Arching and fetlock knuckling in Normandy breed calves

See the detailed description below and the veterinary survey conducted as part of a veterinary thesis at ONIRIS.Arching/Fetlock and  and conformed animals are sometimes associated but not systematically: surveillance is necessary.

Arching and knuckling at fetlock are congenital tendon pathologies. The Charolais breed is known to often have this problem, but it is not the only breed. A hereditary component is currently accepted but has never been researched. In addition to hereditary factors, the in utero position of the fetus may predispose to this affection.

Arching can be defined as the impossibility of completely extending the carpus joint ("knee") and the fetlock by preventing its complete extension of the forelimb fetlock joint. In two cases, bending is always possible (even though the amplitude of mouvement is decreased), which will allow to differentiate an Arching/knuckling of the fetlock from an arthrogrypose.

A certain number of calves heal more or less spontaneously, especiallys if they are not too heavy. In other cases it is necessary to follow a conservatory treatment (immobilisation via extension of the members using splints or surgery by sectioning off the tendons.

The disease may affect the anterior Left, Right or both.

A specific description of these phenotypes has been established for:

Remote assessment, grading of gate:

□ Grade 1 - mild case: the calf can walk without difficulty but the its heal does not touch the groune. The calf puts its weight on the distal end of its hooves and its weight is shifted forward.

□ Grade 2 - moderate: the calf walks but the sole of the hoof is perpendicular to the ground. The calf remains standing for only a short time and has difficulty moving around.

□ Grade 3 - severe: in order to move, the calf must puts its weight on its carpus. The animal is not able to nurse without the breeder's help.

□ Grade 4 - Very severe: the calf cannot stand up.

If the following information is found, it may have an impact on the disease:

- farm practices

- animal feeding

- the health status of the farm

- the animal's antecedents and its pedigree

- precise information for the characterization of the phenotype (using a goniometer for example to measure the articulation)

--> See the detailed description below and the veterinary survey conducted as part of a veterinary thesis at ONIRIS.

Project progress report, January 2021

A campagne of specific sampling, with the project form, was set-up and a veterinarian doctoral student worked on the subject. Over a hundred declarations have been sent to ONAB to date. The samples received have allowed to extract the DNA, genotype the animals and to do the first genetic mapping analyses. Unfortunately the results from the first studies are not conclusive and lead us to believe that there is a multifactorial mechanism underway (influence of the environment and/or compensatory genetic mechanisms).

The studies have been suspended for the moment. The project may be restarted again as soon as new elements will allow the ONAB teams to progress efficiently.