NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
268 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, III
TABLE II
Thousand parts by weight of parotid saliva contain
Saliva
Parotid saliva . . .
Water
991.5
Total
solids
8.5
Organic
matter
1.7
Inorganic
matter
6.8
The results of chemical analysis of the inorganic constituents are given in
the following table.
TABLE III
Thousand parts by weight of saliva contain
Saliva
Parotid gland . . .
Sodium
2.768
Magnesium
0.06
Potassium
In traces .
Sodium,
as chlo-
rides
0.098
Total chlorides, 0. 154 ; sulphates 0. 145 ; and phosphates, 3.590 were present
in 1,000 parts of saliva by weight.
Ptyalin is an amylolytic enzyme present in the saliva of man and in some
domesticated animals ; it is capable of converting starch into dextrin and mal-
tose.
Ellenberger states that both the parotid and sub-maxillary secretions of
horse and ox can convert starch into sugar. Smith [1890] says that in all domestic
animals the parotid saliva possesses the highest degree of amylolytic power. In
ruminants the diastatic action of saliva is about the same as that of the horses.
Schwarz and Steinmetzer [1924] say that the saliva of ox contains no amylase.
Palmer [1916] states that the amount of ptyalin present in the saliva of the ox
is insignificant.
From the review of the literature it is concluded that there is a difference
of opinion about the presence of ptyalin in the saliva of ruminants.
The presence of ptyalin in the parotid saliva of the buffalo was studied by
Evans' method, and it was observed that the starch was neither converted into
erythrodextrin nor into maltose when subjected to the action of the parotid saliva
from the buffalo.
SECRETION AND COMPOSITION OF PAROTID SALIVA IN BUFFALOES
269
Further experiments were conducted to determine whether the parotid saliva
of the buffalo contained a very small quantity of ptyalin, which may require a
longer time to exert its action on the starch. Both boiled and unboiled solutions
of starch were mixed with an equal quantity of saliva in two separate tubes and
allowed to remain at 38° C. for two hours. At the end of this period neither ery¬
throdextrin nor maltose could be detected in either of the tubes. The solutions
were allowed to remain at room temperature for 24 hours in presence of toluene
but the starch remained unchanged. The experiments were repeated several
times with identical results. It can reasonably be concluded from these experi-
ments that ptyalin is absent in the parotid saliva of the buffalo.
ACKNOWLEDGMENT
Thanks are due to Mr. G. S. Khan, B.Sc., Lecturer in Chemistry at the college,
for making the analysis of inorganic constituents of the saliva.
REFERENCES
Ellenberger (cited by F. Smith, 1921). A Manual of Veterinary Phys ology.
Pavlov, I. P. (1910). The work of the digestive glands, 85-87.
Palmer, C. C. (1916). Amer. Jour. Physiol. 41, 483.
Schwarz, C, and Steinmetzer, K. (1924). Ferment-forsch. 7, 229.
Smith, R. M. (1890). The Physiology of Domestic Animals, 293.
SELECTED ARTICLE
THE INHERITANCE OF PRODUCTIVITY IN FARM LIVE
STOCK*
1. MEAT
JOHN HAMMOND
(School of Agriculture, Cambridge)
(With Plates XIV—XIX and three text-figs.)
[Reprinted, from the Empire Journal of Experimental Agriculture, Vol. III, No. 9,
January 1935.]
Introduction.—Almost all the characters that are of any importance for
meat (such as weight-for-age and body-proportions) in our farm animals are
dependent for their full expression on environment and nutrition. We cannot ,
therefore, consider the genetic characters for meat-production without considering
the environment in which they are developed. In my opinion, most of these
characters have been developed purposely, and their development has been
planned and directed by man through selection in an environment that he has
created to produce them, whilst in only a very small minority of cases have they
arisen, by chance, from large mutations. The large mutations that occur in our
live stock are nearly all of the recessive type, and for the most part consist of
defects and abnormalities or fancy points (such as colour and horns) which are
of little commercial importance. They usually segregate out in simple ratios,
and it is an easy matter to breed for them by using Mendelian methods. On the
other hand, almost all the commercial qualities are ' blending' in inheritance:
there is no dominance, and in my opinion they have been produced by quite a
different method, that is, by the accumulation of small variations, which are conti-
nually appearing, and may be stimulated by the environment. In my opinion,
too, these characters exist in all degrees of ' fixity ' in the animal. In other words,
in terms of present-day explanations, I believe not only in the mutation of a gene
already formed, but also in the possibility of the evolution of a new gene by the
animal itself under the stimulation of the environment, and consequently of
varying degrees of ' fixity ' of characters under environmental change, according
to the state of evolution of the gene in question. Whilst the animal produces
the gene as a mechanism for putting the characters that it has evolved into its
inheritance, a mutation in the gene already fully formed gives a variation in the
animal that is of small importance in evolution, because it is at random and not
purposeful, as in the former case. Thus, I see the real evolution of commercial
. The five papers under this head were read to Section D (Zoology) of the British
Association for the Advancement of Science, Aberdeen, September 10, 1934.
