NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
300 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
In Table II the actual net energy obtained during the periods of tests and the
required net energy (column 7) have both been shown. In calculating the
latter, Warths' figure [1926] of 6 therms per 1,000 lbs. live weight has been assumed.
On this basis D 7 should have received about 2.9 to 3.1 therms per day (Column 7),
but instead it had only 1.64 therms during the first test, which came down to 0.87
therms during the 2nd test. In the case of D 8 its net energy dwindled down to
0.4 therms (during the 2nd test) or less than one-seventh of the actual requirement.
All these had their reflex in the total fall of live-weights (Column 10, Table II, also
Graph I). In the case of R 1 and R 2 the difference is only in degree, otherwise the
tendency of progressive decline has been working in all. The nitrogen balance too
has been equally characteristic of the grave nature of the deficiency in supply ; and
it will be noted that the longer the experiments continued, the greater was the
rate of daily loss of live-weight (Table III, Columns 7 and 8). The fall in live-
weights is also shown in chart I.
DETERMINATION OF DIGESTIBILITY CO-EFFICIENTS
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302 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
TABLE III.
Nitrogen balance per day.
Date
1
19th to 28th
May 1932.
18th to 27th
July 1932.
12th to 21st
June 1932.
18th to 27th
July 1932.
10th to 19th
August 1932.
10th to 19th
August 1932
Animal
No.
2
D 7
D 7
D 8
D 8
R 1
R 2
In paddy
straw
ingested
3
gm.
14.271
11.649
11.915
10.423
12.924
13.181
Voided
in
faeces
4
gm.
13.434
15.533
12.358
14.162
13.857
14.197
Digested
5
gm.
+0.837
—3.884
—0.443
—3.739
—0.933
—1.016
Voided
in
urine
6
gm.
7.040
5.706
5.861
4.536
5.444
5.150
Balance
7
gm.
—6.203
—9.590
—6.304
—8.275
—6.377
—6.166
Loss or gain
in Live
weights per
day
8
lbs.
—0.9
—2.7
—1.0
—2.3
—1.0
—0.7
The Need of Balanced Ration. In such circumstance the addition of a concentrate
becomes a necessity in order that the experiment can be conducted under more
normal conditions where the animals could have at least a balanced ration. But
with a mixed ration (here one roughage and one concentrate) the necessity arises
to assume that the digestibility of one of the feeds is known and constant, so that
by corresponding elemination we may calculate the digestibility of the other. Since
however such digestibility figures for India are not available, we had to rely on
" known " published data of elsewhere (European or American) and thereby, making
the corresponding deduction, assign the digestibilities of the roughage.
EXPERIMENTAL SCHEME.
Our investigation naturally included this part of the trial (viz., calculation by
assumed values) and in order to combine in the same the other objectives now
DETERMINATION OF DIGESTIBILITY CO-EFFICIENTS
303
leading to this paper, a fairly elaborate scheme was set up, in which it was ensured
that the normal condition of the animals was maintained. This will be seen from
the nitrogen balance and live weight figures, etc. (Appendices I and II). Six
animals were divided into three groups, each group receiving in turn 1 lb., 2 lbs. and
3 lbs. linseed cake as concentrate with paddy straw ad lib as roughage. The animals
were so chosen that at the time of starting the experiment the total live weight
under each group was more or less the same. Further sufficient interval was
provided between one test and another in order to eliminate as far as possible the
residual effect of the previous feed. Sufficient quantities of straw and cake from
the same source were stored in advance to ensure a uniform quality of feed during
the entire period of the trial.
The following represents the design of the scheme :—
1st Test
1 lb.
D 3
cake
D 6
2 lb.
D 1
cake
D 2
3 lb.
D 7
cake
D 8
2nd Test
l lb.
D 7
cake
D 8
2 lb.
D 3
cake
D 6
3 1b.
D 1
cake
D 2
3rd Test
1 lb.
D 1
cake
D 2
2 1b.
