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Well, I have to say I didn't understand how you were going to keep your
web site and articles confidential, but you
certainly have. I must commend you on the idea and implementation.
I have been impressed by some, not all by any means, but some of the
articles and information on your site. I have been breeding for
many years and felt I would like to share my opinion on inbreeding with
and through your site, others. It may be a little hard for some
to swallow, but it is a summary of all of my years of breeding, inbreeding,
reading and showing. I know that there are many who feel that
inbreeding has achieved a very negative image, despite its value.
this article will make people think about their perception of inbreeding
and spur people to provide answers to numerous questions that I have never
answered to my satisfaction. Please accept the attached article.
Different experts and authorities provide highly variable opinions on
inbreeding and linebreeding. I have always found it impossible to
take many of these people seriously. Unfortunately, my experience has revealed
that few people have the innate curiosity that drives them to find out
how things actually work. Inbreeding or linebreeding is not a mathematical
pursuit or formula, except where it might be used to predict the possibility
of change in a finite, imaginary population, for a quantitative factor
(statistics). It is not, for me, a complex sketch or diagram of related
or unrelated matings. It is not the simple crossing of brother to
sister; cock to daughter or hen to son. It is art. It is feel.
It is at once instinctual and intuitive. It is the compelling observations
that a breeder makes about his stock's behavior and inheritance over many
years. That knowledge and the relatedness of ones birds is so ingrained
in a breeder that he can subconsciously pair the birds that have the greatest
likelihood of producing the offspring he wants.
As I indicate in the body of this document, inbreeding is not memorizing
a standard form and trying to emulate it as so many people try to suggest.
It is not seeking to identify and build on a sport or oddity or at least
rarely, as sports or mutations tend to be discontinuous. The real
inbreeder is driven to develop a bird that exhibits desirable qualities,
that is singularly identifiable, behaves well and is active and responsive.
More than anything else the inbred bird must display all of the characteristics
that the breeder views as critical and desirable. If in his or her
eyes the "new" bird looks good, then it will become a new standard of its
own, and others will come to accept it and want it or reject it out-of-hand.
Inbreeding is the simple and aesthetic act of crossing related stock
to produce the best. This is accomplished by selecting for those transmissible
and desirable properties, that are the province of only a very few outstanding
individuals, and ensuring these traits accumulate within the offspring.
The following position is based on my own observations and reading of
numerous articles, both pro and con, on inbreeding. You may not like
my position, I guarantee you will not like my generalizations and you may
not like my approach and interpretation. If you do not want to read
something that is controversial and intriguing (unfounded to some of you),
you may as well stop now. The anti inbreeder will resent the information
and inferences present here-in. Biologists, Taxonomists and Ornithologists
may find it farcical or erroneous, while Evolutionists may say it is so
general in its sweep of suggestions and questions that it is unworthy of
response or notice. However it is received, I believe the questions
need to be addressed, or the stories of negative long term effects of successful
inbreeding will continue, despite being premised on poor results, excessive
selection, human morality or misunderstandings, as I explain later.
A personal and descriptive visual explanation of inbreeding excess
To describe excessive species selection in an understandable way, I
like to think of an upside down triangle, where the triangle is comprised
of a series of minute horizontal lines, much like pixel density, which
generates a digital image. Each horizontal line comprises a single variety
or breed (one line per breed or variety).
Varieties continue to be distilled, from a diminishing gene pool, until
the inverted apex results in a breed that survives or dies based on whatever
genes are eventually left at the end of a long, long selection process.
Is this the denouement of the species, if indeed so much of the germinal
DNA exists above it ?
Even the most adamant anti inbreeder must recognize that selection is
a continuous process in wild species and many of the changes (gentic gain
or loss) which occur will not be noticed, even by the most meticulous observer:
That's life in the wild. Variation enables the species to undergo
slow or rapid alteration or change to enable adaptation to a shifting environment:
thus continuance of the species may be optimized.
Some would suggest that there should be clear or empty lines in a hypothetical
triangle, presented as a solid object, as these clear lines would serve
to represent or explain evolutionary or inbreeding dead ends. I would
contend that the triangle appears solid, despite full recording of inbreeding
and evolutionary dead ends. The number of viable varieties and genetic
permutations far outweighing the encountered or unrealized dead-ends, whether
natural or artificially selected.
All species have a finite number of genes, that is indisputable.
The question is: how many genetic / phenotypic permutations are viable,
given that a theoretical core of genes are essential for vitality, vigor,
fertility, fecundity and longevity ? If we look at a species that
reproduces itself, forms a clear phenotypic presence and has normalized
variation (around the arithmetic mean) within the population, how does
that description differ from a variety or breed ? A heterozygous
individual, as I have come to understand it, merely indicates that a particular
gene has been revealed or expressed through some process, and represents
substantive enough change to warrant notice. Remember, this mutation
is not added, but revealed from the "normal" genotype, suggesting that
the species carries the gene, but that the gene is in a masked, incomplete
or recessive form, waiting to be uncovered or used in a survivalist adaptation.
A wild species or population has (requires) a great deal of potential
variability present within its genetic make-up, and consequently a potential
for numerous spontaneous presentations of discontinuous mutations.
