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Table 1
lists vitamin requirements for dogs (NRC, 1985; AAFCO, 1992) and
Table 2 lists those for cats (NRC, 1986; AAFCO, 1992). Despite the lack of
precise information on the requirements of many vitamins for dogs and cats and
the almost complete lack of vitamin bioavailability of important pet foods,
there is a baseline of information on these important nutrients. Apparently
dogs have some general similarities in vitamin requirements, compared to other
monogastric species (e.g., swine). However, cats show a specialization
consistent with the evolutionary influence of a strict carnivorous diet, while
diets of dogs show more variety. Cats lack the ability to synthesize taurine,
convert linoleic acid to arachidonic acid and cope with high levels of dietary
carbohydrate. In relation to vitamins, cats cannot synthesize niacin from
tryptophan or convert carotene to vitamin A. Unlike man and most animal
studies, both dogs and cats have a nutritional requirement for vitamin D as
insufficient quantities are synthesized in the skin from UV irradiation (How
et al., 1994a, b; 1995). It is concluded that the cat, unlike the dog, is an
obligate carnivore and is dependent on at least some animal-derived materials
in its diet. Diets that do provide more animal protein (particularly organ
meats) will likewise often provide more bioavailable vitamins for companion
animals.
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Approximately 75% of nonaccidental causes of death in dogs are cancer, kidney
failure and heart disease. Data are accumulating which suggest that many
"age-related" diseases, such as cancer and heart disease, are caused in part
by free radical damage. Free radicals can be generated by stress factors
including weaning, housebreaking, fast gains and disease conditions.
Supplementing the pet diet with antioxidants such as vitamin E, vitamin C and
beta-carotene can prevent or reduce the negative impact of free radical damage
and thereby increase length and quality of life for companion animals.
Impellizeri et al. (1998) tested a multivitamin antioxidant (Proanthozone®) as
a treatment for osteoarthritis secondary to hip dysplasia in dogs and found
improvement over controls.
The dynamics of vitamin nutrition for dogs and cats are demonstrated by the
changes in the NRC vitamin requirements that have occurred since 1962 (
Figure 1 and
Figure 2). For some of the years of publication for dogs, vitamin K and
biotin (1972) were required, but for other years of publication they were left
out. Over the years vitamins A and E have been decreased while requirements
for vitamin D, vitamin B12, riboflavin, niacin, pantothenic acid, choline,
folic acid, thiamin and vitamin B6 have been increased. From the 1985 NRC,
vitamin D was increased by 153% and pantothenic acid by 350% over the listed
requirements for the 1963 NRC.
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The cat NRC publications (
Figure 2) have changed considerably from 1962 to 1986; in 1962 nine
vitamins were required, but four additional vitamins were listed by 1985
(Vitamin B12, vitamin K, folic acid and biotin). Of the original nine vitamins
in 1962, requirements for vitamins A, D, E, riboflavin, niacin, pantothenic
acid and choline had decreased in 1986 while requirements for thiamin and
vitamin B6 had increased.
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The most recent NRC publications for dogs (NRC, 1985) and cats (1986) should
be considered as minimum requirements and do not include a margin of safety.
Earlier NRC requirement publications did include margins of safety to
compensate for vitamin losses during feed processing and storage and for other
factors influencing the vitamin needs of pets (so-called influencing factors).
Later NRC publications, however, recognized that the influencing factors vary
considerably from location to location. Therefore, the margins of safety were
excluded, and the NRC vitamin requirements were reduced to minimum values.
This gave the nutritionist the flexibility to use these minimum requirement
values as a base, arrive at margins of safety, and adjust vitamin allowances
to compensate for the influencing factors occurring in individual operations.
There is considerable controversy over the more recent nutrient requirements
for dogs (NRC, 1985) and cats (NRC, 1986). The Association of American Feed
Control Officials (AAFCO) established new nutrient profiles for dogs and cats
beginning in 1992 (AAFCO, 1992). Previously, AAFCO used the NRC to set the
minimum amounts of nutrients required in a "complete balanced" food for dogs
and cats. However, the last NRC publication available in a format usable by
AAFCO for dogs was published in 1972. The NRC (1985) for dogs is based on
purified diets and the presumption of 100% bioavailability. Practical
ingredients with an included "safety factor of approximately 20% extra"
provided the basis for the 1972 revision. The 1985 revision was based on
isolated tests with experimental purified diets in which nutrients were nearly
100% available, and these data could not be easily translated into the
contributions by normal ingredients used commercially in dog foods (Dzanis,
1991).
There are some differences in the AAFCO profiles compared to the NRC
publications. There are two separate AAFCO profiles (one for growth and
reproduction and one for adult maintenance), instead of just one for all life
stages. AAFCO recommendations note maximum levels of intakes of vitamins A, D
and E for dogs and vitamins A and D for cats. Considerations were made to
account for differences in bioavailability of nutrients in commonly used
ingredients. Thus, the profiles will be of practical usefulness to formulators
of commercial dog foods. Similarly, this Roche reference resource includes
margins of safety in its recommendations to account for differences in
bioavailability and other factors influencing vitamin requirements.
The dynamics of vitamin allowances (amounts fed) have paralleled the dynamics
of vitamin requirements (minimum amounts needed). An allowance today may
become a requirement tomorrow. To assure that dogs and cats are fed the
amounts of vitamins needed to prevent deficiencies and allow optimum
performance, the vitamin fortification levels in pet diets should be reviewed
and/or adjusted periodically—in accordance with the latest production,
processing and storage methods, location conditions, and vitamin nutrition
knowledge.
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