Estimation of genetic parameters for body weight traits in squab pigeons

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Estimation of genetic parameters for body weight traits

in squab pigeons

Se Aggrey, Km Cheng

To cite this version:

Original

article

Estimation of

_genetic

_parameters

for

_{body weight}

traits in

_squab

_pigeons

SE

_Aggrey,

KM

_Cheng

University of British Columbia, Department of

Animal

Science,

Avian Genetics

Laboratory, Vancouver,

BC Canada V6T

_lZ4

(Received

27

_{September 1991; accepted}

1st

_September

₁₉₉₂₎

Summary - Seven hundred and two

_squabs

_(young

_pigeons)

from 144

_pairs

of Silver

King

x White

_King

cross _parents were reared

_by

either their

_genetic

or foster _parents.

Heritabilities were estimated for

_{body weight}

at

_{hatch, 3d,}

1

_wk,

2

_wk,

3 wk and 4 wk

(market age)

of age and the values were

_{0.70, 0.23, 0.22, 0.21,}

0.30 and

_{0.57, respectively.}

Genetic correlations among these

body

weight

traits

_ranged

from 0.26 to 0.82.

Heritability

estimates for

_{weekly gains}

were _0.13,

_0.00,

0.12 and 0.05. These estimates indicated that simultaneous

_{genetic improvement}

of

_{body weight}

at the _{different ages would be feasible.} Production

_efficiency

could be increased

_through

selection to

improve

wk 3

_{body weight}

so that

_squabs

could be marketed a week earlier than the current

_practice.

pigeon

/

heritability

/

genetic correlations

_/

_{body weight}

_/

_{weight gain}

Résumé - Estimation des _{paramètres génétiques} pour des caractères de poids

corporel chez le _pigeonneau. Un total de 702

pigeonneaux

obtenus à

_partir

de croisements entre

_1/4

_couples

Silver

King

et White

_King

ont été élevés par leurs parents

génétiques

ou _par des parents

adoptifs.

Les valeurs d’héritabilité ont été estimées pour le

poids

corporel

à

_{différents âges:}

à la naissarece;

3 jours;

1

_semaine;

2 semaines; 3

semaines;

et 4 semaines

_(âge

à la mise sur le

_marché).

Les estimées sont

_{respectivement: 0,70,}

0,23,

0,22, 0,21, 0,30, et 0,57.

Les corrélations

génétiques

entre ces mesures du

_poids

corporel

varient entre 0,26 et 0,82. Les héritabilités estimées _pour les

_gains

de

poids

hebdomadaires sont 0,13,

0,00,

0,12 et

_{0, 05.}

Ces résultats

indiquent

que des améliorations

génétiques

simultanées du

_{poids corporel}

à

_{difJ’érents âges}

sont

_possibles.

Une

_augmentation

de

_{l’efficacité}

de

_{production pourrait}

être obtenue _par sélection

_afin

d’améliorer le

_poids

corporel

à 3

_semaines,

ce

_{qui permettrait}

de diminuer d’une semaine

_l’âge

auquel

les

pigeonneaux

peuvent être vendus sur le marché.

pigeonneau

/ héritabilité / corrélation génétique

/ poids corporel

gain

de poids

*

INTRODUCTION

Pigeons

are

_widely

used as

_experimental

models in biomedical research and have also been raised for meat

_production.

Commercial

_squab

_(young

_pigeon)

production

has existed in North America since the

_early

1900s

_(Levi,

_{1974; Stanhope,}

₁₉₇₈₎

and annual

_production

is over one and half million

_squabs

in the United States and Canada

_{(Cheng, 1986).}

Unlike other

_{poultry species,}

_pigeons

form

_pair

bonds

to breed and

_hatchlings

must be brooded and fed

_by

their

_parents

until the market age of 4 wk

(Levi, 1974).

A

pair

of

pigeons

can raise about 15

_squabs

_per year.

Although

meat from

_squabs

is

_{produced commercially,}

information

_regarding

breeding techniques

and advances is

_lacking.

