Modification of follicular dynamics by exogenous FSH and progesterone, and the induction of ovulation using hCG in postpartum beef cows

Follicular growth and ovulation in response to FSH, progesterone and hCG were evaluated in postpartum beef cows. In Experiment 1, on Day 21 post partum, cows received an injection of either saline (control; n = 6), FSH (200 mg; n = 6), or a PRID (n = 5) for 10 d. Both FSH and PRID prolonged maintenance of a dominant follicle (15.5 +/- 1.16 and 14.4 +/- 1.29 d, respectively, vs 8.4 +/- 1.22 d in control; P < 0.01), and increased the maximum diameter of the dominant follicle (14.0 +/- 0.91 and 16.4 +/- 1.01 mm, respectively, vs 10.9 +/- 0.95 mm in control; P < 0.05). The PRID-maintained dominant follicle ovulated in 60% of cows, followed by normal estrous cycles (vs 0% in control; P = 0.01), whereas the dominant follicle ovulated in 33% of FSH-treated cows (P = 0.08). The PRID regimen shortened the interval to first ovulation preceding a normal cycle and continued cyclicity (44 +/- 4.1 vs 60 +/- 4.4 d in control; P = 0.02). In Experiment 2, on Day 21 post partum, cows received either saline (control), saline + PRID, or FSH + PRID (n = 16/group). Sixty hours after PRID withdrawal, cows received either saline or hCG (1,500 IU, n = 8/treatment). The FSH + PRID regimen increased the number of large (> 10 mm in diameter) follicles (3.6 +/- 0.43 vs 1.9 +/- 0.39 in control; P = 0.005). Both PRID and FSH + PRID prolonged maintenance of the largest follicle (11.0 +/- 0.82 and 11.2 +/- 0.91 d, respectively, vs 8.7 +/- 0.81 d in control; P < 0.05). The PRID-maintained dominant follicle ovulated in 50% of cows, followed by normal estrous cycles. The FSH + PRID-maintained largest follicle had become atretic at PRID withdrawal and was anovulatory. The FSH + PRID + hCG regimen increased the incidence of ovulation preceding a cycle of normal duration and continued cyclicity (100 vs 50% in PRID; P = 0.03), and reduced the interval to first ovulation preceding a cycle of normal duration and continued cyclicity (38 +/- 6.5 vs 58 +/- 6.3 d in control; P = 0.04). The area under the progesterone curve during the induced cycle was reduced after (PRID +/- FSH) + hCG than after PRID +/- FSH (P = 0.002). These results indicate that PRID alone or with FSH/hCG has the potential to modify the dominant follicle and initiate cyclicity in postpartum beef cows.     

Superovulation in the cow using estradiol 17beta or GnRH in conjunction with FSH-P

A study was designed to evaluate the superovulatory response in the cow when either estradiol 17beta or gonadotrophin releasing hormone (GnRH) was used in a superovulatory regimen with follicle stimulating hormone (FSH-P). Fifty-four cyclic crossbred females were superovulated in replicates between Days 8 and 12 of their cycle. All animals were treated with 28 mg of FSH-P in twice-daily decreasing doses, each receiving 500 mug cloprostenol (PGF) 48 h after initiation of treatment. Group 1 served as FSH-P controls, Group 2 received FSH-P and 400 mug of estradiol 17beta 36 h after PGF, and Group 3 received FSH-P and 250 mug GnRH 48 h after PGF. Inseminations with one vial of frozen semen were done at 12, 24 and 36 h after the onset of estrus. Ova/embryos were collected nonsurgically at Day 7 postestrus. Numbers of corpora lutea (CL) were recorded after palpation per rectum and the recovered ova and embryos were evaluated. All females were bled for endocrine examination. There were no differences in ovarian response among these treatments. Mean total ova/embryos collected in Group 3 was significantly higher than in Groups 1 or 2 (P < 0.05); however, no significant difference existed between groups in the mean numbers of fertilized or transferable embryos. Similarly, no significant differences existed between groups for recovery rate, fertilization rate, or percentage of transferable embryos. Serum estradiol levels were significantly higher at the expected end of ovulation in Group 2, and this tended to be associated with higher fertilization and transferable embryo rates. Furthermore, a significant positive correlation was found to exist between CL numbers and each of the ova/embryo parameters and the estradiol levels at estrus.     

