They can start to build weeks pre-ovulation, with some females I noticed it is easier to "spot" then with other females.
We got a normal over here that has a HUGE build... and an even bigger ovulation...
When she ovulates she really will look like she just ate a bunny! Just keep an eye on if you can spot it you got an 24-48 hour window![]()
Just to be sure with myself I always mark all the sheds just incase... After either the ovulation or pre-lay shed they will move and hug the heat spot![]()