D 7
cake
D 8
3 1b.
D 3
cake
D 6
The whole arrangement was on a restricted randomised basis distributed in
a cyclic order whereby all the animals were in turn under 1 lb., 2 lb. and 3 lb.
combinations. This provided on one side, the same kind and quality of both
roughage and concentrate and on the other, reduced the chances of error to a
minimum whether with respect to the animals or their feeds.
304 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
As will be evident from the above, the design of the experiment provided (in
three cycles) 18 individual tests, six with 1 lb., six with 2 lb. and six with 3 lb. cake.
It was felt however that the extension of the experiment for another complete cycle
of 18 tests would have produced a more satisfactory material for computation but
pressure of work and limitation of staff did not permit it.
The objects of the scheme were mainly three-fold:—
1. The estimation of digestibility by the " method of elimination", i.e., by
applying the assumed values of one of the feeds, to work out the
digestibility of the other.
2. The direct estimation of digestibility by the graphical method.
3. The direct estimation of digestibility on the basis of multiple regression
equations.
METHOD OF ELIMINATION.
For this purpose the assumed values were used from Henry and Morrisons'
" Feeds and Feeding " [1928].
As already stated this procedure implies the carrying out of the experiment by
the addition of a concentrate whose digestibilities are supposed to be ''known".
With the 18 individual trials, six with 1 lb., six with 2 lb. and six with 3 lb. cake,
and working out by difference the digestibilities of the paddy straw, we obtained 18
figures for each component which varied in the case of dry matter from 38 to 49 per
cent.; for ether extract from 35 to 69 per cent.; for crude protein from a positive
figure of 11 per cent. to a negative value of 13 per cent. In order therefore to
reduce the variations to a minimum, each set of 1 lb., 2 lb. and 3 lb. combinations
was worked out into its respective mean. The figures are set forth in the following
table.
TABLE IV.
Digestibilities of paddy straw worked out by the aid of Henry and Morrison's
standards for cake.
—
Mean of 1 lb. group . .
Mean of 2 lb. group . .
Mean of 3 lb. group . .
Dry matter
44.28
42.05
41.83
Crude
protein
+5.91
—1.27
—0.91
Ether
extract
48.60
53.24
59.37
Crude fibre
60.69
58.33
58.25
Nitrogen
free extract
45.29
42.15
42.69
DETERMINATION OF DIGESTIBILITY CO-EFFICIENTS
305
The most noteworthy points about these figures are the values of the protein
on one side and the ether extract on the other. When the amount of concentrate
was least, viz., 1 lb., the protein digestibility of paddy straw worked out at a higher
and positive figure, viz., 5.91 per cent., whereas with increased amounts of cake the
figures were not only lower but definitely negative. This is suggestive of the fact
that a higher value was assigned to the share of cake, leaving a low or negative value
in favour of paddy straw. In the case of the ether extract the position was re-
versed. With increasing doses of cake the digestibility has definitely increased,
viz., 48.6 per cent., 53.24 per cent. and 59.37 per cent. in the 1 lb., 2 lb. and 3 lb.
groups respectively. Or in other words a lower value in the case of ether extract
was assigned for linseed cake, thereby leaving a higher margin in favour of paddy
straw. That this was probably the most likely cause is borne out by the figures
of cake digestibilities obtained by the graphical method as well as by multiple
regression equations.
In the following table the results obtained by all the
methods are given.
TABLE V.
Digestibility of linseed cake.
—
Dry matter
Crude protein
Ether extract
........
Crude fibre
Nitrogen free extract
......
