Induced abortion in cattle

Several procedures were used to abort cattle during the second and third trimesters of gestation. The treatment to abortion interval was better (P<0.05) when dexamethasone trimethyiacetate (DTMA) injections repeated at either 6 or 4 day intervals than when a single injection of DTMA was followed 6 days later by the administration of stilboestrol. The treatment to abortion interval was not significantly shorter when DTMA was repeated after 4 days rather than 5 days (0.10<P>0.05). Prostaglandin F_2α produced abortion 1 to 4 days following direct administration into the foetai fluids.Peripheral plasma progesterone concentration had a tendency to rise immediately following the second injection of DTMA given at a 6 day interval. This was followed by a decline. Two injections of DTMA given at 4 day intervals resuited in a decline in progesterone concentration. Abortion occurred when plasma progesterone concentrations were about 1 ng/ml in cows treated with DTMA. In cows treated with prostagiandin F_2α the plasma progesterone concentration fell rapidly within one day of administration to approximately 2 ng/ml, at which concentration abortion took place.     

Pregnancy-specific protein B and progesterone concentrations in French Alpine goats throughout gestation.

The 34 French Alpine dairy goats originated from a single flock and were artificially inseminated 44 h after synchronization of oestrus. They were bled daily at the jugular vein from 15 to 27 days after AI. An early pregnancy diagnosis by RIA of progesterone concentration was performed 21 days after AI. In pregnant goats (greater than 1.5 ng progesterone/ml) daily sampling was extended until 30 days after AI and, from those, 9 were bled every 2 weeks until the end of pregnancy and at 50 and 63 days post partum. Pregnancy-specific protein B (PSPB) was also assayed. The kidding rate was 67.6% (23/34). PSPB concentrations (ng/ml) in pregnant goats were significantly different from those of non-pregnant goats at 24 days after AI (0.82 +/- 0.18 vs 1.78 +/- 0.19; mean +/- s.e.m.) and rose to 40 ng/ml at the end of pregnancy. From Day 25 and throughout gestation, females with 2 fetuses had higher PSPB concentrations than did those with a single fetus (P less than 0.05). In the 2 goats exhibiting late embryonic mortality according to progesterone concentrations, one had a PSPB profile very similar to those of pregnant goats until 30 days while the other did not show any elevation of PSPB concentration. It is concluded that PSPB profiles in goats are similar to those found in cows throughout pregnancy and that PSPB RIA may be useful for pregnancy diagnosis or diagnosis of late embryonic mortality.     

Effect of endogenous and exogenous progesterone on the oestradiol-induced LH surge in dairy cows

Four cows released an LH surge after 1.0 mg oestradiol benzoate administered i.m. during the post-partum anoestrous period with continuing low plasma progesterone. A similar response occurred in the early follicular phase when plasma progesterone concentration at the time of injection was less than 0.5 ng/ml. Cows treated with a progesterone-releasing intravaginal device (PRID) for 8 days were injected with cloprostenol on the 5th day to remove any endogenous source of progesterone. Oestradiol was injected on the 7th day when the plasma progesterone concentration from the PRID was between 0.7 and 1.5 ng/ml. No LH surge occurred. Similarly, oestradiol benzoate injected in the luteal phase of 3 cows (0.9-2.1 ng progesterone/ml plasma) did not provoke an LH surge. An oestradiol challenge given to 3 cows 6 days after ovariectomy induced a normal LH surge in each cow. However, when oestradiol treatment was repeated on the 7th day of PRID treatment, none released LH. It is concluded that ovaries are not necessary for progesterone to inhibit the release of LH, and cows with plasma progesterone concentrations greater than 0.5 ng/ml, whether endogenous or exogenous, did not release LH in response to oestradiol.     

