IU PMSG Research Articles

Reproductive performances in ewe lambs of the Queue Fine de l’Ouest breed and their D’Man crosses following synchronisation

In order to study the reproductive response to a synchronising hormonal treatment, oestrus, fertility and litter size were compared among 44 Queue Fine de l’Ouest (QFO) ewe lambs and 44 D’Man× QFO contemporaries run in a single flock under natural grazing conditions. Within breed, animals were divided into two groups (balanced for live weight) of 22 ewes, each induced to breed at 9 months of age after being treated with intravaginal progestagen and 200 or 400 IU PMSG, respectively, in groups 1 or 2. Throughout the 45 days mating period, ewes in oestrus were mated by Noire de Thibar rams. The hormonal treatment was effective in inducing oestrus in over 90% of the ewes. At the induced ovulation, the breed and the dose of PMSG did not affect either the number of animals exhibiting oestrous behaviour, or allowing mating. After the mating period, breed had a significant effect on fertility, with lambing rates of 93 and 66% for ewes of the D’Man× QFO and QFO breeds, respectively. Breed also significantly affected the proportions of females lambing when conception occurred at the induced oestrus. Though not significant, ewe lambs of both breeds receiving 400 IU PMSG produced 16% more lambs than those treated with the lower dose of 200 IU. With a dose of 200 IU PMSG, ewe lambs of the D’Man× QFO breed tended to yield a higher litter size than the QFO contemporaries (1.2±0.40 vs. 1.1±0.26). Globally, the results showed that attempts to breed from ewe lambs of the D’Man× QFO breed under the conditions described here are likely to lead to more satisfactory conception rates than in the case of the autochthonous QFO breed.

Synchronisation of oestrus in goats: the use of different progestagen treatments

The efficiency of medroxyprogesterone acetate (MAP), fluorogestone acetate (FGA) sponges and controlled internal drug release (CIDR) devices for synchronising oestrus in goats was evaluated during the natural breeding season. Ninety does (42 boer goat and 48 indigenous goats) were assigned to Group A ( n=30) 60 mg MAP, Group B ( n=30) 40 mg FGA and Group C ( n=30) CIDR devices. Intravaginal progestagen was administered for a 16-day period. Upon progestagen withdrawal, does received 300 IU PMSG intramuscularly. Cervical inseminations with fresh diluted semen at a fixed time (48 and 60 h) followed progestagen withdrawal. The three progestagen treatments did not show significant differences in oestrous response (97%) and duration (33.3±13.4) of the induced oestrous period. Time to the onset of oestrus significantly advanced in the CIDR (27.2±0.4 h) group, when compared to FGA the (30.9±0.4 h) and MAP (32.2±0.5 h) groups. The mean serum progesterone concentrations in the CIDR group were higher ( P<0.05) between days 4 and 16 of progestagen treatment, compared to the MAP and FGA groups. No significant difference was observed with respect to pregnancy rate 40 days after AI (52, 60 and 47% for CIDR, MAP and FGA groups, respectively). Results indicate that the use of MAP, FGA and CIDR intravaginal progestagen treatments are equally efficient in synchronising oestrus in goats.

Follicular and oocyte development in gilts of different age.

The aim of the present study was to estimate follicular and oocyte development of the same gilts in three phases of their reproductive life--prepuberal gilt (6 months old), cycling gilt (9.5 months old) and primiparous sow. Follicular development was induced by injections of 1000 IU PMSG followed by 500 IU hCG 72 h later. Cumulus-oocyte-complexes (COCs) were recovered from preovulatory follicles of the left ovary, and follicular fluid (FF) from the right ovary always 34 h after hCG by endoscopy. Altogether, 19 gilts were used in the prepuberal (P) and cycling (C) trials and 12 of them in the primiparous trial (S). Altogether 168, 190 and 82 follicles were aspirated from the left ovary and 106, 125 and 42 COCs recovered (recovery rate 60.5 +/- 26.9, 62.7 +/- 20.9 and 52.9 +/- 21.8%). The average number of follicles was higher in C compared to P (19.7 +/- 6.8 vs. 15.7 +/- 6.8, p = 0.06) and to S (14.2 +/- 4.0, p < 0.05), respectively. More uniform expanded COCs were aspirated from prepuberal and cycling gilts as compared to sows (89.7 and 78.4% vs. 46.3%, p < 0.05). Furthermore, the meiotic configuration in oocytes differed (p < 0.05) between these groups (55.5 and 61.7% vs. 0% Telo 1/Meta 2). Concentrations of progesterone in FF decreased (p < 0.05) from 590.0 +/- 333.6 (P) to 249.1 +/- 72.6 (C) and 161.4 +/- 75.2 ng/ml (S). FF concentrations of oestradiol-17 beta were different between gilts and sows (9.3 +/- 2.9, 21.9 +/- 10.6 and 94.0 +/- 15.9 pg/ml, p < 0.05). The progesterone/oestradiol ratio was 72.1, 15.2 and 4.7. Results indicate a different follicular and oocyte development during the investigated lifetime periods. Cycling gilts should preferably be used in IVF and breeding programs. The lower reproductive potential of primiparous sows is taken into consideration at breeding. Prediction of lifetime performance based on individual ovarian reaction of prepuberal gilts is unsuitable.

