Superovulation in the cow with pregnant mare serum gonadotrophin: effects of dose and antipregnant mare serum gonadotrophin serum.

The effects of pregnant mare serum gonadotrophin (PMSG) dose and PMSG antiserum on superovulation in crossbred beef cows were studied. In experiment I, three groups were treated with 1200, 2400 or 3600 IU of PMSG and 48 h later with prostaglandin (PGF). The mean numbers of corpora lutea (CL), unovulated follicles, and total ova/embryos collected increased as the PMSG dose increased. The percent of fertilized ova and transferable embryos was lowest in the highest dose group (p < 0.05). In experiment II, all cows received 2500 IU of PMSG; groups 1 and 2 were treated with sheep anti-PMSG serum at 48 h or 60 h after PGF; group 3 cows were PMSG-only controls. The number of CL was lowest and the number of unovulated follicles highest in the PMSG-only group (p < 0.05). The number of CL was higher in group 2 (anti-PMSG at 60 h) than in the control group, with the anti-PMSG at 48 h not different from the other groups. Numbers of total ova/embryos, fertilized ova, and transferable embryos were higher (p < 0.05) in both antiserum-treated groups relative to the PMSG-only group. We conclude that superovulation of beef cows with PMSG and treatment with PMSG antiserum will induce a higher superovulatory response and will result in higher CL numbers and fewer unovulated follicles. Further, the variability in the superovulatory response to PMSG treatment was still evident when PMSG antiserum was administered.     

Active immunization against inhibin improves superovulatory response to exogenous FSH in cattle

The effect of active immunization against inhibin on the response to superovulatory treatment by porcine FSH (pFSH) was investigated in cattle. Japanese black cows were sc injected with 1 mg of porcine inhibin alpha-subunit fragment (1-26) conjugated with rabbit serum albumin (inhibin-immunized group; n=14) or rabbit serum albumin alone (control group; n=12) in Freund's complete adjuvant. Booster injections (half the amount of the primary injection) were given 35 and 70 days after the primary injection. All cows were superovulated three times with pFSH. Three days after each injection of the antigen, a progesterone-releasing intravaginal device (CIDR-B) was inserted vaginally into all animals and left in place for 10 days. Forty-eight hours before CIDR-B removal, all animals were sc injected with 30 mg pFSH dissolved in 40% polyvinylpyrrolidone, and im injected with 750 microg of PGF2alpha at CIDR-B removal. Cows were artificially inseminated twice during estrus, and ova or embryos were collected 7 or 8 days after estrus. The number of corpora lutea, the number of ova or embryos and the number of transferable embryos in inhibin-immunized cows (12.1+/-1.2, 11.1+/-1.3 and 6.2+/-1.0, respectively) were significantly greater than those in the controls (8.2+/-1.0, 5.7+/-1.1 and 3.1+/-0.7, respectively). These results indicate that active immunization against inhibin enhanced ovarian response to the usual superovulatory treatment in cattle. Therefore, immunization against inhibin may be a useful approach for improving the response to superovulation in cattle.     

Relationships among estrous behavior, superovulatory response and grade 1 embryo sex ratio in superovulated Holstein heifers

In this study, we first attempted to determine whether the timing of artificial insemination affects the sex ratio of seven-day-old embryos in superovulated Holstein heifers. The superovulatory treatment consisted of eight decreasing doses of FSH for 4 days and 2 doses of PGF(2alpha) given with the last two doses of FSH. The superovulated heifers were given a GnRH analogue 48 h after the first PGF(2alpha) treatment and were artificially inseminated 48 h (n=10) or 56 h (n=8) after the first PGF(2alpha) treatment. There were no significant differences in the percentages of unfertilized ova and transferable embryos (grades 1 to 3) between the two groups. The proportions of female grade 1 embryos did not significantly differ from the expected ratio of 50:50 (49.3% at 48 h and 52.5% at 56 h). We then compared the estrous behavior and superovulatory responses of the heifers with a proportion of female embryos of 50% or less (n=7, Low group) to those of the heifers with a proportion of female embryos of more than 50% (n=9, High group). The Low group had a longer duration of estrus and a higher superovulatory response than the High group. These findings offer little encouragement for prediction of the population of female embryos collected from superovulated heifers. Further studies are necessary to evaluate to what degree maternal hormone levels are related to estrus duration and sex ratio.     

