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"The Significance of an Achondroplasia-Like Condition Met With in Cattle"

Part III

by F.A.E. Crew

in Proceedings of the Royal Society of London, volume 95, 1923, pages 228-255.

Page 231 (Cont'd)

III -The Monstrous Calf of the Dexter

As time went on, it may be assumed, the matings became more and more confined to those between Black Dexter-type and Black Dexter-type, and that the phenotypic selection which was thus practised was really meant to isolate the genotype BBSS.

Slowly it came to be recognised that this phenotypic selection resulted in the production of a deformed and still-born calf; that, as the mating of Dexter-type and Dexter-type became more common, the proportion of these monstrous calves increased. Ultimately, it was accepted that with such

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matings a proportion of still-born monstrous calves was to be expected. In 1919, the society formed in 1917 to promote the interests of Kerry and Dexter cattle breeding in Ireland, decided to change its name to “The Kerry Cattle Society of Ireland.” “This alteration was deemed advisable as herds of pedigree Dexter cattle have practically ceased to exist in Ireland owing to the difficulty of breeding these cattle pure. It is the experience of Irish breeders that when Dexter cows are mated with a Dexter bull a large proportion of the progeny are either still-born or deformed. As a result of constant disappointments, owners have gradually given up the attempt at breeding pedigree Dexters and, so far as Irish breeders are concerned, their whole attention is now directed to the development of the Kerry breed.”

“Concurrently with the ban upon Dexters in Ireland, a boom was started in England.” To supply the demand for Dexter cattle, the Irish breeders earnestly sought for methods by which Dexter-type calves could be produced and the monstrous calf avoided. The result of their experimentation has been that the Irish Dexter, the so-called “foundation stock” Dexter, is got not by a Dexter x Dexter mating but by using a Dexter bull and Kerry cows. This mating has never yielded a monstrous calf; it has produced on the average equal numbers of good type Dexters and of “sneem” Kerries. The Kerry-type animal so produced is a diminutive Kerry; Sneem is the district of Kerry in which the foundation stock Dexter is raised for export to England, and “sneem” is used locally as a term of reproach, being applied to any undersized creature. The relative numbers of red and of black individuals varies considerably, for it is certain that many Kerries are heterozygous for their black coat colour character.

In England, the English Kerry and Dexter Cattle Society was founded in 1892, and published its first Herdbook in 1900. By the regulations laid down therein, “a cross between the Kerry and the Dexter is considered a half-breed and cannot be entered.” Quickly, as Wilson says, “what was formerly known to Kerry men now became known to other breeders who bred Dexters, according to the rules of the Herdbook, that such a procedure invariably resulted in the production of a proportion of dead misshapen calves.”

The abnormalities which these still-born calves exhibit are constant, and are so characteristic that the foetus is known as a “bull-dog” calf. The cranium is bulging, the nose markedly depressed, the lower jaw protruding, the upper lip is split, baring the teeth, while the swollen tongue, thrust far out, curls up over the nose. Owing to the disproportionate development of the buttocks, the tail seems to have its origin far up on the back; usually

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there is a gaping deficiency of the abdominal wall through which the intestines pass to form a large umbilical hernia. The skin hangs loosely in folds; there is abundant subcutaneous fat. The limbs are ridiculously short and the digits unusually separated.

The period of gestation in the Dexter is approximately 284 days. In the great majority of cases it can be foretold that a pregnancy is to terminate in the production of a “bull-dog” foetus, for in such cases the pregnant cow begins to increase in size very rapidly about the third or fourth month, and ultimately becomes very distended. The early obliteration of the hollow in the flank just in front of the hip is recognised as a sure sign of impending trouble. Then it is noticed that the cow is losing “water,” which dribbles from the vulva, and that she is becoming less and less distended. After a time the loss of fluid ceases, but after a short interval the cow is as “big” as ever. Again there is the flow of fluid from the vulva and the decrease in size, and again the cycle is repeated. Following one of these discharges of fluid from the vulva the foetus is aborted. The fluid is described as being clear in the majority of cases; in a few it has been turbid.

