Scaling back on antibiotics

February 1 2020

Waikato farmers Brendon and Rochelle O’Leary talk about the responsible use of antibiotics – how they’re approaching the issue on their farm and how it’s been working.

Brendon and Rochelle have been on their 85ha farm in the peatlands of Gordonton for 25 years. They run a System 5 farm with a full autumn calving herd of 400 cows. Brendon has been involved with DairyNZ’s DCT (dry cow therapy) Decision-Making project, which has been underway for five years.

In Brendon’s role of farmer representative for the project’s stakeholder group, it was his job to “consider how practices would be implemented on-farm – the pros and cons”, he explains.

Why reduce antibiotic use?

“There’s momentum in the market around the world that we need to reduce antibiotic use in our dairy herds,” says Brendon. “We can’t ignore this – we’ve got to get on the bandwagon.

“Antibiotic use impacts the whole food chain – if we’re putting all these antibiotics into cows, how does that fit down the line with antibiotics no longer working to treat infections in humans and animals? The key is to start reducing antibiotic use at the source.”

Brendon’s thoughts were backed up by his vet, who said, ‘what use is an antibiotic up a teat canal if there are no bugs to kill?’

In the summer of 2017/18, Brendon took the leap to dry off using DCT for high-somatic cell count (SCC) cows, and teat sealant alone for low-SCC cows.

First attempt and lessons learned

The first attempt at selective use of DCT didn’t go quite as Brendon had planned.

The dry-off period went well, with no cases of clinical mastitis. However, once calving began, there was a high incidence of mastitis. Economically, a lot more was spent on milking-cow antibiotics than what was saved at dry-off.

“We turned a lot of low-SCC cows into three-titters or high- SCC cows because our process wasn’t robust enough. It was really disappointing,” says Brendon.

“We realised that, when drying cows off, we needed to break their routine. Cows are creatures of habit, so after dry-off, we needed to stop bringing her to the feed pad, reduce her feed, and put her at the back of the farm so she doesn’t hear the cowshed going.”

Back to blanket

Brendon’s confidence had taken a hit, so the next season, he and Rochelle reverted to whole-herd (blanket) DCT.

“A lot of things had gone backwards so we needed to ride that out.”

It was a good move for the farm, says Brendon.

“We’ve turned things around and corrected some of the mastitis issues we had. We’re now in a position where we can move forward.”

Giving it another go

This time around, Brendon will be transitioning the cows better through dry-off, to support a new regime of selective DCT.

“I’m feeling confident going into this dry-off. As long as we follow the procedures, we should be more than right. Lowering the SCC threshold for cows that don’t receive DCT gives me extra peace of mind.”

Brendon’s criteria for selecting animals to receive teat sealant alone is an SCC below 150,000 cells/ml for cows and below 120,000 cells/ml for heifers. Seventy-six percent of the herd will be eligible for teat sealant alone. The remaining 24 percent will receive a combination of DCT and teat sealant.

Finance isn’t a driver, but their cost of doing selective DCT this year will be $4600, which represents a $2000 saving.

Keep moving forward

Brendon now has plans for a similar DCT strategy on his other farm, managed by his son Alex.

“Sooner or later we have to implement this, so it’s better to get started early and get our strategies right and have confidence. Move ahead of the curve rather than be the last one to start.”

“My advice for other farmers is to surround yourself with good advice from veterinarians. Should you do it, and to what degree? All farms are different.”

Brendon’s dry-off plan this summer

  • Dry off in small groups – 50 days before calving date.
  • Separate the group seven to 10 days before dry-off.
  • Reduce feed to reduce milk volume.
  • Day of dry-off – give time to ensure things are done right with teat hygiene, product administration and teat spraying.
  • When cows are let go from the shed, make sure they’re not running down the race swinging their udder, moving the products out of the teat canal.
  • Use good quality teat sealant.
  • Hygiene at the teat end is crucial.

Project outcomes

The DCT Decision-Making project’s five-year investment by DairyNZ, supported for three years by the Ministry for Primary Industries’ Sustainable Farming Fund (SFF), has been used to:

  • survey farmers and vets to learn about their attititudes towards antibiotics and how they’re using them on-farm
  • assess mastitis prevalence at dry-off across 36 herds, evaluating the effects of specific interventions
  • develop and promote science-based protocols that support less use of dry cow antibiotics on New Zealand dairy farms
  • survey farmers annually to evaluate reduction in use of antibiotics at dry-off.

This work has been guided by a stakeholder steering group, of which Brendon was a key member. Chaired by Cole Groves (Grove Dairies, Ashburton), and involving farmers, vets and other stakeholders, the group has provided an influential forum to ensure workable solutions are introduced.

Learn more about responsible use of antibiotics at

This article was originally published in Inside Dairy February 2020

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