Many farmers will resist it fiercely, housing our dairy herd in sheds is almost inevitable.
The New Zealand dairy industry has always prided itself as being different. Whereas most other countries developed their dairy industries based on the housing of cows for much or all of the year, the New Zealand industry has always been pasture-based. The cows harvest the grass themselves, the cost of production has been low, and the image was of "clean and green".
Alas, we now know the image of "clean and green" was never quite true. Although a huge amount has been done to clean up the industry, with fencing of waterways, nutrient budgets and meticulous management of effluent from the milking shed, there is a fundamental problem still to be tackled. This fundamental problem is the concentration of nitrogen in the urine patches which grazing cows leave behind.
The dominant belief among scientists is that when a cow urinates it deposits nitrogen in the urine patch at up to 1000 kg per hectare. Not all of my animal scientist colleagues are convinced about this specific number, but regardless of the exact amount, it is inevitable that there will be significant nitrogen leaching from urine patches deposited in autumn and winter.
It does not matter what is done in terms of reduced stocking rate or reduced fertiliser or different grasses. As long as the cows are grazing the paddocks in autumn and winter, then there is going to be significant loss of nitrogen into waterways and underground aquifers.
There are four possible strategies.
Stand-off pads bring their own problems. There needs to be collection of all effluent and, without a roof over the pad, the effluent pond needs to be at least double the normal size. So in most cases, it means that there have to be roofed sheds.
The appropriate technologies are well understood in both Europe and the United States. Many European countries legislated decades ago to ensure that cows were held inside during winter, and that the effluent could only be taken back to the paddocks once the soils were drying-out in spring. We now have to adopt and adapt these same systems to work in the New Zealand environment.