This study investigated the effect of altrenogest treatment on the farrowing development of sows, and birth weight (BW) and piglet survival until the third day of life. Three control groups were used: (i) sows that farrowed spontaneously before 114 day of gestation (CONT <114); (ii) sows that spontaneously farrowed at ≥114 day of gestation (CONT ≥114); (iii) sows that farrowed at ≥114 day with cloprostenol treatment (CONTCLOPR). Other sows were treated with altrenogest (Regumate(®) ) for 3 days (days 111, 112 and 113 of gestation): one group gave birth spontaneously (ALT) and the other group received altrenogest until day 113 and cloprostenol on day 114 (ALTCLOPR). There were no differences (p>> 0.05) in farrowing duration, BW, coefficient of variation (CV) of BW, stillborn piglets, mummified foetuses, percentage of light piglets and survival until Day 3 between sows with and without cloprostenol treatment, in both control (CONT ≥114 vs CONTCLOPR) and altrenogest-treated sows (ALT vs ALTCLOPR). Further comparisons were performed taking into account three groups: sows with early delivery (CONT <114 - farrowing before 114 days of gestation; n = 56), sows with longer gestation (CONT ≥114 - with and without cloprostenol treatment sows; n = 103) and ALT sows (with and without cloprostenol treatment; n = 105). Gestation length of CONT ≥114 and ALT sows was similar (p>> 0.05), but higher than in CONT <114 sows. There were no differences (p>> 0.05) between groups in farrowing duration, CV of BW, and percentages of stillborn piglets and mummified foetuses. Sows of CONT <114 group had a larger litter size and a lower BW than sows of the other two groups (p < 0.05). Sows of CONT <114 group had a higher percentage of lighter piglets and a lower piglet survival rate (p < 0.05) than ALT sows. In conclusion, altrenogest treatment proved to be an efficient method to avoid early parturition in 3-5 parity sows resulting in heavier piglets at birth.

Forty-two cycling, multiparous beef cows (percentage-Brahman) were given two injections of 500 ug Cloprostenol (CLP) 11 days apart. Cows were randomly allocated to be ovariectomized at 0, 12, 24, 36, 48, 60 or 72 hr after the second CLP injection. Mean CL weight declined within 36 hr after CLP. Mean concentration of P4 in luteal tissue increased between o and 60 hr, while mean P4 content per CL declined by 12 hr after CLP. There was a precipitous decrease in mean serum P4 by 12 hr following CLP injection. Serum E2 was elevated until 24 hr and then declined through 72 hr after CLP. Follicular T concentration increased from 0 to 48 hr and then decreased by 60 hr. We conclude that CLP caused rapid diminution of luteal function which was accompanied by a reduction in P4 content but not in P4 concentration. Futhermore, the concentration of E2 in large follicles decreased by 72 hr post-CLP which is consistent with an alteration of the steroidogenic pathway in the periovulatory follicle.

The contractile effects of PGF2alpha and its cloprostenol analogs (D-enantiomer and racemate) were examined on isolated smooth muscle preparations (uterine, tracheal, ileal and arterial) from rat, guinea-pig and horse. DL- and D-cloprostenol were potent contractors of myometrium, but had negligible secondary effects on other types of smooth muscle, except artery whose response to the D-enantiomer may give rise to some concern.

49 of 102 sheep of one production herd, which had returned to oestrus once or twice within the 1985 breeding season, were treated twice in a nine-day interval with the PGF2 alpha analogue Cloprostenol "Jenapharm". 53 animals received an additional dose of 10 micrograms of Gonavet "Berlin-Chemie". A lambing rate of merely 15% was achieved by subsequent term-oriented artificial insemination. 31 sheep still in oestrus one day after term-oriented artificial insemination were served, bringing the lambing rate from synchronisation of oestrus and ovulation to 26% and the lambing result to 154%. Serving of the remaining sheep in 2 subsequent oestric cycles, on balance, yielded lambing rates and results of the remaining sheep in 2 subsequent oestric cycles, on balance, yielded lambing rates and results which were higher with significance than those recorded from untreated sheep in the same herd.

