Perhaps it has been a harder than a normal trail ride, maybe you have a heavily lactating mare, maybe your horse has had diarrhea for awhile, but all of a sudden you realize your horse seems to be hiccuping. His whole body is being racked with mild rhythmic spasms. There may be also signs of stiffness and depression. The condition is called thumps and is due to changes in blood ph and/or blood calcium concentrations. It may be a mild transient problem but it may indicate a life threatening electrolyte imbalance in the blood. This report discusses causes, diagnosis, treatment, and prevention of hypocalcemia in horses.

Thumps look like a hiccuping horse. The diaphragmatic (phrenic) nerve is discharging abnormally resulting in the diaphragmatic muscle jumping in concert with each heart beat. The condition is most frequently seen in exhausted horses and indicates stress on the electrolyte system of a horse. It is seen less frequently in heavily lactating mares usually around birthing.

If the hypocalcemia is severe enough, you may also see: a stilted gait from muscle stiffness, muscle fasiculations, rapid heart rates, depression, and colic may be seen.