Nitrogen poisoning has emerged as a possible cause of the sudden deaths of more than 120 cows on a south Taranaki dairy farm last week.
The cows dropped dead after drinking from water troughs that had been topped up from a 5000 litre tank that had been used to mix urea fertiliser.
The Primary Industries Ministry and local vets are still investigating the deaths.
But a family spokesperson, John Murphy, says nitrogen poisoning from the urea is a suspected cause, even though the container had been thoroughly rinsed out.
He says the tank was being used to top up stock water troughs because the mains supply wasn't keeping up with the increased demand from the cows.
Meanwhile, Mr Murphy says local farmers and some further afield have rallied around to supply replacement cows for those lost.
He says 80 cows have either been gifted or leased to the couple for the season, to help fill the gap left in their herd of about 600.