The objective of the present study was to evaluate the effect of different hormonal stimulation treatments on the antral follicular population of naturalized Canindé goats. Adult goats (n=17) having estrous cycles at regular intervals were treated with intra-vaginal sponges containing 60 mg medroxyprogesterone acetate for 11 days, combined with an application of 50 μg d-cloprostenol on the Day 8 of treatment. For ovarian stimulation, goats were distributed into the following experimental groups: (a) multiple doses (MD), with a total of 120 mg NIH-FSH P1 in five intramuscular injections (30/30; 20/20 and 20 mg) at 12-h intervals; (b) three doses (TD), with a total of 120 mg NIH-FSH P1 in three intramuscular injections (60; 40 and 20 mg) at 24 h intervals; (c) one dose (OD), which consisted of the use of 70 mg NIH-FSH P1 combined with 200 IU eCG administered intramuscularly 36 h before sponge removal. In the MD and TD groups, FSH injections were begun on the Day 8 of progestagen treatment. The ovaries of all animals were observed by transrectal real time ultrasonography (TRU) during the follicular stimulation protocols. All follicles ≥2 mm were counted, measured and classified according to greatest diameter. The ultrasonographic assessment of the ovaries provided for well-defined ovarian structures. At the time of insertion of the sponges (Day 0), significant differences were observed (P<0.05) for the mean number of large follicles between the treated groups. Meanwhile, on Day 11, the three treatments did not differ (P<0.05), regardless of the follicular category. The diameter of small follicles was similar in MD, TD and OD during the whole period of the study. In the TD group, diameter of the large follicles was less (P<0.05) on Day 10 when compared to MD and OD. However, these differences were not observed on Day 11. In conclusion, the three treatments produced comparable distribution of the follicular populations. However, the single dose treatment can be preferred because of its simplicity and efficacious follicular response.

This study compared the effects of intravaginal and intravenous routes of oxytocin (OT) administration in 46 oestrous-induced Santa Inês ewes (6-day treatment with progestin-releasing intravaginal sponges and a single injection of 200 IU of eCG at the time of sponge removal) that underwent transcervical embryo recovery 6-7 days after oestrous onset and mating. All ewes received 37.5 μg of d-cloprostenol via latero-vulvar route, and 1 mg of oestradiol benzoate i.m. 16 hr before and 50 IU of OT 20 min before non-surgical embryo recovery (NSER), with OT being administered intravenously (n = 21) or intravaginally (n = 21). An overall oestrous response was 95.6% (44/46), and adequate cervical retraction could be accomplished in 78.6% (33/42) of ewes. The percentage of successful NSER procedures was 57% (24/42) or 72.7% (24/33) of animals with sufficient cervical retraction. The duration of NSER procedure averaged 28 min (range: 17-40 min) and ~96% of flushing fluid could be recovered (range: 85%-100%). Out of 18 ewes that could not undergo NSER, 12 (66.6%) presented various anatomical barriers, whilst the other 33.4% did not present these barriers and still could not be traversed. Excluding the ewes with those anatomical features, the overall success rate of NSER was 80% (24/30). The route of OT administration had no effect on NSER efficiency or the ease with which transcervical embryo flushing was performed. Both routes of OT administration can be used for cervical dilation protocol. Discarding ewes with anatomical features precluding cervical penetration is highly recommended to increase the efficacy of NSER in sheep.

OBJECTIVE

The aim of this study was to evaluate the efficacy of three different treatment protocols for estrus induction and conception rate in postpartum anestrus buffaloes during breeding season under field conditions.

METHODS

The 47 postpartum anestrus buffaloes of the 2nd to 6th parity were divided into three groups. Group 1 (n=16): Buffaloes received cosynch treatment, that is, buserelin acetate 10 µg on day 0 and 9, cloprostenol 500 µg on day 7 followed by fixed-time artificial insemination (FTAI) at the time of second buserelin acetate and 24 h later. Group 2 (n=15): Buffaloes received norgestomet ear implant subcutaneously for 9 days, estradiol benzoate 2 mg on the day of implant insertion (day 0), pregnant mare serum gonadotropin (PMSG) 400 IU and cloprostenol 500 µg on day 9 followed by AI at 48 and 72 h after implant removal. Group 3 (Cosynch-plus, n=16): Buffaloes received Cosynch protocol as per Group 1 except an additional injection of PMSG 400 IU (i.m.) was given 3 days before the start of protocol and FTAI done at the same time of Group 1. Pregnancy diagnosis was performed after 45 days of AI.

RESULTS

The estrus induction response following the treatment was 81.3%, 100%, and 93.7% in Group 1, 2, and 3, respectively. The buffaloes of Group 1, 2, and 3 expressed intense (38.4%, 60% and 46.6%, respectively) and moderate estrus (46.1%, 26.6%, and 40%, respectively). The conception rates in Group 1, 2, and 3, at FTAI and overall including subsequent estrus were 37.5% and 62.5%, 53.3%, and 66.6%, 56.3%, and 75%, respectively.

