A simple irrigation tip, methane and why dairy cows really don't need feed supplements

This post is a bit of a mixed bag. There is some gardening info, but this week I really wanted to delve into the issues around feeding dairy cows the supplement Bovaer.

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Substack Notes is a microblogging feature within the Substack platform that enables writers to share short-form content such as quick updates, ideas, article links, or brief observations. It’s designed to complement Substack articles, allowing for more frequent and conversational interactions with readers. Readers can like, comment, or share ("restack") Notes, which helps foster community and draw new subscribers to newsletters. You can read the published notes of writers you follow on the Substack app.

The reason I am mentioning this is because I post on Notes. This month I have an ‘Advent Calendar’ and each day I post a tip on creating a climate-resilient garden.

So far, I have covered topics such as encouraging ground beetles, planting a hedge wedge, building a dead hedge, opting for species tulips, planting a crab apple, genetic diversity of seeds, and more. There are 13 tips to come. But don’t worry if you are not on Notes as I will produce a compilation of all my tips at the end of the year. If you do use Notes, please join the conversation!

Here’s a tip that’s coming up in the next week

Clay pots for irrigation

An ancient and highly efficient method of irrigation, particularly popular among small-scale subsistence farmers in arid regions, uses buried unglazed clay pots known as ollas. These porous pots are filled with water and buried in soil near plants. Water seeps through the pot walls only when the surrounding soil becomes dry, making the irrigation rate responsive to the plants’ water needs. This method minimizes water waste, as there is no run off or evaporation from the surface.

Compared to modern systems like drip or surface irrigation, the olla method is exceptionally water-efficient and environmentally friendly. It’s also versatile, working well in greenhouses, polytunnels, and even large containers. While commercial ollas are available online, they can be expensive. A cost-effective alternative is to modify a standard clay pot by sealing the drainage hole and using a saucer or lid as a cover to reduce evaporation.

A buried pot in my greenhouse supplying water to the pepper

These pots don’t need filling every day, just once a week or so. Its targeted irrigation so you know your plants are getting the water they require. To install, simply dig a hole that’s wider and deeper than your pot, and gently fork soil around hole to aid drainage. Place the pot in the hole so its rim lies just above surface, gently firm the soil in place, fill water and cover to reduce evaporation and prevent small animals from falling in.

What is Bovaer and why is it a problem?

There’s been a lot of headlines around Bovaer in recent days, with videos of people pouring milk down the sink, unsold milk left on the shelves and producers fielding questions about their use of this additive.

If you live outside the UK, you may not be aware of the furore around this feed additive. Put simply, Bovaer is a feed additive that significantly reduces methane emissions from livestock by inhibiting a key enzyme involved in methane production in the rumen.

As some of you know, I was editor of Organic Farming magazine for 12 years and the question of farming and greenhouse gas emissions cropped up regularly. A few years ago, I wrote an article on methane so here is a bit of an analysis around methane, healthy soil and why I don’t think Bovaer is the answer.

Methane and climate change

There is no denying methane is a significant contributor to climate change. It’s global warming potential is said to be as much as 28 times that of carbon dioxide over 100 years. However, unlike carbon dioxide, it has a much shorter life of around 12 years.

The problem with methane is the sudden surge in levels since 2008. It came out of nowhere and scientists are still unsure of the cause. Current levels are around 1900 parts per billion, contributing an estimated 20 per cent of total atmospheric warming to date. Commentators have been quick to put the blame on ruminants, a blame game that started back in 2006 when the UN Food and Agriculture Organisation published a study entitled Livestock’s Long Shadow. The study claimed that livestock production was responsible for 18 per cent of all greenhouse gas emissions (a figure which has since been revised down to 5 per cent). Since then, many organisations have called for a reduction in meat consumption and a switch away from extensive systems to intensive ones in which animals are raised quickly, on grain and soya-based diets which generates less methane. However, it’s becoming increasingly apparent that the methane story is far from clear cut.

Interestingly, atmospheric methane levels did not rise between 1999 and 2006 despite a 70 per cent increase in livestock numbers and looking further back to times when vast herds of ruminants were grazing grassland across the world, methane levels ranged between 350 and 750 ppb. So what’s caused the dramatic rise over the last 12 years? There is much finger pointing. Some put the blame on leaks from gas fields, while research from Cornell University points at the boom in the US shale gas and oil industry. Discovering that the chemical fingerprint of methane from fracking differed from that of traditional fossil fuels and livestock, researchers were able to track the source. They claim that as much as a third of recent methane emissions may come from shale gas development. However, others suggest that tropical wetlands are the only source large enough to explain the sudden rise.