Effect of fetal mass, number and stage of gestation on pregnancy-specific protein B concentrations in the bovine

In this study we characterized the peripheral plasma pregnancy-specific protein-B (PSPB) profile throughout gestation and examined the effect of stage of gestation, fetal mass and number on this profile in Holstein cows after non surgical embryo transfer. Cows (n = 12) were divided into 2 groups: Group 1 = single embryo recipient cows (n = 5), Group 2 = twin-embryo recipient cows (n = 7). Blood was collected approximately every third day from Day 0 (Day 0 = first day of standing estrus), then daily for the last 10 d of gestation, and sampling was stopped 1 d post partum. Two twin-embryo recipient cows had abnormal pregnancies; therefore, their data were excluded from the group. The time trend concentrations of plasma PSPB were significantly affected by the stage of gestation (P < 0.001) and fetal number (P < 0.001). In both groups PSPB increased gradually, with the mean levels being significantly higher (P < 0.01) in the twin-bearing group from Day 50 onwards (0.7 +/- 0.2 vs 9.2 +/- 4.5 ng/ml, singleton and twin-bearing cows, respectively) except for Day 10 pre-partum. By mid-gestation (Day 140), mean PSPB levels increased in the singleton (P < 0.001) cows by thirty-fold (21.2 +/- 3.2 ng/ml) as opposed to a ten-fold (98.4 +/- 13.2 ng/ml) increase in the twin-bearing (P < 0.001) group. The mean PSPB concentrations between Days 30 to 20 prepartum dramatically increased by about 700 to 200% in singleton (128.8 +/- 46.3 to 745.6 +/- 66.7 ng/ml) and twin-bearing cows (375.6 +/- 130.4 to 861.5 +/- 127.9 ng/ml), respectively. The PSPB levels between Day 10 prepartum to parturition were significantly higher (P < 0.001) in the twin-bearing group than in the singleton group (745.6 +/- 66.7 to 1627.4 +/- 238.9 ng/ml vs 861.5 +/- 127.9 to 3103.0 +/- 643.0 ng/ml in singleton and twin-bearing groups, respectively). Calf birthweight was correlated (P < 0.01) to peripheral PSPB concentration in singleton cows; however, this relationship decreased with the subsequent increase in fetal number. Cows giving birth prematurely to stillborn calves or to a schistosomus reflexus calf exhibited abnormal PSPB profiles. These results indicate that peripheral PSPB levels are correlated to the stage of gestation and fetal number. In addition, the peripheral pattern of PSPB is a valuable guage for predicting fetoplacental viability.     

Detection of pregnancy by radioimmunoassay of a novel pregnancy-specific protein in serum of cows and a profile of serum concentrations during gestation

The development of a double antibody radioimmunoassay for a bovine pregnancy-specific protein (pregnancy-specific protein B; PSPB) is presented. By means of this assay, PSPB could be measured in serum of pregnant cows. Five dairy cows were bled throughout gestation to measure serum levels of PSPB. Serum concentrations (means +/- SE) exceeded 1 ng/ml by 30 days postbreeding and increased gradually through three months (9 +/- 0.6 ng/ml), six months (35 +/- 6 ng/ml), and nine months (150 +/- 75 ng/ml) of gestation. Maximum levels of PSPB (542 +/- 144 ng/ml) were reached two days before parturition and then steadily declined to less than 78 ng/ml by 21 days postpartum. In 21 cows bled daily from 15 through 30 days postbreeding, PSPB could be measured in a few cows before and in most cows by 24 days after breeding. In a commercial herd of 102 beef cows, the assay could detect pregnancy earlier and more accurately than the routine method of rectal palpation. This radioimmunoassay measures a unique antigen that, for the first time, provides a serological method for detecting pregnancy in cows.     

Plasma Progesterone Assays in Superovulated Cattle

Plasma progesterone was measured in 14 normally cycling heifers and cows subjected to non-surgical recoveries of embryos. A radioimmunoassay (RIA) method was used for progesterone determination. The average progesterone concentration increased from 7.5 to 11.6 ng/ml in 8 of the animals following treatment with PMSG on day 8–12. Six animals had a decrease from 5.0 ± 2.1 to 3.9 ± 2.5 ng/ml. The overall increase was from 6.4 ± 2.7 ng/ml to 8.3 ± 4.8 ng/ ml. Prostaglandin F2a-analogue (cloprostenol) treatment resulted in a sharp decrease in plasma progesterone followed by a rapid increase to an average of 46.8 ng/ml on day 16. A high degree of variability in this peak value was observed, and it was not correlated with the number of corpora lutea. The superovulatory cycle was generally prolonged. The heat following the superovulatory treatment was silent, and a typical ovarian resting period was observed during which the progesterone concentration remained low and the ovaries small.     

