Effect of Increased Activity on Metabolic Markers in Captive Black Rhinos: A Pilot Study

Abstract

Ex situ (captive) black rhinoceros populations exhibit higher rates of disease than free-ranging counterparts. Preliminary data from an ongoing study supports the association between excessive adipose tissue, iron overload, insulin resistance and increased inflammatory markers in captive animals. This study hypothesized that an increase in activity level by 30 minutes daily at a moderate activity level for eight weeks would result in improvement in insulin sensitivity (measured by a decrease in the serum insulin-to-glucose ratio) and decreased inflammation (measured by TNF-alpha and serum amyloid A). Serum markers of body condition (leptin), inflammation (TNF-alpha, serum amyloid A), insulin sensitivity (insulin, glucose), phosphate and iron stores (ferritin) were to be measured further. An adult male and female at the Cleveland Metroparks Zoo were the subjects for this pilot study. ELISA assays were validated for measuring serum insulin, ferritin, TNF-alpha and serum amyloid A in black rhino. These assays were used to assess changes in markers of metabolic status from weekly serum samples collected during two weeks of baseline and 10 weeks of increased activity. Methods to increase activity included delaying feeding times by 30 minutes when the subject was already in motion, a call and reward system, playing fetch and jogging in the yard. The GT1 Actigraph, an accelerometer commonly used in field research, was used to establish baseline activity levels and measure activity levels during the 10-week interval of increased exercise. Studies demonstrated a significant (P < 0.001) increase in activity level above baseline in both the male and female black rhino. Serum metabolic markers indicated decreases in inflammation and iron stores with no significant change in insulin sensitivity.