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Pregnancy diagnosis

PREGNANCY AND ITS DETECTION IN THE COW: A variety of different methods has been, and is still, used to detect the presence or absence of pregnancy in the cow. These range from the identification of substances that are present in body fluids using laboratory assays, and from different ultrasound modes, to simple clinical methods such as transrectal palpation; the latter has been the most ubiquitously used method for the last 70 years


I- Management methods 1-Failure to return to estrus and persistence of the corpus luteum. Failure of regression of the CL at about 21 days, as determined by trans rectal palpation, provides a method of anticipating that the cow is probably pregnant. It is seldom used as a practical procedure and there are reasons for the CL persisting in the absence of pregnancy. Rectal examination at about this time in an individual which was close to or at, estrus would demonstrate the presence of a turgid, coiled uterus and a mucoid vaginal discharge.

Fig. 3.12 Detection of pregnancy in the cow by rectal examination. Uterus gravid 70 days.

Fig. 3.13 Detection of pregnancy in the cow by rectal examination. Uterus gravid 90 days.

Fig. 3.14 Detection of pregnancy in the cow by rectal examination. Uterus gravid 110 days.

Fig. 3.15 Detection of pregnancy in the cow by rectal examination. Pregnancy approaching term.



2-Mammary glands: Mammary changes during pregnancy are best observed in primigravida. The teats of the pregnant heifer begin to enlarge about the fourth month, and with a little experience it is an easy matter to distinguish them from those of the non-pregnant or early pregnant animal. From the sixth month the mammary glands become more firm to the touch and their enlargement can be seen. Hypertrophy is progressive and is particularly marked during the terminal month. As parturition approaches, the glands become grossly enlarged and oedematous and the teats take on a waxy, tumefied appearance. The abdominal wall, particularly in the region of the umbilicus, may also become swollen by oedema. In the dry milk cow, mammary enlargement occurs during the last 14 or so days of pregnancy. After the fourth month a honey-like secretion may be withdrawn from the teats of pregnant heifers.


3-Abdominal ballottement: This is often possible as early as 7 months of gestation in some small breeds such as the Jersey. However, in some fat cows of large breeds it is sometimes impossible even at term. The method involves fairly vigorous pummeling of the ventral abdomen and flank with clenched fists. The object is to push the fetus, which is floating in the fetal fluids, away from the body wall and then identify it as it swings back against the fist which is kept pressed against the abdominal wall.


II-Laboratory methods:1-Identification of early pregnancy factor/early conception factor.Early pregnancy factor (EPF) is an immunosuppressive glycoprotein associated withpregnancy. It was first identified in the mouse and subsequently in a large number ofdomestic species; in the cow it has a molecular weight of 200 000. Commerciallyavailable test kits are available which use the ‘dip-stick’ principle and can detect earlyconception factor (ECF) in serum and milk from as early as 3 days after artificialinsemination, although more accurate results are obtained if samples are taken later at7 to 8 days. The test, which is still in the developmental stage, obviously hasimportant practical application in the early identification of the non-pregnant cow inthe luteal phase after an unsuccessful insemination; thus the cow can be treated withPGF2α to induce a premature estrus, when it can be rebred, saving time.

2-Assay of pregnancy-specific protein B.This protein has been identified in the maternal serum of cows from 24 days of gestation; the concentration is measured by radio-immunoassay. It is secreted by thebinucleate cells of the trophoblastic ectoderm, and thus its presence can be used to confirm pregnancy. However, since it has a long biological half-life it can also be identified in serum for many weeks postpartum; for the same reason, false positives can occur after embryonic or fetal death. At present, it can only be measured byradioimmunoassay (RIA) but, with the development of suitable enzyme-linked immunosorbent assay (ELISA) methods, it could well become an ‘on farm’ diagnostic test.

