BACKGROUND

D-cloprostenol is a synthetic PGF2α, commonly used in bovine reproduction, that increases myometral contractility. However, little is known regarding its contractile behaviour and how it depends on the reproductive state and uterine topography (regions and muscular layers).

OBJECTIVE

These aspects would affect the action of d-cloprostenol on the uterus. Therefore, we hypothesize a possible use of this drug at the time of artificial insemination, to improve conception rates and, in the post-partum, in order to accelerate uterine involution in dairy cattle. The purpose of the present study was to investigates the modulatory effect of d-cloprostenol on contractility of the bovine uterine region (horn and corpus) and their muscle layers (circular and longitudinal), in follicular and luteal phases. To our knowledge, motility effects of d-cloprostenol on different regions from healthy bovine uterus have not been described up to now.

METHODS

Uterine specimens were collected from uterine body and horn of cattle in the follicular (n = 28) and luteal phase (n = 32) of the estrous cycle at slaughter. Two strips were prepared from each regions corresponding to the circular and the longitudinal muscular layers, respectively. Samples were cultured in an organ bath, exposed to synthetic prostaglandin (1 μM d-cloprostenol) and their contractile activity was monitored for 10 min. The functionality of the strip throughout the experiment was tested by a dose of carbachol (10-5 M).

RESULTS

The mean basal amplitude of contractions was higher in the follicular compared to the luteal phase in uterine horn samples, but not in muscles collected from the uterine body. The amplitude of contractions increased after d-cloprostenol administration in all tissues with a greater increase in samples from cattle in the follicular phase. The frequency of contractions increased after d-cloprostenol administration in longitudinal but not in circular fibrees.

CONCLUSIONS

The contractile responses to d-cloprostenol in both horn and corpus were strongest in the circular muscles but weak in the longitudinal muscles.

A major trend in fine chemicals and pharmaceuticals is the synthesis of molecules with increased complexity. This trend translates the aim of organic syntheses to conditions in which high degrees of chemo-, regio- and stereoselectivity can be provided. In this context, the chemoselective hydrogenation of one functional group in the presence of other reactive groups is a frequently encountered problem in fine chemicals manufacture. This study provides a critical analysis including elegant examples of reactions in which high chemo- and diastereoselectivities were achieved in the hydrogenation of a C=O group in the presence of C=C double bond. A particular emphasis is addressed to the stereoselective C(15) synthesis from Cloprostenol--a PGF2α structural analogue.

BACKGROUND

Previous surveys reported a positive association between the length of the follicular phase and subsequent fertility in embryo transfer donor and Thoroughbred mares. However, it is unclear whether a longer oestrus positively influences fertilisation and oviductal development (oocyte quality, oviductal environment), or uterine receptivity and survival of the embryo in the uterus.

OBJECTIVE

To determine the effect of length of oestrus (characterised by duration of endometrial oedema) on likelihood of pregnancy and early embryo loss (EEL) in recipient mares after embryo transfer (ET).

METHODS

Retrospective clinical study.

METHODS

A total of 350 embryos recovered from 161 donor mares were transferred into 231 recipient mares during three consecutive breeding seasons. The following variables were analysed via two binary logistic regression models to determine their effect on pregnancy and EEL: 1) year of transfer, 2) season of transfer, 3) age of the recipient mare, 4) age of the donor mare, 5) operator performing the transfer, 6) singleton or twin embryo, 7) embryo size, 8) number of transfers to a given recipient in any one season, the use of 9) d-cloprostenol and 10) hCG in the recipient mare, 11) day of ovulation of the recipient mare at ET, 12) number of corpora lutea (CLs) at ET, and 13) duration of oestrus in the recipient mare.

RESULTS

Age of the donor mare (P = 0.01), operator (P = 0.008), number of CLs at ET (P = 0.05) and the number of days of endometrial oedema during the oestrus preceding ET to the recipient mare (P = 0.004) influenced the likelihood of pregnancy. Early embryonic loss was influenced only by the year of transfer (P = 0.014).

UNASSIGNED

Retrospective design of the study. The involvement of several veterinary surgeons over the 3-year period could have affected data recording.

CONCLUSIONS

The likelihood of pregnancy in recipient mares is positively correlated with the duration of endometrial oedema during the oestrus preceding ET. This suggests a role for an adequate duration of oestrogenic priming during oestrus on uterine receptivity and embryo survival.

