equine pregnancy

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Mare Anatomy Mare Anatomy Vulva Vulva Vagina Vagina Cervix Cervix Uterus Uterus Oviducts Oviducts Ovaries Ovaries

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Equine Pregnancy--by: Dr. Dhiren Bhoi

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Page 1: Equine Pregnancy

Mare AnatomyMare Anatomy

VulvaVulva VaginaVagina CervixCervix UterusUterus OviductsOviducts OvariesOvaries

Page 2: Equine Pregnancy

Normal uterusNormal uterus

Page 3: Equine Pregnancy

Period of Embryo•• Day 15-55 to 60 - Period of organogenesis.Day 15-55 to 60 - Period of organogenesis.

• • Maximum mobility from day 11-16.Maximum mobility from day 11-16.

• • Fixation between day 14 and 16.Fixation between day 14 and 16.

• • Embryo loses spherical shape, appears Embryo loses spherical shape, appears triangular at day 17-19.triangular at day 17-19.

• • Amniotic sac begins to form around day 21.Amniotic sac begins to form around day 21.

• • 10% of pregnant mares may show weak estrus and 10% of pregnant mares may show weak estrus and increased follicular activity.increased follicular activity.

Page 4: Equine Pregnancy

• Fetal heart beat discernible by day 25 on ultrasound exam.

• Day 25 to 30 - If EED occurs, estrus occurs 2-4 weeks later

• Day 28 - Allantois appears and first allantochorionic villi form at yolk sac border

• Early attachment by day 39

Page 5: Equine Pregnancy

• Day 35-40 - PMSG (eCG) – first detectable

• Day 42 - change from yolk sac to allantochorionic dependence

• Day 50-55 - Accessory corpora lutea formation

• Day 55-60 - Villi cover all chorion touching endometrium except endometrial cup areas

Page 6: Equine Pregnancy

Period of fetus• Day 55-60

• Period of progressive increase in fetal crown-rump length

• Day 60 - Maximal PMSG concentrations

• Day 90 - Estrone sulphate levels begin to increase

• Maximum placental attachment occurs by day 150

• Day 80-240 - Maximum growth of fetal gonads and production of estrogens

Page 7: Equine Pregnancy

Cervical changes from 16 or 17 d to term are elongation, firmness and tubularity. The uterus also has increased tone.

Rectal palpation

Page 8: Equine Pregnancy

   

The chorionic vesicle is distinct and spherical and approximate sizes are:   • 28 d (4 wks) Key lime (pullet egg)   • 35 d (5 wks) lemon   • 42 d (6 wks) orange   • 49 d (7 wks) grapefruit   • 56 d (8 wks) cantaloupe   • By 90 d it is hard to delineate the cranial margin of

uterus.   • Fetal Ballotment per rectum becomes consistent after

150d.   • Aging fetus by size, as in the cow, is imprecise.   • Differentials which may confuse the examiner include

the bladder and enlargement in the non pregnant tract at the base of the uterine horn.

Page 9: Equine Pregnancy

Rectal examinationRectal examination

I. Cervix: • In early pregnancy (16 to 30 days) the cervix

can be palpated on the floor of the pelvis as a rigid, firm structure (as during dioestrus).

Page 10: Equine Pregnancy

II. Ovaries: • Both ovaries are usually enlarged from 18 to 40 days due to

follicular development and the CL is not palpable. • From 40 to 120 days there is extensive ovarian activity

with ovulations, luteinisation and development of secondary corpora lutea.

• Follicular activity decreases from 120 days to term and the ovaries become small and inactive for the remainder of gestation.

• The position of the ovaries up to 60 days of pregnancy is as for the non-pregnant mare.

• From then on they are drawn forward and medially but remain dorsal (above) to the uterus.

• From 5 months of pregnancy, the ovaries are not usually palpable.

Page 11: Equine Pregnancy

Uterus:Uterus: Both uterine horns and body should be Both uterine horns and body should be palpated. Pregnancy diagnosis is based on tone palpated. Pregnancy diagnosis is based on tone and location of uterus and contents.and location of uterus and contents.

15 to 22 days15 to 22 days The uterus becomes more tubular and turgid from The uterus becomes more tubular and turgid from

15 to 22 days post-ovulation and is readily 15 to 22 days post-ovulation and is readily palpable. It can be difficult topalpable. It can be difficult to feel the conceptual feel the conceptual swelling except in maiden mares. swelling except in maiden mares.

