Hypokalemia in Adult Cattle

Hypokalemia is common in adult cattle with prolonged inappetence (> 2 days) or in those receiving more than one injection of corticosteroids that have mineralocorticoid activity, such as isoflupredone acetate, because mineralocorticoid activity enhances renal and GI losses of potassium.

Hypokalemia occurs commonly in inappetent adult cattle, particularly in lactating dairy cows, because of the additional loss of potassium in milk. Hypokalemia is extremely rare in healthy adult ruminants that have adequate dry-matter intake.

• Generalized muscle weakness and depression

• Decreased GI motility

• Serum or plasma potassium concentration < 2.5 mmol/L

Cattle with hypokalemia have generalized muscleweakness, depression, and muscle fasciculations. Severely affected animals are unable to stand or lift their head off the ground.

Serum biochemical analysis is required to confirm a suspected diagnosis of hypokalemia. A serum potassium concentration < 2.5 mmol/L reflects severe hypokalemia (1). Most affected animals are weak; some are recumbent.

A serum potassium concentration of 2.5–3.5 mmol/L reflects moderate hypokalemia, and some moderately affected cattle are recumbent or appear weak, with depressed GI motility.

In addition to measuring serum potassium concentration, measuring serum concentrations of sodium, chloride, calcium, and phosphorus, as well as serum CK and AST activities, can be very helpful in guiding treatment of hypokalemia. Aciduria might be present in response to a marked decrease in urine potassium concentration.

• Oral administration of potassium chloride (KCl)

• Increase in feed intake

Oral potassium administration is the treatment of choice for hypokalemia. Inappetent, lactating dairy cattle should be treated for 3–5 days with 100–150 g of feed-grade KCl twice at a 12-hour interval (2). The KCl should be placed in gelatin boluses or administered by ororuminal intubation (3).

Higher daily doses of KCl (up to 1 g/kg body weight) have been reported (1). However, these higher doses can lead to diarrhea, excessive salivation, muscular tremors of the legs, and excitability, and they should be administered only with frequent monitoring.

IV administration of potassium is rare and used only for the initial treatment of recumbent ruminants with severe hypokalemia and rumen atony, because the immediate and potentially excessive availability of potassium in the bloodstream is much more dangerous, and IV treatment is generally more expensive than oral treatment.

The most aggressive IV treatment protocol for hypokalemia is an isotonic solution of KCl (1.15%), which should be administered at a maximum K⁺ delivery rate of 0.5 mmol/kg/h (1). Higher rates of potassium administration risk inducing hemodynamically important arrhythmias, including premature ventricular complexes that can lead to ventricular fibrillation and death.

Given that potassium is absorbed from the diet, restoring proper dry matter intake and offering highly palatable feed sources is important for regaining potassium balance.

Oral administration of potassium is a mandatory component of fluid and electrolyte administration to inappetent cattle. Ensuring adequate dry-matter intake is the best method to prevent hypokalemia in adult cattle.

• Potassium. eClinpath, Cornell University College of Veterinary Medicine.

1. Sattler N, Fecteau G. Hypokalemia syndrome in cattle. Vet Clin North Am Food Anim Pract. 2014;30(2):351-357. doi:10.1016/j.cvfa.2014.04.004

2. Goff JP. Macromineral disorders of the transition cow. Vet Clin North Am Food Anim Pract. 2004;20(3):471-494. doi:10.1016/j.cvfa.2004.06.003

3. Sweeney RW. Treatment of potassium balance disorders. Vet Clin North Am Food Anim Pract. 1999;15(3):609-617. doi:10.1016/s0749-0720(15)30166-3