With pressure on pastures could toxic plants be on the rise?

By Chris Just BVSc MRCVS, Launceston Practice

There has been a certain amount of media coverage about sycamore poisoning in horses recently, though we don’t treat horses I see it as a sensible precaution to be aware of what is challenging my veterinary colleagues as common ground is often stumbled upon. It seems this condition in horses is being diagnosed more frequently due to a raised awareness and probably was always around but not diagnosed due to a lack of knowledge in the profession. There are several such known unknowns in cattle I am sure, and look forward to being part of these discoveries and solutions with the farming industry.

We at Westpoint Veterinary Group have recently seen an increase in the number of conditions related to extended grazing with mild weather; where the livestock have not agreed that an abundance of autumn grass means an abundance of palatable and nutritious grass! So although much of the counties’ livestock will be safely housed, it is never too late to brush up on our knowledge of common plant poisonings in cattle and sheep, here are some of my favourites.

The unmistakable Ragwort and Cinnabar moth

The unmistakable Ragwort and Cinnabar moth

Ragwort, a well-known toxic weed which has not been very abundant in my experience this year; perhaps in part due to the wonderfully named Cinnabar moth. The larval stage of this wonderful sounding moth is also a gloriously beautiful beast, unmistakably tiger striped and can strip a ragwort plant bare in a day or two. Fantastic stuff! We are probably all too familiar with ragwort and its effects and fortunately cattle and sheep are less prone to the effects, but it has a cumulative toxic effect on the liver which can be hard to link back to episodes of exposure so always be vigilant.

 

Next is St John’s Wort, often known to farmers as it makes cattle in particular very prone to sunburn with some spectacular results. It is surprising therefore that most of us don’t know what it looks like! A picture says a thousand words but in brief description it is usually less than waist high and produces five petalled yellow flowers in June (hence the name after St. Johns day, 24th June!).

St John’s Wort in flower

St John’s Wort in flower

 

On the theme of worts also look out for Water Dropwort, as its name suggests it likes water and ditches and those will be on the rise now! It looks a lot like cow parsley and while the leaves and flowers are reasonably safe and often eaten by cattle, the roots from one plant are enough to kill an adult cow. An old ley term for it is Cowbane, understandably. The roots are swollen white tubers (see picture), giving it the other common name of Dead Man’s Fingers.

Dead Man’s Fingers, some call it Poison Parsnip!

Dead Man’s Fingers, some call it Poison Parsnip!

 

A final common invader of pastures will be overhanging oaks, the leaves and particularly acorns are toxic to the kidney which may cause a delayed problem after consumption. We often see this after a period of high winds bring down a crop of acorns and the animals suddenly show an interest in the bounty.

Away from ‘pasture plants’ another common factor in poisonings are garden plants, the prunings of which may be dumped over a hedge in good faith of giving the animals ‘a treat’ or by the more malicious fly tipper! Toxic plants we are generally well aware of include Yew, Rhododendron, Laburnum, Leylandii and the leaves of potato and rhubarb. Perhaps less well known are laurel and the wilted leaves of stoned fruit trees (plum, damson etc.) or Elder.

A final thought on toxic plants sometimes found in non-grass forage crops, I notice particularly in maize for some reason. I have commonly found Woody Nightshade (a climbing plant with clusters of green berries that ripen to red) and less commonly Black Nightshade (similar with black berries). Both cause inappetance and scour and are rarely lethal, luckily the Deadly Nightshade is only found on chalky soils so rarely in Devon and Cornwall! Perhaps one to be aware of in purchased feeds though.

For further information on Westpoint please contact our Launceston practice on 01566 86985.