Archived News

6th July 2009

Hooray!  It’s raining at last!  Just what our crops needed.

The forecast was for rain by midday, but it seemed to have passed us by, with people from all about the south east saying how much rain they’d had.  Well finally, at 6.30pm we are having a few showers and much needed they are too.

Everything hinges on the weather in farming; it is so relevant to crop quality, level of yield, enough grass for cattle, success or failure, life or death. 

Some years ago, working on the North Downs during summer, blisters formed on my skin, similar to a burn. I later discovered that my skin had reacted to the sap of Wild Parsnip in the sunlight. The sap of at least thirty wild and cultivated plants including parsnip tops, parsley, celery tops and giant hogweed contains substances (furocoumarins) which , in contact with bare skin, enhance the skin's sensitivity to the ultra violet rays in direct sunlight.

I have been amazed to hear that cattle can suffer from a similar condition, with sunlight being a recent link to sickness in year old Belted Galloway heifer.

The heifer was born with a small growth on its umbilical cord which was not diagnosed. It has never appeared to grow in stature as with other Beltie calves and the calf recently began to lose its coat, but only within the white belt. 

A vet diagnosed photosensitisation which is not very common in cattle in The UK. It is an ailment in which the skin becomes abnormally sensitive to bright sunlight.

Primary photosensitisation occurs when a chemical comes from a defect in the animal’s metabolism of its red blood cells, or more commonly from plants such as St.John’s Wort.

St John’s Wort is a plant with glands on its leaves, stems and petals containing the light sensitive compound hypericin.  If enough compound accumulates in blood vessels at the surface of exposed skin, sunlight transforms it into a toxin and skin damage results.

Secondary photosensitisation occurs in animals with liver damage. This damage interferes with the complete breakdown of chlorophyll, resulting in the accumulation of a photosensitive chemical.

The green pigment chlorophyll in plants is metabolised in the animal to a light sensitive compound phylloerythrin.  The liver excretes phylloerythrin in bile to the intestine.  When the liver is damaged, phylloerythrin cannot be excreted and it builds up in the bloodstream.  If high enough levels of phylloerythrin are present in the blood vessels at the surface of exposed skin, sunlight transforms the phylloerythrin into a toxin which severely damages the skin.

Local photosensitivity can also result as a reaction to the sap of some plants.

As her coat began to shed, the heifer was moved into the shelter of a barn and she began a course of treatment. When I saw her on Wednesday, she had lost large areas of fur and her skin and flesh were now exposed, as is the nature of this condition. She was in a sorry state and sadly there was no doubt that she had to be put to sleep.  I hope we don’t see this condition again.