Preovulatory LH profiles of superovulated cows and progesterone concentrations at embryo recovery

Forty-two Holstein cows were randomly assigned to three superovulatory treatment groups of 14 cows each. Cows in Group I received follicle stimulating hormone (FSH; 50 mg i.m.); those in Group II received FSH (50. mg i.m.) along with GnRH (250 ug in 2 % carboxymethylcellulose s.c.) on the day of estrus; and cows in Group III were infused FSH (49 mg) via osmotic pump implants. FSH was administered over a 5-d period for cows in Groups I and II (twice daily in declining doses). Cows in Group III received FSH over a 7-d period (constantly at a rate of 7 mg/day). All cows received 25 mg PGF(2)alpha (prostaglandin F(2)alpha) 48 hours after initiation of the FSH treatment. Blood samples were collected from seven cows from each group at 2 hour intervals on the fifth day of superovulation for serum luteinizing hormone (LH) concentration analysis by radioimmunoassay, and blood samples were collected from all cows on the day of embryo recovery for plasma progesterone determination. The LH profile was not altered (P>0.05) by either GnRH administration or by the constant infusion of FSH as compared to FSH treatment alone. Plasma progesterone concentrations were highly correlated with the number of corpora lutea (CL) palpated (r=0.92; P<0.01) and with the number of ova and/or embryos recovered (r=0.88; P<0.01). The accuracy of predicting the number of recoverable ova and/or embryos by the concentration of plasma progesterone was 86%.     

Effects of GnRH treatment on superovulatory responses of dairy cows

Twenty-eight Holstein cows were randomly divided into two groups. Group received 50 mg of FSH-P intramuscularly in declining doses for five days. Cows in group II received the same treatment as those in Group I but were also administered 250 ug of GnRH on the day of expected estrus. Neither the mean number of corpora lutea palpated nor the mean number of embryos recovered nonsurgically was different (P0.05) between treatments. However, administration of GnRH resulted in a higher fertilization rate and recovery of more developing embryos.     

Effect of exogenous FSH on estrus, ovulation and endogenous hormone release in dairy cows

Fifteen lactating Holstein cows were randomly allotted to receive either 0 mg (group 0), 32 mg (group 1) or 50 mg (group 2) porcine follicle stimulating hormone (FSH-P) injected in 10 fractions at 12 hr intervals beginning on day 9 of the estrous cycle. All cows received 25 mg prostaglandin (PG) on day 11. Jugular blood samples were collected from cows in all groups at 6 hr intervals beginning on day 7 and continuing through expression of estrus. Mean duration to occurrence of estrus and preovulatory LH surge after PG injection was reduced (P<.05) by injection of FSH-P. Mean number of ovulations increased (P<.05) progressively with increased dose of FSH-P. Mean peripheral progesterone declined more uniformly in FSH-P treated cows after PG and increased earlier (P<.05) after estrus in group 2 cows compared to group 0 and 1 cows. Mean plasma estradiol-17beta elevated (P<.05) after PG injection in both FSH-P-treated groups compared to group 0 cows. Both LH and FSH increased (P<.05) for 36 hr after initiation of FSH-P injection in groups 1 and 2, then declined until after PG injection. Peak LH and FSH occurred more uniformly following PG in treated cows. Results indicate that FSH-P increased endogenous gonadotropin release, estradiol-17beta, ovulation rate and reduced duration to estrus and preovulatory gonadotropin release after PG. Injection of 50 mg FSH-P increased plasma estradiol-17beta and ovulation rate compared to injection of 32 mg FSH-P.     

