Passage of a calf through the pelvis exerts pressure on the obturator nerve. The close association of the obturator nerve with the origin of the ischiatic nerve can complicate interpretation of clinical signs.
Because the adductors are innervated by the obturator nerve, an animal adopts a base-wide stance or, in recumbency, a sitting position with both hindlimbs extended forward. There is considerable risk that the adductor muscles will be damaged and that permanent recumbency will result. In addition to the base-wide stance, knuckling of the fetlock may be present. This indicates injury of the ischiatic nerve. Both conditions may contribute to downer cow syndrome (see Bovine Secondary Recumbency).
If obturator paralysis is recognized early enough, vigorous measures should be adopted to prevent complications involving the adductor muscles. The animal should be immediately transferred to a site where there is good footing (eg, a base of tenacious manure over which clean straw has been spread) to prevent slippage during attempts to rise. The hindlimbs can be tied together with a soft nylon strap fixed below the hocks. The limbs are restrained from “spreading” >3 ft (1 m) apart.
Last full review/revision September 2015 by Paul R. Greenough, FRCVS