Genetic and environmental factors affecting some reproductive traits of Holstein cows in Cuba

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Genetic and environmental factors affecting some

reproductive traits of Holstein cows in Cuba

A Menendez Buxadera, L Dempfle

To cite this version:

Original

article

Genetic

and

environmental factors

affecting

some

reproductive

traits

of Holstein

cows

in Cuba

A Menendez Buxadera

L

_Dempfle

1

Centro

de

_{Investigacidn}

_para el

_{Mejoramiento Animal,}

Carretera Central Km 21

_1/2,

Cotorro, Havana, Cuba;

2

International

_{Trypanotolerance Center,}

PMB 14,

Banj!al,

Gambia

(Received

6 March

_{1996; accepted}

14

_August

₁₉₉₇₎

Summary - A total of 226 651

_fertility

records of

_dairy

cows obtained from 1980 to

1988 was studied in order to determine the environmental and

_genetic

factors

_affecting

the

reproductive performance

of Holstein cows under Cuban conditions.

Only

43.9% of

the inseminated females were _pregnant at first service;

however,

for heifers this value

was 63.1%. The seasonal

_variability

was

_higher

for heifers and for

_primiparous

than for older

_lactating

cows. The best

_performance

was found from

_February

to

_April,

whereas

during

the hot and humid summer

(July

to

_September)

poorer results were obtained.

Age

at

_calving

or number of

_calvings

was another _important environmental source of

variation: the earlier the

_calving

the poorer is the next

_{reproductive performance.}

The

genetic analyses

were made within

_calving

number with the REML

_procedure.

For heifers

(226

sires,

45 575

_records)

the

_heritability

and the

_genetic

coefficient of variation were:

2.26 and

_10.94%,

3.24 and

_11.24%,

and 3.04 and 6.19% for conception rate

_(CR),

numbers of services _per conception

(SG)

and conception status

_(CS

=

1/SG),

respectively.

For first

calving

females

₍₂₈₀

_sires,

43 647

_records)

the results were: 1.94 and

15.93%,

3.25 and

12.80%,

and 3.47 and 9.47% for

CR,

SG and

CS, respectively.

For the second and third

calving,

the results were _poorer. For the

calving

interval and

days

open, the heritabilities

were between 1.86 and 4.64%. The results of SG were selected as the best and more useful

traits

_{showing high genetic}

correlations

_{(> 0.60)}

for the same traits in different

calving

number.

Holstein cattle breed

_/

reproduction traits

_/

genetic parameters

/

tropical conditions

Résumé - Facteurs génétiques et environnementaux intervenant sur les performances

de reproduction des vaches Holstein à Cuba. Au total 226 651

_{enregistrements}

de

fertilité

de vaches laitières obtenus de 1980 à 1988 sont

analysés

en vue de déterminer les

facteurs génétiques

et environnementaux intervenant sur les

_performances

de

_reproduction

de vaches Holstein dans les conditions cubaines. Seulement

_43,9

%

des femelles

inséminées

sont gestantes à la

_{première insémination,}

alors que pour les

génisses

ce taux est de

_63,1

%.

La variabilité due à la saison

_{apparaît plus}

élevée chez les

_génisses

et

_primipares

que chez

les vaches

plus âgées.

Les meilleurs résultats sont obtenus de

février

à avril, alors _que

les

_plus

mauvais sont observés durant l’été

_(juillet

à

_septembre),

qui est chaud et humide dans les conditions cubaines.

L’âge

au

_vêlage

et le rang de

vêlage

sont aussi

d’importantes

sources environnementales de variation. Plus le

vêlage

est

précoce, plus

la

reproduction

suivante est mauvaise. Les

_{analyses génétiques}

ont été réalisées intrarang de

_vêlage

en

utilisant une méthode REML. Pour les

_génisses

₍₂₂₆

_pères,

45 575

_{performances),}

les héritabilités et

_coefficients

de variation

_génétiques

sont de 2,26 et 10,9l,

%,

de 3,24 et

11,24 % et de 3,04 et _{6,19 % respectivement} pour le taux de conception

(CR),

le nombre d’inséminations par

fécondation

(SG)

et l’état de

_gestation

_(CS

=

1/SG).

Pour les

primipares

(280

pères, 43647

performances),

ces résultats sont de 1, 94 et _15,93

_%,

de

3,25 et 12,80 % et de 3,47 et 9,47 % respectivement pour

CR,

SG et CS. Pour les vaches

au deuxième et troisième

vêlages,

les estimations sont

plutôt inférieures.