Endocrine and superovulatory responses in heifers pretreated with FSH or bovine follicular fluid

This study examined the effects of altered serum FSH concentration on subsequent ovarian response to superovulation. Synchronized heifers were assigned randomly on Day 1 of the cycle (estrus = Day 0) to three pretreatment groups that consisted of 6-d of saline (7ml, s.c., b.i.d.; Group I), FSH-P (0.5 mg, i.m., b.i.d.; Group II) or charcoal-extracted bovine follicular fluid (BFF; 7 ml, s.c., b.i.d.; Group III) injections. Superovulation was initiated on Day 7 and consisted of FSH-P in decreasing dosages over 4 d (4,3,2,1 mg; i.m., b.i.d.), with cloprostenol (500 mug) on the morning of the third day. A second replicate with 14 heifers was conducted using the same protocol but twice the pretreatment dosage of FSH-P (1 mg) and BFF (14 ml). Endogenous plasma FSH decreased during BFF and FSH-P pretreatments compared to controls (P < 0.02). Endogenous FSH concentrations in both primed groups (II and III) were similar to control values (Group I) 12 h after the start of superovulation. Basal LH concentrations were not different between pretreatment groups. The interval from cloprostenol treatment to the preovulatory LH surge in Group III was 21.3 and 23.9 h longer (P < 0.0001) than it was in Groups I and II. The postovulation progesterone rise was delayed in Group III. The number of corpora lutea (CL) was lowest in the BFF-primed group (4.2 +/- 0.8) compared with the FSH-primed (7.4 +/- 1.3) and the control (12.0 +/- 1.8; P < 0.003) groups. In the FSH-primed group (0.68 +/- 0.06 cm(3)), CL volumes were larger than in the control group (0.45 +/- 0.03 cm(3)), whereas in the BFF-primed group (0.27 +/- 0.02 cm(3)) CL volumes were smaller compared with the control group (P < 0.0001). Mean FSH concentrations for 48 h preceding superovulation and the number of CL per cow were positively correlated (r = 0.55; P < 0.004; n = 26). We concluded that both FSH-P and BFF pretreatments decreased the superovulatory response of heifers to FSH-P. The mechanism for this would appear to be associated with reduced endogenous FSH prior to the start of superovulation.     

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.     

Plasma concentrations of luteinizing hormone and progesterone during superovulation of dairy cows using follicle stimulating hormone or pregnant mare serum gonadotrophin

Eighteen lactating Holstein cows were randomly divided into three groups of equal size. Six cows were not superovulated; the remaining cows were superovulated using either FSH-P or PMSG beginning on Day 12 of the estrous cycle (day of ovulation = Day 0). Animals treated with FSH-P were injected intramuscularly (i.m.) with 4 mg FSH-P every 12 h for 5 d. PMSG was administered i.m. as a single injection of 2350 IU. Cloprostenol (PG, 500 ug) was injected i.m. 56 and 72 h after commencement of treatment and at the same time in the cycle of controls. All cows were inseminated 56, 68 and 80 h after the first PG injection. Blood samples (5 ml) were collected daily and every 15 min for a period of 9 h on Days -1, 0, 2, 8 and 10, with continuous blood sampling at 15-min intervals during Days 3 to 6. Ovulation rate was 27.7 +/- 8.22 in animals treated with PMSG, and 8.0 +/- 3.2 embryos per donor were recovered. In the FSH group, ovulation rate was 8.3 +/- 1.48 and 3.0 +/- 1.1 embryos per donor were recovered. Progesterone concentrations were similar in all three groups until the onset of the LH surge, when progesterone concentrations were greater (P<0.05) in animals of the PMSG group. After the preovulatory LH surge, concentrations of progesterone started increasing earlier (44 h) in cows treated with PMSG, followed by FSH-treated cows (76 h) and controls (99 h). The LH surge occurred earlier (P<0.05) in PMSG-treated cows (37 h after first PG treatment), than in animals treated with FSH-P (52 h) or controls (82 h). In animals treated with FSH-P, the magnitude of the preovulatory LH surge (24.2 +/- 1.02 ng/ml) was higher (P<0.05) than in the other two groups (PMSG = 17.1 +/- 2.04 ng/ml; control, 16.7 +/- 1.24 ng/ml). Superovulation with FSH-P or PMSG did not affect either mean basal LH concentration, frequency or amplitude of LH pulses during Days -1, 0, 2, 3, presurge periods, or Days 8 and 10 post-treatment. At ovariectomy, 8 d post-estrus, more follicles > 10 mm diam. were observed in the ovaries after treatment with PMSG (8.5 +/- 5.66) than after treatment with FSH-P (0.7 +/- 0.42) (P<0.05). Maximum concentrations of PMSG were measured 24 h after administration. Following this peak, PMSG levels declined with two slopes, with half-lives of 36 h and 370 h.     

