Dose Of Pregnant Mare Serum Gonadotropin Research Articles

Quantitative Histomorphometry of Pre-ovulatory Follicles and Uterine Glands of Ongole-grade Heifer in Response to the Low Doses of PMSG Administration

Injection of female mammalian animals with gonadotropin prior to mating using superovulation dose increases estradiol 17beta (E2) synthesis and secretion and improves the growth and development of the uterus to support prenatal growth with the side effect of increasing litter size. This experiment was designed to study the effects of low doses of PMSG injection in heifers on the growth of granulose cells (GC) of pre-ovulatory follicles, E2 synthesis, and uterine glands growth and development. Nine Ongole-grade heifers were divided into three groups of doses of PMSG injection, i.e., 0 IU/kg BW, 0.5 IU/kg BW, and 1.0 IU/kg BW. The injection of pregnant mare serum gonadotropin (PMSG) was conducted at the early stage of the second follicle wave. Blood samples were collected at estrus (day 0) to measure plasma E2 concentrations. The ovary and uterus were collected for histological observation after slaughtering the animal. The results showed that non-superovulation doses of PMSG injections at the second follicle wave significantly increased the growth of GC that eventually produced a significantly higher plasma E2 concentration by 39.47% and 113.57%, in heifers receiving 0.5 IU/kg BW and 1.0 IU/kg BW (p<0.05), respectively. The increase in E2 synthesis and secretion significantly stimulated the growth and development of uterine glands (p<0.05), which was reflected in the improved measures of uterine glands. In conclusion, injections of heifers with low doses of PMSG at the second follicle wave could increase the growth of GC to produce a higher secretion of E2 that eventually improves the growth and development of uterine glands in the endometrium without the risk of multiple calving.

The Effect of Using CIDR and Various Doses of PMSG as Well as Genistein on the Reproductive Characteristics of Palu Fat-tailed Sheep

The objective of this study was to observe the reproductive characteristics of Palu fat-tailed sheep affected by animal parities given pregnant mare serum gonadotropin (PMSG) and genistein (GEN) as a synthetic phytoestrogen. This study employed 32 ewes arranged in a completely randomized experimental design. The first factor was parity (P2 and P3) and second factor was a hormonal treatment as follows; H0 (14 d-controlled internal drug release or CIDR implant as control), H1 (CIDR+PMSG at 15 IU/kg BW, im injection), H2 (CIDR+GEN 0.1 mg/kg BW, iv injection); H3 (CIDR+PMSG at 15 IU/kg BW and GEN at 0.1 mg/kg BW, iv injection). Results indicated that all animals exhibited estrous and the onset for H1 was significantly earlier than for H2 and H0. The duration of estrous for P3 was significantly longer than for P2, while that for H1 was significantly longer than for H2 and H0. Gestation rate was 93.75%, birth rate was 83.33% and length of gestation was 147.76±1.54 d. Birth weight for P3 was significantly higher than for P2. It is concluded that CIDR, PMSG, and genistein enhanced the estrous characteristics in Palu fat-tailed sheep but did not affect litter size and birth weight.

Decreased ascorbic acid biosynthesis in response to PMSG in the pre-pubertal female rat ovary

Ascorbic acid (AA) is known to be an important antioxidant serving as a cofactor in collagen synthesis, and thus facilitates follicular growth in the ovary. Many studies have shown that AA is synthesized in the liver and transported to other organs including ovary, however, there is no direct evidence of ascorbic acid synthesis in the ovary. Hence, we examined the expression pattern of different proteins (SMP30/GNL and GULO) involved in the AA synthesis in pre-pubertal rat, which showed significant expression of these proteins, suggesting the synthesis of AA in the ovary. Accumulation of AA in the ovary during follicular growth has been well demonstrated. However, the effect of Pregnant Mare Serum Gonadotropin (PMSG) on the AA synthesis in the ovary has not been studied in detail. Hence to decipher the effect, different doses of PMSG were injected subcutaneously into the pre-pubertal female rats, and ovarian AA level was measured after 48 h. A significant increase in AA content was observed in PMSG treated animal groups. Further, to understand the mechanism underlying ovarian AA accumulation, the expression levels of SMP30/GNL and GULO genes were measured. Expression of both the genes was significantly suppressed, which suggested a lowered AA synthesis in the PMSG treated rat ovary. For further understanding, mRNA expression of AA transporters SVCT1 and SVCT2 encoded by SLC23A1 and SLC23A2 genes respectively were measured, which showed increased level of SVCT1 expression. These observations suggested that the increased AA content might not be due to increased synthesis of AA within the ovary but possibly due to increased uptake from blood during the stimulation of follicular growth.

