Synchronization of follicular wave emergence prior to superovulation in Bactrian camel (Camelus bactrianus)

This study was conducted to synchronize follicle wave emergence prior to superovulation using either GnRH or progestogen treatments, in Bactrian camels. GnRH group camels (n=5) received 20 microg of the GnRH analogue Buserelin on Days -18 and -4 of the experiment (initiation of superovulation=Day 0). Camels in the progestogen group (n=5) received two consecutive treatments of progestogens, 7 days apart, on Days -14 and -8 of the experiment. On each occasion, each female received three norgestomet implants and 200mg progesterone (i.m.) and all implants were removed 14 days after the first progestogen treatment coinciding with Day -1 of superovulation. A combination of eCG and FSH was used to induce superovulation and the growth of all subsequent follicles and CLs were monitored daily by ultrasonography. Following the first GnRH injection, mature follicles ovulated within 1-2 days, and a new follicle wave emerged after 3+/-0.77 days. At the time of the second GnRH injection, a mature follicle (15.6+/-0.97 mm) ovulated and a new follicular wave emerged between 1 and 2 days after GnRH injection. Growing follicles at the time of the first progestogen treatment became either atretic (n=1) or persistent (n=4) and a new follicle wave (n=3) emerged 3-6 days later. At the initiation of superovulation, the diameters of the largest follicle in GnRH and progestogen groups were 7.4+/-0.59 and 20.5+/-2.26 mm, respectively but after superovulation and mating there was no significant differences in the number of unovulated follicles or CLs between groups. In conclusion, two GnRH injections, 14 days apart, may be used to synchronize follicle wave emergence in Bactrian camel.     

Failure of the LH-releasing hormone agonist, deslorelin, to prevent development of a persistent follicle in heifers synchronized with norgestomet

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.     

Effect of purified llama ovulation-inducing factor (OIF) on ovarian function in cattle

Two experiments were designed to determine the effect of purified ovulation inducing factor (OIF) on ovarian function in cattle. In Experiment 1, prepubertal heifers (n = 11 per group) were treated on Day 5 (Day 0 = day of follicular wave emergence) of the follicular wave with an intramuscular dose of saline (1 mL), GnRH (100 μg), or purified OIF (1 mg/100 kg body weight). Ovulation occurred in 9/11 heifers treated with GnRH, and 1/11 heifers in each of the OIF- and saline-treated groups (P < 0.05). Compared to saline-treated controls, OIF treatment was associated with a smaller dominant follicle diameter (P < 0.01), a rise in plasma FSH concentration (P < 0.1), and earlier emergence of the next follicular wave (P < 0.05). In Experiment 2, sexually mature heifers were given either GnRH or purified OIF on Days 3, 6 or 9 of the first follicular wave (i.e., early growing, early static, or late static phase of the dominant follicle; n = 5 per group per day), or were untreated (n = 10). In heifers treated with OIF on Day 6, the dominant follicle diameter profile tended to be smaller than in controls, and was associated with a rise (P < 0.05) in plasma FSH concentrations. A similar rise in FSH was detected after OIF treatment on Day 9. Compared to untreated controls, treatment with OIF and GnRH was associated with a larger CL diameter (Days 3 and 6 groups; P < 0.05) and a greater concentration of plasma progesterone (Days 6 and 9 groups; P < 0.05). Treatment with purified OIF did not induce ovulation in heifers, but hastened new follicular wave emergence in prepubertal heifers, influenced follicular dynamics in a phase-specific manner in mature heifers, and was luteotrophic.     

Deslorelin on Day 8 or 12 postovulation does not luteinize follicles during an artificially maintained diestrous phase in the mare

Practical estrus synchronization schemes are needed for mares. The Ovsynch synchronization protocol for cattle involves the administration of gonadotropin-releasing hormone (GnRH) to induce ovulation or luteinization of dominant follicles during the luteal phase and prostaglandin 7 days later to cause regression of any luteal tissue and development of a preovulatory follicle. An Ovsynch-type synchronization program potentially could be developed for horses if luteinization or ovulation of diestrous follicles occurred in response to GnRH treatment. The objective of this study was to determine if administration of the GnRH agonist, deslorelin acetate, on Day 8 or 12 postovulation would induce luteinization or ovulation of diestrous follicles in the mare. The model used was cycling mares maintained in an artificial luteal phase by administration of a synthetic progestin following prostaglandin-induced luteal regression. On the day of ovulation, 21 light horse mares were randomly assigned to one of three groups: (1) no GnRH, altrenogest from Days 5 to 15 postovulation with prostaglandin on Day 15; (2) GnRH on Day 8, altrenogest from Days 5 to 15 with prostaglandin given on Day 6 to induce luteolysis of the primary corpus luteum, an implant containing 2.1mg of deslorelin acetate inserted on Day 8 and removed on Day 10, with a second prostaglandin treatment on Day 15; (3) GnRH on Day 12, altrenogest from Days 9 to 19, prostaglandin on Day 10, a deslorelin acetate implant injected on Day 12 (subsequently removed on Day 14), and a second dose of prostaglandin administered on Day 19. Follicular development was monitored every other day from Day 5 until a 30-mm sized follicle was observed, and then daily to detection of ovulation. Serum progesterone concentrations were determined daily for 12 consecutive days. Progesterone concentrations in Group 1 remained elevated until approximately Day 12 postovulation. Prostaglandin administration on Day 15 resulted in complete luteolysis in all seven mares. In Group 2, progesterone concentrations in six of seven mares declined to baseline after prostaglandin treatment. No increase in serum progesterone was noted in any of the six mares that were given GnRH on Day 8, including three mares that had diestrous follicles > or =30mm in diameter at the time of treatment. Similarly, progesterone concentrations in six of seven mares in Group 3 declined to baseline after prostaglandin and there was no increase in progesterone after administration of GnRH on Day 12. No ultrasound evidence of luteinization or ovulation of diestrous follicles were noted after GnRH administration in any mares of Group 2 or 3. In conclusion, administration of the GnRH agonist deslorelin acetate to mares failed to induce luteinization or ovulation of diestrous follicles. Consequently, the Ovsynch program (as used in cattle) has little efficacy for synchronization of estrus in mares.     

