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Be Vigilant for Maedi Visna
2012-09-04

When thinking about purchasing replacements and rams it is important to consider health status alongside genetic potential according to EBLEX.

photo © Jennifer MacKenzie

Texel lambs

This advice is particularly pertinent given that the results of an EBLEX and HCC-funded survey undertaken by SAC and AHVLA found that the number of flocks infected with Maedi Visna (MV) has doubled in a 15 year period, increasing from 1.4% to 2.8%. The number of infected sheep has increased four-fold, with the level of infection within affected flocks almost doubling during that time, from 13% to 24%. The survey is the first looking at the level of MV infection in the national flock since 1995.

Visible signs of MV are not usually seen until about half of the adult flock is infected. Signs are loss of body condition, poorer fertility, mastitis, increased twin lamb disease, smaller and weaker lambs born leading to increased mortality, lower volume of and poorer quality colostrum and milk, leading to reduced lamb growth rates.

There is no cure for MV and there is no vaccine to prevent or control it. Infection spreads through close contact so affected flocks that are intensively-managed tend to have more infected sheep. By the time that signs of infection are seen, usually years after the virus has been introduced, the infection has reached such a high level that it is very difficult to control.

Flock owners are advised to take the following actions when purchasing replacements and rams in order to avoid buying-in health problems.

Before purchase:

  • Wherever possible investigate the flock’s health status as fully as you can. Consider infectious abortions, lameness, wormer resistance, fluke, orf, scab, vaccination policy
  • Where possible, purchase stock from MV accredited flocks
  • Inspect the animals for any obvious signs of ill-health or previous treatments, e.g. foot trimming
  • Speak to the breeder about their breeding objectives: maternal ability, carcase traits, mature size
  • Use EBVs to select the right type of stock for your system
  • Ask how the stock have been fed, especially when buying rams. EBLEX has suggested that rams are most fit for purpose when the percentage of concentrates in their diet is less than 40% (as dry matter)

After purchase:

  • Inspect all sheep for any signs of disease before they are brought on farm
  • Quarantine all bought-in stock from the rest of the flock for at least three weeks to ensure treatments and routine vaccinations can be done, and monitor for any signs of disease

Copies of the final report on the survey are available by contacting EBLEX livestock scientist Dylan Laws on 024 7647 8892 or emailing dylan.laws@eblex.ahdb.org.uk

link Fall in Beef Production Forecast for 2012
link Sheep Sector Production to Continue to Rise in 2012 and 2013
link EBLEX Sets ‘Five Tonne Tup’ Target for Sheep Farmers

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