Effect of synchronization protocols on reproductive indices,progesterone profile and fertility under subtropical environmental conditions in repeat breeder Holstein cows

The objectives were to evaluate the reproductive indices and survival analysis of pregnancy outcomes in multiparous repeat breeder Holstein cows (n = 557). The cows were synchronized to ovulate by Ovsynch, new controlled internal drug release device (N‐CIDRsynch), and once‐used CIDR device (U‐CIDRsynch). The pregnancy per AI at 28 days post‐insemination (P/AI 28) in the N‐CIDRsynch group (28.75%) was significantly (COR = 1.49; p = 0.011) greater than that reported in the Ovsynch (23.46%) and U‐CIDRsynch (21.73%) groups. Furthermore, the pregnancy per AI at day 75 post‐insemination (P/AI 75) in the N‐CIDRsynch group was significantly greater than the Ovysync group (COR = 1.35; p = 0.050). The repeat breeder cows received a N‐CIDR device had a significantly higher progesterone level on day 2 and day 4 of CIDR insertion (1.38 and 1.67 ng/ml, respectively) than those received a U‐CIDR device or the control group (p = 0.012 and 0.001, respectively). The Cox regression model recorded significant associations for synchronization protocols, THI at the TAI and season of calving with the hazard of P/AI 28 and P/AI 75 (p = 0.044 and 0.046; 0.001 and 0.005; 0.003 and 0.001, respectively). Multiparous repeat breeder cows (>3) had a lower hazard ratio (HR) of P/AI 28 than that reported in the reference (2nd parity) group (HR = 0.74, p = 0.050). The repeat breeder cows inseminated at 76–80 and >80 temperature‐humidity index (THI) had significantly lower HR of P/AI 28 than those inseminated at the baseline (<70) THI value (HR = 0.73 and 0.30, p = 0.036 and 0.001, respectively). The current results indicate that the use of N‐CIDR synch protocol may achieve satisfactory pregnancy outcomes in repeat breeder cows.     

Plasma fatty acids, prostaglandin F2alpha metabolite, and reproductive response in postpartum heifers fed rumen bypass fat

An experiment was conducted to determine whether feeding rumen-protected fatty acids (FA) to postpartum heifers would increase plasma concentrations of linoleic acid and PGF2, metabolite (PGFM), shorten the interval from calving to first increase in plasma concentrations of progesterone (P4), and increase pregnancy rate relative to controls. Hereford x Angus heifers (346 kg) were assigned randomly to treatments containing either lipid or barley supplemented diets for the first 30 d postpartum. Lipid was .23 kg.heifer(-1).d(-1) of calcium salts of FA (CSFA; n = 20), and an isocaloric amount of barley served as the control (n = 19). Supplements, with .23 kg of barley as a vehicle, and a basal diet of meadow and alfalfa hays were pen fed to heifers (5/pen). Heifers were bled on alternate days (d1 to 30) and twice weekly (d 30 to 2 wk after first estrus) for RIA of plasma PGFM and P4, respectively. Weight percentage of major FA in plasma on d1 and 7 was determined with gas chromatography. First behavioral estrus was detected by use of intact bulls and confirmed by an increase in plasma P4. On d 7, but not d 1, plasma from heifers fed CSFA had altered proportions of major FA (P < .01), including an increase in linoleic acid compared with those of controls (29.1 vs 25.6% of total FA; SE = .75; P < .01). Analysis of variance of contrast variables revealed an effect of treatment on direction of change in PGFM from d 3 to 5 (P < .01). By d 7 and on d 9, plasma concentrations of PGFM were greater in heifers fed CSFA than in controls (P = .02 and P = .06, respectively). There was no difference in plasma concentration of PGFM between treatments on d 1, 3, 5, 11, 13, and 15 postpartum (P = .80, .17, .52, .82, .46, and .77, respectively). Days to first estrus with ovulation, pregnancy rate, and calving interval were not affected by treatments (P = .58, .52, and .24, respectively). Although supplemental lipid fed to primiparous beef heifers increased plasma levels of linoleic acid and production of PGFM in the early postpartum period, it did not improve the fertility of these heifers in the subsequent breeding season.     