Synchronisation of ovarian follicular waves in the dromedary camel (Camelus dromedarius)

This study was designed to compare the efficacy of various treatments intended to synchronise follicular wave cycles in dromedary camels by removing the existing follicle of unknown size and replacing it with a follicle capable of ovulating at a known time. Camels were randomly assigned to one of five groups and treated with either (1) 5mg oestradiol benzoate (i.m.) and 100mg progesterone (i.m.; E/P, n=15), (2) 20 icrog GnRH analogue, buserelin (i.m.; GnRH, n=15), (3) 20 microg buserelin (i.m.) on Day 0 (T=0) and 500 microg prostaglandin on Day T+7 (GnRH/PG n=15), (4) transvaginal ultrasound-guided follicle ablation of all follicles > or =0.5 cm (ABL, n=15) or (5) 5 ml saline (i.m; Controls n=15). All camels were subsequently injected with 20 microg buserelin 14 days after the first treatment was given. The ovarian response was monitored daily by transrectal ultrasonography and the intervals from treatment to follicular wave emergence and also the day on which the new dominant follicle reached 1.3 cm was recorded. Amongst the treatment groups the mean interval from treatment to new follicle wave emergence and treatment to time taken for the new dominant follicle to reach 1.3 cm in diameter was shortest in the ABL group (2.3+/-0.5 days and 8.8+/-1.1 days respectively, P=0.044) and longest in the E/P group (6.4+/-0.8 days and 12.2+/-1.0 days respectively, P<0.001) whereas the GnRH and GnRH/PG groups were intermediate (3.0+/-0.5 days and 11.1+/-0.8 days GnRH; and 4.5+/-0.5 days and 10.7+/-0.7 days GnRH/PG). A total of 11/15 camels in both the GnRH and GnRH/PG groups had dominant follicles between 1.3 and 1.9 cm 14 days post treatment, of which 21 of the 22 follicles ovulated after GnRH injection on T+14. The ABL, E/P and control groups however, showed greater variability in follicle size with less camels having dominant follicles between 1.3 and 1.9 cm than the GnRH and GnRH/PG groups and more in the > or =2.0 cm or follicle regressing groups, therefore fewer of these camels ovulated (ABL n=7; E/P n=9; Control n=6) after GnRH injection on Day T+14. In conclusion, two GnRH injections 14 days apart or two GnRH injections 14 days apart and PG on Day 7 after the first GnRH were the most effective methods to synchronise ovulation rate in dromedary camels at a fixed time interval of 14 days after treatment.     

Comparison of three methods of acute administration of progesterone on ovarian follicular development and the timing and synchrony of ovulation in Bos indicus heifers

The aim of this study was to induce the formation of a persistent dominant ovarian follicle and to compare the effects of 3 methods of acute administration of P4 on ovarian follicular development and on the timing and synchrony of ovulation. Stage of the estrous cycle was initially synchronized in Bos indicus heifers with a norgestomet implants (3 mg) for 10 d and with an analogue of PGF2 alpha (15 mg) on the first and last day of norgestomet treatment. Eight days after removal of the implants, heifers were randomly assigned to 4 groups. All heifers received a norgestomet implant (Day 0), which was removed 17 d later (Day 17); PGF2 alpha was administered on Days 0 and 4. Heifers in the control group (n = 5) received no other treatment. On Day 10 heifers in Group P4C (n = 5) were treated with a CIDR for 24 h; heifers in Group P4O (n = 5) were administered 100 mg i.m. of P4 in oil, while heifers in Group P4S (n = 5) were administered 100 mg i.m. of P4 in saline/alcohol. Data were analyzed using bootstrap estimates of location (mean) and spread (standard deviation; SD). Compared with the control heifers, day of emergence of the ovulatory follicle was delayed, and age and duration of dominance of the ovulatory follicle were reduced in the P4C and P4O heifers (P < 0.05) but not in the P4S heifers (P > 0.05). In all groups treated with P4 both the mean and variability (SD) in the timing of ovulation did not differ with that of the control group (P > 0.05) but there was less variability in the day of emergence, age, duration of dominance and diameter of the ovulatory follicle than in the control group (P < 0.05). Delayed timing and reduced synchrony (SD) of ovulation and greater age of the ovulatory follicle (P < 0.05) occurred in P4S heifers than in P4C heifers. We conclude that administration of 100 mg of P4 in oil is as effective as treatment with a CIDR for synchronizing emergence and ovulation of a newly recruited dominant follicle. However, reduced synchrony of ovulation, greater age of the ovulatory follicle and delayed timing of ovulation occurred following administration 100 mg of P4 in saline/alcohol compared with the CIDR device.     

