IAB Research Project Description

Comparative forestomach physiology in arctic ruminants - the basis for niche partitioning

Caribou cow and calf at the Institute of Arctic Biology Robert G. White Large Animal Research Station. Credit: IAB/UAF

Two two-year-old muskoxen calves stand amid snowflurries. Credit: IAB/UAF

Two two-year-old muskoxen calves stand amid snowflurries. Credit: IAB/UAF

Close-up view of a muskoxen's nose taken at the Institute of Arctic Biology Robert G. White Large Animal Research Station. Credit: Perry M. Barboza/IAB/UAF

Any and all uses of these images must include photographer credit.

Ruminants consume a broad range of plants from the leaves of woody shrubs and trees (browse) to the blades and stems of grasses. There is an ongoing debate about what determines dietary selection of each species and thus distinguishes browsers from grazers and intermediate feeders.

On one hand, observed differences in digestive structure and function are thought to reflect adaptations of different ruminant species to their respective ecological niches (browse vs. grass).

On the other hand, body size is considered as the sole adaptive factor. A large number of physiological observations suggest that differences in forestomach function determine feeding types both within and between species. These functional parameters include anatomy (differences in forestomach design), biochemistry (body composition), allometry (as limited by forestomach design), and physiology (forestomach protozoa, ingesta particle size, digestion efficiency).

Differences in digestive function among feeding types may also explain why browsers are difficult to maintain in captivity and have been suffering losses due to malnutrition for years. There is agreement in the literature that the passage of ingesta through the forestomach is a key parameter for distinguishing feeding types. Stratification of particles in the rumen is a common feature of domestic grazers such as cattle but ruminal contents of browsers and intermediate feeders may not stratify and flow in the same manner.

This project will test the hypothesis that the rumen contents of a browser are more viscous and less stratified than those of a grazer, and that there is a faster passage of fluid and a slower passage of particles in a grazer than a browser. Correspondingly, the separation of particles according to density will be more prominent in the grazer. These differences will be evident on a common diet and more prominent when both feeding types ingest their natural diet.

Project Funding

IAB Project #109

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