The objectives of this study were to evaluate the performance of the SCR eSense ear tag automated activity monitor (AAM) to detect estrus behavior in Holstein heifers and to determine the optimal time from estrus alert to artificial insemination (AI) using sex-sorted or conventional semen. In total, 281 heifers were fitted with the AAM once eligible for breeding (>13.5 m of age). For the first AI, estrus was synchronized using 500 μg of cloprostenol (PGF), given 14 d apart, and heifers were given estrus detection patches (Estrotect™) after the second PGF. Heifers were inseminated at randomly attributed times after high activity alert from the AAM system or if the estrus patch had ≥ 50% colour change. Most heifers received sex-sorted semen for the first AI and conventional semen for subsequent inseminations. Pregnancy diagnosis was performed at 30 d post AI and heifers had four opportunities to become pregnant. In a subset of heifers (n = 149), ovaries were scanned every 12 h from the time of AI until ovulation (OV). The system recorded a heat index (measure of estrus strength), maximum activity change, maximum rumination change and duration of high activity. The sensitivity was 91.0%, with a false positive and false negative rate of 8.0%, and the positive predictive value to detect true estrus events was 83.5%. Pregnancy per AI to first AI was 67.6% and 97.9% of heifers become pregnant after four inseminations. Most false positive estrus events had a heat index < 45 and a rumination change < -20, while false negative events had a rumination change ≥ -20. Odds of pregnancy was not associated with any estrus characteristics measured by the system. However, pre-ovulatory follicle diameter had a weak correlation (r < 0.25) with all estrus characteristics. The average (range) interval of onset of high activity, peak activity and end of high activity to OV was 28 h (16-46 h), 22 h (10-40 h) and 16 h (0-36 h), respectively. For conventional semen, each hour increase in interval from activity onset or peak activity to AI reduced the predicted probability of pregnancy by 3.8 and 4.2%, respectively. For sex-sorted semen, the relationship between activity onset or peak activity to AI and predicted probability of pregnancy was quadratic, but not significant. Overall, the SCR eSense ear tag AAM performed well and strategies to identify false positive and false negative estrus events, along with optimization of timing of AI, should further improve performance in Holstein heifers.

Keywords: Estrus detection; Follicle diameter; Ovulation interval; Pregnancy per AI; Sex-sorted semen.

Dairy cows were injected with 1 alpha-hydroxycholecalciferol (1 alpha-HCC) and, or, cloprostenol at 275 days of gestation. Blood samples were taken daily from 270 days of gestation until seven days after parturition and analysed for calcium, inorganic phosphate, magnesium and hydroxyproline. In all treated and control cows concentrations of calcium, inorganic phosphate and magnesium decreased around the time of parturition. Concentrations of hydroxyproline increased from the second to the fourth day after parturition. This increase was slightly smaller in cows injected with cloprostenol but was unaffected by 1 alpha-HCC. There was a greater indicence of retained placenta and endometritis in cows receiving cloprostenol. The injection of cloprostenol with 1 alpha-HCC at 275 days of gestation did not prevent milk fever.

The use of tail chalk and estrus/heat expression scores (HEATSC) evaluation is instrumental in identifying cows with greater estrus expression and greater artificial insemination pregnancy rates (P/AI) in cows submitted to timed artificial insemination (TAI), and cows with low or no estrus expression present lower P/AI. It was intended in this study to improve the pregnancy rates in TAI for Bos indicus beef cows, and gonadotrophin-releasing hormone (GnRH) injection was hypothesized to increase pregnancy rates in a TAI program for cows submitted to progesterone-estradiol-based protocols with low or no estrus expression, evaluated by HEATSC. Cows (n= 2284) received a progesterone device and 2 mg estradiol benzoate, after 8 days the device was removed and 1 mg estradiol cypionate, 150 μg of d-cloprostenol and 300 IU equine chorionic gonadotropin was administered. All cows were marked with chalk and HEATSC evaluated (scales 1 to 3) at TAI performed on day 10. Animals with HEATSC1 and HEATSC2 (n= 937) received 100 μg de gonadorelin (GNRH group; n= 470), or 1 ml saline (Control group; n= 467), and cows with HEATSC3 (named HEAT group; n= 1347) received no additional treatment. The larger dominant follicle, evaluated on day 8and at TAI (day 10), was greater in HEAT group (P= 0.0145 and P <0.001, respectively). Corpus luteum (CL) area and progesterone concentration was evaluated on day 17, and CL area was larger in HEAT group, intermediary in Control and lower in GnRH group (Control= 2.68 cm2, GnRH= 2.37 cm2, HEAT group= 3.07 cm2, P <0.001). Greater progesterone concentrations were found in HEAT group than in Control and GnRH groups (Control= 4.74 ng/ml, GnRH= 4.29 ng/ml, HEAT group= 6.08 ng/ml, P<0.001). There was a difference in ovulation rate, greater in HEAT group than GnRH and Control groups (Control= 72.5%; GnRH= 81.25%; HEAT group= 90.71%; P= 0.0024). Artificial insemination pregnancy rates was greater in HEAT group (57.09% (769/1347) than in Control and GNRH groups, with positive effect of GnRH injection at the time of TAI in P/AI (Control= 36.18% (169/467), GnRH= 45.95% (216/470); P<0.0001). In conclusion, GnRH application in cows with low HEATSC (1 and 2) is a simple strategy, requiring no changes in TAI management to increase pregnancy rates in postpartum beef cows submitted to progesterone-estradiol-based TAI protocols, without reaching, however, the pregnancy rates of cows that demonstrate high estrus expression at the TAI.

