BREEDING OF FARM ANIMALS.

New Zealand Journal of Agriculture, Volume XXVII, Issue 2, 20 August 1923, Page 103

BREEDING OF FARM ANIMALS.

THE LAWS OF HEREDITY.

Paper read by

Mr. W. D. Hunt,

Wellington, to the New Zealand Board oi

Agriculture.

I should like to state at the outset that I think it can be taken as an established fact that the first necessity in stock-breeding is ability to select the best animals ; that knowledge of the laws of heredity is no use without this ability ; that a breeder will never get anywhere either in breeding purebred stock or crossbred stock unless he has the ability to select good animals; that the person who wishes to succeed as a breeder of any class of animals must first learn how to select, and when he has learnt this, then- —but not till thenwill he be ready to make use of the knowledge of the laws of heredity.

I would like also to state before I go further that one of the first things a man must do if he wishes to succeed as a stock-breeder is to consider his country-what is the class of animal best suited to his country. The breed of stock must be selected that will suit the country they have to occupy. A breeder may be an excellent judge of his breed, and know the last word on the laws' of heredity, but he will never get far if his stock does not suit his country. No breeder can succeed with his country working against him.

Another necessity, if a breeder is to be successful, is proper feeding. I do not mean overfeeding, but feeding that will give the stock a chance of full normal growth and development. Particularly is this necessary when the stock are young. An animal underfed when young may, if well fed afterwards, develop to normal size. Its growth, in fact, has been arrested for a time, and has afterwards moved on again until normal size has been reached. The period of starving, however, leaves its mark on constitution, and constitution is the most important attribute of all in stud stock.

The natural laws that govern heredity are not yet fully known; the study is as yet in its infancy. It is only about 168. years since Bakewell first started his work, and while he and other master breeders discovered the methods that were necessary to get the results they achieved, it is really only during quite recent years that we are beginning to learn some of the reasons why the methods adopted give the results obtained. In this connection it is found that the broad principles that govern inheritance are much the same in the vegetable world as in the animal world. Inquiry' into the laws governing the inheritance of animals can be much helped by studying inheritance in plants. Experiments can be' made with much larger numbers and in such shorter time with plants than is possible with animals, and definite results with plants are thus obtained much more quickly. .

The work of the really successful breeders, both past and present, has been based upon the principle that. “ Like begets like, ,, with a continual tendency to variation.” In the working-out of the principle

it was found that while the offspring might come like the parents, it might also come like grandparents or more remote ancestors. This made it important that all the ancestors should be as nearly as possible alike in type, and all to be of the type that the breeder is aiming to get. This brought out the importance of purity of blood. All the ancestors ’must not only be of pure breed, but of similar strain and type. A crossbred may be as fine an animal as a purebred, but it was found it would not breed true. The same applies to the crossing of different strains within the same breed where the strains differ from each other in type.

While the first part of the principle “ Like begets like ” enabled breeders to fix their type, it was the second part of the principle; “ with a continued tendency to variation,” that enabled breeders to improve their stock. In nature no two things come alike. Every animal has individuality. Every animal is different from every other animal. There is perpetual variation. These variations are carried on to the next generation and lead to further variation. In nature the law of the survival of the fittest eliminates variations towards inferiority and perpetuates variations towards superiority. It is thus that the present animal and vegetable worlds have been established. The stud breeder temporarily suspends the law of the survival of the fittest and puts his own selection in its place. His job is to perpetuate all variations towards superiority, and cull out all variations towards inferiority. It is his success or otherwise in doing this that fixes his place as a breeder.

I said a breeder temporarily suspends the law of the survival of the fittest and puts, his own selection in its place. . Nature has for the time being merely transferred her law of the survival of the fittest from the breeder’s stock to the breeder himself. If he selects his variations well he gets a market for his stock and he goes on breeding. If he selects unsuccessfully he loses his market and is forced out of the breeding business. Fortunately, nature’s law always operates in the end. The stud breeder can only permanently take a hand if he is an improver. If he fails to improve he is forced out of the business.