Protocols for Estrus Synchronization in Awassi Ewes under Arid Environmental Conditions

In July, three trials were conducted to evaluate the best sponge type and optimum PMSG dose to be administered to sheep under the Jordanian Badia (arid) conditions. In trial 1, three flocks (n=77, n=18 and n=47 for flocks 1, 2 and 3, respectively) were administered with 40 mg fluorogestone acetate (FGA) intravaginal sponges for 12 days before receiving 600 IU of PMSG at the time of sponge removal. In trial 2, 95 ewes were assigned to 4 groups to receive 300 (n=25), 450 (n=27), 600 (n=22) or 750 (n=21) IU of PMSG following a 12 d FGA 40 mg sponge insertion period. In trial 3, 60 ewes were assigned to 3 groups (n=20) to receive either FGA 30 mg, FGA 40 mg or medroxyprogesterone acetate (MAP) 60 mg intravaginal sponges all followed by an administration of 600 IU of PMSG at sponge removal. In all trials, rams were isolated 1 day before sponge insertion and were allowed back with the ewes at sponge removal. Estrual responses and lambing data were collected. The effects of treatment, milking status and face color on estrual responses and lambing data were examined. In trial 1, greater first cycle conception rate (p0.05). Despite low lambing rate in trial 2, ewes receiving 600 IU of PMSG had greater (p3.1, 493.1 and 493.1 h post sponge removal in ewes receiving MAP 60 mg, FGA 30 mg and FGA 40 mg sponges, respectively). Other parameters were not influenced (p>0.05) by sponge type, milking status and face color. Data show that a 600 IU dose of PMSG tends to give the best lambing results. In addition, results indicate that the use 60 mg MAP sponges for estrus synchronization may be more appropriate under the Jordanian Badia conditions during late seasonal anestrus.

Reproductive Responses of Awassi Ewes Treated with either Naturally Occurring Progesterone or Synthetic Progestagen

The objective was to identify the appropriate form of progesterone, which exhibits compact reproductive responses in Awassi ewes during mid to late seasonal anestrous period. Forty-eight Awassi ewes were randomly allocated into four groups to be treated with 60 mg medroxyprogesterone acetate (MAP), 30 mg fluorogestone acetate (FGA), 40 mg FGA, or 600 mg progesterone sponges. After a 12 day period, sponges were removed and ewes were administered i.m. with 600 IU PMSG (d 0, 0 h). Five harnessed Awassi rams were turned-in with the ewes to detect heat. Ewes were checked for breeding marks at 6 h intervals for 5 days. Blood samples were collected from all ewes for analysis of progesterone concentrations. Pretreatment (d -13 and -12) progesterone concentrations were ≤0.2 ng/mL among all ewes and were indicative of seasonal anestrous period. On d 0, progesterone concentrations were elevated to 1.4±0.1 ng/mL in ewes received progesterone sponges only and were higher (p 0.1) among all ewes. Incidence of estrus was similar (p>0.1) among the four groups and occurred in 75% (9/12), 82% (9/11), 67% (8/12) and 58% (7/12) of the ewes receiving MAP, 30 mg FGA, 40 mg FGA and progesterone sponges, respectively. Estrous responses occurred 14.7, 20 and 13.6 h earlier in progesterone-sponge-treated ewes than those of MAP- (p 0.1) among ewes of the four treatment groups. Ewes that returned to estrus 16 to 20 days following d 0 were 5/12, 5/11, 6/12 and 4/12 ewes treated with MAP, 30 mg FGA, 40 mg FGA and progesterone sponges, respectively, and all lambed 169 days later. Overall lambing rates were 75% (9/12), 82% (9/11), 75% (9/12) and 58% (7/12) ewes treated with MAP, 30 mg FGA, 40 mg FGA and progesterone sponges, respectively. Results demonstrate that applications of MAP, 30 mg FGA, 40 mg FGA and progesterone sponges Awassi ewes were equally effective in induction of estrus and tended to favor both types of FGA and MAP in overall lambing rates over progesterone sponges during the seasonal anestrous period. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 9 : 1257-1262)

Follicular development and preovulatory oocyte maturation in Hungarian Mangalica and Landrace gilts

