Perosomus elumbis in sheep.

Eight lambs affected with perosomus elumbis were examined during a 3-year investigation; one died during birth, six died soon after birth without rising, and one died at two days. Typically, the affected lambs had an infantile pelvis, thinner and smaller femurs, tibias and metatarsal bones, muscular atrophy, arthrogryposis involving most joints of the hindlimbs, and five had tail malformations. Associated malformations were multiple and included atresia ani (5), unilateral renal agenesis (4), cryptorchidism (4), perineal and diaphragmatic hernias (1), synophthalmia (1), high septal defect (1), cerebellar hypoplasis (1), and hydrocephalus (1). Five of the affected lambs were males and three were females. The incidence of 0.18% in 4,417 lambs examined from a large sheep population over a 3-year period suggests that perosomus elumbis is not an uncommon congenital defect of sheep.