Induction of ovulation in nonlactating dairy cows and heifers using different doses of a deslorelin implant

The objective of this study was to evaluate ovarian function after inducing ovulation with a deslorelin implant in nonlactating dairy cows and heifers. Cattle received GnRH on Day -9, and PGF2alpha on Day -2. On Day 0, in Experiment 1, cows received either 100 microg GnRH (Control), a 750 microg (DESLORELIN 750) or 1000 microg (DESLORELIN 1000) deslorelin implant. On Day 0, in Experiment 2, cows received 100 microg of GnRH or a 450 microg (DESLORELIN 450) deslorelin implant. In Experiments 1 and 2, cows received PGF2alpha on Day 16. Ultrasonography and blood sampling for plasma progesterone (P4) were used to monitor ovarian activity. On Day 0, in Experiment 3, heifers received either 100 microg of GnRH or 750 microg (DESLORELIN 750) deslorelin implant. On Day 16, all heifers received PGF2alpha. Blood samples were collected on Days 7, 13 and 16. In Experiments 1-3, deslorelin implants did not elevate plasma concentrations of P4 in a systematic manner during the late luteal phase. In Experiments 1 and 2, deslorelin implants decreased the size of the largest follicle and the number of Class II and III follicles. In Experiments 1 and 2, deslorelin-treated cows failed to ovulate by Day 28. In conclusion, deslorelin implants induced ovulation, stimulated development of a normal CL, and delayed follicular growth during the subsequent diestrus period. For future applications, the dose of the deslorelin implant will have to be adjusted, and if used for timed-inseminations, nonpregnant cows will have to be resynchronized to minimize delayed returns to estrus and ovulation.     

Follicular wave emergence, luteal function and synchrony of ovulation following GnRH or estradiol benzoate in a CIDR-treated, lactating Holstein cows

This study evaluated the effect of GnRH or estradiol benzoate (EB) on follicular wave emergence and progesterone concentrations, and following a second injection of GnRH, synchrony of ovulation, and pregnancy rates in a controlled internal drug release (CIDR)-based timed AI (TAI) protocol in lactating Holstein cows. Cows received a CIDR device without hormone (controls), with an injection of 100 microg GnRH or with an injection of 4 mg EB. Thereafter, all received PGF(2 alpha) at the time of CIDR removal on Day 7, GnRH on Day 9, and TAI 16 h later. Follicular wave emergence occurred within 7 days in 19/20 GnRH-treated, 14/20 EB-treated and 5/20 control cows (P < 0.05). The interval to wave emergence was the shorter and less variable (P < 0.01) in the GnRH group (2.9 +/- 0.2 days) than in the EB (4.7 +/- 0.5 days) or control (4.8 +/- 1.0 days) groups. Serum progesterone concentrations from Days 4 to 7 were higher (P < 0.01) in the GnRH-treated cows that ovulated than in those that did not ovulate, or in control and EB-treated cows. The diameters of dominant follicle on Day 7 differed among groups (P < 0.01), and the diameters of the preovulatory follicle on Day 9 were larger (P < 0.01) in the control and GnRH groups than in the EB group. The proportion of cows with synchronized ovulations did not differ among groups, but pregnancy rate to TAI was higher (P < 0.05) in the GnRH group (65%; 13/20) than in the control (30%; 6/20) or EB (35%; 7/20) groups. Results suggest that GnRH treatment of CIDR-treated lactating Holstein cows will result in synchronous follicular wave emergence, large preovulatory follicles and synchronous ovulation, resulting in an acceptable pregnancy rates to TAI.     

Effects of estradiol-17β and hCG supplementation on superovulatory responses and embryo quality in swamp buffalo (Bubalus bubalis) implanted with norgestomet

Twenty-four cycling swamp buffaloes with normal reproductive histories and 2–3 months postpartum were used to investigate the effect of addition of estradiol-17β and human chorionic gonadotrophin (hCG) to the superovulation regime on the level of ovarian stimulation and embryo production.The estrous cycles of buffaloes were synchronized by prostaglandin injection and then divided into two groups for superovulatory treatment. Those in Group 1 (n = 12) received a implant containing 3 mg norgestomet (Syncro-Mate-B) for 9 days (insertion day is Day 0), with 4000 IU of equine chorionic gonadotrophin (eCG) and 500 μg cloprostenol i.m. given at Day 7. Group 2 (n = 12) received the same regime as Group 1, together with 7.5 mg estradiol-17β given in three intramuscular injections on Days 3, 5 and 7 in decreasing doses (4.0, 2.5 and 1.0 mg, respectively) and 5000 I.U hCG i.v. coincidentally with the first insemination. Estrus was monitored visually and by placing treated animals with bulls. Each animal was inseminated twice with frozen sperm after standing estrus. The numbers of corpora lutea (CL) and follicles greater than 8 mm in diameter were recorded via palpation per rectum at 6 days after implant removal. Two days later 11 animals from Group 2 and two from Group 1 were slaughtered for direct observation of ovarian responses and for embryo collection.The mean number of CL were 0.91 ± 0.66 and 9.08 ± 5.0 for Groups 1 and 2, respectively. The average recovery rate based on CL counts at slaughter was 60% in Group 2. No embryos were recovered from the two animals in Group 1. Seventy-nine percent of the collected ova were fertilized and more than 60% of them had developed into hatched blastocysts. The percentages of buffalo with excellent and good estrus were 41.6 and 91.6% for Groups 1 and 2, respectively.These results showed that the supplementation of estradiol-17β and the hCG treatment significantly improved the level of ovarian stimulation in swamp buffalo.     

