1. Dry Roughages & Forages: Forage is defined as vegetative material in a fresh, dried, or ensiled state. It includes the leaves, stems, and stalks of plants. The term roughage is sometimes used interchangeably with forage although roughage is a broader term. Roughages are bulky feeds with a low weight per unit volume. Bulky feeds are high in fiber. Roughages include items such as peanut hulls or cottonseed hulls which are not forages. Forages are usually defined by how much fiber they contain. On a dry basis, they usually contain more than 18% crude fiber or 35% cell wall (cellulose, hemicellulose and lignin) and are lower in energy than concentrates. They are also usually lower in digestibility than concentrates due to their higher cell wall content. They are variable in protein content. For example, legumes such as alfalfa may contain 20% crude protein whereas some very low quality forages may contain only 4% crude protein. Forages also provide minerals and vitamins. Forages are used extensively in the diets of ruminants, horses, and other herbivores (plant eaters). In addition to providing nutrients, forage in the diet is important to reduce digestive disturbances in herbivores.
2. Pasture: A pasture is an area of land on which there is a growth of forage (fresh growing grass or legume) that animals can graze. Use of pasture tends to lessen feed costs and, if well-managed, provides a good source of high quality protein, vitamins and minerals. In some climates, forages grow throughout the year and therefore, pasture is available year round. In other climates, particularly in colder regions, there are certain times of the year that preserved forage must be fed.
Hay and silage are two ways of preserving forage. Hay is forage harvested during the growing period and preserved by drying. It can retain much of its nutritional value during storage if it is stored properly. The objective in making hay is to reduce the moisture content of the hay around 15% or less and thus retard enzymatic or microbial degradation during storage. The quality of hay will vary with the species of plant (grasses vs legumes); stage of maturity at which it was cut; and general handling and weather during cutting.
3. Silage: Silage is fermented forage stored under anaerobic (without oxygen) conditions in a silo. The conditions provide an environment where microorganisms ferment the soluble carbohydrates in the forage producing lactic acid, and other short chain fatty acids. As the acids are produced, the pH decreases until it is around 4.0-4.5. As the pH decreases, microbial growth is inhibited and as long as the conditions remain anaerobic, the silage is relatively stable. Forages for silage are stored at approximately 60-65% moisture. Corn is the most common form of silage. Haylage is made from wilted grasses or legumes and is stored in a sealed plastic wrap at 50-60% moisture. There is limited anaerobic microbial fermentation. The final pH of haylage is less acidic than that of silage.
4. Energy Feeds: The category of energy feeds includes several categories of feedstuffs. In general, they are higher in energy density and lower in fiber than forages and roughages. Relative to fiber content they are defined as having less than 18% crude fiber or less than 35% cell wall. They are highly digestible. Types of feedstuffs in this category include cereal grains, co-products from the milling industry, molasses, fats and oils, roots and tubers, beet and citrus pulps, whey products, and seeds of other plants.
5. Protein Supplements: Protein supplements are feedstuffs containing more than 20% crude protein and may be of plant or animal origin.
6. Mineral Supplements: Mineral supplements include many mineral sources to be included in the animal feed which typically include Ca, P, Cu, Fe, Mn, Zn, I, and Se.
7. Vitamin Supplements: Vitamins are organic compounds required for normal growth and the maintenance of life. Vitamins are effective in minute amounts in animal body. Some vitamins are essential for the regulation of metabolism but they are not used as building blocks. Other vitamins are essential for energy transformation whereas they are not supplying energy. Animals are unable to synthesize most of vitamins. However, some vitamins can be synthesized in the animal body using precursors or from 'pro-vitamins'. Examples are vitamin A, vitamin C, vitamin D, and niacin (vitamin B3). Other vitamins are made by microorganisms in rumen and large intestine. All B vitamins are synthesized by rumen microorganisms and can be provided to the ruminants. Vitamin K is synthesized by microorganisms in large intestine and can be provided to the host animals.
Vitamin supplements can contain various amounts of vitamin A, vitamin D, vitamin E, vitamin K, B vitamins (including thiamine (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), cobalamin (B12), folic acid, biotin, and pantothenic acid), and ascorbic acid (vitamin C) meeting the requirement of targeting animals.
8. Nonnutritive Supplements: Nonnutritive additives can be used in animal feed for specific functions such as to improve the efficiency of feed utilization, to improve growth, to enhance palatability, or to enhance the health of animals. However, feedstuffs in this category are not nutrients or source of nutrients. Nonnutritive additives are supplemented in a minute amount. Feedstuffs in this category include feed flavors, pellet binders, antibiotics, probiotics, antioxidants (preservatives), feed enzymes, mold inhibitors, buffers, ionophores, ractopamine, and pigmenting agent.