Body Size, Rumen-reticulum Functions, and Dietary Nutrition of White-Tailed Deer
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Ruminants have a highly specialized digestive system which allows them to obtain nutrients from fibrous forage. The morphology of this digestive system changes with respect to the quality and quantity of consumed forage. Few studies have explicitly examined variation in ruminant digestive system morphology in semi-arid environments at low latitudes. The aim of my dissertation was to examine scaling relationships of anatomical and physiological rumen-reticulum attributes, dietary nutrition, rumen-reticulum fill, reserve capacity, and surface area of rumen mucosa across a body mass gradient of white-tailed deer in a semi-arid environment. My findings indicate that scaling relationships between body mass and rumen-reticulum capacity were isometric. With regard to nutrition, juveniles and sub-adults consumed a higher quality diet (assessed by the ratio of protein to less digestible and indigestible carbohydrates), which should aid in meeting their high mass-specific metabolic demands. Factors governing rumen-reticulum function were complex because rumen-reticulum fill, reserve capacity, and absorptive surface area of the rumen mucosa were influenced by differing factors. One key finding was that surface area of the rumen mucosa had and inverse relationship with reserve capacity. This inverse relationship would allow individuals in a semi-arid environment to conserve metabolically expensive rumen-reticulum tissue, yet still allow them to accommodate sudden changes in forage quality. Additionally, my research indicates that white-tailed deer in a semi-arid environment had less pronounced seasonal changes in their surface area of rumen mucosa than deer at higher latitudes. My findings contain relevant information to intraspecific scaling relationships, forage niche partitioning, and anatomical patterns of the rumen-reticulum of deer inhabiting semi-arid environments.