Excellent BVD screening as just 0.3% untested

At end of January 2014, just 14,800 out of about 2.1 million calves registered in 2013 remained untested, in year one of the compulsory phase of the BVD eradication programme.

When calf deaths are taken into account, only 6,600 (0.3%) 2013-born calves are alive and untested.

Animal Health Ireland (AHI) says 0.8% of calves had a positive or inconclusive result in 2013, falling to 0.67% after negative confirmatory testing. Some 11.25% of herds tested in 2013 had one or more positives, with some 14,000 PIs identified. In February 2014, about 10,250 of these were recorded as dead, while 3,750 were still alive, in 2,500 herds (3% of breeding herds), based on data held on the Department of Agriculture’s Animal Identification and Move-ment System (AIMS).

Animal Health Ireland have expressed satisfaction with the first year of the compulsory phase, and revealed that in 2014, results for 373,000 calves show the numbers testing positive or inconclusive in the initial test has fallen to 0.44%, from 0.8% in 2013.

The rate of empty tags is also lower this year (0.87% compared to 1.16%), reflecting greater familiarity with the use of tissue tags. AHI said the almost immediate impact of the eradication programme on disease incidence became clear in the second half of 2013, with the incidence of PI births peaking at 1.21% at the end of July, but falling since then, with the lowest value, at 0.38%, recorded recently, in 2014. The downward trend is due to fact that the level of infection of unborn calves in early pregnancy started falling in January 2013.

However, PI calves being born now were created within the compulsory phase of the programme, which underlines the importance of key eradication measures in the programme — such as prompt testing of calves (and their dams where positive), prompt removal of PIs when identified, and wider herd investigations after positive results.

With the impending start of the breeding season for many herds, it is vital that as few PIs as possible remain on farms, advised AHI.

A recent analysis of results from herds that had PIs born in 2012 and again in 2013 clearly showed that the number of PIs born in 2013 rose in proportion with the length of time that 2012-born PIs were retained. It was found that nearly all the 30 herds that had six or more PIs born in 2013 still had a 2012-born PI alive in them at the time of the analysis.

A PI heifer or cow will always produce a PI calf. Testing of dams which produced PI calves in 2013 found 6.5% to be positive. Other calves were PI due to transient infection during early pregnancy.

Results for 2013 showed that about 620 herds had PIs born to animals that were in calf when introduced (Trojan animals). In 120 of these herds, the Trojans were returning to their birth herds, after being bred in another herd.

¦ New legislation will shortly prohibit untested calves born after January 1, 2013 from being moved to slaughter, according to AHI.

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