( 270 )
272 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, III
they can be put in a series according to the rate and extent to which these propor-
tions are developed. A beef Shorthorn bull 14 months old is as well developed
in its proportions for meat as an adult Friesian bull 5½ years old, and the extent
to which it develops eventually is far in excess of anything found in the dairy
breeds. The directive influence of man's selection is seen in the way in which
stocks having a different origin—such as the Aberdeen-Angus and the Shorthorn—
approach one another in conformation for beef purposes (and Friesians and Dairy
Shorthorns for milk purposes), whilst stocks with a common origin—such as
the Shorthorn—have developed different types when bred for different purposes,
such as beef and milk (see Plate XVI).
Of quite another nature genetically, and in no way dependent on environ-
mental and nutritional conditions, is the ' Doppellender' calf, which is so much
valued for veal on the Continent (Fig. 4, Pl. XVII). It consists of a doubling of
the muscles of the loin and hind quarters, and has arisen as a mutation in
several Continental breeds of cattle, in which it is carried on in the heterozygous
condition, for the females are sterile. It is a simple recessive and forms no
blend in crossing as do the developmental characters. It cannot, therefore, be
used to improve other stocks in the same way that Aberdeen-Angus bulls are
used to introduce an improved conformation and better quality when mated to
coarse-boned and ill-proportioned cows.
The colour of the body-fat in cattle is a multiple-factor genetic
character; all shades of colour exist from a very pale yellow (which is
desired by the butcher) to a deep yellow (which is desired by the breeder of dairy
cattle). The expression of this character is dependent on the amount of the
xanthophyll pigments of plants in the food, and if these are absent the fat becomes
white, no matter what the genetic constitution is. In selecting for this character
the breeders of dairy cattle feed plenty of greenstuff and pick out those cows
which give the deepest yellow tint. Variability curves (by Whetham) for the
colour of the butter-fat in the different breeds of cattle at the London Dairy Show
are shown in the next figure (Fig. 5, p. 274). This is a case where a definite envi-
ronment of food-supply is necessary before selection can be made for the genetic
character concerned.
Sheep (mutton and lamb).—As with beef, the genetic characters for mutton
and lamb are all ' developmental' ones, and in Great Britain there exists a com-
plete range of types from those possessing early maturing qualities (that is, a quick
change in the proportions of the body), and suitable for killing as lamb, to those
with a slow change in proportions, which are more suited to mutton-production.
These characters are not firmly fixed, however, and may be modified in any one
breed by the methods of feeding and management adopted. During growth, the
tissues of the body develop in a definite order—bone, muscle, and then fat. The
proportional development of these tissues varies considerably in different breeds;
274 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, III
Fig. 5. (From Whetham—paper in preparation.)
Variability Curves of the Colour of Butter-fat in different Breeds of Cattle.—London
Dairy Show data (1923-32). Range of colour measured on a butter-fat colour scale.
1 = white, 10=dark yellow. The vertical lines show the mean values for the different
breeds.
THE INHERITANCE OF PRODUCTIVITY IN FARM LIVE STOCK
275
THICKNESS OF FAT OVER LOIN (C) 9 MONTHS
Fig. 7. (From Hirzel—paper in preparation.)
Measurements of Fat over the loin in different Breeds and Crosses of Sheep at Smith-
field Show.—For position of measurement see Fig. 6, Plate XVII. The measurements
are shown as — or + the optimum measurement (8 mm.) desired by the public, and
are breed averages over a number of years. Approximate age of carcasses—9 months.
develops last. The developmental meat characters of the animal are
genetically fixed only in relation to a certain environment. Conversely, if we
wish to develop a certain character in our stock, we must carry our selection for
that character in a suitable environment, if we are to be successful.
