Lectura de Palabras

at

tirot,

ospooially

in tlock I mnch

erldbl to

a lcJtr

lewl

of

ttr.J..n:ninc,

duo to

tbo

cU.lution

offeot ot

1ncl� on!mls at

r::mdal!l tree the

�

c;roup of

"

-

" -_o to­_-

..:s

0 0

6

.. , . , , h

� ��

I 1 1 1 1 J I I 1 1 !:1 � � • - ("- ... In ..:::t

-91-

drop

in selection intensity, until _when

the

_{proportion culled equals}

the

level of barrennes s , the [pins are once '-l{;ain equ.ivclent to

those

obtainable

could the selection be bo.sed _{upon a continuously c;ro.dtK� ted pheno't1JPiC}

sccle,

shO'I'Ji.n::; the s.:1me coefficient of' repec.tabili ty. \"i'i th e. :f�1.rthcr drop in the

intcnsi ty of selection, t.he ccins fo.l.l off o.t ;��renter rc.te \7hich ;3'!'C.dually

diminishes

m th decreasins intensity of selection .

Four critical poi.l'1ts

(

labelled

(., 6, /

and S) are shown in

li'iuroure 1 .

1hese

represent the points through which the plot of exp ected c;ains <. :.::;ain

s

t

selection intensity would pass, could selection _be based on a continuous

scclo of pheno-cypic values,

provid.inG the

ropoa.tability on t.�s sc:.:.le is

::.lso

0.14.

The

d.iscrep.:...:rcics

botueen this hypothetical line end. t!1o .::;rcphs :::;iven i'or flocks I .:.end II

th'..ls

t.;ive an idc:J. of the roduced selection c:fl"iciency t..h.:!.t rcse1lts !'".con the COa.i'SO cL-ssificc.tion of fertility &:l.to. ne-.s�:.rcd on a sc.:.::J.e of Lnbs born. TI1eoe discrepancies nre soon to be �c�tcct d1oncvor

the

pcrcc::'t.:.!..�o

of' o.r:.i:: · .ls to be s�vcd

fer brccclinc

f'c.lls r;i t:1L'1 one of the

bro-::od phenot(rpic cks:cos c!.lld

especi<..:.lly

if t:lis cla.ss is c. Llrc;c one.

Vii th _{respect to the selection of rcpl...co.ce_.tn to enter the} brccd:inc

flock as two-tooths, a cullin.:; rete of �und

40-505-

seeJS npplicc..blc :for quite a wide ra.nce of variutions in lambi.% pcrce!ltace, o.nd the mortc.li

ty

rate of ewes and _laobs

(

_Goot

1 947, Hickey 1960).

_{It is intercs tine to}

note that for this level of selection intensity,

the

e:xpe..;ted c;ains fn>o

s

e

lectio

n

based on one la.r:ibing record

of the

dams, are ne for below

this

Jvpothetical ma.ximw!l in flock n • a.l thOlJBh in f'lock: I tbEO'

mey

differ

by

2-3�

l_ambs bol.'ll per

100

ewes� Hickey

( 1960) baa

demonstrated

the

way in

'ft'hich

the cull.in€;

rate

amongst

young replacements is influenced by the l

e

v

e

l of flock fertill V. !bus in flock II.

a

culling rate of

the orfer

of

-92-

50-60}., c:iJht

bo moro applicable • this

bci.rle

the aroo of tho

eroph

d1ero the

•

ef'N.eacy of et70 soloot.ion.

ohcro a oolootion

intonaH:\V

of th.o order of 1-2, is n<U"C

l:iJ:oJ.y (Goot 1947),

the diffCl"COOon in tho

c.xpC'..;tod 02-ino a:re cp.ito

nar1

COCJporinono of flocks I and II da.':lOnatr�.:tco '£o:.'T'.i111 s

( 196, ) D��.:ccstion

Co.sc

(Graphs

Ib c.nd

ITh) :

Th:i:J �ittw.t:l.on oco otudiod in v:tcr; o:t" t!u:.

possibilicy tlle·t the

predi.cti vo V-.J.uo of tJ10 d:ti?f'orcmc botr�cn ono lc!.cJb end zero L.:'!lbs, ic lot'JOr

t.bc.-'1 the

prodictivo

vu.luc of the dif'f'eronco botroon two lnobs and ono.

�

genetic parameters choson are thoBO

OUC:.,""eSted by

tbo nvorcce p:rodicti.Ye

values

�or tbo tt?o-tooth rooord

presonted in

Table

11.

'lba

differences

bettrJeen the

ezpoctod e:tdft8

fur

tbi.e a:l.tuat1on

o.nd tbo

of case

(a)

_above, are in

geuero.l. , small � in both

flocks.

For f1ock

until a

level of

culling of

70-7� . ia

roo.cbed

thc.t the advazrteco

of the

slichtly � predictive vuluc to1.• ti:dlll".in.:;

ovcreooos tho lot1or prodicti ve

value of bm:Tonness � both

t\�

and ba.rronness

beine;

considered relu.ti w to the

rubooquont porforn.:.ncc

of

sirtle-�

CVJOs. In f"lock II, !>..o-;Dvor,

tb.o crcctost dif'foronce occurs a.t selection

intcnsities

oorrespondinc to the

level of tcr"..t.nnii\S or

hichor.

'lbo dif'fcl"'nea in tius c.::we corresponds to the

di.f'fC.l"COOO bcttJoon tbo tt �UOOS of

0.1 7

end 0.1!� c.:00 ic the .oo.no C.S t!lct

oo�t.li"r'i.rt

in f'look I c.t selection intensitios �teE' than 0.20.

( G-mplw Ic , IIc , Id <.:nd !Id) :

"Jc..!'l"C!!DC.os .�m<l the ooloct:lo� for

tninni.n_,

tno :r:. T"'��lOI" s<.:Jr'lC;J of ,.:;rcphs ;vc boon

rn:-cnontc·,<.l.

;;ro_:,hn

Ic end IIc corrozponu to a �� vrcdict:lvc

effect of a zero

value

for

�·

11rl.s is seen to be

c,roo.tost

in f'.lock I

uhieh h:::::.o c.

hi:_;hor

iooido..'1Cc of barren ot�s end a 1�.i-cr lovol of'

tl.�

�arison

of Graphs o and i indiccto that et loo levels

of cullinG

a

positive "t;,

value is mre

ir:portant

than a

positive �t

value of the &liDO size. In

tlock II this ia true for cnlU� lovels

up

to about 16-17, ,

In document Relación entre el ejecutivo central, sus funciones, y los procesos de lectura y escritura (página 39-42)