Plasma levels of cortisol, progesterone, oestradiol-17 beta and prostaglandin F2 alpha metabolite after ACTH (Synacthen Depot) administration in ovariectomized gilts

In order to elucidate the effect of stress on reproductive hormones, the present study was designed to investigate the effect of adrenocorticotropic hormone (ACTH) on the plasma levels of cortisol, progesterone, oestradiol-17 beta and prostaglandin F2 alpha metabolite in ovariectomized gilts. Ovariectomy and cannulation of the jugular vein were performed within 1 week of oestrous detection, under general anaesthesia. Approximately 1 week after surgery, two gilts were each administered ACTH (Synacthen Depot) intravenously, at a dose of 0.01 mg/kg body weight, and one gilt was given saline solution (5 ml). The reverse was performed on the following day. The administration of ACTH was followed by a concomitant elevation of cortisol, progesterone and prostaglandin F2 alpha metabolite but not of oestradiol-17 beta. Peak cortisol, progesterone and prostaglandin F2 alpha metabolite levels were reached at 80 +/- 10.0, 80 +/- 10.0 and 46.6 +/- 13.3 min after ACTH administration and the durations of the peaks were 181.8 +/- 19.8, 308.1 +/- 49.7 and 181.8 +/- 7.9 min, respectively. The total area under the curve for cortisol, progesterone and prostaglandin F2 alpha metabolite was significantly higher in the ACTH than in the control group. The present results indicate that during stress, cortisol, progesterone and prostaglandin F2 alpha levels are elevated while the level of oestradiol-17 beta is less affected. It can be concluded that the administration of ACTH to ovariectomized gilts, results in the elevation of cortisol, progesterone and prostaglandin F2 alpha metabolite but not of oestradiol-17 beta.     

Fish meal supplementation alters uterine prostaglandin F2alpha synthesis in beef heifers with low luteal-phase progesterone

The objective of the current study was to evaluate the effect of omega-3 fatty acids in fish meal on mitigating uterine PGF2alpha synthesis in heifers with low luteal-phase concentrations of progesterone. Animals were individually fed a corn silage-based diet supplemented with fish meal (5% of DMI; n = 12) or corn gluten meal (6% of DMI; n = 13). Estrous cycles were synchronized using PGF2alpha beginning on d 25 of supplementation. Random heifers from each supplement group (n = 6 fish meal, and n = 7 corn gluten meal) were given three additional i.m. injections of PGF2alpha (25 mg) at 12-h intervals beginning at 0600 on d 3 after estrus to induce formation of corpora lutea that secrete lower concentrations of progesterone. Jugular blood samples were collected daily commencing on d 1 and continuing through d 16 of the estrous cycle to determine serum progesterone concentrations. Oxytocin was administered i.v. (100 IU) to heifers on d 16 after estrus to stimulate uterine PGF2alpha synthesis. Before statistical analyses, heifers were sorted to either normal or low luteal-phase progesterone as determined from serum progesterone on d 9 of the estrous cycle. After sorting, treatment groups consisted of 1) normal luteal progesterone + fish meal (n = 6); 2) low luteal progesterone + fish meal (n = 6); 3) normal luteal progesterone + corn gluten meal (n = 6); and 4) low luteal progesterone + corn gluten meal (n = 7). Serum concentrations of the PGF2alpha metabolite following oxytocin stimulation tended (P = 0.09) to be greater in heifers with low luteal-phase progesterone compared with heifers with normal luteal-phase progesterone. Fish meal supplementation mitigated this response in heifers with low luteal-phase progesterone (P < 0.05), but had no effect on heifers with normal luteal-phase progesterone. In conclusion, the omega-3 fatty acids in fish meal seem to decrease uterine PGF2alpha synthesis in heifers with low luteal-phase serum concentrations of progesterone.     

Synchronization of estrus and artificial insemination in replacement beef heifers using gonadotropin-releasing hormone, prostaglandin F2alpha, and progesterone