Peripheral plasma progesterone and utero-ovarian prostaglandin F concentrations in the cow around parturition

The concentration of prostaglandin F in utero-ovarian venous plasma and progesterone in jugular venous plasma were determined by radioimmunoassay in 3 cows over the last 2–3 weeks of gestation. Utero-ovarian prostaglandin F concentrations did not show any consistent pattern in two of three cows until 48–72 h before term when the levels rose sharply from 1 ng/ml to a maximum 4–9 ng/ml during labour. The concentration of progesterone in jugular venous plasma tended to fall gradually over the last 20 days of gestation with a further fall occurring 48-36 h before delivery.In two other cows at around 240 days of gestation the concentration of plasma progesterone in ovarian venous plasma was 50 to 150 times the concentration of progesterone in uterine or jugular venous plasma. It is concluded from these results that the ovaries are the major source of progesterone in cows during late pregnancy. The findings also suggest that prostaglandin F may be the luteolytic factor responsible for the sharp decline in plasma progesterone concentrations over the last 48-36 h preceding parturition.     

Progesterone profile in buffaloes during various stages of oestrous cycle using radioimmunoassy technique

Investigation were carried out to study the norms of progesterone concentration in the blood serum of buffaloes during various phases of oestrous cycle. Twenty four animals (12 heifers and 12 cows) were used. The blood serum samples were stored at -20 degrees C until processed for progesterone assay. The progesterone concentrations were measured by the radioimmunoassay technique. The progesterone levels were 0.360 +/- 0.062 and 0.334 +/- 0.066 ng/ml on the day of oestrus in buffalo-heifers and buffalo-cows, respectively. The values were around 1 ng/ml till day 6, followed by a gradual increase to a peak average value of 4.888 +/- 0.399 and 5.119 +/- 0.415 ng/ml on day 15 of the cycle in heifers and cows, respectively. Thereafter, the progesterone concentration fell abruptly to a level similar to that at oestrus. The mean progesterone value a day before oestrus was 0.488 +/- 0.067 and 0.577 +/- 0.053 ng/ml in buffalo-heifers and buffalo-cows, respectively. The mean progesterone concentration of different days of the cycle (except day 16) did not differ significantly (P / -0.01) between heifers and cows.     

Efficacy of PGF(2alpha) to synchronize estrus in water buffalo cows (Bubalus bubalis) is dependent upon plasma progesterone concentration,corpus luteum size and ovarian follicular status before treatment

This study was conducted to identify factors affecting PGF(2alpha) efficacy to synchronize estrus in water buffalo cows. After detection of a corpus luteum (CL) by rectal palpation, cows were treated (im) with dinoprost (12.5, 25 or 50mg) or D(+) cloprostenol (75, 150 or 300 microg) in a total of 66 treatments. Blood samples were collected 0, 24 and 48 h after treatment and ultrasound examinations and observations for estrus were performed daily to the day of ovulation or to 6 days after treatment. No PGF(2alpha) dose-response pattern was observed and overall rates of luteal regression (progesterone <1.0 ng/ml at 48 h), estrus, no detected behavioral estrus with ovulation occurring, and ovulation were 71.2, 36.4, 19.7 and 54.5%, respectively. To analyze plasma progesterone concentrations and ovarian dynamics, cows were divided in three groups according to their response to treatment. Cows that failed to have ovulations from a follicle after treatment (Group A, n = 30) had (P < 0.05) a lower plasma progesterone concentration (2.98 ng/ml) and smaller CL area (CLA; 187.3 mm(2)) before treatment as compared with cows that had an ovulation from a follicle (4.43 ng/ml and 223.7 mm(2), respectively; Groups B and C, n = 36). In cows that failed to ovulate, plasma progesterone concentration decreased in the first 24 h, but did not decline further and was >1.0 ng/ml 48 h after treatment. Moreover, no significant change in CLA after treatment was detected, indicating that treatment induced only partial luteolysis. In cows that ovulated, plasma progesterone concentration and CLA decreased continuously from treatment to ovulation (consistent with complete luteolysis). Threshold values of 2.8 ng/ml for plasma progesterone concentration and 189 mm(2) for CLA were identified as the best predictors of ovulation before treatment (83.3 and 80.6% sensitivity and 58.6 and 65.5% specificity, respectively, with positive and negative predictive values around 71%). When the origin of the ovulatory follicle was investigated, the interval from treatment to ovulation was shorter (91.9 versus 113.3 h; P < 0.05), and the ovulatory follicle had a slower growth rate (1.02 versus 1.55 mm per day; P < 0.005), a lesser increase in diameter from treatment to ovulation (4.7 versus 8.0 mm; P < 0.001), and a greater maximum diameter (13.2 versus 12.1 mm; P < 0.05) in cows that ovulated from the largest follicle present in the ovary before treatment (Group B, n = 27) compared with cows that ovulated from the second largest follicle present in the ovary before treatment (Group C, n = 9). In summary, the efficacy of PGF(2alpha) for causing luteolysis and synchronizing estrus and ovulation in buffalo cows was dependent upon plasma progesterone concentration, CL size and ovarian follicular status before treatment.     

