Vitamin deficiencies were first recognized in dogs about 80 years ago, and played an important role in the discovery and differentiation of vitamins A, D and niacin (NRC, 2006).
Vitamin deficiencies were first recognized in dogs about 80 years ago, and played an important role in the discovery and differentiation of vitamins A, D and niacin (NRC, 2006). They were also used for the assay of human foods for niacin. Unfortunately, much of the research on vitamins in dogs, and to a lesser degree in cats, was done with the objective of understanding the function of the vitamin, rather than of determining a requirement for that species. In addition, the preponderance of the research was done in the early and middle parts of the last century, often when purified vitamins and modern analytical tools were not available (NRC, 2006).
Table 1-1 lists vitamin requirements for dogs (NRC, 2006) and Table 1-2 lists those for cats (NRC, 2008). 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 requirements, compared to other monogastric species (e.g., swine). Cats show a specialization consistent evolutionary with the influence of a strict carnivorous diet, while diets of dogs show more variety. Cats lack the ability to synthesize the amino acid taurine, convert linolic acid to arachidonic acid and cope with high levels of dietary carbohydrate. Unlike other domestic animals, cats are carnivores and this influences both their nutritional requirements and food preferences. A cat diet must not only be nutritious, but also highly palatable (Zaghini and Biagi, 2005). In relation to vitamins, cats cannot synthesize niacin from tryptophan or convert carotene to vitamin A. Unlike man and most animal studied, 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 in organ meats) will often provide more bioavailable vitamins for companion animals.
The early NRC vitamin publications for dogs (NRC 1962, 1972, and 1974) and cats (NRC 1962, 1972, and 1978) gave one recommendation to apply to all classes of that species. 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. Most nutritionists usually consider NRC requirements for vitamins to be close to minimum requirements sufficient to prevent clinical deficiency signs, and they may be adjusted upward according to experience within the industry in situations where a higher level of vitamins is needed. Prior to the current NRC requirements for dogs and cats, the previous NRC’s for vitamin recommendations for dogs (NRC, 1985) and cats (NRC, 1986) had an emphasis on growth for these species. The current NRC (2006) requirements for dogs and cats attempt to list requirements as minimal requirements, adequate intake, recommended allowance and safe upper limit. Values for the safe upper limit are only for vitamins A and D. For both dogs and cats, NRC recommendations are for three catagories: Growth after weaning (puppies or kittens), adult maintenance and late gestation-peak lactation. The minimal allowances for many of the vitamins are similar to those proposed by the previous NRC (1985, 1986).
An additional source of vitamin requirements for dogs and cats is from the Association of American Feed Control Officials (AAFCO). In the past, there has been a controversy between NRC and AAFCO on format for presenting requirements. In the AAFCO 2007 dog vitamin recommendation, figures are for all life stages. For cats, recommendations are in two categories, growth and reproduction and for maintenance (Table 1-3).
Over the years, the number of vitamins recommended by NRC for dogs and cats has increased and vitamin requirement values have been revised. For dogs the number of vitamins recommended by the NRC has increased from 10 in 1962 to 13 in 2006 and for cats from 9 in 1962 to 13 in 2006. In the future, L-carnitine may be listed as a requirement. Supplementation of L-carnitine has been beneficial to other species and recently under special circumstances a value for dogs and cats (Blanchard et al., 2002; Sanderson, 2006; Neumann et al., 2007).
Approximately 75% of non-accidental causes of death in dogs are cancer, kidney failure and heart disease. Studies have utilized various supplements which have included vitamin E, L-carnitine, CoQ10 and B-vitamins as therapy treatments for heart disease in dogs (Dove, 2001). 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 (Stowe et al., 2006). 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 pet food market contains a wide array of commercial foods for dogs and cats. Some of these foods are formulated to provide adequate nutrition throughout a pet’s lifespan, while other foods have been marketed specifically for a particular stage of life or a specific disease state. This large selection of commercial foods, combined with the pet owners increased awareness of their pets health, has resulted in a greater demand for high-quality food ingredients and continued growth of the pet food industry. Providing adequate quantities of high quality vitamins in pet foods helps insure optimum health of the dog and cat populations.
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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