176 
As a group, the grasses Dupontia fisheri and 
Arctophila fulva were more highly _ digest- 
ible than the herbs, sedges, or shrubs (Table 18). 
With one exception, all herb samples proved 
highly digestible (64-70%), as were the sedges 
and cotton grass (48-68%). Digestibilities of 
salices were generally lower at 34-54%; however, 
a singularly high value of 71% was noted for 
Salix arctica when incubated with rumen liquor 
from caribou. Dryas integrifolia was of even 
lower digestibility (12-33%) than the willows. 
Unfortunately, no mosses and only two 
lichens, Cetraria cucul/lata and Cladonia alpestris, 
were available for estimation of digestibility 
using inocula from caribou or reindeer at Prud- 
hoe Bay. Both lichen samples were obtained 
from Coal Creek, Alaska. C. cucu//ata was highly 
digested (48-74%), whereas the digestibility of 
C. alpestris was low (16-27%). A more complete 
study using inoculum from reindeer given a 
prepared forage high in lichen showed that the 
digestibility of lichens was highly variable 
(10-77%) depending on the species. In contrast, 
the digestibility of three mosses was very low 
(6-19%) (Table 18). 
Estimates of jn vitro digestibility of forage 
samples obtained from esophageal fistulated 
reindeer were moderate to high at 45 to 62%. 
However, estimates using liquor obtained from 
caribou were lower at 37 to 43% (Table 18). The 
mean estimate of digestibility of the initial four 
esophageal egesta samples, 52 + 3%, was higher 
than the estimate for a combined sample (45%), 
using liquor obtained from reindeer given a diet 
high in lichen. 
In view of the wide range in digestibility of 
the vascular plant species and groups, it is 
difficult to predict a biologically meaningful 
average digestibility based on botanical composi- 
tion, without incorporating the relative amounts 
of each plant species available or eaten. From 
the mean botanical composition for 20 
esophageal fistula samples, shown in Table 
10(b), and estimates of digestibility of the 
species (Table 18), a mean digestibility was 
calculated which was weighted for the relative 
abundance of each species (Table 19). For the 
esophageal samples, a mean digestibility of 56% 
was obtained; this estimate was 4% higher than 
the mean jn vitro digestibility (52%) of four 
esophageal samples shown in Table 18, and is 
considerably higher than those estimated using 
inoculum from caribou rumen (37-43%). A 
similar calculation based on the botanical analy- 
sis of rumen contents from caribou (Table 11) 
indicated a dry matter digestibility of 52% for 
forage consumed by them. 
Table 19 
Comparison of jn vitro digestibility of esophageal egesta samples with dry matter 
digestibility calculated from the summation of individual estimates of digestibilities 
(Table 15) and the % occurrence of species in the vegetation types. 
Predicted dry digestibility based 
on botanical composition of: 
(a) range: (b) esophageal /n vitro digestibility 
Type live material total egesta of esophageal egesta 
Salix ovalifolia 15-17 47 — 44 ~ 
sand dunes 
Dryas integrifolia heath 2,9 44 41 50 49 
Salix integrifolia snowbed 53 50 
Dupontia fisheri 12 59 49 58 50 
brook meadow 
Eriophorum 3-4 50 38 43 49-62 
angustifolium marsh 
Carex aquatilis 5 62 51 56 51 
marsh 