Genetic and environmental factors influencing first service conception rate and late embryonic/foetal mortality in low fertility dairy herds

The objective of this study was to identify factors affecting variation in conception rate to first artificial inseminations (AI) (CR: number of pregnant cows on D80-100/inseminated cows) and the incidence of embryonic/foetal loss (LEM) between 21 and 80 days of pregnancy (number of cows non-pregnant on D80-100/pregnant on D21) in 44 low fertility dairy herds of the west-central region of France. Reproductive status was assessed using progesterone milk concentration on D0 = Day of AI and D21-24, plasma PSPB concentration on D30-35, rectal palpation on D80-100 and observed return to oestrous. The final data set contained 1285 Prim'Holstein cows, 5.0% (64/1285) were inseminated in the luteal phase (progesterone > or = 3 ng/ml on D0), 61.3% (787/1285) were pregnant on D21-24 (progesterone < 3 ng/ml on D0 and > or = 5 ng/ml on D21-24), 15.4% lost their embryo/foetus between D21-24 and D80-100 (198/1285) and 45.8% (589/1285) were pregnant on D80-100. The incidence of late embryonic/foetal loss (LEM) was 25.2% (198/787). Multivariate logistic regression models including the random herd effect were used to analyse the relationship between AI centre, AI sire, cow's sire, parity, interval between calving and AI, milk production, milk protein content, body condition score (BCS) on D0, season of calving, season of AI, estimated genetic index on CR and LEM incidence. CR was significantly related to parity (p < 0.05), milk production after calving (p < 0.05) and estimated genetic value (p < 0.01). A significant difference in CR was observed for calving to AI interval > or = 70 days versus > or = 90 days, but the overall effect of the interval was not significant (p = 0.11). LEM incidence was affected by period of AI (p < 0.05), milk production (p < 0.05) and BCS (p < 0.05), but was not related to estimated genetic index. In conclusion, in these low fertility herds, the incidence of LEM was high and 25% of the cows lost their embryo after 21 days of pregnancy. LEM was affected by specific factors (season, BCS), which were not related to CR. The absence of a relationship between estimated genetic index and LEM in spite of its effect on CR indicates that estimated genetic merit has a greater effect on early embryonic loss or fertilisation failure than on later stages of embryo development.     

Ovarian and endocrine responses and reproductive performance following GnRH treatment in early postpartum dairy cows

At calving forty-eight Holstein and Guernsey cows were assigned according to age and breed to one of six postpartum periods (1 or 2, 3 or 4, 5 or 6, 7 or 8, 12 or 13 and 18 or 19 days postpartum). Thirty-six of the cows (6 cows per postpartum period) received a single intramuscular injection of 100 μg GnRH. The other twelve cows (2 cows per postpartum period) served as controls and received a single intramuscular injection of the carrier vehicle for GnRH.Four of 36 cows administered GnRH and three of the 12 control cows ovulated by the day following treatment. Four of the cows were 12 or 13 days postpartum (1 control and 3 GnRH treated) and three were 18 or 19 days postpartum (2 controls and 1 GnRH treated). Six of the seven cows that ovulated the day following treatment had a follicle > 1.0 cm the day prior to treatment. Follicular growth was detected in the earlier postpartum periods but ovulation the following day was not detected for either control or GnRH treated cows. Following estrus or silent estrus, plasma progesterone concentrations increased to about 4 ng/ml on day 13. However, in cows ovulating the day following GnRH treatment, plasma progesterone declined from about 3 ng/ml on day 9 to approximately 1 ng/ml on day 13 postestrus. In addition, LH in plasma was higher (P < .01) ? through 13 days following estrus or silent estrus in cows ovulating the day after GnRH treatment in comparison to cows during the first or subsequent postpartum estrous cycles.In summary, in addition to days postpartum other factors including follicular development and maturity are probably involved in GnRH induced ovulation.     