Improving the Quality of Oocytes of Old and Productive Ages White Rats (Rattus norvegicus) Using Pregnant Mare Serum Gonadotrophin

Abstract This study was conducted to improve the quality of oocytes in old-female rats by using pregnant mare serum gonadotrophin (PMSG). Female rats at productive age were used as a control. The experimental rats were injected with 4 doses of PMSG i.e., 0, 2.5, 5.0, and 10 IU PMSG. After 2 weeks of acclimation to the experimantal condition, the experimental rats were injected with PGF2α at a dose of 25µg/g BW two times with 2 days interval to synchronize estrous cycle. PMSG injections were conducted at the same time with the second PGF2α injection. After PMSG injection, the experimental rats were divided into two groups rats, i.e., rats without mating for masurement of oocyte qualities and rats mated for measurement of offspring qualities. Therefore, 16 experimental rats from each age group were sacrifized for maeasurement of oocyte qualities. The other 16 experimental rats for each age group were mated for measurement of offspring qualities. Parameters measured were hematological profile, uterine and ovarian weights, the qualities of oocytes, the qualities of the offsspring born by using swimming test and rat maze test. The collected data were analyzed by analysis of variance (ANOVA) and continued with Duncan test with a 95% confidence level. The data were analyzed using SSPS. The results showed that the improvement in the quality of oocytes in old female rats using the PMSG hormone in this study showed an increase in the quality of oocytes in old and productive age rats. The highest number of oocyte quality was found in rats of productive age (3.25) and significantly different (P&lt; 0.05) from the other oocyte qualities. The quality of offspring born to old age and productive age rats injected with PMSG were improved. It was concluded that the improvement of oocyte quality by using PMSG also improves offspring qualities.

Different estrous induction protocols during non-breeding season in Assaf ewes

This experiment was conducted to investigate the effect of pregnant mare serum gonadotrophin (PMSG) levels and the progestagen method on estrus response, onset and duration of estrus, lambing rate and litter size. A total of 20 Assaf ewes were used in the experiment, which was conducted during April, a month that is considered as non-breeding period in Palestine. Ewes were treated with intravaginal sponges containing 60 mg medroxyprogesterone acetate (MAP). Seven days later, sponges were removed and 10 new sponges were inserted to 10 of the experimental ewes. Following withdrawal of sponges at day 14, 5 ewes from each treatment groups were injected intramuscularly with a pregnant mare serum gonadotrophin (PMSG) at level of 300 or 600 IU. The results showed that level of PMSG and progesterone application methods had no significant effects on the tested parameters. This finding indicated that low level of PMSG can be applied for estrus synchronization. Results showed that using one sponge followed by a 300 IU dose of PMSG could induce estrus successfully with low cost comparing to application of two sponges and high doses of PMSG.

The Effects of Dose of Pregnant Mare Serum Gonadotropin (PMSG) on Reproductive Performance of Algerian Rembi Ewes during Seasonal Anoestrus

The current study was designed to evaluate the effect of different doses of pregnant mare serum gonadotropin (PMSG) on reproductive performance of Rembi ewe during seasonal anoestrus. A total of 120 sheep and 12 rams of Rembi ewe lamb were used in this experiment. Vaginal sponges containing 40 mg of fluorogestone acetate were inserted into the vagina of the ewes. The sponges were withdrawn on day 7 and 300 IU of PMSG (group 1, n=30, 500 IU of PMSG (group 2, n=30) and 700 IU of PMSG (group 3, n=30) were injected intramuscularly. The rates of fertility in groups 2, 3, 4 and the control group were found as 86,2%, 79,3%, 72,4%, and 44,8%, respectively. Fecundity rates were 1.14%, 1.20%, 1.03% and 0.48% in groups 2, 3, 4 and the control group, respectively. The rates of prolificacy in groups 2, 3, and 4 which received different doses of PMSG and the control group were found as 1.08%, 1.52 %, 1.43%, and 1.08%, respectively. Lambing rates were obtained as 67.5%, 77.5%, 77.5% and 58.8% in groups1, 2, 3 and in control group, respectively. The effect of the hormonal treatments on the birth weight of lambs averaging 1.90 ± 0.16, 2.60 ± 0.11 and 3.25 ± 0.19 kg respectively. The application of 500 IU PMSG was rather more effective than injections of 300 IU and 700 IU in Rembi ewes being outside the breeding season.