Equine chorionic gonadotropin and gonadotropin-releasing hormone enhance fertility in a norgestomet-based, timed artificial insemination protocol in suckled Nelore (Bos indicus) cows

Two experiments were conducted to investigate the effects of equine chorionic gonadotropin (eCG) at progestin removal and gonadotropin-releasing hormone (GnRH) at timed artificial insemination (TAI) on ovarian follicular dynamics (Experiment 1) and pregnancy rates (Experiment 2) in suckled Nelore (Bos indicus) cows. Both experiments were 2 × 2 factorials (eCG or No eCG, and GnRH or No GnRH), with identical treatments. In Experiment 1, 50 anestrous cows, 134.5 ± 2.3 d postpartum, received a 3 mg norgestomet ear implant sc, plus 3 mg norgestomet and 5 mg estradiol valerate im on Day 0. The implant was removed on Day 9, with TAI 54 h later. Cows received 400 IU eCG or no further treatment on Day 9 and GnRH (100 μg gonadorelin) or no further treatment at TAI. Treatment with eCG increased the growth rate of the largest follicle from Days 9 to 11 (means ± SEM, 1.53 ± 0.1 vs. 0.48 ± 0.1 mm/d; P < 0.0001), its diameter on Day 11 (11.4 ± 0.6 vs. 9.3 ± 0.7 mm; P = 0.03), as well as ovulation rate (80.8% vs. 50.0%, P = 0.02), whereas GnRH improved the synchrony of ovulation (72.0 ± 1.1 vs. 71.1 ± 2.0 h). In Experiment 2 (n = 599 cows, 40 to 120 d postpartum), pregnancy rates differed (P = 0.004) among groups (27.6%, 40.1%, 47.7%, and 55.7% for Control, GnRH, eCG, and eCG + GnRH groups). Both eCG and GnRH improved pregnancy rates (51.7% vs. 33.8%, P = 0.002; and 48.0% vs 37.6%, P = 0.02, respectively), although their effects were not additive (no significant interaction). In conclusion, eCG at norgestomet implant removal increased the growth rate of the largest follicle (LF) from implant removal to TAI, the diameter of the LF at TAI, and rates of ovulation and pregnancy rates. Furthermore, GnRH at TAI improved the synchrony of ovulations and pregnancy rates in postpartum Nelore cows treated with a norgestomet-based TAI protocol.     

Synchronization of estrus and fertility in beef cattle with two injections of buserelin and prostaglandin

Postpartum beef cows and heifers in Group 1 received 8 mug of buserelin on Day 0 (the beginning of the experiment) and 500 mug of cloprostenol (PGF) on Day 6 (GnRH I, n = 54). In Group 2 (GnRH II, n = 54), the females were injected with buserelin on Day 0 (8 mug) and Day 3 (4 mug), and PGF on Day 6 and Day 9 for females not detected in estrus previously. Animals were bred by AI 12 hours after the onset of estrus. Blood samples were collected on Day -11 and Day 0 to assess cyclicity and on Day 3 and Days 6 to 12 to examine luteal activity. Progesterone levels did not differ between the 2 groups between Days 0 to 9. In both groups, the proportion of spontaneous estruses from Days 0 to 6 was reduced. Precision of estrus was higher (P < 0.005) in the GnRH II group than in the GnRH I group of cows that were detected in estrus between Days 6 and 9. The synchronization rate, interval to estrus, pregnancy and conception rates were similar in GnRH I and GnRH II groups. The conception rate and interval to estrus were similar in cyclic and acyclic cows. Increasing the number of buserelin injections enhanced the precision of estrus, but not the conception rate, without any detrimental effect on luteal activity and induced more estruses in postpartum acyclic beef cattle.     

Effect of estradiol valerate on ovarian follicle dynamics and superovulatory response in progestin-treated cattle

