Not usually cultivated as animal feed. When market prices are low or crops are damaged by hail etc., it is sometimes fed to stock.
• 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.
• 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.
Heinz body anemia.
• 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.
• Haemoglobinuria. Pale, anaemic mucous membranes.
• Icterus (jaundice).
• Diarrhoea, Ruminal stasis.
• Subclinical anaemia.
• Poor milk production, poor growth, emaciation
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.
• 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.
Colour photos. Final web-ready size: JPEG, 72 ppi. Photo 1: 6.7 kb; Photo 2: 27.1 kb; Photo 3: 27.5 kb. Original TIFF file housed at the Dept. of Paraclinical Sciences, Section Pharmacology and Toxicology, University of Pretoria.