NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
238 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
and open on the margin of the oral opening. The duct of the larger gland appeared
to be a little wider than that of the other one.
The excretory system pattern consists of five pairs of flame cells in the body
and two in the tail. From the bilobed excretory bladder a collecting tube on each
side is seen to proceed forwards, and each tube forms a tangle on either side of the
ventral sucker. At the tangle there is a cross connection between the two main
tubes and this connection is anterior to the ventral sucker. Each tube then divides
into an anterior and posterior collecting tubules. The anterior tubule
divides into two branches, each ending in a flame cell. The posterior
tubule divides into two branches, one of which bifurcates soon after and
ends in two flame cells. The other branch bifurcates at the level of the excretory
bladder and one branchlet ends in a flame cell near the bladder and the other
branchlet passes into the tail stem where it divides into two divisions, each sur-
mounted by a flame cell. The flame cell formula is 2 [(2)+(2+1)+2].
The genital cells are arranged in the form of a mass of cells between the ven-
tral sucker and the bladder.
The tail consists of a stem and two long furcal rami. Inside the stem, there is
a caudal excretory channel originating from the bladder. The canal runs the whole
length of the stem, bifurcates into the furcal rami and each division opens in a
midfurcal pore. There are six pairs of caudal glands, arranged along the caudal
canal in the tail stem.
Identification.—This cercaria has the characters of holotsome cercariae and it is
placed in that group. In the following table its characters and those of the other
known holotsome cercariae, are noted for comparison.
Name of cercaria
C.
pygocydophora
Brown, 1931.
C. microphora Brown,
1926.
Cercaria F. 1. Harper,
1931.
G. of Strigea tarda
Harpor, 1931.
G. hirsula Miller, 1927
C. granula
Miller,
1927.
C. bombayensis No. 9,
Soparkar, 1921.
G. hurleyi, n. sp.
Eye
spots
. .
. .
. .
. .
. .
. .
. .
present
Setae
4 on each
side of tail.
. .
. .
. .
Only on tail
stem.
Do.
.
. .
4 on body, 6
on tail on
each side.
Penetra-
tion
glands
4
4
4
4
12
26
6
4
Alimentary
canal
Well deve-
loped.
Do.
.
Do.
.
Do. .
No intestinal
cæca.
Do.
.
Not deve-
loped.
Well deve-
loped.
Pairs of
caudal
glands
8
6
6
. .
6
6
..
6
Flame cell
formula
2[(2)+(2+2)+1]
2[(2)+(2)+1]
2[(2+1)+(2)+1]
2[(2+1)+(2)+2]
2[(2)+(2)+1]
2[(2)+(2)+1]
2(10+2)
2[(2)+(2+1)+2]
PLATE XX.
CERCARIA HURLEYI, N. Sp.
1. Side view.
2. Ventral view.
3. Photomicrograph of C. hurleyi
(Note the contracted body.)
CERCARIA HURLEYI, N. SP.
239
From the Table it is seen that the cercaria described in this paper resembles
the cercaria of Strigea tarda Streenstrup, 1842, described by Harper [1931], but the
former differs from the latter in the flame cell formula and also in possessing pale
yellow eye spots and fine setae on the body and the tail stem.
As regards longifuroate cercariae found in India, Soparkar [1921] has described
only one, Cercaria bombayensis No. 9. It differs from the one under report in
having 6 penetration glands, 10 pairs of flame cells in the body and two in the tail
and its alimentary canal is not developed. Sewell [1922] in his " Emarginate "
group has included such holotsome cercariae as possessing a few penetration cells, a
well developed alimentary canal, and a flame cell formula having five pairs in the
body and two pairs in the tail. He also said that members of that group are not
represented among the Indian forms. It would appear, therefore, that this is the
first of its kind in that group to be reported from India and since it differs from the
other holotsome cercariae described hitherto, it is proposed to name it Cercaria
hurleyi.
REFERENCES.
Brown, F. J. (1931) . . . .
„ (1926) . . . .
Harper, W. F. (1931) . . . .
Miller, H. M. Jr. (1927) . . . .
Sewell, R. B. Seymour (1929) . . . .
Soparkar, M. 13. (1921) . . . .
Some freshwater Larval Trematodes from Cheshire.
Parasitology, 23, 88-98.
British Freshwater Larval Trematodes with contribu-
tions to their life-histories. Parasitology, 18,
21-33.
On the structure and life-histories of British Fresh-
water Furcocercariae. Parasitology, 23, 310-324.
Furcocercous Larval Trematodes from San Juan
Island, Washington. Parasitology. 19, 61-83.
