Low Progesterone Concentrations Research Articles

Spironolactone metabolite causes falsely increased progesterone in the Abbott Architect immunoassay

BackgroundImmunoassays are important for routine clinical testing and medical diagnosis. However, they are limited by cross-reactivity especially at low analyte concentrations. There is a critical need to investigate compounds that can interfere with immunoassays. Herein, we describe the identification of canrenone, a spironolactone metabolite that falsely increases progesterone concentrations on the Abbott Architect i2000 Immunoassay. MethodsSerum samples and assay diluents were spiked with spironolactone or canrenone and progesterone concentrations were measured on the Architect i2000 and Immulite XPi immunoassay platforms. Blood samples from patients taking spironolactone were analyzed with liquid chromatography-tandem mass spectrometry to evaluate the intrinsic response of progesterone concentrations to the presence of canrenone. ResultsWe measured approximately 10-fold higher progesterone concentrations on the Abbott Architect i2000 compared to reference immunoassay analyzers (Siemens Immulite XPi and Roche Cobas e601/602), suggesting an analytical error which is unique to the Architect i2000 antibody and/or assay conditions. By measuring serum progesterone after addition of spironolactone or canrenone to serum samples, we found that canrenone falsely increased progesterone on the Architect i2000 immunoassay. However, this interference was more pronounced at low serum progesterone concentrations. Moreover, a strong positive correlation was seen between canrenone and measured serum progesterone concentrations. ConclusionsOur investigations are important for individuals who require progesterone measurements using the Architect i2000 immunoassay, especially because it is unlikely for clinicians to order canrenone measurements alongside progesterone measurements for individuals taking spironolactone. Further research is needed to determine whether canrenone can influence progesterone measurements on other immunoassay systems.

Progesterone concentrations on blastocyst transfer day in modified natural cycle frozen embryo transfer cycles

Research questionAre serum progesterone concentrations on the day of modified natural cycle (mNC) frozen blastocyst transfer (FET) without luteal phase support (LPS) associated with clinical pregnancy rate (CPR)? DesignData were collected between January 2019 and October 2022 as a sub-study of an ongoing randomized controlled trial assessing pregnancy outcomes in mNC-FET. The sub-study included all women (n = 209) randomized to mNC-FET without LPS at the time of data extraction. Participants were aged 18–41 years, had regular menstrual cycles and underwent mNC-FET treatment with single-blastocyst transfer. Associations between the serum progesterone concentration on the day of blastocyst transfer and CPR, pregnancy rate and pregnancy loss rate (PLR) were examined between groups with low and higher progesterone concentrations using the 25th and 10th percentiles as cut-offs. Multivariate logistic regression analyses were performed to adjust for potential confounding factors. ResultsProgesterone concentrations on the day of blastocyst transfer in mNC-FET without LPS ranged from 4.9 to 91.8 nmol/l, with the 25th and 10th percentiles at 29.0 nmol/l and 22.5 nmol/l, respectively. Serum progesterone concentrations did not differ between women with or without a clinical pregnancy (mean [SD] 38.5 [14.0] versus 36.8 [12.4] nmol/l; P = 0.350). Furthermore, the CPR, pregancy rate and PLR were similar in women with low or high progesterone concentrations when using the 25th or the 10th progesterone percentile as cut-off. Multivariate regression analyses showed no association between progesterone concentrations and CPR. ConclusionsNo association was found between progesterone concentration on the day of blastocyst transfer and pregnancy outcome in women undergoing mNC-FET without progesterone LPS.

