Research Article: Body condition and adrenal glucocorticoid activity affects metabolic marker and lipid profiles in captive female elephants in Thailand

Date Published: October 2, 2018

Publisher: Public Library of Science

Author(s): Treepradab Norkaew, Janine L. Brown, Pakkanut Bansiddhi, Chaleamchat Somgird, Chatchote Thitaram, Veerasak Punyapornwithaya, Khanittha Punturee, Preeyanat Vongchan, Nopphamas Somboon, Jaruwan Khonmee, Elissa Z. Cameron.

http://doi.org/10.1371/journal.pone.0204965

Abstract

Studies in western zoo elephants have found relationships between body condition and physiological function, and identified mitigating management strategies to optimize health and welfare. A similar methodological approach was used in this study, which evaluated a body condition score (BCS; 1 = thinnest, 5 = fattest) every other month and fecal glucocorticoid metabolite (FGM) concentrations twice monthly in 33 tourist camp elephants in Thailand for a 1-year period to assess seasonal variations, and determine how lipid profiles [total cholesterol (TC), low density lipoproteins (LDL), high density lipoproteins (HDL), triglycerides (TG)] and metabolic parameters [insulin, glucose, fructosamine, glucose to insulin ratio (G:I)] related to measures of body condition and adrenal function. The most prevalent BCS was 3–3.5 (60.6%), with 27.3% at BCS = 4 (overweight) and 12.1% at BCS = 4.5–5 (very overweight); no elephants had a BCS <2. BCSs were higher in rainy and winter seasons compared to summer, with FGM, TG, HDL, LDL, and insulin also higher in the rainy and/or winter seasons (p<0.05). By contrast, TC and glucose were lowest in the rainy season. FGM measures were negatively associated with two environmental factors: temperature and rainfall, but not humidity. Positive correlations were found between BCS and TC, LDL, and HDL, and between FGM and TC, HDL, glucose, and insulin (p<0.05), whereas BCS and FGM were both negatively associated with the G:I (p<0.05). However, there was no relationship between BCS and FGM among the camp elephants. Using BCS and FGM measures as outcome variables in separate regression models, this study found high BCS and elevated FGM concentrations were associated with altered lipid profiles and metabolic status in elephants. Furthermore, more work hours/day was associated with better body condition and health measures. Thus, being overweight and exposed to factors that increase adrenal activity could adversely affect health status, requiring alterations in management for some individuals, whereas exercise appears to have a protective effect.

Partial Text

Healthy populations of elephants are essential to long-term global conservation, especially in the face of declining numbers. Wild elephant numbers throughout Asia have declined at least 50% over the last three generations, and without changes to conservation management, some populations are bound to disappear within the next century [1, 2]. Captive propagation is one strategy to ensure species survival [3], especially when conducted in range countries [4]. However, many Asian elephant (Elephas maximus) populations ex situ are not self-sustaining due to poor reproduction [5] or health problems [6–8].

Descriptive FGM, BCS, metabolic marker, and lipid profile measures are presented in Table 2, highlighting the variability in mean and range values across individuals. BCSs ranged from 2 to 5, with none scoring BCS = 1 or 1.5. Based on the yearly average of monthly mode values, numbers of elephants in each BCS category were: BCS = 2 (N = 1), BCS = 2.5 (N = 0), BCS = 3 (N = 14), BCS = 3.5 (N = 6), BCS = 4 (N = 7), BCS = 4.5 (N = 3), BCS = 5 (N = 2). Most elephants (42.4%) were a BCS = 3, with 33.3% scoring BSC = 4 and 5. Relationships between BCS and FGM on metabolic markers and lipid profiles are presented in Table 3. There were significant positive associations between BCS and TC, HDL and LDL. Fecal GC metabolite concentrations also were positively related to TC and HDL, as well as glucose and insulin. Both BCS and FGM were negatively correlated to G:I ratios. In separate Pearson’s correlation analyses of individual means (n = 33), FGM levels were similarly correlated to TC, LDL, glucose, insulin, and fructosamine (p<0.05) (Fig 1). Work time (hours per day) was negatively correlated with FGM concentrations (r = -0.69, p<0.01), HDL (r = -0.51, p<0.01), glucose (r = -0.78, p<0.01), fructosamine (r = -0.59, p<0.01) and insulin (r = -0.59, p<0.01), whereas the G:I was positively associated with work time (r = 0.32, p<0.05). This was the first study to evaluate relationships between BCS and metabolic factors in Asian elephants in any range country, and the first to assess lipid profiles in relation to body condition in this species. We also present new evidence for a relationship between nutritional status and stress hormone levels in elephants, as indicated by associations between FGM concentrations and several measures of metabolic and lipid function. The most prevalent (mode) BCS in Thai elephants was 3–3.5 (60.6%), which is considered ideal [17]. Deviations from that were mostly in the higher BSC categories, with 27.3% at BCS = 4 (overweight) and 12.1% at BCS = 4.5–5 (very overweight); no elephants had a BCS <2. Overall, the working elephants in our study had better body condition than those in western zoos. For example, in the U.S. only 16.5% had a BCS = 3; 27% were BCS = 4 and 48% were BCS = 5 [17], whereas 75% were scored as overweight or very overweight in the U.K. [47]. This could be due to higher amounts of exercise, with tourist elephants engaged in many activities, including trekking, bathing, shows or walking with tourists [48], so inactivity is less of a concern. In the U.S., elephants that walked more than 14 hours/week had a decreased risk of BCS = 4 or 5 [17, 28]. Feeding diversity (i.e., presenting food in multiple ways) also was related to lower BCS in U.S. studies [17, 28]. Comparatively, there is little diversity in how tourist camp elephants are fed, which are given fodder throughout the day, even during trekking. Thus, increased exercise during tourist activities likely helps those elephants maintain better body condition, and in this study, elephants that worked more hours per day in the form of saddle or bareback riding had lower BCSs. Using BCS and FGM as outcome variables in regression models, high BCS and FGM were predictors of higher and potentially unhealthy metabolic and lipid levels in female Asian elephants. This study provides the first evidence that altered metabolic marker and lipid levels are associated with high BCS and adrenal steroid hormone measures in tourist camp elephants in Thailand, and that problems may be exacerbated during the high tourist season (winter and rainy seasons). Future studies will focus on what factors specifically affect elephant health and well-being, and the potential benefits of limiting the amount of high calorie treats (bananas, sugar cane) given to elephants by tourists, ensuring animals receive appropriate levels of exercise to reduce fat and increase muscle mass, and reducing stress by limiting workloads and numbers of tourists interacting with individual elephants, especially during the high season.   Source: http://doi.org/10.1371/journal.pone.0204965

 

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