Successful superovulation, nonsurgical collection and transfer of embryos from Brahman cows

Nonsurgical recoveries and transfers of embryos were performed at the McKellar Embryo Transplant Center from 122 superovulated Brahman cows. FSH-P (Armour) was used to superovulate all cows at dose levels ranging from 36 to 48 mg total FSH-P. Luteal regression was induced by use of 40 mg PGF(2(alpha)) in all 122 cows. Embryos were transferred into recipients 6, 7 or 8 days after observed estrus. Embryos were successfully collected from 82% of the FSH-P treated cows. The dose level of FSH-P affected numbers of embryos collected (P<.05). Numbers of embryos collected from cows superovulated with 36-38, 40, 42, 43, 44, 45, 46 and 47-48 mg FSH-P were 2.8 +/- 1.0, 6.8 +/- 1.1, 9.4 +/- 1.4, 10.0 +/- 2.7, 7.1 +/- 1.6, 6.8 +/- 2.0, 5.0 +/- 1.7 and 4.6 +/- 2.0 embryos, respectively. The dose level of FSH-P also affected numbers of embryos transferred (P<.10). Number of embryos transferred from cows superovulated with 36-38, 40, 42, 43, 44, 45, 46 and 47-48 mg FSH-P were 2.8 +/- 1.9, 5.2 +/- 0.9, 6.9 +/- 1.2, 6.7 +/- 2.1, 4.8 +/- 1.3, 5.1 +/- 1.4, 3.4 +/- 1.2 and 3.2 +/- 2.1 embryos, respectively. The developmental stage (D) of the embryo was also a factor in pregnancy rate of recipients (morula = 13.8%, blastocyst = 22.1% and expanded blastocyst = 29.9%; P<.005). The skill of the technician (T) transferring the embryo had a dramatic effect upon subsequent pregnancy rate of the recipients (T 1 = 46.0% vs T 2 = 22.6% pregnancy rate; P<.005). Pregnancy rate of recipients was also affected by the stage postestrus (S) at which the embryo was transferred (day 6 = 23.5%, day 7 = 25.5% and day 8 = 42.3% pregnancy rate; P<.05). Interactions were found between T x S, T x D, S x D and T x S x D (P<.05). These data indicate that use of 40, 42, or 43 mg total doses of FSH-P were quite effective in superovulating the Brahman cow. Recipients transferred on day 8 postestrus achieved higher pregnancy rates than recipients transferred on days 6 or 7 postestrus. Embryos transferred in the expanded blastocyst stage of development proved to yield the highest pregnancy rates in recipients.     

Serum testosterone concentration, efficiency of estrus detection and libido expression in androgenized beef cows

