The objective was to compare pregnancy per AI and follicular dynamic in suckled Bos taurus beef cows treated with either a 7-day progesterone + estradiol-based protocol or a 5-day progesterone CoSynch protocol for timed artificial insemination (TAI) during four breeding seasons. We hypothesized that estrous cycle status, days postpartum (DPP), fat depth and plasma progesterone concentration differentially modify the effect of treatments. Every year, 9 days before initiation of each breeding season, cows were randomly assigned to one of two groups. Cows in the 7-d P + E group (n = 428) received a progesterone intravaginal device (DIB) and estradiol benzoate on Day -9. On Day -2 the device was removed, and cows received cloprostenol and estradiol cypionate. Forty-eight hours later (Day 0) cows received TAI. Cows in the 5-d P + CoS group (n = 428) received a DIB, and GnRH on Day -8. On Day -3, the device was removed, and cows received cloprostenol. A second dose of cloprostenol was given on Day -2. Cows received GnRH and TAI 72 h after device removal (Day 0). On Day -9, estrous cycle status was determined. In a subset of cows (n = 79) the size of the dominant follicle was determined between Days -2 and 0. In another subset of cows (n = 340), DPP, fat depth (mm) and plasma progesterone concentration (ng/mL) were evaluated on Day -9. Pregnancy per AI was determined 30 d after TAI. Pregnancy per AI was greater for cows in the 5-d P + CoS group than for cows in the 7-d P + E group (50.9% vs. 41.3%, P = 0.01) and was also greater in cyclic than in anestrus cows (54.3% vs. 33.2%, P < 0.0001). There was also a significant effect of breeding season (P = 0.0002) and sire (P = 0.03), and an interaction between treatment group and breeding season (P = 0.03). The dominant follicle was larger (P < 0.0001) in cows in the 5-d P + CoS group than the 7-d P + E group (10.7 ± 0.29 mm vs. 9.0 ± 0.28 mm). Pregnancy per AI was greater in cows with ≥55 DPP (47.0% vs. 29.6%, P = 0.001), fat depth ≥0.50 mm (44.7% vs. 29.7%), and with plasma progesterone concentration ≥1 ng/mL (47.2% vs. 28.7%, P = 0.01). In cows with plasma progesterone ≥1 ng/mL on Day -9, pregnancy per AI was greater in the 5-d P + CoS group (60.5%) than in the 7-d P + E group (34.9%), but there was no difference between treatment groups in cows with plasma progesterone < 1 ng/mL (P = 0.07). In conclusion, the 5-d P + CoS protocol resulted in greater size of the dominant follicle and pregnancy per AI in suckled Bos taurus beef cows subjected to TAI.

Four experiments were designed to evaluate the effect of different circulating progesterone (P4) concentrations during a synchronization of ovulation protocol for the timed artificial insemination (TAI) of Bos indicus (Nelore) beef cattle. In the first trial, 13 ovariectomized Nelore heifers were randomly allocated into one of three groups using new P4 devices (New; 1.0 g P4), previously used P4 devices for 8 days (Used1x), and previously used P4 devices for 16 days (Used2x), in a crossover experimental design. The circulating P4 concentrations during the P4 device treatment were lower for Used1x (2.3 ± 0.1 ng/mL) and Used2x (2.0 ± 0.1 ng/mL) than those for New (3.8 ± 0.2 ng/mL; P = 0.001). In the second trial, the ovarian follicular dynamics of 60 anestrous cows were evaluated after the cows received the treatments described previously (New [n = 20], Used1x [n = 20], and Used2x [n = 20]). During the insertion of the P4 device, the cows were administered 2.0-mg estradiol benzoate. Eight days later, the P4 device was removed, and the cows were administered 0.53-mg sodium cloprostenol, 300 IU eCG, and 1-mg estradiol cypionate. There were no differences among the groups during the interval from P4 device removal to ovulation (73.7 ± 2.9 vs. 69.8 ± 2.4 vs. 68.4 ± 2.3 hours) or regarding the ovulation rate (70.0% vs. 80.0% vs. 85.0%). However, the maximum diameter of the largest follicle was greater (P = 0.06) in the Used2x (15.3 ± 0.4 mm) than that of New (13.5 ± 0.8 mm) and Used1x (14.9 ± 0.5 mm). In experiment 3, 443 anestrous cows were randomly assigned into one of the three treatments (New [n = 144] vs. Used1x [n = 167] vs. Used2x [n = 132]) and received a TAI 48 hours after the P4 device removal. The diameter of the largest follicle during the device removal (10.7 ± 0.3 vs. 11.2 ± 0.2 vs. 11.3 ± 0.3 mm) and the 30-day pregnancy rates (51.4% vs. 53.9% vs. 43.2%) did not differ among the experimental groups. In experiment 4, a field trial with 593 B indicus (Nelore) cows was conducted to evaluate the pregnancy per AI using different levels of P4 in a TAI protocol (New [n = 189] vs. Used1x [n = 203] vs. Used2x [n = 201]). The pregnancy per AI was similar between the treatment groups (63.5% vs. 57.6% vs. 62.7%). In conclusion, the low circulating P4 concentrations that were released from a used P4 device efficiently controlled the ovarian follicular growth and exhibited no detrimental effects on the pregnancy rates of the B indicus (Nelore) beef cattle.

