Medicago sativa and Trifolium species

Abstract

DISTRIBUTION: Trifolium spp. as well as Medicago spp. were imported from Europe and Asia to grow as fodder for stock. The Oudtshoorn district is responsible for about 90% of the lucerne seed produced in South Africa.

BOTANICAL DESCRIPTION: Trifolium repens: Low growing, spreading plants with trifoliate leaves, sometimes mistaken for grass.

TOXIC PRINCIPLE: Frothy bloat: Saponins and glycoproteins.

MECHANISM OF ACTION: • Soluble proteins escape rapidly from fragile thin-walled cells of above species during cellulose digestion. • This results in changes in surface tension of ruminal fluid and stabilization of gas bubbles in rumen. • Critical concentration of several surface-active agents leads to persistent, rigid foam. Phyto-oestrogenism: • The toxic principles of the clovers are various isoflavone glycosides, which are inherently oestrogenic and/or are biotransformed in the rumen to active or inactive compounds. • The oestrogenic compounds contained in lucerne are coumestans.

SYNDROMES: Frothy bloat, ABPE, Phyto-oestrogenism.

SYSTEMS AFFECTED: Gastro-intestinal, urogenital and respiratory systems.

CLINICAL SIGNS: Frothy bloat: • Severe bloat, distended abdomen. • Ruminal atony. • Dyspnoea. Phyto-oestrogenism: • Infertility.