Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbred auction yearlings, weanlings, 2-year-olds and breeding stock.
Question: When it comes to putting broodmares under lights for cycling are overhead lights or mask lights better? And why does it work?
Dr. Peter Sheerin, Rood and Riddle Equine Hospital: In many breeds, Jan. 1 is considered the birthdate for all horses in the breed, no matter when they are born. This can put late-born foals at a disadvantage when competing or at yearling sales. Because of this, many breeders want their mares to foal as early as possible.
The horse is considered a long day breeder, meaning they are cycling when the days are longer. Mares left at natural conditions in the Northern Hemisphere will typically start cycling late March to early April. Mares further north will start cycling later than mares closer to the equator. Researchers determined that by artificially increasing the day length and the amount of light that mares were exposed to, one could get mares to cycle earlier. Mares did not begin to cycle for 60 to 75 days after the beginning of exposure to longer days. So, for a breeding season that starts Feb. 15, one would start lights Dec. 1 at the latest.