This study was conducted to compare the in vitro development of embryos from superovulated postpubertal gilts synchronized with progesterone agonist altrenogest (REG, Regu-Mate) and those from superovulated prepubertal gilts synchronized with prostaglandin analogue cloprostenol (PLA, Planate). Ten postpubertal gilts that had exhibited estrus at least once were fed 20 mg/d of REG from Day 0 (the first day of treatment, may have been any day of the estrous cycle) to Day 17. The gilts received intramuscularly (im) 1500 IU of equine chorionic gonadotropin (eCG) on the afternoon of Day 17, followed by 1000 IU of human chorionic gonadotropin (hCG) 84 h later. Eight prepubertal gilts received intramuscularly one dose of a combination of 400 IU of eCG and 200 IU of hCG (PG 600) on Day 0 (the first day of treatment), followed by 750 IU of hCG on Day 3. From Day 16 to Day 19, the prepubertal gilts received 350 mg/d of PLA, followed by 1500 IU of eCG on the afternoon of Day 19, then 1000 IU of hCG 84 h later. Gilts were checked for estrus with an intact boar. At estrus, all gilts were artificially inseminated and/or mated twice at 12-h intervals. Then 50 to 54 h after the hCG injection, a mid-ventral laparotomy was performed on each gilt. Corpora albicans (CA) and corpora hemorrhagica (CH) were counted, and oviducts were flushed in situ. The embryos recovered (1- to 2-cell) were cultured in modified Whitten's medium at 38.5 degrees C under an atmosphere of 5% CO2 in air for 144 h. The number of CA per gilt did not differ between the postpubertal and prepubertal gilts (11.9 vs 7.9, respectively; P>> 0.05). However, the number of CH per gilt (27.5 vs 18.1, P = 0.05) and the number of embryos per gilt (26.2 vs 15.3, P < 0.05) were higher in postpubertal gilts than in prepubertal gilts. Furthermore, after 144 h of in vitro culture, the percentage of embryos cleaving to the>>-16-cell (morula + blastocysts) or>> or =32-cell (blastocysts) was greater (P < 0.05) in prepubertal gilts than in postpubertal gilts (85.2 vs 68.5, 55.7 vs 44.2, respectively). The total numbers of embryos examined were 122 and 260 in prepubertal and postpubertal gilts, respectively. These results show that postpubertal gilts treated with REG produced a higher number of embryos. However, better embryo development was noted with zygotes from prepubertal gilts primed with exogenous gonadotrophin, followed by synchronization with prostaglandin before induction of superovulation and insemination.

The aim of the current study was to determine the possible effects of progestagen oestrous synchronization on vascular endothelial growth factor (VEGF) expression during sheep luteogenesis and the peri-implantation period and the relationship with luteal function. At days 9, 11, 13, 15, 17 and 21 of pregnancy, the ovaries from 30 progestagen treated and 30 ewes cycling after cloprostenol injection were evaluated by ultrasonography and, thereafter, collected and processed for immunohistochemical evaluation of VEGF; blood samples were drawn for evaluating plasma progesterone. The progestagen-treated group showed smaller corpora lutea than cloprostenol-treated and lower progesterone secretion. The expression of VEGF in the luteal cells increased with time in the cloprostenol group, but not in the progestagen-treated group, which even showed a decrease between days 11 and 13. In progestagen-treated sheep, VEGF expression in granulosa-derived parenchymal lobule capillaries was correlated with the size of the luteal tissue, larger corpora lutea had higher expression, and tended to have a higher progesterone secretion. In conclusion, the current study indicates the existence of deleterious effects from exogenous progestagen treatments on progesterone secretion from induced corpora lutea, which correlate with alterations in the expression of VEGF in the luteal tissue and, this, presumably in the processes of neoangiogenesis and luteogenesis.

1 Human luteal tissue slices from days 18, 21 and 25 of the menstrual cycle were superfused in vitro with Medium 199 alone or containing cloprostenol (1 microgram/ml). Concentrations of progesterone, oestradiol-17beta and prostaglandins F2alpha and E2 were determined in the superfusate samples. 2 Secretion of steroids and prostaglandins was maintained at an approximately constant level throughout the experiments (21 h in one case) when the tissue was perfused with M199 alone. 3 Superfusion with cloprostenol (1 microgram/ml) resulted in an initial depression of progesterone and oestradiol-17beta but this was not maintained, levels returning to control values or showing an increase, while superfusion with cloprostenol continued. Cloprostenol is not therefore considered to be luteolytic at this dose and under these conditions for human luteal tissue in vitro. 4 Superfusion with cloprostenol (1 microgram/ml) also resulted in a large stimulation of secretion of endogenous prostaglandin F2 alpha following a short lag phase. This stimulation was possibly due to the initial depression of progesterone secretion. A short-lived stimulation of prostaglandin E2 secretion was also observed. 5 The significance of the increase in prostaglandin E2 secretion and the interrelationships between the various changes observed with cloprostenol are difficult to interpret.

We tested FSHp, eCG and FSHp+eCG to establish ovum pick-up (OPU) and in vitro maturation method in spotted paca. Eight healthy adult females were subjected to each of four treatments to stimulate ovarian follicular growth. All females were subjected to a hormonal protocol using a single dose of 45 mg of injectable progesterone and single intramuscular injection of 0.075 mg d-cloprostenol on day 6. Ovarian stimulation was carried out as follows: in Group TFE (FSHp and eCG), animals were treated with a single dose of 80 mg of FSHp and 200 IU of eCG intramuscularly on day 6 after application of progesterone; in Group TF (FSHp), they were treated with a single dose of 80 mg of FSHp intramuscularly on day 6 after application of progesterone; in Group TE (eCG), they were treated with 200 IU of eCG intramuscularly on day 6 after application of progesterone; and in Group TC (saline solution), 1 ml of saline solution was administered to control does. The OPU were performed between 22 to 26 hours after gonadotropin treatments. All recovered oocytes were placed into maturation media and incubated for 24 h. There were no differences among the mean number of observed follicles, aspirated follicles and oocytes recovered per treatment. Oocyte maturation rates did not differ among groups, except, TF and TE oocytes had greater maturation rates than TC oocytes. In this study gonadotropin administration failed to superovulate treated does and increase oocyte retrieval efficiency. Despite the feasibility of the procedure, further studies are needed to develop and refine hormonal protocols for oocyte recovery and in vitro maturation in this species.

