Alfalfa
General poisoning notes:
Alfalfa (Medicago sativa) is an important forage and silage crop in Canada. However, under some circumstances, alfalfa can cause a variety of different toxic problems. Ingesting rapidly growing alfalfa at the vegetative to mid-bud stage can cause bloat in cattle and sheep (Hall and Majak 1989). Alfalfa has also caused photosensitization in cattle with white skin (MacDonald 1954). Alfalfa contains phytoestrogens which cause infertility in animals, including cattle and sheep. These compounds are also contained in some alfalfa pills that are found in health food stores, and these may cause problems in some cases (Cheeke and Schull 1985). Alfalfa also contains saponins that can interfere with the growth of poultry and thus reduce egg-laying (Fuller and McClintock 1986, Oakenfull and Sidhu 1989). Low saponin cultivars have been developed.
Nomenclature:
Scientific Name: Medicago sativa L.
Vernacular name(s): alfalfa
Scientific family name: Leguminosae
Vernacular family name: pea
Medicago sativa
Geographic Information
Alberta, British Columbia, Manitoba, New Brunswick, Northwest Territories, Nova, Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan
Toxic parts:
Leaves, stems
Notes on Toxic plant chemicals:
Alfalfa contains two phytoestrogenic compounds, coumestrol and coumestan. These compounds can cause fertility problems in sheep and cattle. Alfalfa also contains bloat-causing proteins. Saponins, such as medicagenic acid, can cause growth reduction in poultry (Adams 1989, Hall and Majak 1989, Oakenfull and Sidhu 1989).
Toxic plant chemicals:
Coumestan, coumestrol
medicagenic acid
medicagenic acid
Chemical diagram(s) are courtesy of Ruth McDiarmid, Biochemistry Technician, Kamloops Range Station, Agriculture and Agri-Food Canada, Kamploops, British Columbia, Canada.
Animals/Human Poisoning:
Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.
Cattle
General symptoms of poisoning:
Bloat, infertility
Notes on poisoning:
Cattle are especially susceptible to bloat after ingesting rapidly growing alfalfa in the vegetative to mid-bud stage of growth. The formation of stable foam bubbles is recognized as being affected by the concentration of cytoplasmic proteins, which is in turn affected by rumen pH, and the colloidal suspension of chloroplast particles from the plant; the stability is controlled by ion concentration (Hall and Majak 1989). Alfalfa also contains phytoestrogens, which have caused infertility problems in dairy cattle because of cystic ovaries and irregular estrous cycles. Precocious development of mammary glands also occurs, as well as genital formation in heifers. The coumestan chemicals suppress estrous and inhibit ovulation (Cheeke and Schull 1985, Adams 1989).
Chickens
General symptoms of poisoning:
Weight gain, reduced
Humans
General symptoms of poisoning:
Infertility
Notes on poisoning:
Alfalfa tablets are available in health food stores as a dietary supplement for humans. The benefits of the tablets are not clear. Measurements of the phytoestrogen content of some commercial brands have ranged from 20 to 190 ppm. This level of intake, in conjunction with other sources of estrogen (such as birth control pills and estrogen replacement therapy), may be potentially harmful (Cheeke and Schull 1985).
Sheep
General symptoms of poisoning:
Bloat, erythema, infertility, skin, peeling of