22 to 28 days22 to 28 days At about 22 days the conceptual swelling At about 22 days the conceptual swelling

develops at the uterine horn/body junction. This develops at the uterine horn/body junction. This corresponds to fixation, when the conceptus corresponds to fixation, when the conceptus stops migration in the uterus and becomes fixed stops migration in the uterus and becomes fixed in position, prior to implantation. The swelling is in position, prior to implantation. The swelling is 3 to 4 cm in diameter (about the size of a golf-3 to 4 cm in diameter (about the size of a golf-ball) and it bulges ventrally.ball) and it bulges ventrally.

Page 12: Equine Pregnancy

28 to 35 days28 to 35 days The uterus is still turgid, and the conceptual The uterus is still turgid, and the conceptual

bulge is more obvious and the embryonic bulge is more obvious and the embryonic vesicle is 3 to 6 cm in diameter. The uterine vesicle is 3 to 6 cm in diameter. The uterine wall over the conceptus begins to feel thin.wall over the conceptus begins to feel thin.

35 to 60 days35 to 60 days As the conceptus grows the swelling As the conceptus grows the swelling

becomes larger and spherical and appears becomes larger and spherical and appears more as a fluid sac. By 42 days it is about 5 more as a fluid sac. By 42 days it is about 5 x 7 cm (the size of a tennis ball). The x 7 cm (the size of a tennis ball). The uterine tone around the bulge begins to uterine tone around the bulge begins to decrease so that the swelling becomes less decrease so that the swelling becomes less tensetense

Page 13: Equine Pregnancy

60 to 90 days60 to 90 days By 60 days the swelling is about 12 cm in By 60 days the swelling is about 12 cm in

diameter and fills the pregnant horn. After 60 diameter and fills the pregnant horn. After 60 days the pregnancy is like an elongated football days the pregnancy is like an elongated football and starts to involve the uterine body. One must and starts to involve the uterine body. One must be careful not to confuse it with the bladder or a be careful not to confuse it with the bladder or a case of pyometra. The uterus migrates cranially.case of pyometra. The uterus migrates cranially.

Between Between days 60 and 100days 60 and 100, the uterus is low , the uterus is low within the abdomen and the foetus can not within the abdomen and the foetus can not usually be palpated;usually be palpated;

From 4 to 5 months onwards the foetus can From 4 to 5 months onwards the foetus can usually be palpated.usually be palpated.

Page 14: Equine Pregnancy

Ultrasound ExaminationUltrasound Examination Diagnostic ultrasound plays a pivotal role Diagnostic ultrasound plays a pivotal role

in the reproductive management of the in the reproductive management of the mare and no deleterious effects of mare and no deleterious effects of ultrasonography have been reported in ultrasonography have been reported in man nor in the equine. man nor in the equine.

A thorough understanding of normal A thorough understanding of normal ultrasonographic anatomy is vital for ultrasonographic anatomy is vital for veterinarians involved in broodmare work.veterinarians involved in broodmare work.

Page 15: Equine Pregnancy

Principles of diagnostic ultrasoundPrinciples of diagnostic ultrasound •• Diagnostic ultrasound utilises sound frequencies between 2 Diagnostic ultrasound utilises sound frequencies between 2

and 10 MHz.and 10 MHz. •• Ultrasound is produced by application of an alternating Ultrasound is produced by application of an alternating

voltage to piezoelectric crystals which change in size and produce a voltage to piezoelectric crystals which change in size and produce a pressure or ultrasound wave. Returning echoes deform the same pressure or ultrasound wave. Returning echoes deform the same crystals which generate a surface voltage.crystals which generate a surface voltage.

• • Most diagnostic ultrasound machines use the principle of Most diagnostic ultrasound machines use the principle of brightness modulation (B-mode) where the returning echoes are brightness modulation (B-mode) where the returning echoes are displayed as dots, the brightness of which is proportional to their displayed as dots, the brightness of which is proportional to their amplitude.amplitude.

• • Real-time B-mode ultrasound is a dynamic imaging system where Real-time B-mode ultrasound is a dynamic imaging system where information is continually updated and displayed on a monitor. information is continually updated and displayed on a monitor.

• • Ultrasound is attenuated within tissues and attenuation is related Ultrasound is attenuated within tissues and attenuation is related to the density of the tissue, the heterogeneity of the tissue and the to the density of the tissue, the heterogeneity of the tissue and the number and type of echo interfaces.number and type of echo interfaces.

• • Bright (specular) echoes are produced when a large proportion of Bright (specular) echoes are produced when a large proportion of the beam is reflected back to the transducer; these echoes are the beam is reflected back to the transducer; these echoes are displayed as white areas on the ultrasound machine screen.displayed as white areas on the ultrasound machine screen.