No concentrated effort in selection to

improve

the

_efficiency

of

_production

_(in

terms of the number of

_{squabs produced}

by

a

_breeding

_pair)

has been made since Australia’s

_Squab

Production Tests of the

early

1930s

_{(Dark, 1973).}

Cheng

and Yelland

₍₁₉₈₈₎

_provided

the first

_heritability

estimates for

_{squab body}

weights

at different _ages

_using

variance

components

and

_{regression analysis.}

Their

data

_suggested

that

_parental

and seasonal factors affected

squab

body weight,

but

they

neither corrected their estimates for seasonal and other environmental factors

nor estimated

_genetic

correlations among the traits. In the

_present

_study

(reported

on

_{briefly by}

Aggregy

and

Cheng,

1991),

we used the same

_{pigeon population}

of

Cheng

and Yelland

_(1988).

In an

_attempt

to

_separate

the environmental effect of the

_parents

from the additive

_genetic

_variance,

a

_{cross-fostering}

scheme was carried

out to estimate heritabilities and correlations of

_{body weight}

traits in

_squabs

from

hatch till 4 wk of _age.

MATERIALS AND METHODS

The

_squabs

used in this

_study

were the _progeny of White

_King

_by

Silver

_King

cross

parents.

Such a cross was made in an

_attempt

to

_develop

an

_autosexing

_system

(Cheng, 1986).

Silver and White

_Kings

are 2 strains of the same

_breed,

_differing

in

_only

a few loci that affect

_plumage

colour,

and both have similar

performances

and selection

_policy

under the standards established

_by

The American

_King

Club

(Levi,

1974;

PJ

Marini,

Nicholas

_Breeding

Farms,

Sonoma, CA, USA; personal

communication).

Our

F

2

performance

data can therefore be treated as

providing

estimates of

_purebred

_parameters.

There were 144

_pairs

of breeders. Each

_pair

of breeders were housed in a 61 cm x 61 cm x 46 cm wire cage

provide

with 2 nests.

_They

were fed ad libitum on a commercial

_pelleted

diet

_containing

17%

_protein

and added crushed

_oyster

shells.

Eggs

were taken _away from the

_parents

after a

_complete

clutch

(2 eggs)

was laid and

_replaced

with wooden

_dummy

_{eggs for the}

_parents

to

_complete

incubation.

Eggs

were hatched

_{artificially throughout}

the _year and

_newly

hatched

_squabs

were

placed

either under their own

_parents

or with foster

_parents

at the same

_stage

of incubation. The

_squabs

were

_weighed

at

_hatch,

3

_d,

1

_wk,

2

_wk,

3 wk and 4 wk

post-hatch.

Data on

_progenies

from different clutches of the same

_parents

were used and

Statistical

_analysis

The data were

_{analyzed according}

to the

_following

model:

where

_{Y2!!1&dquo;,,}

is the

_weight

or

_weight

_gain

(g)

of the 7ath progeny in the

_ijklh

_class;

ILis the overall mean; ai is the random effect of the ith

mating

pair;

F!

is the fixed

effect of the

_jth

foster

_parent;

_B

_k

is the fixed effect of the kth

_{clutch; S}

_l

is the

fixed effect of the lth season in which the

_squab

was

_hatched;

_E!!kvm

_is

the random error. Variance

_components

were estimated

_using

the variance

component

procedure

(PROC VARCOMP)

of the SAS Institute

₍₁₉₈₅₎

computer

package.

Heritabilities

(h

2

)

were estimated

_by:

where

_(1!

_is

the between

_matings

variance

_component

and

o

l

is

the

_phenotypic

variance

component.

Progeny

from

_{mating pairs}

are full sibs.

The

between

mating

pair

component

((1!)

includes the variance due to

_genetic

differences in

_{body weight}

or

_{weight gain}

_{among full sibs}

50%

of the additive

_genetic

variance and

25%

of

the dominance

_genetic

_{variance) (Cockerham, 1954).}

In

_addition,

this

_component

includes the variance

_resulting

from the influence of

_{preoviposition}

environment

provided

to the fertilized _egg

_by

the dam. Much of such influence can be

classified

as

_genetic

with

_regard

to the

_dam,

but is classified as environmental from the

standpoint

of the young

squab.

Standard errors

_(SE)

of the

h

2

were

estimated

_by:

as indicated

_by

Becker

_(1984),

where n is the total number of

_individuals;

t is the intraclass

_correlation;

k is the coefficient of the between

_matings

variance

component

and s is the number of

_matings.

