Listeriosis

Listeriosis is a relatively common disease of ewes supplemented with silage. It is caused by a bacteria in the silage called Listeria monocytogenes which, when ingested by sheep, leads to microsabscessation of the brain stream.

It causes paralysis of nerves on one side of an animal’s face. It can be identified by an animal’s head tilting to one side, with its ear dropped downwards, or saliva coming from its mouth due to an inability to chew or swallow. Animals also propel themselves in one direction as a consequence of paralysis and appear to be circling.

Many flockowners believe bad quality silage being made, either through poor preservation or soil contamination, to be the root of the problem, but there are also other causes.

Air

When silage is exposed to air, it leads to a change in the pH and provides ideal conditions for Listeria monocytogenes to form and multiply. This can occur in bad pit face management or bad feed management, where troughs are not regularly cleaned and fresh silage is offered on top of old or uneaten silage that has spoiled and began to mould.

A regular feature in silage offered in ring feeders is too little sheep present to eat the bale quickly enough, or sheep not being able to reach the very inner core of the bale which spoils and is offered to ewes by falling over or being manually spread by farmers.

The success of treatment is dependent on early detection and includes antibiotics prescribed by a veterinary surgeon. High-energy glucose or glycerol supplements should also be given to prevent an associated energy deficit, dehydration or twin lamb disease.

Silage eye

As the name suggest, silage eye, or its veterinary term ocular listeriosis, is associated with feeding silage and affects the eyes of sheep and cattle.

The risk is increased where animals are eating mouldy silage. It is thought to be greatest where animals are eating from round feeders (burrow their head into the bale) or in windy conditions where there is a chance of silage being blown into animal’s eyes.

It can spread very quickly and affect a large percentage of the flock. Its symptoms are similar to ‘pink eye’, but it can be diagnosed by close inspection of the eye.

Symptoms

Affected sheep will often have their eyes closed, with swelling of the area around the eye being common. Excessive tear production will also give the area a distinctly wet look. It is a very painful condition and, if untreated, it can lead to blindness.

Veterinary advice includes your verteinary practitioner administrating injectons of antibiotics and anti-inflammatories into the tissue around the eyelid. It is vital to consult your vet before administering injectable anti-inflammatories, as they can lead to abortion if incorrectly administered.

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