This study compares the fertility after short- and long-term synchronization using a progesterone intravaginal device in Lacaune dairy sheep outside the breeding season. For the experiment 108 Lacaune sheep were treated with Eazi-breed™ CIDR® G intravaginal devices (Pfizer Animal Health, Zürich) for 12 days (Group L, n = 60) or 6 days (Group K, n = 48) in combination with eCG (Group L) or with eCG and 125 μg Cloprostenol (Group K) at device removal. Thereafter the ewes were kept together with rams for 60 days, ewes in estrus were recorded and the fertility was assessed after lambing. Blood progesterone concentration was measured at device application, withdrawal and 14 days later. Results show that neither treatment nor parity had an influence on estrus rate (Group L 91.7 %, Group K 93.8 %, nulli- and pluriparous animals 96.9 % and 90.8 %, respectively). Group L showed a tendency towards a better first cycle lambing rate and a significantly (P < 0.05) higher overall lambing rate compared to sheep of Group K (71.7 % vs. 60.4 % and 83.3 % vs. 72.9 %). Pluriparous ewes had higher (P < 0.05) lambing rates and greater (P < 0.05) numbers of lambs born per synchronized ewe than nulliparous sheep for the first cycle (75.0 % vs. 46.9 % and 1.4 ± 1.0 vs. 0.9 ± 1.1) as well as for the overall service period (92.1 % vs. 46.9 % and 1.7 ± 0.8 vs. 0.9 ± 1.1). Fourteen days after insert withdrawal progesterone concentrations were higher (P < 0.05) in Group L than in Group K (7.7 ± 4.3 vs. 5.6 ± 2.7 ng/mL) and in nulli- compared to pluriparous (9.1 ± 5.6 vs. 5.7 ± 2.1 ng/mL) ewes. In conclusion, the overall lambing rate was higher after long-term compared to short progesterone treatment and nulliparous ewes were less suitable for estrus induction outside the breeding season.

Concentrations of progesterone and luteinizing hormone in plasma were analysed for two consecutive years in samples from nonpregnant female roe deer. Three animals were treated with monthly prostaglandin injections (325 micrograms cloprostenol) from October 1989 to April 1990 and from October 1990 to March 1991, and three were kept as controls. In control animals, a small increase in progesterone concentrations in July 1990 occurred at the same time as the commencement of the rut in other husbanded roe deer. In prostaglandin-treated animals, progesterone concentration was high at the time of the rut and remained so until late February 1990. After the next rut (August 1990), progesterone concentration remained high until March 1991. Between October and February-March, injections of prostaglandins induced dramatic, but temporary (lasting 72 h), decreases in plasma progesterone concentrations, indicating luteal regression and subsequent ovulation. We infer that roe deer can ovulate repeatedly and should therefore not be regarded as an obligate monoestrous species.

The study aimed to evaluate pregnancy per artificial insemination (P/AI) of cows subjected to synchronization and resynchronization in ovulation protocols using intravaginal progesterone-releasing insert (P4) before pregnancy diagnosis (PD) and the relationship of PR with the diameter of preovulatory follicles (ØPOF) before TAI. Cows (n = 378) were distributed into two groups: a resynchronization group with new devices (GRN; n = 185) and resynchronization group with used devices (GRU; n = 193). On Day 0, both groups received a new P4 and estradiol benzoate (EB). On D8, P4 removal + D-cloprostenol + eCG + estradiol cypionate (EC) was done. On d10, TAI was conducted. On d32, cows were resynchronized and divided into two groups, GRN (n = 185) and GRU (n = 193). The GRN group received a new P4 + EB, and the GRU group received a used P4 + EB. On d40, the P4 was removed + PD. The non-pregnant cows received D-cloprostenol + eCG + EC. US was done again on d42 to determine ØPOF before the second TAI. The P/AI of the GRN and GRU groups after synchronization were 56.2% and 57.0% (p = 0.87), respectively, and those after resynchronization were 58.0% and 37.3% (p < 0.008), respectively. The P/AI of the GRN and GRU groups observed after TAI (synchronization + resynchronization) were 81.6% and 73.1%, respectively (p = 0.047). No difference (p = 0.067) in ØPOF between the pregnant and non-pregnant cows in the GRN was found, whereas the GRU group showed a significant difference (p = 0.003). Resynchronization protocols optimized the P/AI in both groups. New intravaginal devices resulted in greater P/AI and P/AI accumulation in resynchronization as compared with the GRU; the ØPOF was related with P/AI.