• • No echoes are produced when the sound is transmitted and not No echoes are produced when the sound is transmitted and not reflected; these areas are displayed as black on the ultrasound reflected; these areas are displayed as black on the ultrasound machine screen.machine screen.

Page 16: Equine Pregnancy

Day 11Day 11 pregnancypregnancy

Page 17: Equine Pregnancy

A 14 day A 14 day conceptus conceptus viewed by viewed by ultrasound. Note ultrasound. Note the regularity of the regularity of the circular the circular shape.shape.

Page 18: Equine Pregnancy

By 17 days the By 17 days the regularity of shape regularity of shape is starting to is starting to deteriorate - note deteriorate - note the "ragged" edges the "ragged" edges now seen on the now seen on the 17-day pregnancy 17-day pregnancy compared to the compared to the 16-day. 16-day.

Page 19: Equine Pregnancy

By 23 days the embryo By 23 days the embryo itself can be seen with itself can be seen with ultrasound - here it is ultrasound - here it is visible between the red visible between the red calliper marks on the calliper marks on the image. The heartbeat can image. The heartbeat can also start to be detected at also start to be detected at this stage. Note here how this stage. Note here how the regular rounding has the regular rounding has completely deteriorated, completely deteriorated, and the conceptus is and the conceptus is appearing oval, and appearing oval, and without "smooth" edges.without "smooth" edges.

Page 20: Equine Pregnancy

At 33 days, the developing At 33 days, the developing allantois (the outgrowth of allantois (the outgrowth of the embryo's hindgut the embryo's hindgut which forms the bladder, which forms the bladder, carries blood vessels in the carries blood vessels in the umbilical cord, and later umbilical cord, and later combines with the chorion combines with the chorion to form the placenta) is to form the placenta) is visible, and the yolk sac visible, and the yolk sac (visible here as the upper (visible here as the upper portion of the dark section) portion of the dark section) is regressing. The apparent is regressing. The apparent "division" in the conceptus "division" in the conceptus at this stage is not to be at this stage is not to be mistaken for twin embryos mistaken for twin embryos - of which clearly only one - of which clearly only one is visible.is visible.

Page 21: Equine Pregnancy

A different view of A different view of a 35 day a 35 day pregnancy shows pregnancy shows that there can be that there can be differences differences

Yolk/Allantoic Yolk/Allantoic sac.sac.

Embryo position.Embryo position.

Page 22: Equine Pregnancy

By day 39 the yolk By day 39 the yolk sac has almost sac has almost completely completely regressed and is regressed and is visible here only as visible here only as the dark circular the dark circular area immediately area immediately above the embryo above the embryo (compare this with (compare this with the 33 day image).the 33 day image).

Page 23: Equine Pregnancy

In this photograph of a 50-In this photograph of a 50-day fetus, the legs, head, tail day fetus, the legs, head, tail and eye are all clearly and eye are all clearly defined externally. defined externally.

Internally organs and skeletal Internally organs and skeletal structures are in place. structures are in place.

Within 10 days or so, the sex Within 10 days or so, the sex of the fetus can be of the fetus can be determined using ultrasound, determined using ultrasound, by establishing the direction by establishing the direction of migration of the pedicle of migration of the pedicle that will become either the that will become either the penis or the clitoris. penis or the clitoris.

Upward migration towards Upward migration towards the anus of course indicates the anus of course indicates a female.a female.

Page 24: Equine Pregnancy

Fetal sexingFetal sexing Numerous reasons for desiring knowledge of the sex Numerous reasons for desiring knowledge of the sex

of the fetus of the fetus • Appraisals, Appraisals, • Insurance coverage, Insurance coverage, • Payment of stud fees, Payment of stud fees, • Sales consignments, Sales consignments, • Mating lists, Mating lists, • Sale or purchase, etc. Sale or purchase, etc.  Gender determination is based on the location of the Gender determination is based on the location of the

genital tubercle.  genital tubercle.  The genital tubercle is the precursor of the penis The genital tubercle is the precursor of the penis

in the male or the clitoris in the female.  in the male or the clitoris in the female.  The tubercle migrates toward the umbilicus in the The tubercle migrates toward the umbilicus in the

male and toward the anus in the female.  male and toward the anus in the female. 

Page 25: Equine Pregnancy

Ideal times for performing the procedure are Ideal times for performing the procedure are from 59 to 68 days or 5 to 6 months.  from 59 to 68 days or 5 to 6 months.  Before 58 days the tubercle is not distinct Before 58 days the tubercle is not distinct

enough and has not migrated sufficiently to enough and has not migrated sufficiently to make a distinction.  make a distinction. 

