Page 49 - Small Animal Clinical Nutrition 5th Edition

Chapter
5

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Macronutrients

Kathy L. Gross Dennis E. Jewell

Ryan M. Yamka William D. Schoenherr
Christina Khoo Jacques Debraekeleer
Kim G. Friesen Steven C. Zicker

“Nutriment is both food and poison.
The dosage makes it either poison or remedy.”
T. B. von Hohenheim

and toxicity may result if a food exceeds these levels. The area
INTRODUCTION between deficiency and excess represents the range of safe and
adequate nutrient intake. The extent of this area will change
Proper nutrition is among the more important considerations depending on the individual nutrient and overall composition
in health maintenance and key to disease management. A basic of the food. What is less well known is how exposure to mar-
knowledge of nutrients, requirements, availability and conse- ginal deficiencies and excesses affects an animal over time.
quences of deficiencies or excesses is important to feed dogs The most common method of determining the nutrient
and cats correctly and give advice about feeding. content of food is the proximate analysis, which provides the
A nutrient is any food constituent that helps support life. percentage moisture, protein, fat, ash and crude fiber.
Numerous essential nutrients have been discovered over the Digestible (soluble) carbohydrate or nitrogen-free extract
course of history. Nutrients are essential in that they are (NFE) can then be calculated. Figure 5-3 shows how the
involved in all basic functions of the body including: 1) acting determination is conducted. Many commercial laboratories
as structural components, 2) enhancing or participating in conduct proximate analyses of foods.
chemical reactions of metabolism, 3) transporting substances This chapter is organized into five sections: 1) water, 2) ener-
into, throughout or out of the body, 4) maintaining temperature gy, 3) carbohydrates and fiber (including prebiotic fibers, probi-
and 5) supplying energy. otics and synbiotics), 4) protein and amino acids and 5) lipids.
Nutrients are divided into six basic categories (Figure 5-1). Chapter 6 covers vitamins and minerals. The nutrients in this
Some nutrients fulfill a number of functions. For example, chapter and those in the next will be covered in the order shown
water and several minerals are needed for all the functions in Figure 5-1, beginning at the base of the pyramid. Energy, a
described above except supplying energy. Carbohydrates, fats non-nutrient, but nonetheless essential for life will be covered
and proteins may be used for energy but they can also serve as after water.
structural components. Vitamins are involved primarily with
metabolic functions. WATER
Figure 5-2 shows how an individual nutrient can affect the
health of an animal. The minimum dietary requirement has Definition and Function
been established for most nutrients. Clinical signs of deficiency Chemically, water is the combination of hydrogen and oxygen,
may result if a food doesn’t provide this nutrient level. Similarly, which are joined in the ratio of two hydrogen atoms to one oxy-
the maximum tolerable levels of certain nutrients are known gen (H O). Water is vital to life and is considered the most
2