Three experiments evaluated the effects of estradiol valerate (EV) on ovarian follicular and CL dynamics, intervals to estrus and ovulation, and superovulatory response in cattle. Experiment 1 compared the efficacy of two norgestomet ear implants (Crestar and Syncro-Mate B; SMB) for 9 d (with PGF at implant removal), combined with either 5 mg estradiol-17beta and 100 mg progesterone (EP) or 5 mg EV and 3mg norgestomet (EN) im at the time of implant insertion on CL diameter and follicular wave dynamics. Ovaries were monitored by ultrasonography. There was no effect of norgestomet implant. Diameter of the CL decreased following EN treatment (P < 0.01). Mean (+/- S.D.) day of follicular wave emergence (FWE) was earlier (P < 0.0001) and less variable (P < 0.0001) in EP- (3.6 +/- 0.5 d) than in EN- (5.7 +/- 1.5 d) treated heifers. Intervals from implant removal to estrus (P < 0.001) and ovulation (P < 0.01) were shorter in EN- (45.7 +/- 11.7 and 74.3 +/- 12.6 h, respectively) than in EP- (56.4 +/- 14.1 and 83.3 +/- 17.0 h, respectively) treated heifers. Experiment 2 compared the efficacy of EP versus EN in synchronizing FWE for superovulation in SMB-implanted cows. At random stages of the estrous cycle, Holstein cows (n = 78) received two SMB implants (Day 0) and were randomly assigned to receive EN on Day 0 or EP on Day 1. Folltropin-V treatments were initiated on the evening of Day 5, with PGF in the morning and evening of Day 8, when SMB were removed. Cows were inseminated after the onset of estrus and embryos were recovered 7 d later. Non-lactating cows had more CL (16.7 +/- 11.3 versus 8.3 +/- 4.9) and total ova/embryos (14.7 +/- 9.5 versus 7.9 +/- 4.6) than lactating cows (P < 0.05). EP-treated cows tended (P = 0.09) to yield more transferable embryos (5.6 +/- 5.2) than EN-treated cows (4.0 +/- 3.7). Experiment 3 compared the effect of dose of EV on ovarian follicle and CL growth profiles and synchrony of estrus and ovulation in CIDR-treated beef cows (n = 43). At random stages of the estrous cycle (Day 0), cows received a CIDR and no further treatment (Control), or an injection of 1, 2, or 5 mg im of EV. On Day 7, CIDR were removed and cows received PGF. Follicular wave emergence occurred within 7 d in 7/10 Control cows and 31/32 EV-treated cows (P < 0.05). In responding cows, interval from treatment to FWE was longer (P < 0.05) in those treated with 5 mg EV (4.8 +/- 1.2 d) than in those treated with 1 mg (3.2 +/- 0.9 d) or 2 mg (3.4 +/- 0.8 d) EV, while Control cows were intermediate (3.8 +/- 2.0 d). Diameter of the dominant follicle was smaller (P < 0.05) at CIDR removal and tended (P = 0.08) to be smaller just prior to ovulation in the 5 mg EV group (8.5 +/- 2.2 and 13.2 +/- 0.6 mm, respectively) than in the Control (11.8 +/- 4.6 and 15.5 +/- 2.9 mm, respectively) or 1mg EV (11.7 +/- 2.5 and 15.1 +/- 2.2 mm, respectively) groups, with the 2mg EV group (10.7 +/- 1.5 and 14.3 +/- 1.7 mm, respectively) intermediate. Diameter of the dominant follicle at CIDR removal was less variable (P < 0.01) in the 2 and 5mg EV groups than in the Control group, and intermediate in the 1mg EV group. In summary, treatment with 5mg EV resulted in a longer and more variable interval to follicular wave emergence than treatment with 5mg estradiol-17beta, which affected preovulatory dominant follicle size following progestin removal, and may have also affected superstimulatory response in Holstein cows. Additionally, 5 mg EV appeared to induce luteolysis in heifers, reducing the interval to ovulation following norgestomet removal. Conversely, intervals to, and synchrony of, follicular wave emergence, estrus and ovulation following treatment with 1 or 2 mg EV suggested that reduced doses of EV may be more useful for the synchronization of follicular wave emergence in progestogen-treated cattle.     

Follicular dynamics and temporal relationships among body temperature, oestrus, the surge of luteinizing hormone and ovulation in Holstein heifers treated with norgestomet

The effects of chronic treatment with norgestomet on follicular dynamics, corpus luteum growth and function as well as the temporal relationships among body temperature, oestrous behaviour, the luteinizing hormone (LH) surge and ovulation following implant removal were studied in 16 Holstein heifers. Oestrous cycles of the heifers were initially synchronized using 2 injections of prostaglandin F-2 alpha (PGF-2 alpha) 12 days apart. The heifers were then implanted with a norgestomet ear implant for 9 days, beginning either at the middle of the synchronized cycle (dioestrus) or at the end of the synchronized cycle (pro-oestrus). Follicular dynamics, corpus luteum growth and regression, and plasma progesterone were not affected by norgestomet treatment at dioestrus. The dominant follicle present at the time of norgestomet implantation in the pro-oestrus group was maintained during the 9-day implant period of 6 of 8 heifers and ovulated after implant removal. Time from implant removal to onset of standing oestrus and time to LH peak following implant removal were highly correlated with the time of ovulation (r = 0.92 and 0.96, respectively). Onset of standing oestrus and the LH peak and the onset of standing oestrus and peak vaginal and rectal temperatures were also highly correlated (r = 0.96, 0.82 and 0.81, respectively). It is concluded that any decrease in pregnancy rates following treatment with norgestomet is not due to asynchrony among oestrus, the LH surge and ovulation.     

Close synchrony of ovulation in superstimulated heifers that have a downregulated anterior pituitary gland and are induced to ovulate with exogenous LH