The syntheses of five compounds isomeric with the potent luteolytic agent cloprostenol are described. These are the trans-delta 5, cis and trans-delta 4, cis-delta 6 (methyl ester) and cis-delta 13 analogues. The cis-delta 4 isomer is as potent as cloprostenol as a luteolytic agent in hamsters but the others are markedly less so.

Background: Farrowing induction with prostaglandin F2 analogue cloprostenol is commonly used on commercial farms to manage the timing of farrowing. When labour induction is applied, the questions arise about possible side effects of such a hormonal intervention on physiological processes connected with labour and lactation, including colostral immunity.

Results: In this study, immune cells composition, lysozyme concentration, complement bacteriolytic activity and proinflamatory (GM-CSF2, IL-1β, IL-6, a TNFα) and anti-inflammatory (IL-4, IL-10, TGFβ1 a TGFβ2) cytokines were measured in colostrum samples from sows farrowing naturally (NP) and from sows with farrowing induced using cloprostenol administration on day 113 of gestation (IP). A significantly higher proportion of lymphocytes was found in colostrum of induced sows compared to colostrum of non-induced sows. No significant differences between NP and IP were found in complement activity, in the proportions of granulocytes, macrophages and lymphocyte subpopulations. Lower lysozyme concentration and higher IL-1β, IL-6, TGFβ1 and TNFα concentrations were found in IP sow colostrum compared to colostrum from NP sows.

Conclusions: An increased proportion of colostral lymphocytes can positively influence the cellular immunity transmission from sow to her offspring. On the other hand, a lower lysozyme concentration can adversely affect newborn's intestinal immunity, as well as changes in cytokine concentrations can have an adverse effect on newborn piglet intestinal epithelium development and its defence function.

Keywords: Colostrum; Complement; Cytokines; Lymphocytes; Lysozyme; Sow.

The aim of the present study was to evaluate the application of a GnRH-PGF_2α based synchronization and superstimulation protocol for fixed-time natural mating in llama embryo donors. All females (n = 8) received 8 μg IM of GnRH analog (GnRHa; buserelin) on day 0, regardless of follicular status. After eight days, another GnRHa dose was administered followed by 250 μg IM PGF_2α (cloprostenol). A dose of 1000 IU IM of equine chorionic gonadotrophin (eCG) was applied on day 12 and a new dose of PGF_2α was administered on day 13. All embryo donors were mated with a male of proven fertility followed by a GnRHa dose on day 18. 24 h later, mating was repeated with a different male. Transcervical uterine flushing for embryo recovery was carried out on all females on day 26. Recipient females received one dose of GnRHa (day 0) two days after the first mating of embryo donor females. A 75% (6/8) of embryo donors responded to the superstimulation treatment with a range of 2 to 5 corpus luteums (CLs) on embryo recovery day. A total of 24 CLs were registered, with a mean of 4 ± 0.9 CLs per female. Embryo recovery rate was 66.7% (16/24), with a range of 0 to 4 embryos and a mean of 2.7 ± 1.5 embryos per female. Regarding quality of the recovered embryos, 56.2% were grade I, 6.2% were grade II and 37.5% were grade V (untransferable; arrested morulae). Grade I and II embryos (n = 10) were transcervically transferred into recipient females (n = 10) six days after inducing their ovulation. At 24 days after embryo transfer (ET), a 50% pregnancy rate was registered. In conclusion, a group of llama embryo donors can be synchronized and superstimulated using a fixed-time mating protocol based on GnRHa, PGF_2α, and eCG without the necessity of using ultrasonography in the field.

Keywords: camelids; embryo transfer; follicular wave; ovarian dynamic; ovarian superstimulation.

Two experiments were conducted to study effects of cloprostenol sodium (cloprostenol) and clenbuterol HCl (clenbuterol) during postpartum anestrus on subsequent reproductive performance in cows. In Experiment I, 96 cows received either 0.5 mg cloprostenol (PGF, n = 25), 364 mg clenbuterol (CLEN, n = 24), 0.5 mg cloprostenol and 364 mg clenbuterol (CLEN+PGF, n = 21) or no treatment (Control, n = 26) on Day 20 post partum. Treatments failed to influence postpartum interval, pregnancy rate or the incidence of short estrous cycles preceding the first normal estrous cycle. In Experiment II, anestrous cows were administered cloprostenol (0.5 mg) on either Day 20 (PGF20, n = 27) or Day 35 post partum (PGF35, n = 25), or served as untreated controls (Control, n = 26). Neither postpartum interval nor pregnancy rate were affected by cloprostenol treatment. In conclusion, treatment of postpartum cows with PGF did not alter the resumption of normal estrous cycles following parturition.

