Genetic study of Dandarawy chickens: I. Heritabilities and genetic correlations of body weight and weight gain

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Genetic study of Dandarawy chickens: I. Heritabilities

and genetic correlations of body weight and weight gain

M.A. Abdellatif

To cite this version:

Original

article

Genetic

_study

of

_Dandarawy

chickens: I. Heritabilities

and

_genetic

correlations of

_{body weight}

and

_{weight gain}

M.A. Abdellatif

Faculty

of

_Agriculture,

Animal Production

_Department,

Assiut

_University,

Assiut,

Egypt

(received 4-11-1987, accepted 5-5-1988)

Summary — Heritability

values of

_{body weight}

and

_{weight gain}

at the ages of 1 d, and 4, 8, 12, and 16 wk were estimated from 57 half-sib families of a strain of the

_Egyptian

breed Dandarawy

repre-senting

57 sires, 256 dams, and 1,605

offspring.

Estimates were obtained for both of the sexes separately as well as for the two combined. The estimates of

_heritability

ranged from 0.24 to 0.60 for males and females from sire _components of variance, and 0.03 to 0.37 for males and females from dam _components of variance. There were marked differences between

_heritability

estimates from sire and dam _components of variance and between males and females. The

_heritability

estimates from sire _components were

_{generally higher}

than those from dam _components, which indicated the

importance

of the additive genetic effect and

_possible

sex-linked effects. It was also noticed that the environment had an effect on both

_{body weight}

and

_{weight gain}

which is reflected in

_heritability

esti-mates from one _age to another.

The results showed that there were

_{highly significant}

correlations between body

weights

from 4 to 16 _{wk of age. There} were no correlations between hatch

_weight

and _weights at the other ages. This indicates that it is _possible to consider the hatch _weight as a trait

_completely

_separate from the other traits in _{males, females,} and the sexes combined. The highly significant

genetic

and environ-mental correlations showed that both

_genetic

and environmental factors had the same influences on body

weight

from 4 to 16 _{wk of age. There} were absent estimates of the

_genetic

correlations

espe-cially

with the dam components of variance in males and females. The correlations between

_weight

gains

at different

_periods

showed highly

significant

estimates _up to 12 wk of _{age. These correlations} reflect the

importance

of both

_genetic

and environmental effects on

_{weight gain}

at the different per-iods. Our results indicate that it is

_possible

to select for

_{body weight}

and

_{weight gain}

at an _early

rather than a late _{(16 wk) age} because of the _high correlations between _{the different ages.}

Dandarawy

chicken -

_body

weight - weight gain - heritability - sex-linked effect -

_genetic

correlation

Résumé — Etude

_génétique

de la race

_égyptienne

de

_{poulets Dandarawy :}

1. Héritabilités et

corrélations

génétiques

du

_poids

corporel

et du

gain

de

poids.

Les héritabilités du

_poids

corpo-rel et du

_gain

de _poids aux

_âges

de

_{1 jour,}

4, 8, 12 et 16 semaines ont été estimées à

_partir

de don-nées concernant 57

_pères,

256 mères et 1605 descendants dans une souche de la race Egyptien-ne

_Dandarawy.

Les données ont été analysées

séparément

pour les mâles et les femelles, puis

pour les 2 sexes ensemble. Les héritabilités estimées dans

_chaque

sexe à

_partir

de la _composante

«père"

varient de 0,24 à 0,60; celles estimées à partir de la _composante «mère» varient de 0,03 à

0,37. Les héritabilités déterminées à

_partir

de la _composante

_«père»

sont

_plus

élevées que celles déterminées à

_partir

de la _composante «mère». Ce résultat

_{indique l’importance}

de l’effet

_génétique

Dandarawy.

Les variations des estimations d’un mois à l’autre

_{indiquent l5mportance}

de l’effet de l’environnement sur l’héritabilité du

_{poids corporel}

et du

_gain

de

_poids.

Les résultats

_{indiquent qu’il y}

a des corrélations hautement

significatives

entre le

_{poids corporel}

de 4 à 16 semaines. Aucune corrélation

_{significative n’apparaît}

entre le

_poids

à l’éclosion et les

autres

_poids,

ce

_qui

_permet de dire _{que le}

_poids

à l’éclosion est

_{complètement}

_séparé

des autres

pour les mâles, les femelles et les 2 sexes ensembles. Les

_{significations}

des corrélations montrent

l’importance

des effets

_génétiques

et de l’environnement sur le _{poids corporel} de 4 à 16 semaines

d’âge.