Follicular dynamics in dairy sheep within and out of the breeding season employing high or low progesterone concentration in estrous cycle synchronization

Resumo A dinâmica folicular em ovelhas leiteiras é pouco compreendida. Neste trabalho foi avaliado a dinâmica folicular de ovelhas leiteiras, dentro e fora da estação reprodutiva observando o efeito de duas concentrações de progesterona (60 e 120mg) utilizadas em pessários vaginais na pré-sincronização. O experimento foi realizado nos meses de abril/maio e outubro/novembro, utilizando 40 ovelhas multíparas leiteiras hígidas, predominantemente da raça Lacaune, que foram submetidas a exames ultrassonográficos diários por via transretal. Na estação reprodutiva foram avaliados o número de ovulações (1,35 vs 1,05), o diâmetro(mm) do folículo ovulatório (5,97 vs 5,05), a duração da fase lútea (11 vs 9,14 dias) e a duração do ciclo estral (16,83 vs 16,6 dias) dentro da estação em comparação com fora da estação reprodutiva respectivamente. Fora da estação as ovelhas não apresentaram corpo lúteo no momento da inserção do pessário vaginal, caracterizando anestro. Mesmo com menor duração da fase folicular, o folículo ovulatório apresentou maior diâmetro na estação reprodutiva, sugerindo maior viabilidade e qualidade do oócito ovulado. A aplicação de progesterona exógena amplia a fase lútea na estação reprodutiva (11 vs 9,14 dias). O anestro observado fora de época sugere a necessidade de maior concentração de progesterona nos protocolos reprodutivos. Desta forma, é possível adaptar protocolos reprodutivos para diferentes épocas, sugerindo o uso de pessários vaginais com maior concentração de progesterona (120 mg) fora da estação reprodutiva. Os dados obtidos permitiram caracterizar a dinâmica folicular em ovelhas leiteiras, demonstrando suas diferenças em cada estação a partir do uso de diferentes doses de progesterona na pré-sincronização

Reproductive endocrinology, morphological traits, and sexual selection in a population of wild South African giraffes

Sex steroids are pervasive in mammals and evolutionarily conserved, but differences in the nuances of endocrine profiles characterize distinct species. Two sex steroids, testosterone and progesterone, feature prominently in the life history of mammalian taxa, but neither one has been analyzed from wild giraffes. Our study was designed to address this gap in knowledge by examining how these sex steroids are related to biological features and giraffe life history. We conducted the research at Rooipoort Nature Reserve a 44,000 ha private nature reserve in South Africa on a population of South African giraffes (Giraffa camelopardalis giraffa). Eleven adult giraffe cows and seven adult bulls were immobilized and various biological samples and morphological measurements were obtained. We analyzed both testosterone and progesterone using Ultra High Performance Liquid Chromotography – Tandem Mass Spectrometry (UHPLC-MS/MS). We found that non-pregnant females had lower progesterone concentrations than pregnant females and that those in the last trimester of pregnancy showed a slight drop in progesterone, as well as an increase in testosterone. Among males, chronological age was correlated with testicle size, testosterone concentrations, and ossicone volume. We propose that the progesterone decline functions partly to accelerate resumption of ovulation because giraffes become pregnant while lactating, and that the testosterone elevation provides an endocrine mileu for female defense of neonatal calves, given that lion predation is a major threat to calf survival. We suggest that male reproductive strategies are mediated by the age-related impacts of testosterone on growth in both body mass and ossicone volume as a consequence of sexual selection. We conclude by noting that the robust and solid ossicones of male giraffes function in mate competition as wedges that are used to topple opponents by raising their legs and placing them in an off-balanced position that can seriously injure them when falling to the ground.

Low progesterone concentration in early pregnancy is detrimental to conceptus development and pregnancy outcome in horses