But, as Seligmann has previously recorded, it is not invariable for a Dexter with a considerable degree of excess of amniotic or allantoic fluid to give birth to a deformed calf. Moreover, the pregnancy which results in the abortion of a dead monstrous calf is not invariably associated with such excess. Extremely rarely, so the breeders say, the first indication of anything abnormal is a premature labour. In such cases the calf is not delivered naturally, it always must be removed by operative procedure and is dead when delivered.

The puerperium following the delivery of the “bull-dog” differs from that following the birth of a normal calf. The placenta comes away in small fragments or has to be extracted manually, instead of being thrown off complete in a half to four hours. In fact, herdsmen will state that there is no afterbirth in the case of the “bull-dog.” The lochia last longer than is usual, the blood-stained discharge persisting in certain cases even as long as a fortnight instead of the usual one to four days. The abortion of a foetus, other than a “bull-dog,” is followed by an immediate cessation of mammary activity; the abortion of a monstrous calf on the contrary does not interfere with this and the cow produces milk.

The normal Dexter calf is a small individual compared with calves of the same age but of larger breeds. No specimen of the normal Dexter foetus has been available for comparison, but an “off-type” (a Kerry-type) foetus

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was obtained at the eighth month of pregnancy. The “bull-dog” foetus of the same age is very much smaller.
 

An examination of many specimens has shown that there is never any suggestion of putrefaction or of mummification of the foetus. The abortion quickly follows the death of the calf. The death of the foetus is associated with severe foetal anasarca-foetal dropsy - in the case of the earlier abortions and of the majority of the later ones - and with profound dystocia in the cases which proceed until near term. In practically all cases in which there is hydramnios (or hydrallantois) foetal anasarca is present, and the foetus is a fluid-logged shapeless mass and the almost complete subcutaneous covering of the abdominal wall is devoid of skin over a circular area based upon the umbilical cord. In the case of the older foetus, death results from dystocia. The prolonged and difficult labour is made inevitable by the shape and consistency of the foetal head which cannot be accommodated by the maternal birth passages.

The “bull-dog” foetus is a creature which has a head of unusual shape and consistence. The size of the foetus and the shape of the head are to be regarded as significant features of the “bull-dog” calf.

In the herdbooks there are to be found many entries of “premature” or of “dead” in the column which shows the births during the year. It is not to be expected that such a record is critical. English Dexter breeders, anxious to have this problem solved, supplied the following absolutely trustworthy figures:

     Total births, 646;     Normal calves, 630;     “Bull-dog” calves, 116.
         i.e. 1 in 5.5 births.

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At first sight there would seem to be neither rhyme nor reason in the occurrence of the monstrous calf. Some herds are singularly free from them, others yield so many that the breeder gets rid of his stock. A certain cow will produce a series of most excellent Dexter calves and then to the same sire will yield a typical monster. A cow to the service of several different bulls will produce a series of “bull-dogs,” and then the next season produce a prize-winner. There is no Dexter out of a Dexter-by-Dexter mating that is not related more or less closely, to a monstrous calf. The “bull-dog” appears in all herds in numbers that range from 5 to 30 per cent of the total births. During the last two years the present writer has examined 27 cases.

Just as black is the more common colour of the Dexter and for the same reason, so is the coat colour of the “bull-dog” foetus more often black than red. Of the 27 cases examined, 20 have been black and the remaining seven have been red, as close an approximation to a 3 : 1 ratio as can be.

Of the 27 cases examined, 21 have been males and six have been females. For a long time none but a male was received and sex-linkage was suspected. But more recently six females have been examined; at first these were regarded as possible cases of abnormal differentiation of the sex-organisation in a male, but the demonstration of definite ovarian tissue in the gonads has made it certain that the condition is not sex-linked. In the older foetuses the scrotum is well defined as is also the vulval cleft, but in the earlier specimens the sodden skin and the great rent in the abdominal wall make the identification of the sexual apparatus peculiarly difficult. Moreover, since the specimens cannot be examined until at least 18 to 24 hours after delivery the histological evidence is rather weakened. But the evidence is such as to show quite definitely that the “bull-dog” foetus may be either male or female, though, if the series of cases examined can be regarded as a representative sample, the majority of monstrous calves are male.
 

On to Part IV