Rain will bring deluge of challenges

DairyNZ warns rain will rot pasture, leaving cows underfed and give rise to facial eczema. Farmers will need at least three weeks of supplements (100kgDM/cow) to feed out after rain, or on very dry farms up to 160kgDM/cow.

DairyNZ ‘Beat the Heat’ fieldays are helping farmers deal with the drought and preparing them for the post-drought period. Marketing manager productivity Warren Twohey says turnout to the fieldays has been good. About 100 farmers attended days AgResearch’s Tokanui Research Farm in Te Awamutu last week, 100 in Gordonton and 70 in Morrinsville.

The events give farmers confidence to make key decisions as they face prolonged dry weather, Twohey says. “It also gives them opportunity to talk to fellow farmers and get an understanding of how their neighbours are dealing with the drought,” he told Rural News.

He points out problems don’t end when the rains arrive. “When it starts raining, it doesn’t mean everything is hunky-dory. It could be two to three weeks before grass starts growing.” So supplements are essential. 

DairyNZ says past experience shows this ‘rot down’ time is when cows are most underfed during a drought. “As pasture can halve after rain, cows can be severely underfed and will require 50-75% of their intake from supplement. If feeding out before the drought, the amount required after rain will at least double in the first 7-10 days, reducing as pasture cover improves.”

Pasture management is also critical when the autumn rain arrives.  After autumn rain and very rapid grass growth, slow herd rotation will keep pasture cover high. But it warns not to speed the rotation to fully feed the herd, as this will hinder pasture growth.

The rains will also bring animal health problems such as facial eczema. Maintaining a low zinc dosage is then worthwhile. “When the rain does come, spore counts are likely to rise dramatically and by maintaining a low zinc dosage the cows are already adapted to zinc should zinc dosages need to be lifted.”

Farmers are also advised to go easy on copper supplementation, especially if the cows are fed PKE. If feeding out PKE, mind the impact this may have on copper levels in the cow’s liver. “Avoid routine copper supplementation for cows fed PKE in large amounts over long periods without checking the cows copper status first.”

With cull cows being sent to the works now is a good time to monitor copper status via liver biopsies to ensure copper is within acceptable limits.