L’intervalle

entre

_vêlages

et la durée entre

_vêlage

et

_fécondation

ont des héritabilités estimées variant entre

_1,86

et 4,64 %. Les résultats

_relatifs

au nombre d’inséminations _{par gestation}

(SG)

conduisent à considérer ce critère comme le meilleur et le

_{plus efficace}

_pour la

_sélection,

manifestant

par ailleurs une

_forte

corrélation

_génétique

(>

_0,

60)

entre rang de

vêlage

pour

ce critère.

race bovine Holstein

/

_performances de _reproduction

/

_{paramètres génétiques}

/

conditions tropicales génétiques

INTRODUCTION

Milk

_production

is the main cattle

_goal

in Cuba. Great amounts of resources

have been

_used,

not

_only

in construction of cattle barns and

_{infrastructure,}

but also thousands of Holstein females have been

_imported

from Canada. A national

breeding

plan

(NBP)

was established in

_1964,

in which artificial insemination

(AI)

played

an

_important

role in

_{crossbreeding}

between native Zebu cattle and Holstein sires. The

_general

_strategy

and some results of NBP are offered in

Anonymous

(1978)

and Prada

_(1984).

The

_population

of

_purebred

Holstein cows is

_relatively

_large

_(more

than 100 000

heads)

and it is very

important

to

_analyze

the

_general

performance

of all traits of economic

_importance

in order to

_improve

the national

_breeding

scheme. For milk

_production

and its

_{constituents,}

an

analysis

was made

by

De los

Reyes

(1985)

for several environmental factors. The main

_genetic

_parameters

were

_reported

_by

Guerra et al

_(1987),

whereas some

_aspects

on

_genotypic

x environmental interaction and its role in the estimation of sire

_breeding

value were

presented by

Men6ndez

Buxadera and Guerra

₍₁₉₈₁₎

and Men6ndez Buxadera et al

_(1989).

According

to the results

_previously

_mentioned,

it could be

_concluded,

_regardless

of the

_stressing

environmental factors

_{affecting dairy}

_traits,

that a _very

_important

For the last _{15 years,} a

_great

number of _papers has been

_published

with

_respect

to

genetic

aspects

of

_{reproductive performance}

of

_dairy

cattle

_(Janson,

_1980;

Hansen

et al

_{1983; Jansen, 1986;}

Weller

_1989).

In

_general

_terms,

there is a consensus that a

_large

number of traits related to

_reproduction

shows low

_heritability

_(lower

than

_10%),

but a

_high

_genetic

_variability.

_Considering

this fact and also the economic

_importance

of

_fertility,

certain traits of

_reproductive

_performance

should be considered in the selection criterion

_{(secondary traits)}

for a

_breeding

scheme.

Unfortunately,

under

_tropical

conditions almost no research related to this

_topic

has been conducted. For this reason, a

_study

of the

_genetic

and environmental

aspects

of

_{reproductive performance}

of Holstein cattle in Cuba was carried out and the main results will be

presented

in this paper.

MATERIALS AND METHODS

Available data

A total of 270 000 individual records of Holstein cows

_calving

from

_January

1980

to December 1988

_throughout

the

_country

was available for this

_study.

These data

sets

_belong

to a

_system

developed

at the National Center for Cattle

_Recording

(CENCOP)

to maintain the control of the Holstein as a _pure breed but also some

important

reproductive

data have been collected: date of _pregnancy and

_calving;

registration

number of the cows and sire of the

calf;

number of insemination services in which the cow was

_pregnant;

herd

code;

results of

_calving:

abortion - if

_{gestation period}

was less than 260

_days;

stillbirth or not - if

_{gestation period}

was between 260 and 295

days;

sex of the calf - no abortion.

Taking

into account the data

_available,

a

_procedure

was conducted in which the

permanent

file of identification of each animal maintained at CENCOP was

_merged

with the

_reproductive

file mentioned

_previously

in order to obtain the

_registration

number of the sire of the cow and birth date of the cow.

As a _consequence of this process, the new data set has a total of 232 291 records

with the information of each cow.

The number of

_calvings

was not available in the

_original

_file,

so it was decided

to

_generate

_according

to _age at

_calving.

Table I shows the

_general

characteristics of the definitive data set.

Only

Holstein sires born in Cuba and with a minimum of 20

daughters

in a

specific calving

and distributed in at least five herds were considered for

_genetic

l7raits

The

_following

_reproductive

traits were studied:

number of services _{per pregnancy}

_SGi;

conception

status

_CS

_i

= 100 !

_(1/SG

_i

_);

rate of

_conception

for first services

_CR

_i

_{= ( 100}

to

_pregnant

at first

service,

0

_otherwise);

calving

interval

_(in

_days),

_CI

_i

_{(i :}

number of

_calving);

interval between

_calving

and _pregnancy

_(in

_days)

_DO

_i

_(i:

number of

_calving).

Records

_ending

with an

abortion,

as well as records outside of the _range 300-730

days

for CI and 20-450

_days

for DO were deleted. The first three

_Cl

_i

and

DO

i

were

_analyzed.