High progesterone concentrations in the early luteal phase support pregnancy, whereas subphysiological progesterone concentrations delay embryonic development at least until placentation. In this study, fetal growth and development of pregnancy was investigated in pregnancies with prostaglandin F2α-induced low progesterone concentrations (PGF) in the early luteal phase and control pregnancies (CON) in the same mares (n = 12). Mares were inseminated and in PGF pregnancies received the prostaglandin F2α analogue cloprostenol (62.5 µg) on days 0–3 after ovulation to induce subphysiological progesterone concentrations; CON pregnancies remained untreated. Mares were assigned to PGF or CON treatments in alternating order and received the opposite treatment in the following year. Blood was collected and conceptus size determined repeatedly by transrectal (≤day 101) and transabdominal (>day 101) ultrasonography. After birth, foals were weighed, measured and submitted to a clinical examination. Treatment PGF resulted in fewer pregnancies than CON treatment. All foals born from CON pregnancies were healthy and mature, whereas 4/7 PGF pregnancies were either lost (one embryonic death, one abortion) or resulted in the birth of compromised foals (P = 0.018). Size of the conceptus (e.g., diameter day 49: PGF 6.6 ± 0.7, CON 7.7 ± 0.7 cm, P = 0.006) and embryo proper (e.g., crown rump length day 54; PGF 4.4 ± 0.8, CON 5.8 ± 0.6 cm, P = 0.015) differed between treatments. These size differences decreased over time and at birth PGF foals did not differ significantly from CON foals. In conclusion, reduced progesterone concentration in the early luteal phase leads to delayed conceptus growth beyond placentation and increased pregnancy loss.

Prolonged baleen hormone cycles suggest atypical reproductive endocrinology of female bowhead whales.

Serial measurements of hormone concentrations along baleen plates allow for reconstructions of mysticete whale reproductive histories. We assessed gestation and calving interval in bowhead whales (Balaena mysticetus) by measuring progesterone, oestradiol, corticosterone and nitrogen stable isotope ratios (δ15N) along baleen of 10 females from the eastern Canada-west Greenland population. Three immature females (body size < 14.32 m) had uniformly low progesterone concentrations across their baleen, while seven mature females (body size ≥ 14.35 m) had repeated, sustained elevations of progesterone indicative of pregnancies. The mean duration of progesterone elevations (23.6 ± 1.50 months) was considerably longer than the approximately 14 month gestation previously estimated for this species. We consider several possible explanations for this observation, including delayed implantation or sequential ovulations prior to gestation, strategies that would allow females to maximize their fitness in variable Arctic conditions, as well as suggest modified criteria defining gestation as a shorter component of the entire progesterone peak. Calving intervals varied within and among individuals (mean = 3.7 years; range = range 2.8-5.7 years), providing population-specific reproductive estimates for growth models used in bowhead whale management and conservation.

Effect of transvaginal oocyte aspiration on progesterone concentrations and estrous cycle length in domestic jennies

With the growing interest in developing assisted reproductive techniques for breeding or animal preservation purposes, transvaginal oocyte aspiration or ovum pick up (OPU) has become an established technique for collecting oocytes and in vitro embryo production in the horse. However, no studies have explored the impact of OPU on the estrous cycle and progesterone dynamics in jennies. Our work aimed to investigate the effect of the OPU procedure on estrous cycle length and plasma progesterone concentration in jennies. Ten healthy Argentinian native domestic jennies aged 3 to 12 years were used for this experiment. A total of 18 estrous cycles were evaluated during one breeding season: eleven control and seven cycles with OPU. Jennies were monitored every second day by ultrasonography until ovulation was detected (ovulation day = day 0 of the estrous cycle). Blood samples for progesterone determination were obtained from two control and three OPU cycles every two days for an entire estrous cycle (control) and from OPU day until the following ovulation (OPU group). Progesterone concentration was measured by Chemiluminescent Microparticle Immunoassay. For the OPU procedure, jennies on days 8 and 12 of the estrous cycle with more than six total follicles and no follicles larger than 25 mm were selected. The OPU procedure was performed as described by Bragulat et al. (Theriogenology. 2023; 195:199-208). Student's t-test was used to compare estrouscycle length, and analysis of variance (ANOVA) was conducted to determine whether there were any statistically significant differences in progesterone concentrations between control and OPU groups. The estrous cycle length of jennies subjected to OPU was significantly longer (P=0.02) than the control group (mean ± SEM, minimum / maximum values): Control, 22.64 ± 0.85 16/27 days; OPU, 26,00 ± 0.93 23/28 days. No luteinized structures were found after OPU sessions. In control estrous cycles, progesterone concentration increased after ovulation, reaching a peak on day 12 (mean ± SEM values; 36.20 ± 0.99 ng/ml) and decreasing to baseline concentration from day 16 (4.65 ± 3.18 ng/ml) to day 20 (0.75 ± 0.21 ng/ml). The results showed a significant difference in progesterone concentrations between the control and OPU groups (p = 0.003). Specifically, jennies subjected to OPU had lower progesterone concentrations from day 10 to 14 compared to the control group. Interestingly, both groups reached a similar baseline by day 16 until the following ovulation. Therefore, these preliminary data suggest that follicle aspiration between days 8 and 12 may slightly prolong the estrus cycle in donkeys and could affect progesterone plasma concentrations in jennies. However, further studies are required to confirm these results.

