Dairy hoof study goes beyond Taranaki
return a single positive test last season. In his study’s first screening in September and October last year, there was no sign of the disease in 24 herds. ‘‘I was surprised they were negative because I’d expected the infection would get worse.’’
In the first study, the highest incidence of the disease was early in the season. Last season it was most apparent in the NovemberJanuary period. ‘‘So we want to figure out what’s going on because the first year the disease was more prevalent close to calving.’’
Last season different cows returned positive tests. ‘‘The infection in some cows disappeared and new infections appeared. Are certain cows more susceptible than others?’’
Overall, 3.2 per cent of almost 19,000 cows in the latest study showed a lesion - usually between the claws - at some point, significantly less than the rate of 40 to 60 per cent found in indoor dairy farming systems overseas. Although the prevalence was low, he was surprised half the cows with BDD had it on both their back feet.
Chesterton said hardly any of the infected cows were lame. ‘‘The lesions didn’t seem to be affecting the cows, so it’s hard to convince farmers to do anything.’’
Only three farms had footbaths at the cowshed entry and exit. ‘‘The prevalence of the disease fell on those farms, so footbaths are certainly part of the answer.’’
During the study infected feet were sprayed with antibiotic or treated with an antiseptic gel. The infection reappeared in some animals and not in others. ’’It will keep recurring in some cows because their immunity suppresses it without getting completely rid of it.’’
Overseas studies had shown vaccination was unsuccessful. Every farmer in the study completed a questionnaire.
Wang is still analysing the data, which also includes daily maximum and minimum air temperatures, soil temperature and rainfall recorded on a control farm.
His analysis is also exploring the use of feed pads, herd shelters, stand-off areas and whether palm kernel expeller is fed in paddocks. ‘‘We’re looking at any areas where cows could end up with dirty feet,’’ Chesterton said. ’’When feet are clean and healthy, it makes it harder for the bacteria to grow.’’
That theory was tested when the bacteria grew immediately after being applied to a cow’s foot that had been bound in a wet bandage. ’’They don’t grow on a dry, healthy foot.’’
He’s worried BDD bacteria could aggravate white line disease which also makes dairy cattle lame. Additionally, BDD bacteria had been found in front of a cow’s udder in England. ’’So we’re wondering how and why that happens.’’
BDD also occurred in beef cattle on beef farms or on lifestyle blocks, where it was much more difficult to detect and treat than on a dairy farm. In some countries the bacteria had been found in sheep, deer and goats.
Chesterton, who’s conducted seminars and written about BDD for the Society of Dairy Cattle Veterinarians, said New Zealand vets were far more aware of the disease in its early stages than those in other countries with pasture-based feed systems.
He’s encouraging farmers to screen their herds for the disease at least once this season. He’s also recommending a second test after seeing how the incidence varied during the season.
‘‘It’s easy for a farmer to do,’’ said Chesterton, who drew attention to instructions on his website, lamecow.co.nz which has up-to-date information about BDD and a video showing how to prevent it, how to screen animals for it, how to treat it and how to build a footbath.