Effects of prostaglandin F2 alpha and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance of fluorogestone acetate PMSG-treated ewes

Two experiments were conducted to examine the effect of prostaglandin F2 alpha (PGF2 alpha) and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance (fertility, prolificacy and fecundity) of ewes previously treated with fluorogestone acetate (FGA) and PMSG. In the first experiment, 29 ewes were synchronized for estrus with FGA and PMSG but not bred at the postsynchronization estrus. On day 10 of the first post-synchronization estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to experienced, fertile, raddled rams. Twenty-four of the 29 ewes (83%) had viable fetuses 9 weeks after the PGF2 alpha-PMSG treatment. In the second experiment, 64 ewes were treated with FGA-PMSG, and 33 were exposed to fertile, raddled rams at the synchronized estrus. A second group of 31 ewes was not bred at the synchronized estrus, but on day 12 of the postsynchronized estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to fertile, raddled rams. Sixty-six percent of the 33 ewes lambed in the FGA-PMSG-treated group and 60% of the 31 ewes lambed in the PGF2 alpha-PMSG-treated group. Differences in reproductive performance between these two treatment groups were not statistically significant. The results suggest that the PGF2 alpha-PMSG treatment combination does not adversely affect reproductive performance of ewes.     

Comparison of the effect of cronolone sponges and PMSG or cloprostenol on estrous induction in Turkish Saanen goats

The efficiency of cronolone sponges in combination with either pregnant mare serum gonadotrophin (PMSG) or cloprostenol (PGF2alpha) for inducing and synchronizing the estrous cycle in Turkish Saanen does was investigated during the transition from non-breeding to breeding season. All does (n = 80) were treated with 20 mg cronolone sponges for 11 days and divided into 4 equal groups. In addition, each doe received an intramuscular injection of either 1.5 ml sterile saline solution, 0.075 mg PGF2alpha, 500 IU PMSG or 500 IU PMSG and 0.075 mg PGF2alpha, 24 h before the sponge removal. Cervical artificial insemination (AI) with frozen-thawed semen was performed once 16 h after the detection of the first accepted mount. The total estrous response for the first 24 +/- 4 h, total estrous response within 96 h, time to onset of the induced estrus, duration of the induced estrus and pregnancy rate was found to be 75.0%, 97.5%, 31.4 +/- 1.2 h, 29.3 +/- 1.2 h, and 33.3%, respectively. There were significant differences between the first two groups and the last two groups in terms of the onset of induced estrus and estrous response at the first 24 +/- 4 h (P < 0.05). These results indicate that the use of cronolone/PMSG was more effective than cronolone/PGF2alpha in the attainment of early and compact induction of estrus in Turkish Saanen does.     

Effect of age and norgestomet on endocrine parameters and production of embryos in superovulated beef cows

Effects of age of cow and a norgestomet (N) implant on number of embryos and endocrine responses to induction of superovulation were studied in old (greater than 12 yr) and young (5 to 7 yr) lactating beef cows. Seventeen cows (8 old and 9 young) received a 6-mg N ear implant on d 4 or 5 of the cycle (d 0 = estrus); the remaining 17 cows (9 old and 8 young) served as untreated controls (C). All animals were treated with 38 mg of porcine follicle-stimulating hormone (FSH-P) in decreasing dosages over a 4.5-d period beginning on d 10 or 11. Regression of the corpus luteum was induced with injections of PGF2 alpha at 0800 and 2000 on d 4 of FSH-P treatment; implants were removed at the second injection of PGF2 alpha. Cows were inseminated artificially 12 and 24 h after onset of estrus. Embryos were collected on d 7 or 8 postinsemination. Blood samples were obtained daily at 0800 from 2 d prior to initiation of treatment with FSH-P until collection of embryos. An additional sample was collected each day at 2000, from the first injection of PGF2 alpha to 1 d after onset of estrus. Samples were assayed for luteinizing hormone (LH), progesterone (P4), follicle stimulating hormone (FSH) and estradiol-17 beta (E2). Total number of embryos plus ova recovered was lower (P less than .01) in N-treated (5.2 +/- 1.1) than in C-treated (10.6 +/- 1.6) cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical and endocrine responses to embryonic and fetal death induced by manual rupture of the amniotic vesicle during early pregnancy in cows

