As a general rule, when animals are calm and content, they don’t make much noise, but signal feelings by their physical attitude and movements.
Happy cows don’t moo. Sometimes they grunt, for example, when they’re eating (although they also grunt when they are defending themselves or announcing their rank in the herd). The only exception to this rule is calves at play. Kicking up their heels as they run around, they’ll make short maaw’s that start low and end in the middle of their vocal range.
It’s usually when something is not right, or out of the ordinary, that cows moo. The range of frequencies of these vocalizations suggest a more complicated social life than most people assume.
The separation and searching call of a cow looking for herdmates starts in a high pitch and goes higher, usually until the voice cracks.
A mother separated from her calf will run around, for days, making short moo’s that quickly rise from low to high pitch. Separated calves, meanwhile, make a meeeh or bleeeh that sounds something like a sheep’s ba-a-a-a-a, but shorter and without the rapid frequency oscillation (called vibrato when humans do it).
A mother connecting with her calf will make a low mmmmm sound, which sounds very different than a very uncomfortable cow (due to pregnancy or being squeezed together with other cows), who will make vibrating, low mmmmm’s.
“Each cow has her own method of asking a question, either with a look or a strange, quiet moo,” writes Rosamund Young, in The Secret Life of Cows.
Simply by paying attention to the animals around us, we can learn to distinguish the kinds of sounds they make. Understanding “cowmunication” makes it easier to empathize with their feelings, which are not different from ours.
It has been over 10,000 years since the first aurochs, ancestors of the cow, were captured and enslaved by people, but we don’t need their meat and milk to survive anymore, and their continued exploitation is one of the biggest drivers of deforestation and climate change. At this point, it’s time for us to give up beef and dairy.