Les valeurs absentes des corrélations

_génétiques

déterminées à

_partir

de la _composante mère chez les mâles et les femelles

_{indiquent l’importance}

des autres effets

_génétiques

_que les effets additifs sur ces estimations. Les corrélations du

_gain

de

_poids

ont été hautement

significa-tives d’une

_période

à

_{I autre jusqu’à}

12 semaines

_{d âge.}

Ces résultats montrent aussi le rôle de l’ef fet

_génétique

et de l’environnement sur le

_gain

de

_poids

d’un

âge

à l’autre. Nos résultats indiquent

la

_possibilité

d’améliorer le

_{poids corporel}

et le

_gain

de

_poids

à un

_{âge plus précoce}

_{par la sélection} car les corrélations sont

_{significatives}

entre les mesures aux différents

_âges.

poulet Dandawary - poids corporel -

gain de

_{polds -}

héritabilité - liaison avec le sexe —

cor-rélation

_génétique

Introduction

Several

_{problems, especially concerning}

nutrition and

disease,

are encountered in

Egypt

when

_attempts

are made to

_{employ foreign}

strains in the field. At the Animal Pro-duction

_Department

of Assiut

_University

efforts have been directed toward

_improving

the

productivity

of an old

_Egyptian

breed named

&dquo;Dandarawy’

which exists in

_Upper

_Egypt.

The

_productivity

of _{this breed ranges from} 110 to 122

_eggs/yr;

the _egg

_weight

_ranges from 40 to 45 g; the age at _{first egg averages} 212 to 218

_days;

and the adult

_body

wt is 1

kg

for females and 1.5-2

_kg

for males

_(Hassan

et

_al.,

1973;

Sharara,

1974;

Abdellatif,

1977).

No

_genetic

information about this strain is now

available,

therefore a

_{genetic study}

of certain

_productive

traits seemed to _{be necessary before any}

_breeding

_programme was

to be undertaken. Thus we

_began

the

_genetic

evaluation of the strain in a series of

stu-dies

_{by estimating}

the

_genetic

_parameters

of various

_productive

traits which would be useful in a

_breeding

_programme.

First,

we will discuss

_heritability

estimates of

_body

weight

and

weight

gain.

The

heritability

estimates of

_body

_weight

and

_{weight gain}

as summarized

by Kinney

(1969) ranged

from 0.35 to

0.54,

which are

_{moderately high,}

whereas Kaatz

₍₁₉₆₇₎

sho-wed that the decrease in

_heritability

estimates at 10 _{wk of age} was due to

_high

environ-mental

_components.

In

_fowls,

for sex-linked traits

_{theory implies}

that estimates of

_heritability

from dam

com-ponents

of variance are

_higher

with males than with

females,

while for sire

_components

of variance the reverse is true

(Thomas

et

aL, 1958;

Abdel-Gawad, 1970;

Bernon &

Chambers,

1985).

On the other

hand,

Siegel

and

_{Essary (1959), Gaffney (1964),}

and Goodman

(1973)

concluded that

_heritability

estimates of

_{body weight}

were

_higher

from the sire

compo-nents of variance than the dam

_components,

but Amer

_(1965),

Marks and

_Siegel

_(1971),

and Vaccaro and Van Vleck

₍₁₉₇₂₎

showed that

_heritability

_{estimated from dam}

In

_Egypt,

in

_Fayoumi

chickens,

several workers estimated the

_heritability

of

_body

weight.

El-Masri

₍₁₉₅₉₎

found that it was

0.02, 0.02,

and 0.11 at 8 _{wk of age from the}

sire, dam,

and sire-dam

_components

of

variance,

respectively.

Abdel-Gawad

(1961)

sho-wed that

_heritability

estimates

_ranged

from 0.10 to 0.79 at 1 d to 12 wk _{of age from the} sire and sire-dam

components

of variance. Amer

₍₁₉₆₅₎

found similar results and added that the environment had an effect on

_heritability

estimates at the

_early

_ages.

Many

workers

_reported

correlations of

_{body weight}

and

_{weight gain}

at different ages

(Marks,

1979;

Chambers

et al., 1981,

1984). Kinney (1969)

summarized those

correla-tions,

which were

_{relatively high}

and

_positive.

