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C U R R I C U L A R RULES
Rules are Guides--Someone has said that rules are made to be
broken and, in a sense, that is true. Rules are necessary guides, but the
unbreakable rule is an obstacle to efficient administration. The more
competent the administration, the less important the rule. I have frequently been arraigned and indicted by the Secretary of our College
for a wanton disregard for rules. My defense has been that, when a
decision involved either the blind observance of a faculty rule or the
advancement of the interests of a student, my conviction was that the
infraction of the rule was warranted. While I do not care to be considered a faculty outlaw, I still stand by that conviction and for the
student.
CONCLUSION
Professional schools of Law, Medicine, Dentistry, and Veterinary
Medicine have their curricula approved by the national association representing each profession. These schools cannot operate without association approval and they must meet stipulated standard requirement established by their respective national organizations. Would it not
be within the province of this Society to exercise some mandatory, or
at least regulatory function relative to the courses of instruction in Animal Production in the colleges of this country?
T E A C H I N G A N I M A L BREEDING
JAY L. LUSH
Iowa State College
At Iowa State College the course in animal breeding is required of
students majoring in animal husbandry or in dairy husbandry. A few
others elect it because they are specially interested in problems of
genetics and breeding. Most of our students are farm-reared or at least
have worked on livestock farms several months. They have had courses
in general zoology, anatomy of farm animals, embryology and genetics
before the come into the animal breeding course. This makes it unnecessary to teach Mendelism, the physical basis of heredity, or the anatomy
and physiology of reproduction. Attention is focussed on the forces
which the breeder may use to change the hereditary-composition of his
herd or breed; i.e. on the dynamic forces of genetics. Most of the students intend that their future vocations shall be closely connected with
livestock production.
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OBJECTIVES OF T H E COURSE
Much of the material is taught for strictly professional purposes to
fit the needs of those who are to become breeders of seedstock themselves. The aim is that they shall learn the effectiveness of each force
or method which they might undertake to use for improving the hereditary composition of an animal population, like a breed or herd, from
generation to generation.
That the student shall understand the principles is the main aim
but enough specific applications are taught to show how much the
success or failure of a procedure may depend on the underlying principles.
Anything which will help students to understand the nature of the
plant and animal world about them and the biological basis of the
morals and ethics and customs of mankind, so far as those have a biological basis, will contribute as much understanding and enjoyment to their
lives as any other part of the training they may get in college. Certain
topics which are a major concern of professional animal breeding will
also help importantly in promoting such an understanding. Where a
sentence here and a paragraph there, in addition to the strictly professional animal husbandry approach, will explain these human or general
aspects of the topic, that is time well spent, although the teacher must
guard against wandering too far into that field. Examples of such topics
are:
(1) the nature of differences between groups, such as breeds,
races, or species; (2) how heredity and environment are both responsible for every characteristic and what is really meant by arguments as
to the relative importance of each; (3) the real importance and dependability of pedigree; and (4) individual variability and the relation of the
individual to his family, breed or race.
HOW
T H E SUBJECT M A T T E R IS A P P R O A C H E D
First we glance back at the road along which our animal breeding
customs came to be what they are. Experience is a dear teacher but
when our ancestors and predecessors have already paid the tuition
fee, we would be fools to overlook any useful lessons which might
be gained by a brief study of what they tried to do and of what success
they had. A student will be in a better position to appraise the probable
soundness or usefulness of the next proposal or panacea if he knows
something of the tl;ings which have been tried in the past and of the beliefs of breeders when they tried those things. It is easy to spend too
much time on this, especially if the teacher finds it interesting himself.
