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Video 38 Photosensitization in cattle

While it’s great to get cattle outdoors it is still time to be vigilant and watching animal health. While we all welcome sunlight it can be involved in a rare and sporadic disease in cattle. While sunlight is only part of this disease process it means that we need to be watching for it from April to October.

Photosensitization occurs when sunlight reacts with photodynamic agents in the skin. This will lead to the symptoms we often associate with the disease

The symptoms

While in the extreme this skin reaction causes skin sloughing. In most cases it can be very mild changes initially we need to watch for.

It typically will affect the white areas of skin or unpigmented areas like those around the nose, vulva, testes and udder.

These animals will present as uneasy, isolated from the group and often be swishing their tails. As the condition worsens they get very uncomfortable. On closer examination, they will be sensitive around certain areas. The skin can become thickened and sore to touch. They will often have high temperatures and can be in danger of aborting if pregnant. It can affect all age groups of cattle, my own experience was mostly in cattle in their second grazing season or older were affected.


In the latter stages and in more severe cases the skin can get flaky and slough off.


While the debate goes on about bringing animals indoors (out of UV light) I still think this is good advice. Especially in early cases of the disease. These animals really benefit from anti-inflammatories in fact they are the mainstay of the treatment.

In severe cases, topical skin emollients can be used on affected areas. However there is little research to their benefit, but from a practical perspective, they make sense.

It takes time for the symptoms to resolve often 2-4 weeks. Where skin becomes infected your vet may choose to use antibiotics. As a routine, all these cases could receive mineral drench or B vitamins.

At herd level I have heard of using zinc supplementation with multiple cases and only in the last two days heard of farmers using yeast. I could find no research for either of these but both have been reported to me. I could find no current clinical research for this but I must dig deeper to find out more.

The photodynamic agents

These are the agents when excess in the skin the UV (sunlight) reacts with. They can come from numerous sources particularly associated with some plants in the literature

The cases of photosensitization can be broken down into 4 categories

  • Primary ingestion of photodynamic agents through the gut or skin like St Johns Wort, some brassicas, and clovers. There are up to 15 plants said to be associated with this disease!
  • Idiopathic where no known cause can be found
  • Genetic with breeds such as limousines being reported, where defects occur in certain enzymes involved in the breakdown of heme.
  • Poor liver function or plant poisonings affecting liver function. This may be very relevant for farmers with liver fluke issues. Chlorophyll from grass is normally broken down in the liver and this process is disrupted leading to an increase in phylloerythrin (photodynamic agent).

With reasonably good outcomes in most cases except those with secondary liver problems. This is a disease we can recognize it quickly and treat early.

Where a large number of cases develop look at genetics and search fields for some of the plants involved.

My advice is to treat early and bring these animals indoors.


Thought for the day

It was the Italian scientist Paeredo who came up with the 80:20 rule. So focus on the things that will yield you the best results in life and work


Can you apply the Pareto Principle to Recruitment? - Aden Vaughan ...

Huge thanks to Nettex, Progiene, and Rumenco in their support for helping me make #50in50 http://www.net-tex.co.uk


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