Diagnostic scheme provides points for discussion

With the most recent DairyCheck and BeefCheck data showing yet another rise in the number of herds testing positive for BVD and IBR, it’s a timely reminder of the value of these Intervet-subsidised schemes.

Even in the absence of clinical signs, regular testing is simple, free and a good way to get on to farms to discuss herd health planning, says Intervet’s large animal veterinary adviser, Rosemary Booth.

She reports that data from January to November 2007 (see tables) reveals 90% of tested dairy herds were positive for BVD and 70% for IBR. Of the beef cattle tested for BVD, 37.6% had a positive titre of more than 50; whereas for IBR, 32.7% had a positive titre more than 2. 

“Remember that testing simply provides a quick snapshot but, while most people put up with endemic diseases, clients don’t have to spend a lot of money to establish their herd’s BVD and IBR status. This is a good tool for discussion and a useful starting point. From there it can lead to further investigations and practical, effective advice on the benefits of a full testing and eradication programme,” she says.

The problem with IBR is that it can be hard to spot and therefore quantify. Explaining the impact on a unit is also notoriously difficult. Some herds may see stock that is just a bit under the weather while others might not see any symptoms at all. At the other end of the spectrum an IBR breakdown can have devastating consequences. Dairy cows with IBR infections, however, are more likely to have other problems, adds Miss Booth. “Our investigations have also shown that BVD virus is clever at survival and can stay in a herd for more than 10 years.  Long-lasting infection leads to underlying poor performance.”

She reports that some herds in the scheme are obviously tested more than once a year.  Regular testing gives a benchmark from which to detect health problems should they arise. “Monitoring is a good idea, even if you think that a herd doesn’t have a problem. Further tests can confirm whether infection is still circulating.

“When tests reveal high titres in the absence of clinical signs, it’s a good idea to monitor youngstock and find out when they are sero-converting. Remember that a high titre indicates that infection is probably fairly recent.”

BeefCheck results

January to November 2007

Total no. herds tested BVD = 225

Total no. animals tested BVD = 1349

BVD positive titre >2 = 60.1%

BVD positive titre >50 = 37.6%          

Total no. herds tested for IBR = 170

Total no. animals tested IBR = 1016

IBR positive titre >2 = 32.7%

IBR positive titre >50 = 12.2%

DairyCheck results

January to November 2007

Total no. herds tested BVD 543

Positive = 89.7%

BVD positive titre >2 = 23%

BVD positive titre >50 = 66.7%

Total no. herds tested IBR 632

Positive = 70%

IBR positive titre >2 = 36.4%

IBR positive titre >50 = 34%

The above data is represented graphically here.