We evaluated whether a fixed-time AI (TAI) protocol could yield pregnancy rates similar to a protocol requiring detection of estrus, or detection of estrus and AI plus a clean-up TAI for heifers not detected in estrus, and whether adding an injection of GnRH at controlled internal drug release (CIDR) insertion would enhance fertility in CIDR-based protocols. Estrus in 2,075 replacement beef heifers at 12 locations was synchronized, and AI was preceded by 1 of 4 treatments arranged as a 2 x 2 factorial design: 1) Estrus detection + TAI (ETAI) (n = 516): CIDR for 7 d plus 25 mg of prostaglandin F2alpha (PG) at CIDR insert removal, followed by detection of estrus for 72 h and AI for 84 h after PG (heifers not detected in estrus by 84 h received 100 microg of GnRH and TAI); 2) G+ETAI (n = 503): ETAI plus 100 microg GnRH at CIDR insertion; 3) Fixed-time AI (FTAI) (n = 525): CIDR for 7 d plus 25 mg of PG at CIDR removal, followed in 60 h by a second injection of GnRH and TAI; 4) G+FTAI (n = 531): FTAI plus 100 microg of GnRH at CIDR insertion. Blood samples were collected (d -17 and -7, relative to PG) to determine ovarian status. For heifers in ETAI and G+ETAI treatments, a minimum of twice daily observations for estrus began on d 0 and continued for at least 72 h. Inseminations were performed according to the a.m.-p.m. rule. Pregnancy was diagnosed by transrectal ultrasonography. The percentage of heifers exhibiting ovarian cyclic activity at the initiation of treatments was 89%. Pregnancy rates among locations across treatments ranged from 38 to 74%. Pregnancy rates were 54.7, 57.5, 49.3, and 53.1% for ETAI, G+ETAI, FTAI, and G+FTAI treatments, respectively. Although pregnancy rates were similar among treatments, a tendency (P = 0.065) occurred for pregnancy rates in the G+ETAI treatment to be greater than in the FTAI treatment. We concluded that the G+FTAI protocol yielded pregnancy rates similar to protocols that combine estrus detection and TAI. Further, the G+FTAI protocol produced the most consistent pregnancy rates among locations and eliminated the necessity for detection of estrus when inseminating replacement beef heifers.     

Pregnancy and peripheral plasma progesterone levels in cows inseminated after synchronization of estrus with prostaglandin F2 alpha

Fifteen Holstein cows were treated with two doses of 25 mg of a prostaglandin F₂α (PGF₂α as dinoprost tromethamine) administered intramuscularly 11 days apart. The cows were then divided into three groups and inseminated either at 72, 80 or 72 and 96 hours after the second dose of PGF₂α. Thirteen cows ovulated after the second prostaglandin treatment. Eight cows were diagnosed pregnant by rectal palpation 42 days after insemination but only five calved. PGF₂α induced luteolysis in cows with active corpora lutea as evidenced by the dramatic decreases in the plasma progesterone concentrations after treatment. In contrast, following PGF₂α administration to cows in follicular or late luteal phase the concentrations of plasma progesterone either increased gradually or remained low for several days before increasing to maximal levels. The ovulatory rate after the two doses of PGF₂α11 days apart was high. However, the pregnancy rate after this treatment was influenced by other factors including abnormal ovarian function.     

Synchronization of estrus with melengestrol acetate and prostaglandin F2 alpha in beef and dairy heifers

Beef (n = 783) and dairy (n = 209) heifers at 14 locations were used to evaluate the efficacy of feeding melengestrol acetate (MGA; .5 mg/d) for 7 d followed by an i.m. injection of 25 mg prostaglandin F2 alpha (PGF) on the last day of MGA feeding (MGA + PGF) to synchronize estrus. Untreated heifers (C) and heifers injected once i.m. with PGF served as contemporary controls. Heifers were observed for estrual behavior for a minimum of 38 d starting on the 2nd d of MGA feeding. Heifers in estrus from d 1 through d 60 after PGF injection were artificially inseminated (AI) or bred to bulls (d 30 to 60 post PGF only). During the 7-d MGA feeding period fewer (P less than .01) MGA + PGF (1.5%) than C (20.6%) or PGF (18.1%) heifers were observed in estrus. Percent of heifers in estrus d 1 to 6 post PGF was different among groups (P less than .05; 30.5, 52.8, 72.3 for C, PGF and MGA + PGF, respectively). More (P less than .01) MGA-fed (92%) than non-MGA-fed (C and PGF combined) heifers (85.4%) were observed in estrus during d 1 to 24. Conception rate (CR) during d 1 to d 6 was not different (P = .19) between C (58.9%) and MGA + PGF (51.2%) heifers; CR was lower (P = .01) for MGA + PGF than for PGF (68.3%) heifers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of a prostaglandin F2 alpha analogue prostinfenem (15-methyl-PGF2 alpha), to induce luteolysis and oestrus in heifers.