The objective of this study was to evaluate the effect of a PGF2α-analogue (PGF) on ovulation and pregnancy rates after timed artificial insemination (TAI) in cattle. In Experiment 1 cows received an intravaginal progesterone-releasing device (CIDR) plus 2 mg im of estradiol benzoate (EB) on Day 0. The CIDR devices were removed on Day 8, and all cows received 150 μg im of d-cloprostenol (PGF2α-analogue), 300 IU of eCG and 1 mg of estradiol cypionate (ECP) im. On Day 9, cows were randomly assigned into two groups: 1) ECP Group (n = 17), that did not receive any further treatment; and 2) ECP-PG Group (n = 14) that were given 150 μg of d-cloprostenol (PGF) as adjuvant stimulus for ovulation. No difference between groups was detected in interval for ovulation (P = 0.5), and in the proportion of cows ovulating (P = 0.09). In Experiment 2, multiparous suckling crossbred Aberdeen Angus cows (n = 260), were treated into two groups, similarly as Experiment 1; ECP group (n = 122), and ECP-PG group (n = 138). All females were TAI on Day 10. The proportion of cows treated with ECP that became pregnant was 54.9% (67/122), and cows treated with ECP plus PGF was 55.1% (76/138; P = 0.9). In Experiment 3, 686 Nelore cows, 40 to 50 days postpartum, were treated as Experiment 1 (ECP group), however, on Day 8 cows were divided into 3 groups: ECP Group (n = 216); PGF-SC Group (n = 228), in which cows did not receive ECP and were given an additional subcutaneous injection of PGF on Day 8; and PGF-IM Group (n = 242), in which cows also did not receive ECP on Day 8 and were given an additional injection of PGF im on Day 9. On Day 10, estrus was evaluated at timed AI (TAI). There was no difference in the diameter of the dominant follicle at CIDR removal and at TAI, and pregnancy per AI among groups (P>> 0.05). However, the proportion of cows that displayed estrus between CIDR removal and TAI was higher in ECP group than in PGF-SC and PGF-IM groups (P < 0.001). Cows that displayed estrus has higher P/AI than cows that did not (P = 0.008). In conclusion, these results suggested that intramuscular or subcutaneous injection of PGF2α could be successfully used to induce ovulation in cattle undergoing TAI, with similar pregnancy rates when compared with ECP. The subcutaneous injection of PGF on the same day of CIDR removal could be an interesting alternative due it reduces cattle management to obtain similar results.

Pregnancy rates (PR) to fixed-time AI (FTAI) in Brahman heifers were compared after treatment with a traditional oestradiol-based protocol (OPO-8) or a modified protocol (OPO-6) where the duration of intravaginal progesterone releasing device (IPRD) was reduced from 8 to 6 days, and the interval from IPRD removal to oestradiol benzoate (ODB) was increased from 24 to 36 h. Rising 2 yo heifers on Farm A: (n = 238 and n = 215; two consecutive days AI); B (n = 271); and C (n = 393) were allocated to OPO-8 or OPO-6. An IPRD was inserted and 1mg ODB i.m. on Day 0 for OPO-8 heifers and Day 2 for OPO-6 heifers. On Day 8, the IPRD was removed and 500 μg cloprostenol i.m. At 24h, for OPO-8 heifers, and 36 h, for OPO-6 heifers, post IPRD removal all heifers received 1mg ODB i.m. FTAI was conducted at 54 and 72 h post IPRD removal for OPO-8 and OPO-6 heifers. At Farm A, OPO-6 heifers, AI on the second day, the PR was 52.4% to FTAI (P = 0.024) compared to 36.8% for OPO-8 heifers. However, no differences were found between OPO-8 and OPO-6 protocols at Farm A (first day of AI) (39.9 vs. 35.7%), or Farms B (26.2 vs. 35.4%) and C (43.2% vs. 40.3%). Presence of a corpus luteum at IPRD insertion affected PR to FTAI (43.9% vs. 28.8%; P < 0.001). This study has shown that the modified ovulation synchronisation protocol OPO-6 may be a viable alternative to the OPO-8 protocol for FTAI in B. indicus heifers.

An experiment was designed to evaluate the effects of estradiol-17beta (E17beta) on follicular wave dynamics and ovulatory response in Holstein heifers receiving either a progestogen ear-implant (Crestar; Intervet International b.v. Boxmeer, The Netherlands) or an intravaginal progesterone-releasing device [controlled internal drug release-bovine device (Eazibreed, CIDR-B; Bodinco BV, Alkmaar, The Netherlands)]. For comparison, another group of heifers was also synchronized using Crestar plus an injection of estradiol valerate (EV) and norgestomet as recommended by the pharmaceutical company. Twenty 20-22-month-old cycling Holstein heifers were allocated to one of the following treatment groups at random stages of the oestrous cycle: (I) simultaneous insertion of Crestar and intramuscular injection of 3 mg norgestomet and 5 mg EV (Crestar 9 + EV 9); (II) simultaneous insertion of Crestar and intramuscular injection of 5 mg E17beta (Crestar 9 + E17beta 9); (III) insertion of Crestar followed 2 days later by intramuscular injection of 5 mg E17beta (Crestar 9 + E17beta 7); or (IV) insertion of CIDR-B device followed 2 days later by intramuscular injection of 5 mg E17beta (CIDR 9 + E17beta 7). The CIDR-B or Crestar implants were removed after 9 days and all heifers received 500 microg Cloprostenol (Estrumate, Pitman-Moore Nederland BV, Houten. The Netherlands). Ovarian ultrasonographic examinations were performed once daily during the synchronization period using a B-mode scanner equipped with a 7.5 MHz linear-array transrectal transducer. In addition, heifers were scanned every 12 h after implant/device withdrawal until 3 days after ovulation in order to monitor follicular activity, detect ovulation and subsequent early luteal formation. Detection of oestrus was performed every 6 h for 4 days after device/implant removal. Oestrus was observed 24-32 h before ovulation in all heifers. The mean hours interval from treatment withdrawal to ovulation was not significantly different (84.0 +/- 16.5, 77.6 +/- 4.1, 73.6 +/- 4.1 and 64.0 +/- 4.4 h for treatments I, II, III and IV, respectively, p>> 0.1). However, the variance for heifers treated with EV + norgestomet was significantly larger (Levene's Test; p < 0.01) than those treated with E17beta. All E17beta treatments resulted in dominant follicle suppression and a new wave emerged 4.1 days after treatment compared with 6.6 days for the EV + norgestomet treatment (p < 0.05). The time from emergence of the new ovulatory wave to ovulation was longer for the new wave that emerged after E17beta treatment (9.2 +/- 0.3 days) than after EV + norgestomet treatment (6.9 +/- 0.4 days; p < 0.05). The results of this study suggest that the four treatments used were effective in inducing synchronous behavioural oestrus and ovulation. However, a higher degree of oestrus and ovulation synchrony was observed in heifers treated with E17beta than in heifers treated with EV + norgestomet. Synchronization treatments with exogenous E17beta or EV + norgestomet at the time of progestin device insertion (Crestar or CIDR-B) or 2 days later in heifers can regulate a different emergence pattern of ovarian follicular development in randomly cyclic heifers. The E17beta was effective in inducing follicular suppression and resulted in the consistent emergence of a new follicular wave.