Specific receptors for 125I-labelled hCG in ovarian follicle wall were located in the theca interna. No specific binding of 125I-labelled hCG was found in theca externa and/or stromal tissue. The kinetics of 125I-labelled hCG binding to theca interna followed second order kinetics with calculated association rate constants (ka +/- s.d.) of 1.57 +/- 0.16 X 10(6) and 0.57 +/- 0.02 X 10(6) litres mol-1 sec-1 at 37 degrees C and 22 degrees C respectively. Dissociation of specifically bound 125I-labelled hCG from theca interna was minimal at 37 degrees C and 22 degrees C. The binding of 125I-labelled hCG to theca interna could be displaced with PMSG, FSH-P and sheep LH but other sheep pituitary hormones and LH-releasing hormone showed little or no cross-reaction. The calculated binding capacities (Bmax) and equilibrium dissociation constants (Kd) for 125I-labelled hCG binding to theca interna did not differ between Romney ewes and Booroola x Romney ewes with and without the fecundity (F) gene on Day 10 of the oestrous cycle, during anoestrus or at 36 h after an injection of cloprostenol on Day 10 of the oestrous cycle. When the data for Day 10 and anoestrus were pooled, the median (range) Bmax and Kd values in non-atretic follicles (greater than or equal to 3 mm diameter) were 12.0 (5.1-23.5) fmol/mg protein and 0.10 (0.05-0.16) nM respectively. At 36 h after cloprostenol injection the respective median (range) Bmax and Kd values in non-atretic follicles (greater than or equal to 3 mm diam.) increased to 46.9 (28.4-70.3) fmol/mg protein and 0.23 (0.13-0.65) nM respectively. In corpora lutea the hCG binding characteristics were similar in all the above breeds/genotypes. On Day 10 of the cycle, the mean Bmax but not the mean Kd value was significantly higher (P less than 0.01) than the corresponding value at 36 h after cloprostenol injection. In granulosa cells, from follicles of greater than or equal to 5 mm diameter of Romney and Booroola x Romney (++) ewes and from follicles of greater than or equal to 3 mm diameter of Booroola x Romney (F+) ewes, the hCG binding characteristics were similar. In granulosa cells from smaller sized follicles from the above breeds/genotypes, no specific hCG binding was noted.

The use of exogenous progestagens for estrus synchronization in cattle can result in a persistent dominant follicle which is associated with reduced fertility. We examined whether the LHRH agonist, deslorelin, would prevent the formation of a persistent follicle in heifers synchronized with norgestomet. The estrous cycles of heifers were synchronized with cloprostenol, and on Day 7 of the ensuing cycle the heifers received one of the following treatments for 10 d: Group C (n = 5), untreated control; Group N (n = 6), injection of a luteolytic dose of cloprostenol on Days 7 and 8 and implant of norgestomet from Day 7 to Day 17 (i.e. typical 10-day norgestomet implant period); Group D (n = 6), injection of cloprostenol on Days 7 and 8 and implants of deslorelin from Day 7 to Day 17; Group ND (n = 6), injections of cloprostenol and both norgestomet and deslorelin implants as above. Follicle growth was monitored using ultrasonography. Group-N heifers showed continued follicle growth and had larger follicles on Day 17 of the cycle than Group-C heifers (16.8 +/- 1.6 and 10.4 +/- 1.6 mm). Follicle growth for Group-D and ND heifers was similar and variable, and seemed to depend on follicle status at the initiation of treatment. Heifers with follicles of 5 to 10 mm (n = 9) in diameter either showed no follicle growth (2 9 ) or developed large follicles (7 9 ), while heifers with follicles approximately 12 mm (n = 3) in diameter showed follicle atresia with no further significant growth. On Day 17, size of the largest follicle was similar for Group-ND (14.3 +/- 2.9) and Group-D (16.8 +/- 1.6) heifers. Heifers in Group N showed estrous behavior 1.8 +/- 0.2 d after treatment, whereas heifers in Groups D and ND did not show estrus for 2 to 4 wk. The results show that combined treatment with progestagen and an LHRH agonist does not consistently prevent the development of a persistent dominant follicle and that return to estrus can be delayed after treatment with an LHRH agonist.

Several studies in dairy cattle have investigated the final outcome of different treatment regimens in follicular cyst condition. However, sequential monitoring of the response of follicular cysts to these treatments is rather scanty. In this paper, we present the response of a large follicular cyst in a pluriparous crossbred dairy cow with prolonged conception failure to human chorionic gonadotropin, hCG (3,000 IU; day 0) and cloprostenol (500 μg; day 9) treatment. Using transrectal ultrasonography (USG), reproductive tract was imaged daily beginning day 0 until day 11. The follicular cyst showed a consistent regression to a very small anechoic area on day 7 and was undetectable thereafter. Concurrently, there was development of a new dominant follicle that was first detected on day 4 and showed progressive growth to preovulatory stage. The cow was inseminated and ovulation occurred, as diagnosed by the presence of a corpus luteum (CL) 7 days later, but conception did not occur. The animal was re-inseminated after estrus detection in the estrous cycle that immediately followed. Pregnancy diagnosis was performed on 30 and 60 days post-insemination (DPI) and the cow was confirmed to be pregnant. This paper underscores the importance of diagnostic ultrasound in veterinary medicine, especially in the management of reproductive problems.

