Species and individual rhinoceros affect the bacterial communities, metabolites, and nutrient composition in faeces from Southern black rhinoceros (Diceros bicornis minor) and Southern white rhinoceros (Ceratotherium simum simum) under managed care

Abstract

Gut microbiota are essential to nutrient metabolism and the maintenance of hindgut health. The characterization of faecal bacterial communities from healthy individuals is important for the establishment of baseline data that can be compared to periods of gut dysbiosis. Diet is a key determinant of the faecal microbial community structure and generation of volatile fatty acids, a main energy source for the host. While rhinoceroses are herbivores, black rhinoceroses are browsers and white rhinoceroses are grazers. The objective of our study was to characterize and compare diets, faecal bacterial communities, nutrients and metabolites between and amongst Southern white rhinoceroses and Southern black rhinoceroses (n = 3 rhinos/species) managed at Disney's Animal Kingdom^® . Faecal bacterial communities were similar between individual white rhinos and dissimilar between species and individual black rhinos. Faecal butyrate and propionate molar proportions and concentrations were greater in black rhinos than white rhinos, whereas lactate was greater in white rhinos. The Shannon diversity, total operational taxonomic units, and relative abundance of Firmicutes were greater in white than black rhinos. The relative abundance of Proteobacteria in faeces from black rhinos was 3-fold greater than from white rhinos. One black rhino had a greater relative abundance of Verrucomicrobia (7.45 ± 1.31%) than all other individual rhinos (0.01-1.37%). White rhinoceroses demonstrated similar abundances of bacterial phyla and communities between one another and by individual, while black rhinoceroses were more dissimilar by individual. The dissimilarities between black rhinos were suspected to be due to total diet consumption variability, including browse diversity, and lack of direct contact. In contrast, the white rhinos commingled (i.e. nose-to-nose contact) and consumed similar amounts of hay, pellets and training items. These results suggest that species-specific diets and the individual contribute to differences in faecal bacterial communities, nutrients and metabolites between black and white rhinos housed at the same institution.

Keywords: VFA; diversity; inter-animal; microbiota; rhinoceroses; rhinos.

FIGURE 1

(a) Non‐metric multidimensional scaling (nMDS) plot of Bray‐Curtis dissimilarity comparing faecal bacterial community structures between rhinoceros species (n = 36 faecal samples/species). (b) nMDS plot of Bray‐Curtis dissimilarity comparing faecal bacterial community structures between individual rhinoceros (BR, black rhinoceros; WR, white rhinoceros) (n = 12 faecal samples/individual). BR1 and BR2 are adult males. BR3 and all WR are adult females. Stress = 0.17, RMSE = 0.90 [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 2

Venn diagram of total shared bacterial operational taxonomic units between rhinoceros species (BR, black rhinoceros; WR, white rhinoceros) (n = 72 total faecal samples, 12 samples/individual)

FIGURE 3

Boxplots comparing the (a) total operational taxonomic units and (b) Shannon diversity indices between individual rhinoceroses (BR, black rhinoceros; WR, white rhinoceros). Means within boxplots with different letters a,b, or c are significantly different (p < 0.05). Black dots represent the diversity measure from individual faecal samples (n = 12 samples/individual) [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 4

Boxplots comparing the mean relative abundances of faecal bacterial phyla between individual rhinoceroses (BR, black rhinoceros; WR, white rhinoceros). Means within boxplots with different letters a,b, or c are significantly different (p < 0.05). Black dots represent the phylum relative abundance of individual faecal samples (n = 12 samples/individual) [Colour figure can be viewed at wileyonlinelibrary.com]