While the death of 150 Southland cows has been linked to liver failure - it's only one piece of the puzzle.

Dairy New Zealand's conducted an initial autopsy on the cows that died in September.

It's believed hundreds fell ill after grazing on swedes, but the industry body says it's too soon to tell.

Southland team leader Richard Kyte says the next step is to survey around 120 farmers.

"Looking at those that had issues and those that didn't and comparing them.

"Comparing the management practices around how they managed animals on the crop, how much crop they've fed and how much supplement."

Kyte says they can't draw any final conclusions until they carry out more tests.

"Once the survey been analysed, we've also got plant samples being analysed starting in February, we're hoping that by the time we've got that altogether we'll have something to be able to tell farmers."

Results are expected next year.