CONCLUSIONS

All the three treatment protocols can be effectively used for induction of estrus with acceptable conception rate in postpartum anestrus buffaloes during breeding season under field conditions. However, Cosynch-plus (similar to Cosynch protocol except addition of PMSG, 400 IU 3 days before the start of first buserelin acetate administration) protocol results comparatively better pregnancy rate.

This study assessed the efficiency of cervical relaxation protocol using none, half or full dose (1.0 mg) of estradiol benzoate in Dorper ewes subjected to non-surgical embryo recovery (NSER). Thirty-six pluriparous ewes received progestogen sponge (60 mg) for nine days plus eCG administration (300 IU i.m.) 24 h before sponge removal. Ewes were not mated and were randomly assigned to receive at 16 h before NSER 37.5 µg d-cloprostenol i.m. and different doses of estradiol benzoate: 0.0 mg (0EB group; n=12); 0.5 mg (0.5EB group; n=12) or 1.0 mg of estradiol (1.0EB group, n=12). All ewes received oxytocin (50 IU) i.v. 20 min before NSER, which was performed eight days after sponge removal. Corpora lutea were counted by transrectal ultrasonography 24 h before NSER. After procedure, the ewes were kept in natural breeding period to check their post-NSER fertility. NSER was performed in 91.7% (33/36) of the animals with overall fluid recovery efficiency over 97% (P>0.05). The cervical transposing with Hegar dilator was longer (P<0.05) in 0EB (4.2±0.3 min) compared to 0.5EB (1.7±0.3 min) and 1.0EB group (1.5±0.3 min). The cervical transposing with mandrel/catheter was longer (P<0.05) in 0EB (2.4±0.5 min) than 1.0EB group (1.3±0.5 min). Overall duration of uterine flushing was 25.4 min with structure recovery rate of 43.5%, with no difference among groups (P>0.05). The post-NSER fertility was higher (P<0.05) in 0.0EB (90%) than 0.5EB group (36.4%). In conclusion, NSER can be successfully performed in Dorper ewes by using a cervical relaxation protocol without estradiol benzoate.

This study examined the feasibility of transcervical embryo recovery after the hormonal treatment to induce cervical dilation, following the 7-day oestrous synchronization protocol in multiparous Santa Inês ewes. A total of 23 cyclic ewes received two doses of 37.5 μg of d-cloprostenol by latero-vulvar route 7 days apart. After the second injection of d-cloprostenol, the ewes were checked for oestrus (every 12 hr) and then mated by fertile rams throughout the oestrous period. All ewes received 37.5 μg of d-cloprostenol (latero-vulvar) and 1 mg of oestradiol benzoate by either intramuscular (EBim group; n = 12) or intravaginal (EBivg group; n = 11) route 16 hr before embryo flushing. Twenty minutes before the flushing, 50 IU of oxytocin were administered intravenously. The oestrous response (i.e., the percentage of ewes that showed signs of oestrous behaviour after the second d-cloprostenol injection) was 91.3% (21/23). The proportion of successfully penetrated ewes (81.8% compared with 80.0%), the mean duration of embryo flushing (24.7 ± 2.0 min compared 26.2 ± 1.9 min), the flushing fluid recovery rate (94.8 ± 1.3% compared with 91.0 ± 2.9%) and the average number of structures recovered per ewe (0.5 ± 0.4 compared with 0.8 ± 0.4) did not vary (p>> 0.05) between the EBim and EBivg groups. Viable embryos were recovered from 41.2% (7/17) of successfully penetrated ewes. It can be concluded that nonsurgical (i.e., transcervical) embryo collection can be performed in oestrous-synchronized Santa Inês ewes pretreated with d-cloprostenol, oxytocin and oestradiol benzoate, with the latter hormone administered by either the intramuscular or intravaginal route.