Abstract. Preservation of native pig breeds of different values has got increasing public interest. Hungarian Mangalica, likewise other native races, became uninteresting because of economic reasons or other characteristics, and were replaced by modern breeds. Its population decreased rapidly and reached a critical level. However, the exceptional taste of the meat, and the robustness and motherliness do support the propagation of this breed. Nevertheless, low prolificacy and marked seasonality remains a problem. The aim ofthe present study was to find possible implications of the physiological basis with regard to the low fecundity. Therefore, preovulatory follicular development and intrafollicular oocyte maturation of Mangalica and of Landrace gilts were compared. A total of 18 pubertal Blond and Swallow Belly Mangalica and 19 Landrace gilts (8.5 to 9 month of age, body weight of 120 to 125 kg) were used. Oestrus of gilts was synchronized by feeding Regumate®, follicular growth was stimulated by administering 1,000 IU PMSG 24 h after the last Regumate® feeding and the LH peak simulated with 750 IU hCG 80 h after PMSG. Cumulus-oocyte-complexes (COCs) were recovered 34 h after hCG by endoscopic Ovum Pick Up. Follicular fluids from follicles per ovary were pooled and the morphology of COCs was determined. COCs were classified as compact, expanded or denuded. Thereafter, COCs were prepared for evaluation of nuclear configuration. Based on their nuclear status the oocytes were classified as 1) immature – germinal vesicle (GV), with diplotene chromatin; 2) meiosis resumed – G V breakdown, diakinesis, M-I to A-I; or 3) mature – T-I and M-II. The average number (+SD) of preovulatory follicles was 6.8 + 1.4 in Mangalica and 19.6 ± 6.6 in Landrace gilts (p&lt;0.05). Differences were obtained conceming the morphology of recovered COCs between breeds. The per cent of oocytes with compact cumulus was higher in Mangalica compared to Landrace gilts (31 vs. 16 %) but less oocytes possess expanded cumulus (62 vs. 78 %, p&lt;0.05). The meiotic configuration of oocytes was unlike between Mangalica and Landrace gilts. The rate of oocytes with mature chromatin configuration (Telophase I /Metaphase II) was higher (27 vs. 62 %, p&lt;0.05) in Landrace sows. It is assumed that both diminished follicular development and protracted intrafollicular oocyte maturation may be involved in low fecundity in Mangalica.

Ovarian response, embryo recovery and results of embryo transfer in a hungarian native pig breed

The objective of the study was to use embryo transfer (ET) for propagation of the Swallow Belly Mangalica population. Mangalica is a native Hungarian pig breed adapted to extreme climate and housing conditions and distinguished for excellent meat and fat quality. However, due to their weak reproductive characteristics and relatively high fat proportion, Mangalica pigs have been replaced by modern breeds. Now, there is an increased interest again to safeguard the properties of this breed. We conducted two experiments. First, we used a total of 18 puberal Mangalica gilts to determine an optimal superovulatory treatment. Following estrus synchronization with Regumate®, we injected gilts with either 750, 1000 or 1250 IU PMSG, followed by 750 IU hCG 80 h later. We scanned ovaries endoscopically 3 days after hCG administration. The application of 1000 and 1250 IU PMSG resulted in a higher rate of ovulation compared to 750 IU (24.2 ± 3.6 and 21.0 ± 2.3 vs. 13.7 ± 2.7 P<0.05). The number of follicular cysts increased after administration of 1250 IU PMSG compared to 750 and 1000 IU (2.0 ± 1.3 vs. 0.3 ± 0.7 and 0.2 ± 0.3, P<0.05). Thus, we chose 1000 IU PMSG for further stimulation of Mangalica gilts. In the second experiment, we induced superovulation in 10 Mangalica donor gilts by 1000 IU PMSG and 750 IU hCG. Gilts were fixed-time inseminated, and then five days later embryo collection was carried out surgically (n=6) or endoscopically (n=4). Out of the 187 ova recovered, 92.5% were at the morula/blastocyst stage. The embryo recovery rate was higher following surgical flushing than following endoscopy (91.5 ± 4.4% vs. 71.4 ± 12.7%, P<0.05). Altogether 143 embryos were transferred surgically or endoscopically into 8 Landrace recipients. Surgical and endoscopic transfer of Mangalica embryos into Landrace gilts resulted in pregnancies in 3 and 2 gilts, respectively; thus the overall farrowing rate was 62.5%. The birth of 59 Mangalica piglets from 5 embryo recipients equals an average litter size of 11.8 ± 1.3, which is two times larger than usual in this breed. Therefore, we concluded that an appropriate inter-breed ET program is a suitable tool to propagate the endangered Mangalica breed.

Reduced ovulation rate and cytogenetic analysis following tyrosine phosphatase inhibition in mouse oocytes.