Given that a variety also has a fair amount of variability surrounding
the remaining genetic material, it troubles me when people speak of the
wild species being heterozygous. If it was, there should be spontaneous
presentation of mutations on a weekly or monthly basis, depending on the
population's size. Other than numbers, how does the varietal genotype
differ from the wild stock, and is the wild stock truly heterozygous, or
is it simply homozygous for those traits selected by nature which in turn
masks other genes as in the breed or variety? How do people balance a defined
heterozygous state with continuous variation or variability around a mean,
when that very same variability occurs around a defined homozygous type
? Are we becoming too general with our use and application of heterozygous
versus dominant types / species definitions and usage? If there
is considerable variation from and around the population mean, which represents
the recognized physical type, don't heterozygosity and homozygosity begin
to overlap in meaning ? Where does heterozygosity end and where does
homozygosity begin? Is a multigenic mutation heterozygous or homozygous
for the traits? Are you becoming confused ? I am.
Given that each line in the triangle represents a variety or selection,
there is obviously a transmittal of genes, both good and bad, among each
variety trending away from the species type. After all, in lovebirds,
we only really look at the color mutation aspect, although a few breeders
may be seeking size, girth or something else. In the majority of
cases many of the factors we seek as breeders are not continuous. This
means that the breeder may not be able to achieve a certain color
blend or expression, despite the fact that we have seen many color selections
and mutations in Budgerigars and Canaries. It is the discontinuous
events like structural mutations that breeders can work with and intensify
among the offspring over time. These mutants are essentially sports
exhibiting some small change in form. Identification and breeding success
(repeatability or improvement) depends upon the breeder's awareness of,
or recognition of slight changes in offspring in his own aviary population.
Compassion & Breeding
Compassion is not something that the successful inbreeder or line breeder
can afford and it may well be why so many inbreeders are despised by those
who would effect to save every bird. Furthermore, we repeatedly hear
that breeders are selecting based on individual traits versus the population
average. This may or may not be true, although I would tend to believe
it: Breeding best to best is not a good maxim unless the breeder
applies it properly. I think most long-time breeders would admit
that there is always a reversion to type (to the average shape and size
of the population being selected), and that even following what we call
homozygosity (prepotency) in the desired bird, there will still be significant
variation within the population's offspring: not variation to the extent
experienced in a large population, but individuality and variance in structure,
color, internal workings, muscle, beak etc... . In other words, even
homozygous birds exhibit variability around the select "type", just as
variation in wild type offspring occurs around the species "type" as discussed
in previous paragraphs.
Failure to assess your stock, and merely selecting the best looking
bird is a sure way to run into the problems encountered by most novice
or curious inbreeders. The inbreeder needs to work with the population
average. If a good looking individual does indeed prove himself,
by all means mate him to your best hens, but if he fails in passing on
his traits, replace him with a better bird (a bird that might not look
as good, but passes on real benefit to the stock). Every breeder
wants to rush to the finish, but ensuring your birds are prolific, fertile
and active is critical to running the race. Checking the mean population
improvement, instead of basing everything on the outstanding individual
whose reproductive vitality may be less than desirable, will help to prevent
the serious breeder from getting to far ahead of the process and heading
full speed into a dead end.
Finally, I agree with many things said on this site, including the one
that says it is a simple matter to for those opposed to inbreeding to make
general, sweeping comments about the negative side of inbreeding or ignore
it. Unfortunately, it is impossible to dispel these perceptions when
no one wants to discuss or educate others about the process and its pros,
cons and myths.
Hybridism - a problem among species ?
While I understand the conservation and purity question surrounding
this issue, I often have to wonder why we get so upset by the possibility
of species crossing. If species cannot cross, as has been stated
on this site many times, there should be no offspring and no fear of pollution
of the gene pool. Therefore, the only concern that can arise is one
of fertility among hybrid offspring; either with parental populations or
between each other. If hybrid offspring are fertile, either with
one or other of the parental populations or with each other, there must
be some undefined relationship between the "species". If crossing
can occur with little trouble and both sexes are fertile, can we really
continue to identify the parent populations as separate species, and if
we do, are we only basing speciation on phenotypes versus genotypes?
Improved DNA understanding and analysis would suggest we are burying our
heads in the sand on this issue and holding to outdated tenants, despite
information or results that point to the opposite of what has been and
continues to be taught: Why?
Each gene or set of genes which can be transferred from a different
"species", may enable significant new combinations to occur, within
complementary and viable genomes, regardless of our taxonomic designations.
Given the enormity and potential associated with the number of gene interactions
and exchanges available through natural pairing or artificial insemination
(A.I.), there should be no surprise that breeders run into a number of
dead ends, whether working with hybrids or strains. Usually, failed
seminal varieties, hybrids or breeds are selected, not by genes and performance,
but by human compassion, which is thrown into the selection criteria.
Animals that would not survive in nature, are not only saved and nurtured
by people, but are encouraged to breed, thereby passing on undesirable
gene combinations that can lead to the very problems everyone tries to
avoid or attribute to inbreeding. I don't want to say inbreeders
don't have compassion for they do, but they are usually running a business
that parallels the livestock industry. The selection and intensification
of blood in a line or hybrid is done because there is an undeniable and
quantifiable economic benefit perceived at the end of the day, by the breeder,
on top of the joy associated with developing something new.