3-Progesterone concentration in plasma and milk: Since the CL persists as a result of the pregnancy, if a blood sample is taken at about 21 days after the previous oestrus, progesterone levels remain elevated. If the cow is not pregnant and is close to or at oestrus then the progesterone levels will be low. Progesterone is very soluble in milk fat there were higher concentrations per unit volume in milk than in the blood or plasma. Progesterone concentrations in the milk were assayed using radio-immunoassay; The reasons for false negative results are: 1-mistaken identity of the animal either on the farm or in the laboratory. 2-milk storage problems due to excessive heat or ultraviolet light. 3-low progesterone production by the CL. 4-inadequate mixing of milk so that a low fat sample is obtained


The reasons for false positive results are: 1-cows with shorter than average interoestrus intervals, i.e. 18 days. When milk samples are taken 24 days after service or artificial insemination, if the cow is not pregnant she will already be in the early luteal phase of the next cycle. 2-embryonic death, if it occurs after the day when the milk was collected. 3-luteal cysts which produce progesterone. 4-incorrect timing of insemination. Thus if a milk sample is taken 24 days after the cow was incorrectly inseminated in early or mid dioestrus, and the intervening oestrus has not been observed, then she will be in the subsequent dioestrus with a functional CL and elevated milk progesterone concentrations. 5-pathological prolongation of the life span of the CL such as persistent CL.


4-Oestrone sulphate in milk: Oestrone sulphate is quantitatively one of the major oestrogens in the milk of pregnant, lactating cows. During gestation the concentration increases gradually so that after day 105 it is present in the milk of all pregnant animals, whereas in nonpregnant individuals it is low or undetectable; the source of the hormone is the fetoplacental unit.


III- Clinical methods:1-Transrectal palpation:-Palpation of the amniotic vesicle; this method involves the palpation of the amnion towards the end of the first month of pregnancy. The amniotic saccan be felt as a distinct, round, turgid object 1–2 cm in diameter floating in theallantoic fluid. The vesicle should not be compressed directly but gently pushedbackwards and forwards.-Palpation of the allantochorion (membrane slip) The allantochorion will eventually be identified as a very fine structure as itslips between the thumb and finger .-Unilateral cornual enlargement; unless there are twin conceptuses, one in each horn, it ispossible to detect a difference in the size of the two horns. This is largely due to thepresence of fetal fluids, in particular allantoic fluid, which gives the uterine horn afluctuating feel with good tone.


-Palpation of the early fetus; At about 45–50 days of gestation the amniotic sac becomes less turgid, and it is sometimes possible to palpate directly the small developing fetus .This should be done with care.-Palpation of caruncles/cotyledons (placentomes); Caruncles/cotyledons first become recognizable by rectal palpation at 10–11 weeks as roughened elevations when the fingers are passed back and forth over the surface of the enlarged gravid horn. From about 3 months they can be identified as discrete structures in the midline, about 8–10cm in front of and over the pelvic brim, by pressing down upon the uterine body and base of the horns. In the early stages it is difficult to identify them as distinct, individual structures.-Hypertrophy of the middle uterine artery and development of fremitus; the artery runs in the road ligament, along a tortuous course, passing downwards, forwards and towards the midline over the pelvic brim close to the junction between pubis and ileum. -Palpation of the late fetus; Palpation of the fetus, either per rectum or by abdominal ballottement, is diagnostic of pregnancy.-.

Accuracy of pregnancy diagnosis by rectal palpation; The most likely reason for making a false positive diagnosis is subsequent embryonic or fetal death. Other reasons for false positives are incomplete uterine involution, pyometra, mucometra and hydrometra and failure to retract the uterus. The reasons for false negatives are incorrect recording of the date of service or artificial insemination, so that when the cow is examined she is pregnant but a cycle length earlier than expected and incomplete retraction of the uterus.


