A M E T H O D FOR P R E S E R V I N G W E T FECES W I T H O U T
N I T R O G E N OR E N E R G Y LOSS
W. C. JACOBSON,E. A. KANE AND W. P. FLATT
Dairy Cattle Research Branch, ARS, USDA, Beltsville, Md.
investigators (Colovos et al., 1957; Cuthbertson and TurnV ARIOUS
bull, 1934; French, 1930; Gallup and Hobbs, 1944; Kleiber et al.,
1936) have reported losses of nitrogen when feces were dried. In order to
prevent these losses, it is a common practice in many laboratories to
determine nitrogen on the fresh wet feces. A number of studies have also
been made to determine if treating the feces prior to drying may reduce
nitrogen loss. Gallup and Hobbs (1944) found that the addition of 25
ml. of 20% acid alcohol reduced the loss of nitrogen but that this treatment interfered with the subsequent determination of fat and crude
fiber. French (1930) observed that copper sulphate, formaldehyde, or
zinc sulphate reduced the loss of nitrogen from a mixture of feces and
urine to a negligible amount. To prevent loss of nitrogen, Peters and
Van Slyke (1932) proposed that an aliquot of the daily production of
feces be added to sulphuric acid. At the end of the digestion trial period,
nitrogen could be determined on this slurry. This method has the disadvantages of requiring daily dry matter determinations to determine
the amount of dry feces in the sulphuric acid, and the sampling is difficult. Feces from cattle being fed high roughage rations contain undigested
stems of hay which makes representative sampling difficult.
Freezing and refrigeration of daily aliquots of feces with or without
the addition of a preservative such as thymol or toluene have also been
used as methods of storing samples until the end of the collection
period for compositing. This may leave both the bacteria and the
enzmyes in an active state and result in losses when the feces are thawed
and dried.
The extent of these losses may depend upon the drying conditions.
Raymond et al. (1953) has reported losses in dry matter in feces when
low temperatures and an inefficient oven were used to dry the fecal
material. Colovos et al. (1957) demonstrated that there was an appreciable loss of energy when feces were dried at 65 ~ C. for 48 hours.
Nitrogen determinations have been conducted on the fresh daily fecal
samples in this laboratory. This practice requires the time of a laboratory
technician to analyze these samples each day during the collection period.
The following experiment was undertaken to develop a procedure for
storing wet feces without alteration in composition or loss of nitrogen or
energy. Samples could then be composited and analyzed at the end of the
collection period. Thus the number of analyses required would be reduced
and the work load shifted to a more desirable time.
650
PRESERVING WET FECES
651
Experimental Procedure
This experiment was conducted in two phases. In the first phase
samples of feces were canned, stored, and later analyzed for nitrogen,
dry matter, ash, crude fiber, and ether extract. In the second phase the
samples were analyzed for gross energy and dry matter. These values
were compared with analyses run on fresh samples to determine the
effectiveness of canning in the prevention of losses of the various components.
The fecal samples used in the first phase of the experiment were obtained
from six cows maintained on an alfalfa hay-grain ration. Grain-hay ratios
varied from 1:1 to 1:10. Grab samples were taken at 2 p.m. and between
5 a.m. and 6 a.m., the afternoon samples being stored in a refrigerator
at O ~ until the next morning. The two defecations were then mixed
and samples taken for each individual cow. Kjeldahl nitrogen was run
in triplicate on the fresh materials. Duplicate 400-gin. samples from
each cow were dried in a large forced-air dryer at 80 ~ C. At the end of the
5-day collection period the daily samples were composited for each
animal and the proximate analyses of these samples were used as the
controls.
At the same time the above samples were taken, duplicate 400-gin.
samples of fresh feces were also canned. The process involved weighing
the feces into No. 2 R-enamel lined tin cans, placing the cans in a boiling
water bath for 5 minutes to expel the air from the feces, sealing with a
household automatic can sealer and autoclaving for one hour at 10 lb.
pressure. They were then cooled and stored at room temperature until
the end of the 5-day collection period, when they were opened, composited
for each cow and thoroughly mixed with a household electric mixer.
