"Generally, for the North Island, we know that in dry summers, March 20 is the date by which we need substantial rain before farmers would need to dry off all cows to secure pasture and cow condition targets for the next season."
He says it is good for farmers to keep some of their cows milking until that date to maintain their milk income at a reasonable level and to have the option of having cows in milk should grass growth accelerate after good rainfall.
"Options include a combination of selective culling, possibly milking once a day or every 16 hours and buying in or using their own supplementary feed."
He says this still makes economic sense as there is some reasonably priced feed (less than 30c/kg of dry matter landed on farm) about for farmers to buy in to keep cows milking profitably.
"This latest rain will give crops like maize and turnips an extra growth boost so we're advising farmers to keep growing their crops, too, rather than feed it early to their cows. This will maximise the benefit of that rain we've had. And where substantial rain has fallen, say greater than 50ml, then it is worth applying nitrogen fertiliser."
Craig McBeth says making the calculations for feed planning is always an individual call. Farmers facing the driest conditions in Canterbury, North Otago and the Wairarapa are in a more advanced and challenging situation.
He says farmers need a lot more rain to get soil moisture levels back to normal.
"Farmers have to make the calculations and judgment calls now about how much grass growth we can expect in the next two to three weeks.
"They will need to make their own individual decisions about how to balance feed supply and feed demand. Factors to weigh up include costs and how many cows to keep milking and how often. With a bit of moisture around, they will also need to keep an eye on spore counts to manage the risk of facial eczema too."
DairyNZ advice and guidance on feed planning and summer management is available on www.dairynz.co.nz and at DairyNZ discussion groups.