Reproductive efficiency of Pelibuey and Romanov × Pelibuey ewes synchronized with synthetic progesterone and low doses of PMSG under a hot environment

Thirty-nine multiparous ewes (19 Pelibuey and 20 Romanov &amp;times; Pelibuey) treated with fluorogestone acetate impregnated intravaginal sponges were used to evaluate the effects of low pregnant mare serum gonadotropin (PMSG) doses and genotype on their reproductive efficiency under heat stress conditions. The sponge treatment lasted for 12 days, and 24 h before sponge removal, ewes of each genotype were injected with 140 or 280 IU of PMSG. Ewes showing estrus were naturally mated twice. Reproductive performance was not affected (P &amp;gt; 0.05) by the dose &amp;times; genotype interaction. All treated ewes presented estrus signs within a 48-h period after sponge removal. Shorter (P &amp;lt; 0.05) estrus interval and higher (P &amp;lt; 0.05) fecundity were observed in ewes treated with 280 IU of PMSG compared to those treated with 140 IU. Pelibuey ewes exhibited shorter (P&amp;nbsp;&amp;lt;&amp;nbsp;0.01) estrus interval and greater (P &amp;lt; 0.01) fertility as compared with Romanov &amp;times; Pelibuey ewes. The response to estrus, gestation length, prolificacy, and percentage of single and multiple lambing were not affected (P &amp;gt;&amp;nbsp; 0.05) by dose or genotype. In conclusion, under heat stress conditions, low PMSG doses as 140 or 280 IU can be used to successfully induce and/or synchronize the estrus in Pelibuey ewes and their crosses with Romanov, regardless of reduced fertility observed in crossed Pelibuey ewes. If a more predictable and compact estrus is required, administration of 280 IU of PMSG is recommended.

Optimisation of an oviposition protocol employing human chorionic and pregnant mare serum gonadotropins in the Barred Frog Mixophyes fasciolatus (Myobatrachidae)

BackgroundProtocols for the hormonal induction of ovulation and oviposition are essential tools for managing threatened amphibians with assisted reproduction, but responses vary greatly between species and even broad taxon groups. Consequently, it is necessary to assess effectiveness of such protocols in representative species when new taxa become targets for induction. The threatened genus Mixophyes (family Myobatrachidae) has amongst the highest proportion of endangered species of all the Australian amphibians. This study developed and optimised the induction of oviposition in a non-threatened member of this taxon, the great barred frog (Mixophyes fasciolatus).MethodsGravid female M. fasciolatus were induced to oviposit on one or more occasions by administration of human chorionic gonadotropin (hCG) with or without priming with pregnant mare serum gonadotropin (PMSG). Treatments involved variations in hormone doses and combinations (administered via injection into the dorsal lymph sacs), and timing of administration. Pituitary homogenates from an unrelated bufonid species (Rhinella marina) were also examined with hCG.ResultsWhen injected alone, hCG (900 to 1400 IU) induced oviposition. However, priming with two time dependent doses of PMSG (50 IU, 25 IU) increased responses, with lower doses of hCG (200 IU). Priming increased response rates in females from around 30% (hCG alone) to more than 50% (p = 0.035), and up to 67%. Increasing the interval between the first PMSG dose and first hCG dose from 3 to 6 days also produced significant improvement (p<0.001). Heterologous pituitary extracts administered with hCG were no more effective than hCG alone (p = 0.628).ConclusionsThis study found that M. fasciolatus is amongst the few amphibian species (including Xenopus (Silurana) and some bufonids) that respond well to the induction of ovulation utilising mammalian gonadotropins (hCG). The optimal protocol for M. fasciolatus involved two priming doses of PMSG (50 IU and 25 IU) administered at 6 and 4 days respectively, prior to two doses of hCG (100 IU), 24 hours apart. This study is also the first to demonstrate in an amphibian species that responds to mammalian gonadotropins that an increase in the ovulation rate occurs after priming with a gonadotropin (PMSG) with FSH activity.

160 SUCCESSFUL PREGNANCY IN ESTRUS-SYNCHRONIZED HIMALAYAN TAHRS (HEMITRAGUS JEMLAHICUS) BY TRANSCERVICALLY INSEMINATING FRESH AND EXTENDED-CHILLED SEMEN COLLECTED BY ELECTROEJACULATION

In December 2009, 8 female Himalayan tahrs (Hemitragus jemlahicus) were synchronized by inserting CIDR devices for 13 or 15 days. One day before removal of the CIDRs, a combination of pregnant mare serum gonadotropin (PMSG) 400 IU and hCG 200 IU (PG600®, Intervet, Boxmeer, the Netherlands) was intramuscularly injected into each animal and PGF2α was injected at the time of CIDR withdrawal. Semen was collected by electrical stimulation, diluted, cooled to 5°C for 2 h, and maintained in a refrigerator before performing AI twice. Pregnancy diagnosis was conducted by Doppler ultrasonography on March 2, 2010. Four female Himalayan tahrs were impregnated, showing a fetus present in their uteri. In the first experiment in which CIDRs were inserted into the vagina of 4 Himalayan tahrs for 13 days, 3 of the tahrs were transcervically inseminated with fresh semen, whereas 1 was inseminated with frozen–thawed semen 33 h after CIDR removal. As a second insemination experiment, 46 h after CIDR removal, all 4 tahrs were inseminated with diluted (1:3) fresh semen. While the tahr that was later inseminated with frozen–thawed semen did not become pregnant, the other 3 Himalayan tahrs became pregnant. In the second experiment, CIDR devices were inserted into the vaginas of 4 Himalayan tahrs for 15 days. Extended (1:7)-chilled semen was used for transcervical insemination 42 and 49 h after CIDR withdrawal. When performing the second insemination, it was difficult or impossible to penetrate cervical canals. Thus, only 1 tahr became pregnant. These findings show 13 days of CIDR insertion, the dose of PMSG 400 IU and hCG 200 IU, and the use of PGF2α as beneficial for inducing oestrus synchronization, and prove that extended-chilled semen may also be used for artificial breeding of Himalayan tahrs. This is the first report of successful pregnancy induced by artificial insemination of fresh or extended-chilled semen in oestrus-synchronized Himalayan tahrs.

