This paper presents preliminary results from a 5-year study aimed at generating objective data on the effect of subclinical Johne`s disease on productivity in sheep. On two properties where Johne`s disease was considered to be a problem, replacement ewe lambs from a single generation were allocated to one of three groups. One group was vaccinated with the killed Mycobacterium avium subsp. paratuberculosis vaccine Neoparasec, another with the live vaccine Gudair, and the other group remained as unvaccinated controls. The vaccinated and control ewes were monitored over the ensuing four years for the following parameters: lesion size, live weight, fleece weight, scanning percentage, lamb production and weight of lambs weaned per ewe. Serology was also performed on a sample of animals from each group. On one property, the size vaccination-site lesions associated with Gudair declined at a more rapid rate than those associated with Neoparasec. However, results to date have failed to detect a significant difference in productivity between vaccinated and unvaccinated ewes in either flock, suggesting that subclinical Johne`s disease may not be an important cause of production loss in sheep. The trial is now in its final year.

KG, Thompson, DM West, PVA Anderson, and DL Burnham

Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 284-287, 2002
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