Objective: To investigate the effects of sodium orthovanadate (NaV)-induced tyrosine phosphatase inhibition on ovulation rate and aneuploidy during mouse oocyte maturation (OM). Design: A controlled NaV dose response cytogenetic study involving ovulated mouse oocytes. Materials/Methods: ICR female mice were superovulated with intraperitoneal injections of 10.0 IU PMSG and 5.0 IU hCG 48 hrs later. NaV was given immediately after hCG. Ovulated oocytes were collected and counted 16 hrs after hCG and processed for cytogenetic analysis. Based on preliminary cell and animal toxicity data, NaV doses of 5, 15, and 25 mg/kg were selected. Controls received the solvent distilled water. Chromosomes were C-banded to distinguish between complete dyads (chromosomes) and those separated into two chromatids. Data were analyzed by Chi-square and Fisher’s Exact tests. Results: NaV-induced tyrosine phosphatase inhibition led to a significant reduction in the number of oocytes ovulated but did not increase the frequencies of cytogenetic aberrations. The number of oocytes ovulated per number of females for the control group (535/20, 26.8%) was significantly (p < 0.01) greater than that in the 5 mg/kg NaV group (372/20, 18.6%), the 15 mg/kg NaV group (365/20, 18.3%), and the 25 mg/kg NaV group (537/30, 17.9%). The frequencies of hypoploidy (n = 10–19), hyperploidy (n = 20–29), premature centromere separation, premature anaphase, and single chromatids were neither significantly (p 0.05) different between the controls and each of the NaV groups nor among the NaV groups. Ovulated MI oocytes, diploid oocytes, and structural chromosome aberrations were not found. Conclusions: These in vivo oocyte data appear unique in the literature. Although phosphatase and kinase activities are essential for oocyte maturation, the tyrosine phosphatase inhibitor, NaV, did not alter the temporal sequence of OM and increase the frequency of numerical or structural chromosome aberrations. However, NaV-inhibition of tyrosine phosphatase activity resulted in a significant decrease in the number of mouse ovulated oocytes. Supported by: Department of Obstetrics and Gynecology, Louisiana State University Health Sciences Center, Shreveport, LA.

Sincronização da ovulação em fêmeas suínas submetidas ao desmame precoce

Verificou-se a eficiência de protocolos para sincronizar a ovulação em porcas desmamadas precocemente. Trinta porcas com média de 4,4± 2,0 partos e estádio de lactação de 14,8± 0,7 dias foram distribuídas em três grupos de 10 animais: 1- nenhum tratamento hormonal; 2- 1000 UI de PMSG, via intramuscular (IM), 48h pós-desmame e 0,25mg de GnRH, IM, 72h após a aplicação do PMSG; 3- 1000 UI de PMSG, IM, 48h pós-desmame e 500 UI de hCG, IM, 72h após o PMSG. O momento da ovulação foi detectado por ultra-sonografia transretal. A taxa de sincronização (ovulação até 48h após aplicação de hCG ou GnRH) dos grupos 2 e 3 (94,7%) foi maior (P&lt;0,01) que no grupo controle (40%). Com o uso dos protocolos de sincronização de ovulação, as fêmeas tratadas apresentaram, em relação ao grupo controle, tendência de maior taxa de prenhez (95% vs. 70%; P&lt;0,10) e similares intervalo do desmame ao estro (96,5± 3,0 vs. 130,2± 31,4h) e número de leitões nascidos vivos por fêmea gestante no primeiro cio pós-desmame (10,9± 0,8 vs. 12,0± 0,9). Dessa maneira, os protocolos de sincronização usados neste estudo foram eficientes em sincronizar a ovulação, e podem viabilizar o uso da inseminação artificial em horários predeterminados.

Chemical properties of bovine cervical mucus during normal estrus and estrus induced by progesterone and/or PGF2α

Ninety-two Friesian cows were used to determine the chemical properties of cervical mucus during normal estrus and estrus induced by progesterone (P 4)-releasing intravaginal devices (PRID) and/or prostaglandin F2α. The animals were assigned to 4 groups (no treatment, a PRID for 12 days plus injection of 1000 IU PMSG at the removal of PRID, a double im injection of PGF 2α 11 days apart, or PRID for 7 days plus an im injection of PGF 2α 24 h before the removal of PRID). A number of cows with normal estrus exhibit three consecutive estrous cycles after delivery. Cows that had not shown estrus for 3 months after delivery had their ovaries palpated twice at 10-day intervals, to determine their ovarian activity. Then PRID and/or PGF2α was administered in cows that had a palpable corpus luteum in one of the two palpations (cyclic cows). A double artificial insemination (AI) was performed to the cows of the three induced-estrus groups, while the cows with normal estrus received only one AI. Cervical mucus samples were collected from all cows 5 to 30 min before the first AI. Additionally, samples of cervical mucus were collected from 20 cows during their first estrus after the induced one. The results are summarized as follows: 1) The biochemical properties of cervical mucus in the first three estrus periods after delivery were similar. 2) These properties were similar both in normal estrus after delivery and in the first estrus after an induced one. 3) Glucose and fructose concentrations for normal estrus were similar to those for induced estrus groups. 4) Total protein and cholesterol concentrations were significantly lower (P < 0.001) in normal than in induced estrus, while no difference was found among the induced estrus groups. 5) Pregnancy rates of the cows did not differ significantly among the normal and the induced-estrus groups. 6) The percentages of cows in the induced-estrus groups that produced cervical mucus with total protein and cholesterol concentrations similar to those for the normal estrus groups was very low.