2-Vaginal examination:Examination may be manual or visual. In the latter case, an illuminated speculum is used. The condition of the vaginal mucous membrane does not afford definite clinical evidence of pregnancy, for the degree of ‘dryness’ and blanching which occur during the dioestrus period are very similar to those of pregnancy. It is to the external os of the cervix that attention is directed. During pregnancy the secretion of the cervical glands becomes gelatinous and tough, forming a plug for sealing the canal. In many cases the seal covers or protrudes from the external os. It has developed by day 60.

IV-Ultrasonographic methods:

Detection of pregnancy by ultrasonography used transrectal probe 7.5 MHz; depth 4.5 cm Fetus 60 days old.

Two horn of non pregnant cow by using transerctal probe 7.5 MHz

Detection of pregnancy by ultrasonography used transabdomn probe 3.5 MHz; depth 18.3 cm Fetus 133 days old.
heart


Detection of pregnancy by ultrasonography used transabdomn probe 3.5 MHz; depth 18.3 cm Fetus 135 days old.
placentome



Detection of pregnancy by ultrasonography used transabdomn probe 3.5 MHz; depth 18.3 cm Fetus 133 days old.
Ribs


V-Fetal electrocardiography. Fetal electrocardiography has been noted as a method of pregnancy diagnosis. It is not applicable before 5 months of gestation, but it might have application for the diagnosis of multiple pregnancies.


PREGNANCY AND ITS DETECTION IN THE EWE AND DOE:I-Management methods; Traditionally the method used by shepherds is the observation that ewes, which have been marked by a ‘keeled’ or ‘raddled’ ram, fail to be marked again within 16–19 days. Beyond 100 days of gestation the fetus may be palpated through the abdominal wall, and development of the udder is then obvious in primipara. The best way to ballotte the fetus is to have the ewe standing normally and to lift the abdomen repeatedly immediately in front of the udder; the fetus can be felt to drop on to the palpating hand.

II- Clinical methods1-Rectal Abdominal Palpation:This is a simple, cheap, and quick technique to diagnose pregnant ewes. It consists of inserting a lubricated rod into the rectum of a ewe that is lying on its back. One hand is placed on the abdomen of the ewe while the other hand manipulates the rod toward the hand that is over the abdomen. The technique is not indicated for early pregnancy diagnosis because the sensitivity is reportedly low (59 percent sensitivity between days 21 to 55). With the advance of gestation, at 85 to 109 days after breeding, it has a reported accuracy of 100 percent. However, some authors haven’t had the same success rate, indicating that operator experience with this technique is very important. A serious disadvantage of the technique is the risk of rectal injury to the ewe and the induction of abortion.

2-Transabdominal Palpation:The presence of a fetus is detected by manual palpation of the ewe’s abdomen. This is more easily accomplished with the ewe in the seated position. The operator’s hands are placed on both sides of the abdomen. With one hand pressing on one side of the abdomen, the fingers of the other hand palpate the abdomen in search of fetuses. The presence of lambs is felt as a free floating mass that bounces against the operator’sfingers. Although simple and inexpensive, the technique requires training and is limited to the last two months of gestation. The accuracy of the technique varies with the experience of the operator, starting at 80 percent and reaching 90 percent in thin ewes that have been recently shorn. The accuracy can be increased if the method is used in association with other techniques such as udder examination.

3-Udder Examination (Wet and Dry Techniques): This is an indirect method of detecting pregnancy in ewes. It can be performed during late gestation and can have a high accuracy rate if associated with other techniques such as abdominal enlargement and transabdominal palpation. It is best performed during the last month of gestation when ewes start their udder development. This technique also yields the best results if the breeding (lambing) season is short otherwise the udder inspection needs to be performed twice with a three-to-four-week interval. At this stage the udder is firm and enlarged and feels warm. Colostrum can be milked at this stage to confirm pregnancy and differentiate from mastitis or fat open ewes that have been fed estrogenic rich clover. These animals have an enlarged udder that is soft and cold to the touch and their secretions can vary from a watery fluid to thick white milk. In contrast, colostrum should be thick and cream-colored or it can be thick and yellow with a honey appearance. At this stage, ewes identified as pregnant can be separated from the flock for adequate management. It is advisable to do a final check within the last week of the lambing season to identify/cull the ewes that did not conceive during the breeding season. This technique does not allow the determination of the lambing date or the number of fetuses.