I have tried to show the importance of pedigree, and at. the same time the fallacy of thinking of pedigree only without seeing that the right animal is with it. Variations towards inferiority will perpetuate and intensify themselves just as surely— fact, probably more surely —than variations towards superiority.

The Merino sheep which has been developed to its present state of perfection in a comparatively short time by the breeders of Australia and Tasmania is an example of what can be done by the skilful use of nature’s variations. The Merino is grown almost entirely for wool, and the desire was to produce a sheep that would grow the greatest amount of the best quality of wool. The. following is a note of results obtained by the noted Tasmanian breeder James Gibson, of Belle Vue Estate. These results were obtained entirely from Belle Vue blood ; no outside blood was introduced.

In 1868 he bred the ram Sir Thomas, who was the most noted Merino of his time. He was sold when six years old for 680 guineas, which was the highest price up to that time ever paid for a Merino ram. The heaviest fleece Sir Thomas ever cut for twelve months’

growth was 12 lb. In 1872 Sir Thomas sired Sir Thomas 2nd, who cut 14 lb. of wool, an increase of 2 lb. on his sire. . As an indication of the value put on Sir Thomas 2nd, he was sold when six years old for 604 guineas. In 1878 Sir Thomas 2nd got Golden Tom, who cut a fleece of 17 lb. He was sold when four years old for 500 guineas. In 1880 Golden Tom got Treasurer, who cut 18 lb. wool, and was sold in 1883 for 300 guineas. Treasurer got Golden Horn, who cut 20 lb. wool, and Golden Horn got Golden Horn 2nd, who cut 26 lb. In 1890 Golden Horn 2nd sired President, one of the most famous Merino rams ever known in Australia. He cut only 23 lb. wool, but he had with it a quality and evenness which, together with his general symmetry and bearing, made his name a household word all over Australia. He was sold in 1896, when six years old, for 1,600 guineas, the highest price paid up to that time for a Merino ram. In 1895 President got President 2nd, who cut 27 lb. wool. In 1898 President 2nd sired President 3rd, who cut 30 lb. wool. In 1900 President 3rd sired Patron, who cut 36I lb. wool. Patron was sold in 1907, when seven years old, for 1,000 guineas.

Thus in a little over thirty years, by selecting those variations in the direction of increased weight of wool, the weight was increased from 12 lb. to 365 lb., and this was done entirely within the flock without bringing in any outside blood.

THE MENDELIAN LAW AND SOME EXAMPLES.

The discoveries of Mendel have opened up a new field of thought and experiment in. breeding, and explain the - reasons for many results. These discoveries were first published in 1865, but their importance was not realized at the time, and it was not until the beginning of the present century that they became generally known even to scientists. As time passes, it is becoming more and more evident that the Mendel laws of heredity are very far-reaching, and it is worth considering them closely in connection with any breeding plans. Most people connect Mendel’s results merely with the crossing of long and dwarf peas ; but this was only one of his experiments. He found the same results were obtained with round and wrinkled pea-seeds, with yellow and green seeds, with brown and white seeds, with inflated and constricted pods, with green and yellow pods, and with axial and terminal position of flowers. In all these experiments the first-named quality was found to be dominant and the second recessive.

I will give an example of the working of the Mendel law in the breeding of live-stock. It is well known that red calves sometimes appear in pure herds of Aberdeen Angus cattle, and that red-and-white calves appear in pure Friesian herds of black-and-white cattle. Black and red are Mendelian characters. Black is dominant, and red recessive. A purebred black animal produces germ - cells which contain what is known as the factor for black. A purebred red animal produces germcells containing the factor for red. The birth of a new animal arises from the union of -two germ-cells. If at some period in the history of the herd a pure-black animal is. mated with a pure-red the result will be a uni on of black and red germ-cells. In the resulting egg which is to give rise to the new animal the black factor is dominant to or conceals the red, which is recessive ; the calf, although black in appearance,

will contain the red factor in 50 per cent, of its germ-cells and the black factor in the remaining 50 per cent. For example, cross a black animal with a red and we get this result : — Black Animal. Red Animal. Germ-cells . . . . . . . . Black Red. The result of this cross is a black animal, because black is dominant to red ; but half the germ-cells of the progeny are red. Cross two animals bred this way and we get the following results : — Bull. Cow. 50 per cent, germ-cells.. . . . . Black Black. 50 per cent, germ-cells. . . . . . Red Red.

