Animals have to absorb
nutrients to obtain energy and to build and repair their bodies.
Depending on their food source, animals may be carnivores,
herbivores, omnivores or detritivores. Animals are also adapted to
feed in different ways: some are bulk feeders, others feed on
fluids, and so on.
An adequate diet provides fuel,
materials for biosynthesis and essential nutrients. Food produces
energy, and the energy value of foods is measured in calories.
There are some important
nutrients that the body cannot make for itself. These are essential
amino acids, essential fatty acids, vitamins and essential minerals.
Absence of one or more of these essential nutrients can lead to