Effect of long-term treatment with recombinant bovine somatotropin and estradiol on hormone concentrations and ovulatory response of superovulated cattle

The objective was to assess effects of long-term treatment with recombinant bovine somatotropin (bST) and estradiol-17beta (E2) on the number of follicles that ovulated in response to FSH. Non-lactating Holstein and Jersey cows (Trial 1, n=27) and Angus cows and heifers (Trial 2, n=35) received two ear implants of E2 and biweekly injections of bST in a 2 x 2 arrangement of treatments. Estradiol implants were removed 74.6 +/- 1.1 d after insertion and 18.1 +/- 0.9 d after the last biweekly injection of bST. Cows were stimulated with FSH-P beginning 2 d after removal of E2 implants, and PGF2alpha (PGF) was given on the third day of FSH treatment. Ovaries were collected to determine the number of CL at 1 to 2 wk after treatment with PGF. In Trial 2 only, cattle were inseminated at estrus and embryos were collected 6 to 8 d later. Implants of E2 increased (P < 0.01) serum E2 8-fold initially and E2 was still elevated 5-fold at removal of implants. Injections of bST increased (P < 0.01) serum growth hormone (GH) 15-fold and insulin-like growth factor-I (IGF-I) 3-fold. In Trial 1, number of CL was increased by the combination of bST+E2 (P < 0.01). In Trial 2, E2 increased the number of CL (P < 0.05), and bST increased the number of total ova and transferable embryos (P < 0.01). We conclude that long-term treatment with bST and E2 may interact to enhance follicular development and ovulatory response to FSH.     

Studies of FSH-P induced follicular growth in cows

Because cow ovaries do not contain a dominant follicle before Day 3 of the estrous cycle, we hypothesized that gonadotropin treatment early in the estrous cycle would induce growth of multiple follicles and could be used to induce superovulation. In Experiment 1, when 16 cows were treated with FSH-P beginning on Day 2 of the estrous cycle and were slaughtered on Day 5, all cows responded to gonadotropin treatment by exhibiting a large number ( approximately 19) of estrogenactive follicles >/= 6 mm. In Experiment 2, in response to FSH-P treatment from Day 2 to Day 7, and fenprostalene treatment on Day 6, 11 of 15 cows exhibited estrus and had a mean ovulation rate of 23.7 +/- 1.5. In Experiment 3, an FSH-P treatment regimen identical to that used in Experiment 2 was administered to cows beginning either on Day 2 (Day-2 cows; n=14) or Day 10 (Day-10 cows; n=11) of the estrous cycle. Twelve of 14 Day-2 cows and all Day-10 cows exhibited estrus after fenprostalene treatment. Day-2 cows exhibited 34.3 +/- 7.0 ovulations, which was less (P < 0.05) than that exhibited by Day-10 cows (48.3 +/- 4.4). However, the proportion of embryos recovered per corpus luteum was about 2-fold greater (P < 0.05) for Day-2 cows than for Day-10 cows (0.49 +/- 0.08 vs 0.27 +/- 0.06). These data indicate that beginning gonadotropin treatment early in the estrous cycle, when a dominant follicle is not present, provides an efficacious means to induce growth of multiple follicles and superovulation in cows. However, when FSH was administered for 6 d, beginning the treatment on Day 10 also resulted in a consistent and efficacious response.     

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.     

Ovine estrus synchronization and superovulation using norgestomet B and follicle stimulating hormone-pituitary

Finewooled Rambouillet range ewes were used in a study to determine the feasibility of using a progesterone ear implant to synchronize estrus. In addition, some of the ewes were further treated with injections of follicle stimulating hormone-pituitary (FSH-P) to induce superovulation. Five days following estrus detection and breeding, FSH-P-treated ewes were laparotomized and surgically flushed to recover embryos. The number of corpora lutea (CL), the total number of embryos and the number of transferable embryos recovered were recorded along with the number and size of follicles present on both ovaries. Ewes synchronized as recipients were laparotomized for surgical transfer of embryos 5 d following estrus. The number of CL and follicles were recorded. Response to superovulation by FSH-P did not differ (P>0.05) between age groups of ewes when the number of CL present was counted. However, the total number of embryos flushed and good embryos was lower (P<0.05) among the oldest (7 yr) ewes. The number of follicles present showed little variation between age groups. Recipient ewes (No FSH-P) were similar in the number of CL with 6-yr-old ewes, having fewer (P>0.05) CL, than 3-, 4- or 7-yr-old ewes. Only slight variation was boserved in the number of follicles in recipient ewes. Among donor ewes receiving FSH-P in addition to Synchro-Mate B, 71% were detected in estrus within 48 h of implant removal vs 55% of the recipients.     