The progeny may be the result of the meeting of a black germ from the bull with a black germ from the cow, and the result will be a pureblack carrying only the factor for black in its germ-cells. The progeny may be the result of a black germ from the bull meeting with a red germ from the cow, and the progeny, while black in colour, will have the factor for red in half its germ-cells. A similar result will come from the meeting of a red germ from the bull with a black germ from the cow. A fourth alternative is the meeting of a red germ from the bull with a red germ from the cow ; the progeny will then not only be red in colour, but all its germ-cells will carry the factor for red, and it will breed true as a pure-red. One-fourth of the calves from this cross are therefore pure-blacks, one-half are blacks carrying the factor for red in half their germ-cells and the factor for black in the other half, and one-fourth are pure-reds. To illustrate the result :— Offspring - No. 1. No. 2. No. 3. No. 4. 50 per cent, germ-cells . . Black Black Black Red. 50 per cent, germ-cells . . Black Red Red • Red.

No. i bred with another pure-black will breed true blacks. No. 2 and Nd. 3 bred together will give the same results over again as those first explained ; and No. 4 is a pure-red, and if bred with other pure-reds will breed true.

Now let us examine the result of crossing offspring Nos. 1 and 2.' We get the following :— ' No. I. No; 2. 50 per cent, germ-cells .. ... . . Black Black. 50 per cent, germ-cells .. . . . . Black Red. '

If either of the black germs from No. 1 unite with the black germ in No. 2 we get pure-blacks, but if either of the black germs in No. 1 unite with the.red germ in No. 2 we get a black animal carrying the factor for red in half its germ-cells. Out of every four calves from this cross we get : — No. 1. No. 2. . No. 3. No. 4. 50 per cent, germ-cells .. Black Black Black Black. 50 per cent, germ-cells . . Black Black Red Red.

If we now cross No. 1 and No. 2 we get pure-blacks, but if we cross No. 2 and No. 3 we get the results again just explained. If we cross Nos. 3 and 4, as already explained, we get one pure-black to two blacks carrying the factor for red in half their germ-cells, and one, the fourth, will be a pure-red. -

From the foregoing it will be seen (d) that before a red calf can appear in a black herd both sire and dam must both carry the factor

for red ; (b) -that if one animal were introduced into a herd which, although itself black, carried the factor for red, it would be possible in time by selection for red to convert the whole herd into a red one.

The only way to make sure of keeping red out of a black herd is as follows : (a.) Before introducing a new bull into a herd try it out with some red or red-and-white cows. If it is a pure-black all the calves will come black. If it carries the factor for red about half the calves will come red. (b.) Watch the results obtained from bulls bred in the herd when used in crossbred herds. If any calves come red it is an indication that the bull carries the red factor. He must have got this either from his sire or dam. If the sire has been proved pure he must have inherited the red factor from the dam, and the dam should therefore be eliminated from the herd, (c.) If a red calf is born in a pure-black herd the sire and dam must both carry the red factor, and both should be eliminated from the herd. :

I have dealt with the red and black factors in cattle at some length merely to give a practical illustration. This example will, • I think, show the 'manner in which all Mendelian inheritance works. The same rules apply to other qualities or factors.