Nitrogen was determined on the wet feces and a 400-gin. sample was
dried in the sample dryer at 80 ~ C. This material was ground in a Wiley
mill, 1 ram. mesh, and analyzed for ash, crude fiber, and fat for comparison with the control samples.
In the second phase of the experiment fecal samples were collected
once daily from three dry Jersey cows which were on a conventional total
collection digestion trial involving a 3 X 3 Latin square design. The
ration consisted of three lots of orchardgrass hay and each collection
period was for 5 consecutive days. Urine and feces were separated by
means of a rotating belt device.
Samples were taken from each day's fecal collection of each cow and
treated in the following ways: (a) Analyzed immediately, (b) canned
and autoclaved. The feces were canned immediately and were stored for
varying periods of time up to 6 months at room temperature until opened
for analysis. Gross energy determinations were made with an oxygen
bomb calorimeter by a modification of the technique of Colovos et al.
(1957). Combustion of moist samples (1.5 to 2.5 gin., including fresh
652
jACOBSON, KANE AND FLAT'L"
and canned feces), was facilitated by the addition of 2 ml. of 95% ethanol
as a primer. The alcohol was maintained at 44-46 ~ F. to reduce evaporative loss during addition and mixing with the sample. Pyrex glass rods
3 cm. X 2 mm. were used to mix the feces and alcohol immediately
before the bomb was sealed. The gross energy of the alcohol (5,235
cal./ml.) was subtracted from the total gross energy value to obtain the
caloric value of the feces. All values were calculated on a dry matter
basis for comparative purposes.
Results and Discussion
The results of the first phase are shown in table 1. Each value represents the average of four determinations. The protein content of the
canned feces agreed closely with the average of the daily protein deterTABLE 1. A COMPARISON OF T H E C O M P O S I T I O N OF T H E D R Y M A T T E R OF
C A N N E D FECES AND FECES H A N D L E D IN T H E USUAL M A N N E R
Ash
Crude fiber
Fat
Protein
Cow no.
Canned
Control
Canned
Control
Canned
Control
Canned
Control
287
638
697
698
831
1017
Ave.
14.83
16.14
14.07
14.13
14.20
16.94
15.05
14.38
15.47
14.15
14.08
14.'11
16.78
14.83
33_99
35.93
36.91
36.99
34.98
35.71
35.75
34.87
37.07
36.81
36.84
34.79
35.38
35.96
4.36
4.40
4.10
4.64
4.66
4.57
4.46
4.41
4.36
4.25
4.65
4.39
4.25
4.39
i4.54
13.69
13.66
13.37
14.78
14.03
14,01
14.19
13.13
13.96
13.36
14.76
13.94
13.89
minations. There was also close agreement in the other components of
the dry matter of the feces, and an analysis of variance of these data
revealed that there was no significant difference between canned and the
control feces. These results indicate that canning was an effective means
of storing feces for future analysis without the loss of nitrogen, ash, crude
fiber, or ether extract.
Table 2 summarizes the results of the second phase. The values for
period 1 have been omitted because of incomplete combustion of several
of the first samples resulting from failure to add enough alcohol and
insufficient mixing. No difficulties in combustion of moist samples were
encountered after the first week. The caloric value was 5063 _+ 133 cal./gm.
dry matter (DM) for fresh feces and 5090 • 96 cal./gin. DM for the
canned feces. A comparison of the percent dry matter of the canned and
fresh feces indicated that there was no change in dry matter due to
canning. The average percent dry matter of the fresh material was 14.82,
while the dry matter content of the canned feces was 14.83%. Thus
canning prevented any apparent loss of energy during storage.
Canning as a means of preservation and storage of feces for future
analysis offers a number of advantages. The number of analyses required
PRESERVING W E T FECES
653
may be reduced because the necessity of daily nitrogen and dry matter
determinations is eliminated by compositing the canned materials at
the end of the experiment. Dry matter digestibility studies by the ratio
technique involve analyses of indicators, and many of these analyses
may be conducted on wet feces. Samples may be stored for extended
periods of time at room temperature, thus making it possible to shift
the analytical work load to a more suitable time for the analyst. The
T A B L E 2. D R Y M A T T E R A N D GROSS E N E R G Y VALUES Ou BOVINE F E C E S
P R E P A R E D AND S T O R E D BY D I F F E R E N T M E T H O D S ~
Cow no.