OBJECTIVE

Bovine ovarian cysts are a common cause of economic loss in modern dairy herds. The objective of the present study was to evaluate the reproductive responses to three protocols using hCG, GnRH and cloprostenol when the definite diagnosis of the type of ovarian cyst is/is not possible in dairy cows.

METHODS

A total of 144 lactating dairy cows with ovarian cysts were divided into three groups. At diagnosis (Day 0), cows in Group 1 (the conventional method, n=47) were injected with 0.02 mg of a GnRH analogue i.m. (Buserelin); cows in Group 2 (n=47) were intramuscularly treated with 0.02 mg Buserelin plus 500 µg cloprostenol; and cows in Group 3 (n=50) were intramuscularly treated with 1500 IU hCG plus 500 µg cloprostenol. All cows received 500 µg cloprostenol intramuscularly on Day 10.

RESULTS

No statistically significant differences were found in the recovery time, interval to conception, conception rate at first AI, and pregnancy rates by Days 70 and 100 after treatment among the three groups.

CONCLUSIONS

Simultaneous treatment of ovarian cysts with hCG or GnRH and cloprostenol appeared to have no advantage over the conventional method, GnRH alone, in dairy cows. Furthermore, hCG and GnRH have an equal therapeutic effect in cows with ovarian cysts.

Hydrometra is characterized by the accumulation of fluid within the uterus due to the persistence of corpus luteum. The diagnosis of this disorder occurs with an ultrasonic exam. This study evaluated uterine drainage and fertility rates in goats after the use of d-cloprostenol in association or not with Gonadotropin-releasing hormone (GnRH) treatment. Twenty Saanen goats, diagnosed with hydrometra, received three 37.5-μg doses of d-cloprostenol laterovulvarly at 10-day intervals. On D5, the goats were assigned into two groups receiving 1 mL of GnRH or saline solution intramuscularly. Ultrasonography (US) was performed from D0 to D25. An US approach was used to rank hydrometra in scores. The pregnancy rate was assessed 45 and 90 days after the end of treatment. The uterine fluid was totally drained after the first and second administration of d-cloprostenol in 50% and 95% of the goats, respectively. In one female, full emptying of the uterus occurred only after D20. US performed at 45 and 90 days after the end of treatment indicated there was a pregnancy rate of 45.0% and 55.0%, respectively. Fertility did not differ between the GnRH-treated and control goats. Those goats not pregnant at 45 days had a follicular cyst, hydrosalpinx or hydrometra. At 90 days, no change was observed in the hydrosalpinx, and four goats had hydrometra. The use of three doses of d-cloprostenol 10 days apart was efficient for induction of draining the contents of the uterus, resulting in a relatively acceptable pregnancy rate. This treatment associated with the US approach can be important when applied in the field.

This study examined the use of PGF(2α) and estradiol benzoate (EB) either with or without GnRH to synchronize estrus in dairy cows for timed artificial insemination (TAI) under field conditions. First, Holstein dairy cows with a corpus luteum (CL) received 500 μg cloprostenol and were then randomly allocated to three groups: no further treatment (control, n=236); treatment with 1 mg EB 56 h after cloprostenol (EB group, n=339); or treatment with 1 mg EB 56 h after cloprostenol followed by treatment with 100 μg gonadorelin 24 h later (EB + GnRH group, n=216). All cows received TAI 80 h after the cloprostenol injection. In a second experiment, Holstein dairy cows with a CL received 500 μg cloprostenol and were then randomly allocated to two groups: treatment with 2 mg EB 36 h later (EB group, n=284) or treatment with 2 mg EB 36 h after cloprostenol followed by 100 μg gonadorelin 24 h later (EB + GnRH group, n=229). All cows received TAI 24 h after the EB injection. Logistic analyses revealed that the odds ratio for the probability of pregnancy when 1 mg EB was administered 56 h following cloprostenol was 1.9 and 2.0 times (P<0.001) higher in the EB (39.5%) and EB + GnRH groups (40.7%), respectively, compared with the control group (25.8%). However, pregnancy rates in cows receiving 2 mg EB 24 h following cloprostenol showed no difference compared with cows treated with EB only (32.4%) or with EB + GnRH (35.8%). These results indicate that a synchronization protocol comprising PGF(2α) and EB could be used for TAI in dairy herds under field conditions.

