NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
382 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, IV.
The determination of the number of wool-fibres growing upon a unit area of
skin has not yet been sufficiently studied to permit of definite conclusions being
drawn. Difficulties in securing accurate samples have been great, and until recently
there has not been available a technique free from serious objections. Burns and
Miller (1931) describe two methods which are calculated to overcome the more
serious objections raised against some of the earlier methods and which have given
satisfactory results up to date. There has not- yet been time, however, to use these
extensively in experiments on the inheritance of fibre population-density.
Preliminary results, however, support the hypothesis that with certain excep-
tions (of which crosses involving Merino parents appear most important) number of
fibres per unit area is inherited in an intermediate manner.
INHERITANCE OF KEMP FIBRES.
During recent years the occurrence of kemp fibres in the wool of sheep has
formed the subject of numerous studies (Bliss, 1926 ; Duerden, 1926; Roberts,
1926; Blyth, 1926 ; and Hirst and King, 1926). The precise nature of the kemp
fibre can now be defined and it is important to differentiate between it. and the
medullated coarser wool-fibre, such as is commonly found in Romney wool. Kemp
fibres, as they occur in domesticated sheep, represent a remnant of the coarse,
hairy, outer-coat of the primitive sheep. As typically encountered, the kemp fibre
is short, thick, rigid, and finer at tip and root than along the shaft; it possesses a
fairly regular wave or crimp in one plane only, is extremely brittle, has a ' dead
white' or chalky appearance, and is medullated except for the short fine tip and,
when shed naturally, for a portion of the proximal part of the shaft. In many
breeds, if not in all, kemp has the further characteristic that its period of growth
and the time of its shedding occur independently of the other constituent fibres in
the fleece. Some kemp fibres are "cut off at shearing time; others may have
already been shed but are "still entangled amongst the wool-fibres of the fleece ;
whilst some are shed and fall to the ground before the wool-fibres have grown long
enough to retain them.
Owing to its lack of elasticity and the difficulties met with in attempting to dye
it, the presence of kemp in wool for manufacturing purposes is a decided disadvan-
tage. There have been strong reasons for considering that differing degrees of kempi¬
ness are inherited. Barker (1931) admirably summarizes these as follows :—
1. In the course of work on the Welsh Mountain Sheep it has been found that
there is a very close connexion between the type of birth-coat possessed by the
INHERITANCE OF WOOL-CHARACTERS IN SHEEP
383
lamb and the proportion of kemp subsequently developed in the adult fleece. The
type of birth-coat shown by the lamb is a matter of inheritance.
2. If sheep are compared which have just the same type of birth-coat, differ-
ences in kempiness may be discovered, and data are at present being accumulated
to discover how far, in such a case these different degrees of kempiness are inherit-
ed. This work goes to show that inheritance is undoubtedly the important factor.
3. It is easily possible to find in one and the same flock, sheep of the same
age, kept under precisely the same conditions, which will show absolutely different
amounts of kemp in the coat.
4. Sheep kept under artificial conditions, for example, sheep that are being fed
for show, if the coat was originally of a kempy nature, still preserve this feature.
5. Individual sheep examined over a period of years do not show any large
differences between the proportions of kemp in different years.
6. Even in pure Merino flocks a sheep will very occasionally occur with a coat
that is quite full of kemp. This is a good example of what is popularly termed
' reversion', a purely hereditary phenomenon.
7. Those breeders who have the greatest experience of intensive sheep hus-
bandry, for example, the Merino breeders of Australia, have no doubt whatsoever
that kempiness is a matter of breeding.
To sum up, therefore, it may be confidently stated that differences in degree of
kempiness are predominantly a reflection of hereditary differences, and that if
environmental conditions do cause any effect, that effect is very small in compari-
son. The theory that lowland breeds of sheep, kept under adverse conditions on
the mountains, would rapidly develop kemp, has nothing to support it.
It may be added that the complementary theory that kempy mountain breeds,
when kept under low-ground conditions, would grow wool free from kemp has been
shown on numerous occasions to be erroneous.
Bryant (1933, unpublished) has shown that when the degree of kempiness in
a Scottish Blackface ram used for breeding purposes is determined upon a percen-
tage-weight basis, the figures obtained are significantly correlated with the degree
of kempiness exhibited by his progeny. His analysis of the inheritance of kemp
in this breed indicates that there are probably major and minor factors involved,
the former of which can readily be manipulated by practical breeding, though the
minor factors are more refractory. If this conclusion is substantiated, a means
will be at hand whereby in the Blackface breed kemp can be reduced to negligible
proportions, though absolute eradication may not be possible. From the work of
384 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, IV.