A dominant follicle does not affect follicular recruitment by superovulatory doses of FSH in cattle but can inhibit ovulation

It has been suggested that superovulation in cattle is impaired if FSH injections are initiated in the presence of a dominant follicle, but the results of experiments to test this hypothesis have been contradictory. However, previous experiments were conducted during mid-cycle, when the absence or presence of a dominant follicle is difficult to assess. We took a different approach by comparing the effects of initiating superovulatory injections of FSH (11 equal doses of FSH-P, every 12 h) on Day 1 of the bovine estrous cycle, when a dominant follicle clearly is not present, vs initiation on Day 6, when a dominant follicle clearly is present and actively growing (n = 17 heifers in a "crossover" design). In 8 17 heifers initiation of FSH injections in the presence of a dominant follicle (Day 6 group) caused ovulation of the dominant follicle within 1 to 2 days and formation of a smaller than normal CL. These animals had higher than normal concentrations of plasma progesterone around the time of expected estrus (P < 0.05) and failed to exhibit estrus. Although the mean number and diameter of the follicles recruited in response to FSH injections in heifers that ovulated the dominant follicle prematurely were not different from the other heifers in the Day 6 group, no ovulations were observed, and no embryos or ova were recovered 6 d after insemination. Conversely, when FSH injections were initiated on Day 1 in these 8 heifers, they exhibited estrus, and their plasma progesterone around the time of estrus, mean ovulation rate, and number of total and transferable embryos recovered did not differ from the responses observed in the remaining 9 heifers treated either on Day 1 or on Day 6. Taken together, these results indicate that a dominant follicle does not affect the ability of smaller follicles to be recruited in response to exogenous FSH, but may impair their ovulation. These findings provide an explanation for previous reports of decreased superovulatory responses during times of the cycle when a dominant follicle would be expected to be present.     

Effect of dominant follicle removal before superstimulation on follicular growth, ovulation and embryo production in Holstein cows

This study was to investigate whether removing the dominant follicle 48 h before superstimulation influences follicular growth, ovulation and embryo production in Holstein cows. After synchronization, ovaries were scanned to assess the presence of a dominant follicle by ultrasonography with a real-time linear scanning ultrasound system on Days 4, 6 and 8 of the estrus cycle (Day 0 = day of estrus). Twenty-six Holstein cows with a dominant follicle were divided into 2 groups in which the dominant follicle was either removed (DFR group, n=13) by ultrasound-guided follicular aspiration or left intact (control group, n=13) on Day 8 of the estrus cycle. Superovulation treatment was initiated on Day 10. All donors were superovulated with injections of porcine FSH (Folltropin) twice daily with constant doses (total: 400 mg) over 4 d. On the 6th and 7th injections of Folltropin, 30 mg and 15 mg of PGF2alpha (Lutalyse) were given. Donors were inseminated twice at 12 h and 24 h after the onset of estrus. Embryos were recovered on Day 6 or 7 after AI. During superstimulation, the number of follicles 2 to 5 mm (small), 6 to 9 mm (medium) and > or = 10 mm (large) was determined by ultrasonography on a daily basis. At embryo recovery, the number of corpora lutea (CL) was also determined by ultrasonography and blood samples were collected for analysis of progesterone concentration. Follicular growth during superstimulation was earlier in the DFR group than in the control group. The number of medium and large follicles was greater (P < 0.01) in the DFR group than in the control group on Days 1 to 2 and Days 3 to 4 of superstimulation, respectively. The numbers of CL (9.6+/-1.1 vs 6.1+/-0.9) and progesterone concentration (30.9+/-5.4 vs 18.6+/-3.5 ng/mL) were greater (P < 0.05) in the DFR group than in the control group, respectively. The numbers of total ova (7.7+/-1.3 vs 3.9+/-1.0) and transferable embryos (4.6+/-0.9 vs 2.3+/-0.8) were also greater (P < 0.05) in the DFR group than in the control group, respectively. It is concluded that the removal of the dominant follicle 48 h before superstimulation promoted follicular growth, and increased ovulation and embryo production in Holstein cows.     