Alterations in follicle development, steroidogenesis, and gonadotropin receptor binding in a model of ovulatory blockade.

Immature female rats treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) before gonadotropin-induced follicle development and ovulation ovulate significantly fewer ova compared with controls. This study was designed to investigate potential ovarian-specific mechanisms of TCDD-mediated inhibition of ovulation. Immature hypophysectomized rats were treated with TCDD (32 microg/kg) or corn oil vehicle. Follicle development was initiated by injection of 10 IU PMSG 24 h after TCDD, and ovulation was induced 52 h after PMSG by injection of 10 IU hCG. The number of ova flushed from the oviduct was assessed the morning after hCG injection, and ovaries were collected at multiple times throughout the treatment schedule for histological analysis and analysis of FSH and hCG receptor binding and ovarian cAMP levels. In addition, serum levels of estradiol and progesterone were determined. Control rats ovulated 9.3 +/- 1.5 ova, whereas TCDD-treated rats ovulated 0.6 +/- 0.3. Gonadotropin receptor binding was evaluated 52 h after PMSG at the usual time of hCG injection to induce ovulation. Both FSH binding and hCG binding were significantly reduced in animals treated with TCDD. Serum estradiol levels in control animals were increased by 52 h after PMSG administration. In contrast, serum levels of estradiol in TCDD-treated animals remained low. In response to the ovulatory dose of hCG, serum levels of both estradiol and progesterone increased in control animals. Steroid levels also increased in TCDD-treated animals, but did not reach the peak levels observed in controls. TCDD treatment further resulted in lower ovarian cAMP levels at 52 h post-PMSG and at 5 h post-hCG. Together the data indicate that TCDD treatment altered the ability of the ovary to respond to PMSG, resulting in the development of follicles not comparable to controls (lower gonadotropin binding, lower estradiol production, lower levels of cAMP). It appears that critical steps in the development and maturation of follicles are disrupted by TCDD.

Alterations in Follicle Development, Steroidogenesis, and Gonadotropin Receptor Binding in a Model of Ovulatory Blockade

Immature female rats treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) before gonadotropin-induced follicle development and ovulation ovulate significantly fewer ova compared with controls. This study was designed to investigate potential ovarian-specific mechanisms of TCDD-mediated inhibition of ovulation. Immature hypophysectomized rats were treated with TCDD (32 μg/kg) or corn oil vehicle. Follicle development was initiated by injection of 10 IU PMSG 24 h after TCDD, and ovulation was induced 52 h after PMSG by injection of 10 IU hCG. The number of ova flushed from the oviduct was assessed the morning after hCG injection, and ovaries were collected at multiple times throughout the treatment schedule for histological analysis and analysis of FSH and hCG receptor binding and ovarian cAMP levels. In addition, serum levels of estradiol and progesterone were determined. Control rats ovulated 9.3 ± 1.5 ova, whereas TCDD-treated rats ovulated 0.6 ± 0.3. Gonadotropin receptor binding was evaluated 52 h after PMSG at the usual time of hCG injection to induce ovulation. Both FSH binding and hCG binding were significantly reduced in animals treated with TCDD. Serum estradiol levels in control animals were increased by 52 h after PMSG administration. In contrast, serum levels of estradiol in TCDD-treated animals remained low. In response to the ovulatory dose of hCG, serum levels of both estradiol and progesterone increased in control animals. Steroid levels also increased in TCDD-treated animals, but did not reach the peak levels observed in controls. TCDD treatment further resulted in lower ovarian cAMP levels at 52 h post-PMSG and at 5 h post-hCG. Together the data indicate that TCDD treatment altered the ability of the ovary to respond to PMSG, resulting in the development of follicles not comparable to controls (lower gonadotropin binding, lower estradiol production, lower levels of cAMP). It appears that critical steps in the development and maturation of follicles are disrupted by TCDD.

