Ummm, who is slaughtering DAIRY CATTLE????? Holsteins ain't very good eating... too bony.
Have you been drinking???
Now, if you are referring to BEEF CATTLE, then that is a different situation entirely. Some farmers will put a timed-release hormone implant in a calf's ear (and THOSE hormones are the same kind as naturally occur in them anyway) so that it grows more uniformly and reaches the potential size norm FOR THAT BREED!!! And most of the breeds have been refined for a hundred years or more, to provide desirable characteristics depending on the intended use for that breed.
And before you start gasping over a timed-release hormone implant, then you should also be protesting the pregnancy contraceptive patches that women wear, too.
Your apocalyptic visions of Franken-cows the size of woolly mammoths who are full-grown by the time they are weaned COULD NOT BE MORE WRONG. Or hilarious for that matter.
Now, you also might be confusing referring to feedlot operations where cattle farmers will buy cows and steers who are nearly ready for slaughter, and they will 'finish them' on grain, so that they have a better taste, and other desirable qualities, but NOBODY is pumping hormones into cows who are nearly ready to be slaughtered.
It is the broiler CHICKEN operations that pump growth hormones into them and who grow them in inhumane conditions. Some of those operations are inexcusable, and are DIRECTLY the result of corporatizing animal husbandry, with the economies of scale that must be there to maximize profit.
Most cattle operations on the east coast are NOT like that (Cattle don't do well in those conditions). I believe the average herd size in the east, is around 150 head, but I haven't been keeping up with it. (lately)