fistulated steers. Van Dyne (1962) has reported 
good success with steers and sheep. Other work- 
ers also have used the esophageal fistula in cat- 
tle and sheep for diet sampling.t The Wyoming 
Station has used the esophageal fistulae in 
sheep (Blackstone et al. 1965; Strasia 1968) 
and cattle (Jefferies 1968) with good success. 
In one study (Strasia 1968) esophageal-fistu- 
lated sheep were used to study diet habits on 
alpine range. They were left unattended for up 
to 1 month without supervision. No losses oc- 
curred due to fistulation. 
The esophageal technique has not been used 
appreciably with wild ruminants because the 
collection of ingested forage samples requires 
that the animals can be caught easily and that 
their normal grazing habits be disturbed as lit- 
tle as possible. A deer has been fistulated at the 
Engeling Wildlife Management Area at Ten- 
nessee Colony, Tex.,® but the animal has so far 
not been used for diet collections. 
DEVELOPMENT AND USE OF RUMEN 
FISTULAE 
The rumen fistula is a permanent opening 
into the ruminal-reticular area of the animal. 
It is usually placed in the paralumbar fossa on 
the left side of the animal where the rumen 
lies very close to the outer wall. This type of 
fistula is easy to establish and to maintain. It 
apparently has little if any effect on the nor- 
mal functioning and activities of the animal 
(Drori and Loosli 1959). 
The use of the rumen-fistulated animal for 
the collection of diet samples has been de- 
scribed. The procedure involves the complete 
emptying of the rumen of the collector animal. 
After the animal has grazed for a period of 
time, the rumen is again evacuated. The col- 
lected material then undergoes botanical and 
chemical analyses. 
The rumen fistula technique has limitations. 
It is restricted to cattle or to other large rumi- 
nants; it involves time and effort for the opera- 
tor to remove 20-50 gallons of rumen ingesta 
before sampling. The physiologic effect of an 
empty rumen must be considered. The removal 
of the rumen contents must stimulate an imme- 
diate influx of fluids from other body spaces 
and may initiate a strong stimulus for food in- 
take. With the urge to fill the empty rumen, 
the animal probably grazes in an abnormal 
pattern, and may be much less selective than 
normal. Emptying the rumen as seldom as 
*Torell 1954; Bath et al. 1956; Weir and Torell 
1959; Edlefsen et al. 1960; Chapman and Hamilton 
1962; Arnold et al. 1964; Hoehne et al. 1967. 
* Personal correspondence with G. H. Veteto and R. 
M. Robinson, Engeling Wildlife Management Area, 
Route 1, Tennessee Colony, Tex., 1968. 
° Lesperance et al. 1960, Shumway et al. 1963, Cable 
and Shumway 1966, Malechek 1966. 
128 
three times weekly had a depressing effect on 
the digestibility of forage in rumen-fistulated 
animals (Lesperance and Bohman 1963). 
Taylor and Deriaz (1963) circumvented some 
of the problems of esophageal rumen evacuation 
by obtaining ingested boli of food at the eso- 
phageal orifice. An attendent caught ingested 
boli by walking alongside a rumen-fistulated 
animal while it was grazing. This system lim- 
its the distance traveled by the animal and the 
number of animals which can be handled con- 
veniently. 
Except for the research by Lesperance et al. 
(1960), the rumen evacuation technique has 
not been compared with esophageal fistulation 
for sampling the diet of grazing animals. The 
esophageal and ruminal fistula samples were 
similar in chemical composition, however, the 
esophageal samples contained more nitrogen- 
free extract. 
BOTANICAL ANALYSES OF FISTULA 
SAMPLES 
There are many methods of estimating the 
botanical composition of the grazing animal’s 
diet (Ward conference paper). The samples 
collected by either the rumen or esophageal fis- 
tula method should be comparable. These are 
usually collected in bolus form, saturated with 
saliva, and partially chewed. There may be 
large particles of feed mixed with small frag- 
ments. Care should be taken so that these sam- 
ples are not contaminated with regurgitated 
feed. Cook et al. (1958) found that browse 
plants could be identified in fistula samples, 
whereas grass species were too finely masti- 
cated for visual appraisal. 
Heady and Torell (1959), using a micro- 
scopic-point technique, found that trained per- 
sonnel could make identifications with a mini- 
mum of error. Malechek (1966) depended 
upon a microscopic technique for identifying 
finely ground fragments from rumen-fistulated 
steers. 
Van Dyne and Heady (1965) reported that 
the grazing habits of cattle and sheep were dif- 
ferent. Sheep selected a higher quality diet 
containing more forbs and grass leaves than 
did cattle. Where quantitative botanical anal- 
ysis of the diet was desired, large numbers of 
animals were required because of variability 
among animals in diet selection. However, for 
a reasonable number of animals, the diet could 
be accurately sampled. 
In a Wyoming study (Strasia 1968), sheep 
selected a diet which contained a greater pro- 
portion of forbs than grass early in the graz- 
ing season: 73 percent in July, 52 percent in 
August, and 40 percent in September. The ni- 
trogen content of the diet declined as the forb 
content decreased; however, the fiber, lignin, 
