Ministry to probe mystery cow deaths

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The Ministry for Primary Industries (MPI) said it was working with the dairy industry to find out the cause of more than 200 cow deaths throughout Southland early this month.

An investigation into the deaths is being being carried out by DairyNZ in conjunction with the company producing and supplying the product --- PGG Wrightson.

"MPI is working with industry to ensure appropriate testing and monitoring is occurring and that a full and thorough investigation is undertaken," the ministry said in a statement.

MPI was formally notified on September 3 of a potential association of a feed product - brassica swede crops - with an animal health issue.

The situation was discovered following a number of cases of cows becoming ill, and in some cases dying, while grazing on swede crops across Southland.

An initial assessment undertaken by MPI supported industry's view that the most likely cause of the deaths is due to swedes used as animal feed having higher than usual levels of glucosinolates.

Glucosinolates are a naturally occurring substance in the brassica species, which are important animal feed ingredients and are also a common part of the human diet and are naturally present in cauliflower, cabbages, broccoli and brussels sprouts.

"The exact cause is yet to be determined but at this stage it is believed to have been caused by mild weather characterised by lack of frosts in the lower central regions," MPI said in a statement.

The crops in question are specifically grown for animal feeds and are not considered a variety suitable for human consumption.

Swedes form a big part of many farm feed plans and farmers want answers before planting next winter's crops.

DairyNZ, a farmers industry group, is advising farmers who feeding swedes to cows to look out for signs of photosensitivity and weight loss in their herds.