Martin et al.

₍₁₉₅₃₎

showed that the

_high

genetic

correlations between

_weights

at

6, 9,

and 12 wk of age were more

_persistent

during

the

_{growth period}

than other correlations

(phenotypic

and

environmental),

and the

genetic

effect did not _{vary from} one _age to

another,

although

environmental effects were

greatly

different from one _age to another. Merritt

₍₁₉₆₆₎

and

_Pym

and Nicholls

₍₁₉₇₉₎

mentioned a

_{high genetic}

correlation between 5 wk and 9 wk

_body

_weight

from the sire-dam

_components

of variance for males and females. Aman and Becker

₍₁₉₈₃₎

found a similar result for 6 wk and 7 wk

_{body weight}

from the sire

_component

of variance. In the

_present

_study

we estimate the correlations between

_{body weight}

and

_weight

gain

at different _ages in

_Dandarawy

chickens to

_verify

the roles of both

_genetic

and envi-ronmental effects from hatch to 16 _{wk of age. These values will}

_help

in

_design

_of

pro-grammes for

improving

both

_{body weight}

and

_weight

_gain

_by

selection at an

_early

_age.

Materials and Methods

Animals

From a

_population

of

_Dandarawy

chickens maintained at the

_poultry

farm of Assiut University, 57 sires and 570 dams

_{(leg banded)}

were

_randomly

mated in different

_breeding

_pens (10

dams/sire)

to

obtain

_pedigreed

chicks. After 2 wk of _egg collection, all hens that

_produced

fewer than 5 _eggs were eliminated; thus we had 256 dams that

produced

more than 5 eggs.

Accordingly,

the number of dams/sire and the number of

_progeny/dam

was different from one

_family

to another. The chicks were

weighed

to the nearest gram and

wing

banded at 1 d.

_They

were brooded on the floor at a constant

temperature

(35°C)

until 8 wk of age, then moved to the

rearing

house

_{(open system).}

They were

fed ad libitum on a commercial ration

containing

18% total

protein

and 2,800

kcaUkg.

The

photope-riod was 24 h

_during

the wk 1 and 10 h afterwards. The chicks were

_weighed

to the nearest gram at 4, 8, 12, and 16 wk of _age. A total !of 1,605 chicks from the different families

completed

their record up to _{16 wk of age.}

Statistical

_procedures

Components

of variance were obtained

_by

nested

_analysis

of variance with

_unequal

numbers of dams and _progeny in each sex

_separately.

The statistical model in this case was :

where

_Y

_ijk

is the record of the k+h progeny of the

_h

_j+

dam mated to the i+hsire; M is the

_population

mean; aiis the effect of the i+hsire;

_f

_i

_jj

is the effect of the

_j+

_h

dam mated to the i+hsire; and

_e

_ijk

the uncontrolled environmental and

_genetic

deviations attributable to the individuals

(Becker, 1975).

where

_Y

_ijkl

is the record of the I+h progeny of the i+hsex of the k+hdam mated to the

j+

h

sire; af is the

population

mean; ai represents the random effect and

_f3j

_k

the fixed effect in this model, and

₉

_¡

_j

_kJ

the uncontrolled environmental and

_genetic

deviations

(Harvey,

1977).

The method for estimating

heritability

was, as indicated by Becker (1975) :

where

₆

₂

is the covariance of _half-sibs;

_a

₂

is the covariance of full-sibs minus the covariance of sire

half sibs;

_a!&dquo;

contains the

remainder

of

the

_genetic

variance and the environmental variance. Standard errors of heritabilities derived from components of variance were determined

according

to

the method of Dickerson

(1960),

which was modified

_by

Becker (1975). The

_heritability

estimates (+

SE)

were calculated for _{males, females,} and the combined sexes for _body

_weight

and

_{weight gain}

from 1 d to 16 _{wk of age.}

The

_genetic

and environmental correlations were estimated

_according

to the

_general

formula of correlations :

after substitution of the

_genetic

and environmental components of the variance so as to determine the

_genetic

and environmental correlations from the sire, dam, and sire-dam _components of

varian-ce and covariance _{(Becker, 1975).}

Results

Table

_{I presents}

the

_{body weight}

and

_{weight gain}

means + SD from 1 d to 16 wk of _age for

_{males, females,}

and the combined sexes. The hatch means in males and females

were

_equal,

but from 4 to 16 _{wk of age,} the male means were 13-20%

_higher

than females for

_body

_weight

and 15-20%

_higher

for

_{weight gain.}

The

_{weight gain}

increased

progressively

from 1 d to 12 wk _{of age, but} the rate of increase was reduced at 16 wk of

age.

