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Extracts on Dexters

by James Wilson

from The Principles of Stock-Breeding, published by Vinton and Company, Chancery Lane, 1912

In January 2006, I came across this book in a second-hand bookshop here in Hamilton, NZ. James Wilson, MA, BSc, was, at the time of publication, Professor of Agriculture in the Royal College of Science for Ireland, Dublin. He was also author of "The Evolution of British Cattle and the Fashioning of Breeds" as well as editor of histories of the Shorthorn, the Hereford, and the Aberdeen Angus. This book. "The Principles of Stock-Breeding", was written to introduce notions of Mendelian genetics, then still not widely known to farmers, and apply them to the breeding of farm livestock. Wilson explains the basic ideas of Mendel's views on inheritance and the existence of dominant and recessive traits. This was at a time before the discovery of DNA and the mechanisms of inheritance, and before the notion of genetic mutation was understood. Extracts Two and Three below show how historical literature can include views that have some insight but are later proven incorrect in some respects.

EXTRACT ONE - The bulldog calf as an example of what has been called a "sport" (pages 44-45)

In the first part of his book, Wilson discusses a number of theories that have dominated stock-breeding up to that time, the main ones being "like begets like" (progeny are always like their parents) and Robert Bakewell's "in-breeding" (breeding the best to the best within families). Wilson then examines how exceptions to these principles are understood - when like does not beget like, and when breeding the best gives rise to inferior offspring. After discussing such ideas as supernatural causes, maternal impressions (the idea that a cow will have a red calf if she sees a red animal just after being mated) and "telegony" (the influence of a sire on offspring sired by subsequent males of the same female), he refers to the notion of "sports" (an animal that shows a marked change from the parent stock, due to what we might now call a mutation).

Page 44:

Not only are the phenomena attributed to telegony more satisfactorily explained as reversions [to an ancestral type], but so are those attributed to maternal impressions, accidents, training, and all the other external causes believed to make the young different from their parents.

But there are phenomena of another kind more difficult to trace to their origin, since they may be due to an internal cause or to some "anterior" cause about which we can only speculate vaguely. These we call sports. They are by no means common. Indeed they are far less common than is usually assumed, for many of them are no doubt reversions which we are unable to identify as such. There is, however, an instructive case among live stock. It occurs in the Dexter-Kerry breed of cattle. Many pure Dexter calves are malformed, and the malformation, so far as can be seen and gathered, is always of the same kind. The body is short and stout; the upper jaw is short, giving the head a bull-dog appearance; the legs are extremely short, being little more than finger-length; the tail arises from well up the back; and the ventral skin is unclosed so that the intestines protrude. The animals never live more than a few hours after they are born, and so the possibility of their being reversions is absolutely precluded, since they can never have reproduced themselves. But what are they? The Dexter-Kerry breed is

Page 45:

not old. In all probability it is a cross between Kerry cattle and cattle of North Devon type introduced to the south-west of Ireland in the seventeenth and eighteenth centuries.*  But why should this particular cross produce such calves? Was there something in the North Devon type of cattle and something in the Kerries making them what they were, which, when combined, make the malformed Dexter calves what they are ? The problem is not yet solved; but the case is quoted here merely to indicate how difficult it is to say whether a sport may be really a sport: to say whether it may be absolutely new from the very foundation or whether it may result from the uniting of factors never before united.

* See "The Origin of the Dexter-Kerry Breed of Cattle," Scientific Proceedings of the Royal Dublin Society.
 

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EXTRACT TWO - Inheritance of leg-length in Dexters (pages 46-47)

Wilson goes on to examine the rules that seem to govern exceptions, leading to his introduction of the inheritance of dominant and recessive traits. He refers briefly to the case of leg-length in Dexter where his observations are incorrect - crossing long-leg with short-leg will not always produce short-legged offspring.

