Variation in zoo diets, offerings of leafy browse, and body condition scores in Matschie’s tree kangaroos (Dendrolagus matschiei) and their effects on the composition of the gut microbiome

Recommended zoo diets for the arboreal folivore, the Matschie’s tree kangaroo (Dendrolagus matschiei; TKs), were recently found to be much lower in fiber and higher in starch than wild diet items for this species. In contrast to wild animals, zoo-housed TKs are ~30-40% higher in body weight, known to suffer from infections indicating immune dysfunction, and exhibit various reproductive issues. These problems may have ties to gut microbiome dysbiosis related to differences in diet between captive and wild individuals, but to date, the microbiome of TKs has not been explored. This study aimed to 1) quantify the macronutrient intake of diets from zoo-housed TKs and compare the intake of over-conditioned animals to those at ideal body condition, and 2) examine gut microbial communities for any differences associated with TK macronutrient intake, leafy browse offerings, or body condition. Diet information and associated fecal samples (n = 57) for microbial analysis were collected from 31 individuals at 16 facilities accredited by the Association of Zoos and Aquariums (AZA). Diet intake results confirmed suspected extreme macronutrient differences between zoo diets and food items consumed by wild individuals, with some zoo animals consuming as many as three to four times more calories than is currently recommended; these animals also being those with the highest body weights and condition scores in the population. The high caloric diets consumed by over-conditioned animals were driven by elevated protein and starch intake. TKs offered high and intermediate amounts of leafy browse in their diets exhibited substantially different fecal microbial communities compared to animals offered low or no browse. Our results indicate that formulation of diets for zoo-housed TKs, similar to other folivores, should closely resemble the macronutrient and caloric values of wild counterparts to encourage ideal body condition and promote gastrointestinal health.