The development of Polish ponies born after embryo transfer to large recipients

Abstract

Summary Embryos from Polish pony mares (387 to 400 kg) were transferred to larger draught‐type mares (561 to 780 kg). Upon confirmation of pregnancy in the recipients, the donor mares were mated again to the same stallions. Six pairs of full sibling foals were obtained from which three pairs with matching gender were selected for long‐term developmental studies. All the foals born to recipient draught mares were larger and heavier than their siblings born to the genetic mothers. They also developed more rapidly during the nursing period. After weaning, the differences between individuals of each pair gradually became less evident. However, even at 53 months of age, there were still distinct differences in height at the withers (4 to 6 cm), length of front legs (4 cm) and length of cannon bones (1 to 2 cm).