Genetic variability of muscle biological characteristics of young Limousin bulls

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Genetic variability of muscle biological characteristics of

young Limousin bulls

G Renand, C Jurie, J Robelin, B Picard, Y Geay, F Ménissier

To cite this version:

Original

article

Genetic

_variability

of muscle

_biological

characteristics

of

_young

Limousin bulls

G Renand

C Jurie

J Robelin

B Picard

2

Y

_Geay

₂

F

Ménissier

1

Institut national de la recherche

_agronomique,

station de

_génétique

quantitative et

_appliquée,

78352

Jouy-en-Josas cedex, France;

2

Institut

national de la recherche

_agronomique,

laboratoire croissance et métabolisme des

herbivores,

UR croissance

_musculaire,

63122

_{Saint- Genès- Champanelle,}

France

(Received

6

_{May 1994; accepted}

13

_January

₁₉₉₅₎

Summary - Genetic _parameters of 4 muscle

_biological

characteristics

_(protein

to DNA ratio

_(Pro/DNA),

lactate

_{dehydrogenase}

_(LDH)

_activity,

isocitrate

_{dehydrogenase}

_(ICDH)

activity

and the

_proportion

of type I

_{myosin heavy}

chains

_{(MHC I)),}

in the

Semitendi-nosus and the

_{Longissimus thoracis,}

were estimated

simultaneously

with average

daily

gain

(ADG),

480-d final

weight

(FW),

carcass lean and fat contents

_(CL%

and CF%

re-spectively)

in a

sample

of _{young Limousin} bulls tested in station. The data came from 144

animals,

the _progeny of 15 sires. Sire and residual variances and covariances were estimated

using

an

_expectation

maximization restricted maximum likelihood

_(EM-REML)

_procedure

applied

to a multitrait mixed model.

_Heritability

coefficients of

_production

_traits,

ADG,

FW,

CL% and

_CF%,

were

_{0.19, 0.49, 0.39}

and

_{0.43, respectively,}

while

_heritability

coeffi-cients of muscle

characteristics,

Pro/DNA,

LDH,

ICDH and MHC

_I,

were

_{0.11, 0.26,}

1.03

and 0.35

_{respectively,}

in the Semitendinosus muscle and

_{0.29, 0.31,}

0.28 and

_0.41,

respec-tively,

in the

_Longissimus

thoracis muscle. In both

_muscles,

the oxidative

_activity

of the ICDH

appeared

to be

_genetically

associated with the

_proportion

of type I

_myosin

_heavy

chains and

opposed

to the

glycolytic activity

of the LDH. The LDH

_activity

was

clearly

associated with

_higher

muscle-to-fat

_ratio,

while the

opposite relationship

was observed

between that ratio and the ICDH

_activity

or the MHC I

_proportion.

beef cattle

_/

genetic parameter

/

growth

/

carcass

_/

muscle characteristics

Résumé - Variabilité génétique de caractéristiques biologiques du muscle chez des taurillons Limousins. Les

paramètres génétiques de

4

caractéristiques

biologiques -

le

rapport

protéines

/ADN (ProIDNA),

les activités de la lactate

déshydrogénase

(LDH)

et

de l’isocitrate

_{déshydrogénase}

_(ICDH)

et la _proportion en chaînes lourdes de _myosine lente

(MHC I) -

des muscles Semitendinosus et

_{Longissimus thoracis,}

et ceux du

_gain

_moyen

quotidien

(ADG),

du

_{poids vif finaL}

à

_{480 j}

_(FW)

et des teneurs de la carcasse en muscles

et en

_{dépôts adipeux}

_(CL%

and CF%

_{respectivement),}

ont été estimés simultanément à

et résiduelles ont été estimées

_{par la}

méthode du maximum de vraisemblance restreinte,

avec

l’algorithme d’espérance-maximisation, appliquée

à un modèle mixte multicaractère

(EM-REML).