Alteration of gonadotrophin and steroid hormone release, and of ovarian function by a GnRH antagonist in gilts

This study examined the impact of the gonadotrophin-releasing hormone (GnRH) antagonist Antarelix™ on LH, FSH, ovarian steroid hormone secretion, follicular development and pituitary response to LHRH in cycling gilts. Oestrous cycle of 24 Landrace gilts was synchronised with Regumate ® (for 15 days) followed by 800 IU PMSG 24 h later. In experiment 1, Antarelix™ ( n=6 gilts) was injected i.v. (0.5 mg per injection) twice daily on four consecutive days from day 3 to 6 (day 0=last day of Regumate ® feeding). Control gilts ( n=6) received saline. Blood was sampled daily, and every 20 min for 6 h on days 2, 4, 6, 8 and 10. In experiment 2, gilts ( n=12) were assigned to the following treatments: Antarelix™; Antarelix™ + 50 μg LHRH on day 4; Antarelix™ + 150 μg LHRH on day 4 or control, 50 μg LHRH only on day 4. Blood samples were collected daily and every 20 min for 6 h on days 2, 4 and 6 to assess LH pulsatility. Ovarian follicular development was evaluated at slaughter. Antarelix™ suppressed ( P<0.05) serum LH concentrations. The amount of LH released on days 4–9 (experiment 1) was 8.80 versus 36.54 ng ml −1 (S.E.M.=6.54). The pattern of FSH, and the preovulatory oestradiol rise was not affected by GnRH antagonist. Suppression of LH resulted in a failure ( P<0.05) of postovulatory progesterone secretion. Exogenous LHRH (experiment 2) induced a preovulatory-like LH peak, however in Antarelix™ treated gilts the LH surge started earlier and its duration was less compared to controls ( P<0.01). Furthermore, the amount of LH released from day 4 to 5 was lower ( P<0.01) in Antarelix™, Antarelix™ + 50 and Antarelix™ + 150 treated animals compared to controls. No differences were estimated in the number of LH pulses between days and treatment. Pulsatile FSH was not affected by treatment. Mean basal LH levels were lower ( P<0.05) after antagonist treatment compared to controls. Antarelix™ blocked the preovulatory LH surge and ovulation, but the effects of Antarelix™ were reduced by exogenous LHRH treatment. The development of follicles larger than 4 mm was suppressed ( P<0.05) by antagonist treatment. In conclusion, Antarelix™ treatment during the follicular phase blocked preovulatory LH surge, while FSH and oestradiol secretion were not affected. Antarelix™ failed to alter pulsatile LH and FSH secretor or pituitary responsiveness to LHRH during the preovulatory period.

Effect of the stage of pregnancy and post-partum on the number of gonadotrophin responsive follicles in ewes

The present study was designed to study follicular growth and its interactions with the corpus luteum of pregnancy in sheep during early, middle and late pregnancy and during postpartum anestrus. Ewes with 1 or 2 corpora lutea in one ovary were selected from a larger group of Serres ewes. All pregnant ewes were randomly allocated to two groups, with 10 to 12 ewes per group. Ewes of Group I were treated with 750 IU hCG at Day 25 or 45 or 70 or 100 or 125 of pregnancy. In Group II, ewes were treated with a combination of 1000 IU PMSG + 750 IU hCG either at Day 25 or 45 or 70 or 100 of pregnancy. The results demonstrated the presence of gonadotrophin-responsive follicles during early pregnancy (Days 25 to 45), reduction of their number during mid-pregnancy (Days 70 to 100), and their disappearance during late pregnancy (Day 125). Administration of hCG to Serres ewes at 10 and 290 days postpartum induced ovulation of a high proportion of ewes at 10 days postpartum (62%) with a further increase observed at 20 days postpartum (75%). During pregrancy, as well as during the postpartum period, there was no significant difference in the number of ovulations induced according to the location of the corpus luteum of pregnancy. These data demonstrate that the presence of the corpus luteum of pregnancy does not affect the number of gonadotrophin-responsive follicles until Day 100 of pregnancy. However, during late pregnancy such follicles were no longer present in the ovaries. Gonadotrophin-responsive follicles were again present as soon as Day 10 postpartum.

Physical properties of bovine cervical mucus during normal and induced (progesterone and/or PGF2α) estrus

