Jess Rayner
Pneumonia in lambs can be easily overlooked as it can in chronic cases, just look like lambs that are a bit ill-thrifty.
In reality there is a large cost , either in reduction of lambs’ body weight causing them to go to slaughter lighter or stay on farm longer – or carcass condemnation or wastage trimming at the abattoir due to pleurisy in the lungs.
This it makes it extremely important to understand the symptoms, causes and the best methods of preventing lambs from developing pneumonia in the first place.
Reduced weight gain is one of the most common signs of chronic pneumonia.
You may also see coughing when the lambs are in a group as well as nasal discharge.
It is important to keep an eye on kill sheets from the slaughterhouse which will often report if there are increased pleural lesions in the lungs of the animals, or if the carcasses have been downgraded for any reason, which could also indicate chronic pneumonia.
Acute pneumonia will start appearing within a fortnight of a stressful event. Normally it is sudden deaths, with losses sometimes reaching up to 2-8%.
Sporadic deaths can continue for several months after.
In milder cases, lambs will sit down during droving and fail to recover.
The best way to get a proper diagnosis on whether lambs are dying due to acute pneumonia is to perform a post-mortem, which can be done by a vet, or yourself on farm.
You are looking for unresolved abscesses in the lungs, some which may have burst into the chest cavity itself.
Prevention is better than any cure. Practices that have been flagged as most likely to be associated with higher numbers of lambs with pneumonia at slaughter include:
• Shearing lambs on the day of weaning.
• Breeding replacement ewes on farm, and increasing the age of lambs before they are sent off to slaughter.
These practises allow good environments for the bacteria to spread among the flock and breed in the lungs.
Managing heat stress is also an important factor. Heat stress can be seen when lambs are mustered over long distances in the heat causing open-mouth breathing or panting.
It can also be worsened due to: dusty conditions, excessive use of dogs, and a lack of shade in the yards.
Using covered yards to ensure shade, or even portable yards to reduce distance travelled on hot days can help.
Ensuring mustering yards are concrete to reduce dust, mustering on sealed roads and using sprinkler systems to reduce dust can also help minimise the risk of pneumonia in lambs.
Keeping animals on farm longer and in close proximity to each other, or in overcrowded conditions for an extended period of time in mustering yards, increases the risk of spreading the disease from animal to animal.
Hot environments or animals experiencing heat stress will also be at increased risk due to the panting and increased breathing.
The available vaccine has minimal efficacy in New Zealand due to the multiple different strains of bacteria that cause pneumonia in lambs.
Treatment by oxytetracycline has been shown to be beneficial if it is an acute issue, and the animal is a high value animal. Treatment with procaine penicillin is now frowned upon as it will likely cause the bugs to develop resistance to the penicillin and cause more of an issue in the long run.
In chronic cases, the important thing is to separate animals showing signs of pneumonia from otherwise healthy animals.
Afterwards moving healthy animals to a larger paddock where they have room to spread out has been shown to have good results as it minimises contact between animals and lessens the chance for bugs to spread from animal to animal.
If you are worried about your flock or wish to discuss any of the prevention or treatment methods discussed in this article, get in touch with your vet.