Different doses of 15-methyl-PGF2 alpha (0.125-10 mg) were used to induce luteolysis and oestrus in 7 heifers with 28 treatments on day 8-12 of the oestrous cycle. Twenty-three out of 28 treatments gave the desired response and the animals showed signs of oestrus within 5 days post-injection. The doses of 0.25-10 mg can be used to induce luteolysis and oestrus. The dose of 0.125 mg was not effective to induce luteolysis and only 1 out of 4 treatments responded. When higher doses were given (1-10 mg), progesterone levels decreased more rapidly and reached 1 nmol/l 16.2 h earlier than in animals which responded to doses less than 1 mg. The minimum effective dose was considered to be 0.25 mg. Clinical signs of oestrus, regression of corpus luteum and variation in the interval to oestrus were similar as for PGF2 alpha or its other analogues. By measurement of the main circulating prostaglandin F2 alpha metabolite, it was found that an endogenous PGF2 alpha release occurred 1-3 days post-injection of 15-methyl-PGF2 alpha. Furthermore in cases of post-oestrous bleedings an endogenous PGF2 alpha release was also seen concomitantly with the bleeding. This prostaglandin analogue seems to be useful for farm management and can be an alternative to other PGF2 alpha analogues.     

Arginine vasopressin stimulation of prostaglandin F2 alpha release in heifers during the estrous cycle

The effect of arginine vasopressin on the stimulation of prostaglandin F2 alpha (PGF2 alpha) release has been examined in vivo. Fifty-eight heifers received one intravenous injection of 10 IU arginine vasopressin on either Day 0 (n = 14), Day 6 (n = 12), Day 13 (n = 14) and Day 18 or 19 or 20 (Day 18-20, n = 18) after the onset of oestrus (Day 0) to determine the effect of arginine vasopressin at different times of the oestrous cycle. Frequent blood samples were taken before and after arginine vasopressin injection for the measurement of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) by radioimmunoassay (RIA). Blood samples for progesterone determinations were taken 2 hr before and 24 hr after arginine vasopressin to monitor luteal function. The data show that arginine vasopressin causes an increase (P less than 0.005) in PGFM concentrations only at Day 18-20 of the cycle in 67% of the experimental heifers.     

Effect of ACTH and CRH on plasma levels of cortisol and prostaglandin F2alpha metabolite in cycling gilts and castrated boars

The present study was designed to evaluate the effects of synthetic ACTH (1-24, tetracosactid) and porcine CRH on the plasma levels of cortisol and PGF2alpha metabolite in cycling gilts (n = 3) and castrated boars (n = 3). The experiments were designed as crossover studies for each gender separately. Each animal received, during three consecutive days; 1) ACTH (Synacthen Depot) at a dose of 10 microg/kg body weight in 5 ml physiological saline, 2) porcine CRH at a dose 0.6 microg/kg body weight in 5 ml physiological saline or 3) physiological saline (5 ml). The test substances were administered via an indwelling jugular cannula in randomized order according to a Latin square. The administration of ACTH to cycling gilts resulted in concomitant elevations of cortisol and PGF2alpha metabolite with peak levels reached at 70.0 +/- 10.0 and 33.3 +/- 6.7 min, respectively. Similarly, the administration of ACTH to castrated boars resulted in concomitant elevation of cortisol and PGF2alpha metabolite with peak levels reached at 60.0 +/- 0.0 and 20.0 +/- 0.0 min, respectively. Cortisol peaked at 20 min after administration of CRH in both cycling gilts and castrated boars with maximum levels of 149.3 +/- 16.5 nmol/l and 138.3 +/- 10.1 nmol/l, respectively. It can be concluded that administration of synthetic ACTH (tetracosactid) to pigs caused a concomitant elevation of cortisol and PGF2alpha metabolite levels in both cycling gilts as well as castrated boars. The administration of CRH to pigs resulted in an elevation of cortisol levels in both cycling gilts and castrated boars. Conversely, PGF2alpha metabolite levels were not influenced by the administration of CRH either in cycling gilts or in castrated boars.     