Ninety two Friesian cows were used to determine physical properties of cervical mucus collected during normal estrus and estrus induced. Estrus was induced using either progesterone (P 4) releasing intravaginal devices (PRID) and/or prostaglandin F2α (PGF2α). The animals were assigned to 4 groups (no treatment, a PRID for 12 days plus an injection of 1000 IU PMSG at the removal of the PRID, a double injection of 3 mL PGF2α 11 days apart, and a PRID for 7 days plus an injection of PGF2α 24 h before the removal of PRID). A number of cows with normal estrus exhibited three consecutive estrus cycles after calving. Cows that had not shown estrus for three months after calving had their reproductive system palpated twice at 10-day intervals, to determine their ovarian activity. Then PRID and/or PGF2α was administered to cows that were found to have a palpable corpus luteum in one of two palpations (cycling cows). The cows of the three induced estrous groups were artificially inseminated (AI) twice, while those with normal estrus received only a single AI. Cervical mucus samples were collected from all cows 5 to 30 min before the first AI. Additionally, samples of cervical mucus were collected from 20 cows at their first estrus after the induced estrus. The results are summarized as follows: 1) The physical properties of cervical mucus were similar in the first three normal consecutive estrus cycles after calving. 2) The physical properties of cervical mucus in normal estrus after calving were similar to those in the first estrus after an induced estrus. 3) The pH values for normal estrus were similar to those for induced estrus. 4) Viscosity of cervical mucus in the normal estrous group was significantly lower than that in the induced estrus. Furthermore, significant differences were noticed among the three induced estrous groups. 5) Spinnbarkeit, crystallization and receptivity of cervical mucus (penetration test) were significantly higher in the normal estrous group than in the induced estrous groups, while no difference was detected among induced estrus groups. 6) Pregnancy rates in physical properties of cervical mucus at the time of the second AI were similar to those for normal estrus but this suggestion needs further investigation. On the other hand, at the time of the first AI very few cows in the induced estrus groups produced cervical mucus similar to that of cows with normal estrus. The physical properties that differed the most were viscosity, spinnbarkeit, and the penetration test. Other authors found that cows do not exhibit estrus at the same determined time (11,26). On the basis of this finding physical properties of cervical mucus could be used as an indicator for the time of estrus manifestation, in order to increase pregnancy rates by applying AI at an optimal time. In summary, the results from the present study showed that the physical properties of cervical mucus in the first three consecutive normal estrous periods after calving are similar; that the first estrus after an induced estrus is a normal estrus; that viscosity, spinnbarkeit, crystallization and receptivity of cervical mucus (penetration test) are significantly different for normal than for induced-estrus groups at the time of first AI; and a small percentage of cows with induced estrus produce cervical mucus with parameters of viscosity, spinnbarkeit and receptivity similar to those found in normal estrus. These properties could be used as indicators for the quality of cervical mucus produced by the cows with induced estrus.

Ram seminal plasma and fertility: results from an ongoing field study.

The effects of partial replacement of ram semen diluent with ram seminal plasma on the fertility of ewes were studied. Crossbred Chios ewes (n = 152) were assigned to six groups. The oestrous cycles of the ewes were synchronised at the peak (Groups A, B, C and D) and at the end (Groups E and F) of the breeding season by means of intravaginal sponges impregnated with fluorogestone acetate (FGA) for 14 days. Four hundred IU of PMSG were injected intramuscularly at the time of sponge removal. Ewes of Groups A, C and E were artificially inseminated with ram semen diluted with skim milk extender, while those of Groups B, D and F with ram semen diluted with 50% skim milk and 50% ram seminal plasma. The addition of ram seminal plasma induced a significant increase (P < 0.05) in litter size in Groups B and D when compared with that of Groups A and C (1.85 and 1.88 vs. 1.39 and 1.52, respectively). This increase was not significant when insemination was performed at the end of the breeding season (2.0 vs. 1.4). These results indicate that the addition of seminal plasma can influence the fertility of ewes or the fertilising capacity of extended ram semen to some extent.

Synchronization of oestrus in goats: dose effect of progestagen

A trial was conducted to test the efficiency of different doses of intravaginal progestagen in the synchronization of different goat breeds, in the breeding season. Sixty Multiparous Boer and 60 Indigenous feral does were allocated to three treatment groups. The groups consisted of a control group (natural oestrus) ( n=20/breed); 60 mg MAP sponge groups inserted for 14 days plus 300 IU PMSG at sponge withdrawal ( n=20/breed) and halved 60 mg MAP (±30 mg) sponges inserted for 14 days plus 300 IU PMSG at withdrawal ( n=20/breed). The time from sponge withdrawal to oestrus was not significantly different in the treatment groups (whole and halved sponges), irrespective of breed. The duration of the oestrous period was significantly ( p<0.01) shorter in the control group (29.3±14.9 h versus 28.0±15.7 h for the Indigenous and Boer goats, respectively), compared to the induced period for the 60 mg (31.1±14.7 and 31.5±15.9 h) or 30 mg (40.0±22.0 h versus 34.3±21.7 h) for the Boer and Indigenous goats, respectively. No significant difference in pregnancy rate following AI was recorded (mean 74.2%). The mean serum progesterone concentration for the observation period varied between 0.01 and 6.19 ng/ml for Indigenous and 0.01 and 9.05 ng/ml for Boer goat does. No significant correlation was recorded between the does pregnant and serum progesterone levels. Mean serum LH concentration of the 60 mg MAP groups (0.59±0.22 ng/ml) was significantly ( p<0.05) lower than the control (0.84±0.66 ng/ml) and the halved sponge (1.9±0.49 ng/ml) groups. Dose of progestagen played no role in the efficiency of synchronization, regardless of the breed. The mean pregnancy rate achieved, is acceptable following fixed-time AI in both breeds and at both doses progestagen.