General conclusions.—Since the genetic characters concerned in meat-produc-
tion are so dependent for their expression on the environment, especially nutrition
(and are mostly of a developmental character), our best means of directive improve-
ment is selection (by progeny tests) in a suitable environment, that is, one which
276 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, III
stimulates the development of the character in question. The further develop-
ment of these commercial qualities in our animals depends, like the ' civilization
qualities' in man, on the creation of a better environment for the development
of the characters concerned.
Ind. Jour. Vety. Sci. & Anim. Hus., Vol. VI, Pt. III.
PLATE XIV.
FIG. 1. THE CHANGES IN THE PROPORTIONS OF THE
HORSE IN DEVELOPMENT AND DURING
EVOLUTION
In order to show the changes in proportions, all the photo-
graphs have been reproduced to the same cranium size (eye to ear
length). The changes in proportions during embryonic life parallel
those which have taken place during evolution.
Reading from left to right :
Top line : EVOLUTION—(a) Eohippus ; (b) Mesohippus ; (c) Mery¬
chippus ; (d) Equus (Arab).
Second line : DEVELOPMENT(Welsh Pony)—(e) 3 months ; (f) 5
months ; (g) 7 months ; (h) 10 months.
Third line : DEVELOPMENT (Welsh Pony)—(i) 11 months ; (j) 2
weeks after birth ; (k) 9 weeks after birth ; (l) adult.
Bottom line : EVOLUTION—(m) Light Horse (Thoroughbred—St.
Simon) ; (n) Heavy Horse (Suffolk—Wedgwood).
(From Hammond, 'Actes, 16 c Cong. Internal. d.'
Agric., Budapest,' 1934.)
Ind. Jour. Vety. Sci. & Anim. Hus., Vol. VI, Pt. III.
PLATE XV.
FIG. 2. CHANGES IN THE PROPORTIONS OF THE BODY IN
HEREFORD CATTLE
In order to show changes in body proportions, as distinct
from size, the photographs have all been reduced to the same height
at the shoulders, so that the proportions are shown in relation to
this measurement.
11.
12.
13.
14.
15.
Heifer—2 days old.
Steer—30 months old (reared
on low plane of nutrition).
Steer—11 months old (reared
on high plane of nutrition).
Steer—22 months old (reared
on high plane of nutrition).
Bull—adult—type existing
100 years ago.
1.
2.
3
4.
5.
Heifer—2 days old.
Bull—5 weeks old.
Bull—13 months old.
Bull—22 months old.
Bull—5 years old.
(From Hammond, 'Actes, 14 c Cong. Internal. d' Agric., Bukarest,' 1929)
Ind. Jour. Vety. Sci. & Anim. Hus., Vol. VI, Pt. III.
PLATE XVI.
FIG. 3. PROPORTIONS AND AGE CHANGES IN BULLS OF
DIFFERENT BREEDS
(a) 12 months
—
(b) 18 months
(c) 21
„
(d) 25
„
(e) 5½ years
(f)
(g)
(h)
(i)
(j)
12 months
13
„
16
„
22
„
—
4½ years
(k)
(l)
(m)
(n)
(o)
(p)
10
14
16
26
28
5½
months
„
„
„
„
years
—
—
(q) 19 months
(r) 31 „
(s) 5½ years
(Photographs all reduced to the same shoulder-height.)
Ind. Jour. Vety. Sci. & Anim. Hus., Vol. VI, Pt. III.
PLATE XVII.
FIG. 4.
CARCASS OF A 'DOPPELLENDER'
VEAL CALF
11 weeks old. Weight 367 lb.
(From Herter and Wilsdorf, 'Arbeit deut.
Landw.-Gesell.' ; H. 206, Berlin, 1912).
FIG. 6. LOINS OF MUTTON (cut at last rib)
To show where the fat-measurements given
in Fig. 7 were taken—at the narrowest part
over the 'eye' muscle. The three carcasses
illustrate :
Top : A carcass with too little fat and an
insufficient thickness of 'eye' muscle.
Middle: A carcass which has the propor-
tions of fat and muscle required by the
public.
Bottom : A carcass in which the fat is much
too thick.