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The data of the past were incompletely recorded in the first place, only
fragments of those records are preserved (particularly in the case of
efforts which failed), and often there are several possible explanations
for the success or failure of each procedure. *
The second main subject is the connection between what the students
learned in genetics and what they will see in their barnyards and pastures. They have learned about genes and chromosomes, dominance,
linkage, crossing-over, germ-cells, etc. Before them they see animals
and variability. That variability is not evenly spread out in all directions
but is bunched and clumped irregularly in families, races, breeds, etc.,
overlapping in some characteristics but discontinuous in others. A fairly
clear understanding of the genetic basis of variability seems indispensable
if the student is to understand the relative importance of heredity
and environment, or is to get a clear picture of how race and breed and
family differences can be real things, even though the individuals in those
groups may overlap in every characteristic.
The third main topic is selection, - - that tool in which animal breeders
generally place most of their faith - - too often it is the only tool they
use. Selection is studied first on the basis of individual merit as it might
be practiced in a population where pedigrees were unknown. The
aim is to explain what selection may be expected to do and to give some
notion of the rate at which it may be expected to change a population.
Especially stressed are ways of overcoming the circumstances or obstacles which may make progress by selection slow or impossible. Chief
among those aids to selection are: the use of repeated observations or lifetime averages, where those are appropriate; and letting the merits of
an animal's relatives and progeny help sway the decision as to whether
it shall be kept or culled. Such things as the usefulness of the show ring,
the relation between type and production, and the pros and cons of
selective registration, naturally are discussed here as special aspects of
individual selection as a means of changing an animal population.
* Books written in (or concerning the events of) pre,Darwinian days or before
our present herdbook system became well established are especially interesting
to the teacher, since he is apt already to have some general familiarity with
what is in current textbooks. (This may not be true of his students!) Some
widely different ones which have appealed to me in this respect are: Harrison
Fairfax's "Roman Farm Management", Thomas Bates' "History of Improved
Shorthorn Cattle" (actually written by Thomas Bell), A. H. Sanders' "At the
Sign of the Stockyard Inn", and ~ . Engeler's "Die Entwicklung des Herde,
buchwesens unter dem Einfluss der Lehren yon der Vererbung und Zuchtung
bei den landwirtschaftlichen Haustieren".
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The fourth main topic is inbreeding and outbreeding. The aim is that
the student shall learn what things inbreeding or outbreeding will do
well and what they will do poorly or not at all. Chief among these are
the power of inbreeding to form families distinct in all sorts of characteristics, and its almost unique ability to increase homozygosis and
prepotency. Selection and inbreeding are complementary tools in the
breeder's kit because for the most part the things which the one will
do well the other will not do at all. Accordingly considerable time is
spent on linebreeding, which is such a combination of selection and
inbreeding.
More time is spent on inbreeding and its applications than would be
justified by the immediate importance of the topic in the daily run of
situations the average breeder now encounters. I do so deliberately because this is the topic least likely to be learned correctly from the student's own or his neighbors" experiences and because it seems likely that
the future will see many increases in the use of inbreeding and outbreeding. Within the lifetime of many of us, animal breeding seems
almost certain to proceed some distance up the road which hybrid corn
is travelling. Indeed animal breeding found the beginning of that road
first and much of the initial formation of the pure breeds was similar
in principle (although of course vastly milder) to the forming of inbred
lines. The success of those early purebreds as sires on common stock
had much in common with the use of inbred sires in topcrossing as
practiced in corn and had much to do with establishing purebredding
as the conventional method of producing seedstock. After the pure
breeds once became well established we didn't follow that road far in
animal breeding. Perhaps we merely lacked the courage to do that, or
perhaps the nature of our animal material made that biologically or
economically unwise. At any rate the experiment stations are going to
have a look farther up that road in the next few years and I think it
only fair to tell the students something about what appears ahead. Outbreeding is treated briefly as the opposite of inbreeding, its immediate
practical applications coming mainly under the head of crossbreeding
for market animals and outcrossing a strain of purebreds with another
strain in the same breed in order to correct some defect which is
threatening to become too common.