Reproductive hormones associated with the ovarian cyst response to GnRH

Eighteen cows with ovarian cysts were administered 100 mug of GnRH and bled prior to treatment, at half hour intervals for 4 hours posttreatment and on days 1, 5 and 9 posttreatment. Blood plasma was analyzed for estradiol-17beta, progesterone and LH by radioimmunoassay. Response to treatment was recorded as positive if ovulation was detected within 30 days posttreatment. Fourteen cows (78%) initiated ovarian cycles by 30 days posttreatment. Mean pretreatment concentrations of estradiol-17beta, progesterone and LH and the GnRH induced LH release were not different for positive or no response cows. However, all seven cows that had pretreatment progesterone concentrations greater than 1.0 ng/ml had a positive response to treatment. Eight of the remaining eleven cows had a progesterone response (mean progesterone concentrations on days 5 and 9 posttreatment) greater than 1.0 ng/ml; seven had a positive response to treatment. In summary, most cows with ovarian cysts administered GnRH will initiate ovarian cycles within 30 days if: 1) pretreatment progesterone concentrations are greater than 1.0 ng/ml or 2) if progesterone response is greater than 1.0 ng/ml.     

Evaluation of an on-farm blood progesterone test for predicting the day of parturition in cattle

An on-farm blood progesterone enzymeimmunoassay (EIA) was evaluated as a diagnostic test to predict the time of calving within a 24-hour period in near-term dairy cows. Blood samples were taken daily from 45 cows beginning 5 days prior to their expected due dates until calving, and plasma was stored at -20 degrees C until all cows had calved. The EIA test was performed on frozen-thawed plasma samples, and progesterone concentrations were determined to be low (positive test for calving within 24 hours) or high (negative test for calving within 24 hours). Sensitivity, specificity and predictive value of the EIA to accurately determine parturition within 24 hours were 86.7, 90.8 and 75.0%, respectively. The EIA correctly predicted the day of parturition in 168 of 187 (89.8%) plasma samples. Ten additional cows were similarly monitored except the EIA was performed on whole blood immediately after collection, and the sensitivity, specificity and predictive value of the test were 80.0, 97.6 and 88.9%, respectively. The day of parturition was correctly predicted in 49 of 52 (94.2%) whole blood samples. More than 95% of the cows calved within 24 hours when their plasma progesterone reached < 1.3 ng/ml. When results of the EIA were compared with those of a radioimmunoassay (RIA), the EIA findings were used to correctly classify 190 of 232 (81.9%) plasma samples as having low (< 2.0 ng/ml) or high (>/= 2.0 ng/ml) concentrations of progesterone. The EIA test was found to be a quick, practical means of estimating progesterone concentrations in bovine plasma or whole blood and was a useful test for predicting the day of parturition in cows.     

Changes in ovarian follicles following acute infection with bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) has been associated with several reproductive problems in cattle, including poor fertility, early embryonic deaths, abortion and congenital anomalies. Little is known about the cause of poor fertility in cows acutely infected with BVDV. The purpose of this study was to identify changes in ovarian function following acute infection with noncytopathic BVDV. The ovaries of 5 BVDV sero-negative and virus-negative pubertal heifers were monitored daily for 4 consecutive estrous cycles. The position and diameter of all follicles (> 5 mm) and luteal structures were recorded. Daily plasma samples were collected to measure peripheral progesterone and estradiol levels. Each heifer was infected intranasally with noncytopathic BVDV following ovulation of the second estrous cycle. The maximum diameter and growth rate of dominant anovulatory and ovulatory follicles were significantly reduced following acute BVDV infection. Similarly, the number of subordinate follicles associated with both the anovulatory and ovulatory follicle was reduced following infection. There were no significant differences in other follicle or luteal dynamic parameters or in peripheral progesterone or estradiol levels. Ovarian follicular growth was different during the first 2 estrous cycles following acute infection with BVDV when compared with the 2 estrous cycles preceding infection. These differences may be important in explaining reduced fertility in herds with acute BVDV infection.     