Active immunization of heifers against prostaglandin F2 alpha: potential as a sterilization vaccine

Four experiments were conducted with 210 heifers in an attempt to develop a sterilization vaccine by active immunization against prostaglandin F2 alpha (PGF2 alpha) and to evaluate feedlot performance following immunization against the combination of PGF2 alpha and estrogens. The objectives were: development of a PGF2 alpha-ovalbumin conjugate that would induce antibody formation when used with complete Freund's adjuvant (CFA); comparison of CFA with other adjuvants in relation to PGF2 alpha antibody binding and maintenance of the corpus luteum; examination of growth performance in immunized heifers against both PGF2 alpha and estradiol-17 beta and evaluation of sterilization in PGF2 alpha-immunized heifers maintained with bulls. A PGF2 alpha-ovalbumin conjugate was developed that resulted in antibody production against PGF2 alpha, although antibody binding was quite low. The antibody response in heifers was higher in Exp. I and II than in Exp. III and IV (P less than .05). Complete Freund's adjuvant was the best adjuvant in inducing antibody formation compared with all other adjuvants tested (P less than .01). Corpus luteum (CL) function was maintained for 2.5 mo and ovulation was apparently blocked in Exp. I. The results of Exp. II confirmed those of Exp. I. Fewer than half of the heifers in Exp. III and IV had prolonged estrous cycles. In Exp. IV, immunized heifers became sterile for at least 4 mo when kept with bulls, although the success rate was only 37%. The low levels of antibody titers to PGF2 alpha in Exp. III and IV may be the reason for the failure to maintain CL function in some heifers.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Serum progesterone levels in post-partum dairy cows after repeated application of the prostaglandin F2 alpha analogue D (+) cloprostenol sodium

Reproductive management programmes based on strategic use of prostaglandin F2 alpha (PGF2 alpha) to induce and synchronize oestrus in post-partum dairy cows are widespread. Repeated shortening of the oestrous cycle during early lactation in high-yielding dairy cows, however, could impair corpus luteum function and thus decrease fertility. The objective of this study was to analyse the effect of repeated treatments with the prostaglandin F2 alpha analogue D (+) cloprostenol sodium on progesterone concentrations indicative of a functional corpus luteum in post-partum dairy cows. Furthermore, the influence of milk production, parity and endometritis on progesterone concentrations under these circumstances were studied. Eighty-four cows of a commercial dairy operation were treated three to four times with D (+) cloprostenol sodium (Preloban; Hoechst Roussel Vet, Wiesbaden, Germany) at 14-day intervals, starting 22-28 days post-partum. Blood samples were collected prior to treatment 1 (sample 1) and 14 days after treatments 1, 2 and 3 (samples 2-4) and serum progesterone (P4) levels were determined. The percentage of cows with P4 levels < 1 ng/ml decreased from 51% in sample 1 to 23% in samples 3 and 4. More primiparous cows had low P4 levels 14 days after the second treatment than older cows (P < 0.05). Cows with low progesterone levels in sample 3 or 4 had lower protein contents in milk on the second milk test day post-partum and in their cumulative milk yield of the first 100 days of lactation. Clinical endometritis at post-partum examination did not influence progesterone levels after treatment with PGF2 alpha. Repeated application of PGF2 alpha (more than twice) in the post-partum period does not influence serum progesterone levels 14 days after treatment. Failure to develop luteal tissue after treatment contributed to the conception failures after first service.     

The hormone profile in the blood plasma of heifers after cycle synchronization with prostaglandin F2alpha

Highly sensitive radio-immuno assay (RIA) was used for 21 days to study the curves of several steroid hormones, progesterone (P), oestradiol 17 beta (E2), and testosterone (T), as well as of luteinizing hormone (LH) in peripheral blood of six heifers to which oestrus had been induced by prostaglandin F2 alpha. The validity of the authors' RIA for P, E2, and T determination in blood plasma was positively verified by two reliability criteria, correctness and accuracy, as well as by comparative determinations, using reference methods. Only four of the six heifers returned to oestrus, within 21 days from first oestrus induction. A typical cycle-related curve of the P concentration in peripheral blood with peak values between the 13th and 17th days of cycle (15-26 nmol/l) was recorded from four animals. The peak values of pre-ovulatory E2 and LH were between 33.0 and 53.2 pmol/l or between 19.5 and 52.5 micrograms/l. Some of the T rises in peripheral blood were in parallel to E2 concentrations. All hormone curves are presented in detail and are discussed in relation to clinico-physiological findings.     