Les

_coefficients

d’héritabilité des variables de

_{production, ADG, FW,}

CL% et

_CF%,

s’élevaient respectivement à _{0,19, 0,49, 0,39} et

_0,43,

tandis que les

coefficients

d’héritabilité des

caractéristiques musculaires,

Pro/DNA,

LDH,

ICDH et MHC

I,

valaient

respectivement 0,11, 0,26,

1,03

et

0,35

dans le muscle Semitendinosus et

_{0,29, 0,31, 0,28}

et

_0,4i

dans le muscle

_Longissimus

thoracis. Dans les

2 muscles,

l’activité o!édative de l’ICDH était

génétiquement

associée à la

_proportion

de

_myosine

lente et

_opposée

à l’activité

glycolytique

du LDH. Cette activité du LDH était

positivement

corrélée avec le _rapport muscles

_/

_{dépôts adipeux,}

alors

_qu’une

relation inverse était observée avec l’activité de

l’ICDH et la

_proportion

de MHC I.

bovin à

_viande

_{/ paramètre génétique}

_{/ croissance}

_{/ carcasse}

_{/ caractéristique}

musculaire

INTRODUCTION

The

_objective

for

_improving

beef traits in most

_production

_systems

is to

simulta-neously

increase the economic

margin

of

producers

and meet the consumers’

re-quirements

relative to meat

_{quality. Among}

the numerous

_components

involved in

the

_{biological efficiency}

of meat

_production,

muscle

_growth

capacity

appears to be determinant whatever the

_species

_(Dickerson,

_1982;

Sellier et

_al,

_1992).

In

_cattle,

a

large

genetic variability

of beef traits has been shown to exist _among breeds as well as within breeds

(Koch

et

al,

1982;

Cundiff et

al, 1986;

Renand et

al,

1992).

Ge-netic

_improvement

can therefore be obtained

_by

the

_appropriate

choice of

_breeding

animals,

since

_heritability

coefficients _average 0.35-0.40 for live

_growth

traits and 0.45-0.50 for carcass

_composition

traits.

In most

selection

programs the

primary

selection criterion is live

growth

rate.

Up

to _now, meat

_quality

has not been included in beef selection _programs since there is no economic incentive for

_improving

it and

_objective

methods of measurement

on a

large

scale are still

_lacking.

However different studies have shown that a

moderate but

_significant

_proportion

of the

_large

individual

_variability

observed for meat

_quality

traits is under

_genetic

control _among or within breeds

_(Koch

et

al,

1982;

Cundiff et

_{al, 1986; Renand,}

_1993).

These results

_suggest

that

_genetic

improvement

could be made as

long

as

potential

sires could be tested and

selected,

although

the estimated

_heritability

coefficients are lower than for

_{production traits,}

0.20-0.30 on _average

_{(Renand, 1993).}

Although

not

_directly

_selected,

meat

_quality

_components

_may

_change

as a

consequence of selection for

production

traits,

as

_long

as

_they

are

_genetically

linked. Therefore definition of selection programs to

_improve

meat

_{production efficiency}

and meat

_quality

_requires

the

_genetic

_variability

of the different

_components

to be estimated

_{simultaneously.}

The

_quality

of the meat to be taken into account are the _{sensory measurements}

related to the

_{color, tenderness,}

flavor and

_juiciness

of the

_{higher priced}

_joints

that

are roasted or broiled. Most of these

quality

_traits,

especially tenderness, originate

characteristics of the muscles before

slaughter,

and more

precisely

to the contractile and metabolic

_types

of muscles

_(Valin,

1988; Ouali,

1991).

Three

_types

of fibers can

be

_{distinguished}

in adult cattle

according

to their contractile

activity

(slow

or

fast)

and their energy metabolism

(aerobic

or

anaerobic):

_type

I or slow oxidative

(SO),

type

IIa or fast

_{oxidative-glycolytic}

(FOG),

and

_type

lib or fast

_glycolytic

(FG).

However _very little is known about the

_{genetic variability}

of these characteristics and their

_relationship

with

production

traits. The

_present

contribution aims at

giving

the first within-breed

_genetic

parameters

of muscle

_biological

characteristics of French Limousin cattle.

MATERIALS AND METHODS

Animals

For

_estimating

the

_{genetic variability}

in the French Limousin

breed,

the progeny

testing

results of sires used

_by

artifical insemination

_(AI)

were used. The selection

program of Limousin AI sires includes a centralized _progeny

testing.

