Endocrine changes in late bovine pregnancy with special emphasis on fetal well-being

During late bovine pregnancy, several hormones are involved to maintain and develop a successful result with a live calf. These hormones are e.g., progesterone, high levels during the whole pregnancy period, originating from the corpus luteum, maternal adrenals and placenta. Oestrone sulphate, oestrone in its conjugated form, shows elevated levels from about mid-pregnancy until the third stage of parturition (expelling of the fetal membranes). For the onset of normal parturition and the parturition process as such, a change from progesterone to oestrone synthesis is crucial. The increasing levels of oestrone are time-related to an increased synthesis of prostaglandin F(2alpha) (reflected as elevated levels of 15-ketodihydro-PGF(2alpha)) causing prepartal luteolysis and several hormones are then involved in the labour process such as prostaglandin F(2alpha), cortisol and oxytocin. Cortisol might also be an indicator of stressful events for the dam. Levels of pregnancy associated glycoproteins (PAGs), originating from the trophoblastic binucleate cells, are increasing during the last 10 days prior to parturition. All the mentioned hormones have certain functions during pregnancy, more or less understood. However, could deviations from the expected profiles during late bovine pregnancy indicate impaired fetal well-being or be of importance for reproductive performance during the postpartum period? Abortions, stillbirths or dystocia are situations where endocrine profiles might predict the status of the calf. There are two possible approaches to study the endocrine changes in late pregnancy-to follow spontaneous cases of normal or impaired pregnancies or to experimentally disturb the gestation or induce parturition. We have in one study followed pregnant animals to depict reproductive disturbances, both animals with expected normal parturitions and animals where the sire of the calf has given rise to a high incidence of stillborn calves. The number of stillborn calves or dystocia has been small and so far it has not been possible to obtain a clear picture of the usefulness of endocrine parameters to follow fetal well being, but some of the hormonal parameters show a deviating profile. In a small group of animals with induced parturition (PGF(2alpha)), two out of three had parturition problems and one of these animals had a stillborn calf. All three animals had retained fetal membranes. It was possible to demonstrate a deviating endocrine profile in the cow having the stillborn calf in the sense of higher levels of progesterone, cortisol and 15-ketodihydro-PGF(2alpha) at the time of parturition. In both animals with dystocia the levels of oestrone sulphate after parturition were more sustained. Increasing and high levels of PAGs were only demonstrated in the animal with a normal parturition. These studies are ongoing, aiming at finding changes in endocrine profiles related to impaired pregnancies.     

Peripartal Endocrinology in the Mare and Foetus

The endocrine profiles in the periparturient mares are dominated by increasing concentrations of progestagens and decreasing oestrogens. These hormones are produced by precursors from the foetus, metabolized by the placenta and act primarily on the maternal uterus. The circulating concentrations of hormones in maternal plasma, generally, represent a small proportion of those metabolized by the foetus and utero-placental tissues. There is clear evidence that the foetal hypothalamo-pituitary-adrenal (HPA) axis initiates the process of foetal maturation and the hormonal cascade which culminates in parturition at term. The endocrine changes associated with abnormal pregnancy and abortion in late pregnancy are less well understood, as are the hormonal treatments needed to avert these problems. Further work is needed to establish the biological role of the various hormones present in pregnant mares and, in particular, those hormones which control myometrial quiescence.     

Effects of Hemophilus somnus on the pregnant bovine reproductive tract and conceptus following cervical infusion

Three strains of Hemophilus somnus were infused into the posterior cervix of six pregnant cows. The organism persisted in the cervicovaginal region for eight to 87 days, and at parturition H. somnus was isolated from chorioallantois in four of six cows; placentitis developed, and fetal membranes were retained. All calves were born alive and no H. somnus was recovered from them. One cow died 14 days after parturition. The death was attributed to severe necrotizing metritis; H. somnus was not isolated from the uterus at death, but was isolated from the placenta at parturition and cervicovaginal mucus two days days later.     