Pollies and horns in cattle are Mendelian factors, the polly quality being dominant and the horn quality recessive. The white face of the Hereford is a dominant factor also. An interesting cross in cattle is a pure Polled Angus with a pure Hereford. We have one parent with a black body and one with a red. Black is dominant, so the progeny will have a black body but carry the red factor in half its germ-cells. Polled quality of the Angus will dominate the horn quality of the Hereford, and the progeny, will be polled but will carry the factor for horns in half its germ-cells. The white fane of the Hereford will dominate the black face of the Angus, and the progeny will have a white face but will carry the factor for black in half its germ-cells. We can predict therefore with certainty that this cross, if the parents are pure, will produce animals with black bodies, white faces, and polled heads, but carrying in half their germ-cells the inheritance of a red body, in half the inheritance for horns, and in half the inheritance for black faces. These factors will, however, be mixed through each other, and the breeding together of these black-polled Herefords will produce most uneven results.

The foregoing deals with qualities that do not mix in the immediate offspring : the one quality dominates the other. A mixture of black and red cattle does not result in a composite colour : the first cross are all black, and the breeding of the progeny together produces either black or red. Mendel’s crossing of long and dwarf peas did not produce any of intermediate length : the first crossing produced progeny all long, and these produced both long and short. There are other qualities, however, that do mix in the progeny, such as we see in the various kinds of crossbred animals that provide the great bulk of the farm-stock of this or any other country. Recent inquiries point in the direction of Mendelian rules governing this.class of inheritance also when the crossbred animals are bred together.

An experiment was made of crossing a Gold-pencilled Hamburgh cock and a Silver Sebright bantam hen. These two differ greatly in size. The Hamburgh is, roughly, twice' as heavy as the Silver Sebright.

The first-cross birds were of intermediate size — in fact; they showed the blended inheritance most breeders would expect. When, however, a further generation of over two hundred birds was raised from these crossbreds it was found that this consisted of all sorts of size, ranging from birds smaller than the Sebright to birds larger than the Hamburgh. Moreover, it was found that the small birds bred true to size at once, and there is evidence that strains of mediate and of large size could also be established without difficulty.

BREEDING TRUE.

The last paragraph raises important questions to the stud breeder. It goes to show that although in the crossing of animals we often get progeny which to all outward appearance are of blended inheritance, this blended inheritance does not apply to the egg or germcells. The germ-cells in these crossbred animals contain a mixture of unit characters derived from their ancestry, but these unit characters are not blended is pure in itself. In breeding these crossbred animals together there can be no fixed type in the progeny, as it is just a matter of chance which unit characters come together to form the new animal. I think this explains the reason why stockmen who breed crossbreds find from experience that to get good results they must use a pure sire. The prepotency of a good purebred sire dominates the mixed inheritance of a crossbred dam, and at the same time the progeny gets the advantage of the increased vitality and vigour that seems to come from an outcross.

If we get the results stated in the last paragraph when different breeds are crossed, -shall we not also get something of a similar nature, although less in degree, when different strains or types within the same breed are crossed ? If this is true, then stud breeders must always bear this in mind when mating their animals. The object of stud breeding is not only to breed animals as near perfection as possible, but also to produce animals that will, when mated with similar animals, produce animals of similar type and quality ; in other words, they must breed true. If the breeder produces fine animals, but they do not breed true, then he is a failure. Now, every stud breeder will have some ideal in his mind to aim at, and he will be constantly trying to bring his flock or his herd, or. a large proportion of it, nearer his ideal. In doing this he can proceed in two ways : he can use sires of type and ancestry as near to his ideal as he can get them, or he can select sires specially with a view to correcting some weakness in his own animals — that is, if he thinks his own animals have gone to an extreme in one direction he can try and correct this by using sires that go to an extreme in the opposite direction. ■ .

Now, it seems to me that the first method is right and the second method wrong. The second method might get quicker results as far as the outward appearance of the animals is concerned, but it will not produce animals that will breed true. Let us take an example. Suppose a stud-sheep breeder thinks that his flock, or a portion of it, has become too coarse in the wool, and he wants. to get it finer. Suppose he thinks he will attain his ideal quickest by selecting a sire finer in the wool than his ideal, but just so much finer that a blended inheritance will produce the wool he has in mind. Let us see the result.