Henry
and
Morrison
79
89
89
57
78
Graphical
method
70.10
84.75
96.36
27.29
67.30
Multiple
regression
equation
65.15
84.11
95.60
7.71*
61.34
It will be noted that whether according to the worked-out figures of paddy
straw (Table IV) or on a comparison with the figures by the new methods (Table V)
the assumed cake digestibility figures of Henry and Morrison appear definitely
higher for all the components except that of ether extract in which case it is consi-
derably lower. These have been correspondingly reflected in a progressive rise
and fall in almost all the figures of paddy straw under the 3 sets of 1 lb., 2 lb. and
3 lb. combinations (Table IV), the greatest difference occurring in the cases of ether
extract and crude protein, the latter giving also negative values. Such differences
with protein in particular seem to have also been obtained by Warth and Gossip
[ 1928 ] and Warth [ 1923 ] as are shown in the following table.
* This is the only value which has not been found satisfactory. The cause of it has been discussed
later.
306 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
TABLE VI.
Nitrogen digested from paddy straw (Experiment at Karnal and Pusa)
(Original Tables XIV and V).
1
Nitrogen in ration
....
Nitrogen in faeces
....
Nitrogen digested
....
Nitrogen digested from concentrate .
Nitrogen digested from straw ..
Karnal
(Warth and Gossip)
Ration 1
2
45.88
19.30
26.58
25.77
+0.81
Ration 2
3
59.13
21.50
37.63
38.08
—0.45
Ration 3
4
72.38
23.50
48.88
50.39
—1.51
Pusa
(Warth)
Kailash
5
—3.01*
Mahdeva
6
—1.78*
It will thus be seen that when the computation is made on the basis of assumed
digestibilities for concentrates, the amount falling to the share of the roughage is
evidently affected to a definite extent according as the values assigned for concen-
trate are more or less than the actual. In the progressive doses of concentrate as
tried by ourselves on a more comprehensive scale, this rise and fall has behaved
with a remarkable consistency indicating definitely which of the assigned values
of the components of concentrate were above or below the actual amount.
It is however necessary to emphasise here the doubtful utility of the present
unavoidable application of outside standards. In fact the disadvantages of the
use of such data have also been noticed by the continental workers as well.
Wood [1914] of Cambridge University has shown that they were too high
for an ox fed on a heavy fattening ration and Eckles [ 1 ] of Missouri Station has
found such values too low when applied to the dairy cow. Our work also point
to the unsuitability of their general application, but the paucity of local data left
us little alternative ; and in consequence the digestibilities of many of our feeds
have of necessity to be worked out with these assumed figures obtained under
conditions necessarily different from ours. But the variability in the values all
the more emphasises the inexact nature of working by " the method of elimina-
tion". Any attempt therefore to evolve a more suitable method would solve a
long-felt difficulty even if it be only a partial improvement over the prevailing one.
* Warth's results contain a number of such negative values but only two are quoted here.
DETERMINATION OF DIGESTIBILITY CO-EFFICIENTS
307
THE DIRECT ESTIMATION OF DIGESTIBILITIES OF BOTH STRAW AND CAKE BY THE
GRAPHICAL METHOD.
As already stated, the unsatisfactory results obtained by the existing methods
have led to its trial.
It is necessary to state here that this method was apparently given some trial
by Warth [ 1929 ] on the aspect of protein digestion of concentrates. It has
however been carried out in the present case on a rather more comprehensive scale
including all the individual components comprising the roughage and concen-
trate. A brief description of the method as here used is given in the following.
308 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
Let x axis represent the amounts of concentrate consumed and the ordinates
the total amounts consumed and digested on the same scale. The upper line stands
for total consumption and the lower line for total digestion (from both roughage
and concentrate). The lines are produced to meet the y axis and the points at which
they meet are carefully read. These have been shown in columns 2 and 3 of
Table VII. Obviously they represent the amounts consumed and digested from the
roughage (paddy straw) when no concentrate is supposed to be given. Their ratio
is shown in column (4) representing the digestibilities of the components of
roughage. Similarly the slope of the lower curve (column 5) stands for the
digestibility of the concentrate.
