Maternal Recognition of Pregnancy

Maternal Recognition of Pregnancy

• Establishment and maintenance of pregnancy necessitates the prolongation of the luteal phase within the estrous cycle through the persistence of a single corpus luteum (CL) or multiple CLs
• Elevated progesterone concentrations are sustained due to the persistence of luteal tissue
• The presence of a viable developing embryo prevents CL regression, inhibiting the return to estrous in polyestrous species. This is Maternal Recognition of Pregnancy
• This maternal endocrine response can be detected before the blastocyst attaches to the endometrium via microvilli

Importance of Topic

• Knowledge within this topic is essential to understand possible causes of pregnancy failures due to early disturbances of communication mechanisms between the embryo and dam
• Understanding these mechanisms facilitates development of early pregnancy diagnostic tests

Conceptus Definition

• Conceptus consists of the embryo plus all associated extra-embryonic membranes

Maternal Recognition in Sheep

• In sheep, the conceptus produces a protein existing in 3-4 isoforms with a molecular weight of about 18-20 kDa
• The protein secreted by the conceptus was originally named ovine trophoblast protein (oTP-1)
• oTP-1 is a type 1 interferon, now classified as ovine tau interferon
• Production of the trophoderm starts around day 10, at the time of blastocyst elongation
• The influence of interferon-tau (IFN-t) in maternal recognition of pregnancy alters the dynamics of prostaglandin F2 alpha (PGF2a) secretion
• Secreted IFN-t silences transcription of the estrogen receptor alpha gene in uterine luminal and superficial glandular cells
• This silencing precedes estrogen-induced expression of oxytocin receptors in these cells
• IFN-tau indirectly suppresses oxytocin receptor expression in endometrial epithelial cells
• Oxytocin from luteal and pituitary origin is then unable to bind to the uterus, leading to a reduction in pulsatile PGF2a secretion

Maternal Recognition in Cattle

• The antiluteolytic signal from the bovine conceptus is a protein weighing 24,000 Da
• This protein was designated bovine trophoblast protein (bTP-1)
• A description of bTP-1 includes bTP-1 crossing reacting immunologically with oTP-1
• bTP-1 also possesses a high amino-acid sequence homology with both oTP-1 and interferon-alpha (IFN-a)
• Interferon-tau (bIFN-t) is now the classification of bTP-1
• The maximum secretion is between days 16 and 19 of gestation
• Secretion initially happens at the time of blastocyst elongation and keeps secreation continuous until day 38 of gestation
• bIFN-t exerts antiluteolytic effects via silencing estrogen receptor expression in uterine epithelial cells
• It prevents estrogen-induced expression of oxytocin-receptors in these cells

Maternal Recognition in Goats

• Similarly to other ruminants, the caprine conceptus secretes a protein now called caprine interferon-tau (cIFN-tau) originally designated as cTP-1
• cIFN-tau is secreted between days 16 and 21 of gestation
• cIFN-tau suppresses pulsatile prostaglandin secretion from the endometrium and extends the CL lifespan
• Prolongation of luteal function occurs spontaneously in pseudopregnancy with unmated does, the CLs persists with fluid (hydrometra) accumulating in the uterine lumen
• Active immunization of cyclic goats against PGF2a results in luteal persistence and the development of hydrometra

Maternal Recognition in Pigs

• Maternal recognition of pregnancy involves preventing luteolysis via uterine-derived prostaglandins
• After the entry of the embryo into the uterus on day 4, the embryos migrate throughout both uterine horns approximately 2 days after ovulation
• By day 12, the embryos are evenly spaced, a process known as spacing
• The early porcine conceptus converts progesterone into estrone and estradiol-17b, along with isomers like 16a,17estradiol, and 16 alpha,17-estradiol
• Rapid blastocyst elongation increases estrogen production, enabling the conceptus to stimulate a large surface area of the endometrium locally
• Estrogen production by the conceptus plays an important role with maternal recognition and the extension of the CL lifespan