Each _year,

purebred

Limousin cows are

randomly

inseminated with the semen of

potential

young sires and a

_sample

of about 30 male _{progeny per} sire is

gathered

in a

central

testing

station after

_weaning

at 7-8 months of age. The young bull progeny

are distributed in

_contemporary

groups

according

to their birth date and fed a

similar diet with corn

_silage

_adequately

_complemented

and distributed ad

libitum,

up to a constant final

slaughter

age of 16 months.

During

fattening,

cattle are

weighed

monthly.

They

are tested on live

growth

traits and on carcass

_weight

and

conformation.

In

_1991,

a _group of 15

_potential

AI sires was tested on 432 young bull progeny

slaughtered

between 9

_April

and 23

_July.

A

_sub-sample

of these progeny was selected

among the young bulls

slaughtered

between 28

May

and 2

July

to

study

the carcass

composition

and muscle characteristics. It included 144 animals after 3 of them had been eliminated due to

_sanitary

_problems.

The constitution of these

_samples

is

_reported

in table I. In the

_experimental

sub-sample

each sire was

_represented

by

8-10 progeny

(9.6

on

_average).

The

_testing

inseminations were

performed

in

different districts of south-western France with different

management

and climate

conditions,

and so 3 different _groups of

origin

(region

x

_management)

were

_defined,

with 37-68 animals each. The 144

_experimental

animals were born in a 2 month

period

and were distributed in 6 different

_contemporary

_groups, with 20-28 animals

each.

Traits

_analysed

Average

daily gain

(ADG)

during

the 8 months

_{fattening period}

and 480-d live

weight

(FW)

before

leaving

for

_slaughtering

were recorded. Carcass

composition

was estimated

_according

to Robelin and

_Geay

₍₁₉₇₅₎

from the dissection of the llth rib cut. Carcass lean or fat contents were

computed

as the ratio of the estimated

lean or fat

_weights

to the cold carcass

weight.

since

_they

_correspond

to

_{higher priced}

_joints

where sensory

qualities

are

_important.

Measurement methods have been

fully

described

_by

Jurie et

_al,

1994. The

_protein

and DNA contents were measured

(Lowry

et

al, 1951;

Labarca and

_Paigen,

₁₉₈₀₎

and combined into a ratio of

_protein

to DNA

_(Pro/DNA)

as an indirect measure of

protein

synthesis

and

_hypertrophy.

The oxidative metabolism has been

_quantified

by

the measurement of the isocitrate

_{dehydrogenase}

_(ICDH)

_activity

_(Briand

et

_al,

1981).

The anaerobic

_glycolytic

metabolism has been

_quantified

_by

the measurement of the lactate

_{dehydrogenase}

_(LDH)

_activity

_(Ansay,

_1974).

The contractile

_type

has been

_{quantified by}

the

proportion

of

_type

I

_{(slow twitch)}

_{myosin heavy}

chains

(MHC I)

measured

_by

Elisa

_{immunological}

assay

(Picard

et

al,

1994).

Analysis

methods

In addition to the sire effect

_(s!),

the factor of interest to estimate the

_genetic

variability,

the statistical model included both the

_origin

_(O

_i

₎

and the

_contemporary

group

(C

j

)

effects for correction. For each

trait,

the model was as follows:

where _y2!!1 was the record of a trait for a _young bull from the ith _group of

origin,

in the

_jth

contemporary

group and progeny of the kth

sire; O

i

was the fixed effect

of the ith group of

origin;

C

j

was the fixed effect of the

jth

_contemporary

_{group; sk} was the random effect of the kth

sire,

sires

_{being unrelated;}

_ei!k1 was the random

residual.

All traits were

_{analysed simultaneously}

in a

_{multiple-trait}

model. The sire and

residual variances and covariances were estimated

_by

the restricted maximum

likelihood

_(REML)

method

_(Patterson

and

Thompson,

1971),

using

the

_expectation

maximization

_(EM)

_algorithm

_(Dempster

et

_al,

_1977).

_{Taking advantage}

of the fact that all traits had identical

_design

matrices,

a canonical transformation was

used. The estimated

_{(co)variances}

were

classically

combined to

compute

heritability,

genetic

and

phenotypic

correlation coefficients. No exact standard errors of the

genetic

parameters

could be

computed

due to the method used to estimate the

(co)variances.