There are obviously many more cases of natural hybridism being recognized
among different avian populations today, than ever before: one of the primary
reasons people are more frequently including "hybrid zone" potential in
reports. This implies that hybridism is not simply a concept derived
by greedy or unscrupulous inbreeders, but rather a natural event that is
successful or unsuccessful, based on chromosomal similarities and natural
selection. I do not believe any of us would complain to loudly if
a breeder decided to cross their pallid roseicollis with a turquoise roseicollis
or a blue personata with a green personata. Why is this activity
such an acceptable practice, and yet when we look at the word "species"
attached to a group of birds showing the same phenotype in the wild (which
implicitly suggests that chromosomes are dissimilar) any crossing or offspring
production is considered inviable or an aberration. It is neither logical,
scientific sound or pragmatic. Simply put, hybridism wouldn't exist if
it couldn't happen or if nature had not planned for it somehow. The
benefits to species survival, from hybridism, given the need for rapid
change are obvious. Is the concern simply because we are referencing
a known, defined natural form and we have a reluctance to see the form
change or lost.
Artificiality is present in everything we do, from the saving of specific
species at horrendous costs, to the re-introduction of species in the wane.
Choose any example you like, whether whooping crane, swift fox, black footed
ferret, Giant Panda. The focus is invariably on altering the food
ingestion mechanism, the ecological surroundings and other things.
We talk about isolated populations that are inbred and more susceptible
to cold weather fluctuations or some other aberrant climatic phenomena.
Why is this susceptibility considered so significant, the population was
not selected for these swift and aggressive changes. Those that die
were ill-equipped for the sudden change, others ( the variability about
the mean population) were lucky enough to survive. We focus on species
extinction/extirpation and trying to reintroduce them to the wild.
Man has created the selective pressure on these animals as surely as he
has changed the face of the world and perhaps weather phenomena.
It is no surprise that we see wild birds adapting and beginning to forage
successfully in urban jungles rather than a natural one: that is simply
where selection has led. We try to save a species, when we should
be working to stabilize the ecosystem: if we wish to stabilize anything
and prevent the inevitable progression of time and change. Too complex
some would say, but is it any less realistic to think that one can save
a single "natural" species, where the environment and food source that
the species in question was once dependent on has been eliminated by weather
phenomena, catastrophe or climactic spikes? It is the constant variability
around the mean that would seem to ensure survival, not the constancy or
fixation of a recognized form or type. Loss of species will continue:
don't doubt it. It is an historic fact and indisputable. It will
continue, either at a reduced rate or increased rate depending on global
focus. Does hybridization increase the chances of survival for "species"
My position is that hybridism is a positive activity interaction that strengthens
the odds of gene pool survival, regardless of the commonly perceived "type"
that may be universally recognized under prevailing steady state pressures,
continuously applied by natural selection in a relatively slowly fluctuating
environment, and a means to induce rapid change where rapid or catastrophic
environmental changes occur.
The logical meta-question that arises is whether lovebird species named
today may in fact be varieties of a much larger parental population, for
they really appear to represent a homozygous form in their breeding, phenotypic
reproduction and breeding. Are some of the existing lovebird species
actually evolutionary dead ends (without hybridization) because of natural
over specialization (lilianae and swindenaria), which also
threatens species survival in the event of a cataclysmic event ?
Major steps have been made with production in rare species, but swindenaria
is still a relative unknown, while the pure Nyasa tends to die at or during
the molt, except, as I understand it, where a cross with other species
has occurred in the background. Is anyone aware of a mutation or
physiological change in the pure Nyasa that enables the juvenile to pass
through the molt and survive to adulthood? If so, how does one know
the birds are pure? If not, are these species so adapted to their historical
territory that they are incapable of surviving in another environment.
How do adults survive and not offspring, and are offspring that die, the
progeny of hybrid birds?
Pet Peeves and Irritations
I have become very irritated, frustrated and yes, even cynical about
always having to hide my use of certain breeding activities because it
will hurt or bruise the sensitivities of those who simply breed, buy and
sell birds for economic gain, but do not wish to hear, see or be seen to
show interest in anything akin to inbreeding. However, these same people
are completely at home and even complimentary about linebreeding.
The honest practitioner will tell you they do not really know where inbreeding
turns into line breeding or line breeding into inbreeding. It is refreshing
to know that so many who do not practice either breeding method and resent
inbreeding, are so comfortable with line breeding. It baffles me
that people can act in such a contradictory way. In my experience, inbreeding
is the most useful method that we breeders have in the struggle to condense
desirable genes in new types, variants or strains.
If inbreeding gets the job done - the breeder should use it. If
it is the best method to concentrate or intensify desirable bloodline (genes)
- the breeder should use it. If it results in a higher percentage
of defective or deformed chicks, then the breeder should accept that as
the cost for seeking the best in his stock or as a necessary evil in eradicating
lethal or congenital recessives - and use it.
Realize, as many have stated on your site's web pages, that the dirt
(minimal / maximal deformity) rises to the surface with inbreeding and
can be overcome in most cases if managed properly by the breeder.
Inbreeding is the only way to reliably improve your stock, yet the majority
seem to live in fear of it. It is highly unlikely that those reading
this article will not own or have inbred birds present in their stock.
Even going outside your own aviary for an "unrelated bird" of the same
mutation, means that the bird you find will be a close or distant relation
to your own bird. Certain mutations tend to be highly inbred, initially,
so you have acquired / paid for a bird that is most often the result of
inbreeding (mutations tend to be recessive to the wild form and color and
subsequently a relational aspect exists). It is also important to realize
that the discontinuous nature of mutations does not enable the colors to
blend well with the wild type, but instead separate out, based on dominant
/ recessive inheritance.
