NEW ZEALAND - Scientists researching fatalities in New Zealand dairy cows grazing swedes are saying mild weather could be blamed on liver damage to cattle.
Forage swedes produced more leaf last year, prompting researchers to link liver damage with higher leaf consumption.
New Zealand dairy farmers across Southland reported dead cows in September last year.
After three months of farm interviews and plant and post mortem analysis, researchers linked the illness, which frequently gave similar disfigurations to facial eczema, to pre-toxins containing sulphur and consequent liver damage.
The condition seems close to other better known forms of liver damage linked to bovines grazing brassicas. In these instances, damage is linked to glucosinolates.
“There are over 120 individual glucosinolates," said Dawn Dalley, senior scientist at DairyNZ, the levy board overseeing the study. "These compounds are modified as they enter the cow’s rumen and all act differently, so finding those that specifically cause liver disease is difficult.
Diet information from farmer surveys will help understanding of cow rumen condition and the action of glucosinolates, she added.
“There could have been a higher level of glucosinolates in swedes this year – with the mild conditions, there’s been more leaf and the cows eating less bulb.
"Some farms had trouble with cows not eating the bulbs and gave bigger breaks to compensate, which might mean more leaf eaten.”
When first alerted, no accredited laboratory in New Zealand existed to analyse the plant samples, although the “method is being developed now”, said Dairy New Zealand.
Preliminary results will be released as they become available to a working group including government ministers, the New Zealand Veterinary Association, local veterinarians, Beef and Lamb New Zealand, Federated Farmers, the Rural Support Trust and PGG Wrightson Seeds.
A final report will be released in the autumn.