12 PHARMACOLOGICAL STIMULATION OF OVULATION IN THE BLACK FLYING-FOX (PTEROPUS ALECTO)

Artificial insemination (AI) involves the accurate detection of oestrus, the ability to pharmacologically induce ovulation, or both. This is particularly important in flying-foxes (Pteropus spp.) that do not have an overt behavioural oestrus. Pregnant mare serum gonadotropin (PMSG) stimulates folliculogenesis and ovulation in the Little Red Flying-fox (P. scapulatus; Towers PA and Martin L 1985 Proc. Aust. Soc. Reprod. Biol. 17, 115). In this study, a dose rate of 15 IU PMSG was used. Our study investigated if 15 IU PMSG would sufficiently induce ovulation in the larger, Black Flying-fox (P. alecto) or if a higher dose (30 IU) would be necessary. Before the mating season, a single injection of PMSG (Folligon®, Intervet Australia Pty Ltd, Bendigo East, Australia) was administered i.m. to eight adult females at 15 IU (n = 4) or 30 IU (n = 4) on Day 0. On Day 4, semen was collected by electro-ejaculation from adult males and inseminated intravaginally into females under isoflurane (Forthane®, Abbott Australasia Pty Ltd, Sydney, Australia) anaesthesia. Ovaries and reproductive tracts were surgically removed on Day 6, fixed, serially sectioned and stained using Gomori’s Stain. Histological sections were examined for evidence of ovarian activity and the presence of ova and spermatozoa in the reproductive tracts. Preliminary observations showed evidence of ovulation in both groups in the form of at least one CL in either ovary and an ovum in the ipsilateral oviduct or uterine horn. Ovaries of females stimulated with 30 IU PMSG differed noticeably from those treated with 15 IU in containing multiple, large, collapsed luteinized follicles with retained oocytes. Vascularization and glandular hypertrophy of the endometrium was also more evident in the higher dose group. No spermatozoa were observed in any of the excised tracts. These results suggest that whereas both doses of PMSG induce ovulation, the administration of 30 IU PMSG may over-stimulate the ovaries. This, in turn, could lead to an unphysiological environment for successful fertilization and embryonic development. A dose level of 15 IU or slightly above may be sufficient for subsequent attempts to stimulate folliculogenesis and ovulation in P. alecto. The absence of spermatozoa suggests that the site of insemination, the number of spermatozoa inseminated, or both requires further investigation if AI is to be successfully implemented in these species. We conclude that the ovarian responses to PMSG indicate that pharmacological induction of ovulation can be successfully achieved and thereby utilized in AI programs of endangered Pteropus species.

Administration of pregnant mare serum gonadotropin to Japanese quail (Coturnix coturnix japonica): dose response over seven days and comparison of delivery by daily injection or osmotic pump

AIMS: This study is part of a research programme that aims to develop a method of hormone treatment to stimulate breeding in female birds. The aims of this study were to compare dose rates and two different delivery methods, daily injection or osmotic pump, for hormone treatment of Japanese quail (Coturnix coturnix japonica) with pregnant mare serum gonadotropin (PMSG). METHODS: PMSG (0, 5, 10, 20, 40 and 80 IU PMSG/day) was administered to 6-week-old Japanese quail housed under short-day, cool-temperature conditions (8L:16D at 7–10°C) by daily injections or osmotic pump for 7 days. Three additional groups were untreated: one group was dissected at Day 0, and two groups were maintained under either short-day, cool-temperature or long-day, warm-temperature (16L:8D, 20°C) conditions for 7 days. Cloacal diameter was measured daily, and ovarian and oviductal mass and plasma oestradiol concentrations measured at the end of the treatment period. RESULTS: PMSG treatment stimulated ovarian and oviductal growth. After 7 days of treatment with 10–20 IU PMSG, ovarian and oviductal mass were similar to those in birds moved from short to long days. Females treated with the highest doses of PMSG (40 or 80 IU) had significantly larger cloacal diameters and ovarian and oviductal mass than other treated birds or birds maintained under long-day, warm-temperature conditions. Daily injections and osmotic pumps were equally effective methods of delivery. However, there was considerable variation in response to PMSG among individual birds and this was particularly obvious at the higher doses (20–80 IU PMSG). There were no differences in plasma oestradiol concentrations between groups treated using daily injections or osmotic pumps. CONCLUSIONS: A dose of 10 IU PMSG/day was chosen for use in future experiments with Japanese quail, for the first 7 days of treatment. The delivery method of choice for future studies will depend on the practical considerations of the research in question.