Roberts and White (1930) with Welsh mountain sheep there is strong evidence
that degrees of kempiness are similarly inherited in that breed, and as other breeds
of sheep form subjects of study there is every reason to believe that similar
principles of inheritance will apply equally to them.
It is necessary carefully to differentiate between the true kemp fibre and
coarse, sometimes hairy, medullated fibres which are seen particularly in britch
wool from various breeds of sheep. No references to generic work on the inheri-
tance of these fibres have been found, but Dry (1931) has studied their occurrence
in New Zealand (mainly in Romneys), whilst; a technique which has for its aim
the rapid and easy estimation of the proportion of medullated fibres in a sample
of the wool of New Zealand Romney sheep, has recently been reported by Elphick
(1932). This is called the 'benzol test'. It consists of examining a staple of wool
from a given sheep by the naked eye after immersion in benzol, which has a
refractive index practically the same as that of non-medullated wool. The air-
content in a medullated fibre, having a refractive index higher than that of the
solid wool-fibre enables these medullated fibres to be readily seen by the naked eye.
It is stated that the technique is being applied to breeding flocks with a view to
determining the mode of inheritance of medullated fibre, but to date no results are
available.
INHERITANCE OF CERTAIN SECONDARY WOOL-CHARACTERS.
In addition to the more important characteristics of the fleece which have been
discussed, there are certain minor characters which have been studied. Some of
these are of very considerable practical importance, and deserve more attention
than has already been paid to them. Such recorded work as is available will be
briefly considered.
' Chalk-face' in Merinos.—' Chalk-face' or ' Frosted-face' are terms chiefly
used in America to designate the presence of stiff, coarse, dull-white hairs on the
faces of Merino sheep. These appear in sharp contrast to the uniform soft fine
fibres which form the normal hairy covering of the faces of this breed, and which
are referred to by breeders as ' velvety . This feature of ' velvetiness' on the
face is regarded by some as being correlated with excellence of fleece and according-
ly is desirable in good-quality breeding stock. Conversely, chalky fibres are
believed to be correlated with coarseness of fleece. In addition, an abundance of
chalky fibres are liable, when they are shed, to become entangled in the fine wool
of the neck. This requires a more careful skirting of the fleece with, in the
aggregate, a not inconsiderable wastage of fine wool.
INHERITANCE OF WOOL-CHARACTERS IN SHEEP
385
Warwick (1931) and Warwick and Bell (1929) carried out experiments to
determine the mode of inheritance of chalky fibres. They obtained results as
shown in the following tables from Warwick (1931) :—
Chalky-facedXclalky-faced Merino sheep.
—
Expected (3-1) . . . . . . . . . .
Actual . . . . . . . . . .
Deviation . . . . . . . . . .
Chalky
hairs
present
15
13
—2
Ckalky
hairs
absent
5
7
+2
Total
20
20
—
Clean-facedXchalky-faced Merino sheep.
—
Expected (1—1) . . . . . . . . . .
Actual. . . . . . . . . .
Deviation
.
.
.
.
.
.
.
.
.
.
Chalky
hairs
present
7
3
—4
Chalky
hairs
absent
7
11
+4
Total
14
14
—
Warwick, therefore, concludes that the condition is due to dominant rather
than to recessive characters, and suggests that only one pair of dominant factors
is responsible. Rigid and continual selection against chalk-face would therefore
serve to eliminate this condition from a stock of breeding ewes, and only rams free
from it should be used.
Soft, and stiff hairs on face. Wriedt (1925) reports the results of experiments
conducted to determine the inheritance of soft and stiff hairs on the face, especially
the nose, of Rygaya sheep in Royaland, Norway, He obtained the following
results:—
(1) Soft haired ♂ × Soft-and Stiff-haired ♀♀
41 Soft-haired
2 doubtful
386 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, IV.
He concludes this ram to have been homozygous and soft hair to be a domi-
nant character.
(2) Stiff-haired ♀♀ × Soft-haired ♂ × Soft-haired ♀♀
3 Soft-haired
3 Stiff-haired
6 Soft-haired
1 Stiff-haired
He concludes that this ram was heterozygous. Four other rams investigated
proved to be heterozygous; with soft-haired ewes they gave a total of 31 soft-
haired, 5 doubtful, and 5 stiff-haired offspring.