The effects of estradiol esters, d-cloprostenol and oxytocin on induction of cervical dilation prior to non-surgical embryo recovery in Santa Inês ewes (Days 6-7 estrous cycle) were assessed in this study. In Trial 1, transcervical embryo flushing was performed in estrous-induced ewes administered 37.5 μg of d-cloprostenol i.m. 10 h before and 50 IU of oxytocin i.v. 20 min before uterine flushing with (EB-PGF-OT; n = 13) or without (PGF-OT; n = 11) 1 mg of estradiol benzoate i.m. administered concurrently with d-cloprostenol injection. In Trial 2, the estrous-synchronized animals were treated with 1 mg of estradiol benzoate (EB-PGF-OT; n = 12) or estradiol cypionate (EC-PGF-OT; n = 12) i.m. along with 37.5 μg of d-cloprostenol i.m. 16 h before and 50 IU of oxytocin i.v. 20 min before uterine flushing. In Trial 1, uterine flushing could be accomplished in 38% of ewes in the EB-PGF-OT and 27% those in the PGF-OT (P>0.05) group. Flushing fluid recovery averaged 90% and there were 1.0 ± 1.1 embryos/ewe collected with mean duration of the flushing procedure being ˜36 min. In Trial 2, uterine flushing was accomplished in 78% of ewes in the EB-PGF-OT and 44% of those in the EC-PGF-OT group (P>0.05) with mean flushing fluid recovery rate being 88% and time elapsing to complete flushing being ˜33 min. Within the subsets of animals treated with EB, the percentages of successful transcervical penetrations were 38% compared with 78% in Trials 1 and 2, respectively (i.e., with EB administered 10 h compared with 16 h before uterine flushing: P<0.05). The interval from EB administration to the beginning of transcervical penetration can affect the efficacy of embryo recovery procedures utilizing a combined EB/d-cloprostenol/oxytocin pre-treatment.

The present ultrasonographic study examined the relationship between certain follicular parameters and the superovulatory response in gonadotropin-stimulated heifers. Thirty heifers received a total of 35 mg FSH twice daily for 4 d and 0.75 mg <em>cloprostenol</em> were given to induce luteolysis and estrus at 72 h after the initial FSH injection. Transrectal ultrasonography was performed once daily from 1 or 2 d before the initial FSH injection and until the day of estrus. The number of small (2 to 4 mm), medium (5 to 9 mm), and large >>/=10 mm) size follicles as well as the diameter of the large follicles were recorded. Embryos were recovered non-surgically 6 or 7 d after estrus, and the number of corpora lutea was determined by palpation per rectum. Heifers with >2 or </=2 corpora lutea were classified as responders or nonresponders, respectively. All follicular categories were affected by treatment with FSH in the responders (P<0.0001), while in the nonresponders only small follicles and the total number of follicles showed a change after treatment (P<0.05). All follicular categories were different between the 2 groups (P<0.005). There was no effect of corpus luteum location (ipsilateral vs contralateral) on any of the follicular categories (P>0.05). The number of large follicles and the sum of medium and large follicles were positively correlated (r=0.43 and r=0.54, respectively; P<0.05) with the number of corpora lutea palpated on the day of embryo recovery (6 to 7 d after estrus). In conclusion, there was an effect of the day relative to initiation of FSH treatment on all follicular categories in heifers responding positively to superovulation, and there was no effect of side (left or right ovary) or of corpus luteum diameter (ipsilateral or contralateral).

The objective was to examine growth of the ovulatory follicle after FSH (Folltropin-V; Bioniche Animal Health, Belleville, Ontario, Canada) was given at the onset of induced luteolysis during a synchronization of ovulation protocol. Using GnRH or hCG for inducing ovulation enabled assessing ovulatory follicle responsiveness to an endogenous versus exogenous surge of LH activity. At 8 to 10 days after estrus (synchronized estrus = Day 0), lactating dairy cows received an Eazi-Breed CIDR (Pfizer Animal Health) plus 100 μg GnRH. After 7 days, controlled internal drug release devices (CIDRs) were removed, cows were given 500 μg cloprostenol, and then randomly allocated to receive 80 mg Folltropin-V (FSH; N = 19) or 4 mL sterile saline (SAL; N = 16). After 49 hours, FSH and SAL cows were randomly allocated to receive 100 μg GnRH or 3000 IU hCG. Five cows ovulated 30 to 42 hours (38.4 ± 1.2 hours) after FSH treatment. In the remaining FSH (N = 14) or SAL (N = 16) cows, ovulatory follicle size was similar at CIDR removal (14.5 ± 0.6 and 14.7 ± 0.6 mm, respectively; P = 0.85) and when GnRH/hCG was given (16.6 ± 0.6 and 17.7 ± 0.6 mm, respectively; P = 0.23). Estradiol-17β concentrations were lower in FSH cows at 36 and 49 hours after CIDR removal (FSH by time interaction, P < 0.005). After GnRH or hCG treatment, four FSH cows failed to ovulate. In cows exhibiting ovulation, the last recorded size of the ovulatory follicle was not influenced by FSH (18.1 ± 0.9 and 17.5 ± 0.6 mm for FSH and SAL, respectively; P = 0.59) or hormonal induction approach (18.4 ± 0.9 and 17.2 ± 0.7 mm for GnRH and hCG, respectively; P = 0.29). The interval from onset of luteolysis to ovulation and pharmaceutical induction to ovulation was shorter in FSH cows given GnRH (FSH by pharmaceutical inducer [GnRH vs. hCG] interaction; P = 0.01). Cows receiving GnRH had an LH surge; hCG-treated cows did not. Maximum LH concentrations were greater (P < 0.04) in SAL versus FSH cows after GnRH treatment (10.9 ± 1.2 vs. 6.7 ± 1.4 ng/mL, respectively). In three FSH cows failing to ovulate after GnRH treatment, the maximum LH concentration was <4 ng/mL. When analyzed from GnRH treatment, average time to LH maximum concentration was similar (P = 0.50) to values obtained in cows receiving FSH and GnRH and SAL and GnRH (1.7 ± 0.2 vs. 1.9 ± 0.1 hours, respectively). Interval to maximum hCG concentrations was shorter (P = 0.02) for cows receiving SAL versus FSH (8.0 ± 0.8 and 10.0 ± 0.8 hours for SAL and FSH, respectively). Ovulatory dysfunction of this magnitude highlighted the lack of suitability of Folltropin-V at a dose of 80 mg at the time of induction of luteolysis in fixed timed AI protocols.

