An in vitro evaluation of browser and grazer fermentation efficiency and microbiota using European moose spring and summer foods

Abstract

Evolutionary morphological and physiological differences between browsers and grazers contribute to species‐specific digestion efficiency of food resources. Rumen microbial community structure of browsers is supposedly adapted to characteristic nutrient composition of the diet source. If this assumption is correct, domesticated ruminants, or grazers, are poor model animals for assessing the nutritional value of food consumed by browsing game species. In this study, typical spring and summer foods of the European moose (Alces alces) were combined with rumen fluid collected from both dairy cows (Bos taurus) and from moose, with the aim of comparing fermentation efficiency and microbial community composition. The nutritional value of the food resources was characterized by chemical analysis and advanced in vitro measurements. The study also addressed whether or not feed evaluation based on in vitro techniques with cattle rumen fluid as inoculum could be a practical alternative when evaluating the nutritional value of plants consumed by wild browsers. Our results suggest that the fermentation characteristics of moose spring and summer food are partly host‐specific and related to the contribution of the bacterial phyla Firmicutes and Bacteriodetes to the rumen microbial community. Host‐specific adaptations of the ruminal microbial community structure could be explained from the evolutionary adaptations related to feeding habitats and morphophysiological differences between browsers and grazers. However, the observed overall differences in microbial community structure could not be related to ruminal digestion parameters measured in vitro. The in vitro evaluation of digestion efficiency reveals that equal amounts of methane were produced across all feed samples regardless of whether the ruminal fluid was from moose or dairy cow. The results of this study suggested that the nutritional value of browsers' spring and summer food can be predicted using rumen fluid from domesticated grazers as inoculum in in vitro assessments of extent of digestion when excluding samples of the white water lily root, but not of fermentation characteristics as indicated by the proportions of individual fermentation fatty acids to the total of volatile fatty acids.

Macronutrient balancing in free‐ranging populations of moose

“…There are thus indications that foraging in moose, like primates, is driven by nutrient balancing. However, given the important role of fermentation in the rumen of cervids, and the significant variation in the fiber content of forage (Krizsan et al, 2018), we anticipate that if free-ranging moose regulate their dietary macronutrient balance, then dietary fiber content will play a role. For example, ingested fibers not only provide ruminants with energy through fermentation, as long as nitrogen is available in the feed, but also indirectly provide protein from fiber-utilizing microorganisms (Dahl et al, 2020).…”

Comparing Antibiotic Resistance in Free-Ranging vs. Captive African Wild Herbivores

“…Interestingly, plains zebra is the only monogastric and strict grazer species among the three species studied. Despite many studies on ruminal composition, there is a general lack of data on differences between grazers and browsers in terms of composition and structure of the digestive tract microbiome (Krizsan et al 2018), and no link between rumination and AMR has been found to our knowledge. Because the bacterial burden ingested with grass is linked to the soil microbiome, it is likely to be more important in diversity and quantity compared with those covering leaves above the ground and exposed to ultraviolet light.…”

Circum‐Arctic distribution of chemical anti‐herbivore compounds suggests biome‐wide trade‐off in defence strategies in Arctic shrubs

“…Dry leaf material was mixed with rumen fluid from dairy cows and incubated at 38°C for 96 h, and the proportion of digested organic matter was then calculated, all according to Lindgren (1979). Although plant digestibility can be herbivore species‐specific to some extent, overall differences in digestibility of food plants to different grazers and browsers can be estimated by in vitro organic matter digestibility with rumen fluid from dairy cows (Krizsan et al 2018). The analyses were done at HUV Analysis Laboratory, Swedish Univ.…”