Nutritional investigations and management of captive moose

Abstract

Historically, moose have been difficult to maintain in captivity when on diets of grass or legume hays and grain due to enteritis that frequently leads to chronic diarrhea/wasting disease. The development of wood-fiber diets has increased the lifespan of moose in captivity, but these diets do not completely prevent chronic wasting. Purina Mills (St. Louis, MO) hypothesized that captive moose are unable to digest starch that escapes the rumen, and therefore abnormal bacterial fermentation in the hindgut causes chronic diarrhea. An earlier study found no evidence of a digestive problem, so we tested the hypothesis that moose have difficulty metabolizing excess propionate produced from the fermentation of starch found in traditional cervid rations and high-grain wood-fiber diets. When challenged with an i.v. propionate load, moose metabolized propionate similar to healthy mule deer and domestic livestock. We then tested the hypothesis that grass forage is an initiating factor to chronic diarrhea/wasting and further hypothesized that grass, alfalfa, and other agriculture-based forages in association with an anaerobic bacteria produce inflammatory bowel disease (IBD) in moose. Captive moose that had ad libitum access to a wood-fiber pelleted moose diet and grazed in grass pastures developed chronic wasting symptoms at 2–4 years of age and died at 4.7 ± 0.3 years unless restricted from grass before the development of advanced symptoms. We isolated Bacteroides vulgatus in the feces and successfully treated a moose with chronic diarrhea/wasting disease with long-term metronidazole therapy, suggesting that the chronic enteritis causing wasting disease arises from a bacteria-associated defective immunosuppressive response similar to IBD in other species. Further support for the IBD cause of wasting in moose is that this animal will relapse within hours if the metronidazole treatment is discontinued even after many months. We developed a highly palatable high-fiber, low-starch moose ration that can be fed as the sole source of nourishment, although additional research and dietary improvements are required. Zoo Biol 16:479–494, 1997. © 1997 Wiley-Liss, Inc.