With the

_logical

_exception

of

DO

i

and

_Ci

_i

_,

all

_reproductive

traits

are determined for _any value of i

_(between

0 and

_4).

Management

systems

The

_organization

of cattle

production

in Cuba is

_mainly

based on

_large

state

enterprises

(more

than 10 000

_heads),

which are

_fairly

uniform with

respect

to structure and

_{organization.}

The

_dairy

units have around 200 females which are

milked twice

_daily

with

_milking

machines. From 10 am to 4 _pm, all cows are

_kept

indoors where

_they

receive

_forage

or

_silage

and

water,

and graze the rest of the

time. Inseminations are conducted

_early

in the

_morning

or late at

_night

and the service bulls are selected

_yearly

_according

to a

_plan

for each

_enterprise.

As a

rule,

between two and five service bulls are used at the same time in each herd.

_Pregnancy

diagnosis

is made

_by

rectal

_palpation

_(after

60-90

_days

of

_{insemination,}

_by

a

specific

technician).

All the individual records of each animal are maintained at the

_unit,

and once a month an official

_inspector

from CENCOP visits the herd in order to

estimate milk

_yield

of each cow in each

_milking.

All data are sent to CENCOP once a month.

Statistical

_procedures

where _{p is} the

_general

mean;

H

i

is a fixed effect of a combination of herd and

year which was

absorbed;

_M

_j

is a fixed effect of month of

_calving

(or

month of

pregnancy)

for j

=

1, ..12; A,!

is a fixed effect of number of

_calvings

(or

_age at

pregnancy)

for k

_{= 1, ..4;}

_ei!!1 is a random residual.

This model was

_applied

in order to determine the

_magnitude

of the fixed effects of certain environmental factors

_affecting

each

_dependent

variable.

_Age

at

_calving

was considered to be a factor. Solutions for _age and months were estimated after

constraining

the last level of each factor to zero.

The estimation of

_genetic

_parameters

was the

_objective

of the second mixed

model which has the

following

matrix notation:

where: Y is a vector of

_{observations;}

₍₃

is a vector of fixed effects

_including

age and

herd-year-season

of

_calving

_{(natural trimester);}

s is as vector of random sire effects and e is a vector of random

_residuals,

and X and Z are incidence matrices.

The

_following

_assumptions

were made:

The

_QS

and

_Q

_e

were

estimated

_by

restricted maximum likelihood

_(REML)

(Patterson

and

_Thompson,

_1971).

The

_general

statistical

properties

and

description

of this method of variance

_components

are well illustrated

by Kennedy

(1981),

Dempfle

et al

₍₁₉₈₃₎

and Lin and McAllister

_(1984).

The variance

_components

estimated for

SG

i

were used for

_breeding

value estimation

(EBV)

through

the BLUP

procedure

with a mixed model similar to model

_2,

but with the _age at

_calving

as a

covariable. The

_computer

_program was

_{developed by}

_Caleyo

(1989)

and was

_applied

within

calving

number. The

_relationship

matrix was not considered.

The

genetic

correlation

_(Rg)

between

SG

i

was estimated

by

two methods. The first

_procedure

was

published by

Calo et al

₍₁₉₇₃₎

and was _very well

presented by

Blanchard et al

₍₁₉₈₃₎

and is based on the

_weighted

covariance between estimated

EBV

I

;

in that case,

only

those sires with more than 70 effective

_daughters

on

each

_calving

were considered. The second estimation of

_Rg

was based in a REML

procedure

with a model similar to model 2 but

_using

the

_expected

_components

of the variance

of

a new trait

SG

T

=

(SG

i

₊

SG

i+i

).

In order _to fulfill these

conditions,

_a

new data set was formed with those cows with records on

_SG

_i

in

_adjacent

_calvings.

RESULTS

Environmental effects

The results of the statistical

_analysis

_according

to model 1 show _very

_highly

significant

effects

_(P

<

_0.001)

for the different factors

_{included; however,}

the determination coefficient

_(R

₂

₎

of the model was between 9.2 and

12.4%

for all

traits evaluated in heifers and first

_calving

_stages.

For older animals

_(more

than

two

_calvings)

the

R

2

was

between 3.6 and

26.9%.

In all _cases, the

_highest

R

z

was

obtained for

SG

i

and the lowest for

CR

i

.

The solutions for month effects on

_{heifer, first,}

second and third

_calving

con-ception

status

_(CS

_i

₎

are shown in

figure

1.

Although only

CS

i

is

_presented,

the

general

pattern

was the same for the rest of the characters. The best results were

obtained in March and

_April

_(lower

_SG

_i

_,

and

_higher

CR

i

and

_CS

_i

_),

whereas the

poorest

fertility

rate was in

_September

and October.

