Registry Services - Genetic Disorders
OLWS (Overo Lethal White Syndrome)

OLWS is a disorder in which the caecum, colon and sometimes the rectum undergo a large dilation and fill with faecal mass. Associated with homozygosity of the Frame Overo gene it results in incomplete migration of nerve cells to the large intestine during embryonic development. Affected foals die within 72 hours of birth.

i) Any horse testing positive for the Frame Overo gene will not be eligible for registration in the Association’s Stud book or Appendix Register.

ii) At the direction of the Association all horses with white markings beyond the limits described in rule 8.1 k) will be required to be tested  negative for the Frame or Overo Lethal White gene using the official procedure before they will be considered for registration in either the Stud Book or the Appendix Register.