Induction of parturition in cattle with cloprostenol

Bovine retained placenta: hormonal concentrations in fetal and maternal placenta

The aim of this study was to evaluate the relationship between the occurrence of retention of the fetal membranes (RFM) and the hormonal concentrations of progesterone, estradiol-17beta, prostaglandin E(2) (PGE(2)), prostaglandin F(2alpha) (PGF(2alpha)), oxytocin (OT), oxytocin receptor (OT-R), endothelin-1 and angiotensin II (Ang II) in the placental tissues of cattle. Parturition was induced in nine Holstein cows by a single injection of PGF(2alpha) on Day 274 of gestation. Six out of nine cows in the induced group did not release the fetal membranes within 12 h after parturition and served as the RFM group, and the remaining three cows in that group, which released their fetal membranes within 12 h, served as the non-RFM group. Five other cows calved spontaneously and served as controls. The placental tissues were collected immediately (0 h) and at 6 h after parturition. The hormonal concentrations were measured by enzyme immunoassay in maternal and fetal placental tissues from RFM, non-RFM and control cows. There were no differences in P4 and E2 concentrations among the RFM, non-RFM and control groups. The mean PGF(2alpha) concentration of the RFM group was lower than those of the non-RFM and control groups in the maternal part of the placenta. In maternal tissues, the OT and OT-R concentrations in the RFM group were lower than those at 0 and 6 h after parturition in the non-RFM group. Additionally, the Ang II concentration of the RFM group in both the maternal and fetal parts of placental tissues tended to be higher than those of the other groups. In conclusion, the present results suggest that ET-1 and Ang II may play differential tissue-specific roles in the placental unit that may amplify the local endocrinological cascade involving OT, OT-R and PGF(2alpha) interactions which are necessary for normal placental separation in the cow.

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.

Receptor blockers - general aspects with respect to their use in domestic animal reproduction

Receptor blockers compete with the respective agonist for binding to a given receptor without inducing complete signal transduction. In recent years, major interest has focused on sex-steroid hormone receptor blockers (antagonists). Indications have been obtained that inadequate changes in receptor conformation and subsequent failure of transcriptional activation are major events preventing hormonal activity. However, various subtypes and variants of receptors and receptor mutations have also been identified. Expression of antihormonal effects may vary depending on the type of receptor the blocker is bound to. Hence, receptor blockers may also have an inherent agonistic activity. Aglepristone is the first antiprogestin registered for veterinary use with the indication "interruption or prevention of pregnancy"; similarly, these types of compounds were successfully used for induction of parturition in the dog and cat and for conservative treatment of pyometra in the dog. Moreover, application of antiprogestins has clearly demonstrated the role of progesterone as a major factor controlling overt pseudopregnancy in dogs. With respect to farm animals, parturition was induced in cows without an increased incidence of retained fetal membranes. Other than antiprogestins, antioestrogens and antiandrogens are still in a more experimental phase. In particular for use in humans, high-affinity blockers binding to the oxytocin/vasopressin receptor are in development; they exert distinct tocolytic activities. Also, the release of GnRH can be inhibited by respective antagonists; however, their use in reproduction is still hampered by the high dose requirement and the side effects observed.

Bovine retained placenta: aetiology, pathogenesis and economic loss

The literature on the effects and causes of retained placenta in the cow is reviewed. On a herd basis the condition can adversely affect milk yield and fertility, but on an individual cow basis the effects are unpredictable. The aetiology of retained placenta has been extensively studied and many causal factors have been implicated, but little is known of how many of them cause the condition. As a result its prevention and prediction is uncertain, primarily because of the lack of knowledge of the normal process of placental release. Vascular changes and uterine contractions play a role in placental release, but current opinion suggests that the primary cause of retained placenta is the retention of the feto-maternal union. Release only occurs after a process of maturation, which involves hormonal and structural changes. The factors which are thought to influence these changes, and thus cause the condition, are discussed.

Course of pregnancy, steroid hormone levels and maturation process of placentomes after oestrone infusion in cows near term

The present study was designed to examine the effect of systemic oestrone infusion on the course of late pregnancy and parturition, steroid hormone concentrations and maturation of placentomes in cows. Twelve pluriparous pregnant cows with known breeding dates were used in this experiment. Starting on day 267 of pregnancy six cows (experimental group) received 20 mg oestrone daily (in four doses) infused into the vena jugularis until parturition. Six other cows infused with vehicle served as control. Concentrations of oestrone (E1), oestrone sulphate (E1S) and progesterone (P4) were measured by RIA, and after parturition placentomes were examined histologically. In experimental and control animals parturition occurred on days 276,9 +/- 1.8 and 277,2 +/- 1.1 of gestation, respectively. The concentrations of E1 in the treated group were higher (8-12 ng/ml) than those in control animals (1-3 ng/ml), while the levels of E1S (8-14 ng/ml) were similar for both groups. The concentrations of P4 in experimental and control cows were typical for late pregnancy (4-6 ng/ml), with a sharp drop of this hormone 1-2 days before calving. The histological pictures of placentomes obtained from both groups of animals were similar and maturation of the placenta was observed. These results suggest that the prepartal increase of oestrone in maternal plasma does not play a major role in the regulation of parturition and placental maturation.

Female reproductive physiology and endocrinology of cattle

Maximizing reproductive efficiency is of major economic importance to dairy and beef producers. The development of new and improved methods of increasing reproductive performance depends on our understanding of the physiologic and endocrinologic mechanisms controlling the reproductive process. This article reviews the mechanisms associated with puberty, estrous cycles, pregnancy, parturition, and postpartum return to estrus.

Parturition in beef cows following administration of porcine relaxin at ten days prepartum

Administration of procine relaxin (pRLX) to heifers 5 d prepartum has been reported to expedite parturition. Thirty-eight mature crossbred beef cows were randomly assigned to one of three treatment groups. Control animals (C; n = 13) received an intramuscular (i.m.) injection of 2 ml corn oil and 2 ml i.m. phosphate-buffered saline (PBS) 24 h later; relaxin treated animals (RLX; n = 13) received 2 ml i.m. corn oil and 1.0 mg i.m. pRLX 24 h later; estradiol-relaxin treated animals (E-RLX; n = 12) received 20 mg i.m. estradiol benzoate (EB) and 1.0 mg i.m. pRLX 24 h later. Treatment with pRLX occurred at 272.6+/-0.14 d of gestation. The pRLX had been purified to homogeneity from porcine ovaries collected during late pregnancy and was determined to have >/=3000 U/mg by the mouse interpubic ligament bioassay. Peripheral blood samples were collected from all cows at 0, 4, 8 and 24 h, respective to corn oil or EB administration, and assayed for plasma estradiol-17beta. At 24 h post administration of EB, plasma estradiol-17beta concentrations were 48.0+/-10.5 pg/ml for C and RLX cows and 178.5+/-14.8 pg/ml for E-RLX cows. There were no treatment effects (P>/=0.10) for elapsed time from treatment to parturition (304.2+/-22.4 h), gestation length (285.2+/-0.9 d), calving difficulty score (1.05+/-0.04), calf vigor score (1.05+/-0.04) or calf birth weight (38.0+/-0.88 kg). Additionally, there were no retained placental membranes in any cows. Administration of pRLX intramuscularly to beef cows at 10 d before expected parturition was not effective in inducing premature parturition. Furthermore, the effectiveness of pRLX in inducing parturition was not enhanced by pretreatment with estradiol benzoate.