They do use the same sound effects to make the calls for both of these species, so I'd assume so, as even though the star whale was the last of its kind, the cash cow appeared in the 21st century from the rift, presumably, and so could have come from when there were more of them.
The "cash cow" in "Meat" was an aquatic species & had to be sprayed with water to keep it alive. The Star Whale in "The Beast Below" is at home in interstellar space. They're obviously not closely related. Whales on Earth, though, are descended from land animals, so it's possible that the relationship between the Star Whale & the "cash cow" might be similar to that between (say) blue whales & landbound descendants of the whales' landbound ancestors.