On Waitangi Day weekend in 2006, he noticed something was wrong.
Young pigs weaned from their sows suddenly began losing weight at his mainly outdoor piggery west of Christchurch.
A vet was called in who delivered the difficult-to-accept diagnosis. The weaners had been exposed to post-weaning multisystemic wasting syndrome (PMWS), a disease that had first surfaced a few years earlier in the North Island.
Clinical signs included slower growth rates, laboured breathing, visibly enlarged lymph nodes and sometimes diarrhoea and jaundice.
With no known cure, the terminal prognosis was hard to take as most of the young animals had to be put down.
Mortality rates in his case accounted for half of some litters.
"I’m lucky I survived as my production was halved and even those piglets that did survive weren’t particularly economic and hadn’t grown well so it was a terrible time."
Dark days followed.
Where did the disease come from and how did it get here, were questions running through his mind.
"We had our scientists looking at it and the only way we could’ve got it was through meat products coming into New Zealand.
"It was well proven that you could catch PMWS from meat that had been exposed to it. My farm fed no meat or feed waste products so we can only deduce that the disease spread by aerosol from a backyard pig farmer.
"It was an absolute horror and the worst thing I’ve ever, ever had to deal with in my life.
"It’s so demoralising on your staff and yourself seeing these pigs you’ve got up to 25 to 30kg and they were healthy one day and the next day they would just start to waste away. There was nothing you could do."
Only a recently developed vaccine rushed into the country saved more from dying.
Mr Trengrove continues to call it an overnight miracle.
Like other farmers riding out the setback, he developed resilience.
That has seen him weather the disease storm and many other challenges faced by pig farmers such as import unfairness, defending criticism from animal rights activists and more lately the buildup of compliance and regulations.
Equally, there has been a lifetime of many rewards for the industry leader who has helped steer pig farming in new and innovative directions.
For his many contributions to the pork sector he has just been recognised by NZPork with an Industry Lifetime Achievement award.
Mr Trengrove switched from banking to farming in the late-1980s, a seemingly curious change that was not as much of a stretch as might appear.
For a start, pig farming is a numbers game demanding strong business skills, but there were other attractions.
"I loved the outdoors and had been exposed to farms in my younger life and that’s where I wanted to be.
"When I looked around with what I could do with farming on very little capital, pig farming made sense.
"I started out breeding piglets and selling weaners and the numbers were if you looked after that sow and her welfare, fed her well, she was going to produce 18 to 20 piglets for you. You can’t get that from any other animal."
Today, his 400-sow operation has grown to the stage that each sow produces 25 to 26 piglets. The end product is sold to a wholesaler and most goes on supermarket shelves as fresh pork.
From the beginning, the innovative farmer could not afford an indoor operation and gravitated to a hybrid outdoors model.
He prefers to call it "free-farmed" as he is uncomfortable with "free-range" labels, saying they were bandied about too much for his liking.
To be true to a free-range designation, he would have needed a huge premium to warrant extra feed costs. Free-farmed was a more accurate description, he said.
Canterbury is one of the few regions where raising pigs outside is feasible because of its rainfall, topography and free-draining soils.
Mother pigs only come indoors to go in the crate for a week while giving birth — to care for their needs and those of their progeny.
"It is very labour intensive, but that was the only way I could see I could increase my numbers and balance out the welfare between the sow and the piglets.
"In the early days I had losses of 25% to 30% and I’ve got that down to 10% now which is huge. When you’ve got a 250kg sow and a 1kg piglet at birth, the odds aren’t so good as they can be a clumsy animal.
"They’re also an intelligent animal and, believe it or not, I think they understand a sow in a farrowing crate is the best place for them."
After the week the sows were returned to their paddocks with their newborns.
The "60-something" farmer also pioneered artificial insemination for outdoor pig herds.
Bringing in the best genetics and ensuring sows were being mated and mated correctly was a big improvement, he said.
"In those days, people said how can you do that with an outdoor sow and once again I looked at what they do and how do they do it inside and looked overseas to come up with the idea of being able to stimulate the sow by just having a boar placed near to them in smaller pens.
"Of course when a sow’s in heat she’s pretty interested in the boar and that way we were able to come up with a form of confinement to AI those sows."
Loyal staff have helped him grow the business, including his farm manager, who has been with him for 35 years after starting as a school leaver.
As an innovator, Mr Trengrove is a big supporter of the industry’s research and development in many fields such as pig welfare, stocking densities, farrowing crates, sow confinement and meat quality.
He led the decision for NZPork to be part of a joint research initiative with the Australian pork industry.
Artificial intelligence is being developed around the world with cameras capturing piglet growth rates and herd health.