Cercariae Indicae. Ind. Jour. of Med. Res. 10,
Supplement.
Notes on some Furcocercous cercariac from Bombay
Ind. Jour. Med. Res. 9, 23-32.
STATISTICAL STUDIES IN RECORDS OF INDIAN DAIRY
CATTLE.
II*. RELIABILITY OF DIFFERENT LACTATION YIELDS AS MEASURES
OF A COW'S MILKING CAPABILITY.
BY
LALL CHAND SIKKA, B.Sc. (AGRI.)
Punjab Agricultural College, Lyallpur.
(Received for publication on 25th April 1933.)
(With 5 graphs.)
INTRODUCTION.
That Indian cattle are low yielders, and therefore uneconomical producers of
milk is widely recognised. The high milking qualities of the cross-breds, which make
them economical producers of milk are also generally admitted. Yet extensive
experiments in cross-breeding with many a foreign breed have shown that the per-
manent solution of the Indian Dairy Cattle problem lies with the pure-bred Indian
cattle rather than with the cross-breds. No doubt, the first cross has invariably
been highly successful, and the half-bred Indian-European cattle have always been
good and economical producers of milk, but later crosses with the imported sire or
double crosses, have admittedly been disappointing — at least those with the
Ayrshire breed.
Efforts at improving the milking qualities of pure Indian cattle by selective
breeding are, therefore, being made at several Government and Military Dairy
Farms, with a large measure of success. As a result of these efforts, we have got
herds of Indian cows that yield over 5,000 lbs. milk in a lactation on an average—a
level of production that compares quite favourably with that of good average herds
in the West, and which every cow-keeper in India would love to attain.
This remarkable improvement has been effected by patient work along two lines,(a)
maintaining herds of cattle under better systems of feeding and management; and (b)
practising selective breeding, i.e., through mating the best with the best, and the
ruthless culling of the poor yielder. It is not possible to give separately a quantita-
tive idea of the improvement brought about by each of these two factors, although
it will be agreed that the greater share of the improvement belongs to. the latter
* Part I of this paper appeared in Vol. I, part 2 of the Ind. Jour. Vety. Sc. and An. Hus.
( 240 )
LACTATION YIELDS AS MEASURES OF A COW'S MILKING CAPACITY.
241
factor, i.e., selective breeding coupled with rigid selection. Those who have studied
the evolution of these herds are aware of the large number of cattle culled in order
to bring these herds to their present level of milk production. To quote a single
instance, out of a total of 208 female calves born in the Agricultural College Dairy,
Lyallpur, from the time it was started, and excluding the 23 calves that are being
reared, only 78 were reared to maturity, and of those 36 culled (46 per cent.)
on account of poor production.
However, the age at which cows have been culled on account of poor produc-
tion has varied considerably at different dairy farms, and no uniform standard has
been followed. Thus, though at the College Dairy, Lyallpur, out of a total of
36 cows culled on account of poor performance 24, or 66 per cent. were culled
after milking for one lactation only, i.e., were selected very early, this task of
weeding out the inferior animals was considerably deferred at other places, such
as the Pusa Dairy Farm, where animals were usually tried for two or three lactations
generally before they were discarded. Evidently these two Dairy Farms have
assigned different values to the various lactation yields of a cow as a measure of her
milk-giving capacity, for though at Lyallpur the first lactation yield has been
reckoned as quite reliable, at Pusa it has been more often than not ignored.
It costs a huge sum, however, to rear a calf from birth to productive age.
It is, therefore, a waste of labour and capital to cull cows without giving them a
fair trial. It is equally unsound, however, to maintain poor producers in a herd
for any unnecessarily lengthy period. The question of determining the best age
for selection—age up to which a cow should be milked to know her true value as a
yielder —and of comparing the relative reliability of different lactation yields of a
cow as measures of her milking capability is, therefore, of some practical import-
ance. But so far as the author is aware, no results of any study of this nature
under Indian conditions have yet been reported. The present attempt has been
made to fill this gap.
MATERIAL.
The material for this study has been derived from the same sources as for the
previous one [Lall Chand Sikka, 1931], i.e., milk records of the Sahiwal cows of
Ferozepore and Pusa herds; though only those cows have been included which
have been kept for at least 4 lactations. 194 such cases were available, and their
records—776 in all—form the basis of this study.
To eliminate from these records the differences in yield as caused by varia-
tions in service period, and consequently to get more uniform data, all of them
were first standardised to 85 days service period basis, by using the correction
242 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
factors already reported (Lall Chand Sikka, 1931). Only records thus standardised
have been employed. Table I below gives the chief analytical constants for these
data both " raw " and " corrected ".