Ind. Jour. Vety. Sci. & Anim. Hus., Vol. VI, Pt. III.
PLATE XVIII.
FIG. 8.
THE ANCON SHEEP
The shortened legs are a
recessive mutation and do
not give intermediates on
crossing with the long-legged
type, as occurs when a breed
with 'developed' short legs
(such as the Southdown) is
crossed with a long-legged
type.
(From Wriedt, 'Heredity in
Live Stock', London, 1930.)
FIG. 9. CHANGES MADE IN THE
POLAND-CHINA PIG WHEN
THE DEMAND FOR LARD
DECREASED
All the photographs have been
reduced to the same shoulder-height
to show changes in proportions as
distinct from size. The breed has
been changed by selection in the
direction of later maturity, i.e., with
more bone-and muscle-growth and
less fat. These successive changes
are the reverse of the changes which
occur as the pig grows up. This has
been attended with increase in
actual size.
(From Hammond, F. Roy. Agri.
Soc., 1932, 93.)
Ind. Jour. Vety. Sci. & Anim. Hus., Vol. VI, Pt. III.
PLATE XIX.
FIG. 10. CUTS THROUGH THE LEGS AND LOINS OF NEW ZEALAND
PORKERS OF DIFFERENT BREEDS AND CROSSES
Nos. 46, 67, and 68 : Large White × Tamworth ; carcass weight, 71, 65, 74 lb.
No. 52 ; Tamworth × Large White ; carcass weight, 72 lb.
No. 70 : Large White ; carcass weight, 70 lb.
No. 16 ; Berkshire ; carcass weight, 72 lb.
Note on the loins the thickness of the 'eye' muscle, the uniformity and
thinness of the fat over the 'eye' muscle, and the thickness and well-
developed lean meat of the 'streak'.
(From photographs taken for the Department of Sci and Ind. Research, Wellington,
New Zealand.)
THE INHERITANCE OF PRODUCTIVITY IN FARM
LIVE STOCK
II-MILK
A. D. BUCHANAN SMITH
(Institute of Animal Genetics, University of Edinburgh).
Can the science of genetics offer reasonable help to the live-stock producer ?
If so, then by what means ? In this paper it falls to me to deal with these two
questions from the point of view of milk-production in cattle.
Before the scientist can tackle any problems he must be able to weigh or
to measure that with which he is dealing. Both quantity and quality
must be assessed. Thus genetical experiment in respect of eggs and milk is much
easier than it is in the case of meat.
As Dr. Hammond has so clearly stated, it is essential to be able to discriminate
between the factors affecting the productivity of an animal that are due to environ-
ment, nutrition, management, disease, etc., from those factors that are genetic.
The difficulty of doing so is one of the rocks upon which the barque of the geneticist
is most likely to founder; and the task is further complicated because attempts to
correct for environmental and other variations are likely to mask a genetic factor.
For instance, Mackintosh [1] has recently shown that, where it is necessary, for
comparison, to correct the first-lactation-yield of dairy cattle, the correction factors
employed often work reasonably well, but that in the case of one group of cows
they were very far out.
Up till now, about 400 papers have been written dealing principally with
some aspect of the inheritance of milk-yield. Some useful information has been
obtained, but that source is now becoming exhausted, and I think that any future
information of scientific value regarding the inheritance of yield and quality of
milk will be obtained only by deliberate experimentation. By deliberate experi-
mentation I mean the control of environment and nutrition to the greatest possible
extent, so that, although the production of one generation takes place many years
after the production of that ancestral generation with which it is to be compared,
the comparison may be as straightforward as possible and with the minimum use
of correction factors.
The need for this has been recognized by Dr. Graves and those in charge of
the experiments conducted by the Bureau of Dairy Industry of the United States
Department of Agriculture, and Dr. Lush informs me that several of the State
agricultural experiment stations, such as Illinois and Nebraska, have now also
laid down similar experiments with dairy cattle. This principle forms the basis
( 277 )
278 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, III
of the experimental work that we are conducting with dairy cattle and pigs at
the experimental farms of the Institute of Animal Genetics. The method adopted
is to do our utmost to secure a uniform system of management and nutrition over
a long period of years. There is no ' deliberate' experimentation. Results are
being measured continuously. So far as I am aware, nowhere else is this principle
of holding environment, etc., reasonably constant being employed for dairy cattle.