Correlations

_(r

_x

_y)

were estimated

_by:

where _r!y is the estimate of

_genetic

or

phenotypic

correlation;

Cov(x, y)

is the

genetic

or

_phenotypic

covariance between traits x and _y, and

var(x)

and

var(y)

are the estimated

_genetic

or

_phenotypic

variances of traits x _{and y,}

_{respectively.}

Standard errors for

_genetic

correlations

(rg)

were calculated

by

an

approximation

where rg is the

genetic

correlation between traits x and y. RESULTS

Morphological techniques

for

_{sexing squabs}

are not reliable so the

body weights

and

_{weight gains reported}

are not differentiated

_by

sex. Overall _means,

phenotypic

standard deviations

_(up)

and

_heritability

estimates of

_body

_weight

and

_weight

_gain

at different ages are

presented

in table 1.

Variability

in

body weight

is !

12%

on

day

of hatch and increases to

32%

at 3 d of _{age, it} then declines

_gradually

to !

11%

at 4 wk of _age.

_Variability

in

_{weight gain during}

the 1st wk is !

28%,

declines to ?

19%

at wk

_2,

and then increases to x5

40%

at wk 3. The

_weight

gain

from 3-4 wk is not

_{significantly}

different from 0. The

heritability

estimates for

_{body weights}

were

_{generally higher}

than estimates for

weight

_gains.

The

genetic

and

phenotypic

correlations estimated from the full sib

_components

of variance for

_{body weights}

and

_{weight gains}

are

presented

in tables II and III

respectively.

Genetic correlations among the

body

weight

traits range from 0.26 to 0.80.

DISCUSSION

The

_{hatching weight}

of

_squabs

was

relatively

constant with a

_{high heritability}

probably

due to the common

_{preovipositional}

maternal variance

(egg size).

The

heritability

estimate for

_{body weight}

at 3 wk was similar to the estimate

_reported

by

Cheng

and Yelland

_(1988).

However

_heritability

estimates for

_body

_weight

at 3

_d,

1

_wk,

and 2 wk of _age were

_{higher (0.23,}

0.22 and 0.21

_compared

to

_0.14,

0.04 and

_0.16),

and estimates for

_body

_weight

at hatch and 4 wk were lower

(0.70

and 0.57

_compared

to 0.74 and

_0.65)

than those calculated

_by

_Cheng

and Yelland

(1988)

using

full sib variance

_components.

_Cheng

and Yelland

₍₁₉₈₈₎

_reported

that

heritabilities estimated

_by

_regression

_(progeny

on

mid-parent)

for

_squab

_weights

to

1 wk were zero but after 1 wk of _{age their values estimated} from

_regression

and from full sib

_components

were similar.

Heritabilities estimated from covariance of full sibs are biased

by

one

quarter

of the dominance variance and the common environmental variance.

_Hatchlings

from

precocial species

such as chickens can be reared

_{independently}

of the

_parents,

but the young of

_pigeons

_(altricial)

are

_dependent

on their

parents,

causing

resemblance of full sibs. The cross

fostering

_experiment

was

_designed

to minimize the bias of the

full sib covariance caused

_by

common nest environment and

_{post-hatch parental}

effects.

_Pigeons

form

_{pair bonds,}

so that

_designing

a

_mating

_system

to

_provide

substantial numbers of half sibs to estimate

_heritability

from the sire

_component

of variance is difficult. It is not

_possible

under the

_present

model to divide the

11!

into

additive

_genetic

_variance,

dominance

_genetic

variance and variance due

to

_{preoviposition}

environment. On the other

_hand,

in broiler

_chicks,

Pinchasov

weight

decreased

_markedly

after hatch and was not

_{significant by}

5 d after

_hatching.

Similarly,

as the age of the

_squab

_increases,

the

_{preovipositional}

maternal effect on

body weight

may become

insignificant compared

to the effect of the

_genotype.

Additive

_genetic

variances associated with

_{body weight}

from 3 d of _age to 2 wk

were

_low,

_indicating

that the _rp between

_{body weight}

traits until 2 wk resulted

primarily

from environmental causes. The

_{parental ability}

to raise

_squabs

for the

first 2 wk is vital.

