Wednesday, April 24, 2024

Sheep better for the climate?

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Sheep milking is a growing industry in New Zealand and a new study shows it might be better for the environment.
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Sheep milking is potentially more environmentally-friendly than dairy cow farming, according to a study by AgResearch scientists that shows nitrogen leaching per hectare can be reduced by up to 50%.

Senior scientist Diana Selbie says the research aimed to provide evidence for the environmental credentials the NZ sheep milk industry has in export markets.

“Based on the funding that we had, we prioritised looking at nitrogen because dairy sheep could be an alternative land-use option in, say, nitrogen-stressed catchments,” Selbie says.

“So we started with trying to get some baseline measurements: what does nitrogen leaching actually look like beneath grazing dairy sheep?”

The work started with a review of existing scientific literature about nitrogen in sheep milking farm systems but there proved to be not much of that, so the research shifted to on-farm measurements on Pamu-owned Spring Sheep Milk Co’s property near Taupō and another site in South Otago.

“The crux of our work was around nitrogen loss to water and we found on a per-hectare basis that the loss can be reduced by between 10% and 50% (compared with dairy cows), so the potential loss reduction is quite high,” she says.

Much of that reduction can be attributed to what scientists call the “edge effect”, which means nitrogen in urine is spread across the paddock through plants being able to access more nitrogen around the edges of smaller urine patches.

Selbie says the large range is due to a combination of soil and climate factors, as well as how much nitrogen goes through the farm. More research needs to be done to get firmer data. But she says it is clear that, like dairy cow farming, one of the greatest influences on potential nitrogen losses is the level of inputs, such as nitrogen fertiliser and feed.

“The amount of feed the animals are eating on a per-hectare basis, the dry matter intake, is a key driver for both nitrogen loss to water and greenhouse gases,” she says.

“The more they’re eating per hectare, the more likely you are to lose nitrogen and emit greenhouse gases.”

The study included a range of farming systems from extensive to intensive.  The more intensive dairy sheep operations can produce a similar level of environmental emissions to dairy cow farms.

As the expanding sheep milking industry focuses on productivity and genetics, Selbie cautions the associated likely increase in environmental emissions of their operations.

“There’s a broad suggestion here: learn from what the dairy cow industry has been through and pick up on interventions they are already using to lower their environmental footprint,” she says.

Selbie says there’s more work to be done to get the full picture, but that will depend on funding for future research.

“There’s certainly a lot of interest from individual farmers and also collectives, both in the North Island and South Island,” she says.

The sheep milking industry is growing in NZ, with the 18 commercial operations set to be boosted by another 13 starting in the coming season.

“It’s actually quite an inspiring and interesting industry to be part of because it’s small and the biggest players are very open and sharing their experiences, so that means communication and learning is quite efficient,” she says.

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