Twenty multiparous, cyclic, nonlactating beef cows were blocked by dominance rank and randomly and equally allotted to 1 of 4 treatment groups: an untreated control group, a synovex-treated group which received 8 Synovex-H implants with no additional hormones, a testosterone-treated group which received 500 mg, i.m. and 1500 mg, s.c. testosterone enanthate on Day 1 with additional 1000 mg, s.c. doses of testosterone enanthate every 14 d, and a synovex + testosterone-treated group which received 8 Synovex-H implants with 500 mg, i.m. and 1500 mg, s.c. testosterone enanthate on Day 1 only. Blood samples were collected via jugular venipuncture once a week beginning 3 wk prior to start of treatment. In addition, samples were collected just prior to treatment; once a day for 1 wk after initiation of treatment; and then twice a week until 225 d after treatment. Efficiency of estrus detection was assessed 22 d prior to start of treatment and every 14 d thereafter for 98 d, using estrus detection trials with synchronized females or modified libido tests. Scores for estrus detection trials included total mounts in 1 h and the percentage of estrous cows detected. Libido was scored on a scale of 0 through 6. All testosterone treatments raised plasma testosterone concentrations above control and pretreatment levels (testosterone and synovex + testosterone > synovex > control; all P < 0.05). Synovex-, testosterone- and synovex + testosterone-treated females performed more mounts in 1 h than the controls (18, 9, 6 and 1, respectively; all P < 0.05). All testosterone-treated cows mounted a higher number of estrous females than the controls (P < 0.05). Only synovex + testosterone- and testosterone-treated cows received libido scores above pretreatment and control values. However, libido of testosterone-treated cows decreased over time, while that of synovex + testosterone-treated females remained high until Day 98. Libido scores correlated positively with the number of mounts in 1 h and the percentage of estrous females detected (0.70 and 0.44, respectively), and the correlation coefficient for these two factors was 0.63. In conclusion, the synovex + testosterone treatment was most effective for producing estrus detector females and libido testing was useful for evaluating sexual activity in androgenized females.     

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.     

Superovulation of dairy cows with purified FSH supplemented with defined amounts of LH

This study investigated the effects of a purified follicle stimulating hormone (FSH) preparation supplemented with three different amounts of bovine luteinizing hormone (bLH) and a commercially available FSH with a high LH contamination on superovulatory response, plasma LH and milk progesterone levels in dairy cows. A total of 112 lactating Holstein-Friesian crossbred dairy cows were used for these experiments; the cows were randomly assigned to treatment groups consisting of purified porcine FSH (pFSH) supplemented with bLH. Group 1 was given 0.052 IU LH 40 mg armour units (AU) FSH (n = 6); Group 2 was given 0.069 IU LH (n = 32); Group 3 received 0.423 IU LH (n = 34); while Group 4 cows (n = 36) were superovulated with a commercially available FSH-P((R)). This compound appeared to contain 8.5 IU LH 40 mg AU FSH according to bioassay measurement. All animals received a total of 40 mg AU FSH at a constant dose twice daily over a 4-d period. Levels of milk progesterone and plasma LH were determined during the course of superovulatory treatment. The Group 1 treatment did not reveal multiple follicular growth, and no embryos were obtained. Superovulation of Group 3 cows resulted in significantly (P<0.05) more corpora lutea (CL; 12.6+/-1.1) and fertilized ova (5.1+/-1.3) compared with Groups 2 and 4 (10.1+/-0.9 and 2.6+/-0.6, 9.0+/-0.9 and 2.7+/-0.5, respectively). Due to a high percentage of degenerated embryos (33%) Group 3 yielded only one more transferable embryo than Groups 2 and 4. Among groups, LH levels differed in the period prior to induction of luteolysis and were similar thereafter. The progesterone pattern following FSH LH administration reflected the amount of LH supplementation. Milk progesterone levels on the day prior to embryo collection were correlated to the number of CLs and recovered embryos. It is concluded that under the conditions of our experiment superovulation with 0.423 IU LH 40 mg AU FSH may yield a significantly improved superovulatory response in dairy cows. It is further suggested that LH supplementation exerts its effects mainly on follicular and oocyte maturation during the period prior to luteolysis.     

Effects of cloprostenol, human chorionic gonadotropin and estradiol benzoate treatment on estrus synchronization in dairy cows

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

Improved embryo yield and condition of donor ovaries in cows after PMSG superovulation with monoclonal anti-PMSG administered shortly after the preovulatory LH peak