From these and other data, Wriedt concludes that the character for soft hair
is based upon a simple Mendelian dominant factor.
Head furnishings.—Among many breeds of sheep there is developed, as a breed
characteristic, a lock of wool on the poll extending forward on to the forehead.
This is referred to by breeders variously as a ' forelock ', forehead lock', ' muff '.
It is to be seen to its maximum development in the English Lincoln Longwool,
English Leicester, Oxford, Cotswold, Devon Longwool, and Wensleydale, and is
to be differentiated from an extension of the wool of the neck on to the face as is
seen in the Shropshire, Hampshire, and Southdown. Many breeds, such as
Suffolk, Cheviot, Border Leicester, and Derbyshire Gritstone, have bare heads
quite devoid of wool, with a clean line of demarcation between the wool-bearing
skin of the neck and the hairbearing skin of the head and face.
In other breeds, in particular, the dark-faced horned British Mountain breeds—
Scottish Blackface Mountain, Swaledale, Rough Fell, and Lonk—there are animals
to be met with which have bare heads and others which have considerable amounts
of wool in this situation, though in high-class flocks animals are usually bred with
clean heads free from wool.
The presence of much wool on the face, and especially round the eyes, is a
disadvantage in countries where vegetable burrs are common, where there is much
risk of blown sand getting into the eyes and silting in the wool around them, or
where severe snowstorms are common. In Scotland, particularly on the mountain
grazings where the Blackface ewes may have to withstand very severe snowstorm
and blizzards, a heavy head furnishing (' muff ') is not infrequently the cause of
much loss. Snow gathers in the wool, partially melts, then frequently freezes and
forms a stiff cap over forehead and eyes which blinds the animals and not infre
quently results in loss through falling over steep rocks, into streams or bogs.
INHERITANCE OF WOOL-CHARACTERS IN SHEEP
387
The mode of inheritance of head-furnishings is consequently of considerable
importance.
Wood (1905-6, 1908-10) found that in F 1 animals from Suffolk (bare-headed)
and Dorset Horn sheep (wooly heads) the amount of wool on the forehead was
more or less intermediate between that of the parental types. In F 2 and subse
quent generations segregation was marked, but no definite proportions could be
given. Thilo (1922) reports similar results in the work carried out in the founda
tion of the Neuenkirchen Meles sheep from English Leicester (tufted) ♂ × Merino
(clean) ♀♀.
Pucci (1915) found that, in crosses between Rambouillets and sheep of the
middle Tiber valley, the extension of fleece of the Rambouillet on to head, throat;,
and limbs, was dominant. (Middle Tiber Valley sheep have these areas devoid of
wool.) In the F 2 generation simple segregation took place.
In experiments carried out at this Institute which Lincoln ♂ × Cheviot ♂ ♂
crosses, the head-furnishings of the Lincoln type were found in all F 1 animals,
whilst with Shetland ♂ × Lincoln ♂ ♂ crosses the degree of head-furnishings was
somewhat less than in the Lincoln parent, but no bare-headed F 1 animals occur
red. F 2 generations were not reared. Observations upon a very large number
of Blackface sheep show quite clearly that in this breed presence of wool on the
forehead is dominant to its absence. We must postulate more than one pair of
allelomorphs, however, to account for the variations in degree of ' muff' which
are encountered in this breed. Details will, it is hoped, be published later.
Localized covering of wool. Settegast (1878) reported that a cross of Mouflon,
which has no wool on head and legs, with Merino, which has woolly head and
legs, gave F 1 of the Mouflon type. Arkell (1910, 1912) crossed Shropshire (woolly
head and legs) with Suffolk Down (woolless). Out of 99 F l, 3 had a lower grade of
wool-furnishings than the Suffolk, 9 were like the Shropshire. The remainder
were intermediate. There was no sex-linkage and reciprocal crosses gave similar
results. Probably more than one factor is involved. Pazzini (1915) used Ram
bouillet rams on sheep of the Tiber valley, which have woolless head, neck, belly,
and legs. The F 1 had wool on the head to the temples and round the ears, also
on the neck, belly, and legs; the F 2 exhibited an even closer approach to the
Rambouillet. Adametz (1920) found among his crosses lambs with a typical Kara
kul fleece but a Rambouillet type of bead-covering. Thilo (1912, 1922) reports
that the head- and leg-covering of Mele sheep is intermediate between the parents.
