At birth, pony foals from draft mare surrogates were 57% heavier than pony foals from pony mare surrogates, Peugnet said. But despite the former foals being so much bigger, they were actually born about a week earlier than the latter foals. | Photo: Courtesy Pauline Peugnet

As embryo transfer becomes more common in equine reproduction, researchers are discovering the importance of surrogate mare selection for optimum foal growth and metabolic health.

Recently, French scientists implanted embryos from ponies, light saddle horses, and draft horses into surrogate mares of different sizes and observed significant differences in weight, height, barrel circumference, and metabolic markers among the resulting genetic half-siblings, said Pauline Peugnet, PhD, of the French Agricultural Research Institute in Jouy-en-Josas. Peugnet presented her study at the 2014 French Equine Research Day, held March 18 in Paris.

These effects not only influence the animal’s growth potential, but also its metabolism, which can play a role in insulin resistance and perhaps even osteochondrosis (a developmental orthopedic disorder) development, she said