Pregnancy was terminated in 4 cows by manual rupture of the amniotic vesicle on day 41 (n = 1) and day 46 (n = 3) after insemination. Each cow was necropsied 36 days after vesicle rupture, by which time only one cow had come into estrus. Luteal activity, monitored daily by plasma progesterone assay, was still evident in 2 cows 35 days after fetal death; in the remaining 2 cows, regression of the corpus luteum (CL) was achieved at 28 and 32 days, respectively. Uterine release of prostaglandin F2 alpha (PGF2 alpha), measured as the 15-keto metabolite (PGFM) PGF2 alpha, was monitored by a plasma sampling schedule; specimens were obtained every 4 hours. There were no appreciable releases of PGF2 alpha associated with fetal death. The first appreciable PGF2 alpha release in episodic form was seen only in conjunction with CL regression. In all cows, a palpable membrane slip was evident for 18 days after rupture of the amniotic vesicle, although at that time, uterine resilience was diminished in the 2 cows in which the CL subsequently regressed. After 18 days, the uterus was noticeably edematous and fluid-filled in all cows; in 1 of the cows with a regressed CL, the uterus had returned to prepregnancy size and tone by day 33.(ABSTRACT TRUNCATED AT 250 WORDS)     

Conception rates to artificial insemination in primiparous, suckled cows exposed to the biostimulatory effect of bulls before and during a gonadotropin-releasing hormone-based estrus synchronization protocol

The objective of these studies was to evaluate whether exposing primiparous, suckled beef cows to the biostimulatory effect of bulls alters breeding performance associated with an estrus synchronization protocol that included GnRH followed 7 d later by PGF(2alpha) and fixed-time AI (TAI). This was a composite analysis of 3 experiments that evaluated (1) the effects of bull exposure at different days after calving (yr 1); (2) the biostimulatory effects of bull excretory products (yr 2); and (3) the biostimulatory effects of familiar and unfamiliar bulls (yr 3) on the resumption of ovarian cycling activity. In all studies, cows were exposed (biostimulated; n = 94) or not exposed (nonbiostimulated; n = 67) to bulls or excretory products of bulls for at least 60 d before the beginning of the estrus synchronization protocol. Average calving day did not differ among years and was 52 +/- 5 d. Year did not affect the proportions of biostimulated and nonbiostimulated cows that were cycling at the beginning of the estrus synchronization protocol; however, a greater (P < 0.001) proportion of biostimulated than nonbiostimulated cows were cycling at this time. In each year, cows were given GnRH followed by PGF(2alpha) 7 d later. Cows were observed for estrus twice daily (am and pm) after PGF(2alpha). Cows that exhibited estrus before 54, 60, and 64 h after PGF(2alpha) were inseminated by AI 12 h later in yr 1, 2, and 3, respectively. Cows that failed to show estrus were given GnRH and TAI at 62, 72, and 72 h after PGF(2alpha) in yr 1, 2, and 3, respectively. Conception rates were determined by transrectal ultrasonography 35 d after TAI in each year. The percentages of cows that exhibited estrus after PGF(2alpha) and before TAI, the interval from PGF(2alpha) to estrus, and the percentages of cows inseminated 12 h after estrus or at TAI did not differ between biostimulated and nonbiostimulated cows and were 51%, 54.7 +/- 7.3 h, 35%, and 65%, respectively. Conception rates for cows bred by AI 12 h after estrus did not differ between biostimulated and nonbiostimulated cows; however, the TAI conception rate was greater (P < 0.05) for biostimulated cows (57.6%) than for nonbiostimulated cows (35.6%). We conclude that TAI conception rates in an estrus synchronization protocol that includes GnRH followed 7 d later by PGF(2alpha) may be improved by the biostimulatory effect of bulls in postpartum, primiparous cows.     