Effect of estrus synchronization and artificial insemination on reproductive performance of Merino sheep

The experiment was conducted to determine the reproductive performance (lambing rate and litter size) of sheep artificially inseminated at a synchronized estrus in relation to rams, dose of PMSG and number of artificial inseminations performed. During spring cyclic Merino adult ewes were treated with intravaginal sponges impregnated with 60 mg medroxyprogesterone acetate (MAP). After 14 days sponges were removed and the females received an intramuscular injection of either 375 or 400 IU pregnant mare serum gonadotropin (PMSG). Estrus detection was performed with vasectomized rams. Females in estrus were cervically inseminated with fresh diluted semen from different rams either once or twice. Data on lambing rate and litter size were recorded. Lambing rate was not affected by rams or number of inseminations. A higher proportion of ewes that received 400 IU PMSG lambed compared with those receiving 375 IU PMSG (76.47% v 54.32%; p<0.01). Litter size was not affected by any of the variables under study.

Effects of 4-hydroxyandrostenedione and hyperstimulation with pregnant mare serum gonadotrophin on early embryonic development in rats

A possible role of high oestradiol levels in mediating the adverse effects of hyperstimulation with pregnant mare serum gonadotrophin (PMSG) on early embryonic development in the rat was investigated using an aromatase inhibitor, 4-hydroxyandrostenedione (4-OHA), to inhibit endogenous oestradiol production. Three experiments were conducted in this study. In the first, varying doses of 4-OHA were administered either concurrently with human chorionic gonadotropin (hCG) to pro-oestrus female rats hyperstimulated at early di-oestrus stage with 20 IU PMSG or alone into nonhyperstimulated pro-oestrus females. At high doses of 1000, 2000, or 5000 µg/rat, 4-OHA substantially improved the survival of embryos in hyperstimulated females, while low doses of 100 and 500 µg/rat were ineffective. The protective effect of 4-OHA on embryo count was optimum at 2000 µg. When administered alone, only the highest dose of 5000 µg/rat 4-OHA increased embryo count. In the second experiment, higher doses of PMSG were studied (30 or 40 IU), with or without 5000 µg/rat 4-OHA given at the time of hCG injection. PMSG proved to be more detrimental with increasing dose, and 5000 µg/rat 4-OHA was able to rescue embryos from death in the 30, but not 40, PMSG group. In the third experiment, the influence of the timing of 4-OHA treatment on its ability to improve the embryo count in hyperstimulated females was examined by introducing 4-OHA 24 h earlier, rather than at the time of hCG treatment. The results showed the importance of timing of 4-OHA administration, as 5000 µg/rat 4-OHA was able to restore embryo survival in the 40 PMSG hyperstimulated group only when it was administered 24 h before hCG injection. Together, these results highlighted that 4-OHA, when administered at the appropriate time and dose, could reverse the negative effects of hyperstimulation from PMSG on early embryonic development. This may be due to its potent aromatase inhibiting properties that lead to the suppression of oestrogen production, thereby alleviating the supraphysiological level of oestradiol, which is typically present in PMSG-treated females. Interestingly, 4-OHA treatment on its own was able to positively influence embryo count when given at a high dose of 5000 µg/rat, and this may be associated with its weak androgenic properties. In conclusion, this study supports the hypothesis that excessive oestradiol is responsible for the negative effects of hyperstimulation with PMSG on early embryonic development.Key words: 4-hydroxyandrostenedione, embryonic development, PMSG, rat.

Ovulation in the tree shrew (Tupaia belangeri) induced by gonadotrophins

The induction of ovulation by exogenous gonadotrophins is an important approach for recovering oocytes used for studies on the reproductive biology of some mammals. In the present study, pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG) were used to induce ovulation in the tree shrew (Tupaia belangeri) using the following regimens. Groups A1-A3, multiple injections of PMSG (30-60 IU) followed by a single dose of hCG (30-60 IU); B1, combination of a single injection of PMSG (60 IU) with a single dose of hCG (60 IU); E1, combination of a single injection of PMSG (60 IU) with a single dose of hCG (30 IU) plus PMSG (30 IU); and administration of either PMSG (C1 and C2) or hCG (D1). The ovulation rate of animals producing oocytes with either first polar body or distinct perivitelline space, and the mean number of oocytes per animal were considered the most important criteria in each regimen. The most effective induction of ovulation was achieved in groups B1 and E1, with ovulation rates of 4/4 and 4/4, respectively, and mean numbers of ovulated oocytes per animal of 3.25 +/- 0.48 and 4.00 +/- 0.71 respectively. No ovulation was observed in the control group or in group D1. Therefore, regimes B1 and E1 were considered as the simplest and most effective for the induction of ovulation in the tree shrew.