The British Research Association (1925) recorded in the F 1 of the Blackface X South
down cross that a tuft of wool occupies the position of the forelock,
H
388 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, IV.
DISCUSSION.
It has been frequently pointed out by various authors that no simple Mendi-
lian approach is applicable to a study of the various characters which together
constitute the fleece. Wool-production by the skin of the sheep depends upon a
multifactor system, whether the fleece is considered as a unit, or whether the
study includes only one, or a combination, of its various physical attributes.
The marked exception to this is the character of colour. The exhaustive studies
made by Dry (1924, 1926, 1927), Roberts (1924, 1926 (a) 1926 (d), 1927, 1928,
1931), Roberts and Jenkins (1926), Roberts and White (1930), Vassin (1928), Ada-
metz (1917), and many others show that fleece-colours in sheep are inherited in
epistatic series. Colour has, however, not been considered in this paper and will
not now be further discussed.
Where only one wool-character has been studied, the bulk of the evidence
from widely divergent sources shows that with few exceptions the character in
question is exhibited by the progeny to degree which is intermediate between the
parental types. It is also instructive to note that, in cross-breeding experiments
in which several fleece-characters have been studied simultaneously, the interme-
diate characterization of the type of wool grown by the F 1 generation is constant-
ly stressed.
The practical sheep-breeder both in Britain and in the wool-producing coun-
tries of the Empire has conducted operations along lines which are in accordance
with this principle of intermediate inheritance, and has obtained most remarkable
results. That individuals do occur, especially sires, which transmit to their pro-
geny more of their own fleece-characters than would be expected were inheritance
of these always strictly intermediate, is not disputed. But a theory of general
intermediate inheritance is able to accommodate such prepotent animals as these.
The degrees of homozygosity for any given character must vary, and it is readily
possible by suitable selection to concentrate the factors for one or another fleece-
quality in a strain or in individual animals. Where such concentration has pro-
ceeded to a degree greatly in excess of the general average for the breed, it is to
be expected that progeny will exhibit the quality under consideration to a more
marked extent than will the average animal. In almost every breed of domesti-
cated sheep there has been one outstandingly good animal during recent times,
and in some breeds there have been several. At sales, competition for them or
for their progeny has been fierce, and remarkable prices have been paid. In
subsequent breeding they have impressed their characters upon their progeny
in a manner which makes their recognition easy. It is interesting to speculate
whether such individuals may not have been mutations, but in the absence of
any proofs, speculation is undesirable.
INHERITANCE OF WOOL-CHARACTERS IN SHEEP
389
If those physical characters of wool which have been investigated are
considered collectively in inheritance, there strongly emerges the suggestion that
it will be unprofitable in the present state of our knowledge to attempt an analysis
of the fleece of the sheep upon a basis of individual genetic factors ; rather does
it seem desirable to accept as a working hypothesis a multifactor basis for each
physical character of wool. It is permissible to consider that in the great majority
of cases the phenotype behaves in breeding as a genotype, even though it may not
be identical with it. Policies of breeding which aim at eradication of undesirable
features, and those which are drawn up to give effect to a desire or need for
improvement, may safely be framed upon this principle, which is, after all, that
which the practical breeder has endeavoured to follow during the past. Improve-
ment proceeding towards an ideal defined type of wool must be progressive,
and the alert sheep-owner, in a position to recognize the outstandingly good
animal, will seize every opportunity to make the best use of its potentialities.
SUMMARY.
1. Desiderata for genetic experiments where wool-characters are to be studied
are enumerated and discussed.
2. A review of literature dealing with the inheritance of fineness, length of
fibre, crimp, fleece-weight and density, kemp, and certain accessory attributes of
the fleece, is given. Results of the writer's work carried out in the Institute of
Animal Genetics are included, and particular difficulties experienced in obtaining
reliable data are summarized.
3. The inheritance of wool-characters in general is discussed and conclusions
drawn from the works cited are given.
ACKNOWLEDGMENTS.
I am indebted to the Imperial Bureau of Animal Genetics, and in particular
to Miss M. V. Cytovich, for assistance given in searching literature and making up
the Bibliography. To Dr. J. E. Nichols and to Mr. D. M. Bryant I am greatly
indebted for allowing me to use some of their results which have not yet been
published.
