Treatment & prevention of photosensitisation in cattle?

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Hi All,

 

Have any of you FIRST-HAND experience of treating / preventing

photosensitisation (PS) in large groups of cattle at pasture? What

do you advise your clients to do to treat/prevent PS?

 

Note that regular individual dosing is NOT an option but group

medication and/or water medication, and/or slow-release boluses

may be practical options for our farmers.

 

PS may affect 5-30% of cattle at pasture. Usually the white/light-

coloured skin is affected, but one report mentions PS in BLACK

Limousin cattle, mainly in the periorbital area. However, IMO, if the

light intensity is high enough, it may be possible that dark-skinned

areas may show minor signs also.

 

Some PS-affected cattle suffer terribly; they develop dermatitic

eczema, baldness, oedema, pain, sepsis of the affected areas, and

fail to thrive. Some may even die of shock or generalised infection

in severe cases.

 

Any factor that causes liver damage, or stresses liver

metabolic/detoxification function can increase the risk of PS.

Triggers include chemical, plant or fungal toxins, some drugs (like

phenothiazine, etc), hypericin, sporodesmin, pyrrolizidine alkaloids

etc.

 

See ABLD (Acute Bovine Liver Disease), a new disease of

unknown aetiology: http://tinyurl.com/2vvsr

 

For good articles on PS see:

http://tinyurl.com/yu2uo and

http://www.agric.nsw.gov.au/reader/an-health/a0938.htm

 

Best regards,

Phil

 

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Philip Breslin wrote:

> At around this time of year and for the rest of the summer we get,

> on our own farm, cases of photosensitisation (PS). It is typified

> by pain, weakness, depression and occasionally, oedema (especially

> peri-orbital). Animals often appear to be asleep and are difficult

> to rise. I suspect that this is a function of pain. Thickened skin

> is not always present. We have seen this presentation in black

> animals over the years and we have one case now. These blacks are

> usually of limousin type rather than angus. There is no raised

> temperature and little or no thickening of skin. They recover

> after a few days in a (completely) dark stable and will relapse

> when exposed to light (even in cloudy weather). It only occurs on

> one of four outfarms but I am not able to recognise the offending

> plants (However, a colleague has offered his services). Is this

> photosensitisation? Has anybody else seen it or suspected it in

> black animals as it is usually associated with light-coloured

> animals? It would be quite difficult to diagnose without the herd /

> land history. Regards Philip

 

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Best regards,

 

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