After 70 days the fetus is hard to reach until After 70 days the fetus is hard to reach until it is approximately 3.5 to 4 months of age.  it is approximately 3.5 to 4 months of age. 

As the fetus gets larger, a transabdominal As the fetus gets larger, a transabdominal approach may be preferred.  approach may be preferred. 

If cattle are available, it is easier to learn the If cattle are available, it is easier to learn the technique on cattle because the manipulations technique on cattle because the manipulations are easier and they are more tolerant of are easier and they are more tolerant of prolonged rectal examinations. prolonged rectal examinations.

Page 26: Equine Pregnancy

External signs of pregnancyExternal signs of pregnancy     Although abdominal enlargement is Although abdominal enlargement is

characteristic of pregnancy, it is unreliable characteristic of pregnancy, it is unreliable as a diagnostic sign.  as a diagnostic sign. 

Ballotment or observed movements of the Ballotment or observed movements of the fetus can often be seen late in gestation.  fetus can often be seen late in gestation. 

Mammary changes are quite variable.  Mammary changes are quite variable.  Pelvic changes (relaxation of the pelvic Pelvic changes (relaxation of the pelvic

ligaments) occur late in gestation but are ligaments) occur late in gestation but are often difficult to detect.  often difficult to detect. 

Cessation of estrus behavior is variable and Cessation of estrus behavior is variable and unreliable.  unreliable. 

Some mares will continue to show estrus Some mares will continue to show estrus even when pregnant. even when pregnant.

Page 27: Equine Pregnancy

Indirect Indirect pregnancy pregnancy

teststests    

Page 28: Equine Pregnancy

The presence of The presence of eCGeCG has been has been used as a test for pregnancy used as a test for pregnancy because it is only found in because it is only found in pregnant mares.  pregnant mares.  The problem is that it remains The problem is that it remains

elevated after the cups are elevated after the cups are formed even if fetal death formed even if fetal death occurs. In house tests are occurs. In house tests are available which makes them available which makes them attractive in some situations attractive in some situations (e.g. miniature horses).  (e.g. miniature horses). 

For example, with the For example, with the Synbiotics test, it is reported Synbiotics test, it is reported that 20% of samples are that 20% of samples are positive at 30 d, 66% at 38 d, positive at 30 d, 66% at 38 d, 76% at 40 d, and 92% at 42 d. 76% at 40 d, and 92% at 42 d.

Endometrial cups in a mare.

eCG test

Page 29: Equine Pregnancy

Progesterone concentrations in plasma can be measured by Progesterone concentrations in plasma can be measured by radio-immunoassay, radio-immunoassay,

Alternatively the enzyme-linked immunosorbent assay Alternatively the enzyme-linked immunosorbent assay (ELISA) tests can be used in a veterinary practice laboratory (ELISA) tests can be used in a veterinary practice laboratory giving the results more rapidly. giving the results more rapidly.

At At 1717 to to 2222 days post-ovulation, pregnant mares should have days post-ovulation, pregnant mares should have progesterone levels progesterone levels aboveabove 2 ng/ml2 ng/ml . .

However an incorrect diagnosis of pregnancy can occur in However an incorrect diagnosis of pregnancy can occur in cases of:cases of:1.    Prolonged luteal phase, 1.    Prolonged luteal phase, 2.    Early embryonic death or 2.    Early embryonic death or 3.    Mares with a short luteal phase. 3.    Mares with a short luteal phase.

Not all mares with high progesterone concentrations are Not all mares with high progesterone concentrations are pregnant and high progesterone levels pregnant and high progesterone levels only indicate that only indicate that luteal tissue is present in the ovaryluteal tissue is present in the ovary. ·      . ·      

Plasma progesterone test

Page 30: Equine Pregnancy

Produced by Produced by fetal trophoblastfetal trophoblast cells that invade the cells that invade the maternal endometrium beginning around day 35 to maternal endometrium beginning around day 35 to form the form the endometrial cups.endometrial cups.

Concentrations of eCG in the blood from Concentrations of eCG in the blood from approximately 40 days after ovulation and these approximately 40 days after ovulation and these concentrations usually persist at least until 80 - 120 concentrations usually persist at least until 80 - 120 days after ovulation. days after ovulation. 

False positiveFalse positive results are seen when the pregnancy results are seen when the pregnancy fails fails afterafter the endometrial cups have formed and the endometrial cups have formed and continue to produce eCG. continue to produce eCG.