Nonlactating Dutch-Friesian cows were selected from a local slaughterhouse and synchronized with Syncro-Mate B. Cows with a normal progesterone pattern were treated with PMSG (3,000 I.U. i.m.) on Day 10 followed by PG (Prosolvin 22.5 mg) 48 h later. Blood samples were collected daily and at hourly intervals from 30 h after PG. Monoclonal anti-PMSG (Neutra-PMSG) was administered i.v. at 5.8 h after the LH peak in 16 cows; controls (n = 16) did not receive Neutra-PMSG. For comparison, 16 additional cows were superovulated with FSH-P in decreasing doses, twice a day (total 32 mg), starting at Day 10. All cows were inseminated at 10 h after the LH peak. Embryos were evaluated on Days 6 and 7 after flushing upon slaughter (recovery 87%). The number of corpora lutea and follicles on the donor ovaries were counted. No significant differences in the concentrations of progesterone and LH were observed between the three superovulation groups. Upon Neutra-PMSG, PMSG in blood was completely neutralized, it was decreased to < 0.5 ug/l at AI from 7.0 ug/l at the LH peak. The number of transferable embryos was significantly higher after Neutra-PMSG (9.1 per cow) than without Neutra-PMSG (5.3). or upon FSH-superovulation (4.6). The number of cysts on the ovaries of Neutra-PMSG-treated cows was reduced similarly to that after FSH-superovulation. Treatment with Neutra-PMSG shortly after the LH peak positively affects final follicular maturation in PMSG-superovulated cows and results in a nearly two-fold increase of transferable embryos.     

Effects of gonadotropin releasing hormone and prostaglandin F(2)alpha on the reproductive performance in postpartum cows

A study was conducted to determine whether treatment with gonadotropin releasing hormone (GnRH) in combination with prostaglandin F(2)alpha (PGF(2)alpha) could enhance ovarian activity and uterine involution in postpartum dairy cows to reduce the calving interval. Cows were randomly assigned to one of three treatment groups. Cows (n = 8) in Group 1 received 100 mug GnRH intramuscularly (i.m.) twice on Day 20 and Day 35 postpartum, and 25 mg PGF(2)alpha i.m. on Day 47 postpartum. Group 2 (n = 8) received a single i.m. injection of 100 mug GnRH on Day 25 postpartum and 25 mg PGF(2)alpha i.m. on Day 37 postpartum. The Control Group (n = 9) did not receive hormonal treatment. Palpation per rectum of the reproductive organs and serum progesterone (P) determination were performed twice a week to monitor ovarian activity and uterine involution. Postpartum interval to the first ovulation was short in treated groups (Group 1, 21.0 d; Group 2, 26.3 d) compared with Control Group (30.1 d, P < 0.05). Likewise, mean frequency of ovulation was increased in both treated groups compared with the Control Group (P < 0.05). Cows in treated groups required fewer days to complete uterine involution than in the Control Group. The mean interval to the first service, the conception rate at first service and the number of services per conception showed no significant differences among the three groups, but the mean days from calving to conception were shorter for the treated groups (78.7 d in Group 1; 83.3 d in Group 2) than (109.1 d, P < 0.05) for the Control Group. Our results suggest that combined treatment with GnRH and PGF(2)alpha may enhance ovarian activity in the postpartum cow, resulting in improved reproductive performance.     

Dose of FSH-P as a source of variation in embryo production from superovulated cows

Various superovulation treatments were evaluated retrospectively in a commercial embryo transfer program. When it appeared that embryo production was dependent on the dose of FSH-P, a dose response curve to FSH-P was developed and embryo production compared using several treatment regimes. There was a significant effect of dose of FSH-P on embryo production in superovulated cows. At doses in excess of 28 mg, embryo production declined from 5.9 transferable embryos per collection (28 mg) to 2.7 (60 mg). Total embryos collected declined from 14.9 to 6.8 and the percent transferable from 57% to 40%. There was no advantage in using a five-day treatment over a four-day treatment regimen or in using a level over a declining dose regimen. There was a large individual variation in cow response rendering decisions on treatment changes based on single records unreliable. The percentage of zero collections increased with dose rate. Adoption of a 28-mg dose rate in commercial donors resulted in the embryo production forecast by these studies.     

