Studies have shown that dairy cows contribute large amounts of greenhouse gas emissions, caused by the organisms living in their microbiomes.
Genetically modifying cows may help reduce greenhouse gas emissions and feed world populations, a new study led by Prof. Itzhak Mizrahi of Ben-Gurion University of the Negev suggests.

“Our findings are both a major breakthrough for basic science and will have a positive impact on two major challenges facing the international community for the foreseeable future: climate change and food security,” Mizrahi said.

Mizrahi and R.J. Wallace, professor emeritus at University of Aberdeen in Scotland, led a group of 31 scientists in investigating the microbiomes of lactating dairy cows and the genes that are responsible for them.

Studies have shown that dairy cows contribute large amounts of greenhouse gas emissions, caused by the organisms living in their microbiomes. According to a 2013 assessment by the Food and Agriculture Organization of the United Nations, dairy cows added 2,128 million metric tons of CO2 to the atmosphere in one year.

The Israeli findings indicate that specific microbes in the cows’ rumens, or stomachs, determine the amount of methane that cows emit. Within cows’ stomachs is a diverse colony of archaea, ciliate protozoa, bacteria and anaerobic fungi.

The researchers conducted experiments on 1,016 cows – 816 Holstein dairy cows and 200 Nordic red dairy cows – across Italy, Finland, Sweden and the United Kingdom.

As milk consumption goes up and the number of cows increases along with it, Mizrahi thought that it was important for scientists to look into the rumens of cows to figure out how to mitigate the effects of the cow population on the environment. He emphasized that his role was not because he has an opinion as to whether or not the cow population should increase, but that as a scientist, he hoped to perform a “good service to the public.”

Some scientists and public figures have suggested solutions, such as feeding cows grass or cutting back on the amount of meat that human populations consume. However, Mizrahi said he simply started with the facts on the ground: The number of cows keeps increasing and something needs to be done about the negative impact they are having on the environment.

“The idea here is not to take an opinion on growing more cows, it’s just reducing the impact, the global impact or the negative impact, by using this finding,” he said.

Decreasing the amount of methane emissions from cows would have a benefit aside from the environmental, Mizrahi found: feeding world populations. He and his team found that the cows that release less methane also produce more milk, in what he called a “win-win.”

“Methane basically encompasses energy within it,” he said.

“Now, when they release it to the atmosphere, the energy is not getting into the cow, where it can be used to, for example, produce more milk. You basically lose energy that would go towards milk production.”

Producing more milk could solve some of the hunger that could arise from increasing world populations, according to Mizrahi. “Even now, the planet is operating at maximum output for meat and dairy products, and that problem is only going to get worse in the coming decades: By 2050 the world will have approximately 9 billion people,” he said. “That’s going to mean a serious crisis in protein nutrition.”

Mizrahi said that with his findings, it would be possible to selectively breed cows, preferencing those whose rumen microbiomes produce less methane. With adequate support on a public policy level, he predicted that a breeding program could replace the majority of dairy cows in the space of five to 10 years.

In future research projects, he hopes to delve deeper into the rumen microbiome and to learn to genetically engineer them. By “studying the rules that govern how microbiomes are being assembled,” Mizrahi hopes to learn more about microbiome functions and ecosystems, explaining that “The fundamental questions are: How do we govern the effect of microbiomes?”