Theileria hits new $6m dairy conversion hard
Beef cattle possible source
Converting a piece of farmland to dairying is a tough, stressful time for any farm owner.
But it has been a particularly challenging first season for Limestone Downs after one third of its herd was struck down by theileria.
The 3129ha property south of Port Waikato had undertaken the 18-month $6 million development, turning its coastal flats into a 330ha milking platform, complete with a 60-bale rotary shed, a weeping wall effluent system, silage bunkers and races.
It was completed last season and began putting milk in the vat on August 1 last year.
Then on August 26, dairy farm manager Aaron Frazer rang Franklin Vets production animal veterinarian Brent Neal, asking him to inspect a cow that was showing theileria symptoms.
The cow had pale mucus membranes, eyelids and vulva. It struggled to walk, had a fast heart and respiratory rate and her milk production had ceased.
Neal immediately suspected theileria and took a blood sample. It was confirmed the following day.
Speaking at an open day at Limestone Downs in February, Neal said there was always at least one major issue farmers have to deal with during a dairy conversion.
"But I have to admit, I don't think anyone was quite prepared for what we have seen at Limestone Downs in the last six months."
Farm supervisor Kevin Lowe called it "the perfect storm", and C Alma Baker Trust board chairman Chris Horton said as farm owners it "was the most devastating thing that can happen on a farm".
The disease, which is spread by ticks and causes anemia quickly spread through the herd.
Neal received another call from Frazer two days later.
Some of the herd had died and when Neal visited, he observed three cows with theileria symptoms. These cows were crawling with millions of tick nymphs.
These cows were given blood transfusions. This involved taking five litres of blood from a donor cow and transferring it to the sick cow. In the next few months, he performed this procedure dozens of times. He said it was a highly effective treatment.
"It gives the cow a boost in unaffected red blood cells to get her through this crisis where her red blood cells are being destroyed."
The herd looked incredibly unhappy as they went through the milking shed. They were walking slowly, and the paddock they were in had a very high grass residual, which showed that the cows were not eating.
"By this stage the alarm bells were well and truly ringing," Neal said.
Production was also down, due to the cows fighting the infection rather than using their energy to make milk.
The farm had two herds. One had 300 cows that calved in mid to late July and the second had 300 cows that calved in mid-August. Many had calved without too many problems.
Most of the worst affected cows were from the later calving herd. Neal believed this was because these were the calves under the most stress in the herd.
Three days after the initial call, Neal came out to the farm for the morning milking and examined every cow's back end. A healthy cow's vulva is pink, whereas Neal was seeing a lot of pale vulvas.
"That morning we pulled about 180 cows. At that time at least a third of the milking cows had shown some signs of anemia," he said.
They also blood tested 62 cows and 58 came back anemic.
They gave these 180 cows a supportive treatment by placing them in their own mob and kept them as close to the shed as possible. They were milked once a day to try and lower stress levels as much as possible.
Those cows without theileria were given a tick control treatment to slow the spread of the disease to unaffected cows. However, if a cow was already bitten, this control would not remove the theileria.
A week later Neal returned to the farm to check the herd.
The affected cows were improving, although there had been some further deaths.
On September 3, he was asked to check over a bull beef calf suspected and later confirmed of having theileria.
This made Neal believe the disease had been on the farm before the herd arrived in July.
"Our hypothesis, which I doubt we'll ever prove, is that it was possibly bought in in the previous season in 2012 from some bull beef animals."
The infected ticks from these animals then infected the local tick population. When the uninfected dairy cows subsequently arrived in June, the ticks infected the herd.
A week later, Franklin Vets managed to secure a theileria vaccine from Germany and received a special import licence to bring the treatment into New Zealand.
Limestone Downs was one of the first farms in the country to receive this treatment that is now available wholesale in New Zealand.
About 35 animals were vaccinated and most responded very quickly, showing significant improvement.
Others were too far gone and died.
The treatment comes with regulations. It has a withholding period for the treatment of 35 days with milk and 140 days for meat.
Milk from these treated cows could be fed to replacement cows but not to bobby calves.
Although the affected cows at Limestone Downs had already calved, if this had been given to a pregnant cow, then the calf either had to be kept as a replacement or culled. It cannot be sent as a bobby calf.
The treated animals had to be identified with a special tag for life to show they were treated with the disease and the treatment has to be registered with NAIT.
Frazer tagged these animals with a special blue tag so they could be identified in the herd.
This is done to protect the country's export market so no treated milk or meat gets into the food chain, Neal said.
Neal's main concern were animals bought into the herd such as bulls brought in for mating. These animals would receive a tick treatment as soon as they got off the truck.
Neal's estimated that the outbreak cost the farm $200,000 in vet costs and lost milk production.
That does not include the costs around extra labour by the staff in treating infected cattle, the extra food they were given and the infected cows' loss of fertility.
The infected cows' six-week incalf rate was 60 per cent, 7 per cent below the district average.
New theileria cases had stopped after a month.
MAF incursion officer Kevin Lawrence said cattle infected with theileria develop an immunity to the disease.
"That's why the kneejerk reaction to kill all ticks could be wrong because if you keep a population of ticks on your property they will continuously re-infect the cattle.
"That immunity will stay in an endemically stable level."
Neal said they had looked for theileria on many farms since the disease had come to New Zealand.
"Pretty much every farm we have looked for it, we have found it."
But the vast majority of those farms had seen no cows with anemia or they had seen one case.
"Our theory is that the vast majority of cows were infected either in late lactation or in a dry period when they are under very little stress, they have developed their own immunity and have got over it."
The cows at Limestone Downs were exposed to theileria when they were under the peak amount of stress, Neal said.
Neal said the farm had started to see the light at the end of the tunnel by the end of September.
Then on October 9, bovine viral diarrhoea virus (BVD) was detected in the milk after a routine check.
The virus was traced back to two cows in the herd, he said.
A follow-up test in early January showed the farm to be all clear.
Looking ahead, the vat will continue to be monitored for BVD and they will look for any carriers in the replacement cows and cull them.
Neal said it was not practical from a cost standpoint to test every bull beef calf coming onto the farm.
Instead they will monitor their heifer calves and remove any carriers among them and continue to vaccinate the herd.
Trust chairman Chris Horton said it had been a difficult year that resulted in huge pressures.
But the dairy conversion would improve Limestone Downs' returns over the long term by diversifying its revenue streams. This would allow the Trust to better meet its charitable obligations.
"It was easy to make the executive decision to convert part of the farm to dairying, the execution became an entirely different operation for a variety of reasons."
The Trust employed AgFirst consultant Dave Miller to advise them on the conversion.
Their targets in the first season was to convert 290ha, milk 600 cows and produce 200,000kg milk solids.
In July 2013 they increased their herd size and milked 770 cows producing 170,000kg MS.
Eventually the farm would have 800 cows, milking off a 330ha platform and target 280,000kg MS.
Miller said the farm's big advantage was it had excellent pasture growth in the winter that set it up well for the spring.
Summers were more challenging and it did get dry.
This autumn, the farm will go through a regrassing programme that would see 35ha regrassed and put into permanent pasture.
An area out the back of the farm would be direct drilled and there was 22ha to be humped and hollowed.
Three paddocks of maize had been planted and it was expected to yield 400 tonnes of maize silage.
The farm will winter 800 cows this winter and peak milk 780 in the new season.
He hoped the farm's operating expenses would be $4.40-$4.50/kg MS.
"Because of our modest cow production, our feed conversion isn't particularly efficient, we'll need about 14kg dry matter to produce 1kg MS, which means we'll need about 3.4 million kg of dry matter this coming season."
- Waikato Times