How to prevent pneumonia in lambs at weaning

Minimising the time lambs spend in yards, avoiding shearing lambs at weaning and maintaining small mob sizes when yarding lambs have all been found to reduce the incidence of Chronic Non-Progressive Pneumonia (CNP). This is the most common form of pneumonia in lambs and can lead to pleurisy where lungs are stuck to the chest wall. Affected carcasses are downgraded or condemned at processing.

Caused by bacteria, mycobacteria, or viruses, CNP can cost farmers due to downgraded carcasses and reduced lamb growth rates.

In case study of a mob of 500 lambs with a typical level of pneumonia, estimated costs due to downgraded carcasses were $2,920 (at a $6.63 schedule) or $5.80/head.

Significantly affected lambs can grow 50% slower than unaffected lambs. If lambs with CNP grow at 75g/day rather than 150g/day, then it will take them an extra 47 days to grow from 30 kgLW to 37 kgLW. This would require an additional 66 kgDM.

Studies by both Massey University and AgResearch have shown that the prevalence of lambs with CNP at slaughter ranges significantly between flocks and years, but on average flocks have 20–30% of lambs affected.

Other on-farm management factors that may be linked to pneumonia include breeding ewe replacements (lambs spend more time in yards) and contact with other flocks through the purchase of other lambs post-weaning.

It is recommended that farmers try and reduce the extent and duration of open mouth panting when moving lambs. Ways to do this include using satellite yards and utilising laneways to allow lambs to drift along at their own pace and targeting cooler days or cooler parts of the day.

Other suggested risk factors of CNP, which are largely anecdotal, include high temperatures and humidity, crowding, stress, dust, excessive exercise, poor ventilation, low immunity and high parasite loadings.

Sheep with CNP often have sub-clinical symptoms such as reduced growth rates, but affected sheep will often have trouble breathing and pant following exercise and cough.

The best prevention strategy is to ensure animals are well-fed, are up-to-date with animal health treatments and have minimal stressors (especially exercise and yarding stress).

Ewes in good body condition will grow their lambs as fast as possible to weaning, meaning more lambs are sold at the weaning draft and therefore have less exposure to CNP-causing bacteria or viruses. Those that do remain have well developed immune systems.

Tackling CNP

• On average, Chronic Non-Progressive Pneumonia (CNP) affects 20-30% of lambs in a flock.
• CNP can cause significant economic losses.
• Avoiding shearing at weaning.
• Maintain small mob sizes when yarding lambs.
• Avoid moving lambs long distances under pressure.
• Good nutrition for ewes and lambs will help prevent CNP.