In 2008, a new form of arthrogryposis, characterised by a low birthweight and multiple joint involvement (and therefore referred to as arthrogryposis multiplex or AM) emerged in the Angus breed following the widespread use of the elite sire GAR Precision 1680 and his descendants, most notably CA Future Direction 5321 (Windsor et al., 2011).
A commercial Angus producer in the Bathurst region saw three small, premature but not noticeably abnormal calves during the last five years including one in 2020. The first calf born in 2021 was also small and premature but was not obviously abnormal. When a second, clearly abnormal calf was born the owner decided to investigate. The calf was small with arthrogryposis. Genetic testing was consistent with the calf having two copies of the arthrogryposis multiplex (AM) gene.
While AM has largely been eliminated in the seed stock herd though genetic testing (Denholm 2017), it is undoubtedly still present in commercial herds. Commercial breeders who use known AM-free bulls over heterozygous cows should not see affected calves but those who breed their own bulls may be at risk unless they test either the bull, breeding cows or the bull progeny.
Several small premature calves have been born on this property over the last five years. Some of these may have had AM but this hypothesis is unproven. The known affected calf (figure 1) was delivered by a two-year-old heifer on 20 August 2021. The sire of the affected calf was a homebred bull bred by AI from a known AM-free sire (Baldridge Download Z013) indicating that the dam was heterozygous for AM. Both the heifer's sire and dam are of unknown AM status, but the homebred sire presumably also carries the gene.
The property runs 80 Angus cows and heifers, and calves from early August to mid-September. The cattle graze pastures predominately comprised of cocksfoot (Dactylis glomerata), phalaris (Phalaris aquatica), ryegrass (Lolium perenne) and subterranean clover (Trifolium subterraneum). Blue heliotrope (Heliotropium amplexicaule) is an emerging problem. When pasture production is inadequate, the cattle are supplementary fed primarily oaten hay. Calves are weaned in April and the steer portion sold, with heifers retained. The cows are vaccinated with 5-in-1 clostridial vaccine at pregnancy diagnosis in mid-April. Young stock are vaccinated against clostridial diseases (5-in-1) and infectious bovine keratoconjunctivitis (Piliguard, Coopers Animal Health) at calf marking and given a 5-in-1 booster at weaning.
The affected calf was a 14 kg female delivered close to term with a grey hair coat and a crown rump length of 60cm. The head appeared normal with no cleft palate. There was marked scoliosis with cervical vertebrae twisting to the right and marked flexion of all joints of the left forelimb. The right forelimb had marked flexion of the shoulder and elbow, with mild flexion of the carpus and metacarpus. Additionally, there was diffuse muscular atrophy across the thorax and pelvis. The left hindlimb was markedly flexed across all joints, whilst the right hindlimb had marked flexion of the coxofemoral and stifle joint. An ear tip sample was submitted for testing for pestivirus and AM and thoracic blood was collected to test for immunoglobulins and serology if warranted.
Genetic testing of the tissue sample submitted was consistent with the calf having two copies (affected) of the mutation responsible for Arthrogryposis multiplex congenita in Angus cattle. The calf was negative for pestivirus antigen and IgG levels were not elevated.
Arthrogryposis is a congenital condition characterised by ankylosis of multiple limbs (Zachery & McGavin, 2012). The most common presentation involves marked flexion of the forelimbs, scoliosis, muscular atrophy and occasionally central nervous system signs (Windsor et al., 2011; Zachery & McGavin, 2012) The pathogenesis of the disease in Australia is complex and may result from gestational arbovirus infections or plant teratogens. A genetic form of the disease presenting as arthrogryposis of multiple joints, scoliosis, cleft palate and kyphosis has been described in Charolais and Angus cattle (Leipold et al., 1969; Romero et al., 2020). The most recent form, Arthrogryposis multiplex congenita in Angus cattle is also an autosomal recessive genetic disorder (Windsor et al., 2011).
Calves with arthrogryposis are typically stillborn or die shortly after delivery. Dystocia is common due to the musculoskeletal abnormalities associated with the condition (Zachery & McGavin, 2012).
In this case, genetic testing indicated that this calf had two copies of the autosomal recessive AM gene. Akabane infection was not tested for but was not regarded as a consideration because there were no reports of transmission during the pregnancy of the dam.
This finding indicates that there are AM-carrier cows and homebred bulls within the herd. The owner plans on testing homebred bulls prior to joining and will test potential bulls at calf marking. It is not considered necessary to test the cows to be artificially inseminated as these vary from year to year.
We would like to thank and acknowledge the owner, Ian Hendry, who provided the material and information for this case and who greatly assisted Steph Ferguson in the difficult task of completing a remote case investigation.