By Jenna Bayne, DVM
As the mercury starts to rise
with the approach of spring and summer, many riders look forward to an
opportunity to take their trusted mounts out on the trails, into the arenas,
and possibly even pursuing new avenues of fun and adventure, including riding on
the beach. Regardless of whether it is out at pasture or surfing the waves, the
most basic of husbandry practices should not be overlooked. This includes the
utmost importance of providing free access to clean, potable water for your
horse. Most of a horse’s water intake is through drinking (85%). Feed sources
(5%) and water generated through metabolic pathways (10%) make up the remainder
of total water intake. Water can be lost by three routes: in urine, in feces,
and as insensible losses (evaporation) across the skin and respiratory tract.
The maintenance water requirement for a 1000lb horse is approximately 27-30
liters per day or roughly 7-9 gallons per day. This water requirement is
further increased in exercise, as well as with an increase in ambient
temperature and humidity. If you plan to find yourself out on the trail or at
the beach, ensure that sources of fresh, potable water are available. Plan
ahead and haul in your own water. At home, ensure that automatic waters are
working properly; water troughs are full and cleaned out regularly. If water is
from a natural source, it may be advisable to have it tested for its quality
and total dissolved solids. Provide alternative sources of water in addition to
natural sources. Have multiple sources available – accidents do happen. Gates
get closed, troughs accumulate debris, and automatic waters can malfunction.
Providing limitless, fresh water sounds simple and it is. Its importance should
not be overlooked.
Though most commonly described in
cattle, water deprivation and salt toxicosis is a serious health condition that
potentially can occur in the horse. The disease occurs following
over-consumption of sodium chloride in rations or supplements, and can be
complicated by limited availability of drinking water, resulting in severe
dehydration. A similar sequence of events can also occur with simple water
restriction of sufficient duration, allowing the brain to adapt to the body’s
state of hypernatremia (high sodium levels in the blood) and hyperosmolarity.
Adaptive responses of the brain include the production of organic osmolytes
that counteract the osmotic imbalance; a new osmotic equilibrium is
established. Signs of toxicity are seen when rapid rehydration occurs. Given
free access to fresh water, water enters the brain cells, due to the increased
osmolytes within the cells, and the brain swells. Clinical signs include
reduced appetite and dehydration early followed by head pressing, ataxia,
blindness and seizures. Colic and diarrhea may also be present. Animals are
often found dead. The acute toxic dose of oral sodium chloride for cattle and
horses has been reported to be approximately 2.2g/kg of body weight. With water
restriction, the toxic dose of salt is considerably less, and poisonings have
resulted from ingestion of 0.9% NaCl in water-restricted cattle. Animals are
most susceptible to salt poisoning during the summer because of the increased
insensitive loss of water, for example sweating, that occurs at that time. If
you encounter an animal that has been deprived of water for a significant
amount of time, please consult a veterinarian, as it may require professional
management to rehydrate it safely.
As you head out to the many
adventures that await this summer, reflect on the five freedoms that are due to
our four legged friends: freedom from thirst, hunger and malnutrition; freedom
from discomfort; freedom from pain, injury and disease; freedom to express
normal behavior; and, freedom from fear and distress. Not every horse is made
for multiple day excursions on the trail, or may not find it relaxing to bask
in the sun at the beach. Common sense and knowing your animal goes a long way.
And, always ensure that you are prepared, including plenty of water for you
both.
You can contact Surgi-Care Center for Horses with any questions or
concerns at lkuebelbeck@surgi-carecenter.com
Literature:
Salt Poisoning. In: Smith BP, ed. Large Animal Internal
Medicine (3rd Ed). St. Louis: Mosby, 2002: 926-927.
Sodium Chloride Toxicosis. In: McGavin MD and Zachary JF
(editors). Pathologic Basis of Veterinary Disease (4th Ed). St.
Louis: Mosby, 2007: 915-916
Five Freedoms. Farm Animal Welfare Council. http://www.fawc.org.uk/freedoms.htm