Dispersed ovulation at the breeding (BS) and anestrus at non-breeding season (NBS) are major impediments to embryo transfer and insemination programmes. The present study aimed to evaluate a hormonal P4/E2-based synchronisation protocol in mares during both the BS and the NBS on ovarian/follicle behaviour. Mares underwent a hormone protocol to synchronise their ovulation during the BS (n = 8) and NBS (n = 10), starting (D0) with the insertion of an intravaginal device containing 1 g of P4 and 7 mg Estradiol Benzoate IM. (EB). On D9, the device was removed and injected with 0.25 mg of cloprostenol sodic IM and 2 mg of EB IM. Follicular behaviour was evaluated using a daily transrectal ultrasound (24/24 h) from D0 until ovulation. When the dominant follicle (DF) measured at least 35 mm, females were injected with 0.25 mg of gonadorelin acetate IM to induce ovulation. The DF on D0 were similar in animals between BS (18.9 ± 8.4 mm) and NBS (23.7 ± 9.2 mm; p = 0.2700). However, in the BS the DF was smaller (14.2 ± 4.7 mm) on D9 than during NBS (22.0 ± 7.1 mm; p = 0.0177). During the BS, the ovulatory follicle is smaller (p = 0.0042) than during NBS, measured at 33.5 ± 4.6 mm and 41.3 ± 2.8 mm, respectively. Ovulation time after P4 removal was similar during BS (173.1 ± 68.8 h) and NBS (192 ± 58.2 h; p = 0.3507). There was no difference towards an ovulation rate during BS (88%) and NBS (60%; p = 0.0978). There was no difference in spontaneous ovulation during BS (43%) and NBS (0%; p = 0.6085). This hormonal protocol would be an effective tool for inducing cyclicity/ovulation in mares during BS and NBS.

Keywords: Cyclicity; Fertility; Horse; Reproduction; Seasonality; Synchronization of ovulation.

The present study evaluated the effect of the type of norgestomet ear implant (new vs. used) on the ovarian follicular response (experiment 1) and pregnancy per artificial insemination (AI) (P/AI; experiment 2) of beef heifers subjected to an estradiol plus progestin timed artificial insemination (TAI) program. In experiment 1, 57 cyclic beef heifers were randomly assigned to one of two groups according to the type (new or previously used for 9 days) of norgestomet ear (NORG) implant. At the time of NORG implant insertion, the heifers were treated with 2 mg of intramuscular estradiol benzoate. Eight days later, the NORG implants were removed, and the heifers received an intramuscular administration of 150 μg of d-cloprostenol, 300 IU of equine chorionic gonadotropin, and 0.5 mg of estradiol cypionate. The heifers had their ovaries scanned every 12 hours from the time of NORG implant removal to 96 hours after verifying the occurrence and timing of ovulation. No difference (P = 0.89) was observed in the ovulation rates between the two treatments (new = 80.0%; 24/30 vs. used = 81.5%; 22/27). However, the heifers treated with a used NORG implant had (P = 0.04) higher proportion (36.4%; 8/22) of early ovulation (between 36 and 48 hours after NORG implant removal) compared with the heifers treated with a new NORG implant (8.3%; 2/24). In experiment 2, at the beginning of the synchronization protocol, 416 beef heifers were randomly assigned into two groups, as described in the experiment 1. Two days after the NORG implant removal, the heifers were reassigned to be inseminated at 48 or 54 hours after NORG implant removal. There was an interaction (P = 0.03) between the type of NORG implant and the timing of TAI on P/AI. The timing of insemination only had an effect (P = 0.02) on the P/AI when the heifers were treated with a used NORG implant [(TAI 54 hours = 41.9% (44/105) vs. TAI 48 hours = 58.6% (58/99)]. In conclusion, beef heifers synchronized with a used NORG implant plus estradiol exhibited a higher proportion of earlier ovulations, and TAI in these heifers should be performed 48 hours after removal of used NORG implants.

Two consecutive experiments were conducted. In Experiment 1, 24 Friesian lactating cows were randomly assigned to two groups. Cows in Group I received intramuscularly (i.m.) 500 mcg of cloprostenol, 1250 IU of human chorionic gonadotropin (hCG) and 5 mg of estradiol benzoate 12 h after cloprostenol treatment. Cows in Group II received 750 IU i.m. of hCG and 3 mg of estradiol benzoate 12 h after cloprostenol treatment. Treatment was given on Day 16 after estrus in both groups. All animals showed estrus within 24 to 48 h after cloprostenol treatment. The average interval from cloprostenol injection to the onset of estrus was not influenced by treatments. Four cows in Group I failed to ovulate and became cystic. In Experiment 2, 71 Friesian lactating cows were randomly assigned to two groups. Cows in Group I received 500 mcg i.m. of cloprostenol after corpus luteum detection by palpation per rectum. Cows in Group II received 500 mcg of cloprostenol plus 750 IU of hCG and 3 mg of estradiol benzoate 12 h after. When estrus ready for service was confirmed by rectal examination, cows were inseminated. The percentage of cows ready for service tended to be lower (P<0.06) between cows in Group I (88%) and those in Group II (100%). The average interval from cloprostenol treatment to service was longest (P<0.001) in Group I (78.7 h+/-14.9, X+/-SD) vs Group II (48 h+/-2.9). The degree of readiness for service synchrony was lowest (P<0.001) in Group I (59.3%) vs Group II (94.2%). The pregnancy rates of cows synchronized or treated were not altered by hCG-estradiol benzoate treatment (P>0.25). These results suggest that in dairy cows treated with cloprostenol following palpation per rectum of a corpus luteum and then with 750 IU of hCG and 3 mg of estradiol benzoate 12 h later, a single fixed-time insemination at 48 h after cloprostenol treatment should be performed.