This study was conducted to evaluate effects of two administrations of d-cloprostenol at different intervals to synchronize the time of estrus and ovulation among estrous cyclic goats. In Experiment 1, 32 does were treated with 30 μg d-cloprostenol at 7.5 (T7.5, n = 16) or 11.5-day (T11.5, n = 16) intervals. In Experiment 2, the same treatments were administered and there was AI of the does (T7.5, n = 40 and T11.5, n = 38). In Experiment 1, ultrasonic assessments of ovaries were conducted at the time of the second administration of d-cloprostenol, every 12 h until detection of ovulation, and 7 days after estrous onset to detect the corpora lutea, as well as for pregnancy diagnosis 40 days after AI. In Experiment 1, the estrous response (90.6%, 29/32) was similar (P > 0.05) in both groups. Diameter of the largest follicle at the time of administration of the second dose was larger (P = 0.01) in the T7.5 than T11.5 group (7.0 compared with 5.7 mm), while the values for ovarian variables were similar (P > 0.05). In Experiment 2, the greatest (P < 0.001) synchrony in timing of initiation of estrus in does (T7.5 = 83.3% and T11.5 = 50.0%) occurred after the second day (36-48 h). The pregnancy rate tended (P = 0.0836) to be greater for does in the T7.5 (71.4%, 40/56) than T11.5 (55.6%, 30/54) group. With use of both protocols, there were acceptable estrous synchronization and pregnancy rates in estrous cyclic dairy goats.

The present study aims to evaluate the effect of administering prostaglandin (250 μg cloprostenol) and oxytocin (10 UI) or a GnRH agonist (4.2 μg buserelin acetate) on rams' physiological responses to electroejaculation and the ejaculate's characteristics. The study was performed with a 2 × 2 factorial arrangement, according to whether it used oxytocin and prostaglandin (OXPGF) or GnRH. Therefore, there were four treatments: GControl = saline; GOXPGF = administration of PGF2α and oxytocin; GGnRH = administration of GnRH; administration of GOXPGF + GnRH = GnRH and PGF2α + oxytocin. An interaction between the hormonal treatments in the heart rate occurred: while the heart rate decreased when using OXPGF alone (control: 113.7 bpm vs. GOXPGF: 103.5 bpm, pooled SEM; P = 0.02), it did not modify when applying both treatments simultaneously and administering GnRH (GGnRH: 109.1 bpm vs. GOXPGF + GnRH: 111.5 bpm respectively, pooled SEM = 4.5). The respiratory rate also decreased with the administration of OXPGF (38.7 vs. 46.3 with and without OXPGF, pooled SEM = 10.0, P = 0.003). Administering OXPGF also tended to decrease the temperature (38.77 °C vs. 38.94 °C, with and without OXPGF, respectively, pooled SEM = 0.06; P = 0.056). Blood glucose increased with the administration of OXPGF from 58.7 mg/dL to 62.4 mg/dL (pooled SEM = 1.3, P = 0.014) and varied with time. CK concentrations increased from 641.8 mg/dL to 881.7 mg/dL (pooled SEM = 50.6) with the administration of OXPGF. GnRH administration decreased cortisol concentration from 7.3 ng/mL to 2.1 ng/mL (pooled SEM = 1.4; P = 0.04). The treatments had no effects on the time required for EE, the pulse at which the animals began and ended the ejaculation, or the vocalizations emitted during EE. There were no effects in any evaluated sperm variable. The research concluded that the administration of oxytocin and analogs of PGF2alpha decreased the stress response to electroejaculation, as well as administering GnRH agonist was slightly effective as it only decreased cortisol concentration. Also, these treatments, either alone or combined, did not affect the characteristics of the ejaculate collected.

