Page 258 - Small Animal Clinical Nutrition 5th Edition

Feeding Young Adult Dogs 263

VetBooks.ir energy needs must subsequently be evaluated by body condition fat foods have decreased energy density. Fiber is a poor source
of energy for dogs; thus, as the fiber content of foods increases,
assessment and adjusted as needed for individual dogs. It has
been estimated that sled dogs may require more than 10,000 energy density decreases. Dietary fiber reduces the energy den-
kcal/day (41.8 MJ/day) (up to 15 x RER) to maintain body sity of the food and helps promote satiety (Chapters 5 and 27).
weight under racing conditions (Hinchcliff et al, 1997). Active Inclusion of fiber in foods may therefore help maintain ideal
young adult dogs should be fed a food with an energy density body weight in dogs fed free choice. In pet foods, fiber is listed
range of 3.5 to 4.5 kcal/g dry matter (DM). The energy densi- as crude fiber, which is an imprecise measure because most sol-
ty range of foods for inactive/obese prone dogs should be lower uble fiber is omitted. A better measure would be total dietary
(3.0 to 3.5 kcal/g DM). fiber; however, regulations only permit declaration of crude
fiber because no method for determination of total dietary fiber
Fat and Essential Fatty Acids is yet officially recognized for pet foods. It is difficult to deter-
Fats are an excellent source of energy, but the real requirement mine the optimal concentration of crude fiber in a complete
for fat is to supply essential fatty acids (EFAs). In addition, fat food for dogs; however, up to 5% DM seems adequate. Obese-
serves as a carrier for the absorption of fat-soluble vitamins (i.e., prone dogs may benefit from at least 10% DM crude fiber and
A, D, E and K). Linoleic and α-linolenic acids are considered DM fat should be restricted to between 7 to 10%. Foods that
essential because dogs lack the enzymes to synthesize them are low in fat and high in fiber tend to have the lowest energy
(Watkins, 1997). Linoleic acid (18:22n-6) is the parent fatty density and are recommended for obese-prone dogs.
acid of the omega-6 (n-6 series), as is α-linolenic acid for the
omega-3 (n-3) series. EFAs have structural functions in cell Protein
membranes and are precursors of eicosanoids such as The amount of protein in commercial foods for healthy dogs
prostaglandins, thromboxanes and leukotrienes (NRC, 1985a; varies widely (15 to 60% DM). After the amino acid require-
Lands, 1991). Linoleic acid deficiency results in two primary ments are met for an individual animal, addition of more pro-
skin defects: hyperproliferation and increased permeability to tein provides no known physiologic benefit.This fact often runs
water (Ziboh and Miller, 1990). The epidermal water barrier contrary to the popular belief that more protein is better. Also,
consists of lamellae of lipids (sphingolipids) in the stratum the addition of extra protein in commercial dog foods is some-
corneum of the epidermis. Linoleic acid is incorporated into times marketed as necessary for carnivores and misrepresents
the ceramide-portion of sphingolipids where it provides the the fact that dogs are omnivores. Excess dietary protein, above
specific characteristics needed for barrier function (Ziboh and the amino acid requirement, is not stored as protein, but rather
Miller, 1990). Additionally, linoleic acid plays a role in fertility is deaminated by the liver. Subsequently, the kidneys excrete the
(Lands, 1991). Ensuring an adequate intake of EFAs is key to by-products of protein catabolism and the remaining keto acid
maintaining normal skin and coat quality. analogues are used for energy or stored as fat, or as glycogen in
Whether omega-3 fatty acids are essential is less certain some cases.
because of the inability of omega-3 fatty acids to support all The subject of whether excess dietary protein contributes to
of the physiologic functions that are supported by omega-6 the progression of subclinical kidney disease has yet to be
fatty acids (Lands, 1991). Nevertheless, a source of dietary resolved (Chapter 37). Studies in people suggest that protein
omega-3 fatty acids is recommended (Watkins, 1997). The restriction may help slow progression of kidney disease (Mitch
minimum recommended allowance for dietary eicosapen- et al, 1998; NKF, 1998). In addition to any potential aggravat-
taenoic plus docosahexaenoic acids is 0.044% DM (NRC, ing effects excess dietary protein may have on subclinical kidney
2006). Omega-3 fatty acids may moderate excessively vigor- disease, foods high in protein also tend to contain high levels of
ous actions of omega-6-derived eicosanoids (Lands, 1991) phosphorus. As mentioned above, excess dietary phosphorus
and are of value in the management of certain diseases accelerates the progression of kidney disease in dogs. Minimum
(Chapters 30, 32, 34, 37). The minimum recommended protein requirements for healthy adult dogs eating high-quality
allowance for dietary fat in foods for normal, healthy adult protein have been determined using nitrogen balance and
dogs is 8.5%, with at least 1% of the food as linoleic acid endogenous nitrogen excretion. A more reliable estimate based
(DM) (NRC, 2006). Depending on the type/source of fat, on endogenous nitrogen excretion equates to a minimum
increasing the amount of fat in foods increases palatability requirement of 1.7 g metabolizable protein/BW kg 0.75 for an ideal
and EFA levels; however, energy content also increases. The protein (NRC, 1985a; Kendall et al, 1982; Schaeffer et al, 1989).
recommended range of fat for foods intended for young adult When protein of average quality is used (biologic value of about
dogs is 10 to 20% (DM). Lower levels of dietary fat are rec- 70), the minimum requirements are increased to 2.1 to 2.5 g
ommended for obese-prone adult dogs (7 to 10% DM). digestible protein/BW kg 0.75 (Gesellschaft, 1989b).
The minimum crude protein content of food depends on
Fiber digestibility and quality. For example, if the digestibility of an
The levels of dietary fat and fiber are important determinants average quality protein is 75%, then about 12% DM crude pro-
of a food’s energy density. Fat provides more than twice as tein is adequate.Foods containing less than 12% DM crude pro-
much energy on a weight basis than carbohydrate or protein. tein must be of higher biologic value. Biologic value becomes
High-fat foods have increased energy density; conversely, low- less important for healthy adult dogs if foods contain crude pro-