Rapid milk progesterone assay as a tool for the selection of potential donor cows prior to superovulation

This study investigated the accuracy of a commercially available rapid milk progesterone (P(4)) assay (RMPA) and its usefulness for the screening of potential donor cows prior to superovulatory treatment. Superovulation was induced in 90 lactating Holstein-Friesian crossbred dairy cows with twice daily injections over a 4-day period for a total of 40 mg follicle stimulating hormone (FSH-P), starting 9 to 13 d post estrus. Prior to induction of superovulation, a milk sample was collected and assayed for a P(4) level using the RMPA. The test determines P(4) by a simple visual color inspection of the respective sample, which is compared to a standard containing 10.5 ng/ml of P(4). All animals were divided into six groups according to the color intensity of their sample; three groups had a lower level, one group had an equal level and two groups had a higher P(4) level than the standard. Results of the semiquantitative RMPA were verified by a quantitative enzymeimmunoassay (EIA). Samples evaluated as equivalent to the standard had a mean P(4) level of 10.7 +/- 1.3 ng/ml (x +/- SEM). In total, P(4) levels differed (P<0.05) among groups, except in those with lower P(4) concentrations (1.1 +/- 0.0; 1.0 +/- 0.0; 3.7 +/- 1.5; 10.7 +/- 1.3; 13.8 +/- 1.3; 19.0 +/- 1.5 ng/ml, respectively). The correlation between RMPA-groups and EIA P(4) levels was 0.69 (P<0.001). Donors classified as having less P(4) than the standard yielded fewer corpora lutea (CL) (P<0.005), ova and embryos (P<0.05), and transferable embryos (P<0.05) compared with donors having similar or higher P(4) levels (3.4 +/- 1.0 vs 10.8 +/- 0.7 CL; 1.7 +/- 0.8 vs 6.2 +/- 0.9 ova and embryos; 1.2 +/- 0.7 vs 2.8 +/- 0.4 transferable embryos). Our results indicate that RMPA determines milk P(4) levels with sufficient accuracy and is a simple and useful tool for the screening of potential donor cows.     

Lengthening the superstimulatory treatment protocol increases ovarian response and number of transferable embryos in beef cows

This study determined if lengthening the superstimulation protocol from 4 to 7 days would result in an increase in the superovulatory response with no adverse effects on oocyte/embryo competence in beef cows. Follicular ablation was performed, a progesterone-releasing intravaginal device (PRID) was inserted, and cows were assigned to one of two treatment groups 5 to 8 days after ovulation: Control (4 days of follicle stimulating hormone (FSH)) or Long (7 days of FSH; n = 12 per group). The FSH treatments were initiated 1.5 days later (Day 0). A dose of 400 mg NIH-FSH-P1 (Folltropin-V) was distributed equally over 8 (Control) or 14 (Long) im injections at 12-h intervals. Prostaglandin F2α (PGF) was administered twice, 12 h apart, on Day 2 (Control) or Day 5 (Long), and PRID were removed 12 h after the second PGF. Both groups were given 25 mg pLH (lutropin-V) im 24 h after PRID removal and AI was done 12 and 24 h later. Ova/embryos were collected 7 days after the pLH injection. The mean (± SEM) number of ≥ 9 mm follicles at the time of first AI did not differ (P = 0.24) between groups, but more ovulations (30.9 ± 3.9 vs. 18.3 ± 2.9, P = 0.01) and CL (27.2 ± 2.1 vs. 20.8 ± 2.2, P = 0.04) occurred in the Long group. A higher proportion of the ≥ 9 mm follicles ovulated between 12 and 36 h after pLH in the Long group (93 vs. 69%; P = 0.001). Although numerically higher in the Long group, mean numbers of total ova/embryos, fertilized ova, transferable or freezable embryos did not differ. In conclusion, a lengthened superstimulatory treatment protocol resulted in more follicles acquiring the capacity to ovulate with an increased number of ovulations, and without a decrease in oocyte/embryo competence.     