Keywords: Glucocorticoids; Pain; Semen; Sheep; Welfare.

In autumn calving dairy herds, treatment of cattle not observed in estrus prior to the breeding season is common. Routinely, a single prostaglandin or a modified Ovsynch (MOFT) protocol are used-without evidence of their relative effectiveness. This study compares the effects on conception, associated timing, and profitability of administering cows with prostaglandin or MOFT treatment. A hundred and ninety-two Holstein-Friesian cows from three herds without an observed estrus within 28-days before mating start date were randomly treated with d-cloprostenol (PGOD) or an 8-day MOFT protocol. The association of treatment and calving-breeding start-date interval (CBSI) on the risk of conception were investigated. Partial budget, sensitivity analysis, and Monte Carlo simulation was used to assess economic performance, identify critical input variables, and explore the effects of input uncertainties on model output. There was a significant association between MOFT treatment and conception during 21 and 84 days after mating start date, compared to PGOD. MOFT treatment was associated with a mean net benefit of £58.21 (sd £19.42) and £27.29 (sd £17.75) per cow for herds with a fixed or variable dry-off date, respectively. The relative profitability of an MOFT protocol is dependent on its effects on barren rate and herd dry-off strategy.

Keywords: Ovsynch; cattle; dairy; partial budget; progesterone; prostaglandin; reproduction.

The objective of this study was to establish and characterize the relationship between the dose of cloprostenol (37.5, 250, 500 and 750 μg) and the age of the early corpus luteum (CL) (80, 88, 96, 104 and 112 h) on the luteolytic response of mares. Behavioural oestrus and ultrasonographic signs of return to oestrus were considered as the occurrence of full luteolysis. A total of 298 mares were divided into groups according to dose of cloprostenol and CL age. There was an effect of dose of cloprostenol (p < 0.001) and age of the CL at the time of treatment (p < 0.001) on the percentage of mares with full luteolysis. The efficacy of 37.5 μg of d-cloprostenol was similar to that of 250 μg of d,l-cloprostenol (p>> 0.05); and that of 500 similar to that of 750 μg (p>> 0.05). The higher dose groups (500 and 750 μg) induced full luteolysis more frequently than the lower dose groups (37.5 and 250 μg) 96-104 h post-ovulation. There was no effect of CL age or cloprostenol dose on the interovulatory interval (p>> 0.05). In conclusion, the effect of cloprostenol on the percentage of mares undergoing full luteolysis is dose-dependent. However, this effect is only evident in mares with CLs aged between 96 and 104 h. There is no advantage of administering more than 500 μg of d,l-cloprostenol (Estrumate(®)), to obtain a higher percentage of mares with full luteolysis in mares with CLs aged 80-112 h.

Fifteen parturient camels given chlortetracycline (CTC) as intrauterine pessaries (3 g/head) were divided into the control group (n = 5), which remained untreated, oxytocin-treated group (50 IU, intramuscular; n = 5), and cloprostenol-treated group (Estrumate, 500 μg, intramuscular; n = 5). Serum samples were collected at 0, 1, 2, 4, 8, 24, 48, and 72 hours after treatment and CTC was determined. The CTC appeared in blood within 1 hour. The maximum concentration of CTC was detected in blood after 72 (543.58 ± 117.85 μg/L), 8 (520.48 ± 13.65 μg/L), and 1 hour (831.98 ± 111.01 μg/L) of administration in control, oxytocin-, and PGF2α-treated camels, respectively. There was a high significant effect of time (P < 0.001) and treatment-by-time interaction (P < 0.001) on serum CTC concentration. In the control group, there was a significant (P < 0.05) increase in CTC concentrations at 72 hours compared to the other times. In the oxytocin group, there was a significant (P < 0.05) decrease in CTC concentrations at 24, 48, and 72 hours compared to its level after 1 or 8 hours. In PGF2α, there was a significant (P < 0.001) decrease in CTC concentrations at 2, 4, 8, 24, 48, and 72 hours compared to its level after 1 hour. Treatment contrast at different time points showed a significant (P < 0.001) increase in CTC concentration after 1 hour in the PGF2α-treated group compared to oxytocin and control groups. By 72 hours, CTC concentrations were significantly (P < 0.05) lower in PGF2α and oxytocin groups than in the control group. In conclusion, serum CTC concentration in dromedary camels increases within 1 hour after intrauterine administration and remains elevated for at least 72 hours in control, oxytocin-, and PGF2α-treated animals.

