I read from forums that breeding quality impacts vit/sub/ess and can kinda cap it so the highest it is, the bigger chance that it increases, but breeding is a bit random.
As for me I try to rise breeding quality first then look at milk quantity and quality, or at start it was too easy to make milk quantity go from 10 to like 5 when I didn't pay attention to that.
And for easier look at what your animal stats are, I use a notepad doc. If you do not have many breeding animals it is not that hard to make one.
Heres a part on how it looks. (F - female, M - Male, tM - tiny Male)

Some stats are mostly unimportant if you need milk, like meat and hide things.
If I had to sort by importance its probably breeding q > milk-quantitiy/quality > vit/sub/ess.
Well the idea is that with the breeding q increase the vit/sub/ess would increase. Not too sure, but other people whom I asked about this knew even less than me so I had to guess, but they weren't really farmers.
Bessie 5 has nice vit/sub/ess, but both Bessie 5 and 4 have low breeding quality, so I would say not too great for further increase.
Bessie 6 has nice breeding but it has so low milk quality and quantity.
Bessie 3 has nice breeding ands other stats arent too bad except, vit/sub/ess is a bit low.
In my case, I would choose Bessie 3.