Yet it is precisely the same principle as that employed, though not for genetic
purposes, by the most venerable of all agricultural research institutes. The
' classical ' fields at Rothamsted, where certain plots have been under the same
treatment for ninety years, form an excellent example of this method of passive
research.
Already, and without the results of this planned and yet passive research,
there is information of undoubted value, of which perhaps the most important
is that quantity of milk is transmitted to a great extent independently of quality
as measured by fat-yield. But many of the other results are still open to question.
The problems that are now being tackled are not so much the determination of the
number of genetic factors concerned in the transmission of total yield as the analysis
of particular aspects of total yield, e.g., persistency of lactation. The various
characteristics of the lactation must be considered in relation to each other.
In other words, we are not so much concerned with determining the number
of genetic factors involved, as with analysing the lactation curve of individual
animals under a standard environment. (To ensure this, the greater number of
the calvings occur in two months of the year.) Two cows may give the same
yield of milk, but the one may give that yield in 200 days whereas the other takes
300: or the two cows may give the same yields in the same time but yet have
widely different lactation-curves. These, therefore, must be studied with refer-
ence to the various qualities of the milk, amount of fat, sugar, protein, and natural
minerals, as well as the colour, and size of fat-globule, etc., nor must the question
of the relative weights of the cows be ignored both before and after the lactation.
And all these are peculiarities concerning which we can already trace the workings
of heredity. It is of fundamental importance to understand the action of these
characteristics and their reaction on one another.
Thus it is small wonder that simple selection by the mating of the best to the
best gives a large proportion of disappointing results. One cow may yield 2,000
gallons for one set of genetic reasons, whereas another cow will accomplish the
same yield while possessing a very different constitution. There is, therefore,
need for analysis.
Moreover, research of this nature will certainly discover whether abnormal
modes of inheritance are operating, or whether quantity is simply a matter of
multiple factors. These abnormal modes include such things as sex-linked
THE INHERITANCE OF PRODUCTIVITY IN FARM LIVE STOCK.
279
factors, and those combinations of genes which act as inhibitors of yield. The
existence of such modes of inheritance can easily slow down progress by simple
selection.
Further, economic production may actually be best obtained when genes are
in the heterozygous state. Personally, I do not think that this is the case in
milk-production, though there are strong grounds for believing it to hold good for
meat-production. In any case this is obviously a point that must be definitely
ascertained: the required knowledge can only come from experiment.
A further point is to find out whether certain combinations of characters,
desirable from the standpoint of the practical breeder, are genetically possible.
For instance, certain breeders desire cows giving 3,000 gallons of milk with 5 per
cent butter-fat. The analysis-stage might conceivably show this to be as impos-
sible as the desire of other cattle-breeders to establish a roan-coloured breed, roan
being a heterozygote of red and white.
A definite by-product of this type of investigation is that it enables a correla-
tion to be made between the genetical and physiological factors affecting milk-
production. No gene ever works directly on the character. Manifestation of
the character follows some reaction of the anatomical or physiological structure.
Inasmuch as this type of experiment provides what may be called the ' genetic
yield ', these yields may be correlated to certain post-mortem findings, e.g., to the
size of the organs of internal secretion. The maintenance of a herd for genetic
experiment thus provides the ideal material for research into the physiology of
milk-secretion.
It is thus fundamental that, in applying the science of genetics to the complex
problems of milk-production, the various genetic factors first be analysed. There
can be no shadow of doubt that analysis is the pre-requisite of synthesis. Mean-
while, patience must be exercised by those who would question the value of the
application of the science of genetics. Rome was not built in a day, and the
Romans built with stone and not with cattle that require nine months to
conceive and a further three years to produce.
With commendable reserve the United States Department of Agriculture
[2] published only last year the results of the first planned experiment on the
inheritance of milk-yield. It was a simple problem dealing with inbreeding.
The experiment was begun in 1908, a quarter of a century previously. It has now
been incorporated with a bigger experiment started about fifteen years ago, the
results of which, I believe, will cause surprise to those who decry genetical experi-
mentation with cattle on account of the slow rate of reproduction.
It can, therefore, be stated with some confidence that we now see our way
round the Scylla of the disentanglement of the genetic factors. This does in part
answer the question, but not wholly, for on the other side of the genetic ship