I forgot the timing - everything is so precise. The mare has several ultrasounds to check to see exactly when she's about to ovulate. When the vet says go, you call and make your appointment, usually a day (or two if you have the vet out again right before to make sure) in advance. The only way a mare doesn't get bred at the peak of her cycle is if the stallion is booked that day, and so you try for the next available spot and cross your fingers, but usually the mare is ovulating directly after breeding - within a few hours of it even. The stallions are seeing, like 160 mares each season and the timing has got to be spot on to fit all that in, so you get one good cover and make it count. 16 days later, another ultrasound to check for a pregnancy. If no, then the whole process begins again. If yes, you do another at 30 days, 45, AND 60. If you do lose a pregnancy, you gotta catch it ASAP so you can breed her back ASAP. You've got about 4, maybe 5 months to breed in, and the earlier the better, because the earlier the foal is born the better. TBs age is calculated by the year they were born, and they all have a birthday Jan 1st. So if your foal was born in May and is racing as a 2-year-old against other 2-yr-olds that were born in February, he's at quite a disadvantage (thus they typically don't make it to the track that year, and they do have to have passed their literal 2nd birthday to be allowed to run). Plus, he'll look itty bitty at the sales. Bad sauce.

Anyway: TIMING! Very precise.