TABLE I.
Analytical Constants for the " raw " and " corrected " records.
Constants.
Mean
.
.
.
.
.
Standard deviation .
.
Co-efficient of variation . .
Skewness
....
Mode
.
...
" Raw " yield.
4141 ╤ 137
1537 ╤ 26
37.11 ╤ 1.06
+0.2442
3766
" Corrected " yield.
3941 ╤ 33
1378 ╤ 24
34.95 ╤ 0.98
+0.1568
3725
From the table of constants given above, it will be seen, that the mean of
" raw " yields is about 200 lbs. higher than the mean of " corrected " ones. This
is as it should be, since the mean service period for " uncorrected " yields is higher
than that for " corrected" ones, and since as reported earlier, a longer service
period increases the yield in a lactation and a shorter one depresses it. The skew-
ness is positive in both cases, with the result that the mode is less than the mean,
though the value of skewness of " corrected " records is definitely lower than that of
" raw " ones. The value of co-efficient of variation, though very high for both
classes of data, has decreased from 37.11 in " raw " data to 34.95 in " corrected "
data, as a result of standardisation, or by about 5.8 per cent. of its previous value.
This decrease is quite fair, especially when it is realised that we have standardised
the records only for the effect of service period, thus ignoring the effect of varia-
tions in age, dry period, and feeding and management etc. If the records had
been standardised for all these factors, then surely the value of the co-efficient of
variation would have still further decreased, and the data become more uniform.
Such a complete standardisation, however, is not possible as we have not evolved
the correction factors for variations in dry period yet, and it is not possible to
standardise records for variations in feeding and management. Furthermore,
for the study of the problem in question, it seems hardly right to use age-corrected
records, since it is the relative reliability of a cow's yield at different ages that we
are out to study.
METHODS.
Measure of Cow's milking ability.—The highest yield given by a cow in any
lactation when standardised to 85 days service period basis, has been used as a
measure of her milking capability. As has been pointed out before, records are
LACTATION YIELDS AS MEASURES OF A COW'S MILKING CAPACITY.
243
used for this study of the 194 cows, whose milk yield for the first 4 lactations at
least is known, though actually, for a very large number of the cows' included,
the number of records known has been more than 4. Where, therefore, the
number of records known has been larger than 4, the highest of these, though
where only 4 are known, the highest out of the four, has been taken to measure
cows' milk-giving capacity. This procedure is justified in view of the results
already reported regarding the variations of milk yield with age, wherein it was
shown, that Indian cows in general increase in their yield till their 3rd lactation,
maintain it in the 4th, and thence decline at an ever-increasing rate, and there-
fore, where we know the yields for the first four lactations of a cow, as in this case,
we generally know her maximum milk-yielding capacity.
It is recognised that this idea of talcing the corrected maximum lactation
yield, as a measure of a cow's milking capability, might not find favour with
practical breeders, who feel, and rightly so, that in a cow it is not the exceptionally
high yield in any one lactation that counts, but it is the yield over a number of
lactations that really matters, and consequently in selecting cows, we should take
average yield for life, rather than the yield for any one lactation. But as shown
below the mean yield of a cow for several lactations and her maximum lactation
yield are highly correlated, and thus mutually convertable. Besides the maximum
yield is less variable and hence more reliable than the mean yield for several
lactations. This latter point is well-illustrated in Table II which gives the main
analytical constants of the curves for the generally accepted measures of a cow's
milking capability, e.g., mean corrected yield for first three or four lactations, and
the measure used in this study " corrected " maximum lactation yield.
TABLE II.
Analytical constants of the curves for the mean " corrected" yields for the first 3 or 4
lactations and " corrected " maximum lactation yields.
Constants.
Mean . . .
Standard deviation
Co-efficient
of
variation.
Skewness . .
Mode . . .
Mean " corrected "
yield for first
3 lactations.
3877 ╤ 50
1029 ╤ 35
26.54 ╤ 0.97
+0.3803
3486
Mean " oorrected "
yield for first
4 lactations.
3941 ╤ 49
1012 ╤ 35
25.65 ╤ 0.93
+0.2989
3639
" Correoted "
maximum lactation
yield.
5123 ╤ 58
1196 ╤ 41
23.35 ╤ 0.84
+0.2259
4853
244 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
A study of the above Table shows that both skewness and co-efficient of
variation are lower in the case of maximum yield than in the mean first 3 or 4
lactations yield, which means that the maximum yield being less variable is a more
reliable measure of a cow's milking capability than her mean yield for several
lactations.