Roughly, only heritability

coefficients

_higher

than 0.4 could be considered

_significant.

A

_principal

_component

_analysis

has been

_performed

on the

genetic

correlation matrix for each muscle

_including

both

production

traits and

RESULTS AND DISCUSSION

Fixed

effects,

means and

_phenotypic

standard deviations

Among

the fixed effects included in the

_model,

the

_contemporary

_group effect was

significant

on almost all the

_traits,

_{certainly resulting}

from numerous unidentified

environmental effects. The

_origin

_group effects

_appeared

to be

_{significant only}

for live

_growth

traits. When tested in the

_station,

the calves that were reared indoors

in their herd of

_origin

had a lower

_growth

rate

_(—8%)

as

_compared

to

_calves

reared

at

_pasture.

_They

also had a lower carcass fat content

_(—0.5

_percent

_units)

and a

lower

_protein

to DNA ratio

_(—5%)

in both muscles. However these effects were not

significant.

Means,

phenotypic

standard deviations and

_heritability

coefficients are

_reported

in table II. As

_previously

described in

_detail

_by

Jurie et al

₍₁₉₉₄₎

the energy

metabolism was more

_glycolytic

and less

_oxidative,

and the contractile

_type

was

faster in the ST as

_compared

to the LT muscle. The

_{phenotypic variability}

of the

_biological

characteristics measured in both muscles was

_{relatively large,}

with

coefHcients of variation around

20%.

This

_variability

was

larger

than those observed

Heritability

coefficients of live

_growth

traits were within the _range of most of the estimates

_published

in the literature: in _{the lower range for} ADG

_(h

₂

=

0.19)

and in the _upper range for final age

weight

(h

2

= 0.49).

The

_heritability

of carcass

composition traits,

h

2

= 0.38 for lean and

h

2

= 0.43 for fat

_content,

were close to the _average values

_computed

from estimates in the

_literature,

h

2

= 0.44 and

h

2

=

_0.49,

_respectively

_(Renand

et

_al,

_1992).

These estimates showed that the

genetic

variability

in this

_sample

of Limousin young bulls was

_{representative}

of the

genetic

variability generally

observed for similar traits measured on cattle tested in

stations.

Most of the

_biological

muscle characteristics

₍₆

out of

₈₎

_presented

_heritability

coefficients in the _range

h

2

= 0.26 to 0.41.

_However,

2 characteristics measured

on the ST muscle had

_quite

different

_values,

as low as

h

2

= 0.11 for the ratio

protein/DNA

and, surprisingly,

as

high

as 1.03 for ICDH. There _may be _many reasons for these extreme values and the

_relatively

limited size of the

_sample

was

_certainly

the

_major

one.

_Except

for these 2

_{characteristics,}

the

_apparent

genetic

variability

of the

_biological

muscle characteristics was

equivalent

to the

genetic

variability

of live

_growth

traits and therefore

_slightly

inferior to the

_genetic

variability

of carcass

_{composition traits;}

about

30%

of the observed

_variability

of these characteristics

_appeared

to be under control of additive

_genetic

effects. In the literature no similar characteristics could be found for

_comparison.

Andersen et al

(1977)

published

estimates of

_heritability

coefficients of fiber

_{type percentages}

in the

_Longissimus

dorsi of Danish

Red,

or Danish Black and

_White,

or Danish Red

and White cattle. The fibers were

_typed

on

histological

slices stained with Sudan

black

_B,

which is

_particularly

absorbed

_by

the

_lipids

_{predominantly}

associated with red fibers and to a less extent with

_intermediary

fibers. The

_heritability

coefficients

_they

obtained

_averaged

h

2

= 0.29

₂

_(h

= _0.22 to =

0.38)

for fiber

_type

percentages

and diameters. These estimates were

_slightly

lower than the coefficients

estimated for live

_growth

or carcass

_composition

traits

they

found in their

study

(respectively

around

h

2

= 0.42 and =

0.48).