BIBLIOGRAPHY. 1
Adametz, L. 1917. Studien Über die Mendelsche Vercrbung der wichtigsten Rassenmerkmale der
Karakulschafe bei Reinzucht und Kreuzung mit Rambouillets.
Bibliotheca Genctica, 1, 258 pp.
—1918.
Über
die Vererbungsweise der Haarfeinhcit bei Kreuzungen von Karakul mit
Rambouillet. Dent. Landw. Tierzucht, 22.
1 t.t.=translated title.
H 2
390 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, IV
Adametz, L. 1920. Zur Vererbung der Wollcharaktere. Deut. Landw. Presse, p. 81.
—1917.
Über
die graue Farbenvarietät des bocharischen Fetttschwanzschafes (Shiras).
Landw. Monatsh., No. 2, 11 pp.
Arkell, T. R. 1910. Report of the Department of Animal Husbandry. New Hamp. Agric. Exp.
Sta., Bull. No. 151.
—1912. Further Reports on Inheritance of Horns and Wool Covering in Sheep.
Amer. Breed. Ass. Rpt., 8, 561-8.
Bailey, P. G. 1914. Preliminary Note on Wool Inheritance. Brit. Ass. Adv. Sci. Rpt., 654-5.
Barker, A. F. 1925. Genetics and Wool Production. (Pan-Pacific Sci. Congress, Sydney, 19-60)
University of Leeds.
Barker, S. G. 1931. Wool Quality. H. M. Stat. Office, 328 pp.
Barker, S. G., and Norris, M. H. 1930. A Note on the Physical Relationships of Crimp in Wool.
J. Text. Inst., 21, T. i-T. 17.
Baur, E., and Kronacher, C. 1919. Gibt es konstante intermediäre Rassenbastarde in der Sohaf-
zucht ? Duet. landw. Presse, 713-14.
Belehov, P. P. 1928. Wool Quality in F 1 and F 2 Hybrids in Coarse-wooled × Merino Crosses
(t. t.). Chapli Zool. Exp. Sta., Bull. No. 3, 49-81.
—1932.
Inheritance of Wool Qualities in Mouflon×Chuntuk Cross (t.t.). Chapli
Zoot. Exp. Sta., Bull. No. 7, 88-101.
Belehov, P. P., and Reinbot, E. I.1928. Wool Qualities of F 1 Hybrids from Various Breeds
with Shropshires× Hampshires (t. t.). Chapli Zoot Exp. Sta., Bull. No. 4, 89-120.
Bliss, H. J. W. 1926. Flat Kemp. J. Text. Inst, 17, p. T. 254.
Blyth, J. S. S. 1926. Kemp Fibres in Fleeces of British Breeds of Sheep. Brit. Res. Ass. Wool.
Worst. Indust., Publ. No. 59, 28-32.
British Research Association for the Woollen and Worsted Industries, 1922-4, 1925. Report on
Sheep Breeding Experiments, Publ. Nos. 14, 29, 45.
Burns, R. H. 1925. Mendelian Inheritance in Sheep. Nat. Wool Grower, 15, 34-5.
Burns, R. H., and Miller, Wm. 1931. Sampling Instruments to determine Flecce Density in
Sheep. J. Text. Inst., 22, T. 547-T. 564.
Davenport, C. B., and Ritzman, E. G. 1926. Some Wool Characters and their Inheritance. New
Hamp. Agric. Exp. Sta., Tech. Bull. No. 31, 58 pp.
Davy, J. B. 1927. Persian and Merino Sheep Crosses. J. Hered., 18, 25-32.
Dry, F. W. 1924. The Genetics of the Wensleydale Breed of Sheep. 1. The Occurrence of Black
Lambs. J. Genet., 14, 203-18.
—1926.
Colour Inheritance in the Wensleydale Breed of Sheep. J. Text. Inst., 17, T.
180-T. 186.
—1927.
Mendelian Breeding with Wensleydale Sheep. J. Text. Inst., 18, 415-20.
—1931.
Fibre Types in the New Zealand Romney Hogget. Wool Ind. Res. Ass. Bull.
2, 66-75.
Duerden, J. E. 1926. Kemp Fibres in the Merino. J. Text. Inst. 17, T. 268-T. 273.
Elpatjevsky, D. W. 1929. Methods of Improving Coarse-wooled Sheep (t. t.). Bull. Live Stock
Breed. No. 9, 71-9.