Graphical Abstract
Summary:
Ultrasonic determination of antral follicle count (AFC) is used to classify animals into high or low AFC categories. These categories have a wide range and animals classified as low on one study may be considered high by another study based on the population. Associations with high AFC cows include greater follicular vasculature, blastocyst rates, hatched blastocyst rates, 12-d embryonic cell growth and cleavage rates, along with a lower number of embryonic apoptotic cells. More high AFC cows cycled as heifers at 15 months, had a greater pregnancy rate and conception rate and progesterone concentration after breeding, and fewer days to conception. However, other studies have found that low AFC animals had greater pregnancy and conception rates and progesterone concentration after breeding compared with high AFC cows. Low AFC cows also showed greater preovulatory follicle blood flow, greater blastocyst cell number, and greater area of the corpus luteum.