I might be so bold as to say that hybrid (transmutation) birds are probably
more heterozygous than our own birds because of the need to constantly
outcross to the best in the receptor species, to ensure the retention of
the physical appearance of that species. This is quite interesting,
as it clearly implies that the hybridizer seeks the homozygosity of the
color receptor species. He does not seek a heterozygous genome, but
rather a homozygous genome that enables the hybrid bird to be identified
as a member of the receptor species (see: My
A hybrid species development or evolution tacitly implies the need for
significant hybridizing and inbreeding between the parental generation
or F1s depending on fertility ranges. If begun by only a few pairs,
a successful population will be highly inbred, despite the prolific nature
and expansion of such a seminal group. Is there a weakness or flaw
associated with this process ? Yes, but nature has its own way of changing
and selecting for successful species or varieties, that we are still trying
to discover. Whether you feel this is fanciful, or foolish thinking,
double-speak, devoid of fact and substance or scientific scrutiny, the
questions that ultimately follow are:
Wild or Domesticated Parrots and Stock
How different are (homozygous or prepotent) varieties from the (heterozygous)
wild type ?
If varieties and wild types are identified by external appearance or phenotype,
only small changes can have occurred in the variety - TRUE OR FALSE?
If varieties have only experienced a few gene changes that impact color
and behavior for a different environment (domestication) - how quantitatively
different are they from the wild population ?
What is the difference between varieties, breeds, sub-species, strains
and yes, even the wild population?
If inbred varieties are to succumb to inbreeding depression and loss of
vigor, why is this not also true for sub-species and even the primary population,
although admittedly the same effect would take much longer because of the
larger population - However, even this is premised on a belief that the
wild bird is more heterozygous than the variety - I have read this
in report after report, but have seen no mitrochondrial DNA evidence that
would substantiate a substantive or significant statistical alteration
in DNA chains among wild type species or their sub-species, let alone varieties
or breeds. What level of DNA or genetic change is required
to come to the conclusion that inbreeding leads to a path of eventual destruction
? What time frame are we talking about ?
Most people want to buy the pretty birdie or the colorful parrot in
the pet cage They smile and want their picture taken with a Macaw
or Cockatoo. The children want the pretty budgie to hold still on their
finger while they are photographed with it. What is similar or shared
between all of these birds ? All of them are inbred to some extent.
Some will say it is taming, training, treats and care that make them such
pliant and wonderful pets. Show me one wild parrot that will respond
to strangers the way these "pets" do. They are inbred, it is not
simply handling or TLC, their whole response mechanism and behavior has
been undermined or subverted by treats or other training devices.
Oh, it may be that the birds are not genetically inbred, but these birds
have been selected for docility and lethargy, not for natural fire, aggressiveness,
shyness or vitality. The average bird lover would be shocked by the
difference in behavior and needs of a wild parrot versus a domestic one,
so let's take the blinders off for a moment and see that cage birds are
usually either inbred or behaviorally altered to some degree. It
can be no other way, given the human desire to see or own new or unusual
mutations, crosses or hybrids (non aggressive ones): birds that are calm
The reality is that the pairing population potential in cities or towns
tends to be fairly limited when seeking partners for your bird. If
the bird is a combination color, the chances of inbreeding increase.
Yes, people can go and buy birds from a long way off, but depending on
the extent of breeding and bird availability, the breeder is going to run
into terrific expense and some uncertainty as to the relatedness of purchased
and owned birds. In small populations, inbreeding is inescapable.
It may be a milder form of inbreeding, but inbreeding nonetheless.
Can we really avoid it and do we want to ?
I'll go one step further here and say that inbreeding is a necessary
mechanism for improving stock quality, not simply a good or an alternative
mechanism, but an excellent one for the exhibition breeder. There,
I have said it, inbreeding is good! And let any of you argue who
may. Good inbreeding will produce birds that are at least as good
as the parents and in many cases better. We breeders have been hijacked
by a sense of moral prudishness with our birds, and by those who continue
to advocate against inbreeding while they purchase or demand access to
the results. Those that are not courageous enough to take up the
torch of inbreeding will never attain the ultimate breeding pinnacle, the
desire of every serious breeder: A strain of one's own and a bird
whose conformation, color, vigor and fertility set it apart as a highly
desirable acquisition (there is no escaping the economic compensation that
can accompany a desirable mutation or variety).
There are many who will advocate against inbreeding and state
that they have never inbred their birds. If they have never inbred
their birds, I for one must state that they are not really breeders, but
simply propagators of a mutation or species. How do people who have
never experienced the success and challenges associated with inbreeding
form a knowledgeable position against it ? From reading stories about
fewer eggs, deformed chicks and infertility ?
If, a breeder has never experienced dead-in-shell, infertility, dead
chicks, and either mild or severe congenital defects, I for one cannot
say what he or she has been doing. Inevitably, with many years of
breeding, the breeder will experience these heartbreaks in the nest, over
and over again, despite efforts to outcross his birds. Inbreeding
shortens the time frame for these losses, with correct breeding, and will
reward the breeder with healthier stock and birds that are almost identical
in size, color, and reproductive success. Are their immune systems compromised
by the loss of congenital defect genes, or the unmasking of these lethal
or troublesome recessives. I don't know, but their very existence
is a concern in any stock. How much immunity is lost versus lives
saved because of the extraction of a lethal gene or debilitating congenital
Myth, Fact or Simply Unknown
Agapornids are highly inbred. This statement
is a complete fallacy as far as I have been able to determine. Agapornis
is comprised (taxonomically) of 9 separate and distinct species.