That the mean yield and maximum yield are definitely correlated is shown
in Graph I, in which each point in the dotted curve represents the mean
yield for first four lactations for the different cows, and that in the continuous
curve the maximum yield corresponding to this mean yield, the mean yields being
arranged in the ascending order according to their magnitude from left to right.
It will be noticed that except for a few exceptions here and there, the maxi-
mum yield goes on increasing regularly with the increase in mean yield.
From the correlation surface drawn for these 2 variables, the following cons-
tants were obtained:—
r
n
n 2 —r 2
+0.8763 ╤ .0112
0.8889 ╤ .0102
0.0222 ╤ .0144
As will be noted the value of r is very high. The value of n is slightly higher
than that of r, as these values generally are in case of linear regressions, and the
value of n 2 —r 2, compared with its probable error is very low and quite insignificant.
It is only 1.54 times its probable error, and therefore permits the use of a linear
equation to fit the data. This has, therefore, been done, and the following equation
obtained—
y = 1040 +1.0358 x
where y = maximum " corrected " lactation yield ;
x = mean "corrected" yield for first four
lactations.
The fit of the regression line to the actual means is shown in Graph II. It
will be noticed that the fit is good—the line passing through the observational
points remarkably well.
By using the equation given above, the maximum " corrected " yield of a cow
can easily be determined from her mean " corrected " yield for first 4 lactations.
Thus if a cow gives a mean " corrected " yield of 2,000 lbs. in her first 4 lactations,
according to this equation, she will give a maximum of 3,112 lbs. in any one lacta-
tion. The variation around this expected milk yield which would include 50 per
cent. of the cows of 2,000 lbs. mean " corrected " yield for 4 lactations may be found
from the relation of the standard deviation of such a record.
NUMBER OF COWS.
GRAPH I.—SHOWING THE RELATION OF MEAN 1ST. 4 LACTATIONS YIELD AND MAXIMUM YIELD.
GRAPH II.—SHOWING THE FIT OF REGRESSION LINE TO THE ACTUAL MEANS.
MEAN 1ST. 4 LACTATION YIELD.
LACTATION YIELDS AS MEASURES OF A COW'S MILKING CAPACITY
245
STANDARD DEVIATION = 1196/1-(.8763) 2
The probable error, .6745 × standard deviation, works out at 389 lbs., which
means that 50 per cent. of the cows with 2,000 lbs. mean " corrected " yield for
1st 4 lactations, would be expected to have a maximum yield between 3,112 ╤ 389,
or 2,723 to 3,501 lbs.
Evidently the best method of study of the problem indicated above is the
method of correlation, which is here followed. As in the previous publication,
probable error rather than the standard error has been employed to gauge the
significance of a difference. A difference of less than 4 times the probable error has
been considered as having arisen from fluctuations of random sampling.
RESULTS.
Table III gives the values of correlation co-efficients obtained for the variables
maximum " corrected " yield and milk yield with different successive lactations for
our data, though for the sake of comparison with our values those got by Gavin
with British Holsteins and Dairy Shorthorns [1913] for r between the " Revised
Maxima " with successive calves and maximum " Revised Maxima ", and by Tuff
with Norwegian red polled breed [1928] for r between the I and II calf yield and
the average milk yield by the adult animal are also given:—
TABLE III.
Value of correlation co-efficient.
Lactation.
I
II
III
IV
Present data.
+.5026 ╤.0362
+.6642.╤.0271
+.6666╤.0269
+.7745 ╤.0194
Gavin's data.
+ .394 ╤.031
+.452 ╤ .030
+.506 ╤.028
+.605 ╤.024
Tuff's data.
+ .298╤.136
+ .471╤.121
....
....
A study of Table III shows that the values of r with our data are definitely
higher than those given by Gavin or Tuff for their data ; furthermore, that the
value of r goes on increasing with successive lactation yields. For instance, for our
data, the value of r in the case of first lactation yield is + .5026 ╤.0362, though
in second it is +.6642 ╤ .0271—a difference of + .1616 ╤ .0452, which is very
nearly significant. There is not much difference in the value of r for II and III
calf yields, the value for the III calf yield being + .6666 ╤.0269, though the
value of r with the 4th calf is the highest, + .7745 ╤.0194, its difference from
246 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, III.
the r for the III calf being +.1079 ╤.0331. This means that as measures of a
cow's milking ability, later lactations are more reliable than the earlier ones.
First lactation yield, in fact, is hardly worth much, since, if this be used as the
measure, one will be out in almost about 50 per cent. cases. Though, none of.
the later lactations even is very reliable, but they are all better than the first.