The progeny may be just the sheep the breeder aimed at,. but half their germ-cells will carry the fine-wool factor, and half will carry the coarse-wool factor; and when these are mated they will produce progeny one-fourth with fine wool which, if mated together, will breed true as a fine-woolled strain, one-fourth with coarse wool which mated together will breed true as coarse-woolled strain. The remaining half will be like their parents, having wool of the desired type, but which when bred together will not breed true, but will again break up into onefourth fine, one-fourth coarse, and one-half correct wool but with mixed germ-cells.

Now, suppose that instead of selecting a fine-woolled sire with a view to bringing his wool to his ideal type a breeder selects a sire having wool of his ideal type and coming from stock that all had wool of this type. Call this ram “ Perfection.” The progeny will not in outward appearance be as near the breeder’s ideal as the progeny from the fine-woolled ram ; but let us think of the germ-cells. Each one of the progeny will have half its germ-cells carrying the factor of Perfection, and half carrying the factor for coarse wool. Breed the progeny together, and we have the following mating :• — Ram. Ewe. 50 per cent, germ-cells . . Perfection Perfection. 50 per cent, germ-cells .. Coarse wool Coarse wool.

The result of this cross will be that one-fourth of the progeny will have reached perfection and will breed true ; « one - half will be like their parents —that is, a cross between perfection and coarse wool; and the remaining one-fourth will have reverted to coarse wool, and if bred together will come true to this type.

If instead of breeding the progeny of Perfection and coarse wool together the ewes are bred to another Perfection ram, we have the following combination of germ-cells : — ' • ’ . Ram. Ewe. 1 50 per cent, germ-cells. .. Perfection Perfection. 50 per cent, germ-cells . . Perfection Coarse wool.

The results of this cross will, be that half the progeny will be Perfection and will breed true, the other half will be like the damsthat is, a cross between Perfection and coarse wool.

It seems to me, therefore, that the only way to- produce a firstclass flock or herd that will breed true is to continually use sires as near the ideal as possible, both in appearance and in ancestry ; and that using sires of one extreme to correct dams of an opposite extreme will lead to disaster, although it may temporarily produce some goodlooking stock. Further, if the good-looking stock bred this way are purchased by other stud breeders the results will disappoint the buyers.

SEX-LINKED INHERITANCE.

There is evidence to show that certain qualities of inheritance are sex-linked — that is, they are only inherited through the male or through the female. Experience goes to show that high fecundity or egg-laying power is linked up with the factor of maleness, so that the highest grade of laying-hen producing eggs, some of - which will hatch into cockerels and others into pullets, transmits the high egg-laying capacity only to her sons and not to her daughters. The high-grade

layers must therefore get this factor from their fathers. This is why such high prices are paid for cockerels from hens with a high eggrecord.

When a “silver” cock is mated.to a “gold” hen these colours follow the regular Mendelian rules, silver being dominant. All the progeny are “ silver,” but carry the “ gold ” inheritance-factor in half their germ-cells. When, however, a “ silver ” hen is mated with a “ gold ” cock the progeny are “ silver ” cocks and “ gold ” hens. This shows still another peculiar difference in male and female inheritance.

Evidence, too, goes to show that milk and butterfat production in dairy cows is inherited more through the male than the female — that is, a high-producing cow transmits her producing-qualities more through her sons than through her daughters. It is becoming more and more recognized by dairymen that to improve their herds or maintain them at a high standard they must use bulls from high-producing dams.

INBREEDING, LINE-BREEDING, AND OUTCROSSING.

