as well as for forage sampling, would under- 
estimate the intake of intact steers of compar- 
able size and condition. 
TABLE 1.—Comparison of fistulated and intact 
steers grazing range forage? 
Digestibility Average daily— 
Dry- 
intake Fecal Gain 
output ? 
Steer Dry Gross Crude 
treatment matter energy protein matter 
Percent Percent Percent kg. kg kg. 
Fistulated _ 35 36 48 $3.4 S22, 0.47 
Intact ___-- 385 36 48 *5.0 *3.3 .60 
*See footnote 4, p. 111. There were four steers/treat- 
ment and five observations/steer during a 97-day study 
period. 
* Dry-matter basis. 
*4 Means in same column with unlike superscripts 
differ significantly (P<.05). 
Ridley et al. (1963) reported that digestibili- 
ties were similar for rumen-fistulated and in- 
tact cattle. This report is in contrast to their 
Nevada studies (Lesperance and Bohman 1963; 
Connor et al. 1963). In these latter three stud- 
ies, rumen contents for fistula forage sampling 
were removed on 8 different days during the 
digestion trials. Rumen-fistulated animals may 
be used for digestibility studies if the rumen 
evacuations for forage sampling are not con- 
ducted during the digestion study. In many 
range studies, it would be advantageous to 
obtain several forage samples during simul- 
taneous digestion and intake studies. In these 
studies, rumen-fistulated animals should be 
used only for forage sampling, and a second 
group of intact animals should be used to esti- 
mate forage intake and digestibility. 
Indicator Comparisons Based on the 
Ratio Technique 
Various substances have been utilized in an 
attempt to predict digestibility by indirect 
methods; these substances include silica, meth- 
oxyl, lignin, chromogens, crude fiber, and pro- 
tein or nitrogen. Because of analytical difficul- 
ties, stratification in the gastrointestinal tract, 
variable natural occurrence in the feed, or par- 
tial absorption, some of these substances either 
have been eliminated from consideration as in- 
dicators or have not been investigated suffi- 
ciently to establish their potential value. The 
indicator most commonly used for estimating 
digestibility of range forages has been lignin; 
however chromogens and silica have been used. 
Cook and Harris (1951) compared chromo- 
gens and lignin as indicators for sheep grazing 
on winter desert range. The coefficient of var- 
iation averaged 8 to 12 percent for lignin and 
20 to 21 percent for chromogen with sheep 
grazing two types of shrubs. They concluded 
112 
that under these conditions chromogens were 
unreliable as indicators. These workers also re- 
ported that dry-matter digestibility of alfalfa 
hay is similarly estimated by the chromogen and 
lignin ratio techniques. Interactions between 
indicator and type of forage may be im- 
portant. Bohman et al. (1967) cite studies con- 
ducted at the University of Oregon in which 
low recovery of chromogen pigments was ob- 
tained with hand-fed steers. These studies are 
not in agreement with those of Connor et al. 
(1963), who found chromogen to be more suit- 
able than lignin for estimating dry-matter di- 
gestibility on range forage. 
Jefferies and Rice (1967) compared the lignin 
and chromogen ratio techniques for estimating 
digestibility of a native shortgrass range for 
steers. Digestibility estimates varied signifi- 
cantly between techniques and between sam- 
pling periods. Estimates by the two methods 
did not follow the same trend throughout the 
summer. The modified chromogen technique 
gave much higher digestibility estimates for 
dry matter. More studies are needed to clarify 
the validity of chromogens to estimate digest- 
ae for grazing livestock under range condi- 
ions. 
Van Dyne and Lofgreen (1964) evaluated 
lignin and silica as digestibility indicators of 
forage grazed by cattle and sheep on summer 
annual range. The three grazing periods varied 
in the relationship of the digestion coefficients 
calculated by the two indicators. Digestion 
coefficients calculated by silica ratio varied 
widely during the summer grazing periods. 
Their data suggest that silica can accumulate 
temporarily within the animal’s digestive tract, 
and may cause biased digestibility values when 
used as an inert indicator. 
Lignin Ratio Technique 
Three problems have been associated with 
the use of lignin as an indicator: (1) Develop- 
ment of a simplified, repeatable technique for 
measurement of the indicator in forage and 
fecal samples; (2) obtaining forage samples 
with lignin content representative of that con- 
sumed by the animal; and (3) constant, repeat- 
able recovery in the fecal material. 
Van Soest (1964) critically reviewed the 
procedures used for lignin analyses. He con- 
cluded that proteinaceous material, hemicellu- 
lose, and products of nonenzymatic browning 
reaction were artifacts generally present in the 
lignin fraction isolated by many of the common 
procedures. Van Soest (1963) showed that pro- 
teins and hemicellulose which were interfering 
could be effectively removed by treatment of 
the forage with an acid detergent solution. His 
studies indicated that the nonenzymatic brown- 
ing reaction could be largely prevented by 
maintaining the drying temperature below 50° 