This research investment is helping farmers keep on top of challenges.
Mr Trengrove said when he started it was possible to earn a living with far fewer pigs than now and the profit margin today was far less than it once was.
"So it’s become a greater and greater numbers game to stay profitable."
During his 15 years on the NZPork board, nine as chairman, he is most proud of putting pressure on government agencies for a major review of import health standards. Close behind this is the introduction of the sector’s PigCare welfare assurance programme.
Pig leaders went through a "long, long battle" pushing for stronger barriers to prevent exotic disease entering the country through pork imports, he said.
"We were battling with the government and in those days it was the Ministry of Ag and Fish — now MPI [Ministry for Primary Industries].
"Because we’re not an exporting sector of agriculture, they saw any import health standard barriers as being a non-tariff barrier which really put our industry at risk.
"We are sure that we contracted PMWS from imported pork. Our closest trading partner in Australia is very sympathetic of its pork industry and import health standards for importing pork into their country are far more stringent than ours so all we want are level playing fields."
New Zealand farmers were eventually successful in achieving the introduction of better import health standards, albeit a watered-down version compared with Australia.
"We were at risk particularly in the earlier days when there was a lot more feed waste being fed to pigs. If it wasn’t being processed properly it could carry raw imported pig meat and if we just let it all happen I think we could have been very much challenged further than we have been."
Today there remain many thousands of backyard owners of pigs. The commercial industry is less than 100 commercial producers.
The risk of more exotic diseases entering the country was still strong.
So far, New Zealand has avoided African swine fever as it spreads from China to Europe and around the world.
Mr Trengrove said it could enter via imported products and it was unknown if a vaccine under development would work.
New Zealand farmers had also taken issue with producers of imported pork having an unfair advantage as often they were not under the same animal welfare scrutiny as local farmers.
"We aren’t a low-cost producer and the unfair advantage is the subsidies some of these countries get."
For example, grain in New Zealand was unsubsidised and farmers would pay about twice as much as overseas competitors because of subsidies.
To remain viable, New Zealand growers separated their product from the rest by developing clear country-of-origin labelling with the 100% New Zealand Pork slogan.
Consumers wanted to know where their product came from.
However, the fine print of "Made in New Zealand" labelling for bacon showed it could be imported from several countries and merely processed here.
"When I first started farming there was no imported product coming to the country and we produced over one million pigs.
"Now we’re down to 600,000 and that number seems to keep on decreasing and the pressure on our industry to be more efficient is a huge hurdle."
PigCare labelling was also placed on packaged fresh, and some processed, pork.
"When we brought in PigCare several years ago we started talking about what we can do to ensure the consumer is buying a product being cared for under very good welfare standards," he said.
"I think we are far better than most places and we have in place an audit system that is independently audited at each farm if they want to sell product under the PigCare label."
Sow confinement had come under the spotlight with the average time in farrowing crates about 28 days for indoor piggeries.
Mr Trengrove said the pork industry had recognised consumers were wary of long confinement and believed intervals of a week to 10 days should continue to protect newborn piglets.
Animal rights activists who opposed farrowing crates
had not taken into account the welfare of piglets.
Using a crate for one week to 10 days was much better than a sow killing 30% of its litter, he said.
"I think one of the most unfair things is where the current welfare standards could land would make us completely uncompetitive with the rest of the world."
A new draft code of welfare for pigs includes a requirement doubling the space for a growing pig inside a shed or fattening accommodation.
Mr Trengrove said this increase without further investment created its own welfare challenge and he suggested it would halve the current production of about 600,000 pigs a year.
"That would only make us more uncompetitive because we would only be producing 300,000 pigs from that same fattening accommodation and doubling our fattening footprint would be at a huge cost to the New Zealand pig farmer.
"Yet the rest of the world uses farrowing crates backed by some very good sound science to protect piglets," he said.
"Some sort of confinement, even for a short space of time, is required to remain competitive and balance the welfare of the sow and the piglets."
Despite the many challenges, putting so much of his time into representing the pork industry was an easy decision.
"We’re a small industry and I wanted to be at the coal face to help the direction and what went on in the industry and how we would farm.
"I just saw there were a lot of challenges out there and the best way forward for my business was to be involved in the industry."
He would encourage any top young farmer to enter pig farming.
"Farming pigs is hugely rewarding in many, many ways and using specialist management skills and caring for your sows and their progeny will reap huge benefits on farm.
"There are some young talented people out there that we would love to see in the industry.
"Farms are getting bigger and it is more difficult ...
we would like to think there’s a sharefarming model like the dairy industry would be one way of getting younger people a pathway forward."
That is already happening at several farms as pig farming evolves to stay relevant.
- By Tim Cronshaw
