Development Of Young Stock
( Originally Published 1912 )
An animal's inheritance is complete at the instant of conception. Everything he is to be by virtue of his parentage and ancestry is already implanted. His food, protection or lack of it, training, and everything connected with his subsequent life make up what is spoken of as environment. Many warm and earnest debates have been occasioned by differences in opinion regarding the relative importance of heredity and environment and the transmission of the effects of environment.
The stock-raiser's interest in environment is in two phases : first, its relation to the individual animal, and second, its effect on the offspring of that individual. The second concerns only the raiser of stock to be used for breeding purposes, while the possible influence of environment upon the individual is of immediate interest to every stock owner.
The practical relation of environment to heredity in the development of the individuals will be considered first. It is a common remark that the influence of environment upon farm animals is a deteriorating one; that environment is more powerful than heredity because when extra care and feed are withheld from the young the development that characterized the parents is not secured. In the same line of reasoning heredity is held to be secondary to environment because seeming low-bred animals reach unusual development under favorable opportunities, and the "corn crib cross" is advised as a chief factor in improvement.
No good can come from debating the values of heredity and environment, since each is essential, and any lack in one will curtail the possibilities of the other. Inheritance is main ly a matter of possibilities. The advantage of the good pure-bred over the scrub is chiefly in his greater possibilities. Of course he exhibits the color and external features of his breed, and the peculiar conformation, but any advantage through ability to derive a greater amount of nutriment from a given amount of feed is at best very slight. The chief distinction lies in the fact that the pure-bred, under the direction of his inherent nature, constructs from his feed a body of greater value, and in the additional fact that he can consume a greater amount of feed. The power of greater consumption is a decided advantage even though the degree of efficiency of digestion be the same as in the scrub. A very considerable part of what an animal can consume is required for maintenance and only that amount of food digested in excess of needs of maintenance can be used for gain. Consequently the one that consumes the most can devote a larger total amount to purposes of increase, complete his growth more quickly and effect an economy equal to the cost of maintenance during the extra time required by the scrub. Under a system of low feeding and poor care, the natural environment under which the scrub's ancestors were reared, the improved animal has no opportunity to utilize his inheritance and makes an indifferent showing against his rival that is in his own habitat. Improved environment is an imperative adjunct to improved breeding. Under judicious artificial care and feeding, the artificial environment that surrounded the ancestors of the good pure-bred, opportunity is offered for utilizing inherent possibilities and the result is markedly in favor of the improved individual.
The scrub is the outcome of natural selection to answer requirements of natural environment, and if stock is desired for the purpose of withstanding the adversities of poor feeding and treatment, the scrub will admirably fill the bill. Our breeds of improved stock have been evolved by artificial selection to meet the needs of the artificial methods of rearing and use obtaining in all advanced agricultural sections. Their superiority cannot assert itself in the absence of the accustomed environment, and when we assume the presence of natural conditions or a low order of care then environment does assuredly tend to pull down or hinder the assertion of what artificial selection has built into heredity. To secure maximum returns from well bred animals the feeding and all features of environment must be made as favorable as possible to allow the exercise of the potentialities that have been intensified through generations of careful selection. The well bred animal is the only economical instrument for the person who wishes to realize upon his ability to feed skillfully and intelligently and care for domestic animals. Though feed is not the only factor of environment that must be considered in this connection, it is a principal one and many really meritorious animals prove a disappointment or fail to properly repay their owners because they were expected to perform the impossible and make bricks without straw. Perhaps this injustice is most commonly worked by under feeding, but the wrong kinds of feed are sometimes employed. Housing and exercise are important parts of environment, being allied to feeding in the same sense that they have much to do with nutrition and continued efficiency of digestion and the maintenance of health. On the whole probably more of our registered breeding stock is injured by too close housing than by exposure.