The estimation of melatonin in bovine plasma by radioimmunoassay is described and some aspects of specificity are discussed. Mean values for individual heifers ranged from 0.025 to 0.25 nmol/l during the day and were significantly (P less than 0.01) raised in each animal to mean values of 0.19 to 1.41 nmol/l at night. The hormonal changes after cloprostenol injections were not affected by the time of day at which the heifers were treated.

For 6 months, 10 adult Saanen crossbred goats were fed undernutrition diet (70% maintenance), and finally five goats were refed for 6 weeks with 150% maintenance. In all animals oestrus was synchronized using 45 mg FGA vaginal sponge for 11 days, 300 IU eCG and 50 microg cloprostenol 48 h prior to sponge removal. From oestrus onset, during a 24-h period, blood samples were collected for oestradiol and NEFA assay. Ovulation was verified by laparoscopy 3 days after sponge removal. Body mass loss was 18.62 +/- 3.03% of initial weight and in refed goats body weight recovery was 90.63 +/- 3.56%. NEFA level was higher in restricted goats (p < 0.05). Fifty per cent of underfed goats (2/4) and all refed goats (4/4) exhibited oestrus and ovulation. Significant relationship (p < 0.05) was found between weight loss and the interval sponge removal-oestrus onset (r = 0.91) or ovulation rate (r = 0.70). Only in the refed group was the ovulation rate related to the oestradiol amount (r = 0.99) (p < 0.05). Collectively results showed that a short period of improved feeding re-established the responsiveness of oestrus synchronization in chronically fasted goats.

Using two PGF(2α) treatments 14 days apart as a way to enhance estrus detection rate following the 2nd treatment is a reproductive management tool that continues to be used on large dairy farms. In one study, in cows with a functional CL and a dominant follicle, treatment with cloprostenol vs. dinoprost resulted in greater peripheral estradiol concentrations. The objective of the present study was to determine if cloprostenol could enhance pregnancy rates of cows in a large dairy herd using a PGF(2α) program for 1st artificial insemination (AI). Lactating dairy cows (n = 4549) were randomly assigned to receive two treatments of either 500 μg cloprostenol or 25 mg dinoprost 14 days apart, with the 2nd treatment on the 1st day of the voluntary waiting period (57 DIM). Cows detected in estrus within 5 days after the 2nd treatment were inseminated. There was no effect of treatment on day of estrus detection, with 78% of cows inseminated on Days 3 or 4 following treatment. Cloprostenol increased (P < 0.01) estrus detection rates in 1st parity cows compared to dinoprost, 42.4 vs. 34.0%. In cows inseminated on Days 3 or 4 after treatment, cloprostenol increased (P = 0.05) conception rates compared to dinoprost, 38.3 vs. 34.4%. When treatments and parities were combined, conception rates increased (P < 0.02) with interval after treatment (27.0, 36.4, and 44.5% for Days 1 or 2, Days 3 or 4, and Day 5, respectively). Cloprostenol increased (P = 0.02) overall pregnancy rate compared to dinoprost, 14.4 vs. 12.2%. In summary, cloprostenol increased fertility in 1st parity cows inseminated on Days 3 or 4 following treatment and subsequently enhanced pregnancy rates of 1st parity lactating dairy cows compared to dinoprost. Fertility appeared greater in cows expected to have had a young antral ovarian follicle at treatment.

The intensity of induced oestrus in heifers on high and low nutritional planes was graded according to the degree of uterine contraction and cervical relaxation and the volume of oestrous mucus, and correlated with the pregnancy rates after insemination. In the heifers on a high nutritional plane, the heat was more intensely expressed and the conception rates were greater than in the poorly fed animals. In both groups the conception rate was lower in treated heifers than in untreated controls but this difference was minimal on a high plane of nutrition.

