Ancient Greek writings describe livestock eating seaweed, as do Icelandic sagas.
And, as the picture shows, sheep on North Ronaldsay, in the Orkney Islands of Scotland, still graze on the stuff.
But that is now seen as unusual. It may not be in the future, however, as research conducted in Australia and New Zealand
suggests algavory of this sort may reduce greenhouse-gas emissions from stock animals.
The research in question is being co-ordinated by CSIRO, Australia's main science agency.
The project is looking into microbes that inhabit the stomachs of ruminants such as cattle and sheep.
These bugs transform those animals' fibrous fare into energy-rich molecules, some of which the host animal is able to absorb and utilise.
One energy-rich molecule that is not absorbed, though, is methane. Instead, the animals belch it into the atmosphere.
Which is a problem, because methane is a greenhouse gas that has a warming effect 28 times as powerful as carbon dioxide's.
Since this loss of methane also deprives the host of the energy therein,
thus probably reducing its growth rate, controlling methanogenic bacterial activity in ruminants looks like a beneficial twofer.
The antimethanogenic powers of Asparagopsis, the seaweed in question,
were discovered in 2016 and experiments involving it have been going on since then.
One of the latest, published in October in the Journal of Cleaner Production,
其中最新的一篇發表在10月份的《Journal of Cleaner Production》上，
showed that dairy cows eating a diet containing 1% Asparagopsis produce only a third of the methane belched by cows on seaweedless diets.