Analysis of hereditary eye anomalies in cattle and horse

Hereditary eye anomalies do occur in all livestock species. In the current project, two malformations in cattle and horse are analysed with the aim to develop gene tests.

Bilateral convergent strabism in cattle

Bilateral convergent strabism with exophthalmus (BCSE) is a hereditary disorder in different cattle breeds. Affected animals develop bilateral progressive strabism with a protruded eye (see figure on the left). In the course of disease the animals can become completely blind and the impaired vision leads to jumpiness and an unsteady gait, which causes problems in handling. Therefore, otherwise healthy animals have to leave the herd early. The disease usually manifests during or after first lactation, when rearing already has caused significant costs. The timely identification of affected animals is therefore desireable. Previous studies have, however, not identified causative gene variants suitable to develop a genetic test. The aim ot the currecnt project is to analyse the genetic architecture of this condition in Holstein cattle and to identify genome regions invoved in the development of BCSE.

Equine hereditary microphthalmia

Microphthalmia presents as an abnormally small globe with or without various other ocular anomalies. It might occur unilaterally or bilaterally. Remnants of ocular tissue, however, are always present. The complete absence of eye structures is called anophthalmia, a very rare condition. A small but otherwise normal globe is termed nanophthalmia. In this case, sight of affected animals might be normal, while very small and malformed eyes lead to impaired vision or blindness. The occurrence of hereditary microphthalmia is known in various domestic species. Microphthalmia does also occur in horses, especially of Arabian or Thoroughbred origin. In horse breeding, however, it was sometimes assumed that this condition is caused by malnutrition or exposition of the pregnant mare to teratogenic substances and that there is no genetic cause. The observation of familiar microphthalmia in Warmblood horses indicated a heritable trait: equine hereditary microphthalmia. The aim of the current project is to identify causal gene variants in order to develop a genetic test, which is suitable to avoid carrier matings.