Just a FYI to devs who decide on the parameters: the current parameters allow probably a lot more animals than you expect.
The reason is that the current view distance is 4 chunks. + the one you stand in = 72 blocks in each direction remain loaded. or 144 to each side in a square.
The current radius on all farm animals is 100. Thus, if you make 4 pens of 20 animals each in the corners of your view distance, all 4 of them will be further than 100 blocks away from one another, and you actually can maintain 80 animals loaded at once per person. I suspected this but I wasn't sure people would actually do it. It turns out they have rapidly figured it out and are indeed doing it currently.
If you want it to work like this, then okay, but it is pretty artificial seeming, and rewards people who min/max the parameters exactly, which is a little meh IMO. If you want to limit loaded herd size to the parameter amount and encourage more natural single pen setups, then radius needs to be scaled with view distance in mind. In the case of view distance 4, the mustercull radius would need to be 144 * rad(2) = 203 or higher in order to only allow one group of [limit parameter many] animals per online player. (in between 144 and 203 would still allow two pens in opposite corners)
In compensation with the same amount of lag as now, you could accompany that with a bump in the limit amount to, say, 30-35. To end up probably making most people happier, no longer differentially rewarding meta game min/maxers, and making mustercull more intuitive.