The questions of inbreeding, line-breeding, and outcrossing have probably been more discussed and written about than any other aspect in connection with the breeding of purebred stock. It seems to be generally agreed that close inbreeding (a) fixes type, (d) increases prepotency, (c) brings out and intensifies good qualities, (d) brings ' out and intensifies bad qualities, (<?) if long continued, reduces vitality and size and weakens constitution. Outcrossing increases size, vitality, and constitution, but decreases prepotency, and tends to produce unevenness in type. There is always the risk, too, when bringing in an out cross, of introducing a bad quality or weakness that is very difficult to afterwards get rid of. The illustration, given of results in crossing black and red cattle shows how difficult it is to get rid of a hidden red taint. The same principles apply to other qualities.

Line-breeding is the mating of animals not so closely related as the relationships that are looked upon as inbreeding. The principle involved is the same ; the difference is one of degree. The idea behind line-breeding is to.get the advantages of inbreeding, and at the same time to avoid its disadvantages, and also avoid the risks attached to the introduction of an outcross.

Experience and experiments go to show that the loss of vitality, size, and constitution that generally follows continued in - and - in breeding is quickly put right by the introduction of an outcross, and that no animals respond so quickly to the advantages of an outcross as animals that have for some time been closely inbred. The outcross seems in one generation to bring back the size, constitution, and vitality that was lost by continued inbreeding.

The aim of the' stud breeder is to produce the most perfect animals possible, and at the same time animals that will breed true. To breed true the animals must have uniform germ-cells all carrying the same inheritance-factors. This uniformity of germ-cells is gained by close inbreeding. With an outcross there is always the danger of introducing germ-cells carrying the factor for some fault that it may prove afterwards very difficult to eliminate. The problem to be solved is to overcome the loss of size, vigour, and constitution brought about by continued inbreeding, and at the same time avoid or reduce to a

minimum the introduction through an outcross of germ-cells carrying faults.

The foregoing brings up the question of whether the best plan in a stud of considerable size is not to divide the stud into several families, and closely inbreed each within itself until weakness appears ; then introduce a sire from one of the other inbred families, and continue the inbreeding again from his progeny until another outcross is required, when another inbred family can be drawn upon.

What I have said in the last paragraph, of course, only relates to the operations of a stud breeder who. aspires to be a leader in his own particular breed, and who has reached a stage when he considers his stock at least equal to that of any other breeder. The vast majority of breeders are not in this position, and they cannot do better than each select a leading breeder whose stock conforms most closely to the ideal he is aiming at, and in whose breeding methods he has faith, and then go to this breeder whenever he is in need of an outside sire. The breeder who adopts this method will improve his stud much more rapidly and get a more even type than the breeder who goes all over the place for his sires.

The breeders of racehorses and dairy stock have the advantage of seeing the actual performances of the animals they produce. These performances are guide-posts indicating to them whether or not they are keeping on the right lines. Breeders of other classes of stock are more liable to the influences of fads and fancies that often prove to have no sound foundation, and are therefore only of a passing nature. The real breeder with a mind of his own must resist these passing fancies, and must hold closely to the ideal he has in his mind. This ideal must be of a practical nature. The ideal should be to produce the class of animals that will give the greatest return to their users on the class of country and the class of feed they will have to make use of. Like the racehorse and the dairy cow, the test of the quality of all classes of farm-stock must in the last analysis be performance or production. / .

THE QUESTION OF LOCATION.

In establishing a stud the question of location is most important. Animals can be changed in a few generations by environment. They quickly adapt themselves to new conditions. It is important that any changes in the stock caused by their location should be in the direction of strengthening and not 'weakening the suitability of the sires bred in the stud for the class of country and the conditions generally that they will have to adapt themselves to when sold. This is one of the reasons why sires bred in colder climates, as a rule, do well. An example of this is the important position that Scotland has now attained in the production of the highest class of stud stock. Another example is the Friesian breed of cattle, now the world's leading dairy breed; it was produced and developed in the cold and bleak plains of north Holland. In the United States, where this breed of cattle has been so successfully transplanted, the leading studs . are in the northern States. To put the matter shortly, the location chosen for the stud should be one where the conditions are such that natural selection will eliminate any individual unable to thrive under the conditions the sires bred in the stud are likely to be placed in when sold.