Clinical signs and hormonal changes in dairy heifers after induction of parturition with prostaglandin F2 alpha

Parturition was induced in 12 dairy heifers with prostaglandin (PG) F2 alpha about 2 weeks before the expected time of calving. Eight animals gave birth after two injections (group 1), three animals needed more than two injections (group 2) and one animal (cow no. 740) required one injection. All animals in groups 1 and 2 had retained foetal membranes and the time needed to induce parturition was 59 +/- 7 and 149 +/- 10 h, respectively. As cow no. 740 did not have retained foetal membranes and calved 24 h after one PGF2 alpha injection, it was excluded from the results. Udder distension and relaxation of the pelvic ligaments could predict the calving to within 12 h. Furthermore, the pre-calving drop of body temperature could predict the time of parturition to within 16 h. The total white blood cells and polymorphonuclear cells were at their highest values on the day preceding parturition whereas mononuclear cells had a tendency to increase 3 days after calving. Increased levels of haemoglobin were found at the time of parturition, whereas, plasma-calcium levels significantly decreased after parturition (P < 0.001). Progesterone levels markedly decreased after the first PGF2 alpha injection and reached 2 nmol/l at the time of parturition. Plasma levels of oestradiol-17 beta reached the peak at the time of parturition, whereas, the highest levels of the PGF2 alpha metabolite and cortisol were recorded 16 h after calving.     

Bacterial Isolates Associated With Dystocia And Retained Placenta In Iraqi Buffaloes

The present study was conducted on 50 recently calved Iraqi Buffalo cows. Depending on the kind of parturition, buffalo cows were divided into two main groups, the first group had normal unassisted parturition (NP) (26 animals) and the second group with certain periparturent complications (PPC) (24 animals). After 24 h of parturition, these two groups were further subdivided into two groups as cows expel their foetal membranes in <24 h postpartum and referred as non‐retained placenta (NRP) while cows that did not expel their foetal membrane after 24 h referred as retained placenta (RP). Sampling for bacteriology, uterine discharge for polymorphonuclear cells per cent and blood samples for polymorphonuclear neutrophil (PMN) and the enzyme creatine kinase activity were performed at 6, 24 and 48 h postpartum. In PPC group, the most prevalent bacteria after 6 h of calving were Escherichia coli, β‐haemolytic Streptococci and Lactobacillus acidophilus. Total bacterial isolates in the uterus of buffaloes with RP in PPC group after 24 and 48 h were 129 and 183 respectively. Among the isolates, Archanobacterium pyogenes, Fusobacterium necrophorum, Prevotella melaninogenicus and Staphylococcus aureus were the most prevalent isolates after 48 h of RP buffaloes in PPC group. Polymorphonuclear neutrophil were significantly (p < 0.01) increased in the uterine discharge than in blood in buffaloes with RP in both PPC and NP groups. In conclusion, uterine contamination occurs as a result of postpartum ascending contamination by non‐specific environmental organisms. The presence of Lactobacillus sp. in the uterus indicated a healthy uterus. Peripartum complications followed by retention of foetal membranes with the dominance of E. coli in the uterine lumen might favour the colonization of other bacteria including facultative anaerobic and strictly anaerobic in the uterine wall of buffaloes.     

Histologic and histochemical study of placentomes in cows after induced labor

The placentomes were extirpated from 16 cows after parturition induced with 750 micrograms cloprostenol or 20 mg dexamethasone on the 277th day of gravidity, on an average, from 9 cows after spontaneous parturition, and from 7 cows after hysterectomy in the eighth month of gravidity. In the cows with induced calving the foetal placenta was not expelled within 12 hours after calving in 68.7% of the cases whereas in the spontaneous parturitions this proportion was only 22.2% of cases. The placentomes obtained immediately after calf expulsion, and then after four and eight hours, were subjected to histological and histochemical examination. In the terminal crypts of the placentome in cross sections obtained from cows which expelled the placenta in time after natural and induced parturitions, the number of binuclear cells of the fetal syncytium and of cells of the dam epithelium (P less than 0.001) was found to be significantly lower than in the cases of afterbirth retention (1.2 and 3.9; 6.4 and 18.5). The cells of the cow's epithelium of the expelled placentae had a higher activity of acid phosphatase and lipids and the foetal syncytium had a higher activity of non-specific esterase. Increased alkaline phosphatase activity was characteristic of the cow's epithelium in the cases of subsequent retention of afterbirth. These findings should be taken into account in efforts for developing new methods of the induction of parturition if the undesired occurrence of afterbirth retention is to be reduced.     