Effects of standing estrus and supplemental estradiol on changes in uterine pH during a fixed-time artificial insemination protocol

Cows that exhibit estrus within 24 h of fixed-time AI have elevated concentrations of estradiol and greater pregnancy rates compared with cows not in estrus. Our objective was to determine whether estradiol, estrus, or both had an effect on uterine pH during a fixed-time AI protocol. Beef cows were treated with the CO-Synch protocol (100 mircog of GnRH on d -9; 25 mg of PGF(2alpha) on d -2; and 100 mircog of GnRH on d 0). One-half of the cows received an injection of estradiol cypionate (ECP; 1 mg) 12 h after PGF(2alpha). Cows detected in standing estrus within 24 h of the second GnRH injection were considered to be in standing estrus. Uterine pH was determined in all animals 12, 24, and 48 h after the PGF(2alpha) injection. For Exp. 1, pH was also determined 72 and 96 h after the PGF(2alpha) injection; in Exp. 2, pH was also determined at 54, 60, 66, 72, 78, 84, 90, and 96 h after the PGF(2alpha) injection or until ovulation. A treatment x time interaction (P < 0.01) influenced concentrations of estradiol. All cows had similar (P > 0.15) concentrations of estradiol at the time of ECP administration, but after ECP treatment all cows treated with ECP and control cows that exhibited estrus had greater (P < 0.01) concentrations of estradiol compared with nontreated cows that did not exhibit estrus. In all animals, estradiol diminished 48 h after the PGF(2alpha) (time of the second GnRH injection), but ECP-treated cows, regardless of estrus, had elevated (P < 0.02) concentrations of estradiol compared with control cows. There was a treatment x time interaction (P < 0.001) on uterine pH. All cows had similar uterine pH (P > 0.19) 24 h after the PGF(2alpha) injection. Control cows that did not exhibit estrus had a greater uterine pH compared with control cows that exhibited estrus (P < 0.01) and ECP cows that exhibited estrus (P = 0.05) 48 h after the PGF(2alpha) injection (7.0 +/- 0.1 vs. 6.7 +/- 0.1 and 6.8 +/- 0.1, respectively). Estradiol cypionate-treated cows not exhibiting estrus were intermediate (6.8 +/- 0.1; P > 0.05). All cows had similar uterine pH 72 h after the PGF(2alpha) injection through ovulation (P > 0.06). In summary, uterine pH was similar among all animals that exhibited estrus, regardless of treatment with ECP.     

Production of estradiol by each ovary during the estrous cycle of cows

The objective of our experiment was to examine changes in serum concentrations of estradiol in each utero-ovarian vein before, during and after gonadotropin surges. Four cows were given prostaglandin F2 alpha (PGF2 alpha) during diestrus and three cows were allowed to cycle spontaneously. All cows had a cannula in each utero-ovarian vein and in one jugular vein. Most cows had two transient rises in estradiol, primarily coming from a single ovary, preceding and after luteinizing hormone (LH) surges. The first rise in estradiol began after luteal regression and was sustained from 48 h before a pre-ovulatory LH surge to the end of the LH surge. The second rise in estradiol was sustained from 72 to 168 h after the end of an LH surge. To determine how rapidly asymmetrical production of estradiol began during luteolysis, several cows were injected with PGF2 alpha during the luteal phase. Blood samples were taken from a jugular and both utero-ovarian veins at hourly intervals before and after PGF2 alpha. Asymmetrical production of estradiol began within 3 h after an injection of PGF2 alpha. We concluded: (1) that a single ovary was responsible for the sustained increases in concentration of estradiol that occur during proestrus to estrus and early diestrus in cows and (2) that cows may have at least one follicle capable of producing estradiol during most days of an estrous cycle, thus little delay in selection of which follicle eventually ovulates occurs after luteal regression.     

