The hidden cost of pneumonia in Australian lambs

New research by our team has revealed that pneumonia might be much more common in Australian lambs than previously recognized and that it may be resulting in substantial financial penalties for the industry.

Pneumonia in sheep is a complex disease that often involves the interaction of one or more respiratory pathogens, host factors and environmental conditions. Adverse weather conditions and stress (i.e. poor nutrition, weaning, shearing at the same time as weaning) can act as trigger factors that allow infectious microorganisms to cause pneumonia.

Pleurisy, inflammation of the membrane that covers the outer surface of the lungs and the inside of the ribcage, often develops secondary to pneumonia. In lambs that have recovered from acute pneumonia/pleurisy, scar tissue can fuse the pleura covering the lungs to the pleura lining the inside of ribcage. This fusing of the lungs to the ribs makes it difficult for abattoirs to process the carcass of a lamb that has had pneumonia.

Dr Lloyd examined 227 lines of lambs representing 35,839 carcasses at a large sheep abattoir in southern Australia for the prevalence of pleurisy. Pleurisy was present in 115 of the 227 lines (50.7 per cent) and 334 of the 35,389 carcasses (0.9 per cent) examined. The average prevalence of pleurisy within affected lines was 2.2 per cent (range 0.2-12.2 per cent).

Pleurisy trim weight data were collected on 101 carcasses. Thirty-three of the carcasses (32.7%) had the pleura stripped with no rib removal. Thirteen carcasses (12.9%) had approximately one-quarter of the rib cage removed, 49 (48.5%) had half the rib cage removed and six had three-quarters (one carcase) or the full ribcage (five carcasses) removed.

The average trim weight when ribs were removed was 1.0 kg (one-quarter of the rib cage 0.50 kg, one-half the rib cage 1.0 kg, three-quarter to the full rib cage 1.9 kg).

The average trim weight including the carcasses from which only the pleura was removed was 0.7 kg (with the weight of the stripped pleura assumed to be zero).

Region and age, but not breed (Merino, Crossbred or Dorper), were significant risk factors for pleurisy, with lambs more likely to be affected than young lambs.

We estimate that trimming for pleurisy results in a $6 penalty per carcass to producers and an $8-10 loss per kilo in high value cuts (i.e. ‘frenched’ racks) to the processing sector.

Starting in August 2017, our team will again be in abattoirs collecting data on pneumonia in Australian lambs, with the aim of uncovering the primary pathogens responsible for the condition. Please contact us if you would like more information.