Hysterotomy by a colpotomy approach for treatment of foetal mummification in a cow

A 7-year-old Brahman cow was diagnosed as suffering from chronic foetal mummification of unknown aetiology, concurrent cystic ovarian disease, prolapse of the 2nd cervical ring and chronic cervicitis. Repeated treatment with prostaglandin F2alpha and oestrogen failed to resolve the mummification. A hysterotomy was performed via an incision in the dorsolateral vaginal wall. Good exposure of the uterine horn was achieved and mild post-operative complications were observed. Colpotomy can be regarded as an alternative surgical approach to the moderately enlarged bovine uterus.     

Macrophages in bovine term placenta: An ultrastructural and molecular study

Retention of foetal membranes (RFM) is a major reproductive disorder in dairy cows. An appropriate immune response is important for a physiological expulsion of the foetal membranes at parturition. Our study aims to provide a deeper insight into characteristics of foetal and maternal macrophages in bovine term placenta. We used transmission electron microscopy (TEM), immunohistochemistry and semi-quantitative RT-PCR to provide a deeper insight into characteristics of foetal and maternal macrophages in bovine term placenta. Semi-quantitative RT-PCR was used to define macrophage polarization in foetal and maternal compartments of normal term placenta. Gene expression of factors involved in M1 polarization [interferon regulatory factor-5 (IRF5), interleukin (IL)-12A, IL12B] and in M2 polarization (IL10) were studied. Ultrastructurally, foetal macrophages showed an irregular shape and large vacuoles, whereas the maternal macrophages were spindle shaped. By immunohistochemistry, macrophages were identified by a strong staining with the lysosomal marker Lysosome-associated membrane glycoprotein 1 (LAMP-1), while myofibroblast in the maternal stroma was positive for alpha-smooth muscle actin. We used the LAMP-1 marker to compare the density of foetal stromal macrophages in placentas of cows with RFM and in controls, but no statistically significant difference was observed. RT-PCR showed a higher expression of all studied genes in the maternal compartment of the placenta and generally a higher expression of M1-, compared to M2-associated genes. Our results indicated that at parturition placental macrophages predominantly show the pro-inflammatory M1 polarization. The higher expression of all the target genes in the maternal compartment may denote that maternal macrophages in bovine term placenta are more frequent than foetal macrophages.     

Endocrine measurements and calving performance of Swedish red and white and Swedish Holstein dairy cattle with special respect to stillbirth

During 3 consecutive calving seasons, calving performance, placental characteristics and endocrine profiles of total 98 pregnancies of late pregnant Swedish Red and White (SRB) and Swedish Holstein (SLB) dairy heifers and cows, were investigated. Ninety-four singleton pregnancies and 4 sets of twins were recorded. In animals with singleton pregnancy, 8 stillbirths, 7 weak calves, 3 premature parturitions and 1 abortion were registered. In the SLB heifers, 19% of stillbirth (5/26) were observed, while 5% (2/42) were noted for the SRB heifers. One stillborn calf derived from the SRB cows and none was found from the SLB cows. In the heifers and cows delivering a normal living calf with unassisted parturition, the placentome thickness monitored by ultrasonography was constant towards the end of pregnancy. The numbers of foetal cotyledons varied individually between animals but in total, fewer cotyledons were found in the foetal membranes of the SRB animals than in the SLB animals (69 +/- 19) vs. (88 +/- 29) (p < 0.05). No morphological and numerical differences of the placentome thickness in animals delivering a stillborn or weak calf, compared to animals delivering a normal living calf, could be observed. In animals with unassisted parturition and without birth complications, the levels of progesterone (P4), PGF2alpha metabolite (PG-metabolite), cortisol, oestrone sulphate (E1SO4) and pregnancy associated glycoproteins (PAGs) were not different by breeds and parities. In animals carrying stillbirth, higher levels of E1SO4 were found in 3 SRB animals and 1 SLB heifer, whereas lower levels of E1SO4 were recorded in 3 SLB heifers during the last week of pregnancy, compared to the profiles found in animals with unassisted parturition. Additionally, the levels of PAGs remained low and constant in 1 SRB cow (delivering a stillborn calf), 1 SRB heifer (giving birth prematurely), 4 animals (carrying twins) and 1 aborting SRB cow. Our results show a very high rate of stillbirth in especially SLB heifers and deviating profiles of E1SO4 and PAGs in animals with impaired parturition were recorded.     

