Electrolyte and body fluid losses and inadequate intake of B Group vitamins.
Dr Caroline Foote
B.Sc.Agr (Hons) M.App.Sc. PhD
Under stressful conditions, two of the
factors most likely to cause sub-standard performance are:
1. Electrolyte and body fluid losses
2. Inadequate intake of B Group vitamins
Salkavite contains all essential vitamins associated with the B Group
and also provides all essential electrolytes that a horse in work loses
including sodium, potassium, calcium, magnesium, chloride, phosphate and
sulphate. It also contains Vitamin E and
Rutin due to their acknowledged
benefits to a horse subjected to extreme physical stress.
Electrolytes
About 75 to 80% of energy used in the body is given off as heat and this
energy utilisation, and therefore heat production increase greatly
during exercise. Without heat loss, the horse’s body temperature would
increase to a life-threatening level within 4 to 6 minutes (Carlson,
1983). The heat produced by the body, which during exercise is produced
primarily by the muscles, is transported by the blood to the skin and
the respiratory tract where it can be dissipated.
The evaporative cooling of sweat accounts for about 55 to 60% of heat
dissipation of the horse (Schott et al., 1990). The horse’s maximum
sweating rate is 10 to 15 litres per hour (L/hr) and is 6.5 to 9 L/hr at
endurance racing speeds. Thus, an extensive amount of body water is lost
during athletic performance by the horse resulting in up to a 50L sweat
loss, an amount equal to the horse’s total blood volume. If not
replaced, this would result in 7 to 11% dehydration or decrease in body
weight. From 12 to 15% dehydration is fatal. The effects of moderate
dehydration in horses are likely to be similar to those in people, in
which it has been shown that physical performance is impaired with fluid
losses that decrease body weight by only 2 to 4% (Snow and Vogel, 1987).
A dehydration-induced decrease in blood volume decreases blood flow to
both the muscles and the skin. Decreased blood flow to the skin
decreases heat dissipation both by decreasing heat transport to the skin
and by decreasing sweating, which increases the risk and onset of heat
stress or exhaustion.
Sweating results in the loss of not only water but also sodium,
chloride, potassium, calcium and magnesium and if excessive, may result
in a significant body deficit of these electrolytes. As the
concentration of sodium, potassium and chloride in the horse’s sweat is
higher than it is in their plasma, excessive sweating decreases their
concentration in the plasma (Figure 1; Deldar et al., 1982; Snow et al.,
1982).
Figure 1. Electrolyes in plasma and sweat (from Rose et al., 1979)
Particularly associated with exhaustion,
a significant hypokalemia (low concentration of potassium ions in the
blood) may occur. Decreased sodium concentrations may also occur due to
sodium losses, followed by partial replacement of the water deficit by
drinking. Hypochloremia (low concentration of chloride ions in the
blood) is the most consistent plasma concentration alteration in
profusely sweating horses. Plasma chloride concentration decreases from
a normal of 100 to 105mEq/L to 90 mEq/L or less are common, and in many
dehydrated, exhausted horses, the concentration is less than 80 mEq/L.
Calcium and magnesium concentrations also tend to fall with excessive
sweating.
Alkalosis, which occurs due to sweat-loss-induced hypochloremia,
increases protein binding of calcium. This and the loss of calcium in
sweat decrease the ionised calcium concentration. Hypocalcemia (low
concentration of calcium in the blood), which following extensive
sweating by the horse is generally accompanied by hypomagnesemia (low
level of magnesium in the blood), if sufficiently severe cases causes
anxiety, increased neuromuscular excitability resulting in muscle
fasciculations, increase muscular tension (particularly of the
extremities), ataxia, synchronous diaphragmatic flutter and hypocalcemic
tetany (Arnbjerg, 1980; Freestone et al., 1989).
In contrast to many nutrients, there are no body stores of water or
electrolytes other than those carried in the gastrointestinal tract. All
feeds are low in sodium and below that needed to meet the frequently
sweating horse’s needs. In fact many feeds contain even less sodium than
that needed to meet the non-sweating horse. Studies indicate that
electrolyte supplementation is necessary during training and competition
in hot ambient temperatures due to the quantity of sodium, potassium and
chloride calculated to be lost in sweat (McCutcheon and Geor, 1996) and
the decreased circulating potassium (Gottlieb-Vedi et al., 1996) during
exercise. Salkavite contains all these electrolytes that play an
importance role in muscle and nerve function, metabolism, acid-base and
fluid balance in the body including sodium, potassium, bicarbonate,
magnesium and calcium. The electrolyte levels in a 30g dose of Salkavite
are as follows:
Sodium 3600mg
Potassium 400mg
Calcium 2500mg
Magnesium 400mg
Chloride 3800mg
Phosphate 3400mg
Sulphate 1300mg
These minerals have other important functions in the body:
• Sodium is essential for normal growth and is critically involved in
normal nerve and muscle function, and carbohydrate digestion.
• Potassium has a nerve and muscular function as well as enzyme
activation, protein synthesis and carbohydrate metabolism
• Calcium is critically involved in bone growth, development and
maintenance and should be maintained in an appropriate balance to
phosphorus. Deficiencies result in bone deformities/skeletal weakness,
joint problems, and may lead to muscle weakness and conditions such as
“tying up”, and the “thumps” in heavily sweating, exhausted horses.
• 60% of magnesium is within bone, with calcium and phosphorus.
Magnesium functions as an electrolyte in muscle contraction, body fluids
and metabolic enzymes.