Retention of a functional corpus luteum and peripheral concentrations of 13,14-dihydro-15-keto-prostaglandin F2alpha following metestrus administration of Syncro-Mate-B.

This study was conducted to examine the effects of metestrus administration of SyncroMate-B (SMB) on PGF2alpha secretion and corpus luteum (CL) development. In a study replicated over 2 yr, cows were observed for spontaneous estrus in yr 1, and cows received an injection of 25 mg of PGF2alpha and were observed for subsequent estrus in yr 2. At standing estrus (estrus = d 1), cows were randomly allotted to receive either the standard SMB regimen (n = 40) on d 3 of the estrous cycle or no treatment (n = 8). Fifty percent (n = 20) of SMB-treated cows were administered PGF2alpha on d 10 of the estrous cycle 48 h prior to implant removal. Twice-daily blood samples were collected in the morning (AM) and evening (PM) from d 2 AM through d 14 AM of the treated estrous cycle and subsequently analyzed for progesterone (P4) and PGF2alpha metabolite (PGFM). Prior to statistical analysis, SMB- and SMB/PGF2alpha-treated cows were sorted according to P4 concentration at d 10 of the treated estrous cycle to either a CL functional group (P4 > or = 1 ng/mL; n = 20) or a CL nonfunctional group (P4 < 1 ng/mL; n = 17). Following d 10 AM administration of PGF2alpha, functional and nonfunctional groups were further subdivided based on treatment. The groups were as follows: untreated control cows (n = 8); SMB-treated cows retaining a functional CL (SMB-F; n = 8); SMB-treated cows with a nonfunctional CL (SMB-N; n = 11); SMB/PGF2alpha-treated cows retaining a functional CL (SMB/PG-F; n = 12); and SMB/PGF2alpha-treated cows with a nonfunctional CL (SMB/PG-N; n = 6). Of all SMB-treated cows, 54% retained a functional CL through d 10 AM of the treated estrous cycle. Mean serum P4 concentrations increased for cows in all groups until d 7, after which P4 concentrations increased for cows in SMB/PG-F, SMB-F, and control groups and decreased for cows in SMB/PG-N and SMB-N groups. Following PGF2alpha administration on d 10, mean serum P4 concentrations remained < 1 ng/mL for cows in SMB/PG-N and SMB-N groups, decreased to < 1 ng/mL for cows in the SMB/ PG-F group, and remained > 1 ng/mL for cows in SMB-F and control groups. Mean serum PGFM concentrations tended (P = .06) to increase in cows with nonfunctional CL compared with control cows on d 8 AM and were greater (P < .05) in cows with functional CL on d 8 PM through d 9 PM. These results indicate that retention of a functional rather than a nonfunctional CL following metestrus administration of SMB is dependent on a premature release of uterine PGF2alpha.     

PMSG profiles in superovulated and anti-PMSG antiserum treated mice and heifers with enzymeimmunoassay

A sandwich enzymeimmunoassay (EIA) for pregnant mare serum gonadotropin (PMSG) using a microtiter plate was developed. Sensitivity of the assay to PMSG was 15.6 mIU/ml (0.2 ng/well). The PMSG levels in serum were measured with the EIA in superovulated and anti-PMSG rabbit antiserum treated mice and heifers. In mice, the PMSG blood level was measurable in the serum 4-6 days after intraperitoneal injection of 5-30 IU of PMSG. The administration of anti-PMSG antiserum at the same dose level as PMSG caused a rapid decrease in the PMSG blood level, declining to undetectable levels within 17 hours. In heifers, the PMSG level was measurable at 10-11 days after the injection of 2500 or 3000 IU of PMSG. When antiserum was injected 48 hours after the PMSG injection, the clearance rate of PMSG was affected by the route of the administration. The administration of 3000 units of anti-PMSG antiserum intravenously caused a rapid decline and the disappearance of circulating PMSG within 17 hours. When 3000 units of anti-PMSG antiserum was injected intra-muscularly, the PMSG blood level also decreased and became unmeasurable 24 hours after administration; however, it was still detectable for up to 17 hours. These results indicate that the administration of anti-PMSG antiserum at the proper timing and dosage could lead to successful superovulation through the improvement of hormonal conditions.     