Effects of Calf Removal at Parturition on Postpartum Ovarian Activity in Zebu (Bos indicus) Cows in the Humid Tropics

To assess endocrine and morphological responses of ovaries to total weaning at parturition, 6 Zebu (Bos indicus) cows 5 years or older were investigated. Following parturition, blood samples were collected daily during the first month and twice weekly thereafter until day 60 to determine concentrations of progesterone (P₄) and prostaglandin F_2α metabolite.It took between 25 to 32 days to complete uterine involution.The prostaglandin metabolite remained elevated for a mean period of 14.2 days (range, 4-21) postpartum. Five of the animals resumed cyclicity with a short estrous cycle starting between days 7 to 34 and lasting between 7 and 14 days. No estrous behavior was recorded prior to the short estrous cycles, but subsequent normal-length estrous cycles were all preceded by signs of estrus. In the 1 animal that resumed cyclicity with an estrous cycle of normal length on day 37 (length 20 days), the cycle was preceded by estrous behavior.Progesterone concentrations reached a mean maximum of 4.8 nmol liter⁻¹ during the short estrous cycles, and prostaglandin metabolite concentrations peaked while P₄ concentrations were decreasing. P₄ concentrations reached a mean maximum of 12.2 nmol liter⁻¹ during the estrous cycles of normal length. The interval from parturition to the first estrous cycle of normal length varied between 16 and 48 days, and the length of the cycle was 18 to 22 days.Starting 2 days postpartum, ovaries from 5 of the cows were scanned by ultrasonography every second day until day 30 postpartum. Medium-sized follicles were detected between days 4 to 7 postpartum in 4 of the scanned cows that later had short estrous cycles. The time between parturition and the appearance of the first dominant follicle was 7.6 days (range 6-10 days). The interval between parturition and the appearance of the first ovulatory-sized follicle was 10.2 days (range 8-13 days). In 3 of the scanned cows this ovulatory-sized follicle ovulated.We conclude that cyclic ovarian activity in Zebu cows can start early in the postpartum period in the absence of offspring, and that short luteal phases, not preceded by estrous behavior, may play an important role in establishing normal postpartum ovarian activity.     

Biometric parameters of the uterus and ovaries in sheep after administration of Depotocin inj. Spofa in early puerperium]

Objectivisation of the physiological course of puerpery and control of involution processes of uterus represent topical questions of an increased frequency of lambing. Our study was directed at the determination of the weight, length of body and horns of uterus as well as of the weight, length, width and height of ovaries, following the administration of carbetocin (Depotocin inj. Spofa), in the puerperal period of Slovak Merino sheep. The study was aimed at obtaining objective biometric data on uterus and ovaries and recording the influence of carbetocin on the involution of uterus and ovaries of sheep. Thirty ewes, divided into two groups, were included in the experiment. The animals of the experimental group (n = 15) were subjected to treatment with carbetocin (Depotocin inj. Spofa) at the amount 2 x 0.07 mg. The first dose was applied intramuscularly (i. m.) on the 2nd day after parturition and the second dose was injected subcutaneously (s.c.) on the 4th day after lambing. The second group (n = 15) served as a control. Three ewes (n = 3) were bled on each of the following days: 1, 7, 17, 25 and 34 after parturition. After bleeding the sexual organs were removed by excision and their weight and the length of the body and horns of uterus and of ovaries was determined. The number and size of follicles were determined on the surface of ovaries. The weight of uterus body showed a declining tendency in sheep of the control group with a statistically significant decrease from the 17th till the 34th day after parturition (P less than 0.01). Its weight varied from 56.0-14.6 to 5.2-0.3 g in the above-mentioned time interval. The experimental group showed a statistically significant decrease in weight as early as on the 7th day after lambing compared to the 1st day after parturition, down to the values 185.66-38.91 g (P less than 0.05). The decrease in the weight of uterus body recorded on day 17 (106.56-41.08 g) was less pronounced than in the control group. The final average weight of the body of uterus on the 34th day after parturition was 41.36-8.52 g, that means higher than in the control group (5.2-0.3 g). The weight of gravid horns in the experimental group declined significantly as early as on the 7th day after parturition to the average weight of 60.89-9.45 g and reached 9.86-3.49 g on the 34th day.(ABSTRACT TRUNCATED AT 400 WORDS)     