Effect of mid-diestrus oxytocin treatment on early pregnancy in the mare

Progesterone supplementation in early pregnancy is commonplace in equine reproduction. Recently, there has been some controversy questioning the beneficial effects of routine progesterone administration and rising concerns of medication exposure as an occupational hazard for humans. Although premature luteal regression and resulting low plasma progesterone concentrations are rare in the mare, select cases benefit from luteal support. Duration of luteal function can be prolonged following oxytocin administration during mid-diestrus in the non-pregnant mare (Vanderwall.et.al. Journal of Equine Veterinary Science. 2012; 32:536-541). The aim of this field study was to investigate the effects of oxytocin administration on early pregnancy in the mare. Thoroughbred mares (n = 39; age 5 to 19 years) were enlisted and bred over 55 estrous cycles. Prior to natural breeding, uterine cultures were obtained, and mares were assigned to 1 of 2 groups: Oxytocin treatment (OT); oxytocin 60 units, intramuscularly, once daily, days 7-14 post-ovulation; or Control (CT); no treatment. Mare reproductive cycles were monitored by transrectal palpation and ultrasonography. Ovulation was documented and defined as day 0. Pregnancy diagnosis was performed by transrectal ultrasonography day 14 post-ovulation. If pregnancy was confirmed, a blood sample was collected and assayed for plasma progesterone concentration. Mares that did not conceive were administered prostaglandin F2αanalogue (cloprostenol; 250mcg once intramuscularly) at day 16 post-ovulation. These mares were rebred and treatment was determined by the stage in the study; therefore, some mares underwent the same treatment more than once. Subsequent pregnancy examinations were performed on days 28 and 45 of pregnancy. Data were analyzed using two-tailed Fisher's Exact tests for small counts, with significance defined at p < 0.05. First and per-cycle pregnancy rates for OT and CT were 90.9 and 91.3% and 68.2 and 55.1%, respectively. Median progesterone concentrations for OT were 6.9 and 7.0 ng/ml for CT. There were no differences between OT and CT groups for first (p = 0.165) or per cycle (p = 0.289) pregnancy rates, days 28 and 45 pregnancy rates (p = 1.0), or progesterone concentrations (p = 1.0). In this population of mares, oxytocin administration during mid-diestrus in early pregnancy did not induce a negative effect on pregnancy rate nor a positive effect on progesterone concentration. Whilst the study design did not assess the effect of OT on the inter-ovulatory interval (IOI), the authors’ hypothesize that the IOI would be increased, due to prolonged luteal function, in the non-pregnant OT mare if prostaglandin F2α analogue was not administered. Further investigation in this area may reveal potential beneficial effects of oxytocin administration in early pregnancy.

