Evening meals for sheep could mean fewer greenhouse gases - Research

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Changing the time a sheep eats may have an impact on how much nitrous oxide ends up in the atmosphere from its urine.

A study, carried out by Lincoln University, On-Farm Research, built on work originally based on nitrogen concentration in dairy cows' urine, senior lecturer at Lincoln University in livestock health and production, Jim Gibbs said.

"Because dairy cows are pretty much always on a once-daily break and typically, for us in the South Island, that will be in the afternoon [the researcher] was looking at how that urine concentration changed every two hours right around a 24 hour cycle," Gibbs told The Country's Jamie Mackay.

Two things stood out in that study, the really strong changes in nitrogen concentration in the urine, and also the amount of urine mirrored the cows' grazing times, Gibbs said.

"The upshot of if it is - if the grazing time is set in the morning they produce more urine and higher nitrogen urine in the daytime. If it's set in the evening, then they'll produce more urine and higher nitrogen urine in the evening."

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Sheep urine research

For the sheep study, researchers studied 12 merino ewe lambs and fed them either in the morning or in the afternoon.

The sheep were fed with annual ryegrass harvested at 8am to ensure that feed quality was consistent for both feeding treatments.

Peak urine volume occurred eight hours post-feeding and the lowest urine volumes occurred immediately prior to feeding.

Researchers found that both groups peed out roughly 60 per cent of their urine volume in the following 12 hours.

They pointed out that warmer daytime temperatures increased how much urinary nitrogen ultimately turned into the greenhouse gas nitrous oxide out in the pasture.

The researchers suggested that timing a sheep's feed so that it goes to the bathroom overnight could help lower how much nitrous oxide is ultimately made, especially in late winter.

The work also suggested that shifting animals to new pasture late afternoon would result in more urinary nitrogen being deposited at night when lower ambient temperatures should lead to reduced volatilisation and lower N2O production.

Understanding the relationship between time of feeding and subsequent nitrogen excretion may enable the development of better farm management strategies to reduce greenhouse gas output.

The work was funded by the Ministry of Primary Industries Sustainable Land Management and Climate Change (SLMACC) Fund, Project Number ONF30870.

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