Superovulatory response of dairy cattle (Bos taurus ) in a tropical environment

Dairy (Bos taurus) heifers and cows (n = 40) in a tropical environment were treated during mid-luteal phase using either SUPER-OV(R) or OVAGEN to induce superovulatory response after synchronization of the superovulatory estrus with a synthetic progestagen and cloprostenol (PG). Estrous cattle were inseminated twice using frozen-thawed semen, and embryos were recovered nonsurgically, on-farm, 7 d later. Between initiation of gonadotrophin treatment and recovery of embryos, 4 blood samples per animal were collected from 26 animals for determination of plasma progesterone (P4) concentration. Two (5%), 28 (70%) and 10 (22%) of the animals were observed in estrus 1.5, 2 and 2.5 to 3 d after PG, respectively. There was no difference (P = 0.7) in the number of palpable CL between animals treated with SUPER-OV (7.6 +/- 1.0; n = 18) and those treated with OVAGEN (7.9 +/- 1.1; n = 22). There was also no significant difference (P > 0.05) between Jersey vs Ayrshire breeds or heifers vs cows in the ovarian response as estimated by the number of palpable CL. However, a higher proportion of Ayrshire cattle and donors treated with OVAGEN yielded a higher total number and viable/transferable embryos than Jersey and SUPER-OV-treated cattle. There was a significant (P < 0.05) correlation between the number of CL and total number of embryos (r = 0.65); the number of transferable embryos was also significantly related to the total number of embryos per recovery (r = 0.85; P < 0.05). For 15 animals with normal P4 profiles, the mean (+/-SEM) plasma P4 concentration was 14.4 +/- 0.8, 0.5 +/- 0.2, 5.4 +/- 1.1 and 39.4 +/- 3.0 nmol L at initiation of gonadotrophin treatment, superovulatory estrus and Days 3 and 7, respectively. The mean (+/-SEM) interval between a PG injection given after embryo recovery and the induced estrus was 7.1 +/- 0.7 d (range 3 to 14 d) and the length of the superovulatory cycle was 24.1 +/- 3.2 d (range 12 to 35 d).     

Ovarian response to gonadotropin treatment initiated relative to wave emergence in ultrasonographically monitored ewes

Follicular recruitment and luteal response to superovulatory treatment initiated relative to the status of the first wave of the ovine estrous cycle (Wave 1) were studied. All ewes (n = 25) received an intravaginal progestagen sponge to synchronize estrous cycles, and ewes were monitored daily by transrectal ultrasonography. Multiple-dose FSH treatment (total dose = 100 mg NIH-FSH-P1) was initiated on the day of ovulation (Day 0 group) in 16 ewes. In the remaining 9 ewes, FSH treatment was started 3 d after emergence of the largest follicle of Wave 1 (Day 3 group). Ewes received PGF(2alpha) with the last 2 FSH treatments to induce luteolysis. Daily blood samples were taken to determine progesterone profiles and to evaluate the luteal response subsequent to superovulation. The ovulation rate was determined by ultrasonography and correlated with direct observation of the ovaries during laparotomy 5 to 6 d after superovulatory estrus when the uterus was flushed to collect embryos. Results confirmed that follicular recruitment was suppressed by the presence of a large, growing follicle. In the Day 0 and Day 3 groups, respectively, mean numbers (+/- SEM) of large follicles (>/= 4 mm) recruited were 6.4 +/- 0.6 and 2.7 +/- 0.7 (P < 0.01) at 48 h after the onset of treatment, and 6.7 +/- 0.5 and 5.1 +/- 0.6 (P = 0.08) at 72 h after the onset of treatment. Ovulation rates were 5.6 +/- 0.8 and 3.3 +/- 0.8 in the respective groups (P < 0.05). The number of transferable embryos was 1.8 +/- 0.5 and 0.3 +/- 0.2 in the respective groups (P < 0.05). Short luteal phases (相似文献   

Superovulation of beef heifers with Folltropin: A new FSH preparation containing reduced LH activity

The optimum superovulatory dose of Folltropin was determined and compared with a standard 28 mg dose of FSH-P in beef heifers. In Experiment 1, mean numbers of corpora lutea (CL) did not differ among the groups treated with 10, 20, 30 or 40 mg Folltropin or FSH-P, and the mean CL number was reduced (P<0.05) only in the 5 mg Folltropin group. Mean numbers of ova/embryos recovered, fertilized and transferable were greater (P<0.05) for the 10, 20 and 30 mg Folltropin groups than for the 5 mg group. The 40 mg Folltropin group and the FSH-P group were intermediate. The percentage of fertilized and transferable embryos did not differ over the dosages used in this experiment. In Experiment 2, mean numbers of CL were greater for the 9, 18 and 36 mg Folltropin groups than for the 4.5 mg group, with the 9 mg group being lower than the 36 mg group (P<0.05). The 18 mg group was intermediate and did not differ. Mean numbers of ova/embryos recovered and fertilized ova were greater for the 9, 18 and 36 mg groups (P<0.05) than for the 4.5 mg group. The percent of fertilized and mean number and percentage of transferable embryos did not differ among treatments. We conclude that Folltropin may be a satisfactory superovulatory replacement for FSH-P and that a dose of 18 to 20 mg Folltropin may be within the optimum superovulatory dosage range for beef heifers. Dosages of Folltropin of more than twice the optimum did not result in deterioration of ova/embryo quality.     