Evaluation of treatment with deslorelin acetate to induce ovulation and secondary CL formation during the first two weeks of diestrus in mares

Induction of secondary ovulations during the first two weeks post-ovulation could increase progesterone concentrations in pregnant mares predisposed to pregnancy loss due to low progesterone concentrations, such as those carrying mule pregnancies. The objective of this study was to evaluate the effectiveness of deslorelin to induce follicular growth, ovulation and secondary CL formation in mares. Ten adult, healthy mares were used on several occasions for a total of 30 cycles. In the experimental group (n=24 cycles) the mares were treated with 600 μg of deslorelin acetate every 12 h for up to five days, starting when a follicle ≥19 mm was first detected by ultrasonography during diestrus. When the follicle reached 35 mm a bolus injection of 1.8 mg deslorelin was administered to induce ovulation. In the control group (n=6 cycles) the mares were treated with injectable water every 12 h for 5 days starting when a follicle ≥ 19 mm was first detected during diestrus. Daily ultrasonographic observations were continued until day 25 post-ovulation to determine the occurrence of ovulation and secondary CL formation during diestrus. In 19/24 (79%) of cycles treated with deslorelin a follicle grew to ≥ 35 mm, while in the control group it only did so in 1/6 (17%) cycles (p˂0.05). In the treatment group, 4/19 mares thatdeveloped large follicles ovulated and formed a secondary CL. These represented 21% of the mares that developed a large follicle and 17% of the total number of treated mares. No secondary diestrus ovulation occurred in the control cycles. A sustained increase in progesterone concentrations occurred in the cycles with secondary ovulations after treatment with deslorelin, suggesting continued progesterone production by both the primary and the secondary CL. In some of the mares that did not ovulate a sharp but transient increase in progesterone concentrations occurred after the administration of 1.8 mg deslorelin, possibly reflecting stimulation of the primary CL. It is concluded that deslorelin is effective to induce follicular growth up to a preovulatory size in diestrous mares. However, a low proportion of them ovulated and formed a secondary CL after the final injection of deslorelin, suggesting that another alternative, such as hCG administration should be tested to induce ovulation of the follicles stimulated by deslorelin during the first five days post-ovulation in mares. Acknowledgements: Project financed by PAPIIT project IN225923, DGAPA, UNAM, México.

152 The effect of high or low concentration of progesterone during diestrus and its association with intensity of oestrus in lactating Holstein cattle

152 The effect of high or low concentration of progesterone during diestrus and its association with intensity of oestrus in lactating Holstein cattle

153 The effect of high or low concentration of progesterone during diestrus and its association with the LH surge and PGF2α metabolite in lactating Holstein cattle

153 The effect of high or low concentration of progesterone during diestrus and its association with the LH surge and PGF2α metabolite in lactating Holstein cattle

Successful management of mid cycle estrus in Murrah buffaloes- A prelimnary case study

Two pleuriparous Murrah buffaloes were presented with the history of artificial insemination 9 days back and since early morning animal exhibiting signs of estrus. Per rectal and ultrasonographical examination revealed presence of dominant follicle and CL on different or same ovary at the same time, uterus was toned and oedematous with scanty thick cervico vaginal discharge on back retching. To study the hormonal milieu serum progesterone estimation was done in both mid cycle estrus buffaloes and in other two animals with normal estrous cycle in same stage (Day 9 from the last date of A.I.). The diameter of CL was larger in buffaloes exhibiting midcycle estrus than that of true estrus. In this case study, during mid-cycle estrus secretion of estrogen was higher from dominant follicle of first follicular wave and due lower progesterone concentration from insufficient CL animal exhibit signs of estrum in mid lutel phase.

Androgen-armoured amazons: reversed sex roles in coucals are associated with testosterone in females but not males

In some species, sexual selection is stronger in females than males. In classically polyandrous birds, for instance, females compete for mating opportunities and males care for offspring. Sex steroids such as testosterone have been suggested to regulate the behaviours of 'role-reversed' females and males, but comparative studies did not find evidence for a role of testosterone in relation to sex roles. However, the large variability of hormone measurements across laboratories may prevent detecting subtle differences in hormone levels. To circumvent this caveat, I compared sex steroid concentrations of females and males of two closely related and cohabiting species with different mating systems: the classically polyandrous black coucal (Centropus grillii) and the monogamous white-browed coucal (C. superciliosus). Baseline and gonadotropin-releasing hormone (GnRH)-induced testosterone concentrations were twice as high in female black coucals than female white-browed coucals, and the low pre-breeding progesterone concentrations of female black coucals were consistent with progesterone's modulatory role during agonistic interactions in this species. Baseline and GnRH-induced testosterone and progesterone concentrations did not differ between males of both species. This study provides first evidence that elevated testosterone is associated with sex-role-reversed traits in females, whereas low levels of testosterone may not be necessary to facilitate sex-role reversal in males.