Synchronizing estrus and(or) ovulation in beef cows after combinations of GnRH, norgestomet, and prostaglandin F2alpha with or without timed insemination

Three experiments were conducted to induce estrus and(or) ovulation in 1,590 suckled beef cows at the beginning of a spring breeding season. In Exp. 1, 890 cows at three locations were allotted to three treatments: 1) GnRH on d -7 + prostaglandin F2alpha (PGF2alpha) on d 0 (Select Synch); 2) GnRH on d -7 + PGF2alpha on d 0 (first day of the breeding season) plus a norgestomet implant (NORG) between d -7 and 0 (Select Synch + NORG); or 3) two injections of PGF2alpha given 14 d apart (2xPGF2alpha). More (P < 0.05) cycling cows were detected to have been in estrus after both treatments that included GnRH, whereas, among noncycling cows, the addition of norgestomet further increased (P < 0.05) the proportion in estrus. Pregnancy rates were greater (P < 0.01) among noncycling cows after treatments that included GnRH. For cows that calved >60 d before the onset of the breeding season, conception rates were greater (P < 0.01) than those that calved < or =60 d regardless of treatment, whereas days postpartum had no effect on rates of detected estrus. When body condition scores were < or =4 compared with >4, rates of detected estrus (P < 0.05) and conception (P = 0.07) were increased. In Exp. 2, 164 cows were treated with the Select Synch + NORG treatment and were inseminated either after estrus or at 16 h after a second GnRH injection (given 48 h after PGF2alpha). Conception and pregnancy rates tended (P = 0.08) to be or were less (P < 0.05), respectively, for noncycling cows inseminated by appointment, but pregnancy rates exceeded 53% in both protocols. In Exp. 3, 536 cows at three locations were treated with the Select Synch protocol as in Exp. 1 and inseminated either: 1) after detected estrus (Select Synch); 2) at 54 h after PGF2alpha when a second GnRH injection also was administered (Cosynch); or 3) after detected estrus until 54 h, or in the absence of estrus, at 54 h plus a second GnRH injection (Select Synch + Cosynch). Conception rates were reduced (P < 0.01) in cows that were inseminated by appointment. An interaction of AI protocol and cycling status occurred (P = 0.05) for pregnancy rates with differing results for cycling and noncycling cows. Across experiments, variable proportions of cows at various locations (21 to 78%) were cycling before the breeding season. With the GnRH or GnRH + NORG treatments, ovulation was induced in some noncycling cows. Conception rates were normal and pregnancy rates were greater than those after a PGF2alpha program, particularly when inseminations occurred after detected estrus.     

PMSG诱导的双胎母牛血清中P_4、LH、E_2的变化及与单、双胎的关系

于发情周期的第１０天,给１２头参试母牛肌注ＰＭＳＧ（孕马血清促性腺激素,总剂量为１３５０～２０００ＩＵ）。每头参试牛于肌注ＰＭＳＧ前的当天,肌注后２４ｈ、４８ｈ,肌注氯前列烯醇后２４ｈ、４８ｈ,发情后４８ｈ,排卵或妊娠５、１０、２０、６０ｄ,从颈静脉各采血１次,共采１０次,每次１０ｍｌ,离心后分离血清。用放免法测定上述各生理时期血清中Ｐ４（孕酮）、ＬＨ（促黄体素）、Ｅ２（雌二醇）水平。结果表明,适量的ＰＭＳＧ（１３５０～２０００ＩＵ）能诱导母牛产双胎,其双胎率为４２．９％（３／７）。测定早期妊娠母牛（５、１０、２０、６０ｄ）血清中Ｐ４水平,证明双胎牛均高于单胎牛。     

