Brewers grains, a by-product of beer production, are often used as a livestock feed. Because brewers grains provide protein, fiber, and energy, they can be useful in a variety of diets. Protein in brewers grains can meet a significant portion of supplemental protein requirements; in addition, they provide fiber and needed bulk in the diets of ruminants and horses. Brewers grains and other brewers by-products have also been fed to pigs, sheep, and poultry.

Studies showed that citrus products provide cows with good roughage and vitamins, and the essential oils in such products provide a natural antibiotic effect. U.S. Department of Agriculture (USDA) scientists and their collaborators have conducted a series of studies that explore non-antibiotic methods to reduce foodborne pathogens that are found in the gut of food animals.

Grape is the largest fruit crop worldwide and the grape pomace is an important solid waste generated from pressing and fermentation processes in wine industries. Wine industry residues are rich in bioactive compounds and, used as a feed supplement by the dairy and beef industries.