Individualized luteal phase support using additional oral dydrogesterone in artificially prepared frozen embryo transfer cycles: is it beneficial?

Research questionDoes additional supplementation with oral dydrogesterone improve reproductive outcomes in patients with low serum progesterone concentrations on the day of frozen embryo transfer (FET) after artificial (HRT) endometrial preparation? DesignRetrospective, single-centre cohort study including 694 unique patients performing single blastocyst transfer in an HRT cycle. For luteal phase support, intravaginal micronized vaginal progesterone (MVP, 400 mg twice daily) was administered. Serum progesterone concentrations were assessed prior to FET and outco-mes were compared among patients with normal serum progesterone (≥8.8 ng/ml) continuing the routine protocol and patients with low serum progesterone (<8.8 ng/ml) who received additional oral dydrogesterone supplementation (10 mg three times daily) from the day after FET onwards. Primary outcome was live birth rate (LBR), with a multivariate regression model correcting for relevant confounders. ResultsNormal serum progesterone concentrations were observed in 547/694 (78.8%) of patients who continued only MVP as planned, whereas low (<8.8 ng/ml) serum progesterone concentrations were detected in 147/694 (21.2%) patients who received additional oral dydrogesterone supplementation on top of MVP from the day after FET onwards. LBR was comparable between both groups: 37.8% for MVP-only versus 38.8% for MVP+OD (P = 0.84). The multivariate logistic regression model indicated that LBR was not significantly associated with the investigated approaches (adjusted odds ratio 1.01, 95% confidence interval 0.69–1.47, P = 0.97). ConclusionsThe current findings suggest that additional oral dydrogesterone supplementation in patients with low serum progesterone concentrations at the moment of transfer could have the potential to rescue reproductive outcomes in HRT–FET cycles. This field of research, however, remains hampered by the absence of randomized controlled trials.

Influence of the Level of Sex Hormones in the Blood of Gilts on Slaughter Characteristics and Meat Quality.

The aim of the conducted research was to determine the impact of factors such as sex hormone levels, which vary during gilts' reproductive cycle, on the quality of the obtained meat and slaughter characteristics of the processed gilts. The research material included a population of 60 gilts slaughtered in one of the slaughterhouses located in south-eastern Poland. After the slaughtering operations were completed, the carcasses were weighed at the classification stand. The results of the statistical evaluation of the haematological and biochemical blood parameters of the examined gilts showed that, in the tested blood samples, the concentration of progesterone had a statistically significant impact only on the level of total protein, which was higher in the blood samples of gilts with a low concentration of progesterone. It was found that carcasses of gilts with higher levels of the LH hormone were characterized by a lower meat content index by nearly 3%. It was shown that the concentration of LH affected the post-slaughter temperature of the sirloin and ham muscles. The interpretation of the obtained data was difficult since there seems to be a gap in the literature concerning the dependencies of sex hormone levels in gilts and meat quality.