The objective of this study was to determine the effect on pregnancy outcome of either inseminating heifers twice (at 48 and 72 hours after withdrawal of a controlled internal drug release insert (CIDR) containing progesterone) or once (56 hours after CIDR withdrawal) following a seven-day CIDR synchronisation protocol. Dairy heifers (n=267) from five farms, with an age range of 388-736 days, were randomly assigned to one of two treatment groups (group A heifers were inseminated twice; group B heifers were inseminated once). Both groups received a CIDR on day (D) 0 and an intramuscular injection of d-cloprostenol on D6; the CIDR was withdrawn on D7. Measurements of withers height, body condition score and hearth girth (used to estimate weight) were taken on D0. The diameter of the largest follicles and corpora lutea was recorded on both D0 and D6. Data were analysed with the use of multivariable logistic regression modelling. Treatment group and farm were not statistically significantly associated with pregnancy per treatment (P/T). Age and dominant follicle size on D6 were significantly associated with P/T. Heifers with the largest dominant follicle sizes (16-22 mm) were 5.54 times less likely to be pregnant than those heifers with the smallest dominant follicles (8-10 mm) on D6. It was shown that the cost associated with inseminating heifers twice after a seven-day CIDR synchronisation protocol is not justified.

Progesterone (P4) is a requirement for pregnancy development. Previous reports observed a maximal value of serum P4 concentration on 21 days after the first mating after which it slowly declines throughout the rest of pregnancy. Ultrasound examination should be performed to ensure that pregnancy interruption is complete. Limited information is available on the ultrasonic appearance of conceptuses during pregnancy termination in cats The objective was to study serum P4 concentration and ultrasonographic changes during aglepristone (ALI) or cloprostenol (CLO) treatment and to evaluate the fertility after treatment. Two experiments (EXP) were carried out to accomplish this aim. Sixty queens, 12- to 36-month-old, were used. On Days 21 to 22 of pregnancy (EXP I) or 35 to 38 of pregnancy (EXP II), queens were divided into three groups (G). Queens in G1 received ALI (10 mg/kg, sc; EXP I, n = 10; EXP II, n = 10) for 2 consecutive days. Queens in G2 received CLO (5 μg/kg, sc; EXP I, n = 10; EXP II = 10) for 3 consecutive days. Queens in G3 received 1 mL of saline solution (PLA, sc; EXP I, n = 10; EXP II = 10). Blood samples were taken before treatment (Day 0) and every day during 10 days after the treatment to measure serum P4 concentrations. Likewise, after treatment, queens were monitored daily by ultrasonography for 10 days and weekly until the end of gestation to obtain gestational sacs measurements (GS), fetal measurements, and fetal biophysical profile. Data were analyzed by ANOVA. Serum P4 concentrations were significantly different on Day 6 (EXP I) and on Day 1 (EXP II) in ALI and CLO groups compared with PLA group (P < 0.05 and P < 0.01; respectively). The ultrasonographic monitoring during treatment allowed assessing changes in the GS and fetal measurements, embryo-fetal viability, and risk of pregnancy loss. In conclusion, the results from this study reported changes in serum P4 concentration and in ultrasonography measurements during pregnancy interruption with ALI or CLO treatment. Also it was observed that ALI and CLO are safe drugs and can preserve posttreatment queen fertility. Therefore, the results obtained in our work will be applied in feline reproduction practice.

Three experiments were designed to evaluate the effect of different circulating progesterone (P4) concentrations during synchronization of ovulation protocol for timed artificial insemination of seasonal anestrous buffalo cows. In the first trial, ovariectomized cows were randomly allocated into one of three groups: using new P4 devices (G-New; n = 8), using devices previously used for 9 days (G-Used1x; n = 8), and using devices previously used for 18 days (G-Used2x; n = 8). The P4 device was maintained for 9 days, and the circulating P4 concentration was measured daily. The circulating P4 concentrations during the P4 device treatment were the lowest for G-Used2x (1.10 ± 0.04 ng/mL), intermediate for G-Used1x (1.52 ± 0.05 ng/mL), and the highest for G-New (2.47 ± 0.07 ng/mL; P = 0.001). In the second trial, 31 anestrous cows had their ovarian follicular dynamics evaluated after receiving the treatments described previously (G-New [n = 10], G-Used1x [n = 11], and G-Used2x [n = 10]). At insertion of the P4 device, cows were administered 2.0 mg of estradiol benzoate. Nine days later, the P4 device was removed and cows were administered 0.53 mg of cloprostenol sodium plus 400 IU of eCG. Forty-eight hours after P4 device removal, 10 μg of buserelin acetate was administered. There were no differences among the groups (G-New vs. G-Used1x vs. G-Used2x) in diameter of the largest follicle at P4 device removal (9.0 ± 0.8 vs. 10.1 ± 0.9 vs. 8.6 ± 0.8 mm; P = 0.35), in interval from P4 device removal to ovulation (77.1 ± 4.5 vs. 76.5 ± 4.7 vs. 74.0 ± 4.4 hours; P = 0.31), or in ovulation rate (80.0% vs. 81.8% vs. 60.0%; P = 0.51). In experiment 3, 350 anestrous cows were randomly assigned into one of the three treatments described previously (G-New, n = 111; G-Used1x, n = 121; G-Used2x, n = 118) and received a timed artificial insemination for 16 hours after buserelin treatment. The 30-day pregnancy rates did not differ among groups (55.9% vs. 55.4% vs. 48.3%; P = 0.39). Thus, the low circulating P4 concentrations released from a used P4 device efficiently control the ovarian follicular growth and had no detrimental effect on the pregnancy rates of the seasonal anestrous buffalo cows.