Outcomes of short- (6.5 days) and long-term (14.5 days) estrous synchronization for 6.5 d (G-6.5d) or 14.5 d (G-14.5d) and followed by the 4-day or 3-day declining-dose follicle-stimulating hormone superovulatory regimen, respectively, were compared using 16 estrous-cycling Santa Inês ewes. Non-surgical embryo recovery (NSER) procedures were performed 60 d apart starting 6 or 7 d after the onset of estrus; an i.m. injection of estradiol benzoate and of d-cloprostenol at 16 h was followed by an i.v. oxytocin injection administered 20 min before NSER. There was a longer (P < 0.05) period before estrous onset in ewes during the second (September) compared with the first study replicate (July) by approximately 14 h. The NSER could be performed in 11 of 15 ewes that were in estrus, with an average of three viable-embryos/donor and the mean duration of the procedure being 29 min. There were no differences in superovulatory responses between the two groups of ewes, but there were only degenerated embryos in ewes of the G-6.5d group. In summary: i. the duration of progestin-priming and of multiple-dose pFSH treatment had a limited effect on superovulatory responses in estrous-cycling Santa Inês ewes; ii. NSER is a safe and repeatable method of embryo collection in ewes subsequent to superovulation; and iii. duration of the superovulatory treatment regimen may alter the effects of endogenous steroids on oocyte/embryo quality in ewes.

The aim of this study was to compare morphological and functional features of spontaneous and induced corpora lutea (CLs) in goats. Fourteen adult and cycling Anglo Nubian goats (Argentina) were randomly allocated to two groups: Group N (n=7) included goats with natural spontaneous oestrus and Group PG (n=7) included does in which oestrus was synchronized by the administration of two i.m. cloprostenol doses, 10 days apart. In both groups, oestrous behaviour was checked twice daily (Day of oestrus=Day 0) and daily transrectal ultrasonographies were performed for evaluating CLs and follicles dynamics through the complete subsequent oestrous cycle; the luteal activity was determined directly, in terms of progesterone (P4) secretion, and indirectly, by assessing effects of CL on follicular dynamics. All goats exhibited oestrous behaviour and ovulation without differences in ovulation rate (N: 1.67+/-0.2, PG: 2.0+/-0.1). The total luteal tissue area showed linear growth from Day 4 to Day 15 of oestrous cycle in all goats, but the developmental dynamics differed between groups, treated goats had larger area (P<0.01). Plasma P4 concentrations also increased from Day 0 to Day 15 in all the does; however, from Day 5 to Day 15, treated does had a lower concentrations than the untreated group (P<0.001). There were differences in the development of follicular waves between groups; assessment of size-distribution showed that treated group had a higher number of small and larger follicles (P<0.05). The largest follicles recorded in treated goats had a higher maximum diameter both at the first (PG: 7.6+/-0.8mm; N: 4.9+/-0.7 mm, P<0.05) and second follicular waves (PG: 6.3+/-1.4mm; N: 5.0+/-0.4mm, P<0.05) and a longer growth phase during the second wave (PG: 6.5+/-1.7 days; N: 4.6+/-0.7 days, P<0.05), coincident with the period of maximal luteal secretion. In conclusion, synchronization of oestrus and ovulation by the administration of a prostaglandin analogue causes differences in developmental dynamics and functionality of induced corpora lutea when compared to natural spontaneous ovulation.

