Wednesday, June 17, 2015

The World's Favourite Forage Crop: Alfalfa, Medicago sativa

So I recently wrote about Galega orientalis, an introduced species that has been brought to North America as a forage crop (forage : in this case, referring to use for animal feed).

Medicago sativa
I have since discovered that there is Medicago sativa (alfalfa) in the forested side of the Notre-Dame-des-Neiges Cemetery. This plant has been introduced all over the world, including in most states and provinces (US range map here, Canada range map here). In the wild, this plant is a documented source of food for non-livestock animals [1], including antelope, deer, elk, Canada geese, and grouse [2]. Though this plant is widely distributed, it isn't listed as invasive. Note, however, that it is considered weedy in parts of the US [1,2], but is not included in weed lists for Canada [3].

Medicago sativa inflorescence
Medicago sativa, like G. orientalis, is a member of the Fabaceae (legume family), and like many members of this family it is a nitrogen-fixing plant [2,4,5].

Medicago sativa is considered the oldest forage plant [2,4], and is also the most widely used forage crop today [4,5]. It is so greatly favoured for the nutritional quality of the hay it produces and for its high yield by acreage [4,5].

Medicago sativa inflorescence
This plant can be used for grazing rather than haying (grazing : letting livestock feed from the plant directly in the field - haying : growing, cutting, and processing the plant for feed), but because in certain life stages it can cause bloat [2,4,5,6], grazing must be controlled with care.

Medicago sativa inflorescence
Although alfalfa (unsprouted seed) is often touted as a treatment for a variety of human ailments, there is insufficient evidence to support these claims [7], and some of the compounds found in alfalfa (unsprouted seed) are likely harmful to humans if consumed long-term [6,7].

Medicago sativa is primarily pollinated by a solitary bee in the Megachilidae (leafcutter bees), Megachile rotundata (alfalfa leafcutter bee), because pollination using Apis mellifera (honeybees) requires large numbers of naive (young) bees because they are not actually capable of obtaining the reward from this flower due to its shape, so they learn quickly to avoid it [5]. Although large numbers of naive bees are used to pollinate alfalfa in places, Megachile rotundata is increasingly preferred [5].

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