He showed dairy farmers a chart of what he described as the sweet spot; pasture covers between 2100kg and 2300kg drymatter (DM) a hectare.
“That should be your average cover through the year as much as possible,” he said.
Farmers were missing out on growth of 4-5kg DM/ha/day if pastures were at 1800-1900kg DM/ha.
Flood, who has farms at Ruawai and further north of Dargaville near the Kai Iwi lakes, said 15% of the feed value of grass came from the first leaf stage, 35% from the second and 50% from the third. But it took a cow 50% of their time to get that energy from the first leaf stage, 35% for the second leaf stage and 15% for the third leaf.
“So the 2100-2300kg DM/ha can be varied a bit but you want to keep it within that sweet spot,” he said.
Flood explained how a line could be drawn to reduce from an 80-day round at planned start of calving to a 20-day round at balance date. For a 100ha farm this meant starting off grazing 1.25ha/day, increasing to 2.4ha/day by August 20 and 5ha/day by balance date of September 20.
Farmers could use DairyNZ or LIC programmes to draw such a graph or make up their own one to monitor progress on their own farm and avoid blowouts.
“In dry conditions you can get into credit and go out to the right of the line,” he said.
But if it was wet and cows couldn’t graze their allotted pasture a flat line could be the result.
“Then you get into a death spiral.”
Flood said the key to farmers knowing where they were was to platemeter every week or 10 days.
“Keep it alive so you know what you’re growing and follow the line down,” he said.
If it was really dry in the first week of September, as it usually was at NARF, just north of Dargaville, or at Ruawai he suggested adjusting the line. With farm working expenses on his farms averaging $2.50 to $3/kg milksolids he said it was business as usual this season.
“If I need supplement I’ll get supplement,” he said.
On one of his farms he would use the yard to stand cows off if it was really wet or take late calvers off the property.
“You’ve got to do something,” he said.
“When I’m below the line I get nervous but when I’m above that’s money in the bank.”
DairyNZ’s principal scientist, animal science, Dr John Roche, said farmers could manage their cows through winter and spring without purchased feeds by ensuring their stocking rate, pasture cover and crop yields and cow body condition score were correct at the start of calving.
Then the spring rotation planner would dictate the area to be fed daily giving the benefits of minimising a feed deficit in early lactation and ensuring cows were well fed and on a rising plane of nutrition before mating.
Shortening the grazing rotation during a winter or early spring deficit to increase the herd’s DM intake would increase the length and severity of the feed deficit as well as increase the need for bought-in feed and increase the cost of production.
Research at Ruakura Research Station in 1986 comparing maintenance of a slow rotation with increasing pasture allocated to ensure cows were well fed showed that in the second case average pasture cover declined and didn’t return to optimum until December. For a 100ha farm the difference in pasture availability was 500 tonnes DM/cow at a stocking rate of three cows/ha for those four months. With a cost of $200/t DM that added up to more than $35,000/year.
To grow as much grass as possible he said farmers should delay grazing as much as they could, feeding their feed wedge, not their cows.
“For every extra day of rotation you can grow 200kg DM/ha,” he said.
There was only a small drop in pasture quality between the first and fourth leaf stages but it was good to aim to keep grazing between the second and third leaf stages, where grass hits its reproductive phase.
In wet weather it was important to protect soils and pasture cover.
“Pugging damage has got to be avoided as much as possible,” he said.
On-off grazing and standing cows off for periods was preferable to offering a greater grazing area because cows could eat 80-90% of what they were going to within two to three hours.
“This can’t always be achieved but increasing the area offered should be limited to only a few days during winter and spring.”