In

sheep, Vigneron

et al

(1986)

found

that the

percentage

of

type

b

_{(type I)}

fibers in the Scutuloauricularis

_{superficialis}

accessorius

_muscle,

a small muscle of the _ear, determined

histoenzymologically,

had a

_{relatively large}

_genetic

component, h

2

=

0.27, 0.46,

and 0.97 in 3 different breeds

(M6rinos

d’Arles,

Berrichon x

_Romanov,

and

ite

de

_France,

_{respectively).}

In

_swine,

no estimate of within-breed

_genetic

_variability

could be found for fiber

_types,

while estimates of fiber diameter

_averaged

h

2

= 0.32 in 2 Danish studies

_{reported by}

Staun

_(1972).

Phenotypic

correlations

The

_phenotypic

correlation coefficients

_(rp)

are

_reported

in table III.

_They

were not

markedly

different from the raw correlations

_{previously computed}

from variables

uncorrected for the identified fixed effects

_(Jurie

et

_al,

_1994).

In

_general

these coefficients were low. The

_only

notable

_{relationships}

were the

_{positive relationship}

between the oxidative

activity

(ICDH)

and the

_proportion

of

_type

I

_myosin

_(rp

= +0.31 and _rp = _+0.41

respectively

in the ST and the LT

_muscle)

both in

_opposition

to the

_glycolytic

_activity

_(rp

= -0.20 and

rp = -0.30

respectively

for the oxidative

activity

and rP = -0.44 and r

myosin).

The

_phenotypic

correlations between similar characteristics measured in both muscles were _very low.

Similarly

no clear

_phenotypic

_{relationship appeared}

between muscle

_biological

characteristics and

_production

traits.

Genetic correlations

The

genetic

correlation coefficients are

reported

in table IV. In

general they

were

much

_higher

than the

phenotypic

coefficients.

There was a clear

_{genetic antagonism}

between the

glycolytic

activity

(LDH)

and

the

_proportion

of

_type

I

_myosin

_(rg

= -0.72 and

rg = -0.87

respectively

in the ST and the LT

_muscle).

The oxidative

_activity

_(ICDH)

was

_clearly

associated with

the

_proportion

of

_type

I

_myosin

_(rg

= +0.64 and

rg =

+0.28

respectively

in both

muscles)

and

_opposed,

to a lesser

_extent,

to the

_glycolytic

_activity

_(rg

= -0.26

and _r9 = -0.33

respectively

in both

muscles).

These coefficients were

_homogeneous

across muscles and coherent with the observed

phenotypic

coefficients.

The

_genetic

correlations of these 3 muscle characteristics with carcass

composi-tion traits were also

_{highly significant}

and

homogeneous

across the muscles. The

oxidative

activity

(ICDH)

and the

_proportion

of

_type

I

_myosin

_{(MHC I)}

were

genet-ically

associated with carcass fat content

_{(respectively rg}

= +0.79 and r

in the ST muscle and _rg = +0.93 and

rg = +0.17 in the LT

muscle)

and

genetically

opposed

to carcass lean content

_{(respectively}

_rg = -0.79 and

rg = -0.65 in the ST

muscle and _rg = -0.92 and _r9 = -0.17 in the LT

_muscle).

In

_contrast,

the

glycolytic

activity

(LDH)

was

_genetically

associated with carcass lean content

_(rg

= _+0.66 and _rg = +0.42

respectively

in the ST and the LT

muscles)

and

genetically

opposed

to carcass fat content

_(rg

= -0.69 and

rg = -0.38

respectively

in both

muscles).

The

_genetic

correlations of these 3 characteristics with

_growth

traits

were not so

clear. In both

_muscles,

a

_positive

correlation

_appeared

between the

protein/DNA

ratio and

_daily

_{gain during}

the

_fattening

_period

_(rp

= +0.76 and

rg = +0.33

respec-tively

in the ST and the LT

_muscles).

_However,

the

_{genetic relationship}

between this

_protein/DNA

ratio and other

_production

traits or muscle characteristics were

not similar across muscles.

A

principal

components

analysis

has been

_performed

in each muscle to summarize these

_{genetic relationship}

_among muscle characteristics and

_production

traits. The correlations between each trait and the first 2

_principal

_components

are shown in

figure

1. In both

_analyses

the first

component

was

_{primarily explained by}

the

_genetic

antagonism

between lean and fat contents. In both

_muscles,

this first

_component

also

_clearly

discriminated the

_glycolytic

and oxidative activities and the

_proportion

of

_type

I

_myosin.

