Page 103 - Small Animal Clinical Nutrition 5th Edition

Macronutrients 103

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Figure 5-20. Lipoprotein metabolism. See text for details. Key: LDL = low-density lipoprotein, HDL = high-density lipoprotein, VLDL = very
low-density lipoprotein, LCAT = lecithin cholesterol acyltransferase.

Addition of fish oil to cat foods reduced cartilage degradation Lipid Excess
and supported mobility. Geriatric cats (older than 12 years of Increased dietary lipid is often associated with increased ener-
age) fed foods supplemented with fish oil had reduced bio- gy intake, because increasing the dietary lipid content of a
markers of cartilage damage and enhanced mobility compared food is nearly always associated with an increase in the food’s
to cats fed food without fish oil. caloric density. This relationship results from increased avail-
able energy. Changes in body composition result from
Fat-Soluble Vitamin Absorption changes in energy balance. Energy intake may be influenced
Dogs and cats have a “requirement” for lipid to enhance absorp- by dietary fat; however, energy balance controls adiposity not
tion of the fat-soluble vitamins A, D, E and K. Dietary fat pro- the lipid intake.
vides a physical environment in the gut that enhances absorp- Increasing the fat concentration of foods generally enhances
tion of fat-soluble vitamins. This requirement is in the range of palatability for dogs and cats. Fatty acid composition is an
1 to 2% of the food and is not specific for any type of fat. important aspect of palatability and influences acceptance
through flavor and mouth feel. Dietary fat also influences sub-
Lipid Requirements sequent food selection (Mullen and Martin, 1990), an effect
Although not required for health,calories supplied by fat can be mediated through serotonin, a neurotransmitter involved in
more beneficial than those provided by carbohydrate or protein. control of food intake (Mullen and Martin, 1992).
In cases of high-energy demand, the energy concentration of
the food can limit total caloric intake. When the total bulk of Interactions with Other Nutrients
the food is a limiting factor, increasing dietary fat allows for High dietary fat concentration requires increased antioxidant
increased energy consumption. Increased aerobic capacity dur- protection, such as added vitamin E. In the absence of adequate
ing exercise is supported by increased fat consumption because antioxidants, dietary lipids will become rancid (Chapter 8).
of the enhanced use of fat calories when compared with calo- Rancidity adversely affects the animal through reduced palata-
ries from carbohydrate (Chapter 18). bility, reduced vitamin activity and possibly subsequent oxida-
tion of body fat. Because polyunsaturated omega-3 fatty acids
Lipid Deficiency are more susceptible to peroxidation than are most omega-6
Deficiencies of fatty acids impair wound healing, cause a dry fatty acids, increased amounts of antioxidants are needed in
lusterless coat and scaly skin and change the lipid film on the foods high in omega-3 fatty acids.
skin, which may predispose the animal to pyoderma (Chapter Excessive dietary unsaturated fat in conjunction with inade-
32). If deficiency persists, alopecia, edema and moist dermatitis quate antioxidants may result in pansteatitis or “yellow fat dis-
may develop. Lesions of moist dermatitis, associated with EFA ease.”The end products of rancidification in adipose tissue cause
deficiency, are most common in the external ear canals and a yellow, brown or orange discoloration of body fat. Affected
between the toes. However, lesions may develop anywhere on animals are anorectic, depressed, febrile and lethargic. They
the body. Emaciation can result from severe, persistent EFA move stiffly and generally show signs of cutaneous pain upon
deficiency. An EFA deficiency can also impair reproductive handling as the result of inflamed subcutaneous fat. Treatment
performance (i.e., neonatal abnormalities and death may result involves dietary correction and oral vitamin E administration
if pregnancy occurs). until clinical signs disappear (Cordy, 1954; Collins, 1983).