In cattle, large amounts of ammonia and laughing gas are released, which damage the environment and contribute to climate change. But willow leaves as a natural feed additive could reduce these nitrogen emissions and make animal husbandry more sustainable in the future, as an experiment. Accordingly, wicker leaves in beef feed reduces nitrogen emissions by up to 81 percent by changing the digestion of the animals and the microbial decomposition of their excretions in the soil. This is made possible by the interaction of various ingredients in the willow plants.
Ammonia (nh3) and laughing gas (n2O) are two gaseous nitrogen compounds that harm the environment and the climate. Ammonia gets out of the air into the floors, acidifies it and ensures that the ecosystems with nitrogen are fertilized. Lachgas damages the atmosphere ozone layer and has a greenhouse effect for the climate. However, it looks about 300 times stronger than CO2 And remained in the atmosphere after the release at around 150 years.
The largest source of both gases is global agriculture, which releases the nitrogen compounds in large quantities. A significant part of these emissions – about a quarter – arises directly on the pasture – through soil bacteria, which disintegrate the nitrogen containing nitrogen and urine of ruminants such as cattle, sheep and goats. This creates ammonia, nitrite, nitrate and laughing gas. However, these animal excretions cannot be avoided or eliminated with reasonable effort.
With willow leaves against nitrogen in the cattle cattle
A team led by Carolin Müller-Kiedrowski from the research institute for farm animal biology (FBN) in Dummerstorf has now examined whether the nitrogen emissions from pasture keeping can be reduced in other ways. For this, the researchers mixed a well -known natural remedy among beef feed: willow leaves. It is known from previous studies that plants of these leaves, so-called tannins, change the animal nitrogen metabolism, which is why pasture leaves in New Zealand are also used as feed for ruminants. However, willow leaves also contain salicylates such as salicylates, tremulacine and salicortin – vegetable forerunner molecules of the pain -relieving salicylic acid. Müller-Kiedrowski and her colleagues have now checked in a series of experiments with eight calves whether and how strongly the willow salicylates also intervene in digestion as well as the nitrogen and urea metabolism of cattle.
It showed that cattle are fed alongside grass and concentrated feed with pasture leaves instead of lucerne-hau, their urine excretions contain significantly less urea. Instead, the urine contains more hippuric acid, but the salicylates in the beef pipi apparently inhibit the bacterial conversion of urea and hippuric acid into ammonia. In addition, hippuric acid has an inhibitory effect on the microbial conversion of nitrogen compounds to laughing gas, as the team stated. In the cattle mixed with soil, Müller-Kiedrowski and her team found 14 percent less ammonia and even 81 percent less laughing gas than in rehearsals under control feeding without willow leaves.
In dung, urine, stomach and blood samples as well as vapors of the animals, the team also found different compositions of nitrogen compounds after feeding-further indications of changed metabolic processes. As a side effect, the cattle also came up with eight percent less of the potent greenhouse gas methane per kilogram of body weight (CH4) out of. In contrast, the researchers found no evidence of a growth rate changed by the pasture leaves or nutrient supply to the cattle. There was indications of a slightly improved soil structure with increased humification and reduced nitrate formation on the pastures.
Weiden leaves as a feed additive in Germany?
These results suggest that wicker leaves, as the feed additive, can effectively lower the nitrogen emissions of livestock farming and at the same time protect the soil without harming the pasture animals. However, the observed digestive-regulating, emission-reducing and soil-promoting effects of the willow leaves are not only due to the salicylates, but to interplay with other ingredients on willow leaves, especially tannins and phenols such as Müller-Kiedrowski and their colleagues.
The findings now also open up a potential use of the rapidly growing pastures for animal nutrition in this country. So far, the trees in Germany have been used primarily as a supplier of wood chips for heating power plants or in agroforS systems to improve the biodiversity of arable land and to protect fields. “Weidenlaub is a locally available, renewable raw material, which is also particularly suitable as a natural feed additive,” concludes senior author Björn Kuhla from the FBN.
Other tree leaves could also work
Follow studies should now clarify whether the effects observed in the experiment occur even under real keeping conditions in the pasture instead of in the test room. Because depending on the type of willow, the type of soil, the soil type, microclimate and microbioma in the soil as well as feeding behavior of the cattle, the pasture leaves in the animal body could have different ways and subsequently in their excretions. The team led by Müller-Kiedrowski also examines whether, in addition to pastures, other salicylate-containing loud ones may also be suitable as feed additives, for example poplars. If the effects are confirmed, the trees could in future be planted in a targeted manner on the cattle willow and serve as a source of feed on site. This would reduce nitrogen emissions in a sustainable manner and at the same time improve the local microclimate and biodiversity.
Source: Research Institute for Livelihood Biology (FBN); Specialist articles: Agriculture, Ecosystems & Environment, DOI: 10.1016/J.agee.2025.109671