Follicular development and superovulation response in cows administered multiple FSH injections early in the estrous cycle

To determine whether follicular development, superovulation and embryo production were affected by the absence or presence of a dominant follicle, cows were administered injections of FSH twice daily in the early (Days 2 to 6, estrus = Day 0) or middle stage (beginning on Day 10 or 11) of the estrous cycle. Treatment with FSH early in the cycle stimulated follicular development in 83 to 100% of all cows from 4 groups evaluated at different times after PGF2alpha treatment on Days 6 and 7. However, the proportion of cows with > 2 ovulations varied from 31 to 62.5%, indicating that induction of follicular development may occur in the absence of superovulation. When compared with cows treated in the middle of the cycle, no differences were observed in the proportion of cows with > 2 ovulations (31 vs 20%), ovulation rate. (26.0 +/- 6.3 vs 49.6 +/- 25.8), production of ova/embryos (13.3 +/- 3.2 vs 14.4 +/- 3.4), or the number of transferable embryos (8.0 +/- 3.6 vs 5.4 +/- 1.5; early vs middle, respectively). The proportion of the total number of embryos collected that were suitable for transfer was greater (P<0.01) in cows treated early in the cycle (60%) than at midcycle (37.5%). The diameter of the largest follicle observed by ultra-sound prior to initiation of FSH treatment in the early stage of the cycle (10.0 +/- 2.0 mm) was smaller (P<0.05) than at midcyle (16.8 +/- 1.3 mm). These results demonstrate that superinduction of follicular development is highly consistent after FSH treatment at Days 2 to 6 of the cycle and that superovulation and embryo production are not less variable than when FSH is administered during the middle of the cycle. However, superovulation in the early stage of the cycle may increase the proportion of embryos suitable for transfer.     

Superovulatory response following transvaginal follicle ablation in cattle

A study was designed to compare superovulatory responses in cattle when gonadotropin treatment followed 1 of 3 different treatments to synchronize follicular wave emergence. Animals at unknown stages of the estrous cycle were randomly assigned to 3 groups: ablation of the 2 largest follicles per pair of ovaries (n = 21); ablation of all follicles > or = 5 mm (n = 19); or intramuscular administration of 5 mg estradiol-17beta plus 100 mg progesterone (n = 23). All animals were given a CIDR-B intravaginally at the time of the respective treatments. Gonadotropin treatment, initiated 1 d after follicle ablation or 4 d after estradiol plus progesterone treatment, in the respective groups, consisted of 200 mg of pFSH divided in decreasing doses twice daily over 4 d. Cloprostenol (500 microg) was given at 48 and 60 h after the first pFSH treatment; CIDR-B devices were removed at the time of the second cloprostenol treatment. Ovarian ultrasonography was done on the days of CIDR-B insertion, first gonadotropin treatment, and at 36 and 72 h after CIDR-B removal. Cattle were inseminated twice, at 60 and 72 h after the first injection of cloprostenol. Ovarian and ova/embryo data were collected at slaughter 5, 6 or 7 d after insemination. No differences were detected among groups in the number of follicles > or = 8 mm at the time of first insemination (20.4 +/- 1.7 vs 16.6 +/- 2.0 vs 19.9 +/- 2.3; P > 0.05). At slaughter, no differences were detected among groups in the numbers of CL (23.3 +/- 1.9 vs 17.9 +/- 1.9 vs 20.1 +/- 2.6; P < 0.05), unovulated follicles > or = 8 mm (2.2 +/- 0.5 vs 2.1 +/- 0.3 vs 3.7 +/- 0.9; P < 0.05), ova/embryos (11.0 +/- 1.4 vs 12.2 +/- 1.3 vs 8.5 +/- 1.3; P < 0.05), fertilized ova (9.4 +/- 1.3 vs 10.1 +/- 1.2 vs 7.5 +/- 1.1; P < 0.05) or transferable embryos (8.2 +/- 1.2 vs 8.4 +/- 1.3 vs 6.5 +/- 0.9; P < 0.05). Variation in the numbers of CL (P = 0.1) and unovulated follicles > or = 8 mm (P < 0.01) was lower in the ablation groups than in the steroid-treated group. Results suggest that follicle ablation is as effective as estradiol plus progesterone in synchronizing follicular wave emergence for superstimulation in cattle, and that ablation of the 2 largest follicles is as efficacious as ablating all follicles > or = 5 mm.     

