Energy supply of the okapi in captivity: fermentation characteristics of feedstuffs
A variety of feeds are used in the nutrition of browsing ruminants. During digestion trials on okapis, feedstuffs of different facilities were sampled and the Hohenheim gas test was used as in vitro fermentation method to quantify their fermentative behavior.
Forty-six feeds were analyzed (7, fruit and vegetable; 11, energy concentrates and pelleted compounds; 13, forage; 9, browse leaf; 6, small and large twig samples). Gas production of these samples was recorded after 2, 4, 6, 8, 10, 12, and 24 hr of fermentation. Browse leaf samples were additionally analyzed with a tannin-binding agent (polyethylene-glycol) to assess limiting effects of condensed tannins. Metabolizable energy (ME) was estimated from 24 hr gas production according to standard regressions. Vegetables and particularly fruits were found to yield very high gas productions during the first 2 hr of fermentation, whereas unmolassed beet pulp was found to have a more even distribution of gas production/energy release over total fermentation time. Feeds like rolled oats or bread were evaluated to yield very high energy contents of >14 MJ ME/kg dry matter (DM). Alfalfa (Medicago sativa) hay had a comparable fermentation pattern to fresh browse samples, characterized by a high fermentation rate. In conclusion, energy-rich constituents for captive ruminant diets should not include larger amounts of vegetables and especially fruits, due to their very fast fermentation during the initial phase of fermentation and the connected risk of rumen acidosis. Energy-concentrates like beet pulp (unmolassed) showed moderate fermentation characteristics and energy content and are well suited as a component of zoo ruminant diets. Energy-concentrates with very high energy densities (>13 MJ ME/kg DM) like bread or rolled oats are not suitable for a diet that is intended to promote long feeding times. Various aspects are involved in the decision for appropriate forage for browsing ruminants; based on fermentation pattern, alfalfa hay seems to be a reasonable substitute for browse leaves.
Title: Energy supply of the okapi in captivity: fermentation characteristics of feedstuffs
Authors: Jürgen Hummel, Gunther Nogge, Marcus Clauss, Camilla Nørgaard, Kristina Johanson, Joeke Nijboer, Ernst Pfeffer