APPLICATION OF PROGESTERONE PROFILES IN THE ASSESSMENT OF POST ARTIFICIAL INSEMINATION FERTILITY IN CATTLE

The present study was conducted to investigate success of AI in relation to progesterone concentrations with respect to the timing of inseminations or heat detection in the field. Milk samples were collected for progesterone assay from 149 crossbred cows subjected to AI. The milk progesterone concentrations were estimated by RIA to access the reproductive status of the cows. On the day of AI, progesterone concentrations were less than 1.0 nmol/L (Low) in 51% samples and more than 3.00 nmol/L (High) in 18%. Rest 31 % samples showed intermediate progesterone (1.01 to 2.99 nmol/L) suggesting that these cows were nor in proper heat at the time of AI. On the basis of two samples (day 0 and day 10-12 post AI), 50% cows had low progesterone concentrations on the day of AI and high in the second sample, indicating that these cows were inseminated during estrus and ovulated subsequently. Whereas, 12% cows had high progesterone in both the samples suggesting that at the time of AI these cows were either in the luteal phase or had luteal cyst. Remaining 37% cow had intermediate progesterone concentrations on both the occasions suggesting that they were having either developing or regressing or malfunctioning corpora lutea or partial luteal cyst. Perusal of observations on progesterone concentrations showed that 18% of inseminations were done during luteal phase and another 30% were done at some inappropriate time of heat, thus suggesting that high proportion (48%) of cows under field conditions were inseminated while not in proper heat.

Effect of Additional Progesterone Treatment During Intravaginal Progesterone Priming in AnestrousEwes

Oestrus induction with intravaginal progesterone is the most preferred method in anoestrus sheep. In previous studies it was argued that the decrease in the progesterone level before the sponge is removed reduces the efficiency. This study aimed to test the hypothesis that additional progesterone treatment during the progesterone priming in anestrous ewes could increase the reproductive efficiency of the induction. The study conducted on 261 Kangal sheep, which were pregnant in autumn and gave birth in spring and breastfed their lambs for about 60-75 days. All animals included in the study were randomly divided into 3 different groups as P-7 (n = 86), P-8 (n = 80) and control (n = 95). At the beginning of the study a progesterone impregnated sponge was placed to all ewes (Day 0). During sponge treatment, an injection of progesterone was given to P-7 and P-8 group 7 and 8 days after the was sponge placed, respectively. As for control group, no additional progesterone was given during sponge treatment. All groups received 500 IU pregnant mare serum gonadotropin at the sponge withdrawal. Ram was introduced to all ewes the 10th days of the study. There was no difference between the groups in terms of estrus rate (P = 0.28), pregnancy rate (P = 0.32) and multiple pregnancy rates (P = 0.38) (P = 0.28). We considered that the main reason for unexpected low progesterone concentration at the end of the treatment might be the result of high feed intake and metabolic rate. On the other hand, this additional dose could be caused by an excessive increase in progesterone levels in the sheep, which could be the reason for the decrease in reproductive parameters. Additional progesterone support during progesteronebased synchronization yielded acceptable results. However, progesterone can be administered in injection form in the earlier days of synchronization or before sponge insertion to obtain better results.

Low plasma progesterone concentration during the early luteal phase delays endometrial development and the beginning of placentation in mares

While detrimental effects of reduced plasma progesterone concentration in the early luteal phase on conceptus development in horses have recently been demonstrated, there is no information on associated effects on the endometrium, allantochorion (AC), and chorionic girdle (CG) in this species. We hypothesised that reduced early postovulatory progesterone concentration in pregnant horses is detrimental to endometrial function and development of the embryonic membranes and is an underlying cause of delayed conceptus development. After insemination and ovulation, mares (n = 11) were assigned to treatment (TREAT) or control (CON) during two pregnancies. In TREAT pregnancies, mares received a PGF2α analogue for four consecutive days starting on the day of ovulation with the aim to reduce progesterone secretion. Mares were left untreated in CON pregnancies and thus served as their own controls. Endometrial biopsies for analysis of histomorphology, epidermal growth factor (EGF) and EGF receptor (EGFR) mRNA and protein expression in the endometrium, AC, and CG as well as abundance of regulatory T lymphocytes (Tregs) were collected on day 34 of pregnancy. Histomorphometric analysis revealed a higher luminal endometrium and a higher CG epithelium in CON compared to TREAT pregnancies. Abundance of mRNA for EGF and EGFR was large in the endometrium, AC and CG but did not differ between TREAT and CON pregnancies. The number of endometrial regulatory T lymphocytes was reduced in TREAT compared to CON pregnancies, adding further aspects to the potentially detrimental effects of reduced progesterone concentrations on equine pregnancy.

