Transport tetany is more appropriately designated a "management syndrome" versus a specific disease, with multiple management risk factors leading to tetany due to hypocalcemia, hypomagnesemia, or both. Transport tetany typically occurs in cows and ewes in late pregnancy, after the stress of prolonged transport. It also occurs in lambs transported to feedlots and in cattle and sheep transported to slaughter. Crowded, hot, poorly ventilated transport vehicles (railroad cars or trailers) with minimal or no access to feed or water seem to predispose animals to the condition; however, prolonged travel by foot is also a risk factor. The disease is characterized by recumbency, gastrointestinal stasis, and coma, and is generally fatal.
Although cows in late gestation are most commonly affected, the disease also occurs in cows that have recently calved, as well as in bulls, steers, and dry cows. Risk factors include heavy feeding before shipment, deprivation of feed and water for >24 hours during transit, exercise immediately after transport, and exposure to hot environmental conditions.
Clinical signs of transport tetany in cattle may occur while in transit or up to 48 hours after arrival. Early clinical signs include restlessness and excitement, trismus, and grinding of teeth. A staggering gait may be seen, and later, if recumbent, affected cattle often demonstrate paddling of the hind legs. Rumen hypomotility and gastrointestinal stasis occur, and animals become completely anorectic. Tachycardia and rapid, labored respiration may develop. Abortion may be a complication. Moderate hypocalcemia and hypophosphatemia may occur in cattle. Cattle that do not recover gradually become more obtunded, leading to coma and death within 3–4 days.
In sheep are hypocalcemia and hypomagnesia may be present; however, some affected animals have a normal serum biochemical profile. No specific lesions are found at postmortem examination other than lesions associated with prolonged recumbency, most commonly ischemic muscle necrosis. In lambs, early signs include restlessness, staggering, and partial hind limb paralysis followed by lateral recumbency. Death can occur rapidly or after 2–3 days of recumbency. In lambs, mild hypocalcemia may be noted. Prognosis for recovery is fair even with treatment. Diagnosis is based on recent history of transport or forced, prolonged exercise followed by development of characteristic clinical signs.
Some animals respond to treatment with combinations of parenteral calcium, magnesium, and glucose. IV injections of calcium borogluconate (25% solution at 400–800 mL per cow or 100 mL per ewe) or calcium borogluconate with magnesium sulfate (5% solution, same volumes) can be administered slowly. A dose of 50 mL per day, SC, can be administered to affected lambs in feedlots. Repeated injections may be warranted, however failure to respond is common and most likely due to concurrent muscle necrosis. Additional treatment considerations include intravenous administration of large volumes of isotonic fluids such as lactated Ringer’s solution. Animals should be offered good quality feeds with high concentrations of calcium and magnesium and lower concentrations of potassium, such as alfalfa hay, fresh water, and soft bedding with good footing underneath. Sedation may be necessary in some cases.
It is important to decrease animal stress via gentle handling techniques, appropriate, well-designed handling equipment, avoiding overstocking of trailers, and transporting animals during the cooler times of day. If prolonged transport times of cows or ewes in advanced pregnancy is unavoidable, animals should be fed good quality hay such as alfalfa several days before shipment, then provided adequate feed, water, and rest periods during transport. Administration of ataractic agents (unless transport is to slaughter) such as promazine hydrochloride before loading is recommended for extremely nervous animals. Upon unloading at the destination, animals should be allowed limited access to water for the first 24 hours and minimal exercise for 2–3 days.