_{Plotting climatological}

data on the same

_figure

shows the _very evident

relationship

between the hot and humid

summer and a lower

reproductive

performance,

and the

_relationship

between the

winter and the less humid

_period

from

_January

to

_April

and the best results for

CSi, CRi

and

_SGi.

Concerning days

open

(DO

i

)

and

calving

interval

_(CI

_i

_),

month effects were the

same as for

_CS

_i

_,

_CR

_i

and

_,

_SG

_i

which was as

expected. However,

the most

_important

component

of

DO

i

and

_CI

_i

is the interval between

_calvings

and first service and these characters were not available in our data

_sets,

so no more details can be

provided

on these traits.

The year effect was

_{highly significant}

(P

<

_0.001)

for the main traits studied. The solutions for each character

_expressed

as deviations from the last year are

shown in table III. In

_general

_terms,

_during

the

_period

of time

_represented

in our

data

sets,

a

_positive

trend in

_{reproductive performance}

of our Holstein females was

found;

however,

even with these

_changes

an

_optimum

or near

_optimum

level of

fertility

is never reached. The

_analysis

of the effect of _years was made also within

calving

number and the same

_pattern

was found

_except

in

_heifers,

which showed

The effect of _age or number of

_calving

on the

_dependent

variables was

highly

significant

(P

<

_0.001).

This was

_{expected according}

to the information offered

in table II. In

_general,

the

reproductive performance

decreases as the number of

calving

increases as a _consequence of cumulative stress due to lactation and

_previous

reproductive

disorders. When data were

analyzed

within

calving

number,

the trend

of _age effects was

_negative,

so the _younger the

calving

is reached the _poorer is the

next

_reproductive

_performance

of

_lactating

females.

Genetic effects

The results of the mixed model show a

_{highly significant}

effect

(P

<

_0.001)

of

sires for all traits. The

heritability

(h

2

)

for each character and variance

_component

estimated

_by

REML are

_presented

in table

_IV,

where the additive

_genetic

coefficient

of variation

_(CVg)

is included.

For

_CR

_i

and

CS

i

,

the

genetic

variance was more or less the same for different

calvings,

with the

_exception

of second

_calving

in which an

unexpected

result was

found. For

_DO

_i

and

_Cl

_i

_,

an

_opposite

_pattern

was found and a clear reduction in

the

_genetic

variance was obtained for older cows

_compared

to

_primiparous

cows.

The

_genetic

variance for

_SG

_i

increased 2.8 times for first

_calving

with

respect

to

results in

heifers; however,

for second and third

_calving

the estimates were lower.

The total

_phenotypic

variance increases when

_estimating

in heifers to third

_calving.

As a _consequence of these

particular

trends in both variance

_components,

the

h

2

for all traits was

_higher

for heifers and first

calving.

The same results were obtained

for

_CVg.

Concerning

the number of

_reproductive

characters available it would be necessary

to

_perform

a certain

_type

of discrimination. In this

_context,

it will be _very

important

to take into account not

_only

the value of

h

2

and

CVg,

but other

_{peculiarities,}

such as facilities for

_recording

and

multiple objectives

in the

principal

factors

limiting

the level of

_productivity

of

_populations.

In this sense, it will be very

useful to conduct a relative

_comparison

_among some

fertility

_parameters

in different

populations

of Holstein cows

(table V).

Before 100

_days

after

_calving

there is not

a clear difference _among the

populations

of

_percentage

of females

inseminated,

which is _very

_important

to consider because the

_{climatological}

conditions,

systems

of

_management

and level of

_feeding

are

_quite

different in the three countries. The real

_problems

_emerge when we look at the

percentage

of

_pregnant

females before 100

_days

after

_{calving. According}

to this

_complete

relative

_comparison

and

_taking

into account the results of Caral et al

_(1984),

who

_reported

that

_only

43%

of cows

not

_pregnant

at first service

_presented

second heat in a normal

_period

of

_time,

it can be concluded that at least in female Holstein

populations,

limiting

factors

are

_closely

related to the number of services per

conception

(SG

i

).

Together

with this

_advantage,

this character is related to first service

_conception

_rate,

_{is easy} to

record under field conditions in heifers and

lactating

cows

_{and, furthermore,}

it will be useful for other purposes such as sire

fertility

evaluation; thus, SG

i

will be the

preferred

trait in our

_{breeding objectives.}

_However,

it is _{necessary to} determine the

The

_general

_pattern

of this

_study

_{(table VI)}

shows that there are medium to

_high

genetic

associations between

SG

i

at different

_calvings.

The results were _poorer with

non-consecutive records in

_comparison

to

_adjacent

ones. The

_Rg

estimated

by

the covariance of

_EBV

_I

was

_higher

than the results of

_{REML; however,}

the differences

would not

_suggest

that the same

_genetic

bases exist for this trait measured at

DISCUSSION

Unfortunately,

there are not _many references available on

_{reproductive performance}

of Holstein cattle in the

_tropics.

