and in vitro dry matter digestibility of the diet 
was relatively constant. Percent composition 
was as follows: 
July Aug. Sep. 
Nitrogen _________- 3.6 2.1 1.7 
Miber (eee. 3S 43.7 41.2 45.4 
igenin' 2 Seale Fos. 9.9 10.1 8.3 
In vitro dry matter 
digested ________ 42.4 42.8 43.5 
This tabulation indicates that the sheep grazed 
selectively and maintain a relatively constant 
quality of diet. They adjusted to differences in 
forage availability and quality by changing 
their species preferences. 
When using fistula collection procedures, in- 
vestigators are able to determine the prefer- 
ences of grazing animals for species of plants 
under many conditions and types of range. 
CHEMICAL ANALYSES OF FISTULA 
SAMPLES 
Ruminal or esophageal fistulae were devel- 
oped primarily to define the chemical composi- 
tion of the grazing animal’s diet. During col- 
lection, forage samples are thoroughly wet and 
mixed with saliva. Saliva is composed of water, 
minerals, and possibly nitrogen (McDougall 
1948). Cook (1964) found that saliva increased 
moisture, ash, and nitrogen in the forage col- 
lected by esophageal fistulae. Lesperance and 
Bohman (1964) and Blackstone et al. (1965) 
also reported an increased nitrogen content in 
forages as a result of salivary contamination 
during esophageal collections. Several other 
workers,’ however, did not report this condi- 
tion. 
Salivary contamination of fistula-collected 
forages with phosphorus has also been re- 
ported,® while calcium contamination has not 
been observed (Lesperance et al. 1960; Hoehne 
et al. 1967). 
The composition and amount of saliva se- 
creted by fistulated animals varies with the 
diet. Dry, coarse feeds stimulated a greater sal- 
ivary flow than succulent feeds (Lesperance et 
al. 1960). Somers (1961) and Bailey and Balch 
(1961) found that the nitrogen content of sa- 
liva was related to the nitrogen content of the 
diet. In Wyoming, Blackstone et al. (1965) ob- 
served that the salivary ash content was 
greater when esophageal-fistulated sheep ate 
lush forage than when they ate dry forage. 
More moisture was added to a dry grass sam- 
ple, while more ash was added to the fresh 
ee when collected through an esophageal fis- 
ula: 
“Lesperance et al. 1960; McManus 1961; Lombard 
and Van Schalkwyk 1968; Arnold et al. 1964; Lang- 
lands 1966; Hoehne et al. 1967. 
*Lombard and Van Schalkwyk 1963; Cook 1964; 
Langlands 1966; Hoehne et al. 1967. 
Before After Amount 
Fresh grass: collection collection added 
Percent Percent Percent 
Water __________ 62.7 85.0 22.4 
Ashe oe Meh oe 8.3 11.7 3.4 
Nitrogen ________ 2.8 3.0 2 
Grass hay: 
Water - 2.258... 9.3 82.0 bar 
Ash” seca ot 4.7 er 3.0 
Nitrogen ________ 1.4 1.8 A 
The dry matter, ash, and nitrogen content of 
saliva from steers maintained on native hay or 
alfalfa pellets (Cundy and Rice 1968) was as 
follows: 
Hay fed Pellet fed 
Gm./100 ml. Gm./100 ml. 
Dry matter ________ 1.13 1.13 
Nitrogen ___________ .005 010 
shigtia We aes ire 1.04 1.04 
Saliva from steers maintained on native hay (8 
percent protein) had a slightly lower nitrogen 
content than saliva from steers maintained on 
alfalfa pellets (18 percent protein). Esopha- 
geal samples collected from the alfalfa pellet- 
fed steers tended to have higher nitrogen con- 
tents and lower ash and lignin contents than 
those collected from steers fed native hay: 
Hay fed Pellet fed 
Percent Percent 
Dry matter ________________ 13.2 13.1 
IASG noi. 5 ot pees BSS one 11.4 13.1 
Nitrogen* —2.25.22.- 2222.2 2.9 2.7 
Cellulose* ________________- 30.6 28.1 
Acid detergent lignin’ ______ 2.0 2.7 
*Dry matter basis 
Since saliva adds considerable ash to esopha- 
geal samples, some investigators have proposed 
that the chemical composition of esophageal 
samples be reported on an ashfree basis (Cook 
1964; Hoehne et al. 1967). 
The method of handling esophageal samples 
after collection also appears to affect the chem- 
ical analyses. The fiber and lignin content of 
forages may be increased by drying samples at 
high temperatures (Van Dyne and _ Torell 
1964; Smith et al. 1967). A combination of 
temperature and moisture apparently causes a 
nonenzymatic browning reaction that increases 
the apparent fibrous content of feeds (Van 
Soest 1962). The soluble carbohydrates in 
plant material are lost rapidly unless the 
sample is frozen soon after collection. The sol- 
uble components of the diet may also be lost if 
saliva is allowed to drain off samples or if sa- 
liva is squeezed or rinsed out of the samples 
(Langlands 1966; Arnold et al. 1964; Hoehne 
et al. 1967). Smith et al. (1967) compared the 
effect of freeze drying with drying at 60° C. on 
the chemical analyses of esophageal fistula 
samples. They found that fiber and lignin were 
higher in the samples dried at 60° C. 
129 