The synchrony of ovulation was examined in superstimulated heifers that had a downregulated pituitary gland and which were induced to ovulate by injection of exogenous LH. The pituitary was downregulated and desensitized to GnRH by treatment with the GnRH agonist deslorelin. Nulliparous heifers (3.5 yr old) at random stages of the estrous cycle were assigned to 1 of 3 groups, and on Day -7 received the following treatments: Group 1 (control, n = 8), 1 norgestomet ear implant; Group 2 (GnRH agonist, n = 8); Group 3 (GnRH agonist-LH protocol, n = 8), 2 deslorelin ear implants. Ovarian follicle growth in all heifers was superstimulated with twice-daily intramuscular injections of FSH (Folltropin-V): Day O, 40 mg (80 mg total dose); Day 1, 30 mg; Day 2; 20 mg; Day 3, 10 mg. On Day 2, all heifers were given a luteolytic dose of PGF (7 A.M.), Norgestomet implants were removed from heifers in Group 1 (6 P.M.). Heifers in Group 3 were given an injection of 25 mg, i.m. porcine LH (Lutropin) on Day 4 (4 P.M.). Ovarian follicle status was monitored at 8-h intervals from Day 3 (8 A.M.) to Day 6 (4 P.M.) using an Aloka Echo Camera and 7.5 MHz transducer. Heifers in Groups 2 and 3 exhibited estrus earlier (P < 0.05) than heifers in Group 1. Heifers in Group 2 did not have a preovulatory LH surge and they did not ovulate. Individual control heifers in Group 1 ovulated between 12 A.M. on Day 5 and 8 A.M. on Day 6. Heifers with deslorelin implants and injected with LH in Group 3 ovulated between 4 P.M. on Day 5 and 8 A.M. on Day 6. It was confirmed that superstimulated heifers with GnRH agonist implants can be induced to ovulate with LH. It was also demonstrated that ovulation is closely synchronized after injection of LH. Thus, a single, fixed-time insemination schedule could be used in a GnRH agonist-LH superovulation protocol, with significant practical and economic advantages for superovulation and embryo transfer programs.     

Induction of a new follicular wave in holstein heifers synchronized with norgestomet

Treatments with progestin to synchronize the bovine estrous cycle in the absence of the corpus luteum, induces persistence of a dominant follicle and a reduction of fertility at doses commonly utilized. The objective of the present research was to induce a new wave of ovarian follicular development in heifers in which stage of the estrous cycle was synchronized with norgestomet. Holstein heifers (n=30) were used, in which estrus was synchronized using two doses of PGF2alpha i.m. (25 mg each) 11 days apart. Six days after estrus (day 0=day of estrus) heifers received a norgestomet implant (6 mg of norgestomet). On day 12, heifers were injected with 25 mg of PGF2alpha i.m. and assigned to treatments (T1 to T4) as follows: treatment 1, heifers received a second norgestomet implant (T1: N+N, n=6), treatment 2, received 100 microg of GnRH i.m. (T2: N+GnRH, n=6), treatment 3, 200 mg of progesterone i.m. (T3: N+P4, n=6), treatment 4, control treatment with saline solution i.m. (T4: N+SS); in the four treatments (T1 to T4) implants were removed on day 14. For treatment 5, heifers received 100 microg of GnRH i.m. on day 9 and 25 mg of PGF2alpha i.m. (T5: N+GnRH+PGF2alpha) at the time of implant removal (day 16). Ovarian evaluations using ultrasonographic techniques were performed every 48 h from days 3 to 11 and every 24 h from days 11 to 21. Blood samples were collected every 48 h to analyze for progesterone concentration. A new wave of ovarian follicular development was induced in 3/6, 6/6, 3/6, 1/6 and 6/6, and onset of estrus in 6/6, 0/6, 6/6, 6/6 and 6/6 for T1, T2, T3, T4 and T5, respectively. Heifers from T1, T3 and T4 that ovulated from a persistent follicle, showed estrus 37.5 +/- 12.10 h after implant removal and heifers that developed a new wave of ovarian follicular development showed it at 120.28 +/- 22.81 h (P<0.01). Ovulation occurred at 5.92 +/- 1.72 and 2.22 +/- 1.00 days (P<0.01), respectively. Progesterone concentration was <1 ng/ml from days 7 to 15 in T1, T2 and T4; for T3 progesterone concentration was 2.25 +/- 0.50 ng/ml on day 13 and decreased on day 15 to 0.34 +/- 0.12 ng/ml (P<0.01). For T5, progesterone concentration was 1.66 +/- 0.58 ng/ml on day 15. The more desirable results were obtained with T5, in which 100% of heifers had a new wave of ovarian follicular development induced, with onset of estrus and ovulation synchronized in a short time period.     

The effects of exclusion of progesterone or Day 0 GnRH from a GnRH,prostaglandin, GnRH + progesterone program on synchronization of ovulation in pasture-based dairy heifers

This study evaluated the effect of removing the GnRH injection on Day 0 or the progesterone (P4) device from a GnRH, PGF2α, GnRH (GPG) + P4 program on follicular dynamics and synchronization of ovulation in dairy heifers. Friesian and Friesian × Jersey heifers, in autumn 2009 (n = 35) and spring 2010 (n = 38), were randomly allocated to one of three estrus synchronization programs. The first group (GPG + P4) received 100 μg GnRH on Day 0, a P4-releasing intravaginal device from Days 0 to 7, 500 μg PGF2α on Day 7, and 100 μg GnRH on Day 9, followed by fixed-time artificial insemination 16 to 20 hours later. The program for group 2 (GPG) was the same as group 1 with the exclusion of the P4 device. Group 3 (P + G + P4) was treated the same as group 1, except for the absence of the GnRH treatment on Day 0. Ultrasonography was performed on Days 0, 1, 2, 3, and 7 and then at 12 hourly intervals on Days 9 to 11. Dominant follicle size was affected by both treatment and day, and there was also a significant interaction (P < 0.02) between treatment and day. Mean dominant follicle size was larger in the heifers treated with P + G + P4 on Days 1 to 3 than those treated with GPG + P4 (P < 0.02) and, on Day 2, than those treated with GPG (P = 0.005). However, on Day 7, mean dominant follicle size was larger in heifers treated with GPG than heifers treated with P + G + P4 (P = 0.03). The emergence of a new follicular wave was later in heifers treated with P + G + P4 than heifers, which received a GnRH injection on Day 0 (4.3 ± 0.7 days, compared with combined GPG + P4 and GPG 3.0 ± 0.3 days; P = 0.03). The proportion of heifers that ovulated within the first 48 hours after the Day 9 injection of GnRH was not affected by treatment (GPG, 81%; GPG + P4, 84%; and P + G + P4, 100% [including early ovulation]; P = 0.11). The timing of the ovulation was not different between treatments (P = 0.97).     

