Damage to the sciatic and obturator nerves after intrapelvic parturient trauma may cause recumbency after calving. The specific cause of calving paralysis is excessive and prolonged intrapelvic pressure due to fetopelvic disproportion. A large fetus, relative to the diameter of the pelvic canal, places pressure on the sciatic and obturator nerves. Either or both nerves may be affected; however, typically the sciatic nerve is more commonly damaged than the obturator nerve. The tibial and peroneal nerves are distal branches of the sciatic nerve that can be damaged at extrapelvic sites.
Clinical Findings of Calving Paralysis
Calving paralysis may occur after a difficult calving. Sciatic nerve damage results in knuckling of the fetlock (metatarsophalangeal joint), which is usually bilateral in severe cases and unilateral in milder cases. The animal has trouble standing, and when assisted to stand, the characteristic knuckling is present. Severely affected cattle can also have damage to the obturator nerve, resulting in an inability of the animal to adduct the hind legs. For this reason, cattle with obturator nerve paralysis are more likely to splay and hyperextend the hind limbs laterally (“do the splits”) when attempting to stand, leading to tearing of the adductor muscles and possibly hip dislocation. Damage to the sciatic and obturator nerves contributes to downer cow syndrome.
Treatment of Calving Paralysis
If calving paralysis is recognized early enough, vigorous measures can be adopted to prevent complications involving prolonged recumbency and potential damage to the adductor muscles or hip dislocation. The patient should be immediately transferred to a location 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 hind limbs should be tied together with a soft nylon strap fixed below the fetlocks. The limbs are restrained from spreading too far apart (no wider than 60–100 cm [approx 2–3 feet]). Anti-inflammatory agents (particularly glucocorticoids), such as dexamethasone (10 to 40 mg, IV or IM, every 24 hours), should be administered for the first 5 days. Another choice is flunixin meglumine (1.1 to 2.2. mg/kg, IV slowly, either once a day as a single dose or divided in two doses administered at 12-hour intervals for up to 3 days; the total daily dose should not exceed 2.2 mg/kg). Cattle that fail to show any improvement in the first 5 days of treatment have a poor prognosis.
