Cold weather causes stubble turnip feed risk

Stubble turnips being fed this winter could have seriously deteriorated following the recent cold weather, with frosted crops also potentially toxic, experts warn.

Seed specialists and sheep advisers say lamb finishers with stubble turnips should take “nothing for granted” and must make regular physical checks of their crops to assess “bulb” damage.

The severe weather has even tested the frost tolerance of varieties normally expected to withstand low temperatures well into the New Year, says Ian Wilkinson of Cotswold Seeds.

“Stubble turnips are a popular crop but we must remember this is a “catch crop”, and so even though new varieties have greater ability to cope with these conditions, they are still vulnerable when subjected to such persistent freezing.”

It is commonplace for the green tops to perish in cold weather, but although the roots of new varieties have usually provided a stable feed source despite low temperatures, this winter’s sustained and penetrating frosts have probably damaged crops that farmers would have expected to cope.

“Crops covered in snow may have been protected from the worst effects of the severe frosts but stubble turnips in areas that haven’t had the snow fall could be hardest hit. Even varieties we can usually rely on to feed lambs in a bad winter are now on the cusp of tolerance and must be monitored carefully to ensure they are still providing enough feed for lambs.

“As soon as the bulbs start to go mushy, that’s it; they just won’t last any longer,” adds Mr Wilkinson.

ADAS sheep consultant Kate Phillips says the massive drop in temperatures was causing deterioration in many root crops, and farmers with lambs on stubble turnips must monitor crops daily.

“Some dry forage – hay or silage – must be available to lambs on turnips and supplementary feed should also be offered. There could be little food value in the worst-affected crops, and even roots that have remained stable are still very cold and unpalatable. Every effort must be made to stop lambs losing condition,” she advises.

But there could also be toxicity risks associated with feeding frosted brassicas. Nutritionists say it has not been a problem they’ve had to deal with before but because of the unprecedented freezing temperatures recorded in some regions there could now be a risk of the freezing process leading to high levels of sulphur building in the roots, which can be highly toxic to sheep. Anyone feeding brassica crops needs to keep a close watch on the severity of frost damage.

The quality of stubble turnips should also be closely monitored when being used to strip-graze beef cattle. Intakes will be reduced where root quality is deteriorating but eating frosted material can cause digestive upsets.

“Cattle may continue to eat roots that have succumbed to frost damage but it’s more likely to be the consumption of very cold material that will cause problems. It can lower the temperature of the rumen and lead to scouring as the digestive system starts to stagnate,” says nutritionist Robert Whiteoak, Gloucester Animal Feeds.

Even when stubble turnips have remained stable, intakes will still lead to a lowering of the rumen temperature. He advises feeding hay or round-bale silage to try to offset the worse effects of the scouring risk.