Each of the individual components, viz , dry matter, crude protein, ether
extract, etc., has thus been separately plotted out under 1 lb., 2 lb., and 3 lb.
combinations. These have been shown in separate graphs (Charts 2—7). In these
the mean under each group with its circle of error is also represented to indicate
the range of variation.*
* For accurate drawing the straight line of best fit can be obtained by least squares giving the
ordinates as well as the slopcs.
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310 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
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DETERMINATION OF DIGESTIBILITY CO-EFFICIENTS
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The values obtained from the graph drawn for each of the food components are
set forth in the following Table :—
TABLE VII.*
Components
1
Dry matter
....
Organic matter
....
Crude protein
....
Ether extract
....
Crude fibre
Nitrogen free extract ...
Ordinate at
x=o
(consumed) C
gems.
2
3,862
3,326
147
45
1,302
1,830
Ordinate at
x = o
(digested) D
3
1,751
1,687
13
19
803
845
Digestibility
of
roughage
D
C
4
.4507
.5073
.0873
.4316
.6165
.4617
Slope of the
curve
(Digestibility
of
concentrate)
5
.701
.7216
.8475
.9636
.2729
.6730
* The original data are reproduced in Appendix II.
It will be seen that the straight line in the graph has given a very close fit
to the observed values except in the case of crude fibre †. This evidently points
out that the interaction during the course of digestion is probably negligible and the
digestibility is more or less constant for the three sets of combinations. This
would suggest a fair order of reliability for the estimates of digestibility co-efficients.
THE DIRECT ESTIMATION OF DIGESTIBLITIES (OF STRAW AND CAKE) BY THE AID
OF MULTIPLE REGESSION EQUATIONS.
We have no direct way of ascertaining whether there is any or no interaction
taking place during the course of digestion of cake and straw. The same state-
† In the case of fibre the range of variation of the observed values and the deviations from the
straight line will be seen to be of the same order and hence the fit cannot be considered satisfactory.
316 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
ment holds good for the progressive doses of cake as used in our experiment. The
graphical method however suggests that within the range of 1 lb., 2 lb. and 3 lb.
combinations, the interaction at any rate would seem inappreciable. It may
therefore be neglected for the purpose of this experiment, and as a first approxi-
mation be assumed that the behaviour of cake and straw with respect to their
individual digestibilities is independent of each other and also constant. The
subsequent analysis of the results, as will be shown later, supports this assump-
tion within the limits of sampling errors in the case of the majority of the indivi-
dual components of both the feeds.
A brief description is given in the following.
In the case of the above experiment with 1 lb., 2 lb. and 3 lb. cake as con-
centrate and paddy straw ad lib as roughage there is a mixed ration of two un-
knowns—viz., cake and paddy straw.
If now a and b represent the digestible fractions of the component (here crude
protein) from straw and cake respectively, the linear relation is obtained as fol-
lows* :—
y=ax 1 +bx 2
(1)
y=Amount digested from straw and cake.
x 1 =Amount consumed from straw.
x 2 =Amount consumed from cake.
If the equation gives a good fit, it should reasonably follow that the hypothesis
holds good and that the values of a and b thus obtained represent the nearest
approach to the fractions digested from the respective share of X 1 and X 2 .
From the equations thus obtained, the expected values (y) of the amount digested
from the observed values of x 1 and x 2 can be calculated. As an illustration the
observed and expected values of one of the important constituents, viz., protein
nitrogen has been shown in Table VIII. For this the co-efficients of digestibility as
worked out are :—
Digestible crude protein in paddy straw.—9.90 per cent.
Digestible crude protein in linseed cake.—84.13 per cent.
The method of calculation is described in detail in Appendix IV.
* Since when x 1 =o and x 2 = o the amount digested is necessarily Zero, therefore no constant has
been added. From the observed values also the value of c is found to be negligible in all cases.
DETERMINATION OF DIGESTIBILITY CO-EFFICIENTS
317
TABLE VIII.
Crude protein (Total nitrogen).
Name
of
bullocks.