Effects of 4-hydroxyandrostenedione and hyperstimulation with pregnant mare serum gonadotrophin on early embryonic development in rats

A possible role of high oestradiol levels in mediating the adverse effects of hyperstimulation with pregnant mare serum gonadotrophin (PMSG) on early embryonic development in the rat was investigated using an aromatase inhibitor, 4-hydroxyandrostenedione (4-OHA), to inhibit endogenous oestradiol production. Three experiments were conducted in this study. In the first, varying doses of 4-OHA were administered either concurrently with human chorionic gonadotropin (hCG) to pro-oestrus female rats hyperstimulated at early di-oestrus stage with 20 IU PMSG or alone into nonhyperstimulated pro-oestrus females. At high doses of 1000, 2000, or 5000 microg/rat, 4-OHA substantially improved the survival of embryos in hyperstimulated females, while low doses of 100 and 500 microg/rat were ineffective. The protective effect of 4-OHA on embryo count was optimum at 2000 microg. When administered alone, only the highest dose of 5000 microg/rat 4-OHA increased embryo count. In the second experiment, higher doses of PMSG were studied (30 or 40 IU), with or without 5000 microg/rat 4-OHA given at the time of hCG injection. PMSG proved to be more detrimental with increasing dose, and 5000 microg/rat 4-OHA was able to rescue embryos from death in the 30, but not 40, PMSG group. In the third experiment, the influence of the timing of 4-OHA treatment on its ability to improve the embryo count in hyperstimulated females was examined by introducing 4-OHA 24 h earlier, rather than at the time of hCG treatment. The results showed the importance of timing of 4-OHA administration, as 5000 microg/rat 4-OHA was able to restore embryo survival in the 40 PMSG hyperstimulated group only when it was administered 24 h before hCG injection. Together, these results highlighted that 4-OHA, when administered at the appropriate time and dose, could reverse the negative effects of hyperstimulation from PMSG on early embryonic development. This may be due to its potent aromatase inhibiting properties that lead to the suppression of oestrogen production, thereby alleviating the supraphysiological level of oestradiol, which is typically present in PMSG-treated females. Interestingly, 4-OHA treatment on its own was able to positively influence embryo count when given at a high dose of 5000 microg/rat, and this may be associated with its weak androgenic properties. In conclusion, this study supports the hypothesis that excessive oestradiol is responsible for the negative effects of hyperstimulation with PMSG on early embryonic development.

Effect of interval between two PGF 2α doses on superovulatory response and embryo recovery in crossbred sheep in tropics

An experiment was conducted to investigate the effects of different superovulatory regimes, including pregnant mare serum gonadotrophin (PMSG) and follicle-stimulating hormone (FSH-P) on steroidogenesis, oestrus, ovulation and premature luteal regression in sheep. Thirty mature Merino ewes were treated in the breeding season with intravaginal progestagen pessaries and 1200 IU PMSG (Group 1), 15 mg FSH-P (Group 2) or a combination of 700 IU PMSG and 11 mg FSH-P (PMSG/FSH-P; Group 3) to induce superovulation. After treatment with FSH-P alone, the incidence of oestrus was lower than after treatment with PMSG alone (6/10 vs. 10/10, P < 0.05) and the incidence of ovulation was lower than after treatment including PMSG (7/10 vs. 20/20, P < 0.05). However, there were no differences in the mean time to onset of oestrus (24.7 ± 2.3 h after pessary withdrawal) or the time to onset of ovulation (48–54 h after pessary withdrawal) between the treatment groups.The total ovarian response (corpora lutea + large follicles) was higher (P < 0.05) following stimulation with PMSG alone (17.1 ± 1.9) than with FSH-P (8.3 ± 12.5). However, the numbers of corpora lutea present on Day 6 (Day 0 = pessary withdrawal) were not affected by the exogenous gonadotrophin treatment (PMSG, 11.4 ± 1.8; FSH-P, 7.2 ± 2.5; PMSG/FSH-P, 11.1 ± 2.1; not significant). The mean pre-ovulatory peripheral plasma peak level of oestradiol-17β (E2) per follicle was higher following treatment with PMSG than with either of the other two regimes (PMSG, 23.2 ± 0.8 pg ml−1; FSHP, 10.8 ± 0.6 pg ml−1; PMSG/FSH-P, 13.9 ± 0.4 pg ml−1; P < 0.05). Moreover, E2 peaked earlier in the ewes treated with PMSG than with FSH-P or PMSG/FSH-P (7.6 ± 2.1 h vs. 33.7 ± 1.5 h and 24.8 ± 0.5 h respectively; P < 0.01). There were no differences detected in the peak levels of luteinizing hormone (LH) (8.6 ± 1.1 ng ml−1) or the mean time to LH peak (32 ± 1.4 h) between the ewes treated with the different exogenous gonadotrophins.Three ewes (one treated with PMSG alone and two with PMSG/FSH) had premature luteal regression by Day 6. In each case, a secondary peak of E2 secretion was observed 36–44 h after pessary withdrawal. These ewes each displayed a second oestrus on Days 5–6 and a mild superovulatory response at this oestrus.It is concluded that in sheep PMSG is highly steroidogenic in comparison with FSH-P. A combination of moderate doses of PMSG and FSH-P is a suitable superovulation regime for Merino ewes as it induces a consistently high superovulatory response without the secretion of excessive E2 levels. Perturbation of the periovulatory endocrine events may result in premature luteal regression.

