Some common genetic defects in sheep

Abstract

While many genetic defects are lethal or semi-lethal (cause the death of only some of the individuals with the affected genotype), the gene frequency for some of these diseases can reach surprisingly high levels in defined populations, presumably due either to the founder effect or the presence of a selective advantage of heterozygous individuals. Some of the more common genetic defects are entropion, brachygnathia, cleft palate, cryptorchidism, hernias, and hereditary chondrodysplasia (spider lambs). Heritable conditions considered less common include arthrogryposis, Dandy Walker syndrome, cerebellar abiotrophy, microphthalmia, and abomasal emptying defect. The higher incidence of cervical vertebral malformation in the progeny of certain Texel rams suggests a heritable component.