When we compare the parrot world to the dog world, we quickly see how very
far behind we are in breed or varietal development. Parrot owners
and breeders tend to focus on color and not novelty or specialty varieties.
It only takes a moment to look at all of the canary, pigeon and chicken
varieties and breeds that abound as a result of careful or sometimes serendipitous
crossings. The budgerigar fancy has the Australian and English varieties
and the feather-duster (some breeders have tried to stabilize, but as far
as I am aware there has been no luck to date). Feather-dusters die
within weeks of getting their feathers.
The growing fear and concern around inbreeding appears based on decades
of selection and intensive breeding in livestock, canine and feline species.
Breeds and varieties in those species have been established through intensive
inbreeding, careful selection, testing and clear objectives. The
selection has been very important to food production and delivered cost,
and we have all benefited from that work. However, problems have
recently arisen because of the continued use of a single sire in line breeding
and the later realization that the sire carried a lethal or debilitating
recessive, which was never identified or eradicated. Few if any animals
come without these inherent genetic problems. The identification
of these problematic genes has led to a resurgence of fear and concern
around excessive inbreeding and stock viability based on existing lines
of animals and these hidden genes. While the issue and concern is
obviously serious, there are probably enough animals to see the stock clear
of the problem after careful analysis, testing and back crosses to the
clean sire, although I am only guessing at this, and basing it on simple
recessive inheritance mechanisms.
Agapornis are, if anything, in the seminal stages of breed development.
We certainly have color mutations, but will we be challenged to any more
than that until such time as there are a number of inbred lines or a few
sports arise that have aesthetic appeal and can be bred for. Inbreeding
or hybridizing of agapornids in domestication, if premised on the number
of breeds in other species, has not even begun. It has barely scratched
the surface, and like the canary or pigeon fancy has the potential for
numerous breed developments: perhaps like the longfeather, but even this
one not for long if it is simply mixed in randomly with the various lovebird
color mutations and not maintained. Inbreeders and hybridizers should
be able to educate themselves regarding the best processes and mechanisms
to prevent those pitfalls and traps that earlier inbreeders and hybridizers
have fallen into in their specific species. If we cannot learn to
accept advice and direction, and educate ourselves once more, based on
what has transpired elsewhere, we are bound to repeat the loss of life,
congenital aberrations and errors in relationship and methodologies.
Inbreeding leads to smaller nests, lack of vigor and poor immunity.
Another statement that leaves me quite perplexed. I certainly understand
how inbreeding can be perceived as leading to all of the identified problems,
but surely it is not inevitable: in fact, far from it if inbreeding is
practiced properly. We know that inbreeding is a tool that can be
applied successfully to maintain fertility, egg production and health,
while seeking to concentrate the desirable "phenotypic" genes. Inbreeding
cannot create something that is not there, but it can maintain and perhaps
improve certain factors. We have some very well known, established
inbred herds (not parrots) that have been selected for a very long time.
When did inbreeding issues with herd sires develop and was it because of
a change in herd management or inbreeder, or a departure from past practices.
How can a stable inbred herd suddenly run into problems with the utilization
of a herd bull or sire in a linebreeding scheme, where the system has worked
so successfully in the past (PROS AND CONS OF INBREEDING: Copyright Sara
Hartwell 1996, 2001, 2003: (http://www.messybeast.com/inbreed.htm).
The only reasonable answer, where a sire is suddenly found to have a hidden
genetic defect that has been passed on among the herd, is that herd management
has changed. Why does poor immunity have to be a necessary evil of
proper inbreeding. An initial phenotypic separation from the wild
stock, does not imply immune deficiency. After all, if we look at
other species breeds, I would not be surprised to find that those breeds
closest to the original stock lost very little if any immunity, particularly
if the substantive inbreeding changes were in coat color or fertility.
Obviously, color breeding does not require a huge shift towards a homozygous
gene set. Certainly, as breeds splinter further and further from
each other and the foundation stock, the gene pool will shrink, and
there will be more critical issues, but that would seem to be founded on
a question of how many breeds a genome may safely be diversified into.
Given the variety of breeds in a number of species, is it unusual or surprising
that a number of congenital defects exist among a genome and occasionally
come to the surface? Simply put, I do not understand the mathematics
or the conclusion drawn with regard to inevitable deterioration of inbred
stock, unless maintenance is thrown to the wind and additional factors
are pursued in an otherwise established and stable line.
Mathematical formula suggesting greater negative impact from inbreeding
than previously thought. I came across this interesting position
on inbreeding on The Cat Resources Archive (PROS AND CONS OF INBREEDING:
Copyright Sara Hartwell 1996, 2001, 2003: (http://www.messybeast.com/inbreed.htm),
an excellent site on inbreeding in cats, although I do not agree with all
of the inbreeding statements. As I have said in this document, I
ascribe to the understanding that a finite population may indeed be mathematically
assessed for mutational and other inbreeding probabilities. I mention
here, Mr. Roy Silson's Book: "Additive Genes in Evolution and Selection",
which has become my bible on inbreeding computations. Having read
this book, I read the Genomics piece in the Cat Resource Archive with great
interest, as microsatellite homozygosity or internal relatedness of positive
"+" or negative "-" satellite markers may enable one to monitor or physically
assess the extent or degree of inbreeding within wild populations.