The results of the

_analysis

of variance indicate that the mean number of

_progeny/dam

was

_6.1,

the mean number of dams/sire was

_6.8,

and the mean number of

_progeny/sire

was 28.0. The

_{least-squares analysis}

of the differences between

sires, dams,

and the combined sexes are

_presented

in Table II. It was noted in the

analysis

that there were

highly significant

differences between sires from 1 d to 16 wk of age for all the traits

body weight

at 8 _{wk of age and}

_{weight gain}

from 4-8 and 12-16 _{wk of age. The}

diffe-rences between the sexes were

_{highly significant}

for all traits

_except

_{body weight}

at

hat-ching

time.

As for

_heritability

estimates of

_{body weight}

and

_{weight gain}

for

males, females,

and the combined sexes

_{(Table 111),}

differences were observed between

_heritability

estimates

in the sexes from sire and dam

_components

of variance. The estimates

_ranged

from 0.24 to 0.60 for males and females from the sire

_component

of

variance,

and from 0.03 to

0.37 for males and females from the dam

_component

of variance. The

_heritability

The values of

heritability

of the combined sexes before and after elimination of sex

effect showed no

_great

differences for

sire, dam,

and sire-dam

_components

of

variance,

and the estimates had the same trend. The results showed that

heritability

estimates of

weight gain

were not consistent and their values were lower than those of the

_body

weight.

The

_genetic

and environmental correlations of

_{body weight}

are shown in Table IV. It was noticed that the

genetic

correlations between hatch

weight

and

weights

at different ages had low and

negative

values

_compared

with the other estimates. The

_genetic

corre-lations between

body

weights

from 4 to 16 _{wk of age had}

_positive

and

_{highly significant}

values for

males, females,

and the sexes combined estimated from the

_{sire, dam,}

and sire-dam

_components

of

variance,

and for females estimated from the dam

_components

of variance.

_Missing

estimates were due to

_negative

_components

of variance.

The environmental correlations between hatch

_weight

and

_{body weight}

at different ages showed

negative

and small values

_{(Table IV).}

The environmental correlations of

body weight

from 4 to 16 _{wk of age} were

_{highly significant}

and

_positive

for

_males,

females,

and the combined sexes estimated from the

sire, dam,

and sire-dam

compo-nents of variance. These correlations were more

_persistent

than

_genetic

correlations at

the various ages.

The

_genetic

and environmental correlations of

_{weight gain}

at the different

_periods

of

age are

_presented

in Table V. The

_majority

of the

_genetic

correlations between

_weight

gain

from one

_period

to another had

_highly

_significant

and

_positive

correlations for

males,

females,

and the combined sexes estimated from the

sire, dam,

and sire-dam

compo-nents of variance. The

_missing

estimates

_correspond

to the

_negative

variances in the

analysis

of variance.

Environmental correlations of

_{weight gain}

from one

_period

to another had unstable estimates.

_{Highly significant}

and

positive

correlations were noticed

during

the

_periods

of

growth

until 12 _{wk of age for}

males, females,

and the combined sexes estimated from the

sire, dam,

and sire-dam

_components

of variance.

Discussion

The

_significant

differences between sires showed that in our local strain

_Dandarawy,

additive

_genetic

factors had a

_great

effect on

_{body weight}

and

_weight

gain,

and the

signi-ficant differences between dams for the

_majority

of the traits studied _{may also} reflect additive

_genetic

effects. Bernon and Chambers

_{(1985) reported}

similar

_findings.

Heritability

estimates from sire

_components

of variance were

_higher

than those from dam

_components,

_confirming

the

_importance

of additive

effects,

since dam

_components

include more non additive

_genetic

and common environmental effects than sire

compo-nents

_(ignoring

sex-linked

_effects).

_{These results agree} with those mentioned

_{by Siegel}

and

_{Essary (1959); Gaffney (1964);}

Goodman

_(1973);

Becker

_{(1975); Pym}

and Nicholls

(1979);

and Bernon and Chambers

_(1985).

