Interesting - I wonder how sheep's milk and goat's milk compare with cows milk. Both of the above are readily available where I live (in Luxembourg).
I believe the worst aspect of conventional dairy farming is the methane emissions from bovines. However, I have no idea how the emissions from sheep (rarely farmed for milk in most countries; ours comes from France where they are often farmed for milk in areas where bovines would not flourish) and goats compare.
@Paulos_the_fog @Herbivore methane emissions from bovines are not a single item - grass fed outdoor beef produces a lot less methane than house or fed (cattle cake) beef. Most of the methane from beef production comes from slurry - releases methane in the rotting liquid. Straw-manure systems release less methane than housing that collects slurry in a tank. Actual ‘cow farts’ are not scientifically significant - it is the manure systems that are. https://science.nasa.gov/climate-change/causes/
@Paulos_the_fog @Herbivore I think outdoor reared milk has a much lower carbon footprint than milk from housed cows. So surely goat and sheep would also be lower as they are less frequently housed. Sheep in particular (if not overgrazing and not fed) can be part of carbon capture not a loss if the system is organic and the wool is used locally / composted (I.e. crofting).There’s a shortage of data on sheep farming and considerable differences to dairy. https://www.cambridge.org/core/journals/journal-of-agricultural-science/article/carbon-footprint-of-uk-sheep-production-current-knowledge-and-opportunities-for-reduction-in-temperate-zones/0C6D9CE40AB7AAF3B8CDD4CA1AD9E5B5