The above table giving the values of correlation co-efficients between the
successive lactation yields and the maximum yield, however, does not present
the real gain in accuracy secured in judging the milking capability of a cow, when
she is kept for a period longer than one lactation. It only gives the values of r
for individual successive lactation yields with maximum and does not take account
of the fact, that when a cow is kept for more than one lactation, we know not
only her yield for each successive lactation separately, but also her mean yield
over several lactations as well. This mean yield is generally a much more reliable
guide of a cow's milking capability than any one lactation yield alone. To
illustrate this point Table IV is presented which gives the values of r for the mean
" corrected" yield of 2, 3 or 4 lactations and maximum yield for the data
under study.
TABLE IV.
Correlation of mean " corrected " yield, of 2, 3, or 4 lactations and maximum yield.
Lactation.
Moan 1st and 2nd . . .
„ 1st, 2nd, and 3rd . .
„ 1st, 2nd 3rd and 4th .
r.
+.72╤.0233
+.8033╤.0174
+.8763╤.0112
n.
.7409 ╤.02184
.8284 ╤.01519
.8889 ╤.0102
n 2 —r 2
.03053╤.01693
.04095╤.01960
.0222╤.0144
If the values of r as given in Table IV be compared with those given in Table
III, it will be seen that they have all increased in their value considerably. For
instance, the value of r for the mean first and second calf yield, is higher than that
got with any of the 1st 3 calf yields separately, and that for the mean 1st, 2nd and
3rd calf yields higher than that got with any of the 1st 4 calf yields separately,
though the value for mean 1st, 2nd, 3rd and 4th calf yields is the highest of all.
This means that the mean 1st 2 calves yield is more reliable as a measure of a cow's
milking capability than any of the 1st 3 calves yield separately, and mean 1st 3
calves yeild more reliable than any of her 1st 4 calves yield separately. The values
of n and n 2 -r 2 all show that all the regressions are linear, and therefore that linear
regression lines can be fitted to the data. The fit of one of the regression lines—
LACTATION YIELDS AS MEASURES OF A COW'S MILKING CAPACITY
247
maximum yield and mean 1st to 4th calf yield—has already been shown in Graph II,
which, as will be seen, is quite satisfactory.
That individual lactation yields are less reliable than the mean of 2 or more
lactation yields is generally accepted. Gowen [1920], for instance, got the same
results, and therefore while studying the subject of inheritance in crosses of Dairy
and beef-breeds of cattle [1920], used the mean corrected yield for several lactations
as a measure of cow's milking capacity. Gavin [1913] got a value of +.526╤.028
for r between the mean 1st 2 lactations " Revised Maxima" and maximum
"Revised Maxima", against that of +.394╤.031 for r between 1st calf "Revised
Maxima" and maximum "Revised Maxima" and +.452╤.030 for r between
2nd calf " Revised Maxima " and maximum " Revised Maxima ". Tuff [1928] got
a value of r=+.488╤.118 for the variables average 1st 2 calves' yields and average
milk yield by the adult animal, though he got a value of only +.298╤.136 for r
between 1st calf and average yield, and +.471╤.121 for r between 2nd calf and
average yield. Roberts [1928] found that a high yield in one lactation depresses
yield in the successive lactation, so that the average of 2 or more lactation yields is
always more reliable than individual lactation yields.
The reason why individual lactation yields are less reliable as measures of a
cow's milking ability, lies in their much greater variability, as compared with that
of mean yields for 2 or more lactations. Table V is presented to illustrate this point,
though to compare the values of co-efficient of variation for our data with those got
by other workers Table VI is also given.
TABLE V.
Constant.
Mean
Standard deviation . .
Co-efficient of variation . .
1st calf
yield.
3,726╤ 61
1,265╤43
33.95
╤1.29
2nd calf
yield.
3,874╤67
1,380╤47
35.62
╤ 1.37
3rd calf
yield.
4.027╤67
1,373 ╤ 47
34.09
╤1.30
4th calf
yield.
4.136╤70
1,451 ╤ 50
35.08
╤1.34
Mean 1st
2 yields.
3,802╤52
1.078╤35
28.35
╤1.04
Mean 1st
3 yields.
3,870╤50
1,029╤35
26.54
╤0.97
It will be seen from Table V that the values of co-efficient of variation for the
1st four lactation yields are all nearly equal, and definitely higher than those of
mean 1st 2 or mean 1st 3 lactation yields. A further comparison of these values
with those given in Table VI shows that they are all very high. They all range
between 33—35, though those of other workers approximate about 25 per cent. It
D