Abstract

We present a review on the feeding practice, the nutritional pathology and the documented nutritional peculiarities of zoo ruminants. The difference in chemical composition between browse and grass historically led to the conclusion that browsers need a diet lower in fibre and higher in protein than grazing ruminants. The term “concentrate selectors”, coined to describe browsing ruminants, additionally focused the attention on the chemical nature of a browser’s diet assumed high in easily fermentable, soluble nutrients; the choice of the term “concentrate” therefore has been critized in the scientific literature (e.g. Owen-Smith 1996). In comparative nutritional surveys, browsing ruminants in zoos tend to consume less fibre, more protein and more nitrogen-free extracts than grazers. While this could be interpreted as a reflection of their nutritional needs, this feeding type displays, in comparative pathological surveys, a higher incidence of acidotic changes in the ruminal mucosa, indicating that this group does not ingest sufficient amounts of fibrous material. Additionally, data from controlled bilance trials does not support the notion that browsing ruminants have higher protein requirements. We suspect that the lesser fibre intake in browsers is due to their reluctance to ingest hay, which is usually offered ad libitum. Reluctance to ingest hay and digestive problems after hay ingestion have been reported for different captive browsing ruminant species and is reflected by a similar reluctance of free-ranging browsers to ingest grasses. There is reason to believe that it is the physical rather than the chemical difference between grass and browse that affected the evolution of different ruminant feeding types. Attention within the zoo community should focus on providing browsers with a fibre source that corresponds to the physical characteristics of their natural forage.

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