Arachnomelia in four Italian Brown calves

IN recent decades, Undesirable genetic defects havc occ Urred in Browvin cattle (Browni Swiss, BraLunvieh and Itallia BI3 vni), of which the weaver svndromne has been the most well klo\nwn. As a resuLlt of preventixe genetic progranmmes and the availability of genetic tests for detecting carriers, the prevalenice ofdisease in the populationi hals been substantially rcduLced. Spinal ImuLIsculariatrophy, spinal dvsmyelination anid conigenital myopathy otlherdefects of younig calves have also been the subject of illtelsiVe studics. Their genetic origini has becn established, althouLghl 1not in a definitive mannner. Arachnlomlelia ('spider-legs'), a congeniital abbnormiiality of the skeletal system giving the animilial a spidery look, has beenl reported as anotlher unldesirable and fatal genetic disease of Browni cattle (Rieck and Sclhade 1975, Brem and others 1984, K(nig anid others 1987, Leipold and Steffen 1989). Althogll it has not been possible to find candidate genes so far-, this disease iS attributed to a simiple recessive genetic defect, with an1 Americani Brown Swiss bull or a cow of the samiec breed postultated as the origin of the defect (Konig and others 1987). This short com1TmuLnication describes the nmost important pathological finidinigs of foulaffected calves, which were submitted as part of a surveillance plan for genetic discases in Brown cattle in Italy. Four dead, newborn Italian Brown calves (thlee fenmale and one male) were brought to the Department of Veterinary Clinical Science, Padua, because of macroscopic skeletal malformations of the skull and the hindlegs. All of the calves could be traced back to the same sire, which was already knowni to be a carrier of the defect. Facial deformities were evident in all of the animials, anid were nmainly characterised by a short (approximately 5 to 10 cm) lower jaw (brachygnatlia inferior) and concave rounding of the dorsal profile of the maxilla (Fig 1). The tip of the maxilla was tapered and slightly turned upwards, and was also shifted laterally in one calf. The head profile resembled that of a pointer dog. All of the calves looked 'crouched' due to a pronounced kyphosis. Their legs appeared much longer and thinner than normal (dolichostenomelia) and were curved. The thinness did not affect the epiphyses of the long bones, but did affect the diaphyses, especially those of the metacarpus and the metatarsus. In addition, severe angular deformities were observed in the distal part of the hindlegs, characterised by marked bilateral hyperextension of the fetlocks with the extremity of the toe forward and parallel to the trunk of the body (Fig 2). The fetlock joints were stiff. Long bone fragility was suspected on the basis of multiple leg fractures in three of the calves, possibly as a consequence of a traumatic event such as calving, and the muscles of the legs were atrophic. Radiographs of the legs showed that the diaphyses of the long bones were curved, and the thinness prevalently affected the bone medulla. Cardiac mnalfort-nations were cxvdent in one calf; they wvere characterised by complete trainsposition of the arterial truniks anid bilateral conicenitric ven1tricUlar hpcritrophy. This vas very severe in the left ventricle; in fact, the left ventricUlarcavity was onie third the size ot the right ventricuLlar cavity. Although some overlap betwecen this abnormality and Malrfan svndrome in humiiani beinigs hals beeni higlhlighted, the rapid tal couL-se obser-ved in the fouLcalves makes clinical identification wvith the humnan disease iniappropriate. In fact, Mlarfan syndrome in humnani patienats is not usually fatal. Moreover, a true 'bovine Marfain synidrome', more closely resembling humnani Marfan svncidrome, has also been described (Potter and others 1993, Potter and Besser 1994). To the authors' knowledge, this is the first documientationi of arachnomelia in Italian Brown calves. As the sire of the calves has been widely used for artificial inseniinationi in Italy in recent years, further cases of the disease are expected. As neither chromosomal nor biochemical tests are available to detect the carriers of this defect, only the reporting of malformed calves and the identificatioin of clinical cases enable carrier animals to be established in retrospect.