Pregnancy makes breasts bigger, so why not keep a few cows pregnant forever to see just how big they can get?
On paper, that seems like a fairly straightforward idea. Pregnancy = bigger boobs. More pregnancy = more bigger boobs. Rinse and repeat.
The flaw in that logic is that hucow pregnancies can be a little... unpredictable.
A lot of what makes a hucow a hucow comes down to hormones. Some women make the right mix naturally, others need some extra help, but it's the hormones that dictate how their body acts. They're what give a woman udders instead of breasts. They're what drive her production far beyond what a normal person would be expected to make. Hormones are even responsible for the docility that we usually see in hucows. Getting a hucow pregnant can disturb that delicate balance of hormones in fairly wild ways and it's not always the same for each cow.
A lot of people think that hucows are naturally predisposed towards multiples, but that's not actually true. A hucow is no more or less likely to have multiples than a normal woman. The key difference is that, if they do wind up having multiples, it's very likely to be a high number of multiples. Twins and triplets among hucows are actually less common than quintuplets and octuplets, with the record being even higher than that. This can cause wild swings in hormones for cows that are carrying so many babies inside them and those swings can bring a wide variety of psychological effects.
In one instance, a hucow with decuplets started to see the whole herd as her children and became aggressive in her protection of them. Seeing someone burdened by a pregnancy of that degree charge her handler for daring to put a hand on another member of the tribe is definitely a little funny, though significantly less so for the handler. In a similar case, a hucow with nonuplets also felt ownership over her herd and started to take on a maternal role, but it was chaos for the farm as she insisted on breasfeeding all of them, pouring copious amounts of her milk into the mouths of her fellow cows. And, of course, her milk carried some of her hormones in it, which went on to wreak havoc across the whole herd. By the time they figured it out, one of the younger hucows had already started to exhibit signs of a psuedo-pregnancy of her own!
In some ways, though, the ones that don't have multiples have it worse. Since hucows are more likely to carry so many babies, their bodies take on additional changes to help support them. For cows with a singlet, their body still does all those things, but it has nowhere else to go. Singlet hucows often gain a ton of weight. Their bodies are desperate to eat just about anything they can get their hands on, using the spare calories to go towards babymaking and towards making milk, but with only one baby, all that extra fat just stays packed on her body. Occasionally, singlet hucows will instinctively feel like, with only one baby inside them, that they haven't actually been bred! Many a cowhand has been caught in the sights of a hucow desperate to be bred despite already being pregnant, just with only one child.
Some farms, especially ones with more resources, do take the risk, but it's rarely worth the chaos. Even between different pregnancies for the same cow, the outcomes can be wildly different. Or, rather, I should say will be wildly different. Once a hucow has a taste of being pregnant, they're going to be desperate to get it again. That need to be full never goes away.