’

Heritability

estimates for males based on dam

_components

of variance were

_higher

increases the numerator of

_heritability

for males but not _{females from the dam} compo-nent of variance. Merritt

₍₁₉₆₆₎

and Becker

_{(1975) reported}

similar

conclusions

for the differences between the sexes estimated from the dam

_components

of variance.

On the other

hand,

in the female progeny the

generally higher

value of the sire

com-ponent

than that of the dam

component

of variance _{may also}

_suggest

that

_part

of the variance is due to _{sex-linked genes.}

Fluctuations of

_heritability

estimates from one month to _{another may show the}

impor-tance of environmental conditions

_during

the

_{growth period}

and their effects on

heritabili-ty values;

Kaatz

₍₁₉₆₇₎

found a similar result.

Comparison

between the estimates in this

_study

and those

_reported

in the literature is difficult because of the differences between our

_population

and the other

populations,

which had a

_history

of selection and

_breeding

_{programmes that did} not exist in our

popu-lation.

Lower estimates of correlations between

_{body weight}

at hatch and

_{body weights}

at

later ages lead to the conclusion that hatch

_weight

had no effect on later

_{body weight,}

and that

_{body weight}

at hatch must be considered as a

_separate

trait.

_Kinney

and Shoff-ner

_{(1965) reported}

a similar result.

Significant

correlations between

_{body weights}

within and across sexes reflect the

importance

of

_genetic

effects on

_body

_{weight during}

the

_{growth period}

from 4 to 16 wk of age. Martin et aL

₍₁₉₅₃₎

indicated the same effect of

_genetic

factors on

_{body weight.}

Genetic effects

_{depend mainly}

on _{the fact that the genes that affected}

_{body weight}

at the different ages were the same and had

_pleiotropic

effects. In

addition,

the

_genetic

correla-tions show that additive

_genetic

effects

_greatly

affect

_body

_{weight during}

the

_growth

per-iod

_(Becker,

1975;

Falconer,

1981).

The absent estimates,

especially

with the dam

com-ponents

of

variance,

indicate the

_importance

of

_genetic

effects other than the additive

genetic

effects on

_body

_weight

_(Becker,

1975;

Pym

and

Nicholls, 1979;

Aman and

Bec-ker,

1983).

The environmental correlations of

_{body weight}

from 4 to 16 wk of _age, which had all the environmental and non additive

_genetic

_effects,

showed more

_persistent

estimates than the

genetic

correlations.

Thus,

this result indicates that the environmental factors

affecting

body weight

were the same and did not vary from

period

to

_period

_during

grow-th.

The

_{higly significant}

correlations indicated the

_possibility

of

_{improving body weight}

_by

selection

at an

_early

_{age. Aman and Becker}

₍₁₉₈₃₎

showed a similar conclusion.

The

_genetic

correlations of

_{weight gain}

at different

_periods

_{of age for}

_{males, females,}

and the combined sexes estimated from the

_{sire, dam,}

and sire-dam

_components

of variance confirm the

_persistence

of the same

_genetic

influences on

_{weight gain}

from one

period

to another. The

highly

significant

correlations

_agreed

with those mentioned

by

Kin-ney

(1969)

for

_{weight gain}

at _{various ages.}

Acknowledgments

I wish to _{express my thanks} to those who

_helped

me

_during

data collection at the

_poultry

farm,

University for his

_help

in

_preparing

the _{computer programmes} for the statistical

_analysis

of the data and to Dr. H.M. Mansour, Animal Production

_{Department, Faculty}

of

_Agriculture,

Ain Shams

Univer-sity for his

_{help during}

the

_analysis

of data by the mixed model.

References

Abdel-Gawad E.M.

(1961)

Genetic and

_phenotypic

_parameters in the

_{Fayoumi breed}

and their rela-tion to the environment

_{through breeding.}

Ph. D. Thesis,

Faculty

of

_Agriculture,

Alexandria

Universi-ty,

Egypt

Abdel-Gawad E.M. (1970)

Heritability

estimates and _{types of gene action of} some economic traits in &dquo;Dokki 4&dquo;. II.

_Heritability

and _types of action on 8 and 12 weeks

_{body weight. Agric.}

Res. Rev. 48, 53-62

Abdellatif M.A. ₍₁₉₇₇₎ Studies on some _productive traits in

_{Dandarawy chickens}

under

_{Upper Egypt}

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