CARRIER–Contractural Arachnodactyly (CA)
Contractural Arachnodactyly (CA) calves are normally born alive and most can walk, suckle and survive. The birth weight of CA calves is normal. The phenotype is subtle and hence CA may not initially be recognized as an inherited defect. Contractures which reduce the range of angular movement of the upper limb joints are present at birth in CA but are much less severe, without rigid joint contractures. Due to these contractures, CA calves at birth assume an abnormal crouched posture, resembling an elk or deer fawn, with the feet placed more to the rear that normal, hocks pulled up and back and the spine slightly arched. In their first days of life, CA calves are also flat down on their pasterns. Although there is a reduced range of movement ("contracture") in the upper limb joints, particularly the hip, stifle and hock, there is an increased extensibility of the lower limb joints, particularly the pasterns.
CA affected calves are reported as taller and more slender, than their unaffected siblings. Australian researchers assert that the inability to passively extend the hip, stifle and hock joints to the normal extent by pulling downwards on the foot of a newborn calf — while it is held on its side on the ground — is a valuable diagnostic sign in CA cases. Affected calves can show significant recovery and usually appear relatively normal by 4 to 6 months of age. As weanlings and yearlings, the CA calves appear lighter framed and lighter muscled, particularly in the hindquarters. Most perform poorly and remain tall, slender animals with poor foot conformation. The more normal appearance of CA cases as mature adults makes early evaluation of the phenotype essential. Australian researchers have also reported the early onset of degenerative arthritis in cows that were CA-affected as calves, particularly in the stifle joints.
