These common vegetables belong to the onion genus, Allium, one of the largest categories of plants in the world. This genera was originally classified in the lily family (Liliaceae). However, in 2009 it was reclassified and is now the subfamily Allioideae of the Amaryllidaceae family.
Although plants are classified by their flower, and not their chemical constituents, members of the Allium genus – garlic (Allium sativum), chives (A. schoenoprasum) onions (A. cepa), shallots (A. oschaninii), leeks (A. ampeloprasum) and scallions (A. ascalonicum) all contain some amount of organosulfur compounds (organic compounds that contain sulfur). The sulfur compound content is unique for each plant species and can increase if elevated sulphur levels are present in the soil during cultivation.
Onions are most commonly known for causing hemolysis (the destruction of red blood cells) in dogs, cats and horses, some of these sulfur-based compounds are also present in raw garlic.
When cut, onions form allyl propyl disulfide, diallyl disulfide, dipropyl disulfide, other disulfides, sulfides, trisulfides, thiosulfinates, sulfenic acids, mercaptans, sulfoxides, sulfates, and thial oxides. The concentration of allyl propyl disulfide, diallyl disulfide, and dipropyl disulfide [increases over time] after the onion is cut. (1)
[Garlic] cloves consist of cells that contain both a cysteine-based sulfur rich amino acid, called alliin (diallyl disulphide oxide) and a protein-based enzyme called allinase, which acts as a catalyst. These compounds are kept apart by the cell walls. The clove has little or no discernible smell until it is sliced and the two compounds are mixed. [When combined] these two compounds form a third compound, diallyl thiosulphinate, commonly called allicin.(2)
Allicin is the chemical which gives garlic its odor. It is a strong oxidant, which means that it creates free radicals, which in excess, can be dangerous. Allicin can cause stomach irritation and, in rare cases, hemolytic anemia – [the] destruction of red blood cells. If if placed directly on the skin, allicin can cause blistering. (3)
It is these organosulfur compounds present in concentration in raw garlic, raw onions and other members of the Allium genus that have the ability of causing hemolysis in certain animal species.
A Dusky-headed conure (Aratinga weddelli) [also known as Weddell’s conure] with a history of being force fed a large amount of garlic (Allium sativum) was presented because of anorexia and lethargy. The conure died one hour after supportive care was administered. At necropsy, a half clove of garlic and several large pieces of chicken meat were present in the crop. Histopathologic findings of hemoglobinuric nephrosis and hepatosplenic erythrophagocytosis strongly suggested an acute hemolytic event . [Meaning the microscopic examination of the bird’s tissues and body fluids revealed the abnormal presence of hemoglobin, that had been separated from the red blood cells, along with protein in the urine. Hemoglobin is the protein-iron compound in blood that carries oxygen from the lungs to the cells and carbon dioxide away from he cells to the lungs for exhalation. Additionally, the body’s macrophages and phagocytes had attacked and consumed red blood cells adversely affected the liver and spleen. These findings indicate that hemolysis, the destruction of red blood cells, had occurred.] Frozen kidney and liver samples were negative for polyomavirus DNA, and tissue lead and zinc levels were normal. The clinical presentation and postmortem findings in this conure are similar to those in mammals with onion and garlic (Allium species) toxicosis.(4) The Dusky-headed conure weighs approximately 95 gms. This is just slightly larger than my Green-cheek conure, Elvis, who weighs 80 gms.
The mechanism for avian hemolysis appears to be similar to the problems that can occur in dogs, cats and horses when they are feed raw onions or large volumes of raw garlic – with the amount being considered excessive in relationship to the size of the individual.
However, when any type of new plant, whether nutritional or medicinal, is being considered for introduction into a parrot’s diet painstaking research must first be conducted. With interest growing in the scientific community with regards to the healing properties of foods and nutritional and medicinal plants the discoveries and supporting evidence acquired through research, case studies and feeding trials provide a data base rich in scientific fact-based information. As more professionals publish their findings this knowledge becomes available to the person who knows how, through proper research, to gain access to the valuable information these documents contain. Then when made easily available to public – like the information I share with you in this column – situations like what occurred with the Dusky-headed conure can be avoided.
When introducing new herbs or foods to any parrot I always suggest we error on the side of caution. Although some parrot species may be able to consume small amounts of fresh or powdered garlic without ill effects, I think running the risk of causing hemolytic anemia is too great a danger, especially when there are safer, gentler natural alternatives. Years ago when I interviewed Dr Greg Harrison (Harrison’s Bird Diets) he explained that he and many of his colleagues would not do feeding trials on birds to test a food, chemical or substance they knew or suspected would cause harm. I applaud Dr Harrison’s attitude as I think we need to replace traditional feeding trials with a more humane, long term system, of feeding studies.
Avian veterinarians have repeatedly stated that malnutrition is the leading cause of illness, disease and early death of birds. If nutrients are missing from a bird’s diet, this results in either malnutrition or undernutrition. Patricia Macwhirter DVM, (in Avian Medicine: Principles and Application) malnutrition or undernutrition can cause a specific health related, or behavior related, problem or it can suppress a bird’s immune system. When the immune system has been suppressed the body becomes vulnerable to infection from a variety of pathogens: bacteria, fungus, virus or parasites.
With the topic of supporting the immune system in mind my favorite holistic tool uses food as medicine. Feeding a sprouting blend that has been formulated to provide complete protein and with a compatible germination and growth rate (so it can be grown for two to three days for optimum nutrition) provides a nutritional foundation not available in any other type or combination of foods.
I’m saddened by what the Dusky conure endured so we could benefit from the information his necropsy revealed. So is raw or powdered garlic safe to feed your parrots? I won’t feed it to my birds and I don’t recommend that it be given to birds, but then the choice is ultimately yours.
(1) “Allyl Propyl Disulfide, Diallyl Disulfide, Dipropyl Disulfide” Published by US Department of Labor, Occupational Safety & Health Administration (OSHA), Mary E. Eide, 1983, Methods Development Team, Industrial Hygiene Chemistry Division , OSHA Salt Lake Technical Center, Sandy UT
(2) Research paper “Garlic”, Eric Coleman, (third year chemistry student); Bristol University, UK.
(4) Case Study, “Hemoglobinuric Nephrosis and Hepatosplenic Erythrophagocytosis in a Dusky-headed Conure (Aratinga weddelli) After Ingestion of Garlic (Allium sativum)”, by Laura L. Wade DVM, Dipl ABVP (Avian) and Shelley J. Newman DVM, DVSc, Dipl ACVP in “Journal of Avian Medicine and Surgery” 18(3):155-161. 2004.
This article originally appeared in the April 2010, issue 147, of Parrots magazine.
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