We aimed to evaluate the reproductive performance of Nelore lactating cows submitted to a resynchronization 12 days after timed artificial insemination (TAI) with or without a long-acting progesterone (P4-LA) treatment. Nelore cows were submitted to a P4/oestradiol-based TAI protocol (D0 = insemination). On D12, cows in the control group (n = 184) received a new P4 intravaginal device (0.96 g), whereas cows in the P4-LA group (n = 192) received the P4 device and 75 mg P4-LA. Cows identified as non-pregnant (n = 120) by regression of corpus luteum using colour Doppler ultrasonography on D20 had the P4 device removed and received 500ug of sodium cloprostenol, 1 mg of oestradiol cypionate and 300 IU of eCG and were re-inseminated on D22. There was no difference (p > 0.10) in the pregnancy rate at D20, D30 and D60 after first TAI between the control (69%, 59.7% and 57%, respectively) and P4-LA (67%, 55.7%, and 55.2%, respectively) groups. Pregnancy losses were similar between both groups (p > 0.1). For cows submitted to the second TAI, the pre-ovulatory follicle size did not differ (p > 0.1), but the oestrous detection and pregnancy rates were greater (p < 0.05) in the P4-LA group (92.2% [59/64] and 60.9% [39/64], respectively) than in controls (75% [42/56] and 44.6% [25/56]). The cumulative pregnancy rate after two TAIs did not differ (p > 0.1) between control (73.3% [135/184]) and P4-LA (76% [146/192]) groups. The use of P4-LA at 12 days after TAI potentially increases the pregnancy rates for a new early resynchronization strategy associated with the Doppler imaging for pregnancy diagnosis and results in an alternative to perform two TAIs in 22 days in beef cows.

This study aimed to evaluate the effect of recombinant bovine somatotropin (bST) in combination with progesterone (P4) and estradiol benzoate (EB) on ovarian follicular dynamics using a protocol for estrus and ovulation synchronization in crossbred Bos taurus taurus cows. Twenty-four non-lactating multiparous cows were randomly assigned to two groups: the recombinant bovine somatotropin group (GbST; n = 11) received an intravaginal P4 device (1.5 g), estradiol benzoate (EB = 1.0 mg IM), bST (500 mg SC), and an ovarian ultrasonography (US) on day zero (d0 = beginning of the study); d-cloprostenol (150 μg, IM), US, and P4 removal on d8; 1.0 mg of EB (IM) on d9; and US on d10 and d15. On the other hand, to the control group (GC; n = 13), the same protocol as the GbST was applied, except for the non-receipt of bST on d0. The follicles were measured and evaluated on d0, d8, and d10, as were the corpora lutea (CL) on d15 (using ultrasonography). The effect of the two treatments (GbST vs. GC) on the follicle size, CL (F-test), and ovulation rate (logistic regression) were evaluated. The GbST showed a greater follicle diameter on d10 (14.5 mm) than the GC (12.1 mm; P < 0.03), as well as a greater diameter of CL on d15 (19.7 vs. 16.9 mm, P < 0.01). In addition, in the former, the ovulation rate (90.9 vs. 69.2%, P = 0.09) was observed to be greater. It was concluded that the combination of bST, P4, and EB in synchronization for estrus and ovulation protocols significantly increased the diameter of the preovulatory follicle, produced a higher follicular growth rate, and a greater diameter of the corpus luteum. Additionally, there was a higher percentage of cows with ovulation compared to the group that did not receive bST.

The synthetic progestagen, medroxyprogesterone acetate (MPA), was administered to sows in late pregnancy with the objective of slightly delaying the time of farrowing and thereby providing more marked associations between hormonal changes and the termination of pregnancy, and the initiation of farrowing and lactation in this species. MPA was administered orally (140 mg, twice daily) to eight sows in late pregnancy on days 112, 113 and 114 of gestation. Parturition was then induced to occur on day 116 by injecting 200 micrograms cloprostenol i.m. on day 115 of gestation. The peripartum changes in the plasma concentrations of progesterone, cortisol, oestradiol-17 beta, relaxin, prolactin, lactose and 13,14-dihydro-15-keto prostaglandin F2 alpha (PGFM) were measured in these sows together with a group of untreated sows. The gestational length for the MPA-treated sows (116.3 +/- 0.3 days, mean +/- S.E.M.) was significantly (P less than 0.01) greater compared with the untreated sows (114.9 +/- 0.3 days). Plasma progesterone declined earlier (P less than 0.05) with respect to the time of parturition in the treated sows compared with the untreated group. With respect to the timing of parturition, the time at which maximal concentrations of relaxin were attained and the timing of the subsequent decline were earlier in the MPA-treated sows. In both groups of sows, the concentration of relaxin increased before the decline in plasma progesterone. In the untreated sows, the concentration of PGFM increased either slightly before or at the same time as the decline in plasma progesterone, whereas in sows treated with MPA, progesterone concentrations began to decline before any significant increase in the plasma concentration of PGFM. The profiles of cortisol, oestradiol-17 beta and PGFM were similar in both groups of sows. In both groups of sows, the timing of the initial increase in the concentration of plasma prolactin coincided with a similar rise in plasma lactose (P less than 0.01). Plasma progesterone either declined earlier or at the same time as the rise in plasma lactose (P less than 0.01) in the treated group of sows only. We conclude that since the prepartum changes in the concentration of progesterone and relaxin occurred before significant changes in the concentration of PGFM in the MPA-treated sows, the nature of the luteolytic factor and the mechanism by which it exerts its action remains obscure. The higher concentration of lactose in the mammary secretion at birth in the MPA-treated sows compared with the untreated group suggested that lactogenesis was initiated earlier with respect to parturition following MPA treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