Ovarian responses to intramuscular or intravenous administration of prostaglandin F2 alpha in control and FSH-treated beef heifers

Sixty Simmental crossbred heifers 18 to 20 mo of age were detected in estrus and assigned at random to a 2 x 2 factorial design study with 30 controls, and 30 given FSH. Half of each group was given prostaglandin F2 alpha (PGF) i.v. and the rest i.m. Injections of follicle-stimulating hormone were started on d 7 to 14 of an estrous cycle and continued for 5 d or until ovariectomy; PGF was administered either i.v. or i.m. at 48 (25 mg) and 60 (15 mg) h after the initial FSH injection. Control females received a similar PGF treatment on a day between d 9 and 15 of the estrous cycle. Blood samples were collected from all animals immediately before PGF administration and every 12 h thereafter until ovariectomy. Within each of the four experimental subgroups, ovariectomies were performed at either 24, 48 or 72 h (five/time group) after initial PGF injection. Ovarian and corpus luteum (CL) weights were recorded as well as number and size of follicles and number of ovulations. Regression of the CL was slower (P less than .05) after administration of PGF i.v. than i.m. (CL weight was 2.6 vs 3.3 +/- .2 g for i.m. and i.v. groups, respectively). Exogenous FSH increased estradiol-17 beta (E2) concentrations, and FSH-treated heifers had more (P less than .05) early ovulations than control heifers did. Ovulations in FSH-treated heifers had begun to occur by 24 h after i.v. and i.m. PGF injection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in bovine luteal progesterone metabolism in response to exogenous prostaglandin F(2alpha)

An experiment was conducted to determine the effect of prostaglandin F2alpha (PGF2alpha) on luteal synthesis of progesterone (P4) and related progestins. Sixteen beef heifers were assigned in equal numbers to four groups in a 2x2 factorial arrangement of treatments. The experiment consisted of two levels of PGF2alpha analog (0 and 500 microg) and two levels of time (4 and 24 h after injection) of corpus luteum collection. All heifers were injected intravenously with saline (2 ml) or PGF2alpha (cloprostenol) on day 8 of the estrous cycle (estrus=day 0). Jugular blood was collected at 0, 1, 2, 3, 4 and 20, 21, 22, 23, and 24 h after injection. Resulting sera were analyzed for P4 by use of radioimmunoassay. Luteal tissue was analyzed by gas chromatography/mass spectrometry for P4, 20beta-hydroxyprogesterone, pregnenolone, and allopregnanolone (3beta-hydroxy-5alpha-pregnan-20-one). Treatment with PGF2alpha reduced serum concentrations of P4 as early as 1 h after injection (P<0.005) and steroid levels remained low over 24 h. Similarly, administration of PGF2alpha caused a decline in luteal P4 (P<0.005), 20beta-hydroxyprogesterone (P<0.10), and pregnenolone (P<0.05). In contrast, treatment with PGF(2alpha) caused an increase in luteal allopregnanolone over time (time x treatment interaction; P<0.05). These data are interpreted to suggest that PGF2alpha promotes conversion of P4 to the metabolite allopregnanolone.     

Effect of intrauterine bacterial infusions and subsequent endometritis on prostaglandin F2 alpha metabolite concentrations in postpartum beef cows.

Multiparous Angus and crossbred Angus cows were used to determine the effect of induced endometritis on plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) and progesterone (P4) and on duration of the estrous cycle of treatment. Beginning on the day of calving (d 0), blood samples were collected on alternate days. On three consecutive days, ranging from d 8 to 14 of the first postpartum estrous cycle, uterine horns were inoculated transcervically with either 3 x 10(9) colony forming units (cfu) of Actinomyces pyogenes and 1.5 x 10(9) cfu of beta-hemolytic Escherichia coli (treated; n = 9) in sterile PBS or with sterile PBS alone (control; n = 9). Samples of uterine fluid were collected by transcervical aspiration twice weekly from just before the start of each series of inoculations until the end of the experiment. Endometrial biopsies were collected transcervically between d 4 to 6 and 11 to 13 after inoculation. Based on clinical observations and results of bacterial cultures, all treated cows developed acute uterine infections. Controls did not develop uterine infections. Endometrial biopsies indicated that there were no significant diffuse or focal cellular reactions in response to the infection. The interestrous interval was greater (P less than .0003) for treated (27.7 +/- 1.0 d) than for control (20.6 +/- 1.0 d) cows, but P4 concentrations were similar between the two groups. Mean PGFM concentration and PGFM profiles were similar (P greater than .10) between treated and control cows before bacterial infusions. Bacterial infusions increased mean PGFM concentration (P less than .0001) and changed the shape of the PGFM profile (P less than .02).(ABSTRACT TRUNCATED AT 250 WORDS)