Liver function profiles with special emphasis on bile acids in sloth bears (Melursus ursinus): Influence of age and sex

Introduction

The Sloth bear (Melursus ursinus) is an insectivorous ursid native to the Indian subcontinent and is currently listed as "Vulnerable" by the IUCN and protected under Schedule I of the Wildlife (Protection) Amendment Act (2022). Threats including habitat loss, fragmentation, and anthropogenic conflict have led to significant population declines (Dharaiya et al., 2016) [2] . Wild carnivores in managed care often exhibit unpredictable temperaments, complicating clinical evaluation. Accordingly, reliable clinical pathology reference intervals are indispensable for health monitoring and decision-making. Serum biochemical profiles offer insight into metabolic status, organ function, and early subclinical disease (Geffré et al., 2009; Friedrichs et al., 2012) [5,6] , and are influenced by age, nutrition, stress, activity level, and captivity-related factors (Dontas et al., 2011; Janyamethakul et al., 2017) [3,8] . Previous work has documented biochemical and haematological values in sloth bears (Veeraselvam et al., 2014; Arun et al., 2019) [1,13] , but detailed assessments of hepatobiliary markers particularly bile acids are lacking. Bile acids play an essential role in lipid digestion, nutrient absorption, and cholesterol metabolism (Engelking et al., 1980; Sutherland, 1989) [4,12] , and are sensitive indicators of hepatobiliary function (Schlesinger & Rubin, 1993) [10] . Despite their diagnostic relevance, bile acids have been studied in only a few ursid species (Ursus arctos; Graesli et al., 2014 and Ursus americanus; Solá et al., 2006) [7,11] . This study provides the first characterization of bile acids and associated liver biochemical parameters in captive sloth bears. It further evaluates age-and sex-related differences to generate clinically relevant baseline values to support veterinary care and conservation management.

Materials and Methods

Study population

Eighty-five rehabilitated sloth bears housed at the Agra Bear Rescue Facility (Wildlife SOS, India) were included. Bears were categorized into two age groups: Group I (≤ 15 years): N=10 (8 males, 2 females) and Group II (≥ 16 years): N=75 (29 males, 46 females). All individuals received a consistent diet comprising seasonal fruits and multigrain porridge.

Sample collection and biochemical analysis

Blood samples were collected from the cephalic vein using operant conditioning techniques (Maharana et al., 2025) [9] and standard vacutainer systems. Serum was separated after clotting and centrifugation. Ten liver-associated biochemical parameters were analyzed using a Catalyst One chemistry analyzer (IDEXX Laboratories): ALB, ALKP, ALT, AST, BA, GGT, GLOB, LDH, TBIL, and TP.

Statistical analysis

All analyses were performed in R (version 4.5.0). Descriptive statistics included means, standard deviations, and 95% confidence intervals. Independent t-tests evaluated differences between age and sex groups. Significance was set at p<0.05.

Results and Discussion

Across the study population, body weight did not differ significantly between age groups.

Age-related differences No significant differences were observed between age groups for ALB, ALKP, ALT, AST, BA, GGT, LDH, or TBIL (Table 1). GLOB was higher in older bears, although not significantly so. TP was significantly higher in older bears (P=0.042), consistent with age-associated increases documented in other URSIDS (Graesli et al., 2014) [7] .

Sex-related differences Among bears ≥ 16 years, females displayed significantly higher BA concentrations than males (P=0.015). No sexbased differences were observed for the remaining parameters (Table 2). Hormonal or metabolic factors may contribute to these findings, aligning with similar observations in other bear species (Solá et al., 2006; Graesli et al., 2014) [7,11] . To further illustrate these patterns, scatter plots with overlaid boxplots were generated for all parameters (Figure 1). These visualizations show overlapping distributions across most age-sex categories.

Acknowledgment

The authors express their sincere gratitude to the Co-Founders of Wildlife SOS, Mr. Kartick Satyanarayan and Ms. Geeta Seshamani, for their visionary leadership and unwavering support. We also thank the Uttar Pradesh Forest Department for their continued collaboration, and extend our appreciation to the Wildlife SOS animal care staff for their dedicated efforts and valuable contributions to this program.

Conclusion

This study provides the first baseline reference values for bile acids in sloth bears and demonstrates age-related differences in total protein and sex-related differences in bile acid concentrations. These results support improved clinical assessment, monitoring, and management of captive sloth bears.

Conflict of Interest Not available

Financial Support

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