1 lb. {
2 lb. {
3 lb. {
1
D 1
D 2
D 3
D 6
D 7
D 8
D 1
D 2
D 3
D 6
D 7
D 8
D 1
D 2
D 3
D 6
D 7
D 8
Total
Amount digested
Calculated x 1 a x 2 b
2
18.88
18.91
20.13
20.14
19.87
19.79
37.90
37.75
37.62
37.74
35.07
35.20
55.48
55.41
51.77
51.73
55.27
55.35
663.41
Observed y
3
19.14
19.61
21.53
21.21
20.08
16.98
38.09
37.50
36.70
37.93
34.38
32.95
55.75
53.09
52.44
53.78
56.90
55.35
663.41
Difference between
calculated
and observed
4
—0.26
—0.70
—1.40
—1.07
—0.21
+2.81
—0.19
+0.25
+0.92
—0.19
+ 0.69
+2.25
—0.27
+2.32
—0.67
—2.05
—1.63
0.0
...
It will be seen from a reference to columns 2 and 3 (Table VIII), that the
assumption of the constant digestibilities of roughage and concentrate is clearly
borne out from the remarkable agreement of the observed and expected values of
the amounts digested.
318 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.
Applying the same procedure, all the other components, viz., dry matter,
organic matter, crude protein, ether extract, crude fibre and nitrogen free extract
have each been separately worked out. The value of a and b for each of them
are set forth in Table IX and the necessary statistical tests of significance have
been shown in Appendix V.
TABLE IX.*
Best values of a and b.
1
Dry matter
....
Organic matter ....
Crude protein
....
Ether extract
....
Crude fibre **....
Nitrogen free extract ...
Digestibilities of
paddy straw
(a)
By regression
equation
2
0.4556
0.510324
0.098985
0.4379
0.618935
0.463524
Graphical
method
3
0.4505
0.5073
0.0873
0.4316
0.6165
0.4617
Digestibilities of
linseed cake
(b)
By regression
equation
4
0.6515
0.670692
0.841132
0.9730
0.077092
0.613449
Graphical
method
5
0.7010
0.7216
0.8475
0.9636
0.2729
0.6730
* See also Appendix V.
** Vide remarks, page 305 foot note and also in discussion.
DISCUSSION.
It has been stated earlier that as a first requisite for reliable digestibility figures
the animals must be provided with more or less normal conditions and the feed must
be at least a balanced ration. In the tests initiated by the authors these provisions
were followed as far as possible. The critical examination that resulted with respect
to the three methods, shows that in computing the figures by what has been
termed " the method of elimination " the resulting values, worked out on the basis of
assumed standards, are definitely affected according as the assumed values are higher
or lower than the actual. The need for local data to replace these outside standards
has become insistent. These difficulties chiefly account for the subsequent attempt,
and the preliminary investigation appears to indicate that the working of data on the
basis of linear relations enables a direct calculation and warrants a greater degree of
DETERMINATION OF DIGESTIBILITY CO-EFFICIENTS
319
accuracy. The graphical method was thus brought in and as the next step, the
multiple regression equations followed as a natural corollary to it.
In order to get an idea of the nature of agreement obtained by this procedure
the case of crude protein already given as an illustration of the working out of these
methods might be taken up (Table 8, Columns 2 and 3). It will be seen that the
actually observed values of digestion (y) and the calculated or expected values
(x 1 +x 2 b) worked out from the value of a and b (obtained by the application of
regression equations) have recorded an unexpectedly remarkable coincidence of
agreement. The co-relation (Appendix V, Column 8) has been above 99 per
cent. and the observed ratio of variance has been much above the minimum
requirement of Fisher's 1 per cent. point of distribution. The observed and
expected values have also been plotted out (Chart 9) and it will be noted that
the variation has been negligible. For the results worked out by the graphical
method the reader is referred to Chart 4 (for protein) and Table IX. It will be seen
that by the graphical method the errors on mean (also of. Appendix III) have been
very small and the agreement between it and that of regression equations has been
reasonably close.
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