III- Laboratory methods :1-Estimation of plasma progesterone:Estimation of progesterone concentrations from this time after service would be worthwhile. Values of progesterone in the plasma ≥7.5 ng/ml were indicative of pregnancy. In lactating ewes it is also possible to determine the progesterone levels in milk. Plasma and milk progesterone values in pregnant sheep 18–22 days after matingwere similar (3.7 ng/ml), whereas in non-pregnant ewes they were 1 ng/ml.2-Rosette inhibition tittiter IT) test; this is an established test for determining the immunosuppressive potential of antilymphocyte serum which has been applied todetermining the presence of an ‘early pregnancy factor’ (EPF) in ewes.

3-Vaginal biopsy the stratified squamous epithelium of the vaginal mucosa is sensitive to the hormonal changes that occur during the estrous cycle and pregnancy. There is no doubt that the difference in the histological appearance is greater between oestrus and pregnancy than between dioestrus and pregnancy. The diagnosis depends on the number of layers of vaginal epithelial cells, which in turn relates to the endocrine state; thus during pro-oestrus, when oestrogen is dominant, a rapid proliferation of the stratum germinativum occurs, so that at oestrus there are up to 20 layers. From the end of oestrus and throughout the luteal phase, when progesterone is dominant, the depth of vaginal epithelium falls, so that by day 11 or 12 there are only three or four irregularly arranged layers and only two or three layers in late dioestrus. With the onset of pregnancy progesterone domination continues, and by day 26 the typical histological picture is two parallel rows of epithelial cells with condensed darkly staining nuclei. This pattern persists until the final 3 weeks of gestation. Sections taken erroneously from the cervix or posterior vagina are unsatisfactory for diagnosis.



IV-Peritoneoscopy and laparoscopy; Some authors obtained 91% accuracy of pregnancy detection between 17 and 28 days by means of direct inspection of the uterus and ovaries with a laparoscope, using general anesthesia

V-Radiography: Both dorsoventral and lateral radiographs can be taken. Fetuses were detectable from 70 days of gestation.


VI-Ultrasonographic methods; the fetal pulse detector (Doppler) has been used to diagnose pregnancy in ewes, and two types of probe are available. The external probe is applied to the skin surface of the abdomen just cranial to the udder. The fleece in this region is sparse and with transmission gel applied to the end of the probe it is slowly moved over the surface. The ewe can be restrained either standing or sitting on her haunches. Characteristic sounds indicate the presence of the fetal heart (‘tack, tack, tack’) orvessels (‘swish, swish, swish’); the frequency greatly exceeds that of the mother’s heart rate, except in late gestation when the fetal heart rate is reduced. Between 40 and 80 days of gestation the accuracy of detection is no better than 60%. However, after 80 days, with a reasonable amount of practice, it is over 90% accurate and it takes an average 3 or 4 minutes per ewe to make a diagnosis. Using a rectal probe anaccuracy of 97% between 35 and 55 days after mating. A B-mode ultrasound sector transducer probe, using the Tran abdominal approach, has proved to be an accurateand rapid method of not only differentiating pregnant from non-pregnant ewes butalso accurately determining fetal numbers.

Detection of pregnancy by ultrasonography used transabdomn probe 3.5 MHz; Fetus 107 days old.
placentome
Uterine fluid


Detection of pregnancy by ultrasonography used transabdomn probe 3.5 MHz; Fetus 92 days old.
head
Vertebral column


Detection of pregnancy by ultrasonography used transabdomn probe 3.5 MHz; Fetus 107 days old.
Heart
Ribs

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رفعت المحاضرة من قبل: Yehia Vet
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