_However,

it is obvious from our results that the level

is _very low

_(see

table

_II).

_According

to Roman Ponce

₍₁₉₉₂₎

this is the

_general

trend

in

_tropical

conditions and this low

_fertility

rate of cattle

represents

the

_principal

limiting

factor

_affecting

the

_productivity

of cattle in these

_regions.

The seasonal variation obtained in these results is similar to those

_patterns

reported

in the

_{subtropical regions}

of Mexico and Florida

_(Ingraham

et

_{al, 1974;}

Thatcher et

_al,

₁₉₈₄₎

and in the _very hot and arid environmental conditions of Arizona

_{(Monty, 1984)}

and Israel

_(Heimann,

_1982;

Ron et

_al,

_1984).

_Many

studies have been conducted in order to

_study

the role of heat stress in the summer on the

productive

and

_{reproductive performances}

of cattle in that _area, with the

_objective

of

_reducing

the

_depressive

effects with a new

_{management system.}

_According

to

Thatcher

_(1974),

Thatcher et al

_(1984),

_Monty

₍₁₉₈₄₎

and Wazdauskas et al

_(1986),

the maximum

temperature

after insemination is one of the main factors

_affecting

the

_{reproductive performance}

of Bos taurus cattle in

_tropical

countries.

_High

temperature

causes a

_complete

hormonal

imbalance,

which in turn _may

_change

the flow of nutrients to the

uterus,

and at the same time raises the uterus

_temperature.

This mechanism contributes to

_creating

a more hostile ’uterus environment’ and

increases the

_probability

of

_fertility

failure or

_subsequent

_embryo

death. In

_figure

1 it

can be observed that the

_magnitude

of the month effect is _very intense for all cattle

categories; however,

it would be evident that this environmental stress was twice

as

_high

for heifers and first

_calving

females

as for the rest of the cows. In

_fact,

this behavior is

_{contradictory}

in the literature

_(Thatcher,

_1974;

Thatcher et

_al,

_1984),

according

to which the older

lactating

females must be more variable and more

sensitive to heat stress. It is

_possible

to

_speculate

on this

_apparent

_paradox.

When

an

_adequate

level of

_feeding

and

_management

is

_available,

the live

_weight

at first

such

_conditions,

the

_variability

of

_fertility

traits in heifers and first

_calving

females can be less affected

by

heat

_stress;

however,

this is very far from our conditions.

The

_developement

and

_{body weight}

curves of Holstein females in Cuba are _poorer

than those

expected

for this breed

_(Men6ndez

Buxadera et

_al,

_1983);

on _average our

females reach

_{approximately}

400

_kg

live

_weight

in the middle of first

_calving,

which

means that this

_type

of animal is less mature

_(in

the sense of

weight).

_Therefore,

a

higher

percentage

of the nutrients received must be used for the

_growing

process.

This mechanism could account for the

_{higher variability}

and

_sensitivity

of _younger females under our conditions.

All these environmental factors

require

a more detailed and

profound

research

in order to determine the

_{physiological}

mechanism.

_However,

the

_practical

conse-quences of the seasonal variation in

reproductive performance

of Holstein females

under our

_tropical

conditions could be used. For

_instance,

these results show that

from

_September

to

_January

around

60%

of the cows

_{(not heifers)}

_calving

in that

period corresponded

to the season of

higher fertility

rate

_(see

_fig

_1).

_According

to

this

_pattern,

it would be

_highly

recommended to inseminate the

_majority

of the females from

January

to

_April

with semen of Holstein sires of

_{higher breeding}

value for milk

_production

_(principal

traits in our

breeding

scheme).

The

_preliminary

es-timates of such a

_policy

show an

_improvement

of not less than

20%

in

_genetic

potential

in our female

_population

with

_respect

to the normal

_practice

of bulls in service all _year round.

According

to our results it was clear that the

h

2

for

different

_fertility

traits were

low

_{(< 5%)}

and similar to many

reports

on this

subject

(see

review of Men6ndez

Buxadera,

1993);

however,

the

_genetic

_variability

_(table

_IV)

was

_higher

than most

of the results in the literature

_(see

_{Janson, 1980; Berger}

et

_al,

_1981;

_Raheja

et

_al,

1989 for SG and

Baptist

and

Gravert,

1973;

Janson, 1980; Jansen,

1986 for

non-return rate as a trait related to

_CR).

This is due to the reduced

_culling

rate

_applied

in our female

population,

so these data show a

_{complete picture}

of the real

genetic

variability

in the

_{reproductive performance}

of Holstein cattle under the

_tropical

conditions of Cuba. The

_potential

of this

_variability

has not been considered

_by

many researchers on account of the low

h

2

value.

_According

to

_Maijala

₍₁₉₈₇₎

this

is a

_{pessimistic point}

of view

_regarding

the

_{possibilities}

of

_{genetic improvement}

for

fertility

traits.

