Answer to Question 1
Nutrition: sustenance of the basic processes of life.
The study of nutrition consists of scientific investigations that provide us with knowledge and sound principles of biology and chemistry that can be applied to help ensure health, welfare, and longevity.
Note, technically, the following sentence is wrong: This food is high in nutrition. That sentence means nothing because different nutrients are required in varying amounts relative to the animal and its needs. A more correct sentence would be: This food is adequate in the nutrients required (for this animal).
Answer to Question 2
Aging animals generally have reduced total requirements for nutrients, even at the same body weight, as the metabolic rate slowly decreases over time. So as the energy needs slowly decline, this means the animal must either consume less, or consume a diet with less energy yielding components in it. Muscle protein turnover slows, and the ability of the kidney to synthesize and excrete the by-products of amino acid metabolism normally declines with age.
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