Purina Complete Alfalfa Rabbit Feed Pellets, 50 lb.

50 may refer to:

• 50 (number)
• one of the following years 50 BC, AD 50, 1950, 2050
• .50 BMG, a heavy machine gun cartridge also used in sniper rifles
• .50 Action Express, a large pistol cartridge commonly used in the Desert Eagle
• .50 GI, a wildcat pistol cartridge
• .50 Beowulf, a powerful rifle cartridge used in the AR-15 platform
• .50 Alaskan, a wildcat rifle cartridge
• 50 Cent, an American rapper
• Labatt 50, a Canadian beer
• Fifty (film), a 2015 film
• "The Fifty", a group of fifty airmen murdered by the Gestapo after The Great Escape in World War II
• 50 (Rick Astley album), 2016
• 50 (Chris de Burgh album), 2024
• Benjamin Yeaten, widely known by his radio call sign "50", a Liberian military and mercenary leader
• "Fifty", a song by Karma to Burn from the album V, 2011
• 50 Virginia, a main-belt asteroid
• Audi 50, a supermini hatchback
• Dodge Ram 50, a compact pickup truck sold in the United States as a rebadged Mitsubishi Triton

Alfalfa () (Medicago sativa), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as well as a green manure and cover crop. The name alfalfa is used in North America. The name lucerne is more commonly used in the United Kingdom, South Africa, Australia, and New Zealand. The plant superficially resembles clover (a cousin in the same family), especially while young, when trifoliate leaves comprising round leaflets predominate. Later in maturity, leaflets are elongated. It has clusters of small purple flowers followed by fruits spiralled in two to three turns containing 10–20 seeds. Alfalfa is native to warmer temperate climates. It has been cultivated as livestock fodder since at least the era of the ancient Greeks and Romans.

Purina may refer to:

• Ralston Purina, an American pet food company that was acquired in 2001
• Nestlé Purina PetCare, the pet food division of Swiss-based Nestlé S.A., and the acquirer of Ralston Purina Company in 2001 (subsequently merged with Nestlé's Friskies PetCare Company)
• Purina Mills, a farm animal feed company that was spun off from Ralston Purina Company

Rabbits are small mammals in the family Leporidae (which also includes the hares), which is in the order Lagomorpha (which also includes pikas). They are familiar throughout the world as a wild prey animal, a domesticated form of livestock, and a pet, having a widespread effect on ecologies and cultures. The most widespread rabbit genera are Oryctolagus and Sylvilagus. The former, Oryctolagus, includes the European rabbit, Oryctolagus cuniculus, which is the ancestor of the hundreds of breeds of domestic rabbit and has been introduced on every continent except Antarctica. The latter, Sylvilagus, includes over 13 wild rabbit species, among them the cottontails and tapetis. Wild rabbits not included in Oryctolagus and Sylvilagus include several species of limited distribution, including the pygmy rabbit, volcano rabbit, and Sumatran striped rabbit.

Rabbits are a paraphyletic grouping, and do not constitute a clade, as hares (belonging to the genus Lepus) are nested within the Leporidae clade and are not described as rabbits. Although once considered rodents, lagomorphs diverged earlier and have a number of traits rodents lack, including two extra incisors. Similarities between rabbits and rodents were once attributed to convergent evolution, but studies in molecular biology have found a common ancestor between lagomorphs and rodents and place them in the clade Glires.

Rabbit physiology is suited to escaping predators and surviving in various habitats, living either alone or in groups in nests or burrows. As prey animals, rabbits are constantly aware of their surroundings, having a wide field of vision and ears with high surface area to detect potential predators. The ears of a rabbit are essential for thermoregulation and contain a high density of blood vessels. The bone structure of a rabbit's hind legs, which is longer than that of the fore legs, allows for quick hopping, which is beneficial for escaping predators and can provide powerful kicks if captured. Rabbits are typically nocturnal and often sleep with their eyes open. They reproduce quickly, having short pregnancies, large litters of four to twelve kits, and no particular mating season; however, the mortality rate of rabbit embryos is high, and there exist several widespread diseases that affect rabbits, such as rabbit hemorrhagic disease and myxomatosis. In some regions, especially Australia, rabbits have caused ecological problems and are regarded as a pest.

Humans have used rabbits as livestock since at least the first century BC in ancient Rome, raising them for their meat, fur and wool. The various breeds of the European rabbit have been developed to suit each of these products; the practice of raising and breeding rabbits as livestock is known as cuniculture. Rabbits are seen in human culture globally, appearing as a symbol of fertility, cunning, and innocence in major religions, historical and contemporary art.