Page 512 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

VetBooks.ir Chapter 34

Sodium Chloride (Salt)

Larry J. Thompson

INTRODUCTION and correction of hyponatremia the reader is directed to
other references (Angelos and Van Metre, 1999).
Sodium chloride is often referred to as table salt, common
Salt is normally present in animal diets at 0.5% 1%.
salt, or just simply salt. Salt is an essential nutrient and
Production animals are often given free access to salt
can give an attractive taste to foods and feeds. It has been
blocks or mineral mixes as supplements to the diet.
stated that salt is the only mineral compound for which
Additional sources of salt may include high-saline ground
animals can truly develop a craving.
water, brine or seawater. The use of whey as a feed or to
Salt is a necessary nutrient for the health of animals produce wet mash can add dramatically to sodium intake.
and many nutrition texts divide it into separate require-
High concentrations of salt in the diet (up to 13%) have
ments for sodium (Na) and chloride (Cl). Daily require-
been used to limit feed intake of cattle. In general, animals
ments for salt will increase due to lactation, exertion and
can tolerate high concentrations of salt in the feed if they
increases in ambient temperatures. These same conditions
have free access to fresh water. Salt-deprived animals or
will also require an increase in water intake, which must
animals not acclimated to high-salt feeds can over-
always be considered in any discussion concerning salt
consume these feeds making the animal prone to hyperna-
intake.
tremia. Improperly formulated or improperly mixed feed
An excess of salt intake can lead to the condition known
can be an additional source of excess salt. Companion ani-
by various names including salt poisoning, hypernatremia,
mal exposures to excess salt have included the use of salt
sodium ion toxicosis, and water deprivation sodium ion
as an emetic (this practice is no longer recommended) and
intoxication. The last name in this list is the most descrip-
the consumption of various salt-containing objects includ-
tive, giving both the result (sodium ion intoxication)
ing rock salt and dough-salt mixtures. Dogs can develop
and the most common predisposing condition (water
hypernatremia during prolonged exercise and play in the
deprivation).
ocean surf, especially if insufficient fresh water is avail-
able. Hypernatremia has also been reported in animals
treated with improperly mixed oral electrolyte solutions
BACKGROUND
and remedies for diarrhea. Other causes of hypernatremia
Sodium is the main cation and chloride is the main anion in dogs can be found in Goldkamp and Schaer (2007).
in the regulation of osmotic balance in the extracellular Excess ingested salt can be irritating to mucosal sur-
fluid (ECF) of the body. Serum sodium concentration and faces and can result in anorexia, vomiting or diarrhea.
serum osmolarity are normally maintained under precise Ingested dietary salt is approximately 90% absorbed
control by homeostatic mechanisms involving thirst, anti- across the gastrointestinal tract. Ingestion of excess
diuretic hormone and renal reabsorption of filtered sodium. sodium on an acute basis can result in hypernatremia with
Normal reference ranges for serum sodium in adult animals this condition being variously termed direct sodium ion
(given in mmol/L) include porcine 135 150, bovine toxicosis, acute sodium ion toxicosis or acute hypernatre-
132 152, canine 141 152, feline 147 156, and equine mia. Clinical signs develop within 1 2 days. The more
132 146 (Kaneko et al., 1997). For sodium concentration common form of hypernatremia develops due to restricted
measurement, mmol/L 5 mEq/L and can be used inter- water intake and is termed indirect sodium ion toxicosis,
changeably. Hyponatremia is the result of the loss of chronic sodium ion toxicosis or chronic hypernatremia.
excess sodium compared to loss of water and can be the Clinical signs will develop over a period of 4 7 days but
result of a large number of disease processes and condi- the early changes may be missed or ignored. There are
tions. For a more complete explanation on the recognition several common reasons for restricted water intake
Veterinary Toxicology. DOI: http://dx.doi.org/10.1016/B978-0-12-811410-0.00034-9
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