A mare mule--dam or foster mother?

Area of Science:

• Veterinary Genetics
• Equine Reproduction

Background:

• A mare mule was reported to have given birth to a horse-like foal after mating with a Shetland stallion.
• The presence of three pregnant Shetland mares in the same pasture introduced ambiguity regarding the foal's true parentage.

Purpose of the Study:

• To accurately determine the parentage of a foal initially attributed to a mare mule.
• To investigate the reproductive events in a mixed pasture of equines.

Main Methods:

• Phenotypic assessment of the foal (appearance, voice).
• Karyotype analysis to determine chromosome number and structure.
• Blood typing and transferrin system analysis for genetic profiling.
• Monitoring of births and lactational status of mares in the pasture.

Main Results:

• The foal was phenotypically and genetically identified as a horse.
• Transferrin system analysis excluded the mare mule as the biological mother.
• Evidence suggested one Shetland mare gave birth to twins with a prolonged interval.
• The mare mule spontaneously lactated and adopted the first twin foal.

Conclusions:

• The foal was the offspring of a Shetland mare, not the mare mule.
• The mare mule acted as a foster mother to the foal.
• Complex reproductive scenarios can occur in mixed equine populations, necessitating accurate genetic and phenotypic analysis.