The objective was to determine the effects of eCG given on the day of, or 2 days before removal of an intravaginal progestin device, on ovarian follicle diameter, luteal volume, serum progesterone (P4) concentrations, and pregnancy per insemination in a fixed-time AI (FTAI) protocol. Lactating, anestrous, multiparous Bos taurus cross beef cows, 40 to 60 days postpartum, were given estradiol benzoate (2 mg im) and a progestin intravaginal device containing 250 mg of medroxyprogesterone acetate on Day 0 and cloprostenol (0.265 mg) on Day 6. Intravaginal devices were removed on Day 8 and GnRH (100 μg im) was given on Day 9, with timed AI 16 hours later. In experiment 1, cows were randomly assigned to receive 400 IU im eCG on Day 6 (eCG6; N = 8) or Day 8 (eCG8; N = 8), or to not receive eCG (control; N = 8). Dominant follicle diameter on Day 9 in the eCG6 group (10.0 ± 0.5 mm) was larger (P < 0.05) than in the eCG8 (8.6 ± 0.2 mm) or control (8.5 ± 0.4 mm) groups. Corpora lutea (CL) in all cows in the control group underwent premature luteolysis within 10 days after ovulation. Luteal volumes and P4 concentrations 10 and 15 days after ovulation were higher (P < 0.05) in the eCG6 group than in the eCG8 group. In experiment 2, the eCG6 (N = 121) and eCG8 (N = 125) protocols were compared in lactating anestrous cows that underwent FTAI. Pregnancy rate was higher (P < 0.05) in the cows that received eCG on Day 6 (27.3%; 33/121) than on Day 8 (16.0%; 20/125). Furthermore, CL volumes and P4 concentrations were higher (P < 0.05) in the eCG6 group (5784.0 ± 857.3 mm(3) and 8.1 ± 1.3 ng/mL, respectively) than in the eCG8 group (3220.9 ± 505.1 mm(3) and 4.5 ± 0.7 ng/mL, respectively). We concluded that eCG given 2 days before progestin removal in this FTAI protocol for anestrous beef cows increased diameter of the dominant follicle, luteal volume, serum P4 concentrations, and pregnancy rates.

In wintertime 7 nonpregnant cows (3 nonlactating and 4 milk secreting less than 3 liter/day) and 3 heifers were treated:day 1 cloprostenol (530 microgram); day 2 progesterone capronate (0,25/Kg); days 3 to 5 progesterone (0,25 mg/Kg)+ estradiol valerianate (0,01 mg/Kg) and reserpine (0,01 mg/Kg); days 6 to 8 progesterone (0,25 mg/Kg) + estradiol (0,2 mg/Kg) and reserpine (0,01 mg/Kg); day 9 betametasone acetate (0,2 mg/Kg) and phosphate (0,55 mg/Kg); days 9 to 16 estradiol (0,0075 mg/Kg). 9 days later the treatment started again. In all the period (5/12-25/2) the animals where machine milked. 2 lactating nonpregnant cows where kept as control. The milk secretion started in nonlactating animals but the peak daily milk yield was 3 liter about only. In lactating animals the yield no increased. The second treatment (and the first in lactating cows) induced secreting less milk with more fat and protein. The low milk yields was associated to a season's negative effect.

Two experiments were performed to evaluate the reproductive performance of zebu beef cows treated with different doses of eCG at the end of a progesterone (P4)/estrogen based protocol for timed artificial insemination (TAI). In Experiment 1, suckling Bos indicus Nelore cows (n = 261) received, on day 0, a progesterone (P4) intravaginal device (PD) and an injection of 1 mg estradiol benzoate (EB). On day 8, the PD was removed, 500 μg of cloprostenol was injected, and cows were assigned to one of the following groups: Control (no treatment), 300 (300 IU of eCG), 600 (600 IU of eCG), and 900 (900 IU of eCG). On day 9, all cows received 1 mg EB and TAI performed 54-56 h after cloprostenol injection. A pregnancy diagnosis was done by ultrasound scanning 40 days after TAI, and the number of fetuses and calves was recorded at pregnancy diagnosis and at birth. More cows treated with eCG displayed estrus within 48 h after removal of the PD (42.3% vs. 11.6%, P < 0.01), and ovulated more than one follicle (42%, 58/138 vs. 1.8%, 1/54; P < 0.01). This effect on ovulation rate was dose dependent (P < 0.05). The pregnancy rate was affected only by cow parity (primiparous, 25.3% vs. multiparous, 48.9%; P < 0.01). Twin pregnancy was higher (P < 0.01) in cows treated with eCG (42%, 58/138) than controls (0%, 0/54). However, few cows (33.3%) were able to keep both fetuses intact until birth. For evaluation of ovarian characteristics by B-mode and Doppler ultrasonography, 43 Nelore cows were submitted In Experiment 2 to the same four groups described in Experiment 1. Although no difference (P>> 0.1) was observed for size and blood perfusion in the pre-ovulatory follicles, corpus luteum was larger and with greater blood perfusion (P < 0.05) in eCG-treated cows. In conclusion, eCG increased the number of double/multiple ovulations in a dose-dependent manner, induced larger and more vascularized corpora lutea, but did not affect the fertility of cyclic or anestrous cows. Although eCG results in twin pregnancies, most of cows underwet embryo/fetus loss and birth a single calf.