Effect of exogenous progesterone on prostaglandin F2 alpha release and the interestrous interval in the bovine

The present study was developed to determine if administration of progesterone, early in the estrous cycle of the cow, stimulated an advanced pulsatile release of PGF2 alpha from the uterine endometrium resulting in a decreased interestrous interval. Twenty-three cyclic beef cows were randomly assigned to receive either sesame oil or progesterone (100 mg) on Day 1, 2, 3 and 4 of the estrous cycle. Peripheral plasma concentrations of progesterone and the metabolite of prostaglandin F2 alpha, 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) were measured by radioimmunoassay. Administration of exogenous progesterone increased peripheral plasma concentration of progesterone in treated (3.67 ng/ml) compared to control (1.28 ng/ml) cows from Day 2 through 5 of the estrous cycle. Progesterone administration shortened the interestrous interval (16.7 d) compared to controls (21.6 d). The shortened interestrous intervals in treated cows resulted from an earlier decline in peripheral plasma progesterone. Decline of peripheral plasma progesterone concentrations is coincident with an increased pulsatile release of PGFM in both progesterone treated and control cows. Results indicate that administration of exogenous progesterone stimulates an earlier maturation of endometrial development, causing an advanced release of PGF2 alpha which shortens the interestrous interval of the cow.     

Plasma oestradiol and progesterone during early pregnancy in the cow and the effects of treatment with buserelin

We have monitored plasma concentrations of oestradiol and progesterone after insemination in dairy cows, and investigated the effects of injection with 10 μg of the gonadotrophin-releasing hormone (GnRH) analogue buserelin, a treatment known to result in an improvement in conception rate. Animals were injected intramuscularly on Day 12 after insemination with 2.5 ml of either control saline (n = 29) or buserelin (n = 26). Blood samples were collected from Day 8 to Day 17 and milk samples from the day of insemination until Day 30. On the basis of milk progesterone profiles, in the control group 15 cows remained pregnant (control pregnant) and 11 underwent luteolysis (control not pregnant), whereas in the treated group 13 cows remained pregnant (treated pregnant) and 13 underwent luteolysis (treated not pregnant). Three cows were excluded from the control group owing to high progesterone at insemination or failed ovulation. In both the control and treated groups mean plasma progesterone concentration was significantly (P < 0.05) lower in non-pregnant cows than in pregnant ones from Day 12 post-insemination. However, no significant effect of buserelin treatment on plasma progesterone concentration was detected. In the control group the plasma oestradiol concentration was similar in the pregnant and non-pregnant cows. In the treated group, plasma oestradiol concentration in the non-pregnant cows was similar to that in the control group, whereas in the treated pregnant cows the plasma oestradiol concentration showed a significant (P < 0.05) decline after treatment. As oestradiol is known to stimulate the development of the luteolytic mechanism at this time, we suggest that buserelin is acting to reduce the strength of the luteolytic drive in some cows, thus improving the chance of the embryo being able to prevent luteolysis.     

Intrauterine instillation of prostaglandin F2ALPHA IN EARLY PREGNANCY.

Intrauterine PGF2alpha (5mg) was administered for termination of early pregnancy in 14 healthy volunteers. With 11 complete abortions, the efficiency rate of this technique is below conventional methods. In addition, the incidience of infection was high occuring in 12 out of 14 subjects. Because of persistent bleeding, six patients underwent a dilatation and curettage. Other significant side effects included transient hypertension, pain, nausea and restlessness. In the patients with a complete abortion, the mean plasma progesterone concentration fell 37% after 8 hours post PGF2alpha instillation and 90iod and 75% over the next 14 days.     

