Animal feed is any material, whether plant-based, animal-derived, or manufactured, that is given to livestock, poultry, fish, or pets to meet their nutritional needs. It is the single largest cost in raising animals, typically accounting for 60% to 70% of total livestock production costs. Global feed production reached nearly 1.4 billion metric tons in 2024, supplying operations that range from backyard chicken coops to industrial-scale cattle feedlots.
The Two Main Categories: Roughages and Concentrates
Almost all animal feed falls into one of two broad groups: roughages and concentrates. Understanding the difference comes down to fiber and energy density.
Roughages are bulky, plant-based feeds that are high in fiber and relatively low in digestible energy. The standard classification defines a roughage as any feedstuff with at least 18% crude fiber. Hay, pasture grass, silage, straw, and crop stalks all qualify. These feeds are rich in the structural carbohydrates that make up plant cell walls, and they tend to supply more calcium, potassium, and fat-soluble vitamins than concentrates do.
Concentrates are the opposite: dense in energy or protein, low in fiber. Grains like corn, barley, and wheat are energy concentrates. Soybean meal and cottonseed meal are protein concentrates. Because they pack more nutrition into a smaller volume, concentrates are digested faster and more completely. Livestock diets are usually built by combining roughages and concentrates in ratios that match the animal’s stage of life and production goals.
Why Different Animals Need Different Feeds
The feed an animal needs depends heavily on how its digestive system works. Cattle, sheep, and goats are ruminants, meaning they have a multi-compartment stomach that houses billions of microbes. Those microbes ferment fibrous plant material, breaking down tough cell walls that a simple stomach could never handle. The fermentation process also generates protein, energy, and B vitamins for the animal. This is why cattle can thrive on grass and hay alone.
Chickens, pigs, and most fish are monogastric, meaning they have a single-compartment stomach with limited capacity for microbial fermentation. They rely on their own digestive enzymes to break food down, so they need more concentrated, nutrient-dense diets with well-balanced amino acids and vitamins already present in the feed. A pig fed only grass hay would not get enough energy or protein to grow.
Key Nutrients in a Feed Ration
Every feed ration is designed around six nutrient classes: protein, carbohydrates, fat, vitamins, minerals, and water. The exact proportions shift depending on the species, age, and purpose of the animal. A growing beef steer, for example, needs a diet with roughly 10% protein and about 60% total digestible nutrients (a measure of available energy). A mature cow in early pregnancy needs less, around 8% protein and 53% energy. Dairy cows in peak milk production and fast-growing broiler chickens sit at the high end of both protein and energy requirements.
Carbohydrates supply most of the energy. In grains, these come as starches and sugars inside the plant cell. In roughages, the energy is locked in structural fibers like cellulose and hemicellulose, which only ruminant microbes can efficiently unlock. Fat is a concentrated energy source, often added in small amounts to boost calorie density without increasing bulk. Minerals like calcium and phosphorus support bone growth and metabolic function, while vitamins play roles in everything from immune response to reproduction.
Preserved Forages: Hay, Silage, and Haylage
Fresh pasture isn’t available year-round, so farmers preserve forage for later use. The method they choose depends on the moisture content of the crop at harvest.
Hay is forage that has been dried in the field until most of its moisture is gone, then baled for storage. Silage takes the opposite approach: the forage is harvested while still wet (above roughly 50% moisture) and packed into an airtight structure where natural fermentation by bacteria converts plant sugars into organic acids. This acid environment preserves the feed, similar to how pickling preserves vegetables. Corn is considered an ideal silage crop because of its high sugar content and the fact that it naturally reaches the right moisture level (about 65% to 70%) at harvest.
Haylage, sometimes called baleage, falls between the two. It is forage that has been partially dried to around 40% to 60% dry matter before being sealed and fermented. Forage that is too wet (above 70% moisture) risks producing foul-smelling, poorly preserved silage because harmful bacteria outcompete the beneficial ones.
Feed Additives and Their Roles
Beyond the base ingredients, commercial feeds often include small amounts of additives designed to improve digestion, health, or feed quality.
- Enzymes help animals extract more nutrition from their feed. One widely used enzyme breaks down a compound in grains and oilseeds that locks up phosphorus, making that phosphorus available for the animal to absorb. This not only improves nutrition but reduces the amount of phosphorus excreted into the environment. Other enzymes target complex carbohydrates in wheat and barley that monogastric animals cannot digest on their own.
- Probiotics are live beneficial bacteria added to feed to support gut health. They colonize the intestine and crowd out harmful pathogens by producing antimicrobial substances and competing for space. They serve as an alternative to antibiotic growth promoters in many modern production systems.
- Prebiotics are non-digestible fiber ingredients that selectively feed the beneficial bacteria already living in the gut, encouraging their growth.
- Antioxidants prevent the fats in feed from going rancid during storage. By neutralizing free radicals, they extend shelf life and preserve feed quality.
How Commercial Feed Is Made
Large-scale feed manufacturing transforms raw ingredients into a uniform product so that every mouthful an animal takes contains the intended balance of nutrients. The process follows a consistent sequence.
First, raw ingredients are ground to reduce particle size. Finer particles mix more evenly and are easier for animals to digest. Next, the ground ingredients are combined in a mixer following a precise formula. The goal is to distribute every component, including micro-ingredients like vitamins and trace minerals, uniformly throughout the batch.
Many feeds are then pelleted. The mixed feed passes through a conditioning chamber where steam adds about 4% to 6% moisture and heat, softening the material. It is then forced through a die under high pressure, forming dense pellets. Pelleting reduces dust, prevents animals from sorting out preferred ingredients, and improves digestibility. After extrusion, the hot pellets are cooled within about ten minutes to near room temperature and dried to below 13% moisture so they store without spoiling.
Regulation and Labeling
In the United States, animal feed is regulated under the same foundational law that covers human food: the Federal Food, Drug, and Cosmetic Act. All animal feeds must be safe, produced under sanitary conditions, free of harmful substances, and truthfully labeled. The FDA requires that labels include the product name, a net quantity statement, the manufacturer’s name and address, and a complete ingredient list ordered from most to least by weight.
Every ingredient must be either approved as a food additive or generally recognized as safe for its intended use. Colorings need specific approval. Canned pet foods face additional requirements to ensure they are processed at temperatures high enough to eliminate dangerous microorganisms. State-level feed regulators add another layer of oversight, often requiring product registration and periodic inspection of manufacturing facilities.
Feed Costs and the Global Industry
Because feed represents 60% to 70% of the cost of raising livestock, even small changes in grain prices ripple through the entire food system. When corn or soybean prices spike, the cost of producing chicken, pork, eggs, and milk rises with them. This is why feed efficiency, the amount of feed an animal needs to gain a pound of body weight, is one of the most closely tracked metrics in animal agriculture.
Global feed production hit 1.396 billion metric tons in 2024, a 1.2% increase over the previous year. China, the United States, and Brazil are the largest producing countries. The industry continues to explore alternative protein sources like insect meal and algae to reduce reliance on traditional ingredients such as fishmeal and imported soy, though these alternatives remain a small fraction of total production.