The aim of this study was to investigate the effects on follicle stimulating hormone (FSH) secretion and dominant follicle (DF) growth, of treatment of Bos indicus heifers with different combinations of intra-vaginal progesterone releasing devices (IPRD), oestradiol benzoate (ODB), PGF2α and eCG. Two-year-old Brahman (BN; n=30) and Brahman-cross (BNX; n=34) heifers were randomly allocated to three IPRD-treatments: (i) standard-dose IPRD [CM 1.56g; 1.56g progesterone (P4); n=17]; (ii) half-dose IPRD (CM 0.78g; 0.78g P4; n=15); (iii) half-dose IPRD+300IU eCG at IPRD removal (CM 0.78g+G; n=14); and, (iv) non-IPRD control (2×PGF2α; n=18) 500μg cloprostenol on Days -16 and -2. IPRD-treated heifers received 250μg PGF2α at IPRD insertion (Day -10) and IPRD removal (Day -2) and 1mg ODB on Day -10 and Day -1. Follicular dynamics were monitored daily by trans-rectal ultrasonography from Day -10 to Day 1. Blood samples for determination of P4 were collected daily and samples for FSH determination were collected at 12h intervals from Day -9 to Day -2. A significant surge in concentrations of FSH was observed in the 2×PGF2α treatment 12h prior and 48h after follicular wave emergence, but not in the IPRD-treated heifers. Estimated mean concentrations of total plasma P4 during the 8 days of IPRD insertion was greater (P<0.001) in the CM 1.56g P4 treated heifers compared to the CM 0.78g P4 treated heifers (18.38ng/ml compared with 11.09ng/ml, respectively). A treatment by genotype interaction (P=0.036) was observed in the mean plasma P4 concentration in heifers with no CL during IPRD insertion, whereby BN heifers in the CM 1.56g treatment had greater plasma P4 than the BNX heifers on Days-9, -7, -6, -5, and -4. However, there was no genotype effect in the CM 0.78g±G or the 2×PGF2α treatment. Treatment had no effect on the DF growth from either day of wave emergence (P=0.378) or day of IPRD removal (P=0.780) to ovulation. This study demonstrates that FSH secretion in B. indicus heifers treated with a combination of IPRD's and ODB to synchronise ovulation was suppressed during the period of IPRD insertion but no significant effect on growth of the DF was observed.

Three experiments evaluated ovarian dynamics and circulating progesterone (P4) during P4-based protocols initiated with GnRH, estradiol benzoate (EB), or no additional treatment in Nelore (Bos indicus) cattle. In Exp 1 (n = 59 cows), a 5-d P4-only protocol (P-5d; D0: P4 implant alone (1g); D5: P4 removal, 0.5 mg estradiol cypionate [EC], 0.526 mg cloprostenol [PGF], and 300 IU equine chorionic gonadotropin [eCG]; D7: 8.4 μg buserelin acetate [GnRH]) was compared to a 9d protocol initiated with EB (EB-9d; D0: 2 mg EB + P4; D9: P4 removal + EC + PGF + eCG), and to a 7d GnRH protocol (G-7d; D0: 16.8 μg GnRH + P4; D6: PGF + eCG; D7: P4 removal + PGF; D9: GnRH). Exp 2 (n = 55 cows) compared G-7d and EB-7d protocols (similar to EB-9d, but D9 treatments were done on D7). Exp 3 (n = 64 heifers) compared EB-7d, G-7d, and P-5d protocols. For all experiments, daily ovarian ultrasonography was done from D0 until 4d after implant withdrawal and blood samples were collected at D0 and first PGF. Follicle dynamics were determined for each individual animal, analyzed within individual experiments, and afterwards combined to determine overall effects of treatments. The protocol that began with GnRH, G-7d, had greater ovulation rate after D0 with subsequently greater number of CL and circulating P4 at time of PGF (52.8%, 1.0 ± 0.1 CL, 4.0 ± 0.4 ng/mL) than for EB protocols (12.1%, 0.4 ± 0.05 CL, 2.0 ± 0.2 ng/mL), or P-5d (2.5%, 0.6 ± 0.09 CL, 2.6 ± 0.3 ng/mL). The G-7d and EB protocols had synchronized follicle wave emergence in 92.1% of animals but with distinct patterns. For the G-7d group, wave emergence occurred earlier in ovulating than non-ovulating animals (1.4 ± 0.2 d vs 2.5 ± 0.4 d). By comparison, most animals in EB-7d or EB-9d (80.3%) displayed atresia of the dominant follicle, followed by wave emergence 2-3 d after EB treatment. In contrast, P-5d protocol synchronized wave emergence in only 30.0% of cows. Nevertheless, no differences among treatments were detected for ovulation at end of the protocol (85.7%). In conclusion, the P-5d protocol did not synchronize follicle wave emergence but produced similar final ovulation, whereas, GnRH and EB protocols had follicle dynamics synchronized by distinct mechanisms that produced differences in CL number and P4 at the time of PGF treatment but similar final ovulation. Based on ovarian function, each of these synchronization methods are promising for use in FTAI, although fertility still needs to be evaluated.

Three groups of five lactating dairy cows in the mid-luteal phases of oestrous cycles were given an injection (at time 0 h) of the naturally-occurring prostaglandin F2 alpha (PGF2 alpha) or cloprostenol (a synthetic analogue of PGE2 alpha) at doses recommended for inducing luteolysis, or injection vehicle. Concentrations of glucose and hormones in jugular plasma were measured from 26 h before to 12 h after the injections and the significance (P < 0.05) of the effects of the prostaglandins on these concentrations was determined. Both prostaglandins induced falls in progesterone concentration and rises in luteinizing hormone concentration; neither influenced follicle-stimulating hormone. PGF2 alpha increased glucose concentration; neither prostaglandin influenced insulin concentration. Both prostaglandins increased growth hormone concentration and resulted in declining thyroxine concentration. PGF2 alpha increased prolactin and cortisol concentration. There were, however, no significant differences between the effects of the two prostaglandins on any hormone (or glucose) concentration.