_{Breeding pigeons}

are more sensitive to environmental

_changes

than chickens

_(Cheng,

_personal

_{observation),}

so disturbances

during

the first 2 wk of

_brooding

should be

kept

to a minimum. Selection to

_{improve parenting traits,}

if these traits are

heritable,

should be

_important

and their

_genetic

correlations with

squab growth

should be examined. After 2 wk of _{age, additive}

_genetic

variance was associated with

_body

_weight

_increases,

_indicating

that after this age the

body

weight

of

_squabs

is influenced

_by

their own

_genotype.

Genetic correlations are

_important

for

_determining

the

_{genetic relationship}

between

_{body weights}

at different _{ages. Estimates of r9} between

_weight

at hatch

and

_weight

at _{ages 2-4 wk} were low and

_suggest

that

_squab

hatch

_weight

is a poor indicator of later

body weight.

As

pointed

out

_by

Abdellatif

_(1989),

hatch

weight

must therefore be considered a _separate trait. The

relatively

high

heritability

for 4 wk

_{body weight,}

low heritabilities for

_weight

at _{other ages, and the low}

or

_negative

_genetic

correlations _among

_{weight gains}

for different

_periods

could indicate that

_squabs

are

_{opportunistic}

_growers

_having

the

_{genetic potential}

to make

compensatory

gains

whenever conditions are favourable.

The

_{relatively higher}

heritabilities of

_{body weights}

late in this trial indicate that

genetic gains

could be made

_through

selection

_{allowing squabs}

to reach market

weight

earlier than 4

_wk,

which would shorten the

_recycling

time for

_parents.

ACKNOWLEDGMENTS

The

_experiment

was funded

_by

a Science Council of British Columbia

_{Operating Grant,}

BCASCC

_Agricultural

Research and

Development Fund,

Nanaimo

Poultry Processors,

and VIM

Squab

Farm. We thank G Yelland for technical assistance and PJ

Marini,

WF Hollander and anonymous reviewers for their

helpful suggestions.

REFERENCES

Abdellatif MA

₍₁₉₈₉₎

Genetic

_study

of

_Dandarawy

chicken: I. Heritabilities and

genetic

correlations of

_{body weight}

and

_weight

_gain.

Genet

Sel

Evol 21,

81-92

Aggrey

SE,

Cheng

KM

₍₁₉₉₁₎

_Heritability

estimates and

_genetic

correlations for

body

weight

traits in

_{squab pigeons.}

Poult Sci

_70,

_{(suppl 1),}

2

Becker WA

₍₁₉₈₄₎

Manual

_{of Quantitative}

Genetics. Academic

_Enterprises,

Pull-man,

Washington,

4th edn

Cheng

K1!I

₍₁₉₈₆₎

UBC search for

_{squab production}

_{efficiency. Country Life}

_(June)

p A6

Cheng

KNl,

Yelland G

₍₁₉₈₈₎

Factors

_affecting

_{squab body weight}

and the number

of

_{squabs produced}

in a _year. In: Proc 18th World’s Poult

_{Congr. Nagoya, Japan,}

Cockerham CC

₍₁₉₅₄₎

An extension of the

_concept

of

_{partitioning hereditary}

variance for

_analysis

of covariance _among relatives when

_epistasis

is

_present.

Genetics

_39,

859-882

Dark J

₍₁₉₇₃₎

There’s room for

improvement

of local table

pigeon.

J Avicult

(Aust)

71, 447-449

Levi VM

₍₁₉₇₄₎

The

_Pigeon.

Levi Publ Co

Inc, Sumter,

SC

Pinchasov Y

₍₁₉₉₁₎

Relationship

between the

_weight

of

_hatching

_{eggs and}

subse-quent

early

performance

of broiler chicks. Br Poult Sci

32,

109-115

Robertson A

₍₁₉₅₉₎

The

_sampling

variance of the

_genetic

correlation coefficients.

Biometrics

15,

569-485

SAS Inst Inc

₍₁₉₈₅₎

SAS User’s Guide: Statistics. SAS Institute

_Inc,

_{Cary, NC,}

version 5 edn