BLOOD ANALYTE CHANGES ASSOCIATED WITH MUSTH IN TWO CAPTIVE ASIAN ELEPHANT (ELEPHAS MAXIMUS) BULLS

Musth is a normal behavioral phenomenon characterized by postpubertal, periodic elevations in circulating testosterone, resulting in behavioral and physical changes in sexually mature, healthy Asian (Elephas maximus) and African (Loxodonta africana) elephant bulls. To date, the understanding of the role that musth plays on blood analytes is limited. The objective of this study was to assess serial blood analyte data (hematology, serum biochemistry, acute phase proteins, cortisol, and testosterone) relative to periods of behavioral musth vs nonmusth in two Asian elephant bulls housed at a single institution over three years. Linear and generalized linear models were used to test for differences between musth and nonmusth periods, as well as for associations of each biomarker with testosterone. In both bulls, platelet count (PLT), alkaline phosphatase (ALP), cortisol, serum amyloid A (SAA), and testosterone were statistically significantly higher during musth compared with nonmusth periods. Both bulls also displayed positive covariations of testosterone with PLT and mature heterophils. Blood urea nitrogen had a significant inverse association with testosterone in both bulls. These changes may reflect physiologic stress, systemic inflammation, and decreased urea synthesis during musth. There were otherwise limited consistencies in blood analytes between bulls, possibly due to sample size, sampling period, or individual variations. For instance, ALP, c-glutamyl transferase, SAA, and testosterone were statistically significantly higher and considered clinically relevant during musth periods in bull 1; however, similar observations for clinical relevance were absent in bull 2. Though results should be interpreted with due consideration of biological variation and other factors in individual bulls, these data provide novel information for interpretation of routine blood analytes of Asian elephant bulls, for informing clinical decision-making, and for contributing to the understanding of physiologic changes during musth periods.