Two intact and 2 ovariectomized mares aged 3-16 years had bipolar electrodes implanted in the myometrium to measure electromyographic (emg) activity during normal and exogenously simulated (with oestrogen and progesterone) cyclical activity (anoestrus, transition, oestrus and dioestrus). Oxytocin, cloprostenol, propantheline bromide and clenbuterol were administered during each cycle stage. In 1 mare, emg activity was recorded during natural breeding (4 times) and through the first 20 days of pregnancy. Simultaneous intrauterine pressure recordings (IUP) using an open tipped catheter system were taken occasionally. For mares in oestrus, we recorded short bursts of high amplitude emg activity separated by quiet periods, a pattern that is indicative of uterine contractions. During dioestrus the duration of emg activity increased, but amplitude decreased and interspersed quiet periods were less well defined, indicative of uterine tonus. The emg patterns seen in anoestrus and transition were intermediate. At breeding there was a short-lived increase in emg activity, unlikely to be caused by endogenous hormone release. During early pregnancy the emg characteristics varied depending on whether the fertilized ovum was in the oviduct, migratory or fixed, with emg activity increasing to 100% after Day 16 when uterine tone is maximal. Oxytocin and cloprostenol caused prolonged emg activity followed initially by a short burst pattern that was most pronounced in oestrus and least in dioestrus and suggests uterine motility is stimulated to a greater extent during oestrus. Propantheline decreased emg activity, whereas cloprostenol caused minimal changes. IUP increased with uterine stimulants and decreased with uterine relaxants, but showed little variation between cyclic states. There was little correlation, statistically or visually, between IUP and emg activity during the oestrous cycle with or without drug treatment. Because emg analysis gave consistent results and demonstrated significant differences between oestrus and dioestrus that neither agreed nor correlated with IUP, the validity of the IUP recording technique used in this study (as well as those used in general for the mare) is questioned. It is suggested that extrauterine factors such as intestinal motility and intra-abdominal pressure changes could influence IUP responses.

The efficacy of eight combinations of fluorogestone acetate (FGA, 20 or 40 mg as intravaginal device during 11 days), equine chorionic gonadotropin (eCG, 300 or 500 UI injected 48 hr before FGA removal) and prostaglandin F_2α (cloprostenol, 0 or 50 μg injected 48 hr before FGA removal) aiming at induction and synchronization of oestrus and ovulation was evaluated during the anoestrus season in spring and during the breeding season in autumn in adult Beni Arouss goats. Oestrous behaviour was recorded between 12 and 60 hr after FGA removal. Blood samplings allowing to assess onset of the pre-ovulatory LH surge and increase of progesterone as sign of an active corpus luteum were performed, respectively, between 20 and 60 hr and 3, 5, 8 and 15 days after FGA removal. No season-related differences (spring vs. autumn) were observed for oestrous response (95% vs. 93%), pre-ovulatory LH surge (94% vs. 84%) and luteal response after 3-8 and 11-15 days post-treatment (respectively 92% vs. 66% and 92% vs. 98%). The onset of oestrus (21 [13-53] vs. 32 [12-54] hr) and LH surge (26 [20-60] vs. 38 [22-60] hr) occurred significantly later in autumn. FGA (40 vs. 20 mg) in autumn significantly delayed the onset of oestrus (36 [16-54] vs. 23 [12-47] hr) and LH surge (44 [26-58] vs. 33 [22-60] hr). Significant treatment-related differences were recorded for onset of LH surge (earliest for 20 mg FGA, 300 IU eCG, 50 μg PGF_2α ) and onset of luteal phase (latest for 40 mg FGA, 300 IU eCG, 50 μg PGF_2α ). In conclusion, the hormone combinations tested appeared equally effective in terms of oestrous and ovulation rates. Season has influenced significantly the onset of oestrus and LH surge, and the high dose regimen of FGA delayed the ovarian response in autumn.

The 5alpha-reduced androgens have been implicated as antagonists of follicular development. In this experiment, we examined the effect of active immunization against 5alpha-reduced androgen on follicular development in ewes. During the breeding season, cyclic Merino ewes were either actively immunized three times against 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) or served as controls. Six to nine weeks after the last immunization, they were treated with PGF(2alpha) analog (PG, 125mg cloprostenol i.m.) and luteolysis was induced. Fourteen days after the PG treatment, the ewes were either killed (mid-luteal phase) or treated a second time with PG and killed 24h later (early follicular phase). At slaughter, blood samples were collected and ovaries recovered. All CL and follicles larger than 2mm were dissected and their size and appearance were recorded. Follicular fluid was collected and concentrations of estradiol-17beta (E(2)), progesterone (P), androstenedione (A(4)), testosterone (T), dihydrotestosterone (DHT), 5alpha-androstane-3alpha-ol,17beta-one (androsterone: 3alpha-ol) and 3alpha-diol were determined by RIA. Immunization induced antibodies primarily to DHT and its 5alpha-reduced substrates 3alpha-diol and 3alpha-ol but not to E(2), P, A(4) or T. Immunization increased ovulation rate, size of ovulatory follicles and weight of CL. Immunization appeared to increase ovulation rate by decreasing the incidence of atresia in large preovulatory follicles. Regardless of their physiological status follicles contained only low levels of DHT; 3alpha-ol and 3alpha-diol were not detected in most follicles. Immunization did not appear to affect levels of DHT or other steroids in the follicular fluid. In conclusion, the induction of antibodies to 5alpha-reduced androgens increases ovulation rate by enhancing follicular viability during the preovulatory period in ewes. However, this effect is not brought about by the direct immune-neutralization of DHT or its 5alpha-reduced substrates 3alpha-ol and 3alpha-diol at the ovarian level.