Additional Pig Information

• Maternal (endometrial) and conceptus-derived products participates in a complex signaling cascade to establish pregnancy, attachment, and implantation
• Cascade Products are : protease, calcium, growth factors, adhesive molecules, and cytokines
• A second sustained release of estrogens by the conceptus is necessary between days 14 and 18 for luteal persistence after the initial estrogen secretion at day 11
• Conceptus-secreted estrogen prevents luteal regression through a direct luteotrophic effect and a reduction in endometrial synthesis and release of PGF2a
• Luteotropic effects also protects CLs protecting against the luteolytic action of PGF2a. by secretion of prostaglandins E2 and maintaining LH receptors in the CLs.
• Estrogens exert their effects by altering the transport of PGF2a from an endocrine (towards the uterine vasculature) to an exocrine (into the uterine lumen) direction
• Estrogen-induced prolactin receptors in the endometrium facilitate redirecting, which prevents PGF2a from reaching the CLs

Pig Interferons

• Conceptus produces interferons during elongation (11-17 days of gestation)
• The two interferons that are identified are Type 1 (IFN-delta) and Type 11 (IFN-gamma).
• The functions that are postulated are a protective antiviral role and can act in conjunction with conceptus derived estrogens to prolong the CL life span

Maternal Recognition in Horses

• Equine conceptus produces estradiol and estrone, which enhance the production of uteroferrin
• The spherical conceptus migrates within the uterine lumen, fixing at the base of the uterine horn between 16 to 18 days of gestation
• Equine conceptus, unlike ruminants, does not secrete interferon
• Although it produces estrogen in high amounts from day 10, the estrogen is unable to extend the luteal lifespan

Maternal Recognition in Dogs

• The bitch is atypical because the luteal phase length exceeds that of pregnancy
• No need for maternal recognition of pregnancy to maintain the CLs' lifespan and continue progesterone production.
• CLs of pregnant and non-pregnant bitches necessitates luteotropic support by luteinizing hormone (LH) and dominantly Prolactin, especially during the second half of their lifespans

Maternal Recognition in Cats

• The luteal phase length in the mated but non-pregnant (pseudopregnant) queen is about 40 days
• The luteal progesterone production continues for another 20 days in pregnant females.

Pregnancy Diagnosis

• In polyestrous species (cattle, horse, pig, sheep, goats), the early and accurate identification of nonpregnant individuals is important for rebreeding
• Sensitivity describes the correctness of identifying pregnant animals using a diagnostic method
• Specificity is the correctness of identifying non-pregnant animals
• It is important that inexperienced veterinarians chose a good time to diagnose when their confidence is high, regardless of what method is used

Methods to detect pregnancy

• Methods can be species-specific or common to all species
• The methods consist of management, clinical, ultrasonography, and laboratory.
• Management and Clinical are most common and will-tried methods
• Ultrasonography and laboratory are more specific and have recently been improved and refined.
• Broader principles behind technology behind ultrasonography is needed before the methods applicable to the various species are described

Ultrasonography Types

• Ultrasound fetal pulse detector was the first type used based on the Doppler phenomenon
• High frequency sound waves emitted from a probe are reflected at an altered frequency when they hit a moving object, such as the fetal heart or blood
• The altered reflected waves are received by the probe and amplified with audible sound or a color image which can be measured measuring blood flow in both arteries and veins
• Ultrasonic Amplitude Depth Analyzer (A Mode) emits high frequency sound waves and receives the sound reflected at interfaces of tissues of different acoustic impedance.
• The amplitude echoes show as a one - dimension display for varying depths shown on an oscilloscope or by light emitting diodes or by squeak -producing devices
• Success from the device has been shown in many species, especially notably the sow

B-Mode Information

• an advanced technology that shows a mode image display with acoustic impedance
• The (brightness ) mode image displays provide a two - dimensional section of the tissues
• The technique is referred to as real time ultrasound or imaging and indicates and implies live or moving images
• Become a instrument tool for studying reproductive events on many species
• Transducer prove can be inserted into the rectum or vagina or placed on the body
• Numbers of piezoelectric crystals contained in the transducer undergo expansion and contract high frequency sound waves high when an electric current is present

Ultrasound notes

• To prevent reflection from tissue, gas, or interface, air cannot be trapped between the transducer face and tissues
• Methyl cellulose (gel) is applied to the transducer before placing it on skin to eliminate air
• An area that is relatively hairless should be focused in the area, and should be clipped if not

