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• Blackleg

Blackleg

There are five clostridial diseases which can affect livestock:

blackleg, pulpy kidney, tetanus, black disease and malignant oedema.

The most common of these in this farming district is blackleg and given this season's unusual climatic conditions, all young unvaccinated cattle are particularly susceptible over the coming months.  Correct vaccination in terms of timing, dosage, injection technique and vaccine storage are all important in minimising the chance of losing animals to these largely preventable diseases.

The blackleg bacteria survive in soil as spores and prefer warm environmental conditions.  The spores are ingested as the stock graze, and pass via the blood stream to various body tissues, such as muscle.

The spores lie dormant in such tissues until local trauma causes the bacteria to proliferate and produce a toxin responsible for clinical disease.

We usually see blackleg in stock aged from 3 months to 2 years of age but sometimes as early as 3 weeks, with the largest and apparently healthiest animals being affected first.  Most are found dead after a short period (12-36 hours) of depression, upper hind limb swelling and severe lameness.  It is not uncommon for 10-20% of a group to be affected, although in outbreaks this may approach 50% - imposing a significant financial loss.

Treatment of blackleg is based on high doses of penicillin, but unfortunately unless treatment begins within the first few hours the response is generally poor.  In face of an outbreak of blackleg, treatment may also involve immediate vaccination and/or treatment of normal animals with penicillin as a preventative measure.

The other four clostridial diseases are seldom seen in this district but all have been reported on the rare occasion.

Blackleg vaccination is included in both 5 in 1 and 7 in 1 (with lepto) products and is a cheap and very effective means of preventing this and the other clostridial diseases.  Ideally three shots should be given.  The first at weaning, the second 4-6 weeks later and the third twelve months later.  Adequate protection is not gained in calves until two weeks after the second injection.

It is important the vaccine is kept refrigerated, and that you inject the correct volume (2 or 2.5ml depending on the particular vaccine) using a well calibrated vaccine gun.  All vaccines should be injected under the skin on the side of the neck.

As milk prices fall it is very tempting to minimise costs by not vaccinating your stock,  however the cost of the vaccine is minimal compared with other farm expenses, not to mention the time and effort you have already put into rearing your calves.