Period
and
day no.
Percent dry matter
(Vacuum oven 100 ~C.)
Calories/gram
of dry matter
Fresh
Canned
Fresh
Canned
348
II--1
II--2
1I--3
II--4
II--5
12.51
14.27
13.94
14.20
15.62
12.66
14.19
13.93
14.29
15.67
5183
5260
5255
5152
5098
5049
5103
4901
4778
5096
681
II--1
II--2
II--3
II--4
II--5
14.78
15.06
14.74
14.64
14.89
14.70
15.04
14.72
14.73
15.05
5210
5179
5001
50,64
5121
4992
5193
4946
5048
5047
682
1I--1
II--2
II--3
II---4
II--5
12.83
14.29
14.45
13.96
14.02
12.85
14.28
14.41
14.04
14.04
5126
5236
4778
5059
5088
5246
5116
4822
4984
50'10
348
III--1
III--2
III--3
III--4
III--5
16.93
15.65
14.65
14.77
14.93
16.99
15.67
14.58
14.69
14.84
5411
500'1
5032
4795
5068
5234
5204
5058
50,96
5122
681
III--1
III--2
III--3
III~4
III--5
15.37
15.55
15.80
15.72
15.81
13.38
15.61
15.87
15.49
15.83
5286
50,58
4917
4751
5023
5062
5236
5265
5182
5146
682
III--1
III--2
III--3
III---4
III--5
15.04
14.99
15.08
15.62
14.58
15.06
15.13
15.16
15.40
14.65
5062
5047
4774
4837
50,09
5085
5129
5317
5317
5066
Average
St. Dev.
14.82
14.83
5063
133
50,90
96
a Each value is the average of two analyses.
654
JACOBSON, KANE AND FLATT
labor i n v o l v e d in c a n n i n g feces is small, a n d v a l u a b l e r e f r i g e r a t o r and
freezer space is spared.
Summary
A m e t h o d of p r e s e r v i n g w e t feces w i t h o u t loss of n i t r o g e n or gross
e n e r g y has been described. Samples of b o v i n e feces were canned, stored
at r o o m t e m p e r a t u r e and a n a l y z e d for gross energy, nitrogen, ash, crude
fiber, ether e x t r a c t and d r y m a t t e r . T h e r e was no significant difference
b e t w e e n these values and those o b t a i n e d w h e n samples of the s a m e feces
were a n a l y z e d in the c o n v e n t i o n a l way. C a n n i n g of feces p r o v e d to be an
efficient, simple m e a n s of p r e s e r v i n g fecal samples.
Literature
Cited
Colovos, N. F., H. A. Keener and H. A. Davis. 1957. Errors in drying silage and feces
for protein and energy determinations. Improved procedures. J. Dairy Sci. 40:173.
Cuthbertson, D. P. and A. K. Turnbull. 1934. Note on the loss of nitrogen and sulphur
on drying feces. Biochem. J. 28:837.
French, R. B. 1930. The use of preservatives to prevent loss of nitrogen from cow
excreta during the day of collection. J. Agr. Res. 41:503.
Gallup, W. D. and C. S. Hobbs. 1944. The desiccatioa and analysis of feces in
digestion experiments with steers. J. Animal Sci. 3:326.
Kleiber, M., R. W. Caldwell and H. Johnson. 1936. Losses of N and C in drying feces
of cattle. Proc. Soc. Exp. Biol. Med. 34:128.
Peters, J. P. and D. D. Van Slyke. 1932. Quantitative Clinical Chemistry Methods.
Vol. II., p. 78, Williams and Wilkins Company, Baltimore, Md.
Raymond, W. F., C. E. Harris and V. G. Harker. 1953. Studies on the digestibility
of herbage. J. British Grassland Soc. 8:301.