The post-ovulatory rise in progesterone is lower and the persistence of oestrous behaviour longer during the first compared with the second cycle of the breeding season in mares.

Mares are seasonally polyoestrous breeders. Therefore, the first ovulation of the season, following winter anoestrus, is the only cycle in which mares ovulate without the presence of an old CL from the previous cycle. The objective of this study was to compare the length of oestrous behaviour, and plasma progesterone concentrations during the early post-ovulatory period between mares after the first and second ovulation of the breeding season. Overall, 38 mares and 167 oestrous periods were used in the study. From those, 11 mares were used during the first and subsequent oestrous period to measure and compare the post-ovulatory rise in progesterone concentration, whereas all the mares were used to compare the length of the post-ovulatory oestrous behaviour between the first and subsequent cycles of the breeding season. The persistence of the post-ovulatory oestrus was longer (p< .001) following the first ovulation of the year (median of 52 h) compared with the subsequent ovulations (median of 36 h for second and later ovulations groups; n= 38 mares). The progesterone concentration at any of the four 8h-intervals analysed (28, 36, 76 and 84 h post-ovulation) was lower (p< .01) following the first versus the second ovulation of the year. By 36 h post-ovulation the progesterone concentration of mares at the second ovulation of the year had passed the threshold of 2ng/ml (2.1± 0.33 ng/ml), whereas in the first cycle it was 1.2± 0.13 ng/ml. In conclusion, mares had lower progesterone concentrations in their peripheral circulation and longer persistence of oestrous behaviour following the first ovulation of the year compared with the second and subsequent ovulatory periods of the breeding season.

Study of progesterone level during first trimester of pregnancy in cows.

Measurement of progesterone is an indirect method for pregnancy diagnosis in many livestock species including cattle, buffaloes, sheep, and goats. Conception extends the life of the corpus luteum (CL) by preventing the luteolytic mechanism from being triggered, thus prolonging and maintaining its functional characteristics, ensuring continued high progesterone levels (Spencer, et.al., 1995). (Shemesh et al., 1973) proposed that the difference in peripheral plasma progesterone levels between pregnant and non pregnant cows, 19 days after insemination, can form the basis for a very early pregnancy test. (Laing and Heap 1972) first documented this in milk to diagnose cows in early pregnancy Progesterone maintains the uterine endometrium in a state which supports embryonic development, implantation, and foetoplacental development. Progesterone concentrations vary with the stage of the estrous cycle which makes it one of the most commonly studied reproductive hormones in bovine ruminants for pregnancy detection and ovarian activity (Kaneko,et.al.,1994). Studies in the bovine estrous cycle indicate that the milk or serum progesterone concentrations reach a maximum value 13-14 days after estrus, and if the animal is pregnant, these continue to remain elevated up to day 21 after fertilization (Parkinson, et al.,1994) . These high levels of progesterone in serum or milk between days 18 and 24 after insemination form the basis of establishment of pregnancy in cattle (Sasser, and Ruder,1987; Shemesh,1973). Interferon-???? exerts its antiluteolytic effect by inhibiting the endometrial expression of oxytocin receptors, through which oxytocin stimulates pulsatile PGF2???? release (Wolf,2003). Although low progesterone concentrations at 18 to 24 days after breeding can accurately predict non pregnancy, high progesterone concentrations during this period are not the specific indicators of pregnancy due to variations among cows in duration of the estrous cycle as well as the incidence of early or late embryonic mortality. The advantages of progesterone assay for pregnancy diagnosis include noninvasive collection of milk sample and the feasibility to conduct the test on the farm using commercial cow-side milk progesterone test kits [Pennington,1985 ; Gowan,1982 ; Wimpy,et.al.,1986), though the sensitivity gets compromised to some extent with these assay kits.&#x0D; Key Word: progesterone, pregnancy, cows