Methods and Processes of Pregnancy Diagnosis

• The methods of pregnancy diagnosis is management, clinical, ultrasonographic, and laboratory methods
• Management method: failure to return to estrous occurs when a mare is pregnant and requires the presence of a stallion teaser
• The mares must be accustomed to to the routine 16 days of service in continuation with 6 days after
• False positives occur when the mares has a silent heat, and or the mare becomes enestrous from lactation or environmental factors
• Also has a prolonged luteal phase without conceptus or prolonged luteal phase associated with embryonic death and this is called pseudopregnancy
• False negatives will occur in a few mares which will show estrous as though they are pregnant at the time
• Clinical method: 1.visual inspection of the vagina via speculum is used for a vaginal exam and 2. palpation transrectally using the hand and arm
• For experienced practitioners, methods with pregnancy diganosis are quick, accurate, and applicable
• VAGINAL EXAM: pale pink mucosa vaginally, mucus is scant and sticky , the cervix is small , and external os is filled with tacky mucous
• False positives can occur if vagina is indistinguishable from diestrous.
• Errors are possible because of prolonged luteal phase and pseudo pregnancy.

Rectal Palpation

• During gestation with first 3 months- follicles are normally present
• 17-21 days after pregnancy- Uterine tone is marked with the uterine cornua- palpatated as resilient and tubular
• Palpation of the conceptus is first after 17-21 days after- a small soft swelling of 2.4 to 2.8cm is apparent
• Distension is made appreciated between 21-30 days- cranial portion of portion is felt only
• Diameter of conceptual swelling is 3-4 cm @ day 30
• Size reaches tennis ball- 6-7 cm in diameter @day40
• measures -13x9 oval in shape @ day 60
• 23x14 cm measured in size @ day 90
• can identify twin conceptuses up to 60 days
• Ballotte possible at 100 days when it floats in fetal uterine body fluid
• Results that are false by rectal palpation= pyometra is confused with pregnancy
• Early stages w/involuted uterus in mares by the foal heat is from pregnancy
• Pseudopregnancy can develop
• Mares with embryonic/abortion death after confirmation require embryo resorption
• False negatives can occur- after service date- with unconfirmed palpation

Ultrasound Notes

• Mode is now commonly used
• 5.0 MH imaging mode makes the gestation at the point of 9 days
• Swelling vesicle appears as a black sphere of -3 mm
• @ 11 days - 98% vesicles have been identified
• Conceptus moves in the uterus-uterine and cervix are easily located
• Vescle rapid Growth- occurs in 9 -16 days
• Fixation at horns -16 to 18 days
• Conceptual vesicle's diameter- - 19- 24 diameter

Twin Gestation, Conception and Ovaries

• Twin ovulations occur in 30% of occurrences in thoroughbred and draught mares
• Fertilization fails, death occurs to embryos before or after, death of one fetus (uncommon), abortion ( costly one common sequel) will explain how its changed with twins
• Before fixation management, early determination is possible at scanning both horns and bodies in the uterine
• Determining of the foal gender is possible
• Genital tubercle has to establish relationship to structures to be based
• Genital tubercle- Precursor of penis embryo

Determining Characteristics to ultrasound

• Tubercle moves from behind hind legs to tail or near umbilicus if male or female
• 59-60 days- Gestational age is appropriate
• Determining can get hard after age passes

Methods to Determining Conception (lab)

• 1.collect plasma progestogens before when the mare comes to estrous
• 22 -16 samples after service show high progesteone- pregnancy- typical from estrous
• prolonged results= false and not as reliant as a method

Chorionic & Biological Methods

• Biological to original for injections to mice
• Identification from chorionic via serum
• 120 -50 days- collected, the 90 is preffered
• immunological= gel, used for gel or hemagglutin
• Kit with reagents= commercial availability and ELISA
• Veterinary possibilty test can carried

Pregnancy Tests

• It cannot be detected if you take the test early or too late, but if the pregnancy samples it can't be detected.
• Low measurements- can't read if briefly
• False positives- fetal and embryonic death
• Endrometrial cups formed- they persist
• ecG's
• 150-300- Days= urinary test

Blood and Urine Tests

• Blood Test- by 85 days- measuring of estrogens in peripheral bloodstream determine pregnancy
• Urine Test- Urinary Estrogen
• Sufficient range with urine in pregnancy at 150-300 days via chemical
• estous is identified in urinary level with these not effective
• 300- 150 accuracy at 100 persent from urine

Diagnosing Info

• As easy as you can diagnosis the pregnancy better
• Terminate pregnancy or ultrasound= identification with mares that are thoroughbred
• twins are cut before forming of cups

Hazards with Diagnosing

• Diagnose will cause issues such as failure or death
• no sign of feeling the tract will hurt pregnancy.
• Normal or examination wont kill the pregnancy if death is going to happen