The role of microbes in the soil

It’s not just methane sources that’s important, we need to know how much methane is oxidised (broken down). This happens naturally in the lower atmosphere but there’s another methane sink to interest us. There’s a group of microorganisms called methanotrophs; single-celled organisms, such as bacteria, that consume methane as their source of carbon. They can be aerobic or anaerobic and are usually obligate, which means that methane is their only carbon source, so they are particularly common in places where methane is produced. Without them levels of methane would be much higher. In fact, half the methane released by wetlands may be taken up by methanotrophs and oxidised (Dunfield 2007).

Cows produce methane. It’s a product of their digestion in the rumen: the fermentation process breaks down the cellulose in grass and the product is methane which that cow belches out. Ruminant emissions vary, even within species. Cattle on high fibre feed produce more methane than those on a grain-based diet. But, as always, the whole picture has to be considered. Grain-fed beef animals may emit less methane, but overall, the energy required to finish these animals is twice that of pasture-fed, because of the use of fossil fuel in growing, harvesting and transporting the grain, plus the greenhouse gas emissions during the manufacture and transport of nitrogen fertilisers etc, while pasture-fed beef could be considered to be carbon neutral as the carbon is recycled via the plants. And when looking at the whole picture, it’s important to offset any methane production with carbon sequestering gains; a well-managed, rotationally-grazed permanent pasture will sequester carbon, so helping to offset methane production by the animals.

Cows burp methane which is mopped up by methanotrophs in the soil Image credit Shutterstock

Plenty of lab-based studies have measured methane in a cow’s burp, but this takes no account of its lifestyle. When they are on pasture, head down and grazing, a burp of methane soon gets mopped up by the methanotrophs in the soil. If you have a healthy pasture with a soil rich in microorganisms, methane is not so much of a problem. But place them in unnatural situations, such as vast feedlot in the US or on a poorly managed pasture in the UK that is regularly fertilised, you disrupt the system, and the soil will be less able to deal with methane.

What does Bovaer do?

Simply tweaking the cow’s diet can result in fewer methane emissions, for example feeding sainfoin silage, adding more oil or seaweed.

Scientists found that seaweed-eating cattle had lower methane emissions, which lead to more studies Image credit Shutterstock

So this is where Bovaer comes in. Bovaer is a feed additive developed the Dutch company DSM to reduce methane emissions from livestock, particularly cows. It contains a compound called 3-NOP (3-nitrooxypropanol), which inhibits an enzyme that microbes in the cow's rumen use to produce methane. By disrupting this process, Bovaer significantly reduces the amount of methane emitted, the amount depending on the diet and dosage. The additive has to be sprinkled on the food, so its possible to treat housed cattle, but not cattle in grazing on pasture.

I feel this is the wrong approach. It’s all very well to tweak the diet but interfering with the functioning of microbes in the rumen could have unforeseen consequences. Organic organisations across Europe, including the Soil Association, have made it clear that Bovaer is not permitted under organic standards.

In the case of Bovaer. I feel it’s a quick fix to reduce methane emissions in intensively managed herds that are housed. Pasture for Life summarised it well:

“We view the use of feed additives as a ‘business as usual’ approach, in that they represent another industrial solution to the problem of industrial farming, and can only be a short-term intervention at best. Furthermore, in providing a supposed solution to only one part of the problem – carbon – feed additives risk causing unintended side effects on other issues, such as animal welfare or biodiversity. It is imperative that we take a holistic approach in our assessment of the problem and the design of solutions and the use of feed additives do not meet this criteria.”

I remember a sheep farmer telling me that he felt very sorry for the cattle on a farm beside the fields his sheep grazed on the Pewsey Downs in Wiltshire. While his sheep were grazing a wonderfully diverse meadow, the cattle in the nearby farm could only watch and dream of doing the same as they were housed all year round.

There is no easy answer to the livestock question. I don’t think anybody wants a shift to highly intensive systems with all the welfare issues that would result, but without meat we’d need more crops and they require nitrogen. A lack of manures would mean more land under fertility building leys or more inorganic nitrogen fertiliser which has a major role in the methane story.

It’s a complex situation, whatever food is grown, there are methane implications.

If any reader would like to see my article on methane please let me know and I can sent a pdf.

Happy gardening

Sally

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