Evaluation of the incorporation of GnRH into a superovulatory regimen for Zebu cattle

The objective of this study was to evaluate the utilization of gonadotropin releasing hormone (GnRH) as part of a superovulatory regimen for Zebu cattle. Forty Zebu cows were superovulated with 40 mg of follicle stimulating hormone-pituitary (FSH-P) divided in eight fractions of 5 mg injected at 12-h intervals. Luteolysis was induced with 15 mg of luprostiol injected at 48 h after the first injection of FSH-P. Half of the animals were injected with 200 ug of GnRH 3 h after the onset of standing estrus. The other 20 animals were not injected with GnRH. All the cows were inseminated three times at 12-h intervals, starting at the time of standing estrus. Embryos were recovered nonsurgically 7 d after the last insemination. Palpation per rectum performed immediately after collection of the embryos did not show differences in the number of corpora lutea between groups (P > 0.05). Likewise, there were no significant differences between treatments with respect to the total number of embryos plus ova, total number of embryos, or the number of transferable embryos recovered (P>0.05). The number of blastocysts, morulae, degenerated morulae and unfertilized ova was similar for the two groups. It is concluded that the incorporation of GnRH into a part of the superovulatory treatment for Zebu cattle does not improve the results of such treatment.     

Ultrasound-monitored ovarian responses in normal and superovulated cattle given exogenous progesterone at different stages of the oestrous cycle

In two experiments with female cattle, responses to synchronisation and superovulation were monitored by transrectal ultrasonography and embryo recovery. Each experiment had both a synchronisation phase to establish a reference oestrus and a superovulatory phase with the oestrous cycle controlled by exogenous progesterone commencing at two specific times. The reference oestrus was controlled using a progesterone releasing intravaginal device (PRID) applied for 12 days with prostaglandin F_2α given 1 day before removal. Experiment 1 had two treatments which differed by the absence (A) or presence (P) of a 10mg oestradiol benzoate capsule on the PRID, while in Experiment 2 all animals were on treatment P. In the superovulatory phase of both experiments treatment P commenced on Day 7 (PRID 7 treatment) or Day 14 (PRID 14 treatment) of the oestrous cycle (oestrus designated Day 0). Superovulation, using equine chorionic gonadotrophin in Experiment 1 and oFSH in Experiment 2, commenced 3 days before PRID removal. Treatment P caused rapid regression of the dominant follicle and corpus luteum (CL) irrespective of when treatment commenced. A second wave of follicular growth was detected after 6–8 days and the dominant follicle grew at 1.1 mm day⁻¹ in the 7 days before oestrus. In contrast, in treatment A of Experiment 1, the dominant follicle either grew slowly and eventually ovulated for cows in the mid-luteal phase, or the dominant follicle regressed and a second wave follicle ovulated if cows were early luteal at PRID insertion. In the superovulatory phase of both experiments the dominant follicle of PRID 7 animals increased in size and then regressed, but in PRID 14 cows, the dominant follicle was regressing before PRID insertion. During superovulation, the number of 7–10 mm follicles was significantly (P<0.001) greater in PRID 7 animals in Experiment 2. In both experiments, half the animals on the PRID 14 treatment maintained a large follicle during the superovulatory phase in contrast to the even sized follicles in animals on PRID 7 treatment. In Experiment 1, the number of grade 1 embryos recovered was significantly (P<0.05) higher for PRID 7 than PRID 14 treatments. In Experiment 2, there were significant differences (P<0.001) in the number of corpora lutea, total ova plus embryos and grade 1 embryos in favour of PRID 7 animals following superovulation. We conclude that the initiation of control of the oestrous cycle with a PRID and subsequent superovulating regime should take account of normal follicular wave status for effective superstimulation and production of viable embryos, and that ultrasonography may usefully be applied to the process.     