• Chloride is closely inter-related to sodium in acid-base balance and
extra-cellular fluid osmotic regulation. It is also contained in bile
and gastric acid.
• A deficiency in phosphorus can result in retarded bone formation,
retarded growth, poor appetite, infertility and poor conception and
lowered milk production.
These minerals are often inadequate in diets in working horses and the
addition of Salkavite will assist in correcting these deficiencies.
B Group Vitamins
High grain diets and hard physical work significantly increase a horse’s
daily requirements for B Group vitamins. B Group vitamins play a role in
the release of energy, and are needed for numerous essential body
functions. In diets consisting largely of cereal grains, protein meals,
chaff and dried hays, natural forms of B Group vitamins are generally in
short supply. Along with the electrolytes, B Group vitamins are also
lost in the sweat and consequently require replacement on a daily basis.
Each kilogram of Ranvet’s Salkavite provides the following levels of B
Group vitamins:
Thiamine (B1) 2819mg
Riboflavin (B2) 3404mg
Pyridoxine (B6) 157μg
Niacin 10445mg
Cyanocobalamin (B12) 14.34mg
Choline 5103mg
Folic Acid 816mg
Inositol 8775mg
• Thiamine (Vitamin B1) has a role in carbohydrate metabolism and nerve
transmission and a deficiency may result in reduced growth rate, loss of
appetite, abnormal heart beat, muscle tremours, incoordination and
stiffness in limbs, lung fluid build-up.
• Riboflavin (Vitamin B2) is involved in the metabolic function with two
co-enzymes used in aerobic energy production. There is little capacity
for the body to store Riboflavin so deficiency symptoms can develop
quickly on a deficient diet. Deficiency results in reduced growth rate,
dull dry coat and flaky skin loss and hindgut inflammation and
diarrhoea.
• Pyridoxine (Vitamin B6) is involved in energy production and blood
formation. Again, body storage is minimal and excess intake is
eliminated in the urine.
• Niacin is converted to nicotinamide in the gut lining and in the
tissues is involved in the metabolism of carbohydrates, fats and amino
acids to energy. There is a higher requirement for Niacin in exercising
horses.
• Cyanocobalamin (Vitamin B12) is involved in methionine synthesis,
folic acid activity and propionic acid to energy. It is widely used in
performance horses to avoid anaemia, aid the appetite, complement iron
supplementation and promote recovery after heavy worm burdens.
• Choline functions as a component of the neurotransmitter
acetylcholine, phatidyl choline (lecithin) and betaine.
• Folic Acid is associated with vitamin B12, which is necessary for
conversion to its active form. It is involved in blood cell production
in conjunction with vitamin B12.
• Inositol is suggested to aid in the metabolism of fats.
Vitamin E is an essential fat-soluble vitamin and has an anti-oxidant
activity to protect against oxidation of compounds in food and within
fats in membranes of muscle and body tissue. It is recognized as a
compound which dilates capillaries and preserves capillary walls, and is
also known to increase cardiac efficiency significantly, and reduce
lactic acid production. Supplementation at high dose rates enhances the
immune response and studies indicate that intakes of 2000IU daily or
three months improves track performance in racehorses. Vitamin E
supplementation may also be beneficial in preventing the occurrence of
exertional myopathy due to its effects on stabilising cell membranes.
Vitamin E is often deficient in commonly used ingredients used in equine
diets, particularly in diets designed for high performance.
Salkavite is intended as a base electrolyte replacer formulated for
daily supplementation to the diet, and has the added role of providing
supplementation of vitamins and minerals often deficient in diets of
horses used for performance. Additional electrolyte replacement, such as
Ranvet’s Electropaste is recommended to meet specific electrolyte needs
or replace excessive sweat and fluid losses.
References
Arnbjerg, J. (1980). Hypocalcemia in the horse. Nord. Vet. Med. 32,
207-211.
Carlson, G.P. (1983) Thermoregulation and fluid balance in the
exercising horse. In Equine Exercise Physiology. Edited by DH Snow.
Granter Ed., Cambridge, England, pp 291-302.
Deldar, A., Fregin, F.G., Bloom, J.C. (1982). Changes in skeletal
biochemical constituents of blood collected from horses participating in
a 50-mile endurance race. Am. J. Vet. Res. 43, 2239.
Freestone, J.F., Carlson, G.P., Harrold, D.R. et al. (1989). Furosemide
and sodium bicarbonate-induced alkalosis in the horse and response to
oral KCl or NaCl therapy. Am. J. Vet. Res. 50, 1334-1339.
Gottlieb-Vedi, M., Dahlborn, K., Jansson, A., Wroblewski, R. (1996).
Elemental composition of muscle at rest and potassium levels in muscle,
plasma and sweat of horses exercising at 20 degrees C and 35 degrees C.
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Harris, P.A., Snow, D.H. (1988). The effects of high intensity exercise
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Kohnke, J., Kelleher, F., Trevor-Jones, P. (1999). Feeding Horses in
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Lewis, L.D. (1995). Equine Clinical Nutrition: Feeding and Care.
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McCutcheon, L.J., Geor, R.J. (1996). Sweat fluid and ion losses in
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conditions: implications for ion supplementation. Equine Vet. J. Suppl.
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Rose, R.J. (1983). Cardiovascular effects of exercise. Eq. Vet. Data pp
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Schott, H.C. Hodgson, D.R. Naylor, J.R. et al. (1990). Thermoregulation
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Snow, D.H., Kerr, M.G., Nimmo, M.A. et al. (1982). Alterations in blood,
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Snow, D.H., Vogel, C.J. (1987). Equine Fitness: Care and Training of the
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