Plasma insulin-like growth factor-I concentrations increase during the estrous phase in goats

The objective of this study was to characterize plasma insulin-like growth factor-I (IGF-I) profiles during the estrous cycle in goats. Frequent blood samples were drawn during the day of estrus and during the luteal phase on Day 10 after estrus, and plasma growth hormone (GH) and IGF-I profiles were examined. Then, daily blood samples were drawn throughout the estrous cycle or during induction of estrus by prostaglandin F(2alpha) (PGF(2alpha)) to further clarify the IGF-I profiles. GH was secreted in an episodic manner in the estrous and luteal phases in goats. There were no significant differences in the mean concentrations, pulse amplitude and pulse frequency of GH between the estrous and luteal phases. IGF-I concentrations during estrous phase were higher than those in the luteal phase (P<0.05). Plasma IGF-I increased approximately two days before behavioral estrus, and the IGF-I peak was observed in accordance with the appearance of estrus. The elevated IGF-I levels then declined to basal values 4 to 5 days after estrus. When estrus was induced by PGF(2alpha), plasma IGF-I concentrations increased after treatment, and the concentration 2 days after treatment (day of appearance of behavioral estrus) was significantly higher than concentrations before treatment (P<0.05). The elevated IGF-I levels then declined during the 3 days after treatment. These results indicate that plasma IGF-I concentrations increase during estrus in goats.     

Enzyme activity in bovine cervical mucus during spontaneous and induced estrus

The purpose of the present research was to compare the enzyme activity of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), α-amylase, α-manosidase, β-N-acetyloglucosaminidase, β-glucuronidase, and β-galactosidase in the cervical mucus of cows during spontaneous and induced estrus. Friesian cows (n = 106) were assigned to 4 groups: 1) no treatment; 2) progesterone releasing intervaginal device (PRID) for 12 days plus pregnant mare serum gonadotrophin (PMSG) at the removal of the PRID; 3) PGF2α2 doses 11 days apart; and 4) PRID for 7 days plus PGF2α 1 dose, 24 hours before removal of the PRID. Fourteen cows were excluded from the trial because of an inadequate quantity of cervical mucus collected or a lost PRID. The cows from the 3 induced estrus groups were artificially inseminated (AI) twice, while those with spontaneous estrus received only a single AI. Cervical mucus samples were collected from all cows 5 to 30 min before the first AI. The results are summarized as follows: 1) ALP and α-amylase activity for spontaneous estrus were similar to those for induced estrus; 2) LDH activity levels during spontaneous estrus were significantly lower (P < 0.001) than that in the P4 and P4+PGF2α induced estrus groups; and 3) glycosidases' activity was significantly lower (P < 0.001) in the spontaneous estrus group than that in the induced estrous groups. In conclusion, the activity of most enzymes in the cervical mucus of cows, in the present study, was significantly different between the spontaneous and the induced estrus groups.     

黄牛孪生处理前后发情周期的外周血中GnRH水平

在母牛产后第1次发情后第10d，给5头发情周期正常的母牛安装颈静脉血管导管；在母牛产后第2个发情周期进行挛生处理，即在产后第2次发情后第10d注射PMSG2000IU，2d后注射氯前列烯醇0．4mg第3次发情后注射抗PMSG抗体2000IU。自第1个发情周期第10d开始，每天间隔10min连续采血2h。发情当天间隔30min采血一次，直到第3次发情结束为止。挛生处理后采血间隔时间和方法与处理前不同。应用酶免疫测定方法测定血清中促性腺激素释放激素水平。结果表明：（1）牛外周血中GnRH释放具有脉冲性；（2)PMSG处理后外周血中GnRH水平升高，表现为脉冲频率增加，脉冲峰值升高。     

