Abstract
Peracute mortality syndrome, or giraffe wasting disease, has been a leading cause of mortality in giraffe since the 1970s. It generally presents as acute death without premonitory signs. It is characterized by serous atrophy of adipose tissue and weight loss. Other lesions are nonspecific. Several articles have been published suggesting a potential nutritional component.2,4-6,8
Over the past 15 yr, evaluation of the serum, omental, and pericardial adipose tissue relative % fatty acids (R%FA) in captive North American giraffe deaths has demonstrated an inverted linolenic:linoleic acid ratio when compared to wild giraffe values in virtually all animals.
Linolenic acid is metabolized at a lower temperature than linoleic acid.1 When linolenic to linoleic acid ratios are inverted for a prolonged period, giraffe enter a negative energy balance and subsequently lose weight. Cold stress is a well-known inducer of lipolysis.2 Due to the large surface area of giraffe and minimally protective pelage, conservation of body heat is not possible during suboptimal environmental temperatures. Since linolenic acid burns at a lower body temperature than linoleic acid, we postulate that prolonged suboptimal environmental temperatures cause serous atrophy of fat reserves and predisposes to acute mortality.
Very few species of native plants in the United States provide a linolenic to linoleic acid ratio > 1:1. Perilla futrescens, Linum usitatissimum, and Salvia columbariae plants provide a linolenic:linoleic acid ratio > 2:1.1,7 Alfalfa hay, the most common component of giraffe diets, provides a significant inverse ratio of linolenic to linoleic acid.1 To find a plant that provides a linolenic to linoleic acid ratio > 2:1, we looked for a North American equivalent to African Acacia species, the predominant forage of wild giraffe.3
Prairie bundle flower (Desmanthus illinoisensis), a common native plant, was analyzed for relative % fatty acid (R%FA) profiles and found to have a greater linolenic:linoleic acid ratio than any other plant studied. (We theorize that giraffe, as well as other ruminants have an as yet unknown mechanism to detect and seek out plants based on their linolenic:linoleic ratio, as they actively seek this plant out over other browse items offered). Plants were grown on zoo grounds, harvested and analyzed at various stages of seasonality. In addition, plants were dried for 30, 60 and 90 days, and then analyzed for R%FA analyses. No adverse effects were noted when supplementing prairie bundle flower to giraffe. Results are encouraging and may provide a basis for year round supplementation to captive giraffe diets, minimizing the need for high energy, alfalfa based diets that may predispose to rumen acidosis, urinary calculi and urethral blockage, the latter of which is commonly diagnosed as a cause of death in male giraffe. Additional research into fatty acid content of wild Acacia sp. and supplementation is ongoing.
Literature Cited
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