It is also imperative that this opportunity to develop be accorded the progeny of carefully selected parents during their growing days. It is very easy to allow a scarcity of the right kind of feed to continue too long, or to be deluded by the fact that an excess of fattening foods is filling the requirements because the animal is in an attractively fat condition. Often before it is realized, the days in which growth is possible have passed and a reliable knowledge of what was the animal's inheritance is impossible be-cause no test was made of his capacities to respond to the demands which the builders of the ancestry sought to serve. In the future, much more than in the past, buyers of breeding animals of the meat-making breeds will want tangible evidence of the feeding qualities of their purchases such as can only be furnished by a record of feed eaten and gains made. Unusual prices of feeds required for growth sometimes justify a less rapid development than might be desirable, but generous feeding has the practical advantage of putting such indivduals as are to be discarded into their most attractive condition while still retaining the bloom of youth so that they can be disposed of to the best advantage. Referring again to the "corn crib cross," while it is an essential adjunct to heredity and enables the animal fully to utilize its inheritance in yielding maximum returns, it cannot originate any character or implant anything not represented in the inheritance. It must be relied upon as the material for the structure, the plan of which was drafted by the parents. It is only when an animal has been given a good chance to develop what it is supposed to have inherited that its value as a breeder, if a young animal, can be fairly estimated.
Of course there must always be considerable commerce in undeveloped and untested animals that are appraised upon the insight and experienced judgment of the buyers and sellers, but where much depends on an estimate of individual merit, as in selection of sires or additions to a breeding herd, a fair test must be regarded as superior to the best judgment.
To summarize the discussion of this factor in its relation to the individual, it may then be stated that economy of production suggests the furnishing of that environment most favorable to the development of those characteristics the animal is believed to have inherited. If difficulties may arise in so doing, then the best possible environment should govern the selection of the breed in order that heredity and environment may assist rather than combat each other.
It is as an aid to selection that environment is of greatest importance. Selection is based in large part on individuality and unless the environment permits the exercise of the inheritance, estimates of merit will be less trustworthy than is possible. Then some inferior animals will be preserved and some superior ones discarded, and unsuitable environment will drag down instead of build up. It not infrequently occurs that offspring or descendants of animals of note are used as breeders without even having had a chance to come into a high, state of development. In such cases the sole reliance is placed on the pedigree, and though it may be worthy of such entire faith at times, at other times it preserves what should have been rejected, thus misrepresenting the family and disappointing the owners.
The relation of environment to heredity in the development of individuality seems clear. The relation of environment to breeding powers is more difficult of understanding. Breeders sometimes state that this or that animal never had a chance to develop rightly, "but he is well bred and he will breed right." The likelihood of the transmission of the effects of environment is the question that has occasioned more debate and divisions among men of science than has any other topic. Among biologists this question is designated, "The transmission of acquired characters." Just what constitutes an acquired character is hard to state, and much of the debate has been occasioned by a lack of agreement in the premises. The word "acquired" is used as opposed to "inherited," and anything acquired must therefore be the result of environment. It has been asserted that in the strict sense there can be no such thing as an acquired character be-cause the most environment can possibly accomplish is the development of something of which the beginning is already present.* However, from the viewpoint of a practical stockman we will not miss the real value of the matter if we consider the transmission of development acquired as a result of environment.
Does the liberal feeding of the parents render their offspring any more responsive to good treatment than they would otherwise have been? Are the offspring of raced horses possessed of greater ability in the speed line than they would be if their parents were not raced? The supposed inheritance of the ability to perform certain tricks and to display certain habits are often introduced into this discussion but do not vary the principle of the cases here referred to. The transmission of congenital deformities and oddities are also offered as evidence in this connection, but must clearly be rejected because they have no relation to environment. In short, the matter resolves itself into the question, Does the hereditary material reflect the influence of the surroundings of the parents?
If we consider that all animal improvement has been effected under highly artificial environments, we can easily subscribe to the idea that the effect of environment is transmit ted. It is when the attempt is made to give a physiological explanation of the occurrence that skepticism arises. According to the idea, which seems to be the best extant, that heredity is conveyed by tangible chromatin material retained in the reproductive organs, it is impossible to conceive of the actual incorporation within the chromatin of any substance representing the effects of special feeding, exercise, or education. Although biologists are still divided as to the transmission of acquired characters, they all regard chromatin as the chief if not sole vehicle of heredity. They therefore refer every matter to selection and seek to explain apparent transmissions of acquired characters or develop-ment on that basis. Not every instance can be satisfactorily explained by that means, but on the other hand no evidence is forthcoming to fully substantiate the other view. As a consequence a majority of the biologists, when pressed to give their verdict in the matter, have recourse to the Scottish jurors' "not proven."
