Chapter 4 The Role of Nutrition in Canine Performance and Rehabilitation 85since the water‐soluble vitamins have large
margins of safety. Vitamin C is the most abun-
dant water‐soluble antioxidant found in the
mammalian body, and dogs sustain their
requirements through hepatic synthesis; how-
ever, dogs may not synthesize as much as other
species (Chatterjee et al., 1975). Lack of high
hepatic synthesis taken with the fact that serum
ascorbic acid concentrations decreased more
than 50% after an undefined race distance of 1.5
hours duration has led experts to speculate that
supplementation may be useful (Kronfeld et al.,
1989). Similar decreases have been observed
in unsupplemented exercising Greyhounds
(1.8–2.8 mg/L; Marshall et al., 2002; Scott et al.,
2002). Supplementation of 1 g of ascorbic acid
per day returns serum concentrations closer to
what is considered a normal baseline concentra-
tion (5–6 mg/L), but similar supplementation in
Greyhounds for 4 weeks resulted in slower rac-
ing times by 0.3 km/h. Therefore vitamin C sup-
plementation, having shown no definitive
benefit for athletic canines, is not routinely rec-
ommended at the time of writing, particularly
for racing Greyhounds.
Fat‐soluble vitamins (A, D, E, and K) have
smaller margins of safety and are more con-
cerning. Sufficient vitamin K is synthesized by
indigenous bacteria in the gastrointestinal tract
of normal dogs. Vitamin A may be of more
concern if organ meats are used as a portion of
the diet, and they should not exceed 15% of any
meat mix used to feed. This is due to the high
concentration of vitamin A found in liver.
Excess vitamin A consumption may manifest as
poor coat quality, perturbed bone mineraliza-
tion and hepatic damage. Dogs, as a species, are
very tolerant to high dietary vitamin A (Morris
et al., 2010). Vitamin D is also found in organ
meats, particularly liver, making a small
amount of organ meat desirable if using meat
as part of the diet. Many commercial dog foods
have at least twice the cholecalciferol needed in
the diet, so with the increased energy consump-
tion required by athletic dogs, the amount of
cholecalciferol consumed is usually adequate.
Vitamin E is sufficient in commercial pet
food, and most manufacturers add significantly
more than the requirements, making vitamin E
deficiency unlikely. Deficiency has been
observed in hunting dogs fed an all meat diet
and was associated with retinal degeneration
(Davidson et al., 1998). Vitamin E has been
examined extensively in endurance sled dogs,
and low serum vitamin E was associated with
an increased risk of being dropped from the
Iditarod (race event). Additionally, serum
vitamin E dropped after a single day of endur-
ance activity in two separate studies (Kronfeld
et al., 1989; Piercy et al., 2001a, 2001b). Increased
serum creatine kinase was never directly corre-
lated to low vitamin E concentrations in dogs
exhibiting exertional rhabdomyolysis (Piercy
et al., 2001a). Similarly, decreased serum vita-
min E concentrations have been observed in
Greyhounds racing 500 m (Scott et al., 2001).
These finding suggested that supplementation
might be beneficial. A consensus statement
made by the Iditarod trail committee in 1996
stated that endurance sled dogs should be sup-
plemented with 400 IU of vitamin E daily dur-
ing training and racing in an effort to reduce
exertional rhabdomyolysis. However, there
appears to be no decrease in the incidence of
exertional rhabdomyolysis (Iditarod Veterinary
Trail committee, personal communication).
More compelling evidence for not supplement-
ing vitamin E was provided when Scott and
colleagues and Hill and colleagues showed that
although supplementing with 100 to 1000 IU
raised serum tocopherol concentrations, dogs
receiving 1000 IU had slowed racing times (Hill
et al., 2001a; Scott et al., 2001). Tocopherol
supplementation is not recommended in canine
athletes as long as they are being fed sufficient
complete and balanced dog food, while supple-
mentation should be considered for dogs being
fed nontraditional diets (primarily meats)—
vitamin E (200–400 IU for a typical athletic 20‐
to 40‐kg dog)—to prevent deficiency.Table 4.4 Essential water‐soluble and fat‐soluble
vitamins
Water‐soluble vitamins Fat‐soluble vitaminsThiamin (B1) Vitamin A
Riboflavin (B2) Vitamin D
Niacin (B3) Vitamin E
Pantothenic acid (B5) Vitamin K
Pyridoxine (B6)
Folic acid
Cobalamin (B12)
Choline