Is this a modified phylogenetic mitrochondrial DNA analyses ? At
any rate, Mr. Silson suggests, if I have interpreted it correctly, that
a cousin by cousin mating is potentially the best "distance" mating available
in terms of controlling the Coefficient of Inbreeding, while at the same
time generating the greatest potential for change. If the greatest
variability occurs at a cousin / cousin mating level, it would not
be surprising that there would be as much opportunity for beneficial improvement
at this stage, as there would be for the fixing of detrimental genes,
which could inevitably lead towards inbreeding depression. As with
all inbreeding, the result is highly dependent on the experience and knowledge
of the successful inbreeder. It would be highly unlikely for a novice
inbreeder to escape the high probability for inbreeding depression, where
a lack of knowledge is compounded by excitement and an eagerness to inbreed.
Inbreeding success is subsequently highly correlated to a breeder's knowledge
and skill, and the application of that skill.
Successful breeders, not buyers, have a history of inbreeding success
to emulate. Names such as Davenport; Wreidt; Wright and Armour
conjure a world of opportunity and change grounded in good science, observation
and meticulous record keeping. These names are famous in a variety
of livestock areas as pre-eminent inbreeding or linebreeding supporters.
People who charged hell with a bucket of water and succeeded. Not
only did they succeed in their efforts to develop or improve lines of animals,
but have been recorded as doing such or were confident enough to record
their own experiences, thoughts and opinions. People now question the success
of such activity as the use of an alpha dog, dominant cock or herd bull
as a founding sire for a new line, as inherited defects may only become
apparent after many sire / daughter matings. While this is true,
it is simply another significant element to be aware of in the selection
of your foundation animals. few will say that inbreeding happens
quickly or is a quick goal to an end. Inbreeding is not for novices,
it requires a meticulous recording system, knowledge of your animals inheritance,
fantastic luck, rapid identification of problems, the strength to dispose
of (cull) animals that do not come up to expectation or simply have a weak
constitution or appearance - same approach as Nature, and clear objectives
or strengths you want in your birds: not something that is often followed
in the pursuit of developing exhibition birds. It is also important
to remember that genetic inheritance and phenotype are not analogous.
A fantastic looking bird, may no be prepotent and able to pass on his genes,
where a slightly less appealing bird may be able to pass on all good properties
Does inbreeding reduce the gene pool. I have heard
people repeat this belief many times, and have also read it in breeding
reports. Again, I don't know what the answer is, but I thought I
would provide the following. In my opinion, inbreeding does impact
the gene pool (whether that reduction is significant or not is another
question. Whether genes are lost or masked is another question -
I presume lost, but I don't know). However, is that gene loss necessarily
a bad thing ? In many ways the gene pool is altered within a decade
of capturing wild stock and "acclimating" offspring to domestication.
The original birds will not have changed, but we do know that each new
generation of offspring will usually be "selected" for certain traits,
that the breeder may not consciously know they are selecting for.
What really gets me agitated is the suggestion that a mutational event
or inbreeding of a certain color variety might substantively reduce the
gene pool, and the same is said for hybridization of species. Can
someone please explain this to me in an understandable fashion ?
Supposedly, the hybridizer is wasting time and energy by in breeding or
hybridizing birds, which might otherwise be producing more heterozygous
wild type birds. I am so sorry, but I cannot accept this type of
argument. We have no idea what the percentage of mutational events,
alterations, deaths or congenital defects might be in a wild population.
How can a substantive gene reduction position be drawn ? If it is
a theory, OK, explain the position. Just because we cannot see problems
in the wild, is no reason to suppose that in breeders do something evil,
or are the causal factor in generating new and horrendous congenital diseases,
viruses or illness. these are merely resident within the birds genome
and sometimes become uncovered in the pursuit of certain colors.
I believe that the mutational events and fixing of the mutation by inbreeding
actually helps to identify weaknesses that may be attributed to specific
inheritance or gene patterns, i.e.: blindness in excessive lutino crosses,
where the gene is present or is triggered by some small alteration in the
in breeder's aviary or in an aviary other than the in breeders.
My favorite Peeve :
I have read pros and cons surrounding inbreeding for many years now and
the underlying irony in it all is that the reference to inbreeding always
returns to the wild populations and the fact that inbreeding threatens
the gene pool. That the pursuit of homozygous or prepotent animals
in domestication translates into birds with increased: immune deficiencies;
disease susceptibility; sterility; infertility; deformities and deaths.
What these people seem to fail to realize is that wild populations must
be homozygous or prepotent in order to produce offspring of like kind.
Yes, it may be a heterozygous population, but the outward evidence or phenotype
enables us to spot a bird and say: "That is Agapornis roseicollis roseicollis
and not Agapornis personata". The fact that we can visually
define species, and that they are not all different suggests that selection
has been going on for some time and that the birds we see today are the
result of some form of controlled or selective breeding, over time, that
has led to their outward appearance or type. Those opposed to inbreeding
bring up the likelihood of catastrophic weather events or a plague that
could destroy domestic inbred varieties. Nobody is saying otherwise,
but there is an equally high potential for a lot of wild animals to be
killed in catastrophic natural phenomena. If a bird is developed
for a certain niche, such as exhibition, it would not be a surprise to
see it suffer and die if released in the wild, where food and water were
short, its feather consistency was not in keeping with natural or wild
survival parameters and behavioral response mechanisms were dulled by captivity.
If we extend the timeline out far enough, we hear the fears of those who
believe that in bred varieties are facing annihilation from selection.
If the genome is homozygous enough, inbreeding depression will occur.
However, true this may be, we can only assume that the same thing will
occur in the wild, where "typey" species (homozygous for the characteristics
that we use to define differences and species) will also exhaust their
gene pool, which will in turn lead to extirpation. How long will
this take ? a long, long time if cheetahs and their ability to survive
is any indication. The interesting question is whether inbreeding,
hybridization or splitting and re-joining of "species" is beneficial in
prolonging, delaying or generating new and adaptable species. No
matter how many birds we might believe there to be in the wild, it is important
to remember that "species" are finite populations and the likelihood and
incidence of inbreeding and hybridizing will increase as populations dwindle.
I cannot comment on hybrid to species evolution, but it is
a fascinating concept to consider and when all of the facts are open for
review, it is certainly a persuasive and intriguing position. These
pages are the first place I have seen someone build on and increase the
trickle down effect of such an occurrence.
Maintaining purity of existing studs and wild stock. Many
aviculturalists and I suppose other animal breeders seem to focus on the
purity of wild stock and the necessity for keeping these populations untainted
by other species, varieties or hybrids. Unfortunately, like any "purebred"
animal, the pure breed is going to run into trouble when the inbreeding
coefficient increases as a result of having no unrelated animal with which
to mate. The great irony here is the fact that anti-in breeders will
talk about the necessity for maintaining pure studs and wild populations,
and then go on to talk about the heterozygous nature of wild stock and
its ability to withstand disease, infection and strange weather events
(I have noted this position on your pages as well). My simple
questions: Are we talking about wild heterozygous or homozygous populations
? Can they be both ? Are breeders simply turning to any excuse they
can to prevent in breeding from a purely human moral perspective.
We know that wild populations have been isolated, which has led to inbreeding
and some apparently disastrous results, we still don't know if these populations
will find a way out of their quandary or disappear. We also know that many
species have active hybrid zones and that taxonomists have reviewed relationships
and definitions because of unexplainable occurrences such as two
different species mating and producing fertile offspring with human intervention
(Artificial Insemination): An impossibility based on the strictest definition
of species. Birds are supposed to have evolved from dinosaurs so
is it any surprise that many of the birds we see today may have similar
genetic foundations, particularly those identified as species and sub-species.
How close are those species ? If indeed a simple physical change
in the sex chromosome can lead to incompatibility with birds of the originating
species, but enables fertile crossing with a similarly altered bird, the
only difference is a physical one. The birds are otherwise genetically
similar. A reversal of this same chromosomal aberration in an offspring
of the newly established variety (sub-species ?) enables these reversal
birds in the unique population to cross back into the original or originating
population. Is this a pollution of "other species" genes or simply
a recombining of original genes ?
Mathematics as a mechanism or tool for inbreeding predictions,
while interesting tend to be based on the selection and accuracy of the
inputs. Unfortunately, those formulae that I have seen always seem
to leave out critical elements. The one person and approach that
has given me reason to reconsider the value of a mathematical approach
is Roy G. Silson and his book: "Additive Genes in Evolution and Selection"
. Mr. Silson applied, and continues to apply a unique approach to
genetic inheritance and probability prediction. His thoughts and interpretations
of computerized breeding are absolutely fascinating and challenging to
find fault with. He offers a very simple approach to genetic inheritance
that questions contemporary analysis and complexity. It is interesting
that similar complex mathematical problems, such as spiders and web construction,
were eventually found to be premised on something as simple as the length
of the spider's varying legs, silk and web edge. Could it be that
Mr. Silson has identified one of those most sought after and perhaps relatively
simple keys to genetic determination and inheritance. I am not qualified
to comment on the mathematical process utilized, simple as they may be,
but I can readily see the problems it generates for geneticists and biochemists
that have sought complicated pathways to explain increasingly more complex
inheritance (polygenic, multigenic etc...) If this book does not
make you reflect and question most of those things that you have heard
and learned, I don't know what else will. On another note, I was
pleased to see some of the articles on this site referencing additive genes,
and I firmly believe we are beginning to see more mathematicians
and biometricians starting look at inheritance in this same way.
Inbreeding as the cause of congenital defects. I think
this is absolutely erroneous and not enough can be said to refute this
most common of beliefs. The impact of in breeding and congenital
defects has been, much to my surprise, very well handled in articles by
those on your site. However, I don't think they explain congenital
defects, brought about by other situations, well enough. Birds can
acquire or be impacted by a number of environmental or climatalogical alterations
that can be toxic towards some aspect of egg or embryological development.
The defects are usually obvious in twisted or overgrown beaks, humped backs,
loss of toes, peculiar deformities of the foot, polydactyly, muscle contractions
or other physical or physiological symptoms. Unfortunately, the majority
of these defects are immediately blamed on, or viewed by those opposed
to in breeding, as having been caused by consanguinity. In captive
or caged birds, it is true that some defects are brought to the surface
or exposed by mating close relations. There are, however, numerous
other reasons and causes for problem chicks and structural aberrations,
such as in Alaska, where a number of deformities (beak damage) in numerous
species of birds have been identified and continue to occur. Are
these species all inbred and that is the reason for the outbreak of beak
deformities? Of course not. Something else that we are not
aware of is happening. Deformities can be caused by chemical alterations
or failures in enzymatic pathways, by rapid changes in temperature in the
egg or breeding chamber, problems with the hen's metabolism or mothering
and a number of items or conditions other than in breeding, but in breeding
is the easy one for people to challenge and undermine.
Inbreeding results in more sales to the pet market.
In my opinion this is probably the most unrecognized and under-valued reality
associated with in breeding. Without in breeding there would be fewer birds
and fewer colors available for exhibition or the pet store. I cannot
provide you with a mathematical expectation or probability for mutational
events, but my experience has been that mutational events happen because
the breeder pairs related birds with recessive genes. That gene may
only be unmasked in a small percentage of birds in a family unit.
The realization of the gene's expression (phenotype), expressivity or penetrance
would be highly unlikely, where genes were masked for decades or happened
to be recessive to the wild form and the breeder only practiced out crossing.
The presence of a color mutation might suggest to some that a certain amount
of in breeding had to have occurred, at some stage, in order to enable
the mutation to express itself. To ensure production of a specific
mutation it is implicit in the breeding world that these recessive birds
be mated in back cross or sibling cross. Some will suggest that this
is the worst type of matings that you can do, matings of this type
are an old wives tale and that your best chance of mutational success and
assessment comes from crossing to the heterozygous wild type bird.
Any other form of mating leads to in breeding and the problems associated
with it. Obviously I do not agree with the premise of the reasoning of
such statements and would say that your best option is to seek to combine
the mutational genes once more. This, in turn means that all birds
of a certain (clearly definable) mutation color will, eventually, all be
related. How closely is irrelevant, but certainly for the color gene
transcription component. The birds may not have been able to reproduce
the desired color or achieve the color mutation transfer or fixation without
in breeding. Given this, can we please stop pretending that in breeding
is all bad, or that it is a management tool to be abhorred or repudiated.
Are hybridism and inbreeding essential survival and adaptation mechanisms
? I believe people will eventually come to the irrefutable
conclusion that in breeding and hybridism are survival and adaptation mechanisms,
and that breeders currently dedicated to these specific pursuits are merely
refining, synthesizing or distilling an infinitesimally small percentage
of the variable changes in form or color that our birds are inherently
or genetically capable of. This does not mean that we are breeding
or wasting genes, but perhaps developing birds that may be more responsive
to changes in environment in the future or generating changes or combinations
that certain species may never be called upon to utilize in the wild, given
the evolutionary topography, and climatalogical patterns that have slowly
evolved over the globe. In other words, breeders of mutation or hybrids
are generating physical evidence of birds that could have, but up to this
point have not evolved without human intervention. The greater understanding
we develop around and about our birds genetic potential, diversity and
combinations, the more accurately we will be able to predict the changes
that we can "engineer" through controlled breeding. This knowledge
could be utilized to engineer a bird that could replace a bird species
(given that some of the species members were domesticated) following extirpation
from a climatalogical catastrophe. Extirpation being due to the species
inability to enhance or increase its evolutionary adaptability and survival.
Without species, hybrid and varieties in captivity / domestication, there
will be no opportunity at all to replace lost species, unless one wishes
to discuss and consider cloning (this leads to a problem in sexual reproduction
if the wild bird has not been inbred and undesirable recessives removed.
Inbreeding depression is certainly a reality in this case). This will drive
the ecologists and evolutionary biologists wild, as we are talking about
replacing a natural species, extirpated by a natural event, by a modified,
engineered variety in an ecosystem where other endemic species might evolve
to fill the niches. That the domesticated or captive animals might
introduce different bacteria, viruses or other issues into a natural environment
is almost a given. However, the result of such action, whether replacing
a natural species with a domesticated form of that same species, or displacing
a wild population through captive release is someone else's headache. If
the replacement of wild species by domestic animals is not desirable, particularly
if the wild species is wiped out by a "natural" plague, virus or weather
event, there is really very little left to concern ourselves about regarding
in breeding. However, there remain ethical questions
Inbreeding can be done by anyone. Currently, this is
absolutely incorrect. A novice undertaking this activity without
a mentor or the knowledge of the standard of the bird species they
have is only seeking trouble and building the potential for more horror
stories about the failure of inbreeding. Inbreeding is a challenging
tool that needs to be applied correctly in breeding. Even the knowledgeable
breeder will use these tools with some apprehension and trepidation, because
the results can be highly variably. A good breeder will know his
stock intimately and have a solid, practical evidence and knowledge of
which birds pass on which traits. It is this understanding that is
applied by the determined breeder, to the act of inbreeding. If a
novice wants to undertake this task, I would highly recommend reading everything
that he can get his hands on, particularly earlier books by professional
breeders. He should not contain his reading to birds, but look at
all of the mechanisms utilized for improving animal breeding. Many
of these proven methods are applicable across species.
An example of inbreeding and the many schematic breeding strategies that
are available can be seen on the Sabong
Agapornis lilianae: Here is an excellent example of
confusion around species and potential inbreeding or speciation.
The Nyasa lovebird has always been considered a very "weak" bird outside
its natural habitat. Is the Nyasa in fact so inbred that it can survive
no where else. Is the failure of this species to adapt to changing
circumstances, unlike others of its genus, a hint that the Nyasa did in
fact specialize and hive off from another group, where-upon its immunity
was depressed by inbreeding ,which has led to untold and unexplained deaths
? Is the Nyasa an example of niche over-specialization in the wild
or could it be an example of speciation and inbreeding in the wild ?
Is the swindenaria species the same ? This bird too, apparently,
is also unable to survive outside of its locale and is highly specialized
in its seed dietary requirements. At least we know that hybridization
with the Fischer enabled the Nyasa to breed and survive a little better,
outside its natural environment than it had before hybridization.
Are these birds so well selected by their natural environment that a loss
of genes led to compromised immunity ?