Allium species

Abstract

DISTRIBUTION: Not usually cultivated as animal feed. When market prices are low or crops are damaged by hail etc., it is sometimes fed to stock.

BOTANICAL DESCRIPTION: General: • Onions (Allium cepa), garlic and chives are all bulbous vegetables which are produced for human consumption. • They do not grow naturally in the wild. • The bulbs and/or leaves are edible. • Sometimes it is fed to stock for various reasons, or it could be part of the left-overs of human meals which is fed to pets.

TOXIC PRINCIPLE: • The toxic principle of Allium spp. is n-propyl disulphide, which is a non-nitrogenous, pungent, volatile oil, which inhibits the enzyme Glucose-6-phosphate dehydrogenase (G6PD) in the pentose phosphate pathway of the red blood cell. • The synthesis of reduced NADPH is thus stopped. • NADPH is important in the reduction of glutathione (GSH) which is again necessary to protect haemoglobin and the erythrocyte membrane from oxidative damage. • With oxidative damage the haemoglobin is denatured and the protein precipitates as Heinz bodies. • The affected erythrocytes are removed by the RE-system or intravascular haemolysis ensues resulting in haemoglobinaemia and haemoglobinuria.

SYNDROMES: Heinz body anemia.

SYSTEMS AFFECTED: Haemopoietic system.

CLINICAL SIGNS: • Especially sheep find onions palatable. • Cats and dogs are sometimes affected, since they could have been fed table scraps. Chronic ingestion results in a haemolytic anaemia and formation of Heinz-bodies. Acute: • Haemoglobinuria. Pale, anaemic mucous membranes. • Icterus (jaundice). • Diarrhoea, Ruminal stasis. Chronic: • Subclinical anaemia. • Ill-thrift. • Poor milk production, poor growth, emaciation • Infertility.

NECROPSY: Icterus. Anemia – pale mucous membranes, watery blood. Haemoglobinuria and dark pigmented kidneys. G.i.t. irritation. Treatment: • Remove feed • Blood transfusion in valuable animals. • Symptomatic and supportive.

PREVENTION: • Allium spp. should be fed only in limited quantities. • Feed with other good quality hay, concentrate, etc. • Can slowly increase the percentage of Allium spp. in the ration. • Avoid frost damaged plants - may have a higher concentration of the toxic principles.