OBJECTIVE

To compare performance of the Ovsynch program on reproductive performance between cycling and non cycling cows in seasonally-calving herds.

METHODS

An Ovsynch mating program (100 mg Gonadorelin on day 1 and day 9, 500 mg of Cloprostenol on day 7 with fixed time artificial insemination on day 10) was administered to 3,559 cows from 14 herds in Australia and New Zealand. Cycling status before planned start of mating was determined. All cows were treated and artificial insemination continued for at least 25 days after fixed time artificial insemination. Pregnancy testing was performed 75 to 100 days after fixed time artificial insemination. Multivariable modelling examined the impact of the Ovsynch program and other risk factors upon reproductive performance.

RESULTS

Thirty percent of cows were classified as no visible oestrous (NVO). Odds of being NVO increased significantly for cows that were young, recently calved, and in low body condition. The fixed time artificial insemination conception rate was 35.7% and 33.2%, 21-day pregnancy rate was 54.5% and 48.4% and 42-day pregnancy rate was 69.7% and 62.6% for cycling and NVO cows respectively. Odds of pregnancy increased significantly for cows calved more than 40 days by planned start of mating, in greater body condition, and cycling, and there was a significant interaction between body condition and cycling status in both models. The return-to-service rates by 24-days were 67.6% and 55.9% and by the end of the AI period were 86.9% and 81.5% for cycling and NVO cows respectively. Odds of return to service increased significantly for cows in greater condition score in both models. Odds of return were increased for cycling cows in the 24-day multivariable model.

CONCLUSIONS

The Ovsynch program may provide a useful treatment option for NVO cows within seasonally-calving pasture-based dairy herds.

Conception to synchronized ovulation (Ovsynch) using injections of GnRH and PGF2alpha and timed artificial insemination has been shown to be maximized when the program is initiated 5 to 12 d after estrus. The objective of this double-blinded field trial was to assess the effect of one injection of PGF2alpha, 10 d before the Ovsynch program, on the probability of pregnancy at first insemination in lactating dairy cows. The hypothesis was that cows that underwent luteolysis in response to PGF2alpha would be between 5 and 8 d postestrus at the start of Ovsynch. In five commercial dairy herds in Ontario, Canada, at 52 +/- 12 d in milk, 506 cows were assigned at random to receive either one i.m. injection of 500 microg of cloprostenol or saline. Ten days later, all cows received 100 microg of GnRH i.m., followed in 7 d by 500 microg of cloprostenol i.m. and 100 microg of GnRH i.m. 48 h later. All cows were artificially inseminated 0 to 20 h after the second injection of GnRH, without regard to detection of estrus. Pregnancy was diagnosed by transrectal palpation at least 35 d after insemination. The probability of pregnancy after first insemination was modeled with logistic regression, accounting for the correlation of cows with herd and the effect of season of calving. There was no difference in pregnancy risk between cows that received PGF2alpha presynchronization and controls (37.3 and 36.6%, respectively; odds ratio = 1.03, 95% confidence interval, 0.88 to 1.20). Parity and days in milk at insemination were not significant covariates.

Previous studies have compared the effectiveness of dinoprost and cloprostenol in cows yielding conflicting results. The aim of our study was to evaluate the efficacy of single treatment with cloprostenol or dinoprost on estrus and reproductive performance in cows with unobserved estrus after service. The study was conducted over four years in two dairy herds of Polish Holstein Frisian cows under a herd health program with an average milk yield per cow over 9000 L. Cows (n=523) diagnosed ultrasonographically as non-pregnant and with a corpus luteum were randomly assigned to be treated with either cloprostenol (n=261) or dinoprost (n=262). The estrus detection rates after administration of cloprostenol or dinoprost were 59.4%, and 57.6%, respectively. The difference between both groups was not statistically significant (p>0.05). Distribution of observed estrus did not differ between cloprostenol and dinoprost. There were no differences (p>0.05) between cloprostenol and dinoprost in conception rate (65.2% vs. 66.2%, respectively) and pregnancy rate (57.5% vs. 54.9%, respectively). Mean days open were similar in cows of both treatments (177.5 ± 74.6 days vs. 175.8 ± 62.6 days, respectively; p>0.05). In conclusion, data from this study showed no significant differences in estrus detection rates and fertility between cows with unobserved estrus after service treated with cloprostenol or dinoprost. Both products are equally useful for the treatment of non-pregnant dairy cows with anestrus after service within a reproductive herd health program.