Endocrine, estrous and pregnancy response to varying dosages of Luprostiol in beef cows

Multiparous lactating beef cows were observed for estrus and randomly assigned to one of four Luprostiol (13, thia-PG-F(2)alpha analog) treatment groups receiving 3.8 (LI), 7.5 (LII), 15 (LIII) or 30 (LIV) mg Luprostiol, respectively, or to an untreated control group (C), or to a positive control group (E) receiving 500 mcg Estrumate. Cows received their respective treatments in a single dosage on Day 7, 8 or 9 of the estrous cycle (estrus = Day 0) and were artificially inseminated 12 h following the subsequent estrus. Blood samples were collected from all groups immediately prior to treatment and at 12-h intervals to 48 h post treatment and analyzed for progesterone (P(4)). Blood samples were collected at 3-h intervals from 24 to 72 h post treatment for animals in Group LIII and for 48 h (or observed estrus) starting on Day 19 of the estrous cycle for animals in Group C. These samples were analyzed for estradiol-17beta(E(2)), follicle stimulating hormone (FSH) and luteinizing hormone (LH). Treatment with Luprostiol at doses >/= 7.5 mg resulted in a synchronous estrous response during the first 5 d post treatment in 75 to 95% of cows treated. Luteal function, as evaluated by systemic P(4) concentration, paralleled results observed for estrous response. Treatment with a 15 or 30 mg dose of Luprostiol resulted in greater overall pregnancy rate at synchronized estrus. No biologically significant differences were found in blood levels of E(2), FSH or LH around the time of estrus between cows in Groups C and LIII. Results from these studies indicate treatment with Luprostiol at doses >/= 7.5 mg resulted in a synchronous estrus during the first 5 d after treatment. Pregnancy rates and endocrine changes were similar to those observed in control and Estrumate-treated cows.     

Effect of alfaprostol on postpartum reproductive efficiency in brahman cows and heifers

Brahman cows (n = 54) and heifers (n = 18) were randomly allotted by calving date, sex of calf and age to one of four treatment groups. Group 1 received no treatment (control), Group 2 received 5 mg alfaprostol (AP) i.m. on Day 21 postpartum, Group 3 received 5 mg AP i.m. on Day 32 postpartum and Group 4 received 5 mg AP i.m. on both Days 21 and 32 postpartum. Blood samples were collected via tail vessel puncture at 30 min-intervals for 8 h from half the animals in each group on Days 21 and 32 postpartum, with AP injection administered 2 h after sampling had begun. All cows were bled at weekly intervals. Samples were processed to yield serum and stored at -20 degrees C until assayed for luteinizing hormone (LH) or progesterone (P(4)). All cattle were maintained with epididymectomized marker bulls and were artificially inseminated (A.I.) at first estrus. Serum P(4) was below 1 ng/ml prior to AP treatment in all animals and did not differ (P > 0.10) between treatments. Alfaprostol treatment affected mean postpartum interval (from parturition to return to standing estrus and subsequent corpus luteum formation with serum progesterone concentrations > 1 ng/ml; P < 0.08). The control group (84.8 +/- 7.9 d) did not differ from Group 2 (86.3 +/- 11.1 d) or Group 3 (66.7 +/- 5.5 d) but did differ (P < 0.09) from Group 4 (65.1 +/- 6.4 d). Cattle injected on Day 32 had a shorter (P < 0.01) postpartum interval than those not receiving treatment on that day (65.9 +/- 4.2 vs 85.7 +/- 6.8 d). Pregnancy rate was affected (P < 0.05) by AP treatment. The control group (72.2%) did not differ (P > 0.10) from any group but, Group 2 (50.0%) was lower (P < 0.04) than Group 3 (83.3%) and (P < 0.02) Group 4 (88.9%). Cattle treated on Day 32 (Groups 3 and 4) had a higher (P < 0.02) pregnancy rate (86.1%) than those not treated on Day 32 (Groups 1 and 2; 61.1%). Serum LH was affected by day (P < 0.0003) and treatment by day (P < 0.07) but not by time (P > 0.10). Treatment Group 3 (P < 0.08) and Group 4 (P < 0.0003) mean LH concentrations differed between Days 21 and 32 postpartum. Cattle receiving AP treatment on Day 32 postpartum had a higher (P < 0.04) cumulative frequency of return to estrus by 100 days postpartum than nontreated cattle.     