Dose response effects of PMSG on ovulation rate and follicular development in Pelibuey ewes treated with Syncro-mate-B implants

The effect of dose of pregnant mare serum gonadotropin (PMSG) was determined on the superovulatory response and follicular development in 50 cycling, mature Pelibuey ewes following treatment with Syncro-mate-B (SMB) implants. A randomized complete block design with five treatments was utilized; all ewes were treated for 10 days with SMB implants and at the end of the treatment, groups of 10 ewes each were randomly allocated and treated with 1-500, 2-1000, 3-2000, 4-3000 or 5-4000 IU of PMSG, 24 h prior to SMB removal. Ovarian responses were recorded as the number of corpora lutea (CL) and the number and size of follicles present 5–6 days after estrus, by means of a midventral laparotomy. The percentage of ewes responding to treatment, determined by the presence of unovulated follicles, was significantly different ( p<0.01) among treatments, these values were 50, 60, 90, 80 and 100%, respectively, for the groups 1–5. The number of unovulated follicles was also different ( p<0.05), among the treatment groups, the corresponding means (±SEM) were 0.7±0.63, 2.4±4.07, 8.0±4.7, 9.4±7.03 and 9.0±5.6 follicles per ewe, respectively, for the treatment groups 1–5. The overall percentage of ewes ovulating was 80%. The percentage of ewes ovulating at least once per group was also different ( p<0.01) among the treatment groups, the corresponding values per group were 70, 60, 100, 80 and 90%; whereas the percentage of ewes ovulating at least twice was 48% and the corresponding treatment group values were 30, 20, 80, 60 and 50%, respectively. These values were significantly different ( p<0.01). The mean number of CL for the ewes with two or more CL among the treatment groups was different ( p<0.05); the values being 1.5±2.4, 1.0±2.1, 6.9±6.1, 4.4±4.2 and 4.6±5.4 CL per ewe. It is concluded from these results, that Pelibuey ewes can be effectively superovulated with a dose of PMSG of 2000 IU.

Follicular atresia as an apoptotic process: Atresia-associated increase in the ovarian expression of the putative apoptotic marker sulfated glycoprotein-2

To evaluate the possibility that morphologically confirmed/hypophysectomy-induced ovarian follicular atresia, a putative apoptotic process, is coupled to alterations in the steady-state levels of ovarian sulfated glycoprotein-2 (SGP-2) transcripts. Hypophysectomy-induced follicular atresia in immature rats, morphologically confirmed at the light and electron microscopic levels, was correlated with alterations in the steady-state levels of ovarian SGP-2 transcripts as assessed by a solution hybridization/RNase protection assay. Cellular localization was accomplished by in situ hybridization technology. Hypophysectomy of the 24-day-old immature rat, an established precipitant of follicular atresia, led (3 days later) to a significant (P < .05) increase (up to 3.3-fold) in the relative abundance of densitometrically quantified ovarian SGP-2 transcripts compared with age-matched intact controls. Detailed time-course analysis after hypophysectomy revealed significantly (P < .05) increased ovarian SGP-2 mRNA expression as early as 2 days after hypophysectomy; no further increments were noted on days 4 or 8. Light microscopic analysis of comparable ovarian material 4 days after hypophysectomy revealed increased numbers of atretic follicles displaying large numbers of degenerating granulosa cells. Electron microscopic analysis of the degenerating cells of atretic follicles (from hypophysectomized rats) disclosed nuclear condensation and cytoplasmic shrinkage as well as apoptotic bodies at all levels of the granulosa cell layer. In situ hybridization established the granulosa cell of the intact untreated rat as the somatic cell concerned with SGP-2 gene expression. In turn, hypophysectomy led to an increase in SGP-2 expression at the level of the theca-interstitial cell, an effect prevented by the concurrent provision of pregnant mare serum gonadotropin (PMSG). The hypophysectomy-induced increase in ovarian SGP-2 transcripts was similarly reversed (54% inhibition by day 27) by the concomitant provision of FSH, an established antiatretic principle. The delayed administration (day 26) of a single dose of PMSG to rats hypophysectomized on day 24 eliminated the hypophysectomy-induced increase in ovarian SGP-2 transcripts as assessed on day 28. Qualitatively similar but quantitatively more pronounced increments in ovarian SGP-2 gene expression were obtained when atresia was induced by hypophysectomy of PMSG-primed immature rats. These observations establish the immature rat ovary as a site of SGP-2 gene expression and reveal hypophysectomy-induced follicular atresia to result in the up-regulation of ovarian (specifically, theca-interstitial) SGP-2 gene expression, an effect prevented by the concurrent provision of FSH or PMSG. To the extent that SGP-2 is an acceptable apoptotic marker, the present findings support the hypothesis that ovarian follicular atresia may be an apoptotic process.