For

DO;

and

CI

i

there was a clear

reducing

h

2

pattern

when the number of

calving

increased. In

_fact,

this trend is

_contrary

to the results

_{published by}

_Berger

et al

_(1981),

Hansen et al

_(1983),

Jansen

₍₁₉₈₆₎

and

_Strandberg

and Danell

₍₁₉₈₈₎

who obtained a small increase in

h

2

and

_CVg

in older females. For the rest of the traits it was evident that these

_genetic

_parameters

were

_higher

in the first two

_stages

(heifer

and first

_calving),

which is in

_{correspondence}

to Van Raden et al

_(1987),

Raheja

et al

₍₁₉₈₉₎

and Weller

_(1989).

The results for the second

_calving

were

_quite

low and no clear

_explanation

was found.

As a matter of

_fact,

the

_general

_pattern

for

_{higher variability}

_{in younger} females

in

_comparison

to

_multiparous

cows could be a _very

_{important advantage}

in our

breeding

scheme,

since the EBV for characters of the

_{reproductive complex}

must be determined as

early

as

possible,

and

higher genetic

variability

is

equivalent

to

_major

possibilities

for selection and

_breeding.

This is true

_only

if the traits evaluated in heifers and first

_calving

females were in close

relationship

with the same characters

The information available on that

subject

is

contradictory. European

_reports

(Janson,

1980; Distl, 1982; Jansen,

1986)

showed that the same

reproductive

char-acters in both

_types

of females

_present

the same

_genetic

base so the results of

heifers and

primiparous

cows can be used for sire evaluations. Another

recommen-dation was made

by

North American researchers

(Hansen

et

_al,

_1983;

_Raheja

et

_al,

1989;

Van Raden et

_al,

₁₉₈₉₎

who

_reported

lower

_genetic

correlations

_(Rg

<

_0.30)

although

the

_tendency

was the same.

According

to our results

(table VI)

the

_genetic

correlation

(Rg)

for

SG

i

in

different

_calvings

was

_higher

than 0.60 when

_Rg

was estimated

_by

the

_weighted

covariance between EBV of the

_sire,

whereas

_Rg

> 0.49 when the REML

_procedure

was used. Both estimates are difficult _{to compare} because the value of

Rg

depends

on the

_quality

of the data set.

_However,

_great

differences were not observed. Our

point

of view is in favor of the results obtained

_through

the

EBV,

of the

sire,

because

in REML the same

_design

matrix was used and the

_{computing requirement}

was

greater.

According

to our results it is

possible

to conclude that the same

_genetic

bases

exist between certain

_fertility

traits measured in different

_stages

of the

_reproductive

life of cows. This

aspect

will be very

important

for sire evaluation purposes since

the records of heifers and first

_calving

could be used in this sense.

CONCLUSIONS

This

_study

shows

_positive

_yearly

trends in the level of

_{reproductive performance}

of Holstein cattle under Cuban

_conditions,

_{nevertheless,}

the

_general

mean was

_quite

low.

_Calving

number and month of

_calving

were the

_principal

environmental factors

affecting

the

_fertility

rate of Holstein

_females;

this

_aspect

was more critical in heifers

and

primiparous

in

_comparison

to older

lactating

cows.

According

to these results the best

_performance

was achieved from

_February

to

_April,

_{corresponding}

to the

winter season, while

_during

the hot and humid summer

(July

to

_September)

_very

poor results were obtained. This seasonal

pattern

must be

_interpreted

as a

general

reproductive

behavior of Holstein cattle in the

_tropics,

which could be used under

practical

conditions.

From a

breeding

_point

of

_view,

our

_study

confirms that the

h

2

of the characters

corresponding

to the

_{reproductive complex}

shows the

_expected

low value

_(h

₂

<

_5%).

However,

the

_genetic

coefficient of variation was

higher

than the value

reported

for

_developed

and

_temperate

countries

_(see

Menendez

_Buxadera,

_1993),

so

_plenty

of space is available for

breeding.

The number of services per

conception

(sG

i

)

was selected as the character more related to our

limiting

factor

affecting

the

reproductive

performance

of this breed under

_tropical

conditions.

_{Furthermore, SC}

_i

could be used for various purposes and it will be

_possible

to measure this at an

_early

age

(heifers).

In this sense, the

relationship

between

SG

i

in heifers and first

_calving

females was 0.60 and

_higher

than the 0.88 found between older _cows, which allows

us to use all information available for

_breeding

value estimation of AI sires.

_Taking

into account that the

_procedures

used for

_Rg

estimation could be affected

_by

some

bias,

it is

_highly

recommended to use a more

_powerful

statistical

_procedure

such as an individual multitrait animal

model,

with different matrix

design, although

the

ACKNOWLEDGMENT

The authors wish _{to express} their

gratitude

to their

colleague

F M6nissier

_(Inra,

_SGQA,

F 78352

_{Jouy-en-Josas cedex,}

_France)

for his valuable

_{help during}

the process of

publica-tion of this article.

