Do Recipient Mares Pass Traits to Foals?
—Jessica Wieland, Germany
A. There is data available indicating that the recipient mare does influence a foal’s traits. Most of this describes the effect of recipient mare size in comparison to that of the donor mare. In a study on transfer of pony embryos to either pony or draft mares, a research group in Poland found that at maturity (4 ½ years) the pony-in-draft foals were 1.5 to 2.5 inches higher at the withers than those in pony mares, and they also had proportionately longer front legs, especially the cannons, which were almost 10% longer in proportion to body size.
These findings were supported by a study in England in which foals resulting from pony embryos transferred to Thoroughbreds were compared to foals resulting from Thoroughbred embryos transferred to ponies, and both were compared to their same-size recipient controls. The foals from embryos transferred to the “wrong” size mares were different from their control siblings not only in weight and height at birth but also in their growth patterns. At 3 years, the foals’ body weight, length from head to tail, girth, cannon bone circumference, and forearm and cannon bone lengths differed from those of the control foals. In another study by the same group, foals from identical twin embryos that had been transferred to different-size recipient mares differed three inches in height at the withers at
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