Downer cow syndrome

downer cow syndrome is a complication of periparturient hypocalcemia. Recumbency in cattle is caused by numerous metabolic, traumatic, infectious, degenerative, and toxic disorders. If treatment of the underlying cause of recumbency is not successful and cattle are unable to rise for >24 hr after initial recumbency, they may develop a secondary recumbency from pressure damage to muscles and nerves, often termed “downer cow syndrome. Calving paralysis after dystocia may also result in recumbency due to traumatic injury to tissues and nerves inside the pelvic cavity. Regardless of the initial cause of recumbency, all cattle develop pressure-induced damage to muscles and nerves of the pelvic limbs, especially when lying on a hard surface. The hindlimb muscles of the leg the animal is lying on are compressed between the bones and the skin by the physical pressure from the weight of the recumbent cow. The positioning of the hindlimbs may indicate the cause of the recumbency. Limbs splayed out behind the animal may indicate obturator nerve paresis or paralysis, hip dislocation, or fracture of the femur or tibia. Fracture should be suspected whenever the upper limb is extended sideways in such a manner that a crease is formed in the skin.

Blood samples are not usually taken when treating routine cases of hypocalcemia. However, hypocalcemia, hypophosphatemia, and hypokalemia should be assumed to be present in all recumbent cattle, and determination of the biochemical status of cattle unresponsive to calcium therapy frequently helps guide treatment and prognosis. Hypokalemia and hypophosphatemia are commonly quoted causes of creeper cows (cows able to crawl but unable to stand). Alert downer cows may have normal serum concentrations of calcium, potassium, magnesium, and phosphorus. Downer cows have increased serum CK, AST, and LDH; cows that do not recover have higher serum AST and CK activities than cows that do recover. Increased serum CK activity is a specific indicator of muscle damage; however, CK activity peaks shortly after the start of muscle damage and declines noticeably within 4 hr. For this reason, increased serum AST activity is the best prognostic indicator in recumbent cattle, with higher AST activities indicating a poorer prognosis. In cattle with severe muscle damage, the urine may contain myoglobin as well as higher than normal concentrations of protein.

Downer cows are often hypocalcemic. If an apparently hypocalcemic cow does not respond to calcium therapy, potassium, phosphorus, and magnesium should be given as additional treatments pending results of laboratory tests. Monitoring blood mineral status is an important part of downer cow management.

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