WITH surplus potatoes available at extremely attractive prices compared to their relative feed value, many livestock producers could make good use of this opportunity.

Potatoes have a similar metabolisable energy (ME) content to barley at 13.3MJ/kgDM, but are slightly lower in crude protein (CP) at 9% of DM. With barley at £115/t and rapeseed meal at £220/t, potatoes are worth £26/t.

Of course, it is all very well potatoes being cheap at the moment but, with turnout happening soon, they are not really going to be needed. Or are they?

With silage making season approaching, it is worth considering purchasing potatoes for inclusion with the grass. It's a great idea and will reduce feed costs - but there are some golden rules.

When ensiling potatoes with grass:

- The potatoes should be as clean as possible - soil contamination is not good for the ensilage process as it introduces undesirable bacteria, eg clostridia which will result in a poor fermentation (and may even incorporate listeria).

- The mixing ratio should be five parts of grass to one part of potatoes - some producers have used a higher proportion of potatoes.

- Potatoes can be incorporated by making alternate layers of about 0.6m of grass followed by 0.15m of potatoes - but whatever method is used to mix them, aim to have the potatoes completely surrounded by grass so that air pockets are minimised.

Of course, the usual silage making rules apply:

- Wilt grass (to at least 25% DM) to reduce effluent and nutrient loss.

- Take care in cutting, moving and picking up the grass so that no soil is included.

- Chop the grass to aid compaction in the silo and exclusion of air.

- Roll to exclude trapped air.

- Completely seal the silo against entry of air as soon as filling is completed.

With 'average' quality grass silage at 25% DM, the mix of grass and potato silage will have around 11MJ ME/kgDM and 12.5% CP in DM.

Another feed that is usually a good buy at this time of year and through the summer, is draff. A mix of draff and potatoes makes a useful feed since the low CP content of the potatoes is balanced by the higher CP in the draff.

The two feeds can be stored by ensiling them together:

- The mixing ratio should be two parts draff to one part clean potatoes.

- Potatoes should be surrounded by the draff to exclude air pockets.

- If ensiled when the draff is hot, some of the potatoes will be partially cooked and this will reduce the effluent from them.

This mix of draff and potatoes will have around 11.8MJ ME/kgDM and 18%CP in DM.

Sometimes other vegetable surpluses become available but most vegetables have a much lower DM content than potatoes. Therefore, they may not ensile so well with grass and would produce a lot of effluent.