Although comparatively few scientists approach problems of heredity to study their relation to stock-breeding practices, yet the breeders will find that the opinions of those less practical men are the most useful for explaining the best of what has been and is being accomplished in animal breeding. The denial of transmission of acquired development and the explanation of the effect of environment solely through selection may doubtless seem an extremely rigid adherence to the sufficiency of selection. This course is the only one open, however, to him who would put heredity on a tangible, truly scientific basis. To ignore or belittle selection is to ascribe results to the working of unknown forces and to continue an atmosphere of mystery around heredity that certainly can not achieve any advance in science or in practice.
It will be seen, however, that whether or not we believe in transmission of acquired development, there is no occasion to place a lower estimate upon good environment as in related to improvement. The prin cipal issue can be most satisfactorily discussed as it relates to trotting horses. With them there is no question about the acquiring of an unusual development, and whatever may be said will also apply in consideration of other effects of environment in other animals. The most plausible presentation of claimed facts presented of late years in support of the idea of the inheritance of acquired develop-ment is contained in the articles published by C. L. Red-field, based on his study of trotting horse breeding. He says :
"The theory relates to the inheritance by offspring of the characteristics acquired by parents. I have pointed out that the characters which an animal acquires are those which he develops by exercising them, and consequently that an acquired character does not mean the acquirement of a new character, but the development of a character already in existence. I have, therefore, substituted for `acquired character' the term `acquired development.' I have also pointed out that a development acquired by exercise is in its nature dynamic, hence I have used the term `dynamic development.'
"The next step was that if the dynamic development acquired by the parent is inherited by the offspring, then the amount of. such should be proportional to the amount of the acquirement. This simply means that if the child is to inherit the dynamic development which the parent acquires, then the parent should acquire the development before he begets the child. Or to state the matter in another way, the child cannot inherit anything which the parent acquires after the child is born.
"I then pointed out that dynamic development is acquired by exercise, and as active animals continue to exercise during their whole lives, therefore, old and active animals have acquired more dynamic development than have young or inactive ones. In other words, I argued that the amount of dynamic development which an animal has acquired is a quantity to be determined by considering the age of the animal and the degree of its activity taken together. From this I drew the conclusion that if acquired dynamic development is transmitted from parent to offspring, then those animals which have, by natural inheritance, a fine dynamic quality must be descended from a line of progenitors which were either old or highly developed by special training.
"I have said that I took 1,000 registered stallions alphabetically, from the `Index Digest' of the `Register' and calculated the ages of sires at the time when these registered stallions were foaled. From these I deter-mined that the average time between generations in the male line was 10.43 years, which would give the average age of sires as 9.43 years at the time of service. I then said that, making all reasonable allowances for errors, the average time between generations in the male line might be set down as between to and 11 years, and that this period might be used as a standard in testing the age part of the theory. So far no one claims to have tested the accuracy of my calculation; no one claims that the figures I gave were wrong; and no one has said that these figures cannot properly be used as a standard ; yet if I am to be controverted, one of the first things to be done is to dispute the accuracy of my standard.
"I then took the entire list of 2:10 trotters as an appropriate class of animals to be used in testing the inheritance of dynamic development, and I calculated the ages of their male progenitors for four generations. The number of animals involved was over 5,000 and I gave the average time between generations in the male line for the production of 2:10 trotters as being approximately 14 years. This is an average of nearly 40 per cent over the standard average determined from the `Register,' and my explanation of this remarkable difference was that it indicated the inheritance of acquired dynamic develop-ment. So far no one has disputed the accuracy of my computation and no one has attempted to give any other explanation of such an unusual divergence from the natural order of things. Am I right or am I wrong? If I am wrong will some one please come forward with a better explanation ?"
In the "American Naturalist" the author has made this reply to the foregoing :
"It is noted that in the case of the average horses re-resented by the first thousand in the `Index Digest,' the ages of their immediate sires only were computed, and found to average 9.43 years; whereas in the case of the horses in the 2.10 list all the sires appearing in the first four generations were brought in. Assuming 14 years to be correct for the average time between generations, this carries us back 56 years.
