Mares should be prepared for breeding season well in advance for the best chance of a successful pregnancy. | Adobe StockMares not prepared well ahead of the equine breeding season often take longer to cycle, need to be bred more times to conceive, and might have lower overall fertility. During a presentation at the 2025 American Association of Equine Practitioners Convention, held Dec. 6-10, in Denver, Colorado, Etta Bradecamp, DVM, Dipl. ACT, ABVP, of Rood & Riddle Equine Hospital, in Lexington, Kentucky, explained how veterinarians and horse owners can work together to prepare mares for breeding season.Breeding Soundness Exams for MaresA key starting point is the breeding soundness examination, said Bradecamp. For barren mares, ideally veterinarians should perform this evaluation in the fall, not at the beginning of breeding season. Ultrasound, uterine culture and cytology, and assessment of the cervix and perineal (region between the anus and vulva) conformation can identify lingering issues such as chronic endometritis, urine pooling, or compromised reproductive barriers. Addressing these problems months in advance can make the breeding season easier for both the mare and veterinarian.Lighting for Breeding ManagementArtificial lighting remains a critical management tool, especially for breeders aiming to have foals born early in the season. Most mares in the Northern Hemisphere have their first ovulation of the year in early April. To advance that timeline, mares need 60 to 70 days of extended light exposure beginning around Dec. 1, said Bradecamp. Owners can accomplish this using traditional barn lighting programs or light masks, which allow mares to stay outdoors while still receiving an effective photoperiod. However, light exposure works best when mares also have adequate nutrition and protection from extreme cold, she added.Nutrition and Body Condition for BroodmaresNutrition and body condition play a central role in reproductive efficiency. Researchers have shown that mares entering the breeding season thinwith a body condition score below 5are slower to cycle and less likely to conceive easily. In some studies, breeding efficiency was enhanced in mares entering the breeding season or foaling at a body condition score of 5 or above, said Bradecamp. Winter management deserves particular attention because mares expend more energy to maintain body temperature and might lose condition without thoughtful feeding strategies.Chronic Health Conditions in BroodmaresPrior to the start of breeding season, veterinarians should investigate chronic health issues in broodmares. Equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (PPID, formerly equine Cushings disease) can interfere with normal ovarian activity, and both conditions often require months of dietary and medical management before seeing improvements. (Veterinarians) need to correct these metabolic problems early so that once breeding season arrives, the mare is well controlled, said Bradecamp. Diet and exercise changes often help control these conditions, but horses might also benefit from medical managementespecially those with PPID.Chronic pain and lameness might also affect reproductive performance, said Bradecamp. She noted that researchers on multiple studies in cattle showed lameness negatively affected fertility. Additionally, it is important to understand the effects that medications used to treat pain might have on the reproductive cycle, she said.A mares cortisol levels could also affect her fertility. The mare that has gone from being stalled and blanketed might not do well being turned out year-round and fighting for her meals in a group, said Bradecamp. Having these mares with the least amount of stress possible in their lives is important. Some non-steroidal anti-inflammatory drugs can affect uterine clearance, and flunixin meglumine (Banamine) has been associated with an increased incidence of hemorrhagic anovulatory follicles when administered near ovulation.Take-Home MessageEquine breeding success reflects long-term management rather than last-minute intervention. Addressing reproductive soundness, nutrition, lighting, and systemic health well before the breeding season begins gives mares the best chance to cycle normally and conceive efficiently. One must be productive before they can be reproductive, said Bradecamp.