Changes in the cumulus-oocyte complex of subordinate follicles relative to follicular wave status in cattle

We investigated factors that affect cumulus-oocyte complex (COC) morphology and oocyte developmental competence in subordinate follicles on different days after follicular wave emergence in beef heifers. In Experiment 1, heifers (n = 13) were assigned at random to COC aspiration during the growing/static (Days 1 to 3) or regressing (Day 5) phase of subordinate follicle development (follicular wave emergence = Day 0). Follicular wave emergence was induced by transvaginal ultrasound-guided follicular ablation, ovaries were collected at slaughter, all follicles > or = 2 mm except the dominant follicle were aspirated, and COC were microscopically evaluated for morphology. There was a greater percentage of COC with expanded cumulus layers on Day 5 (42.4%) than on Days 1 to 3 (2.2%). In Experiment 2, heifers (n = 64) at random stages of the estrous cycle had all follicles > or = 5 mm ablated and 4 d later, 2 doses of PGF were injected 12 h apart; heifers were monitored daily by ultrasonography for ovulation (Day 0 = follicular wave emergence). Heifers were assigned to the following time periods for oocyte collection from subordinate follicles: Days 0 and 1 (growing phase), Days 2, 3 and 4 (static phase), and Days 5 and 6 (regressing phase). Ovaries were individually collected at slaughter, and all follicles > or 2 mm except for the dominant follicle were aspirated. The COC were morphologically evaluated and then matured, fertilized and cultured in vitro. Expanded COC were more frequent during the regressing phase (53.4%) than the growing or static phase (14.4 and 17.8%, respectively; P < 0.05). While the proportions of COC with > or = 4 layers of cumulus cells and denuded oocytes were higher (P < 0.05) in the growing and static phases, the production of morulae was highest (P < 0.05) with COC collected from subordinate follicles during the regressing phase. In Experiment 3, heifers (n = 18) were assigned at random to oocyte collection from subordinate follicles 3 and 4 d (static phase) or 5 and 6 d (regressing phase) after follicular wave emergence. The heifers were monitored ultrasonically for ovulation (Day 0 = follicular wave emergence); COC were collected from all follicles (> or = 5 mm) except for the dominant follicle by transvaginal ultrasound-guided follicle aspiration 3 to 6 d later. Recovered oocytes were stained and examined microscopically to evaluate nuclear maturation. A higher proportion of oocytes collected on Days 5 and 6 showed evidence of nuclear maturation (50%) than on Days 3 and 4 (8.3%; P < 0.05). Results support the hypothesis that COC morphology and oocyte developmental competence change during the growing, static and regressing phases of subordinate follicle development.     

The effect of interval from day of administration of bovine somatotropin (bST) to synchronization of ovulation and timed-insemination on conception rate of dairy cows with and without ovarian cysts

The objective of this study is to evaluate the effect of the interval from the day of administration of bovine somatotropin (bST) to the day of initiation of synchronization of ovulation (Day 0 and 7) and timed-insemination (TAI) on conception rate (CR) of dairy cows with and without ovarian cysts, respectively. Lactating dairy cows (n = 359) were divided into two groups. Cows in Group 1 (n = 238, without ovarian cysts) were treated with 100 microg, i.m. GnRH on Day 0; 25 mg, i.m. PGF2a on Day 8. 100 mirog. i.m. GnRH on Day 10; and inseminated 16 h later without detection of estrus. Cows in Group 2 (n = 121, with ovarian cysts) were treated with 100 microg, i.m. GnRH on Day 0; 100 microg, i.m. GnRH on Day 7; 25 mg, i.m. PGF2alpha on Day 14, 100 ug, i.m. GnRH on Day 16; and inseminated 16 h later without detection of estrus. Between 60 and 63 days postpartum, all cows in the herd were given bST every 14 days for the duration of the study. Logistic regression was used to assess the risk of nonpregnancy associated with interval from bST treatment to Day 0 for cows without ovarian cysts. and both Day 0 and 7 for cows with ovarian cysts adjusting for parity and days in milk. The CR for cows in Group 1 was significantly higher when the interval from last treatment with bST to Day 0 was between 1 and 3 days (28%) compared to 4-6 days (14%). In addition, the risk of nonpregnancy was 2.19 times greater in cows 4-6 days after bST treatment compared to 1-3 days after adjusting for parity and days in milk. The CR for cows in Group 2 was not significantly different when the interval from last treatment with bST to both Day 0 and 7 was between 1 and 3, 4 and 6, and 7 and 14 days. In conclusion, the results of this study suggested bST treatment closer to Day 0 had a positive effect on CR of cows without ovarian cysts, but bST treatment closer to both Day 0 and 7 had no effect on CR of cows with ovarian cysts. This was interpreted to mean that bST had a beneficial effect on either, or both, the preovulatory follicle and the oocyte in dairy cows without ovarian cysts, but not in dairy cows with ovarian cysts.     

