I found this on Red Alder leaves:
https://www.fs.fed.us/pnw/pubs/pnw_rp246.pdfCopy and paste created a lot of typos, but it is still understandable: ( Higher fats and carbs, good protein than during the growing season. Very good pre-winter food source.)
"Chemical Composition and Deer Browsing of Red Alder Foliage"Discussion and Conclusions
Results show that in June when
utilization by deer was minimal,
red alder leaves contained adequate
levels of minerals, available carbohydrates,
protein, and fats to satisfy
the nutritional needs of herbivores,
including deer (Maynard 1951) . The
leaves were also succulent, moderately
acidic, had enough roughage as shawn
by the contents of fiber and lignin,
and contained nontoxic levels of
nitrates as well as fatty acids which
are usually found in palatable plants.
The total phenols in the leaves,
however, were quite high; they anounted
to over 10 percent of the dry natter
and greatly exceeded levels found in
plants bravsed by black-tailed deer
in winter (Radwan and Crouch 1974) .
Comparison of the June and
Septerrber leaves indicated many variations
in most chemical constituents.
Thus, as leaves grew older and becane
more preferred by deer in Septenber,
moisture, acidity, protein, and phenols
had decreased, while available carbohydrates
and fats were increased.
Fatty acids also changed in their
conposition during the sane period of
tine. Cbviousl y, it is impossible to
state which change or conbination of
changes were actually responsible for
the increased preference or the nechanism
by which any of these factors were
operating. One nay speculate, havever,
that changes in fats and phenols were
the irr[x::>rtant factors. That changes
in these two leaf constituents were
much greater than those shawn by renaining
constituents tends to support
this speculation. Crude fat also is
recognized as a high energy food source
for animals, and associations of high
fat contents in forages with high
preferenoe by sone animals have b
reported (Hardison et al. 1954, Iouw
et ale 1967) . Phenols, on the other
hand, have been generally considered
as defense conpounds which protect
plants from their natural enemies,
including herbivorǜs (Levin 1971) .
Furthernore, tannins, which are
estimated here as total phenols,
have been shawn to reduce palatability
and digestibility of some
plants in ruminants (Wilkins et ale
1953, Donnelly and Anthony 1973) ;
and their great decline in Septerrber
could very well account for the increased
utilization of the leaves in
the fall.
Factors affecting animal preferences
for plants are extrerrely varied
and conplex. Accordingly, we recognize
that chemical constituents other than
those reported here or nonchemical
factors such as differences in availability
of preferred food nay have
influenced deer preference.