Effects of once- versus twice-weekly transvaginal follicular aspiration on bovine oocyte recovery and embryo development

Ultrasound-guided transvaginal follicular aspiration combined with in vitro maturation/in vitro fertilization (IVM/IVF) and culture was used to obtain bovine preimplantation stage embryos. Evaluated were the effects of aspiration frequency on oocyte recovery and embryo development following IVM/IVF. In Experiment 1, transvaginal follicular aspiration was performed once (n=5) or twice (n=5) weekly in multiparous Angus cows with the aid of a transvaginal sector transducer (5-MHz). In Experiment 2, aspiration was performed on Angus cows once weekly (n=6), twice weekly (n=4), or twice weekly after treatment with FSH (15 mg; n=4). Follicles (>2 mm) were punctured using a 55-cm needle (17g), and oocytes were aspirated through the needle and silastic tubing (2 m) by vacuum suction (75 mmHg). The oocytes were examined for morphology and were in vitro matured and fertilized. Following IVF, all ova were co-cultured in vitro for 7 d on Buffalo Rat liver cells. Oocyte recovery rates per asp?ration session in Experiment 1 were not different between groups aspirated once or twice weekly (6.8+/-2.0 vs 6.3+/-1.1 oocytes/session; x+/-SEM) or in Experiment 2 between groups aspirated once, twice, or twice plus FSH treatment (7.7+/-1.8 vs 9.5+/-1.1 vs 6.2+/-1.1; P>0.10). In vitro development to the blastocyst stage was not different between the once, twice or twice-weekly aspiration plus FSH treatments or control oocytes obtained from cows at slaughter (23.1 vs 26.1 vs 18.0 vs 27.9%; P>0.10). Oocytes from the twice-weekly and twice-weekly plus FSH aspiration groups generated a higher percentage of Grade-1 quality embryos than the once-weekly group (P<0.05). In commercial bovine oocyte aspiration, more transferable embryos can be generated from twice-weekly aspirations than from once-weekly aspiration.     

Superovulatory and endocrine responses in heifers treated with FSH-P at different stages of the estrous cycle

Forty-two Holstein heifers were superovulated with FSH-P (total dose, 30 mg) and cloprostenol. Treatment was initiated on Day 3 (Group D3, n = 11), Day 6 (Group D6, n = 11), Day 9 (Group D9, n = 10) or Day 12 (Group D12, n = 10) of the estrous cycle. Heifers were bled daily for serum progesterone and estradiol-17beta determinations and every 6 h for a 48-h duration at the expected time of estrus for luteinizing hormone (LH) assay. Ova and embryos were flushed from the reproductive tracts and the number of corpora lutea (CL) were recorded after slaughter on Day 7 post-estrus. Mean (+/- SEM) numbers of observed CL were higher (P < 0.05) in Group D9 (33.3 +/- 4.8) than in Group D3 (15.3 +/- 3.8), with Group D6 (17.0 +/- 2.9) and Group D12 (23.9 +/- 7.3) being intermediate. Similarly, mean (+/- SEM) numbers of fertilized embryos were highest (P < 0.05) in Group D9 (13.3 +/- 2.2). There was also a nonsignificant trend for the number of transferable embryos to be greatest in Group D9. Neither serum progesterone concentrations 3 d after the LH peak nor peak serum estradiol 17beta concentrations differed among groups, but both were significantly correlated with numbers of observed CL and total ova and embryos.     

Superovulatory response of Sistani cattle to three different doses of FSH during winter and summer

Objective of the present study was to investigate the effect of season and dose of FSH on superovulatory responses in Iranian Bos indicus beef cattle (Sistani). Cyclic cows, in summer (n=16) and winter (n=16), were assigned randomly to three dose-treatment groups of 120 (n=10), 160 (n=12) and 200 (n=10) total mg of Folltropin-V with injections given twice daily for 4 days in decreasing doses. Estrous cycles were synchronized with two prostaglandin F2alpha injections given 14 days apart. From day 5 after the ensuing cycle, daily ovarian ultrasonography was conducted to determine emergence of the second follicular wave at which time superovulation was initiated. Relative humidity, environmental and rectal temperatures were measured at 08:00, 14:00 and 20:00 h for the 3 days before and 2 days after the estrus of superovulation. Non-surgical embryo recovery was performed on day 7 after estrus. The effects of season, dose, time of estrous expression and all two-way interactions were evaluated on superovulatory responses: total numbers of CL, unovulated follicles (10 mm), ova/embryo, transferable and non-transferable embryos. Season (summer or winter), doses of Folltropin-V (120, 160 or 200 mg NIH) and time of estrous expression (08:00, 14:00 or 20:00 h) did not affect the number of transferable embryos (3.1+/-0.58). When superovulatory estrus was detected at 08:00, a FSH dose effect was detected with the greatest numbers of CL (12.2+/-0.87) and total ova/embryos (12.2+/-1.46) occurring with 200 mg FSH (dosextime of estrous expression; P<0.01).