Reproductive performance of dairy cows with ovarian cysts after different GnRH and cloprostenol treatments

Cystic ovarian disease is an important cause of reproductive failure and economic loss for the dairy industry. This report describes two consecutive studies. The objective of the first was to evaluate the response of cows with ovarian cysts to two therapeutic treatments. In the second study, we compared the effectiveness of the best treatment established in Study 1 with that of the Ovsynch protocol. For Study 1, cows were considered to have an ovarian cyst if it was possible to observe a single follicular structure with a follicular antrum diameter > 25 min in the absence of a corpus luteum in three ultrasonographic examinations performed at 7 days intervals. At diagnosis (Day 0), cows were assigned to one of two treatment groups. Cows in Group GnRH/CLP (n = 31) were treated with 100 microg GnRH i.m. and 500 microg cloprostenol (CLP) i.m. on Day 14. Cows in Group GnRH-CLP/CLP(n = 32) were treated with 100 microg GnRH i.m. plus 500 microg CLP i.m. on Day 0, and 500 microg CLP i.m. on Day 14. The animals were inseminated at observed estrus and monitored weekly by ultrasonography for 4 weeks or until Al. Cows in the GnRH-CLP/CLP group showed a lower cystic persistence rate (15.6% < 45.2%; P = 0.01); a higher estrus detection rate (84.4% > 41.9%; P < 0.0001); a higher ovulation rate (75% versus 32.3%; P < 0.0001) and a higher early response rate (31% > 3%; P = 0.02) than those in the GnRH/CLP group. For the second study, 128 cows with ovarian cysts were randomly assigned to one of two treatment groups: cows in Group Ovsynch (n = 64) were treated with 100 microg GnRH i.m. on Day 0, 500 microg CLP on Day 7, and 100 microm GnRH i.m. 36 h later. Cows in this group were inseminated 24 h after the second GnRH dose (Ovsynch protocol). Cows in Group GnRH-CLP/CLP/GnRH (n = 64)were treated as those in the GnRH-CLP/CLP group of Study 1 but received GnRH 32 h after the second CLP treatment and were inseminated 24 h after this. A further group of cows without ovarian cysts inseminated at natural estrus served as the Group Control (n = 64). Cows in the GnRH-CLP/CLP/ GnRH group showed a lower cystic persistence rate (10.9% < 46.9%; P < 0.0001); higher ovulation rate (79.7% > 17.2%; P < 0.0001); higher return to estrus rate (34.3% > 12.5%; P < 0.01) and higher pregnancy rate (28.1% > 3.1%; P < 0.01) than those in Ovsynch; and a similar pregnancy rate (28.1% versus 35.9%) to Control cows. These findings indicate that lactating cows with ovarian cysts can be successfully synchronized and time inseminated using a protocol that combines GnRH and CLP, starting treatment by simultaneously administering both products. This protocol also allows the insemination of cows showing estrus within the first week of treatment. Ovarian cysts were less responsive when treatment was started with GnRH alone.     

Effect of an acute ergotamine challenge on reproductive hormones in follicular phase heifers and progestin-treated cows

The objective of this research was to determine if ergotamine, an ergopeptine alkaloid isolated from Neotyphodium-infected grasses and associated with toxicoses in livestock, altered plasma concentrations of reproductive hormones in follicular phase heifers and in cows given a progestin implant. In Experiment 1, blood was sampled for 8h from four cycling heifers 2 days after synchronized luteolysis. Heifers were treated with ergotamine tartrate (19microg/kg) i.v. or saline vehicle in a simple cross-over design after 1h of pre-treatment blood sampling. Heifers received oxytocin (100USP units) i.v. 4h after ergotamine or saline treatment. Ergotamine reduced (P<0.01) prolactin concentrations from 1 to 4h post-treatment and increased (P<0.01) 13,14-dihydro-15-keto prostaglandin F2alpha (PGFM) concentrations from 2 to 5h post-treatment. A PGFM response to oxytocin was not detected. In Experiment 2, blood was sampled for 8h from six cycling cows 10 days after receiving a s.c. norgestomet implant. Cows were treated i.v. with ergotamine (20microg/kg) or saline in a simple cross-over design after 1h of pre-treatment blood sampling. Cows received gonadorelin (GnRH, 100microg) i.v. 1h after ergotamine or saline. Cows received oxytocin (100USP units) i.v. 4h after ergotamine or saline treatment. Ergotamine reduced (P<0.01) serum prolactin concentrations by 120min after treatment, with prolactin returning to pre-treatment concentrations by 200min after treatment. Saline-treated cows had lower (P<0.01) prolactin by 280min after treatment. Ergotamine-treated cows had higher (P<0.01) PGFM concentrations compared to saline-treated cows 120-240min after treatments, but the groups exhibited similar increases in PGFM after oxytocin. Plasma LH and FSH concentrations increased to peaks 100-120min after GnRH for both groups. However, the LH response to GnRH was greater (P<0.01) for ergotamine-treated cows. In summary, ergotamine lowered prolactin and elevated PGFM concentrations in follicular phase heifers and cows on norgestomet therapy. Ergotamine increased the LH response to exogenous GnRH in cows with norgestomet implants. These data highlight the potential of ergopeptine alkaloids to affect reproduction through altered endocrine function.