15-Ketodihydro-PGF2α, Progesterone and Uterine Involution in Primiparous Cows with Induced Retained Placenta and Post-partal Endometritis Treated with Oxytetracycline and Flunixin

Retention of the foetal membranes (RFM) and post‐partal endometritis are common problems in dairy cows. Among other things, the disease is characterized by a bacterial endometritis with aerobic as well as anaerobic bacteria. From an endocrine perspective, cows with RFM have high levels of 15‐ketodihydro‐PGF_2α (PG‐metabolite) immediately after parturition but these levels fall rapidly within 2 weeks post‐partum (early PG‐metabolite elevation). After this decline, the PG‐metabolite levels increase again and the levels (at this time of a lower magnitude) remain elevated during the period of uterine infection (late PG‐metabolite elevation). The aim of this study was to investigate the PG‐metabolite profiles in cows with retained placenta and post‐partal endometritis treated with the prostaglandin synthesis inhibitor flunixin (F), either alone or in combination with oxytetracycline (T). The study was accomplished over 2 years with 12 primiparous cows in each experiment. As a model for RFM, preterm parturition was induced in late‐pregnant heifers by injecting PGF_2α (25 mg i.m) twice with a 24 h interval. In each experiment, the cows were divided into four groups and treated with either T (10 mg/kg b.w. i.m. once daily), F (2.2 mg/kg b.w. p.o. twice per day), a combination of T and F (dosage, as above), or conservatively (0). The treatment periods lasted from day 11 to day 14 post‐partum (pp) in experiment 1 (after placental shedding, groups T1, F1, TF1 and 0) and from day 3 to day 6 pp in experiment 2 (before placental shedding, groups T2, F2, TF2 and 0). Jugular vein blood samples were collected for analyses of PG‐metabolite and flunixin. Uterine biopsies were collected twice weekly for investigation of endometrial microbiology. Rectal palpation and ultrasonographic examinations were performed three times per week for investigations of uterine and cervical involution and ovarian activity. No attempts were made to remove the placentas manually. The experiment lasted until day 56 pp. The induction of parturition was successful in all heifers and 22 of 24 animals had RFM. All RFM cows had bacterial endometritis, based on bacteriological examinations. Flunixin treatment (F1, TF1, F2 and TF2) suppressed PG‐metabolite levels significantly (p=0.006) during the period of treatment in both experiments. However, the early flunixin treatment only suppressed PG synthesis partially. Late oxytetracycline treatment (T1) did not influence the PG‐metabolite levels but oxytetracycline treatment (T2 and TF2) before placental shedding significantly altered the kinetics of the early PG‐metabolite elevation compared with other treatments. Late PG‐metabolite elevation was significantly correlated to duration of uterine infection and cervical involution. In conclusion, flunixin treatment of cows with retained placenta either before or after placental shedding suppresses prostaglandin synthesis. However, early treatment, when the release of prostaglandins is high, might need more intensive treatment in order to prevent the PG synthesis effectively. Oxytetracycline treatment during the period immediately after parturition before placental shedding might influence the PG‐metabolite profile and suggests a bacteriological contribution to the high levels of PG‐metabolite seen during the first 2 weeks pp in cows with retained placenta. In this study, a correlation between prostaglandin release, the final cervical involution and the end of infection was found. This suggests a link between uterine endocrinology, bacteriology and involution in cows with retained placenta.     