Induction of breeding in anoestrous crossbred ewes with progestagen and PMSG with or without prior immunisation against an androstenedione-protein conjugate

Results are presented of an investigation into the potential value of immunisation of anoestrous ewes with androstenedione-7-HSA, using a commercial preparation (Fecundin; PitmandashMoore, Australia) prior to treatment with intravaginal sponges impregnated with fluorogestone acetate (Cronolone; Searle) and Pregnant Mare Serum Gonadotrophin (PMSG) for out-of-season breeding. Five experiments, involving treatment of 1292 ewes in various physiological states, were conducted during one anoestrous period of 4 months. Factors introduced were: whether or not immunised; interval from booster dose to mating; and dose of PMSG. The ewes were in three stages of anoestrus, namely early, middle or late. Other associated factors were whether or not they were suckling lambs (lactating) and stage of lactation. In early anoestrus, ewes in early lactation were difficult to impregnate compared with maiden ewes (30.6% vs. 51.9% ewes lambed). In mid-anoestrus, ewes in mid-lactation were comparable with maiden ewes (60.6% lambed). In late anoestrus, by which time most lambs had been weaned, 64.3% lambed. The response to immunisation varied with the time from the booster injection to that of the induced oestrus. A 13–14-day interval was too short and had deleterious effects. At 48 days, there were no deleterious effects and a slight residual beneficial effect on lambing performance. An interval of 21 days was much more effective. It had little effect on the time of onset of oestrus, markedly increased the ovulation rate, did not reduce the percentage ewes that lambed, and resulted in a 47% increase in lambs born to ewes in late lactation or from which lambs had recently been weaned. Immunised ewes consistently shed more ova than did nondashimmunised ewes, and this difference increased with increasing doses of PMSG, raising the question of the potential value of immunised animals as donors in embryo transplant programmes. The use of immunisation in a controlled breeding programme requires evaluation of each particular circumstance. There are potential advantages in terms of increased lambs born but the programme needs to be carefully timed.

Ovulatory activity, hormonal induction of ovulation and fertility of young Cashmere and Angora female goats in a temperate environment.

Reproductive parameters of young Cashmere and Angora goats born between 1988 and 1990 and grazed on temperate pastures in southern Australia were examined with a view to reducing the age of first breeding. Females born in August or October of 1989 and 1990 were examined each month by laparoscopy to determine natural ovulatory activity when 6-19-months old. Cashmeres commenced ovulating as young as 7 months of age or as light as 12 kg. Almost all Cashmeres were ovulating by 8-10 months of age at a liveweight of at least 18 kg, and their breeding season extended from April to October. By comparison with Cashmeres, Angoras grew more slowly, fewer ovulated, they commenced ovulation later, their ovulation rates were lower and their breeding season was shorter. A stratified sample of these females was injected with 200 I.U. or 400 I.U. of pregnant mare serum gonadotrophin (PMSG) after treatment with controlled internal drug release (CIDR) devices for 16-18 days to induce ovulation at 6, 9, 12, 15 and 19 months of age. Ovulation rates after CIDR-PMSG treatment were higher for Cashmeres than for Angoras and tended to be higher for females injected with 400 I.U. PMSG than 200 I.U. PMSG. The proportion of females remaining anovulatory after exogenous hormonal treatment was higher for Angoras than for Cashmeres (38% and 10% respectively) but it was not affected by the dose of PMSG or age. For kids born in 1989, the kidding rates to insemination (with follow-up mating) after CIDR-PMSG treatment for 8-month-old and 20-month-old Cashmeres (in the breeding season) were similar (75.0% and 83.8% respectively) but the rate for 14-month-old Cashmeres was only 10.0% (in the non-breeding period). The kidding rates for Angoras bred at 8, 14 and 20 months of age were 8.4%, 20.0% and 30.0% respectively. Ovulatory activity and fertility in the non-breeding period, with or without CIDR-PMSG treatment, did not improve with melatonin treatment.