Apparent pA2 value of naltrexone is not changed in rats following continuous exposure to morphine or naloxone.

Chronic opioid antagonist administration increases opioid binding sites and potentiates behavioral responses to morphine. Conversely, chronic opioid agonist administration attenuates behavioral responses to morphine, though this is not necessarily accompanied by a parallel loss of binding sites. We examined the possibility that the in vivo affinity of the mu receptors might be altered as a consequence of the continuous administration of either naloxone or morphine. Rats were implanted sc with naloxone- or morphine-filled osmotic pumps; control animals were implanted with sham pumps. One week later, 24 hr after removing the osmotic pumps, cumulative dose-response curves for fentanyl analgesia were generated in the presence of 0.0, 0.03, 0.1, or 0.3 mg/kg naltrexone, using a tail-flick procedure. The analgesic ED50 (with 95% C. L.) of fentanyl in sham implanted animals, following saline pretreatment was 0.027 mg/kg (0.019, 0.039). The potency of fentanyl was decreased in rats infused with morphine, ED50 = 0.051 mg/kg (0.028, 0.093), and increased in rats that received naloxone, ED50 = 0.018 mg/kg (0.015, 0.022). The mean apparent pA2 value for naltrexone (with 95% C.L.) in the control group was 7.7 (7.5, 7.9). No differences were detected in animals that had received either naloxone or morphine for 7 days, pA2 = 7.8 (7.5, 8.1) and 7.4 (7.3, 7.6), respectively. Our results indicate that there is no change in the apparent affinity of the mu-receptor following continuous exposure to either an opioid agonist or antagonist, at a time when the analgesic potency of the agonist is decreased or increased, respectively.     

Effect of gonadotropin-releasing hormone and prostaglandin F2α on reproduction in postpartum dairy cows

Thirty dairy cows serving as the treated group (Group A) were injected intramuscularly with 100 mcg gonadotropin-releasing hormone (GnRH) at 10 to 16 days postpartum followed by 25 mg prostaglandin F₂α (PGF₂α) 14 days later. Twenty-nine herdmate dairy cows (Group B) serving as controls were treated in a similar manner using saline injections rather than GnRH or PGF₂α treatments. Only cows without obvious uterine infection were assigned to the experimental groups, and any uterine pathology that developed during the treatment interval was treated accordingly following the experimental period. Internal genitalia were evaluated via rectal palpation prior to each injection. Blood samples were collected for progesterone analysis before each injection and at 30 hours following the PGF₂α or the second saline injection. Experimental animals were artificially inseminated at the first detected postpartum estrus starting 35 to 40 days following calving. Results indicated evidence of enhanced cyclicity when Group A cows were compared with those in Group B. However, there were no significant differences between the two groups for interval to first observed estrus, interval to first serive, first serive pregnancy rate, services per pregnancy and days open. Furthermore, no difference in the incidence of follicular or luteal cysts, incidence of repeat breeders or number of reproductive culls was observed. From observations in this study, the GnRH and PGF₂α treatment scheudule might not be economically beneficial in lactating dairy cows as long as reproductive tract abnormalities are promptly diagnosed and subsequently treated by the attending practitioner.     