The preliminary studies on protein profile in retained and not retained foetal membranes in heavy draft mares

Protein profile of the placenta expresses its function and maintenance. Any alterations can be reflected in qualitative and quantitative changes in this profile. The aim of the present study was the evaluation of protein profile in the placenta of mares suffering from the retention of foetal membranes (FMR) by two separation methods and the comparison with physiologically released tissues. Placentas from 14 healthy, heavy draft mares were collected immediately after the expulsion of newborn. Tissues after homogenization and staining with fluorescent dyes were subjected to electrophoretic as well as chromatographic separation. Electrophoretic gels were statistically analysed for the presence and abundance of examined proteins, while some proteins were identified in chromatographic fractions. Out of 248 spots detected in endometrium, 38 differed significantly between FMR and control animals, while in allantochorion, respective values reached 241 and 27 spots (p < .05). Among identified proteins that expressed higher abundance in endometrium of FMR mares than control animals were prostaglandin reductase, dehydrogenase/reductase SDR family, and placental growth factor. These proteins are involved in regulation of parturition. Additionally, the following proteins responsible for physiological activity of a cell—guanine methyl transferase, aspartyl/asparaginyl beta‐hydroxylase and GTP‐binding protein, were identified. These proteins expressed higher abundance in allantochorion of FMR mares than in controls. This preliminary study confirmed the disturbances in protein pattern between foetal membranes in FMR and healthy mares. Further qualitative and quantitative experiments are necessary to deepen our knowledge on the mechanisms of the retention of foetal membranes in mares.     

Analysis and Validation of the Differentially Expressed ENO1 in the Maternal Placenta of Cow with Retained Foetal Membrane

The paper aimed to analyze and validate the function of differentially expressed ENO1 in the cow with retained foetal membrane.In our research,we chose three healthy Holstein dairy cows and three Holstein dairy cows with retained foetal membrane of similar age,foetal times,weight and milk yield and divided them into two groups.The total protein of maternal placenta was extracted in the control and retained foetal membrane of cow.The differential expression of proteins were found out by the 2-DIGE,and the differential expression of ENO1 was validated by the Western blotting and Real-time quantitative PCR.The results showed that ENO1 was significant expression and large multiple in the two groups,and it was significant increased expression in the retained foetal membrane of cow after Western blotting and Real-time quantitative PCR (P=0.015<0.05;P=0.001<0.01).The ENO1 participated in the energy homeostasis,immune and fibrinolysis process which related to the retained foetal membrane of cow.It suggested that ENO1 was likely connected with the retained foetal membrane.     

胎衣不下奶牛母体胎盘α-烯醇化酶异常表达分析及验证

试验通过对胎衣不下奶牛母体胎盘组织中差异α-烯醇化酶(enolase,ENO1)的分析验证,探讨ENO1在胎衣不下中的作用。本研究选取了年龄、胎次、体重和泌乳量均相近的产后胎衣不下和产后胎衣正常排出奶牛各3头,分为两组,提取了胎衣不下组与胎衣正常排出组母体胎盘组织中的总蛋白,采用双向凝胶电泳的方法筛选出差异蛋白,并利用Western blotting及实时荧光定量PCR的方法对其中差异表达量大的ENO1进行验证。结果发现,胎衣不下组和胎衣正常组母体胎盘组织中ENO1差异表达量大且倍数较大,Western blotting及实时荧光定量PCR验证发现ENO1在胎衣不下奶牛母体胎盘中的表达量升高,t检验结果分别为P=0.015<0.05,差异显著;P=0.001<0.01,差异极显著。该基因参与机体的能量调节、免疫和纤溶等过程,而这些过程与奶牛胎衣不下密切相关,提示ENO1可能参与该病的发生发展。     

Levels of oestrone sulphate during pregnancy in different breeds of cows and its possible association with retained foetal membranes.

The levels of oestrone sulphate in plasma of pregnant cows was followed from 30 days of pregnancy until parturition. The Swedish Jersey Breed (SJB) showed significantly lower levels of oestrone sulphate between 101 and 200 days of pregnancy than either the Swedish Red and White (SRB) or the Swedish Lowland Breed (SLB). No significant difference was noted between SRB and SLB. On days 141-160 of gestation the oestrone sulphate values were still below the 10 nmol/l level for the SJB while they were above this level for the SRB and the SLB, and the difference was significant. In the SJB, levels above 10 nmol/l were reached on days 161-180 of gestation. In the second part of this study the levels of oestrone sulphate were measured around parturition in SRB cows. At parturition, the levels of oestrone sulphate rose to peak values of 79.9 +/- 5.2 nmol/l and then decreased to 6.6 +/- 0.5 nmol/l on the day after calving. In one cow peak values of 66.0 nmol/l were reached 2 days prior to parturition, and subsequently dropped to 7.0 nmol/l at parturition. This cow had retained foetal membranes. A possible relationship between low oestrone sulphate levels prior to parturition and retained foetal membranes is discussed.     

