Floppy lamb syndrome û an inherited lower motor neuron disease in open-faced Romney lambs

Floppy lamb syndrome û an inherited lower motor neuron disease in open-faced Romney lambs
Peer reviewed


A naturally-occurring genetic condition of a lower motor neuron (LMN) disease in a small flock of related open-faced Romney sheep was discovered after a sire-to-half-sister mating resulted in the first case of the disorder. Subsequent intentional matings of this sire to his daughters resulted in more affected lambs. The signs became obvious after the lambs were 7–10 days old. Over several days, the condition would worsen to the point that the lamb would be unable to get up without help. The lambs continued to suckle but became ‘floppy’ and showed marked medial strabismus within a week of becoming recumbent. Controlled matings of the ram to his daughters resulted in some stillborn and weak lambs that had histopathological lesions consistent with LMN disease. In several incidences, lambs that were unable to get up after birth were assisted for 24–48 hours, at which time they became ambulatory, only to develop the ‘floppy lamb’ condition at 10 days to 2 weeks of age. Histologically, the lesions in stillborn lambs and lambs euthanised at 2–3 weeks of age included degeneration and loss of neurons with spheroid formation in the brain stem, oculomotor nucleus, and ventral horns of the spinal cord. Wallerian-type degeneration was also evident in the latter, as well as neurogenic atrophy of muscles. The disorder is an autosomal recessive trait. Extensive literature reviews suggest that the condition is similar to spinal muscular atrophy in children; however, the genetic aberration that causes the floppy condition in lambs is currently unidentified.

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