"The first horse that was uniformly successful as a sire. of speed was Hambletonian Io, foaled in 1849. In the sixties this horse's reputation as a sire of speed was established and he did heavy stud service until the time of his death in 1873. This was the real beginning of the trotting breed of horses. During the later years of the life of Hambletonian 10 and subsequent to his death his sons were patronized by owners of well-bred and speedy mares. The more successful of these were retained in service. When the grandsons of Hambletonian Io, with two generations of speed-producing sires back of them and out of selected female ancestry, came into service, it was found that in many instances they sired faster colts than did their sires or grandsire. Only in more recent years were representatives of popular families used for stud purposes in earlier life.
"In view of these facts, I deem it unfair to base a conclusion upon a comparison of two results, one of which (13 years as the average age at time of service of sires in four generations back of horses in the 2:10 list) comes largely from an investigation of the formative period of the breed, while the other (9.43 years as the average age at the time of service of immediate sires of average horses) mainly refers to more recent conditions. If the figures 9.43 and 13 had been derived by similar means their value would be unquestionable. A really fair comparison would demand the same procedure in one case as in the other. Either all sires in the four generations of the thousand horses should be used or else only the immediate sires of those in the 2:10 list.
"Assuming 9.43 to be correct for the average age of the sires when they produced the first thousand horses in the `Index Digest,' I have attempted to secure a similar figure for the immediate sires of the horses in the 2:10 trotting list as published in the `Yearbook,' Vol. 22. The list published in that volume contained 279 horses. In thirty cases the records failed to show the horse's age. In seven cases the age of the sire is not given. This leaves 242 of the 279 horses whose ages are shown.
"Taking 9.43 years as the average age of the sires of average horses and substituting 13 by 9.41 years as the average age of the sires of 2:10 trotting horses, it is evident that the records do not reveal any su periority of the old sire over the younger one."
It seems quite possible and fully reasonable to account for the great accomplishment of breeders of American trotting horses without accepting the idea of transmission of acquired development.
Most fast horses come from parents with speed be-cause our most astute breeders insist on actual performance as a test of individual merit. Sires without low marks are seldom accorded the opportunity of choice mares until their get from mares bred to them earlier have demonstrated their possession of speed. In the natural order of things such a sire must be of considerable age before being used very freely and having many colts, and thus it might seem that age in the sire favors speed in his get. Whichever side of the question a breeder chooses to take his practice will not be seriously changed. In one case he will train his breeding stock as an aid to selection and discard the failures. In the other case the training will be calculated to produce a result transmitted to the progeny. Those not responding to the training will be discarded just the same.
The development of such a quality as early maturity or ease of fattening may likewise be regarded as not attributable to transmission of effects of environment. Such a character being desired, and environment adjusted to develop it, those not showing it are eliminated while those with greatest aptitude in the desired direction are mated and the inheritance made greater in some of the offspring than it was in either parent. The same sort of testing and selection continued for several generations tends to render the inheritance pure to the desired character. It would be out of line with the practices of master breeders as well as scientifically wrong to seek to develop and have transmitted any greater degree of merit in any feature than was inherited, but selection can, by mating two suitable animals, procure for their off-spring a more generous inheritance than was possessed by any individual of earlier existence.
The light esteem placed upon the possibility of trans-mission of the effects of environment should not incline us to in any way lower our appreciation of studied care and intelligent liberal feeding of breeding stock. Whether we think of speed, easy fattening or natural fleshing qualities, we see that it was only under favorable environments that the makers of the breeds and strains were enabled to select from their herds those animals that should be mated for the perpetuation and intensification of the features they sought to impress upon their stock. It is only by continuing the same conditions that we can retain or improve those same features. Those conditions being withdrawn we are forced to rely entirely upon pedigree, which though of the best cannot safely be allowed to overbalance individuality, and good individuality necessitates full chance for development.
It is only when improved animals are subjected to scrub conditions that the pull of environment is downward. The maintenance of a favorable environment in the feed particularly is therefore necessary in order to realize upon the good inheritance of the animals. It is again essential in the selection of the really best individuals from the young produced. If environment is properly related to the purpose sought its pull is upward. To maintain our flocks and herds under an increasingly artificial environment and yet retain in them the vigor and freedom from difficulties of reproduction found in native stock is the duty that falls upon the breeders of today and their successors.