Deer Browsing and Rumen Microbial Fermentation of Douglas-Fir as Affected By Fertilization and Growth Stage

Abstract

Abstract The growth rate and crude protein level of Douglas-fir seedlings growing on nitrogen-deficient soil were increased during the first growing season following fertilization with nitrogen, as were acceptability to deer and in vitro fermentability by deer rumen microbes. The growth rate, crude protein level, and acceptability remained higher during the second growing season after fertilization, although fermentability differences between fertilized and unfertilized trees could no longer be detected. Deer browsing on Douglas-fir was limited to new growth throughout the study. New growth was consistently more fermentable and higher in crude protein than old needles, but old needles appeared higher in reducing sugar. Essential oils from Douglas-fir had an inhibitory effect upon rumen microbes, and oils from old needles were more inhibitory than those from new growth. Forest Sci. 16:21-27.