Tracey Papenfuss, BS

Supervisors: J. Braddock and R.G. White

Supporting Agency: Department of Biology and Wildlife

Different leaf colors are known to contain many different chemicals and substituents, leading to the question of whether the chemical differences in leak types indicate differences in nutritional value, and whether rates of microbial breakdown or overall rates of disappearance would differ substantially for leaf types. The microbial breakdown of different leaf types in the rumen of a fistulated reindeer is used as an indirect measure of the nutrient components("digestibility"). My hypothesis is that there should be no difference in rates of disappearance (log % remaining) in different leaf morphologies (green, yellow, and brown).

The experiment consists of in vivo incubations of ground, vacuum-dried leaf samples suspended in a reindeer's rumen for various lengths of time (0, 6, 12, 24, 36, 48 and 60 hrs.). Three incubations are performed over a three-week period during the winter. After incubation, the samples are washed, vacuum-dried, weighed and analyzed via a Kjehldahl nitrogen assay to obtain percent nitrogen and percent phosphorous.

The results indicate that there is a difference in the overall log percent remaining of the different leaf types, but not a difference in microbial rates of breakdown (i.e. the rate of disappearance). The rates of microbial breakdown for all leaves have a similar regression equation

(y=-0.0052x+1.904) but are offset from one another, probably due to the effects of a second exponential function: that of volatilization of leaf compounds. A necessary addition to future experiments is the analysis of starting leaf material (material which has not been washed or exposed to the rumen) and a larger sample size. The results of this experiment should be analyzed qualitatively due to a lack of statistical significance, but are useful as a preliminary study.