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Let us now look at the exceptions more closely and see whether they occur in any regular order; for, if they do, there must be some reason for the regularity, and if we find this reason we may get some hint that may lead to a more satisfactory theory of stock-breeding. It has been found, as a rule, that, when both parents are pure and of the same breed, like begets like; but that this is less and less true as the parents are more and more mixed in respect of their ancestry, and that, when two distinct breeds are mated, the rule breaks down in so far that some of the characters

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of one or other breed may disappear in their progeny while some of the characters of both may blend into something new. Let us take a few of these extreme cases, and, first, those in which a character of one parent disappears in the progeny:-

(i) When red breeds of cattle are crossed with black, the young are black.
 

(ii) When horned breeds are crossed with hornless, the young are hornless.
 

(iii) When cattle of whole colour are crossed with white-faced Herefords, the young are white-faced.
 

(iv) When long-legged cattle are crossed with Dexters, the young are short-legged.
 

(v) When chestnut horses are crossed with breeds of any other single colour, the young are of the other colour.
 

(vi) When Tamworth swine are crossed with Yorkshires or wild swine, the young are Yorkshires or wild in colour according as the parents are Yorkshires or wild.
 

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EXTRACT THREE - The Dexter-Shorthorn cross (pages 100-102)

Later, in his discussion of the transference of characters like coat colour and horns between breeds, Wilson refers to a case where the Dexter was crossed with the Shorthorn. This case is likely to have been the source of his incorrect view in Extract Two that crosses between long-legged cattle and the short-legged Dexter would always result in short-legged offspring, although Wilson is correct that long-leggedness is recessive.  

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Another case of transferring the characters of one breed to another, and so forming a new breed, might be mentioned. This case has the advantage that every step taken since the beginning till now is known. About fifty years ago a red Dexter cow arrived at Straffan House, Co. Kildare, as a present to Mrs. Barton, whose husband owned the well-known Straffan herd of Shorthorn cattle. A few years later a similar cow or her daughter was also brought to Straffan. Of necessity these cows were mated with Shorthorn bulls, and such of their female descendants as were retained in the herd were mated in the same way for over thirty years. At the end of that time the stock descended from the original Dexter cows had at least five crosses of the Shorthorn behind them. Yet, for the most part, they were still the same type of animal as the first crosses had been. Such animals are frequently seen at the Smithfied and Dublin Fat Stock Shows. Excepting for their extremely short legs and shorter skeletal structure generally, their slightly turned in toes, their rougher shoulders and usually something indescribable about the head, they are Shorthorns of the best "beef" type. A full-grown bull weighs about 16 or 17 cwts when fat. These characters, of which the short legs are the most striking, are dominant to the alternative characters in the Shorthorn, and so they are shown by the first
 

Page 101:

crosses. After the first cross 50 per cent, of the original cows' descendants ought to have had legs of Shorthorn length, but the actual number with such legs was luckily below expectation. This, however, is a matter of chance, and when the numbers are not great, expectations are not always realized. When the female stock were five or six crosses away from the Dexter, Mr. Milne, the manager of the Straffan herd, determined to have them mated with bulls of the same breeding as themselves, and the result shows that one step more is apparently all that is wanted to have these animals breeding true to their own type. They throw an occasional Shorthorn of the ordinary type - slightly smaller than the largest type of Shorthorn - as might be expected from the fact that long legs are recessive and that these short-legged Shorthorns have as yet been bred to their own kind for only two or three generations. When, however, the recessive long leg has been eliminated, and, according to what we now know, this can be done quickly, the Dexter-Shorthorns or Shorthorn-Dexters, as they may be called, depending upon the point of view, will reproduce their own kind in all essential characters just like any other pure breed.

This small breed of Shorthorns is proof of a point which is frequently disputed, without the disputants having very accurate information to

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uphold their views on either side. They are exceedingly good "beef" cattle; and recently the writer of this volume saw some of the cows milked, and, when the milk was weighed, it showed the cows to have a capacity of four gallons a day. On trustworthy evidence, they have been known to give five gallons a day. Thus "beef" and milk are not inconsistent in the same animal, nor is a wedge-shaped shoulder a necessary concomitant of high milk yield.

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