Same as above, but you have to remember to take the notes. I like weight and length when I do my equation. I use the ratio of length compared to weight to determine if she is safe to breed.
If you have a female that grows a foot over the year but only gains 300 grams she is probably a little skinny to breed, while another girl that has only grown a couple of inches but puts on that same 300 grams should be thick and ready to breed.