Cow disease cause under debate
Livestock genetic companies are adamant their bull semen is not responsible for bringing in the disease Mycoplasma bovis, but former Federated Farmers president Dr William Rolleston says farmers need more proof.
He said until the semen and the donor bulls had been reliably tested as negative by the Ministry for Primary Industries (MPI) or an independent lab, the possibility of the disease entering New Zealand through semen ‘‘must remain open’’.
The disease, highly contagious within herds but not from farm to farm through airborne means, was detected for the first time in New Zealand last month on two farms owned by South Canterbury farmers Aad and Wilma van Leeuwen.
Mycoplasma bovis is in all of the world’s dairy countries. It does not infect humans and presented no food safety risk. There is no concern about consuming milk and milk products.
Some animals from the van Leeuwen properties have already been put down for animal welfare reasons, while others are being sent to freezing works for slaughter.
One of the world’s largest semen companies, US genetics firm World Wide Sires said it was ‘‘pleased MPI has confirmed there is no evidence that resistance has developed to Mycoplasma in imported bovine semen’’.
World Wide Sires New Zealand general manager, Hank Lina, said the company – along with other importers of bovine semen – had been working with MPI to isolate and identify the source of the outbreak.
‘‘We sell more than 19 million straws of semen to 80 countries around the world and, over several decades, have developed semen production and processing procedures which are amongst the most rigorous in the world,’’ Lina said in a statement.
Its research showed no evidence of Mycoplasma bovis was found in any of World Wide Sires’ 1700 bull team. The company also used a wide range of antibiotics as a secondary line of defence against contamination.
Rolleston, who farms in South Canterbury and runs a hi-tech animal blood products company, said his analysis was that the companies were admitting the risk of it coming in through imported semen was small but did not rule it out completely.
‘‘We have to keep an open mind on all pathways and MPI should not dismiss semen as a possible pathway until the semen/bulls have been tested negative to M. bovis. This is not a witch hunt it is simply going through the process in an objective manner,’’ Rolleston said.