This clear

_antagonism

between the LDH

_glycolytic

_activity

on

and fast twitch-white fibers

_(type

_IIb)

was

_largely

under

_genetic

control and was

related to the

_composition

of

_growth.

Muscles of the animals that were

genetically

leaner,

also had a

_{higher proportion}

of

_glycolytic

and fast twitch fibers. The second

component

was

_essentially

related to the

_growth

capacity.

The relative

position

of the

_protein/DNA

ratio to other traits was different in the 2 muscles and difficult

to

_interpret.

The oxidative

_activity

_(ICDH)

was the

only

muscle characteristic that

displayed

a

positive genetic

correlation between muscles

_(rg

=

+0.64),

while the

protein/DNA

ratio and the

_glycolytic

_activity

_(LDH)

were

_{genetically independent}

when

mea-sured in the ST or in the LT muscle. More

_{surprisingly,}

the

_proportion

of

_type

I

myosin

in the ST muscle

_appeared

to be

_{genetically opposed}

to the same

charac-teristic measured in the LT muscle

_(rg

=

-0.48).

The

relationship

across different

muscles need to be studied further since the

_present

_results,

if

_confirmed,

indicate that the

genetic

control of the muscle fiber

proportions

can be

_quite

different in

skeletal muscles with different functions. If

confirmed,

these results would indicate that interactions _may exist between

_genetics

and muscle functions.

CONCLUSIONS

Although

measured on animals that were

_homogeneous

as far as

_breed,

_{sex, age} and

fattening

system

were

_concerned,

muscle characteristics of the ST or LT muscles of _young bulls were

highly

variable _among

individuals,

with a

significant

_part

that was under

_genetic

control.

_Although

this

_apparent

_{genetic variability}

was

_slightly

lower than the

_{corresponding}

one for

_production

traits,

genetic changes

of muscle characteristics can be

_expected

if

_they

could be

_effectively

selected in

_breeding

programs. Such selection is

theoretically possible

since live measurements of these characteristics can be

developed using biopsy techniques

(Jurie

et

al,

1995).

The choice of the muscles to be

_{sampled depends}

on the actual

_genetic

_relationship

that exists between muscle characteristics of different muscles. The most favorable situation would be the lack of interaction between

_genetics

and the muscle function

influencing

the

_proportion

of different fiber

_types.

Therefore measurements on a

single

muscle would be sufficient to characterize the

_genetic

_ability

of the

potential

young sires.

The

_present

results show that selection for

_{growth capacity}

is not

_clearly

related to

_biological

characteristics of the ST or LT muscles. In

_contrast,

these

characteristics are

clearly

related to carcass

_composition

traits. The

higher

the

genetic

capacity

for

_fattening,

the

_higher

the

_proportion

of

_type

I

_myosin

and the more oxidative the

_{enzymatic activity}

(slow

twitch-red

fibers).

_Therefore,

even

if muscle characteristics are not

_{directly selected,}

_they

_may

_change

in as much

as carcass

_composition

is selected. Selection for leaner animals will increase the

proportion

of the fast twitch and

_glycolytic

_{(type lib)}

fibers.

_Although

the

post-mortem

_aging

rate is known to be more

rapid

(favorable

for

tenderness)

in muscles

characterized

_by

this

_type

of fiber

_{(Valin, 1988),}

the _consequences on meat

_quality

of such correlated

_{genetic changes}

have to be

_quantified

in order to know whether measurements of

_biological

muscle characteristics need to be included in selection

ACKNOWLEDGMENTS

Financial _support from the Minist6re de la Recherche et de la

_Technologie

_(Paris)

and

the UPRA France Limousin Selection

_(Limoges)

is

_{gratefully acknowledged.}

Authors are indebted to the staff of the

_testing

station of the GIE France Limousin

_Testage

_(P6pieu)

and to the technicians of the Institut de

_1’Elevage

_(Limoges)

for

_providing

the

experimental

muscle

_samples.

Authors are

_grateful

to D

Boichard,

INRA

_{CR, Jouy-en-Josas}

for the multitrait REML software he

provided.

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