In Waikato these cows have averaged 13kg milksolids (MS) more than low-residual cows. But when the cost of the 150kg of palm kernel they were fed until October 30 was factored in they were just $7/cow ahead of their pasture-only, lower-residual counterparts.
In Taranaki the milksolids response wasn’t as great, with just 3kg MS/cow extra being achieved by the high residual herd, which was fed 85kg of palm kernel. That put the target residual herd ahead by $4/cow.
DairyNZ farm systems specialist Chris Glassey said it would be interesting to see whether the difference was maintained through summer and into autumn.
“My feeling is the gap will close and if there’s a drought in Waikato that could make all the difference,” he said.
The purpose of the demonstration was to look at the effect of high residuals or the impact of achieving target residuals of 1500kg drymatter (DM)/ha compared with those 300kg DM/ha higher.
It builds on work done by DairyNZ developer, feed and farm systems, Sean McCarthy, which looked at nine farms, seven in the lower North Island and two in Canterbury. It found 49% of paddocks were grazed before optimum ryegrass growth, and 62% after the recommended 2600-3200kg DM/ha pre-grazing level.
Farmers missed the post-grazing residuals target in 48% of paddocks.
“Grass and money was being left in the paddock, which meant it wasn’t in the bank,” Glassey said.
Modelling on a whole-farm basis showed at the current payout forecast farmers who weren’t achieving targets could have been missing out on around $400/ha profit/year.
“And that could easily be $600/ha/year with a higher milk price,” he said.
The demonstration was being carried out by DairyNZ at two locations, Scott Farm in Waikato and the Westpac Taranaki Agricultural Research Station (TARS) near Hawera. They were set up and started operating on July 20 and 27 with pasture residuals differentiated from August 28. The herds were on 24-hour breaks with a four-week rotation so at the end of the first week in November pastures were getting their third differentiated grazing. While the 1500kg DM/ha residual cows were receiving no supplements the high residual herds were being fed up to 3kg/cow/day of palm kernel.
Scott Farm has two farmlets, each of 7ha with 14 paddocks, with two herds of 21 cows stocked at three cows/ha each.
The project was being led by DairyNZ senior scientist Kevin Macdonald, Glassey and senior research technician, Chris Roach.
The herds were selected to be very similar to each other by being split in two before the demonstration began and then balanced according to their Breeding Worth, age and calving date. They have had almost equal mean calving dates and are a similar age profile, ranging from two to 10 years old.
The pastures were all ryegrass and white clover mix with a variety of different cultivars included, and there was no recent pasture renovation history. Soil tests were done every year and show high phosphate levels.
Nitrogen went on after the cows had grazed the paddocks according to feed budget requirements.
Each herd had three paddocks of silage made and later in the season other supplements would be considered based on their cost and value. Glassey said because of the demonstration’s aim of differentiating pastures to gauge the impact on summer and autumn milk production and profit, use of supplements could be a problem.
“It could hide some of the differences in the pastures but we will need to work that out,” he said.
Every Tuesday morning those involved in the demonstration do a visual assessment of the farmlets’ paddocks and pasture cuts were also taken of 10 0.2m2 quadrats. Six of these cuts were of pre-grazing paddocks, which have averaged between 2900 and 3200kg DM/ha, and four of post-grazing pasture.
“The average we’ve achieved so far is a 200kg DM/ha difference in grazing residuals,” Glassey said.
A couple of factors were involved. Firstly the cows on the high residual have always been offered sufficient feed to keep them above 1800kg DM/ha.
“And staying at 1500kg DM/ha at this time of year (Nov) is hard with stem growth in the pastures,” he said.
The result was that the low residual herd were taking levels down to just 1700kg DM/ha while the higher target herd was reaching 1900kg DM/ha.
“It’s not unexpected but the difference is still being maintained,” he said.
“There will be a gradual change and the pastures do look quite different now. There’s less light getting in to the daughter tillers so the higher residual pastures are not doing so well. They appear to have more pasture growth, but that’s an illusion. It only lasts for a week then pasture growth and then pasture quality is expected to fall off.”
Because of that it’s expected the cows will need to graze lower-quality material in the future, so he was keen to see the impact compared with the herd still getting better quality pasture, regrown from paddocks where lower residuals were achieved. With DairyNZ gearing up for a dry summer across Waikato, Bay of Plenty and Northland it was basing expected pasture growth rates on records going back to recent droughts in those areas.
Milk yield from each cow in the two herds was recorded daily with a weekly herd test carried out to give milk composition.
At Westpac TARS the demonstration got underway a week later than Waikato on two farmlets, each of 31ha. There were two herds of 96 cows stocked at 3.1 cows/ha. Both the cows and the pastures they’re grazing were similar to those in Waikato, Kevin Macdonald was also supervising this demonstration, with farm manager Brett Thompson and local consultant Debbie MacCallum also involved.
Glassey said some farmers might be getting pre-grazing levels wrong by putting their cows in paddocks with too much grass. Or at the other end of the process they might not be taking post-grazing residuals low enough and using up supplements which would be better kept until they’re really needed in summer or autumn.
“Farmers can think they’re ahead with high grazing residuals but they don’t see some of the downsides until later on,” he said.
“We assume they exist so we want to know the extent of it. And we might discover something along the way.
“You’ve still got to manage pastures well even when the payout is high and you can afford supplements.”
He said it was likely DairyNZ wouldn’t be able to be conclusive about where the differences in the herds’ performance come from.
“If there are things we can’t explain we may have to dig deeper,” he said.
One of the consequences could be that a low residual level of 1500kg DM/ha might be right for pasture quality.
“But it could be at a cost to the cow, and that’s what farmers worry about,” he said.
He doesn’t believe that there’s any underestimation of the effect on the cow based on the evidence from the demonstration to date.
“In Taranaki the cost to the cow is minimal, but in the Waikato it’s more and we might have to question why.”
Results from the demonstration are posted on DairyNZ’s website.
Pasture focus lost?
It’s been suggested from a number of different quarters that dairy farmers have been losing their focus on pasture management over recent years, Chris Glassey said.
“A lot of extra feed other than pasture has been used with farmers chasing production rather than profit.”
In some respects, he said, he wasn’t surprised at the results from Sean McCarthy’s research showing 50% of farmers were getting pasture residual targets wrong.
The dairy industry was passing through an era when the farmers experienced in having pasture as their herd’s only feed were not actively managing properties any more.
“Some skills may have been lost because there’s no certainty they have been passed on to the younger generation,” he said.
“Some know nothing more than feeding palm kernel.
“But we do know there is still a lot of good pasture management going on out there.”
