First report of cytogenetic studies in Spanish breed horses

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First report of cytogenetic studies in Spanish breed

horses

M Moreno-Millán, A Rodero, Fj Alonso, A Sanz

To cite this version:

First

_report

of

_cytogenetic

studies

in

_Spanish

breed horses

M

Moreno-Millán A

_Rodero.

FJ

_Alonso,

A Sanz

Instituto de

_{Zootecnia, CSIC,}

Facuttad de Veterinaria,

Laboratorio de

_{Citogenetica,}

Unidad de

_Genetica,

14005 -

Cdrdoba, Spain

(Proceedings

of the 9th

_{European Colloquium}

on

_Cytogenetics

of Domestic

_Animals;

Toulouse-Auzeville,

10-13

_July

₁₉₉₀₎

chromosomes

/ horse

/ abnormalities

During

the

_past

three _years, our

laboratory

has been

cytogenetically

studying

Spanish

breed horses in

_{general and,}

more

_{particularly,}

those animals which had

some

_type

of

_irregularity

in their

_reproductive

_capacity.

We found two

_types

of

chromosome

alterations related to these

_{irregularities.}

Sixty Spanish

breed horses of both sexes,

including

10 females with

_reproductive

problems

and 5 subfertile

_males,

were studied. Three of these females had the

appearance of intersex horses with marked stallion behavior and with no

_apparent

estrus. The

_remaining

7 were

_{phenotypically}

normal females with

_{highly irregular}

estrus

_cycles

and a

_history

of

_{miscarriages.}

The 5 subfertile males studied had _very

poor

quality

semen, with little

motility

or _azoospermy.

They

were

phenotypically

normal.

Peripheral

blood cultures were set _up

_using

a

_slightly

modified version of de

Grouchy

et al’s

₍₁₉₆₄₎

method.

Twenty-four

hours after

treatment,

the G- and

C-banding

techniques

were

_applied

to the

_preparations

obtained

_by

_air-drying,

according

to the methods of Dutrillaux and

_Lejeune

₍₁₉₇₁₎

and Sumner

_(1972),

respectively.

The G-banded

_karyotypes

were sorted

following

the recommendations of the

Reading

Conference

_{(1976) (Ford}

et

_al,

_1980),

while the sex chromosomes were

identified

_according

to Blue et al

_(1978).

The

_analyses

_gave the

_following

results.

For a

_{phenotypically}

intersex mare with the characteristics of a

pseudo-hermaphrodite

male: the vulva was normal but 2 testicular formations were found

in the

_inguinal

_region

and a short

_vagina

closed at the

_end;

no uterus or ovaries

were

detected; cytogenetic analysis

showed the _presence of an

_X-trisomy

(Moreno

Milldn et

_al,

_1989).

For 2 mares whose external examinations showed one of them to be a normal

surfaced. This animal showed

_aggressive

behavior towards the

_males,

had no estrus

and did not

_respond

to the

_conceptive

treatment

_prescribed.

_Cytogenetic

_analysis

revealed that the animal was a carrier of the cellular

_XX/XY

chimerism.

We also had the

_opportunity

to

_study

a _young mare with an external _appearance

of intersex. Instead of

_ovaries,

we found

only

a structure on the left

side,

similar

to a

testicle,

4 cm

_long

and 2 cm

_wide,

with a smooth surface and thick walls.

Histological analysis

showed an absence of

_primordial

follicles and severe ovarian

hypoplasia.

No structure was observed which

_{might correspond}

to a testicle. The

animal’s the chromosome

_complement

was

XX/XY

chimerism,

with a

_predominance

of the XX

population.

In the literature consulted on

XX/XY

chimerism in the

_horse,

we found that

this

_anomaly

is associated with a vascular anastomosis between

_dizygotic

fetuses

which

_gives

rise to fertile mares, the

opposite

of what

_happens

in cattle

_(Bouters

and

_{Vandeplassche, 1972;}

Podliachouk et

_al,

_1974).

The few known cases of true

hermaphrodites

with

_XX/XY

chromosome constitution

_(McIlwraith

et

_al,

_1976;

Dunn et

_al,

₁₉₈₁₎

_{had organs of both} sexes which was doubtless the result of

double fertilization. Given the characteristics

analyzed,

we think that the animals

we studied can be classified as

having gonadal dysgenesis

and,

more

_{specifically,}

ovarian

_hypoplasia

in the second animal and not

_{intersexuality.}

_Chandley

et al

(1975)

observed an

_X-trisomy

in a case of ovarian

hypoplasia;

the case cited here is

the first in which ovarian

_hypoplasia

is associated with

_XX/XY

cellular chimerism. The

_remaining

7 mares

_{investigated presented reproductive}

alterations with

highly

irregular

estrus

_cycles,

defects in

_conception

and

_spontaneous

abortions. External and internal examinations revealed a normal female

_phenotype

with

completely

normal external and internal

_genitalia;

_{cytogenetic analysis}

determined that

_they

were XX mares.

We

_investigated

5

_{phenotypically}

normal stallions that had _poor

_quality

_semen, with _very little

_motility;

2 of them were

_azoospermic.

_Cytogenetic

_analysis

showed that all these animals had a normal XY chromosome

_complement.

REFERENCES

Blue

_IVIG,

Bruère

_AN,

Dewes HF

₍₁₉₇₈₎

The

_significance

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of the mare. New Zealand Vet J _26, 137-141

Bouters

_{R, Vandeplassche}

M

₍₁₉₇₂₎

Twin

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CK,

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SW, McEnery RJ,

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₍₁₉₇₅₎

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Mcllwraith

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₍₁₉₇₆₎

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Vet J 8, 156-160

Moreno-Mill6n

M, Delgado JV, Lopez

G

₍₁₉₈₉₎

An intersex horse with X-chromosome

trisomy.

Vet Rec

124,

169-170

Podliachouk

L,

Vandeplassche

NI, Bouters R

₍₁₉₇₄₎

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_gemellaire,

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