influence feed quality, it is nonetheless worth comparing the potential feed savings between a high-quality and average-quality forage.

If average quality forage is offered, and it takes 2kg of concentrate per head to sustain comparable performance to a situation where only high-quality forage is fed, across a 150-day winter it is an extra cost of £82.50 per head (assuming concentrate at £275/t). Over a batch of 50 stores it is an extra £4,125.

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