Feeding seaweed to reduce emissions Is seaweed a viable enteric methane mitigation option for the dairy industry? by A.N. Hristov
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opular media has created a buzz around feeding seaweed to ruminants in order to cut down their enteric methane emissions. Curbing methane release to the atmosphere (whether from oil and gas or livestock) is important, and the animal science community and livestock and feed industries are working hard on finding effective and economically feasible mitigation technologies with some real successes in recent years. The dairy nutrition group at Penn State started investigating seaweeds as feed additives about two years ago, supported by federal and private organization grants. Our efforts have been directed toward in vitro screening of a large number of temperate and tropical seaweed species for their methane mitigation potential. We are also investigating dairy cattle responses to Asparagopsis taxiformis, a red seaweed shown to have a large inhibitory effect on enteric methane emission in sheep, and more recently, beef cattle by Australian researchers.
A closer look at seaweed The in vitro work is ongoing and was reported at the 2019 Northeast American Dairy Science Association (ADSA) meeting, and another abstract was presented this summer at the 2020 ADSA meeting. This article will be focused on the A. taxiformis work.
Researchers at Penn State evaluated the inclusion of a seaweed called Asparagopsis taxiformis in dairy cow diets. Asparagopsis taxiformis is a macro alga found in tropical and warm temperate waters. The species deposits compounds called bromoforms which, along with other halogenated compounds (chloroform and bromochloromethane), have been shown to have potent methane mitigation properties. The mode of action of this class of compounds is thought to be through inhibition of the methanogenic pathway at the final step of methane formation. The methane inhibition effect of A. taxiformis has been demonstrated in several in vitro experiments, and more recently, in exper-
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iments with live animals. The halogens are known to cause ozone depletion and are banned in many countries around the world. These compounds are also suspected to be carcinogenic. Preliminary in vitro data at Penn State showed that A. taxiformis reduces methane formation by 95% at a 1% inclusion rate (on a dry matter basis). These in vitro experiments were followed by several experiments (two completed and one ongoing) with lactating dairy cows. A. taxiformis was fed at 0.25% up to 0.75% of the cows’ daily dry matter intake. In the first study, aimed at determinjofnm.com
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