Evolutionary adaptations of ruminants and their potential relevance for modern production systems

Abstract

Comparative physiology applies methods established in domestic animal science to a wider variety of species. This can lead to improved insight into evolutionary adaptations of domestic animals, by putting domestic species into a broader context. Examples include the variety of responses to seasonally fluctuating environments, different adaptations to heat and drought, and in particular adaptations to herbivory and various herbivore niches. Herbivores generally face the challenge that a high food intake compromises digestive efficiency (by reducing ingesta retention time and time available for selective feeding and for food comminution), and a variety of digestive strategies have evolved in response. Ruminants are very successful herbivores. They benefit from potential advantages of a forestomach without being constrained in their food intake as much as other foregut fermenters, because of their peculiar reticuloruminal sorting mechanism that retains food requiring further digestion but clears the forestomach of already digested material; the same mechanism also optimises food comminution. Wild ruminants vary widely in the degree to which their rumen contents 'stratify', with little stratification in 'moose-type' ruminants (which are mostly restricted to a browse niche) and a high degree of stratification into gas, particle and fluid layers in 'cattle-type' ruminants (which are more flexible as intermediate feeders and grazers). Yet all ruminants uniformly achieve efficient selective particle retention, suggesting that functions other than particle retention played an important role in the evolution of stratification-enhancing adaptations. One interesting emerging hypothesis is that the high fluid turnover observed in 'cattle-type' ruminants -which is a prerequisite for stratification -is an adaptation that not only leads to a shift of the sorting mechanism from the reticulum to the whole reticulorumen, but also optimises the harvest of microbial protein from the forestomach. Although potential benefits of this adaptation have not been quantified, the evidence for convergent evolution toward stratification suggests that they must be substantial. In modern production systems, the main way in which humans influence the efficiency of energy uptake is by manipulating diet quality. Selective breeding for conversion efficiency has resulted in notable differences between wild and domestic animals. With increased knowledge on the relevance of individual factors, that is fluid throughput through the reticulo-rumen, more specific selection parameters for breeding could be defined to increase productivity of domestic ruminants by continuing certain evolutionary trajectories.Keywords: herbivory, hindgut fermenter, foregut fermenter, browser, grazer ImplicationsUnderstanding evolutionary adaptations of ruminants will have an impact on (i) husbandry of captive wild ruminants, many of which cannot be kept or fed as domestic ruminants and (ii) research for continuous refinement of the production potential of domestic ruminants, ...

Rumen microbial (meta)genomics and its application to ruminant production

“…Within herbivores, ruminants have enlarged their gastrointestinal tracts and increased the retention time of forages to facilitate the fermentation of feeds by their symbiotic microbes. Ruminants have evolved the most sophisticated system to harbour and take advantage of microbes in their forestomach (Stevens and Hume, 1998;Clauss et al, 2010), making them very adaptable to a large variety of diets. This is a characteristic that was certainly an important domestication trait (Diamond, 1997 and2002) and that can be attributed directly to microbes.…”

“…This is a characteristic that was certainly an important domestication trait (Diamond, 1997 and2002) and that can be attributed directly to microbes. The stratification of the rumen contents into gas, solid and liquid layers allows retention of particulate feeds for further processing while at the same time optimising the collection of microbial protein due to the high liquid turnover (Clauss et al, 2010). Ruminants also have a strong innate immunity in the digestive surfaces of the remainder of the gastrointestinal tract, and have recruited and duplicated enzymes such as lysozymes and ribonucleases to play a digestive role, allowing a better utilisation of the microbial biomass leaving the rumen (Benner et al, 2002;The Bovine Genome Sequencing Analysis Consortium et al, 2009).…”

Ruminants as Part of the Global Food System: How Evolutionary Adaptations and Diversity of the Digestive System Brought them to the Future

“…Hofmann classify ruminants in three different types (concentrate selectors, intermediate and grazers) using botanical and nutritive observations of the diet [43,44]. The terminology "concentrated selector" used for Hofmann as a description of browsing ruminants is recently avoided, since concepts that integrally describes both botanical and nutritive aspects have been developed, explaining evolutionary adaptation properly rather than the botanical approach only [19].…”

“…The production capability of domestic ruminants has changed for the past decades, either by the massive genetic improvements to attend the consumption demand, or by the natural evolution throughout the centuries [19]. Taking this background together, this review aims to depict the environmental and evolutionary aspects of domestic and wild ruminants, regarding the digestive conversion capability; morphophysiological differences among species and the prospective for the future in terms of effects on productivity in future evolutionary adaptation in livestock ruminants.…”

Resigning protein concentrates in dairy cattle nutrition: a problem or a chance?

“…Whereas for monogastric species the possibility to resign dietary concentrates is limited, the nutritional physiology of ruminants might allow for considerable reductions in this field. Due to their digestion physiology, which combines fermentation, chewing and particle sorting in a unique way, ruminants, in particular cattle, are able to degrade plant fibres very efficiently (Clauss et al, 2010) and to gain metabolizable energy from roughages which are poor in soluble carbohydrates like sugars or starch. This is the big advantage of ruminants compared to monogastric animals.…”