Synchronization of estrus in postpartum beef cows with melengestrol acetate and prostaglandin F2 alpha

At the beginning of the breeding season, most beef herds consist of a population of cyclic and anestrous postpartum cows. To be most effective and economical, an estrous synchronization method for postpartum beef cows must be capable of synchronizing estrus in cyclic cows and inducing estrus in anestrous cows. In the first of two experiments, the combination of melengestrol acetate (MGA) fed for 9 d and prostaglandin F2 alpha (PGF2 alpha) administered on the last day of MGA feeding synchronized estrus in cyclic cows (94%) and induced estrus in anestrous cows (66%) as effectively as combining PGF2 alpha with a progestin implant (97 and 75%, respectively). In the second experiment, MGA treatment was necessary for 7 d prior to administering PGF2 alpha to maximize the expression of estrus in cyclic and anestrous cows. In both experiments the proportion of cows exhibiting a synchronized estrus and the pregnancy rates tended to be higher for cows that were cyclic prior to treatment. However, the MGA-PGF2 alpha treatments consistently induced estrus in more than 50% of the anestrous cows and approximately one-third of the cows that were anestrous prior to treatment conceived during the synchronized breeding period. The MGA-PGF2 alpha treatment was 33 to 46% less expensive than a comparable estrous synchronization method that is approved by the U.S. Food and Drug Administration. If feeding MGA and administering PGF2 alpha is approved, it may be the treatment of choice for synchronizing estrus in cyclic cows and inducing estrus in anestrous cows when supplemental feeding is feasible.     

Endocrine changes in beef heifers superovulated with follicle-stimulating hormone (FSH-P) or human menopausal gonadotropin.

The effects of superovulatory treatment (FSH-P vs human menopausal gonadotropin, HMG) and of route of administration (i.m. vs. i.v.) of prostaglandin F2 alpha (PGF2 alpha) on hormonal profiles were determined in 32 Angus x Hereford heifers. Heifers were superstimulated with either FSH-P (total of 26 mg) or HMG (total of 1,050 IU) beginning on d 9 to 12 of an estrous cycle and PGF2 alpha (40 mg) was administered at 60 and 72 h after the beginning of superovulatory treatments. Heifers were artificially inseminated three times at 12-h intervals beginning 48 h after PGF2 alpha treatment. Blood serum samples were collected immediately before treatments began, at 12-h intervals during the first 60 h, each 4 h during the next 96 h, and each 12 h until day of embryo collection. Concentrations of LH and FSH were not affected by hormone treatments, route of PGF2 alpha injection, or interactions between them. Estradiol-17 beta (E2-17 beta) levels were higher (P less than .05) in HMG- than in FSH-P-treated heifers 60 h after gonadotropin treatment. Peak concentration of E2-17 beta occurred earlier (P less than .05) in HMG- than in FSH-P-treated heifers and earlier in heifers injected with PGF2 alpha i.m. than in those injected i.v. Progesterone concentrations were not influenced by treatment or route of PGF2 alpha administration, but were affected (P less than .01) by the interactions between treatment and route of PGF2 alpha administration. Progesterone declined to basal levels earlier in the FSH-P- than in the HMG-treated heifers.(ABSTRACT TRUNCATED AT 250 WORDS)     

猪胚胎移植中同期发情母猪的内分泌研究

〗本研究选用猪胚胎移植的３头供体母猪，依次用前列腺素（ＰＧ），孕马血清促性腺激素（ＰＭＳＧ）和人绒毛膜促性腺激素（ＨＣＧ）作同期发情和超数排卵处理，于处理第１１天做剖腹手术采集胚胎，在整个处理过程中多次采血，监测了血清中孕酮（Ｐ４），雌二醇（Ｅ２），促黄体素（ＬＨ）和硫酸雌酮（Ｅ１Ｓ）四种激素浓度的变化，并据此来讨论同期发情和超数排卵处理成功和失败的原因。