W e pass rather briefly over what the breeder can do by mating like
to like or by mating unlikes, regardless of pedigree. The former is a
powerful tool for scattering the population toward the extremes for the
characteristics on which the choice ~f mates is based. It is not very
effective for anything else. The mating of unlikes is mainly useful for
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decreasing variability in the population as a whole and for holding the
population near the goal if that goal is an intermediate dimension or combination of characteristics. A major goal in teaching this topic is to make
the distinction between what selection will do and what mating like to
like will do. Most of what the students have read and heard praising
the practice of mating like to like has really meant nothing but selection;
--that is saving for breeding purposes the "best" males and the "best"
females, culling the rest. Ordinarily no thought is included of what
would happen to the population if the poorest of the females saved for
breeding were mated to the poorest of the males saved, the medium
males to the medium females, etc., as would be the case if the real
results of mating like to like were being considered, as distinct from
the results of selection.
W e pass lightly over the physiology of reproduction, partly because
the students have had that elsewhere and partly because it seems no
more closely connected with the problem of changing the genetic
composition of the population than other physiological topics such as
digestion, metabolism, or disease resistance. Specific therapeutic treat,
ments altering or repairing the physiology of reproduction will doubtless be devised for increasing fertility and will thereby permit the breeder
to practice more intense selection than at present. But those treatments will probably each be specific and require separate instruction.
It does not seem wise to require the undergraduate student to learn
more than a general idea of hormonic control and an appreciation of the
fact that these hormones may interact with each other in complicated
ways.
MAJOR DIFFICULTIES E N C O U N T E R E D
1. To present a quantitative subject fairly and clearly to students not
familiar with the measures of variability and correlation. I would like to
teach the subject quantitatively so that the students would learn just
how much or how little they might expect to gain from a given practice,
rather than to teach them that the practice is a good one or a bad o n e ,
but I have not yet found how to go far in that direction. Eachi year
another detail or two of this is simplified but the problem remains an
acute one. A t present I include only two or three exercises, started in
class and finished outside, intended primarily to give a qualitative idea
of what a "standard deviation" and a "correlation coefficient" are used
to measure.
2. To present fairly what may reasonably be expected per year or per
generation from each breeding method, without chilling the enthusiasm
of those students who may be disposed to expect miracles.
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3. To give the abler students work commensurate with their ability,
without hopelessly confusing the less able ones.
4. To offer constructive substitutes or explanations to replace each
procedure, fallacy, and double meaning which is criticized or explained.
There is a useful place for purely destructive criticism, yet even the
effectiveness of that is enhanced if something constructive can be offered
to replace the concepts being criticized or revised. Certainly the optimism
of the student and his will to work are better maintained thus.
5. To give the students a proper perspective about what items are of
major importance and what are minor details. It is here that examinations are most useful to the teacher in showing him how well or poorly
this is being achieved.
6. To devise problems and assignments simple enough for the students to do in a reasonable time and yet complete enough to make
the principles clear. Even the best problems often leave some of the students "unable to see the forest for the trees".
7. Should more be taught about the financial aspects and vital statistics of the purebred business? I mean such things as: How long does
the average breeder stay in business? W h a t are the major causes of
failure? Are there any dependable general rules concerning prices which
may reasonably be paid for breeding animals which seem to be of
unusual merit? W h a t number of future offspring may be expected from
females of various ages in each species? Etc. Where may one lind
dependable answers to these questions?
8. How much should one stress the aesthetic and sporting satisfactions
which may be derived from stock breeding? That these may be consider,
able is evident from the many rich men who breed purebred livestock
as a hobby, and from the large amount of energy and money spent in
breeding "pet and fancy stock", ranging from dogs and cats to canaries
and goldfish.
9. There simply is not time enough to teach all these things thor,
oughly. ( W e have at Ames about 30 class periods not counting those
used for examinations and holidays). How adjust the time and emphasis
on each topic so that there is the least risk of seriously confusing the
student or of teaching him things less useful than some which are
omitted for lack of time?