Cold-weather warfare
Trench foot is a medical condition caused by prolonged exposure of the feet to damp, unsanitary, and cold conditions at temperatures as warm as for as few as 13 hours. Exposure to these environmental conditions causes deterioration and destruction of the capillaries and leads to morbidity of the surrounding flesh. Affected feet may become numb, affected by erythema (turning red) or cyanosis (turning blue) as a result of poor blood supply, and may begin emanating a decaying odour if the early stages of necrosis (tissue death) set in. As the condition worsens, feet may also begin to swell. Advanced trench foot often involves blisters and open sores, which lead to fungal infections. If left untreated, trench foot usually results in gangrene, which may require amputation. If trench foot is treated properly, complete recovery is normal, though it is marked by severe short-term pain when feeling returns. Trench foot affected tens of thousands of soldiers engaged in trench warfare in World War I. Keeping feet warm and dry, or at least changing into warm and dry replacement footgear, is the best way to avoid trench foot.
Horse grooming
The most basic form of hoofcare is cleaning, or "picking out the feet". A hoof pick is used to remove mud, manure, and rocks from the sole of the hoof. Removal of mud and manure helps to prevent thrush, a common hoof ailment which in very severe cases may cause lameness, and the removal of rocks helps to prevent stone bruises. In the winter, hoof picking also provides the chance to remove packs of snow from the horse's hooves, which can cause uncomfortable "snowballs". Additionally, when the hoof is cleaned, it can be visually inspected for problems such as puncture wounds due to a nail (which has the potential to be very serious if left untreated).
All crevices of the hoof are cleaned, particularly the sulci between the frog and the bars, as those areas are most likely to trap rocks or other debris, and also are the most common area to develop thrush. It is best to work the hoof pick from heel to toe, so to avoid accidentally jabbing the horse's leg, the frog of the hoof, or the person using the pick. When picking the feet, the groom stands at the horse's side, facing the tail of the horse, then slides his or her hand down the horse's leg. If the horse was not trained to pick up its foot when a person runs their hand to the fetlock and lifts lightly, most horses will pick up their feet if the tendons behind their cannon bone are squeezed. Some horses, particularly draft breeds, may be trained to pick up their feet to pressure on their fetlock.