Peripheral plasma progesterone concentration in zebu (Bos indicus) cows during pregnancy

Plasma progesterone concentrations were determined weekly during gestation averaging 283 +/- 2 d in Ethiopian zebu (Bos indicus) cows. Mean progesterone levels increased from 0.2 +/- 0.1 ng/ml at oestrus (service) to 3.1 +/- 1.6 ng/ml on d 7 and 8.1 +/- 2.1 ng/ml on d 21. Progesterone levels remained elevated throughout pregnancy. Hormone concentration differed significantly between cows (P less than 0.001) and with the wk of pregnancy (P less than 0.05); it tended to be higher during the last trimester of pregnancy. Mean levels dropped sharply to below 1 ng/ml during the last wk of pregnancy with considerable variation (C.V. = 39 to 63%) among cows. These data indicate that pregnancy in Ethiopian zebu cows can be reliably diagnosed by determining circulatory plasma progesterone levels.     

Abortifacient and endocrine effects of metergoline in beagle bitches during the second half of gestation

The purpose of this study was to investigate the abortifacient effects of high doses of metergoline when administered to pregnant beagle bitches during the second half of gestation and to define the endocrine effects of this treatment as represented by plasma progesterone and estradiol concentrations. Previously, metergoline had been shown to be incompletely luteolytic and induced abortion in only one of eight pregnant bitches when 0.4-0.5 mg/kg were administered twice daily for 5 days from Days 18 to 20 of diestrus. Nine pregnancies in six beagle bitches were used for the present study. Three bitches were treated in each of two consecutive pregnant cycles. Metergoline was administered at a dose of 0.6 mg/kg per os twice daily, starting on Day 28 after the cytological onset of diestrus. Abortion was induced in eight of the nine treated pregnancies and started after 3-23 days of treatment (mean 12.5 days, S.D. 6.4 days). The abortions were completed within 0.5-8 days (mean 2.2 days, S.D. 2.7 days). There were no side effects associated with metergoline treatment and none of the abortions was associated with complications that required intervention. In the single bitch that did not abort, an ovarian granulosa cell tumor was discovered when the single fetus had to be removed surgically at term. Plasma progesterone concentrations declined after the start of metergoline administration in all pregnancies but levels below 4.8 nmol/l were required for successful abortions. Plasma estradiol concentrations showed a tendency to decline and fluctuate concurrently with the plasma progesterone levels. However, suppression of plasma estradiol concentrations by metergoline was not as complete as the suppression of progesterone and did not seem a prerequisite for abortion. The hormone profiles and treatment period required for abortion tended to be similar for both cycles of the three bitches that were treated during two consecutive pregnancies. This suggests a bitch effect on the factors that determine the efficacy of metergoline to induce abortion. The large variation and length of the treatment period that was required until abortion commenced was probably related to the relatively early start of treatment compared to other studies. The results of this investigation suggest that, similar to other prolactin suppressing ergot derivatives, metergoline causes complete luteolysis and can be used to reliably induce abortion only during the last 3 weeks of gestation.     

Factors affecting plasma progesterone in the early fetal period in high producing dairy cows

The aim of the present study was to determine whether certain animal- or management related factors could affect plasma progesterone concentrations on Day 42 of gestation in high producing dairy cows. Factors affecting early fetal loss were also analyzed. The study population was comprised of 199 pregnant cows classified as having high (> or =9 ng/ml) or low (<9 ng/ml) plasma progesterone concentrations. Through logistic regression procedures it was determined that, based on the odds ratio, cows with two or more corpora lutea were three times more likely to have high progesterone concentrations than cows with a single corpus luteum. Low producing cows during the warm season were 2.86 times more likely to have high progesterone concentrations than the remaining cows. Primiparous cows with high concentrations (>4 ng/ml) of pregnancy associated glycoprotein-1 (PAG-1) were 2.73 times more likely to have high progesterone concentrations than the remaining cows. Of the 199 pregnancies, 25 (12.6%) suffered early fetal loss: 22/136 (16.2%) during the warm season and 3/63 (4.8%) during the cool season, all in cows without additional corpora lutea. Based upon the odds ratio, cows without an additional corpus luteum were 3.67 times more likely to suffer fetal loss during the warm season than during the cool season. Our results indicate that milk production, the presence of two or more corpora lutea and plasma PAG-1 concentrations can affect plasma progesterone concentrations at the onset of the fetal period. The presence of an additional corpus luteum strongly diminished the risk of early fetal loss during the warm period.