False negativeFalse negative results may be seen if sampling is at results may be seen if sampling is at an incorrect time and in some mares which can be an incorrect time and in some mares which can be negative for eCG as early as 70 days after ovulation.negative for eCG as early as 70 days after ovulation.

Equine chorionic gonadotrophin (eCG)

Page 31: Equine Pregnancy

Placental oestrogen determinationPlacental oestrogen determination

Serum Serum oestrone sulphateoestrone sulphate levels are detectable From levels are detectable From day 65 of pregnancy onwards day 65 of pregnancy onwards

It increase to It increase to peak around day 200peak around day 200, remaining high , remaining high until after 300 days. until after 300 days.

The oestrogens come from the foeto-placental unit The oestrogens come from the foeto-placental unit especially the foetal gonads which are very large especially the foetal gonads which are very large during the later stages of pregnancy. during the later stages of pregnancy.

Small amounts of oestrogen are produced by the Small amounts of oestrogen are produced by the follicles on the mare’s ovaries. follicles on the mare’s ovaries.

In general, this is a In general, this is a reliable assayreliable assay and can even be and can even be performed on faeces. performed on faeces.

Also a good indicator of Also a good indicator of foetal viabilityfoetal viability.  .  

Page 32: Equine Pregnancy

EstrogensEstrogens are are elevated 150 d to term.elevated 150 d to term.

It is due to production It is due to production from fetal gonads.  from fetal gonads. 

The Cuboni test, based The Cuboni test, based on fluorescence of on fluorescence of urine, is 90% accurate urine, is 90% accurate after 100 d, 100% after 100 d, 100% accurate after 150 d.  accurate after 150 d. 

Cuboni test

Page 33: Equine Pregnancy

Estrone sulfateEstrone sulfate can be tested for in almost any bodily can be tested for in almost any bodily fluid. fluid.

In serum there is a sharp rise after 60 d, peak levels by In serum there is a sharp rise after 60 d, peak levels by 80 d.  80 d. 

Before 60 d a false positive can be obtained due to Before 60 d a false positive can be obtained due to estrus. estrus.

In milk a similar pattern is observed, only with lower In milk a similar pattern is observed, only with lower values.  values. 

It is considered an indicator of fetal viability after 44 d. It is considered an indicator of fetal viability after 44 d. In feces, it can be found after 4 mos. In feces, it can be found after 4 mos. Also be found in urine. Also be found in urine. Commercial tests available "Equi Test - ES" Commercial tests available "Equi Test - ES"

Estrone sulfate test

Page 34: Equine Pregnancy

Determination ofDetermination ofOestradiol-17-Oestradiol-17-b b Hormone in Hormone in

FaecesFaeces The faeces samples of pregnant and non-pregnant The faeces samples of pregnant and non-pregnant

mares contained a mean oestradiol-17 b concentration mares contained a mean oestradiol-17 b concentration of 9.39 ± 2.63 and 7.70 ± 2.00 ng/g, respectively in of 9.39 ± 2.63 and 7.70 ± 2.00 ng/g, respectively in the 4th month of gestation. the 4th month of gestation.

From the 5th month of pregnancy the oestradiol-17 b From the 5th month of pregnancy the oestradiol-17 b concentration in pregnant mares was significantly concentration in pregnant mares was significantly higher than in non-pregnant mares.higher than in non-pregnant mares.

Oestradiol-17 b levels were estimated to be 71.20 ± Oestradiol-17 b levels were estimated to be 71.20 ± 8.00 and 4.60 ± 2.20 ng/g in pregnant and non-8.00 and 4.60 ± 2.20 ng/g in pregnant and non-pregnant mares in the 5th month of pregnancy, pregnant mares in the 5th month of pregnancy, respectively.respectively.

Page 35: Equine Pregnancy

Early Pregnancy FactorEarly Pregnancy Factor EPF EPF - two components - two components

EPF-A - Uterine tube  EPF-A - Uterine tube  EPF -B - Ovary EPF -B - Ovary Production requires signal from fertilized ovum (ovum Production requires signal from fertilized ovum (ovum

factor) released under prolactin presence after sperm factor) released under prolactin presence after sperm penetration.  penetration. 

Appears 4-6 hours Appears 4-6 hours Disappears with fetal death Disappears with fetal death Non-detectable at 20 days in milk and 30 days in serum Non-detectable at 20 days in milk and 30 days in serum Lateral flow dipstick test Lateral flow dipstick test It does not work in the cow, so I have doubts in the It does not work in the cow, so I have doubts in the

mare. mare.

Page 36: Equine Pregnancy