REFERENCES

Anonymous

(1978)

Selection program for

dairy

and beef

production through

Artificial

Insemination in Cuba. In:

_Breeding

and

Artificial

Insemination,

FAO/SIDA

Seminar,

30

_October,

1978,

Habana,

Cuba

Baptist

Von

R,

Gravert HO

(1973)

Die Fruchtbarkeit der Tochter in der Bullen Selection.

Zuchtung

45, 339-411 1

Berger PJ,

Shanks

RD,

Freeman

_AE,

Laben RC

₍₁₉₈₁₎

Genetic aspects of milk

_yield

and

reproductive performance.

J

Dairy

Sci 64, 114-126

Blanchard

_PJ,

Everett RW, Searle SR

₍₁₉₈₃₎

Estimation of

_genetic

trends and

correla-tions for

Jersey

cattle. J

_Dairy

Sci 66, 1947-1954

Caleyo

M

₍₁₉₈₉₎

_{Un programa para} estimaciones BLUP del valor

_gen6tico

de los

semen-tales. VIII Jornada

CIMA,

November

1989, Cotorro,

La

_Habana,

Cuba

Calo

_LL,

McDowell

_RE,

Van Vleck

LD,

Miller PD

₍₁₉₇₃₎

Genetic _aspects of beef

pro-duction among Holstein-Friesians

pedigree

selected for milk

_production.

J Anim Sci

37, 676-682

Caral

_{J, Iglesias C,}

Martinez

G,

Solano R

_(1984).

Influencia del numero de parto en el

periodo

intercelo y distribuci6n anual de partos en

_ganado

Holstein. In:

Reproduction

des ruminants en zone

_tropicale

(P

Chemineau,

D

Gauthier,

J

Thimonier,

eds),

8-10

juin

1983, Pointe-h-Pitre

_(FWI).

Les

_Colloques

de L’INRA no _20, 491

(abstract),

Inra

Versailles

De los

_Reyes

A

₍₁₉₈₅₎

Causas de variaci6n no

_gen6ticas

_que afectan la

producci6n

del

ganado

Holstein y estimaci6n de factores de

ajuste

por edad. Tesis Doctor en

Ciencias,

La

_Habana,

Cuba

Dempfle L, Hagger C, Schneeberger

M

₍₁₉₈₃₎

On the estimation of

_genetic

parameters

via variance components. Genet Sel

Evol 15,

425-444

Distl 0

₍₁₉₈₂₎

Selection for

_fertility

traits. Proc 2nd World

_Cong

Genet

_Appl

Liv

_Prod,

4-8 October 1982,

Madrid, Spain,

Vol 7, 580-585, Editorial

Garsi,

Madrid

Foote RH

₍₁₉₇₈₎

Reproductive performance

and

_problems

in New York

dairy

herds. Search

Agric

Anim Sci 8, 18

Guerra

_D,

Cordovi

_J,

de los

Reyes

A

₍₁₉₈₇₎

Parimetros

_gen6ticos

de las

primeras

tres

lactancias en vacas Holstein. II Jornada

ACPA,

_mayo 29-30,

1987,

Ciudad de

Habana,

Cuba

Hansen

LB,

Freeman

AE, Berger

PJ

₍₁₉₈₃₎

Association of heifer

_fertility

with cow

fertility

and

_yield

in

_dairy

cattle.

Dairy

Sci 66, 306-314

Heiman MM

₍₁₉₈₂₎

Breeding

Israeli Holstein. Holstein

Herdbook, Summary

of 1982 milk and butterfat

production

Ingraham

RM, Gillette

_{DD, Wagner}

WD

₍₁₉₇₄₎

Relationship

of _temperature and

humid-ity

to

_conception

rate of Holstein cows in

_subtropical

climate. J

_Dairy

Sci

_57,

476-481

Jansen J

₍₁₉₈₆₎

Studies of

_fertility

in

_dairy

cattle on

analysis

of AI data.

Wageningen

Lands,

PhD

Thesis,

The Netherlands

Janson L

₍₁₉₈₀₎

Studies on

_fertility

traits in Swedish

dairy

cattle. Swedish Univ

_Agric

Sci,

Genetics

Dept,

report 45

Kruif A de

₍₁₉₇₅₎

An

_{investigation}

of the parameters which determine the

_fertility

of a

cattle

population

and some factors which influence these _parameters.