The immune status of the bovine uterus during the peripartum period

The post-partum period in cattle is characterised by an increased risk of infection of the uterus, as the anatomical barriers are broached during parturition and remain open for several days. Infection of the uterus is largely influenced by the balance between bacterial contamination and the local and systemic immune status during pregnancy and around parturition. Infectious diseases are more prevalent during this period, because of an impaired immune status before and immediately after parturition. Neutrophils play a primary role in the defence of the uterus against infection. Influx of neutrophils into the uterus is thought to be mediated by chemoattractants, chemokines and adhesion molecules, such as beta2-integrin (complement receptor 3) and L-selectin (CD62L). Other cellular components activated in the uterus during this period include lymphocytes, eosinophils, mast cells and macrophages. The major classes of immunoglobulins (IgM, IgA and IgG), either by passive diffusion or local production, play an important protective role in the uterus by acting as opsonins to enhance phagocytosis, stimulating the complement pathways or blocking pathogens from adhering to mucosal surfaces. Endometrial cells express toll-like receptor 4 (TLR4), which recognises lipopolysaccharides of Escherichia coli and other Gram negative bacteria, the most common causes of bovine endometritis. Activation of TLR4 triggers the production of tumour necrosis factor alpha and other pro-inflammatory cytokines. The periparturient period is also characterised by an increased secretion of prostaglandin F(2alpha), which enhances uterine immune defences.     

Enzymatic activity in the placenta in cows in relation to the course of parturition

The activity of aminopeptidases and cathepsins was determined in placentoma homogenates; placentomas of cows were extirpated immediately after parturition and in four and eight hours. In cows with afterbirth retention (a. r.) following induced parturition, the activity of these enzymes was always higher than in cows without a. r., no matter if after induced and spontaneous parturitions; it was at a similar or slightly higher level than in the eighth month of pregnancy. The content of total proteins in placentomas of cows with a. r. was also higher. These findings point to the insufficient ripening, or aging of placental tissue, which is related to a release of lysosomal enzymes. The enzymes are active through hydrolysis in the separation of foetal placenta from the maternal one and in the modification of proteins participating in intercellular linkages.     

Between prepartum luteolysis and onset of expulsion

In the cow the foetal endocrine signals that initiate the calving process result in prepartum luteolysis. Withdrawal of progesterone (P4) action is a prerequisite for a normal calving. The rather abrupt declining influence of P4 is followed by a cascade of physiological processes in the myometrium and cervix. This contribution will focus on some of these events. Like in many other species, the myometrium in cows is not completely inactivated during pregnancy. So-called contractures have been registered during the final weeks of gestation and their EMG-characteristics in cows show a low frequency (on average: 13.6 per day) and long duration (on average 12.1 min). They are not evenly spread over the day because they occur less frequently when the cows are disturbed for feeding or cleaning their stables. Contractures affect several foetal functions. In the cow these contractures disappear during a period of about 8-9h when maternal plasma P4 levels are rapidly declining before calving. There is experimental evidence that this temporary inhibition is associated with prepartal luteal regression. The cause of this inhibition is still unknown. Because nitrous oxide inhibits smooth muscle cells and evidence in laboratory animals indicates that expression of the inducible form of nitrous oxide (iNOS) is downregulated in myometrium, but upregulated in the cervix around the onset of parturition, we started to investigate the role of this enzyme in bovine tissues around calving. By means of a RT-PCR technique, we obtained a first indication that iNOS is hardly expressed in the myometrium during calving, while expression was clearly detected at day 4 after calving. Analysis of prepartum en periparturient biopsies from myometrium and cervix with quantitative PCR is still underway. In six pregnant cows, provided with uterine EMG-electrodes and with ultrasonic crystals implanted on the caudal cervical rim to measure cervical dilatation, calving was induced with an injection of prostaglandin (PG) F2alpha. While maternal plasma P4 levels had significantly declined within 8h after PG treatment, the myometrium escaped from temporary inhibition with the development of a parturient contractility pattern on average at 13.5h after injection. However, it was only at 28 h after PG treatment that the first sustained increase of the opening of the vaginal ostium of the cervix was measured.