Monoamine oxidase activity in some brain areas of sheep after hormonal stimulation.

The influence of hormonal superovulatory preparations Folistiman (450 IU FSH, Spofa, Prague) and serum gonadotropin (1500 IU PMSG, Spofa, Prague) on monoamine oxidase (MAO), the degradative enzyme of catecholamines, was investigated in some areas of the brain regulating reproductive functions (area preoptica of the hypothalamus, pituitary gland, and pineal gland) in ewes with synchronized oestrus (20 mg chlorsuperlutin) during the oestrous period using a radiochemical method. After intramuscular administration of 1500 IU PMSG, marked increase of MAO activity was found in the area preoptica (p < 0.05) and in the pituitary gland (p < 0.01) in comparison with the control group. No change occurred in MAO activity after ovarian stimulation with FSH. Administration of the above superovulatory preparations failed to induce MAO activity in the pineal gland of sheep.

The effect of GnRH supplement of FSH and PMSG treatments for prepubertal swamp buffalo calves (Bubalus bubalis).

The objective of the experiment was to improve the multifollicle stimulation technique and the ovarian response examination in prepubertal swamp buffalo calves. Six animals were stimulated by gonadotropin hormone 7 days after a progesterone ear-implant. The first stimulation was done by giving 24 mg FSH + 100 microg GnRH (FSH+GnRH) and the second, one month after by giving 2,000 IU PMSG + 100 microg GnRH (PMSG+GnRH). Twenty-four hours after GnRH, the ovarian responses were checked using rectal palpation and real-time B mode ultrasonography. Five out of six animals (83.3%) responded to both treatments and were selected for oocyte collection. The oocytes were aspirated directly following a caudal midline laparotomy. The results of ovarian responses to FSH+GnRH and PMSG+GnRH averaged 17.6+/-12.1 (L-9.8+/-8.7, R=7.8+/-6.2) and 17.4+/-5.6 (L-9.4+/-2.9, R=8.0+/-3.7), respectively. The average number of recovered oocytes per animal was 9.0+/-6.4 and 8.4+/-1.1, respectively which represented a recovery rate of 56.3 (+/- 9.2)% and 51.9 (+/- 10.3)%. More than eighty percent of the recovered oocytes were in an immature stage with more than 2-3 layers of compact cumulus mass. The present study showed that the oocytes were collected successfully in prepubertal buffalo calves after the FSH+GnRH or PMSG+GnRH stimulation and most of the recovered oocytes were immature, which made them suitable for in vitro maturation and fertilization.

Effect of Bovine Somatotropin Administration on Day 11 after Artificial Insemination in Estrus-Induced Ewes during the Non-Breeding Season.

The present study aimed to examine the possibility that bovine somatotropin (BST) treatment after artificial insemination (AI) may improve the fertility by the stimulation of corpus luteum (CL) function in seasonally anestrous ewes. The experiment was conducted at the Tawa Field Station, Shibecha-cho in Hokkaido, Japan, during the non-breeding season (May, 1995). Eighty-nine mature (2 to 3 years old) Suffolk and Suffolk-crossed ewes were treated with controlled internal drug release devices containing 0.3 g progesterone (CIDR-G) for 12 days. Ewes were injected intramuscularly with 500 IU PMSG the day before CIDR removal. Eighty-seven ewes were assigned to an insemination of frozen semen on a fixed-time basis (42 to 50 h) after removal of CIDR. On the 11th day after AI (13 days after CIDR removal), 43 inseminated ewes were received 100 mg of recombinant BST, while the remaining 44 ewes were given vehicle as controls. The BST administration appeared to reduce pregnancy (65.1% vs. 72.7%) and lambing (51.2 vs. 65.9%) rates, prolificacy (145.5% vs. 165.5%) and proportion of ewes rearing more than two lambs (47.6% vs. 60.7%), as compared with controls, although there was no signifiant difference. BST-treated ewes had higher plasma GH concentrations (endogenous GH plus exogenous BST) at Day 19 (8 days after BST treatment) as compared with controls in both pregnant and non-pregnant ewes (P<0.05). Also, in the control group, plasma GH concentration of pregnant ewes was higher than that of non-pregnant ewes (P<0.05). Plasma progesterone (P) and estradiol-17β (E) cencentrations at Day 19 were lower in BST-treated ewes than that of control ewes (P<0.05). In conclusion, an administration with 100 mg of BST on Day 11 after AI during the non-breeding season resulted in the suppression of the ovarian function 1 week thereafter. Consequently, the conception rate and lambing rate did not improve by the present BST treatment in the ewe.