_{Tijdschr Dierg}

100, 1089-1098

Lin

_CY,

McAllister AJ

₍₁₉₈₄₎

Monte Carlo

_comparison

of four methods for estimation of

genetic

parameters in the univariate case. J

_Dairy

Sci

_67,

2389-2398

Maijala

K

₍₁₉₈₇₎

Genetic control of

_reproduction

and lactation in ruminants. J Anim Breed Genet

_104,

53-63

Menendez Buxadera A

₍₁₉₈₈₎

Importancia

de la interacci6n

genotipo-ambiente

en la

evaluaci6n de sementales lecheros. Boletin Resefia, CIMA 6

Menendez Buxadera A

₍₁₉₉₃₎

Variacion

_genetica

del

_{comportamiento reproductivo}

en el

vacuno: revision

blibiographica.

Rev Cubana

Reprod Animal 19,

3-53

Menendez Buxadera

_A,

Guerra D

₍₁₉₈₁₎

Relaci6n entre el valor

_gen6tico

de sementales Holstein evaluados en

_Cuba,

Canada _y Mexico, Proc ALPA _16, 161

Menendez Buxadera

_A,

P6rez

_B,

Valle E,

Rodriguez N,

Herrera

_R,

Varela 0

₍₁₉₈₃₎

Crecimiento _y desarrollo de la hembra Holstein en Cuba. IV Reun ACPA _1983,

69-89

Menendez Buxadera

A,

de los

_{Reyes A,}

Guerra D, Cordovi J

_(1989).

Genetic

variability

of milk

_production

from Holstein cows

_according

to the level of milk

yield

of the herd. Cub J

_Agric

Sci

_23,

9-15

Monty

de Jr

₍₁₉₈₄₎

_{Early embryo}

death in cattle

_during

thermal stress. In:

_Reproduction

des ruminants en zone

tropicale

(P

Chemineau,

D

Gauthier,

J

Thimonier,

eds),

8-10

juin

1983, Pointe-h-Pitre

_(FWI).

Les

_Colloques

de L’Inra no _{20, 285-298,} Inra Versailles Patterson

_{HD, Thompson}

R

₍₁₉₇₁₎

_Recovery

of interblock information when block sizes

are

_unequal.

Biometrika

_58,

545-554

Prada N

₍₁₉₈₄₎

_Programa

nacional de mejoramiento

gen6tico

vacuno. Rev ACPA 3, 20-26

Raheja

KL, Burnside EB, Schaeffer LR

₍₁₉₈₉₎

Heifers

_fertility

and its

_relationship

with

cow

_fertility

and

production

traits in Holstein

dairy

cattle. J

Dairy

Sci 72, 2625-2629

Roman Ponce H

₍₁₉₉₂₎

_Reproducci6n

_y

_{manejo reproductivo}

de los bovinos

_productores

de leche y carne en el

_tropico.

In: Avances en la

produccion

de leche _y carne en el

Tropico

Americano

_{(Ferndndez-Boca, ed),}

_Santiago

de

_Chile,

_1992,

_§

IV 131-168, FAO

Ron

_M,

Bar Anan

_{R, Wiggans}

G

₍₁₉₈₄₎

Factors

_affecting

conception rate of Israeli Holstein cattle. J

_Dairy

Sci 67, 854-860

Strandberg E,

Danell B

₍₁₉₈₈₎

Genetic and

phenotypic

parameters for

production

and

days

open

period

in the first three lactations of Swedish

dairy

cattle. Proc VI World

Cong

Anim

_Prod,

Genetic section, June

_27-July

1, 1988, Helsinki

Thatcher WW

₍₁₉₇₄₎

Effects of season, climate and temperature on

reproduction

and

lactation. J

Dairy

Sci 5, 360-368

Thatcher

_{WW, Badinga L,}

Collier

_RJ,

Mead

_MM,

Wilcox CJ

₍₁₉₈₄₎

Thermal stress

effects on the bovine _conceptus:

_early

and late _pregnancy. In:

_Reproduction

des

ruminants en zone

_tropicale

_(P

_Chemineau,

D

_Gauthier,

J

_Thimonier,

_eds),

8-10

_juin

1983,

Pointe-h-Pitre

_(FWI).

Les

_Colloques

de L’INRA no _20,

_265-284,

Inra Versailles

Van Raden

_PM,

Freeman

_{AE, Berger}

PJ

₍₁₉₈₇₎

_Relationship

_among

_production

and

reproduction

in

_nulliparous

and first lactation Holstein cattle. 82th Meet

_ADSA,

June 21-24,

1987,

Columbia

Wazdauskas

_FC,

Whittier

_WD,

Vinson WE, Pearson RE

₍₁₉₈₆₎

Evaluation of

reproduc-tive

_efficiency

of

_dairy

cattle with

_emphasis

on

_timing

of

_breeding.

J

_Dairy

Sci

_69,

290-297

Weller JJ

₍₁₉₈₉₎

Genetic

_analysis

of

_fertility

traits in Israeli

_dairy

cattle. J

Dairy

Sci 72,