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Alfalfa is a very palatable and productive herbaceous perennial legume with worldwide distribution. It is grown in every state in the US. Hundreds of different varieties have been developed. Growth habit is upright, with crowns having 5-25 stems growing 23-35 inches (60-90 cm) in height. Regrowth occurs from crown buds or axillary stem buds. Alfalfa has a prominent taproot. However, typically 60-70 percent of the root system is concentrated in the upper 6 inches (15 cm) of soil, with fibrous roots predominating and bearing most of the nodules. It is high yielding and high in quality, but requires high fertility and large quantities of water for optimum productivity. It is grown primarily for hay, but can be ensiled, or used as pasture, either alone or in combination with grasses (typically orchardgrass or smooth bromegrass). Dehydrated alfalfa can be pelleted, cubed, or sold as meal.
Growth habit is upright from a crown with 5-25 stems. Regrowth initiates from crown buds or axillary stem buds. Periodic defoliation (28-35 day schedule) is required to restore root carbohydrates.
Alfalfa has the highest feeding value of all commonly grown hay crops when harvested at late bud or early flower stage of maturity, while also being one of the most palatable and nutritious. Alfalfa produces the greatest amount of protein per acre of any livestock feed, and is often used in combination with corn silage in livestock rations to take advantage of the protein and energy content of the two feeds. When cut prior to bloom, it is low in fiber and high in energy. Thus, it is prized as a primary component in dairy cattle rations and is an important feed for horses, beef cattle, sheep, and milking goats.
Bloat often is a problem for animals pastured on alfalfa and various clovers. Bloat is a distention of the rumen caused by an inability of the animal to eructate gases produced in the normal process of fermentation. Unfortunately, the methods of controlling bloat are troublesome, expensive, and only partially effective. Using a grass-legume mixture in pastures, supplementing legumes with grass hays, intensive strip grazing with electric fences, and drylot feeding have all been somewhat successful.
The most effective treatment involves using bloat-preventative materials. These anti-foaming compounds may be added to drinking water, applied as a top-dressing on grain supplements, included in pellets, or added to salt-molasses blocks supplied on pasture. However, the effectiveness of these methods is variable and depends upon animals obtaining a regular supply of bloat preventative.
Five general types of plant-breeding procedures have been used to develop alfalfa cultivars. These include plant introductions, improved populations, synthetics, hybrids, and strain crosses. Many cultivars have been developed to increase multiple pest resistance, which uses the practice of strain crossing so plant breeders can quickly incorporate multiple resistance traits.