The Relationships Among Nutrition, Soil Ingestion And Anthrax Occurrence In Zebra And Springbok In The Etosha National Park Of Namibia

ABSTRACT

The relationship among animal nutrition, soil ingestion and the seasonality of anthrax occurrence in zebra and springbok in the Etosha National Park of Namibia was examined. The nutrient content of zebra and springbok faeces was determined in wet and dry seasons for a period of two years. Nutrient content was also determined for a dominant grass species (Enneapogon desvauxii) eaten by zebra. Faecal Crude protein (FCP), faecal phosphorus (FP) and faecal crude fibre (FCF) were assessed as indicators of forage quality. Springbok had a significantly higher faecal CP, P and lower CF content compared to zebra in all seasons. Faecal CP and P were significantly higher in wet seasons than dry seasons while faecal CF were lower in the wet seasons than dry season. It appears that the CP and P content of the faeces reflect the CP and P content of the diet. Also CP and P content of diet follows rainfall patterns. Concentration of silicate (soil) in faeces of springbok and zebra was also estimated, to determine why anthrax occurrence is seasonal, since ingestion of soil exposes animals to the anthrax bacterium. Results indicated that zebra had significantly higher silicate (soil) ingestion compared to springbok. Also the faeces of both species had significantly higher crude silicate content in wet seasons compared to dry seasons. Results also indicated that there was a positive correlation between the seasonality of faecal silicate content and anthrax occurrence in both animals. Faecal crude protein (FCP) of springbok ranged between 9.74 and 12.62% while that for zebra was 6.92 to 8.51% which is higher than the recommended nutrient requirement (6%) all the seasons (wet and dry) while faecal phosphorus FP of springbok ranged from 0.21-0.41% while that zebra is 0.26-0.41% which is higher than the critical value of 0.2% all seasons. Results show that these animals are not nutritionally stressed, so nutritional stress is unlikely related to the timing of anthrax outbreaks in Etosha, iii however their feeding behaviour may affect how and when these herbivores contact the anthrax bacterium in Etosha.