If you notice coughing in a large proportion of your lambs, or if you have more pleurisy listed on kill sheets, you are not alone.
Pneumonia (Ovine pneumonia (or “viral pneumonia”) is detected in an average of 28% of lambs’ lungs at slaughter but rates can vary greatly, affecting 6%-80% of animals in each line.
The most severely affected (an estimated 7% of lambs) take an average growth rate check of more than 50 grams per day.
Animals which develop pleurisy (resulting from severe pneumonia) will have adhesions in the rib cage for life, compromising them for the rest of it.
Pneumonia in lambs and hoggets is a multi-factorial disease involving both pathogens and external factors such as stress, environmental changes and concurrent disease.
In acute cases, sheep may be found dead, or found lagging behind the mob displaying signs of respiratory distress.
In groups of young sheep where pneumonia has developed, many sheep may be seen or heard coughing, and some may develop chronic ill thrift.
"Ovine pneumonia is detected in an average of 28% of lambs’ lungs at slaughter."
While the viruses (like parainfluenza) and bacteria (like Manheimia haemolytica) which cause
pneumonia circulate in all populations of sheep year-round, environmental and animal risk factors come together mainly in the summer months to trigger clinical disease.
Poor summer feed quality, heat stress (including high humidity, long musters, dusty yards),
shearing lambs on the day of weaning, purchasing and mixing different groups of lambs and
transporting them have all been shown to increase the risk of pneumonia.
Stress, whether it be from mustering, yarding, drenching or changes in feed, contribute greatly to the development of pneumonia, and the ability of the lamb or hogget to fight the disease without developing chronic damage to the lungs.
In the absence of specific preventative measures, you can minimise pneumonia by addressing risk factors. Strategies could include:
Muster during cooler times of day
Concreting or covering yards to minimise dust and provide shade during yarding
Delay shearing lambs until after weaning
Provide good quality feed to lambs over late summer
Avoiding yarding for long periods in close confinement
If lambs are already coughing make sure you don’t push mobs too hard; if you see lambs open-mouth panting you are increasing the risk for them to run into problems.
Preventing/controlling other diseases such as facial eczema, endophyte toxicity (staggers),
and Haemonchus (barber’s pole), all of which put lambs under increased stress during the late summer/autumn will help the lamb to better deal with an infection as well.