Ovulation and follicular growth in gonadotropin-treated gilts followed by in vitro fertilization and development of their oocytes

We investigated whether porcine ovaries derived from FSH-pituitary (FSH-P) or hCG-treated animals can produce oocytes with better in vitro cytoplasmic maturation and in vitro embryonic development relative to those derived from saline-treated animals. The size of the follicle producing the oocyte was also studied. Each of 25 prepubertal gilts received 1 of 6 treatments by intramuscular injection: 1) saline (3 mL, once, n = 5); 2) FSH-P8-3 (8 mg, 3 times, with a 24-h interval, n = 4); 3) FSH-P16-3 (16 mg, 3 times, with a 24-h interval, n = 4); 4) FSH-P16-1-P4-2 (16 mg, once, 4 mg, twice, with a 24-h interval, n = 4); 5) FSH-P16-1 (16 mg, once, n = 4); or 6) hCG (100 IU, 3 times, with a 24-h interval, n = 4). The ovaries were removed by mid-ventral laparotomy 72 h after the first injection. The numbers of corpora hemorrhagica (CH) with each FSH-P treatment were similar (P > 0.05). However, compared with gilts treated with saline or hCG, those treated with FSH-P8-3 had a greater (P < 0.05) number of CH. Treatment with FSH-P8-3 or FSH-P16-3 induced significant growth of medium/large follicles (4 to 8 mm in diameter) compared with saline or FSH-P16-1. The same results were observed when FSH-P8-3 was compared with FSH-P16-P4-2 or hCG. After in vitro fertilization, the rates of male and female pronuclei in oocytes derived from medium/large follicles did not differ (P > 0.05) between treatments, but in oocytes derived from small follicles they were lower (P < 0.05) in saline-treated than in FSH-P16-1-P4-2-treated gilts. After 120 h in culture, the percentages of the inseminated oocytes from 1 to 3 mm or 4 to 8 mm follicles developing to > or = 2-cell did not differ (P > 0.05) between saline- and gonadotropin-treated gilts. However, a higher (P < 0.05) percentage of the inseminated oocytes from 4 to 8 mm follicles had developed to the morula stage or beyond, than those from the 1 to 3 mm follicles. In conclusion, administration of single or multiple doses of FSH-P induced ovulation, but only 8 or 16 mg FSH-P injected 3 times with 24-h intervals for 72 h induced growth of 4 to 8 mm follicles. The size of follicle from which the oocyte derived also had a significant effect on its development in vitro.     

Effects of gonadotropin treatment on ovarian follicle growth, oocyte quality and in vitro fertilization of oocytes in prepubertal gilts

This study was undertaken to compare the effects of FSH-pituitary (FSH-P), eCG, and a combination of gonadotropins containing 400 IU eCG and 200 IU hCG (PG 600) on the growth of large follicles, oocyte quality and in vitro fertilization (IVF) rate of in vitro matured (IVM) oocytes in prepubertal gilts. The ovaries were removed via midventral laparotomy 48 h (Experiment 1) or 72 h (Experiment 2) after the first injection. In Experiment 1, 30 gilts received 1 of 5 treatments: 1) saline (3 ml i.m., once, n = 6); 2) FSH-P8 (8 mg i.m., twice, with a 24-h interval, n = 6); 3) FSH-P16 (16 mg i.m., twice, with a 24-h interval, n = 6; 4) eCG (1000 IU i.m., once, n = 6); or 5) PG 600 (5 ml i.m., once, n = 6). Compared with saline, treatment with PG 600 or eCG induced significant (P < 0.05) growth of large follicles (> or = 6 mm). In Experiment 2, 16 gilts received 1 of 5 treatments: 1) saline (n = 4); 2) FSH-P8 (n = 4); 3) FSH-P16 (n = 4); 4) eCG (n = 4), or 5) PG 600 (n = 4). The same injection protocol as in Experiment 1 was used. Compared with treatment with FSH-P8 or FSH-P16, eCG increased (P<0.05) the number of large follicles. The proportion of good oocytes was increased (P<0.05) with FSH-P8 or FSH-P16 compared with treatment with eCG or PG 600. Moreover, oocytes from eCG-treated gilts had a greater (P<0.05) rate of male and female pronuclei than FSH-P or saline-treated gilts. In conclusion, treatment with FSH-P resulted in a higher proportion of oocytes with multilayer cumulus cells, whereas treatment with eCG resulted in higher pronuclear rates following in vitro fertilization in prepubertal gilts.