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Cost of Johnes' disease in sheep revealed

New research part-funded by Meat New Zealand has for the first time measured the effects of the debilitating Johnes' disease that costs the New Zealand sheep industry around $6 million a year in lost productivity. The data will allow accurate evaluation of methods of controlling the disease.

Neil Clarke, General Manager of R&D at Meat New Zealand, said:

"Now that we have measured both subclinical and clinical effects in New Zealand field conditions, we can use that as a benchmark to test out ways of controlling the disease."

The seven-year trial, funded by Meat New Zealand and the Wool Board with AgResearch, showed that clinical Johnes' reduced a ewe's average weaned lamb weight from 45.9kg to 24.9kg, a massive 46% drop. With subclinical Johnes', which is harder to detect but still causes significant productivity losses, the loss was half that, at 17%, with average weaned lamb weight of 37.9kg. The incidence of Johnes' disease in 3-7 year old ewes was up to 1.4% in the trial flock.

The effects on fleece weight loss were also measured, with clinical Johnes' causing 15% loss, and subclinical 10%. In dairy cattle, subclinical Johnes' is known to reduce milk production by 20%.

Clarke said: "If we find a way to suppress Johnes' to keep it at the subclinical level, or prevent it outright, we can compare the cost of the treatment with the gains in productivity, and work out whether overall it will save farmers money."

Meat New Zealand is funding the early stages of developing a sheep and cattle vaccine for Johnes' disease, at Massey University.

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