222
Studies on the Determination of Digestibility Coefficients
TABLE I
Experiment III of 1941
Animal D 6
Days
1st . . .
2nd . . .
3rd . . .
4th . . .
5th . . .
6th . . .
7th . . .
8th . . .
9th . . .
10th . . .
11th . . .
12th . . .
13th . . .
14th . . .
15th . . .
Distribution of cake
Factor used
per lb. of live
weight
X
1.232
1.012
1.078
1.265
1.045
1.100
0.990
1.210
0.880
1.276
0.968
1.056
1.188
1.034
1.166
Live weight
lb.
Y
854
854
854
854
854
854
854
854
854
854
854
854
854
854
854
Air dry
cake fed
(gm.)
XY
1052
864
920
1080
892
939
845
1032
751
1089
826
901
1014
883
995
Data used in regression equation.
Straw
nitrogen*
(gm)
R
38.049
42.556
36.181
40.488
33.748
40.304
38.961
39.386
39.677
38.266
35.672
41.768
39.855
42.363
36.825
Cake
nitrogen*
(gm)
C
66.109
55.004
58.421
58.256
61.646
59.904
53.484
66.886
48.674
71.604
53.693
57.112
65.889
56.984
64.574
Digested
nitrogen
(gm)
D
63.824
54.182
55.294
55.143
54.788
60.150
49.434
62.796
46.360
63.115
47.841
51.360
66.885
51.947
58.065
* These values have been obtained from chemical analyses, and, although theoretically they should bear a direct
relation with the corresponding amount of cake, some variation is implicit, as dry weights and air dry weights of cake
from day to day did not vary on a constant proportion. A slight variation is also inherent between the analytical
composition of different days' samples.
The amount of air dry cake fed to the ani-
mals from day to day was worked out by multi-
plying the factor X (each day's respective fac-
tor) with the live weight X. The values thus
obtained have been set up in column four un-
der XY. The corresponding values of cake ni-
trogen as ingested from day to day have been
obtained from the individual analysis of each
day, and have been represented in column six
under C. These together with straw nitrogen
R and digested nitrogen D form the data final-
ly used for regression equation.
The results work out as follows:
a= 0.3318 ± 0.0702
b= 0.8713 ± 0.17l9
The co-efficients of correlation between the con-
secutive day's observation as found by Dr P.V.
Sukhatme were as follows:
Straw nitrogen . .
Cake nitrogen . .
Digestible nitrogen . .
0.40
0.76
0.76
The last two are significant at 1 p.c. level of
probability and suggest that these method of
using individual days' values in place of mean
of 10 or more days is not without a defect.
However, so far as the digestibility values are
concerned the values of a and b, as obtained,
here show a reasonable order of agreement with
the values obtained by the other method. The
statistical order of accuracy has not been as
satisfactory. This appears to be associated
with some complexities inseparable with the
basic data.
The animals do not work with mathematical
precision, and while the variation to this may
be a peculiarity inherent with individual ani-
mals, the main difficulty lies in respect to the
apportionment of the real amount actually fal-
ling to the corresponding shares of feeds and
faeces. There is at present no satisfactory
means by which a correct differentiation of these
can be made.
Possibly a solution of it can be found in
increasing the number of collecting days and
then working out on the basis of a certain speci-
fied standard as to what should be the minimum
number of days compatible with such a stand-
ard of statistical accuracy.
It is also necessary to state here that much
remains to be done to bring the method to con-
form to such a strict standard. But, even
if it only indicates a partial approximation
to it (as in the present case), it will be a
definite improvement over the prevailing
"method of elimination" in which altogether
assumed values have to be used which do not
permit of any form of statistical examination.
Besides, no other method contemplates the
assessment from the performance of single
individual animal from a single course of trial.