Abstract

A skeletal chondrodysplasia (noncancerous abnormal cell growth affecting cartilaginous tissues) characterized by dwarfism and angular deformity of the forelimbs has been recognized in Texel and Texel cross lambs. Some affected lambs have normal co-twins indicating the disease is likely to be of genetic origin. This study outlines the mode of inheritance of the disorder. Three affected rams were mated to 221 unaffected ewes to generate 123 daughters, which were backcrossed by multiple sire mating with their sires the subsequent season to produce 83 lambs for evaluation. The time course of the morphological progression of the disease was recorded. Of the 46 lambs that were successfully diagnosed, 22 were affected with the condition and 24 were unaffected. This was consistent with a 50:50 ratio expected for recessive inheritance in a backcross between affected and carrier animals. Within sexes, 11 males (24%) and 11 females (24%) were affected with 10 males (22%) and 14 females (30%) were unaffected. This was not different (P<0.05) from a 0.25 proportion for autosomal recessive inheritance. Variation in the age of onset (16 days ± 7 days) and severity of clinical expression suggests variable penetrance, with semi-lethality.

TJ, Byrne, HT Blair, KG Thompson, KM Stowell, and S Piripi

Proceedings of the New Zealand Society of Animal Production, Volume 68, Brisbane, Australia, 20-22, 2008