The number of dog foods available and the variation in nutrient concentrations between products may make choosing feeds a confusing task. The guidelines in the Feeding and Watering section are intended to help you choose the appropriate source or sources of nutrition to meet the specific requirements of your dogs.
The first step in evaluating a particular dog food is determining the concentration of nutrients in the products you are considering. Most commercial foods have a guaranteed analysis on the label; more detailed information is available by contacting the company. Vendors of frozen or fresh meat products may have analyses available as well. If not, such an analysis can be obtained by submitting a sample to a university or commercial laboratory.
When choosing a dog food, always compare nutrient concentrations on a dry-matter basis. Most dry products contain only about 10 percent water, while meat products may range from 65 to 85 percent water. Since all the protein, fat, carbohydrates, vitamins, and minerals are found in the dry matter, you cannot look at the nutrient concentrations of feeds on an as-fed basis and fairly compare dry and meat products.
For example, a dry product that contains 30 percent protein and 20 percent fat on an as-fed basis (10 percent water), and a meat product containing 8.3 percent protein and 5.5 percent fat on an as-fed basis (75 percent water) both contain 33 percent protein and 22 percent fat on a dry-matter basis.
To avoid this confusion, convert as-fed percentages to dry matter percentages with this simple formula:
as-fed % ÷ [(100 - % water) ÷ 100] = dry-matter %
Using this formula, you could determine the dry-matter fat concentration of a meat-based diet containing 75 percent water and 5.6 percent fat on an as-fed basis as follows:
For a dry food containing 10 percent water and 20 percent fat, the calculation for the dry-matter percentage would be: