Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1920-06-10

esfiRg ReSulfs-Ihe Mar
rowng If Network of Des-
cent by Mating GeneticaHy
+ Related Animals - Experi-
menfs Still Going On.
Orunn. Ne, June s-The tnIIuw.ng
Was ISSUED this afternoon rom the
Office uf Charles D. wunds, dirsc1nr
III tine Maine Agricultural Experi-
meu1 station at the University Of
Maine.
No one problem in connection with
practical hrssding Of domestic live
stock LIE more discussed than the sf-
feet Of Inbreeding upun the urossny
On the one hand II mas been main
tanned that trnreeding LIS the nnst
permcinus and destructive proceed IRE
thai nreener could fnlipw And On
the other hand that wichnur It's DOW
errui AID most Of what ting breeder
mas accomplished could NOT have
oeen otherwise gained and thai II Of
fsrs the chief hope fur future ad-
vance. When the Maine Agricui-ural
Experiment Station began It's animal
nusnaunry investigations II COM
menced study Of the RECORDS of reg
isnered livestock ID determine. # DOS
s1bls- WrIaI was the answer 10 this
problem. II was found that while in
nrnaG tNc WAS rrr1ry1 rS-uc,,cra1 +n,~e
was no accurate measure of what
constitutes Inbreeding and that final
judgment was being formed On the
OASIS of individual INTERPRETATION
without any quauritalive measure of
comparison. Among the first con-
rribuIions of the many from the Sta
ton that have proven of great value
70 the theory as well as the Practice
OF breeding YVES an adequate measure
Of this much talked of and vet vague
SUBJECT The problem had been at
lacked by many investigators but
none Of the published results gave >
reliable measure " the real INTENSITY
OF innreeding. The essential weak
ness was q failure 10 take account Of
the composition IF the Eeneratiof1 u
which the common ancestor Of an in
bred pair belongs.
IN the now GENERALLY accepted
method pruposed by the Maine Sta
ton IN 1918 the basic cuncept of in
breeding is the narrowing of the net
work ri descent as a result of mating
together inuividuals Eeneticailv re
'Hted TO each other. This means that
number Of potentially different
Tn-to-ge-rn lines (''bioud Iines"l
acentratad IT a given individual Is
fewer IN the inbred individual than
IT one not inbred. Or stated posi-
tIweiy. the inbred Individual Possesses
fewer different ancestors IN one or
more generations than the maximum
number possible.
This means that the two factors fnr
exact measure are the amount Of an
uestral reduction ana the rats Of this
reduction. Both Of these demands
are met If one takes as the measure
Of inbreedins the exact shortage Of
ancestral individuals N cnmpRrlsnn
with the maximum number there
might have been.
leading 10 It's exact measurement Is
the question whaT degree Of inDreed-
ing was involved in the production Of
a particular animal Il Is necessary
therefore. 10 start with the individual
and work backward InrD the ances-
try rather than 70 start back IN the
ancestry and work down toward the
individual And this Is the funGa =
mental difference IN the method
pointed 0ur BY the Maine STaLion. An
individual viii have TWO parents and
may have different grandparents.
different great grandparents, &c diff
fereut great great grandparents. and
80 on until IN the twelfth generation
there may theoretically be q total Of
40g6 different unrelated ancestors
But II an individual If Lhe product Of
brother anc sister only half THAI
number Of different ancestors is DOS
sjple That is the ceefficient Of IL
breeding would be represented ny 50
# the brother and sister that were
mated were in turn the offspring Of
brother and sister the coefficient Of
lnbreeding of the individual would be
IS anc If the mating of brother and
sister had begun q generation earlier
and been followed through the three
generations the coefficient Of in
breeding Of the Individual would be
g-.5.
This method of measurement Of in
breeding gives rise TO the practical
rule that IN measuring the degree of
inr1reediug in & pedigree II Is neces-
sa-v 10 regard al different IndivlC-
mails as entirely unrelated until the
contrary is proven by The finding Of
common ancestor While this
seems a truisrn there are apparent
uaradoxes that arise in its actual ap-
pIicariun For instance. the coeff1-
c,eut Of fnbreeding would usually In
crease somewhat in proportion 70
the number Of generations cDnsld-
cred. For il in any generation pre-
cediur the one considered, common
ancestor 10 the father an1 the mother
.-,neared. the number Of possible diff
earer- ancestors becomes progress
sivelv decreased as the generations
a-e followed backward Hence the
coefficieut Of inbreeding al the fourth
generation might be BIB and by fol
lowing backward enough common
sncasturs might appear TO materially
,-,,-.ase the coefficieut. In AL events
81. ,,s@nod is a strictly cumulative
,re for COMBATING a like number Of
generations. From what has proceed
al IL is seen that this coeffIcienf
uo,,,d not give an exact cumulative
e 4ta fn,rrfh generation In