Effects of supplemental feeding on the fecal bacterial communities of Rocky Mountain elk in the Greater Yellowstone Ecosystem

Abstract

Supplemental feeding of wildlife is a common practice often undertaken for recreational or management purposes, but it may have unintended consequences for animal health. Understanding cryptic effects of diet supplementation on the gut microbiomes of wild mammals is important to inform conservation and management strategies. Multiple laboratory studies have demonstrated the importance of the gut microbiome for extracting and synthesizing nutrients, modulating host immunity, and many other vital host functions, but these relationships can be disrupted by dietary perturbation. The well-described interplay between diet, the microbiome, and host health in laboratory and human systems highlights the need to understand the consequences of supplemental feeding on the microbiomes of free-ranging animal populations. This study describes changes to the gut microbiomes of wild elk under different supplemental feeding regimes. We demonstrated significant cross-sectional variation between elk at different feeding locations and identified several relatively low-abundance bacterial genera that differed between fed versus unfed groups. In addition, we followed four of these populations through mid-season changes in supplemental feeding regimes and demonstrated a significant shift in microbiome composition in a single population that changed from natural forage to supplementation with alfalfa pellets. Some of the taxonomic shifts in this population mirrored changes associated with ruminal acidosis in domestic livestock. We discerned no significant changes in the population that shifted from natural forage to hay supplementation, or in the populations that changed from one type of hay to another. Our results suggest that supplementation with alfalfa pellets alters the native gut microbiome of elk, with potential implications for population health.

Fecal Bacterial Community of Allopatric Przewalski’s Gazelles and Their Sympatric Relatives

“…Previous studies of different types of mammals have revealed that their fecal microbiota and function cluster according to diet (herbivores, omnivores, and carnivores) rather than host phylogeny (Ley et al, 2008;Muegge et al, 2011). The microbiome composition of Rocky Mountain elk (Cervus canadensis nelsoni) that was supplied with alfalfa pellets changed compared to that in natural feed population (Couch et al, 2021b). In captive primates, gut microbiota cluster weakly by species, but strongly by diet, so that the gut microbiota is more similar when monkeys in the same genus are fed with the same diet, even if they are different species (Hale et al, 2018;Huan et al, 2020).…”

Human-mediated impacts on biodiversity and the consequences for zoonotic disease spillover

“…Similarly, agricultural conversion has limited the availability of high-quality winter resources for elk, which serve as reservoir hosts of Brucella abortus (Figure 2C). Large elk populations are now supported by lower-quality supplemental feeding, which reduces migration and promotes high-density aggregations, thereby increasing the spread of Brucella among these animals and potentially spillover to livestock [87][88][89][90] . Climate change may further exacerbate loss of phenological diversity and interrelated shifts in animal movement; however, this has not been explicitly linked to zoonotic spillover 91 .…”

Functional Diversity within Gut Microbiomes: Implications for Conserving Biodiversity

“…Taxonomic profiling involves quantifying the identity and abundance of the microbial taxa present in a sample [37]. By comparing taxonomic profiles of microbiomes sampled from individuals, populations or species subject to different conditions, such as climatic shifts [8], pollution [35], and captive management actions [16], it is possible to infer how these factors affect the microbiome and which host species may be most negatively affected. Comparing the taxonomic profiles of communities can also help explain how an individual's microbiome develops in response to environmental conditions and external microbial communities.…”

“…This example demonstrates how effective microbe-targeted conservation efforts can be at preserving biodiversity on a macro level. A study in elk (Cervus canadensis) also used this approach to show that supplementary feeding of populations with processed alfalfa pellets led to a shift in gut microbiome composition, whereas supplementation with unprocessed loose hay had no effect [16].…”

“…Captive breeding is only one avenue by which conservation action can influence microbiomes. Supplementary feeding of wild elk (Cervus canadensis) populations led to a significant shift in gut microbiome composition [16] and translocation of captive Tasmanian devils (Sarcophilus harrisii) saw them quickly re-establish their wild-type microbiome [17]. Thus, human actions, through both neglect of the environment and active conservation of it, can lead to major changes in microbial communities.…”