Ureteral and Intestinal Obstruction Associated with Abdominal Fat Necrosis in a Herd of Eld’s Deer: Suspected Fescue Toxicosis
Between 1994 and 1996, two adult (6 and 7-yr-old) female Burmese brow-antlered deer, or Eld’s deer (Cervus eldi thamin), housed at the Conservation and Research Center (CRC) in Front Royal, VA, died acutely with no premonitory clinical signs. At necropsy, both animals had large masses of firm, mineralized perirenal and sublumbar adipose tissue that partially enveloped each kidney. The masses surrounded and constricted the ureters bilaterally, causing hydroureter and hydronephrosis. A third animal, a 6-yr-old female, presented to the veterinary hospital with anorexia and depression of 2 days’ duration. Loose, tarry feces and frank blood were present on the tail and perineum. Abdominal palpation and radiographs indicated the presence of large firm masses within the abdomen, and serum chemistry showed a markedly elevated BUN (270 mg/dL) and creatinine (16.9 mg/dL). An exploratory laparotomy revealed the abdominal cavity to be filled with very large, firm white masses that adhered to most of the abdominal organs and apparently obstructed the gastrointestinal tract. The animal was euthanatized, and necropsy confirmed large masses of mineralized necrotic sublumbar and perirenal fat constricting the ureters bilaterally as well as the intestinal tract at the cecocolic junction, resulting in bilateral hydronephrosis and cecal impaction.
A retrospective study of Eld’s deer deaths at CRC from 1975 to 1996 (including those described above) revealed that, of 45 deaths of Eld’s deer housed at CRC for 2 yr or more, 11 (24.4%) had necrotic fat at necropsy. Six affected animals were female and five were male. Five of those affected had uni- or bilateral hydronephrosis associated with ureteral constriction by masses of necrotic fat, and four of the five with hydronephrosis were female. Since 1994, there have been 11 Eld’s deer deaths, and of these, seven (63.3%) had necrotic fat and four had associated hydronephrosis.
Physical examination and radiographic screening of the CRC Eld’s deer population were subsequently conducted to assess the prevalence of abnormal fat in the remaining population. Of 16 female Eld’s deer (3–15-yr-old), 15 (93.75%) had palpable firm sublumbar masses. Thirteen of the 15 masses were also visualized radiographically, and 9 appeared mineralized. Only one of seven male Eld’s deer screened (9–15-yr-old) had palpable firm abdominal masses, which were not visible radiographically. Abnormal fat was not detectable in animals of either sex under the age of 3 yr. Laparoscopic evaluation confirmed the presence of firm masses of sublumbar fat in all females diagnosed with abnormal fat by palpation and/or radiography. Males were not examined laparoscopically. Fat biopsies obtained laparoscopically demonstrated histologic changes similar to those observed in necropsy cases and included extensive coagulative necrosis of adipocytes with foci of saponification, fibrous tissue proliferation and, occasionally, focal osseous metaplasia. Inflammation was not a prominent feature in any of the cases.
The lesions in these animals are similar to those described in cattle on endophyte-infected fescue pasture.1 Fat necrosis has been reported in a wide variety of species, and it is believed to occur by different pathological mechanisms. In cattle, fat necrosis is associated with several factors: 1) obesity, 2) breed predisposition, 3) nitrogen-fertilized grasses, and 4) tall fescue (Festuca arundinacea) forage infected with an endophyte fungus, Acremonium coenophialum.
The CRC Eld’s deer herd has been segregated by gender and kept on pasture from March to November since 1988. Females are rotated on two pastures totaling approximately 4 acres, consisting primarily of tall fescue, orchardgrass, bluegrass, red clover, crowned vetch and alfalfa. Particularly during the cool season, tall fescue appears to be the predominant grass in the pasture, and the deer have been observed to eat tall fescue over other available grasses. During the winter months, the animals are housed indoors and fed alfalfa and a pelleted diet consisting of wheat middlings, soybean hulls, alfalfa, corn, cane molasses, beet pulp, soybean oil and vitamin/mineral supplements. The pelleted diet contains 12.5% crude protein, 3.0% crude fat and 21% crude fiber.
Fescue samples from several CRC pastures, including Eld’s deer pastures, were confirmed to be highly infected with the endophyte fungus by the Auburn University Fescue Toxicity Diagnostic Center.
Similar lesions of fat necrosis, or lipomatosis, have been reported in other Asian cervid species including swamp,2 sika and sambar deer3. In each report, the etiology of the fat necrosis was not determined, but diet was suggested as a likely cause. While age, diet and genetic predisposition may be contributing factors, the level of endophyte infection in the resident tall fescue and the increasing incidence of the problem suggest that, as in cattle, endophyte-infected tall fescue forage has played a role in the development of necrotic fat in these Eld’s deer. Moderately infected tall fescue pastures tend to become increasingly infected over time because the infected plant is, paradoxically, more insect-, drought- and disease-resistant than the noninfected plant.4-8 Therefore, it is likely that this herd has been exposed to increasing levels of infected forage over the past 9 yr.
Further studies are being conducted to determine the nature and cause of abdominal fat necrosis in Eld’s deer at CRC. In early summer 1996, the Eld’s deer pastures were treated with herbicide and reseeded with switchgrass, orchardgrass and alfalfa. Since this time, there have been no clinical developments attributed to fat necrosis in the Eld’s deer herd.
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2. Ashton, D.G., E.C. Appleby, D.M. Jones. 1982. Abdominal lipomatosis in swamp deer (Cervus duvauceli)- a preliminary report. In: Erkrankungen der Zootiere. Verhandlungsbericht des XXIV. Internationalen Symposiums uber die erkrankungen der Zootiere. Akademie-Verlag Berlin.
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8. Yates, S.G., J.C. Fenster, and R.J. Bartelt. 1989. Assay of tall fescue seed extracts, fraction and alkaloids using the large milkweed bug. J. Agric. Food Chem. 37:354–357.