Injection Of GnRH Analogue Research Articles

Chitosan nanoconjugation of GnRH analogue augments reproductive performance in Clarias magur (Hamilton, 1822)

A breeding trial was conducted to investigate the impact of a chitosan nanoconjugated formulation of Salmon gonadotropin-releasing hormone analogue (ChN-sGnRH-a) on the induced breeding performance of female Clarias magur (magur). A total of 72 magur breeders were divided into six treatment groups: Cn, the Negative Control (injected with bare chitosan nanoparticles); Cp, the Positive Control (injected with Gonopro-FH®, a commercially available inducing hormone, at a dose of 1 mL/kg body weight of fish); T1, injected with ChN-sGnRH-a at a dose of 1 mL/kg; T2, T1 + 10 mg/kg domperidone; T3, injected with ChN-sGnRH-a at a dose of 0.5 mL/kg; T4, T3 + 10 mg/kg domperidone. Blood was collected at 0 (before injection), 6, 12 and 18 h post-injection to determine the serum steroid profile. In the Cp treatment group, the serum steroid levels of testosterone, estradiol, and 17α, 20β-dihydroxy progesterone in the fish, displayed a sharp increase, peaking at the 6-h post-injection, followed by a significant decrease. However, the fish in the T2 and T4 treatment groups exhibited serum steroid peaks at the 12-h post-injection and maintained those levels up to the 18-h post-injection. The reproductive performance, as measured by spawning fecundity, fertilization rate, and hatching rate, was significantly higher in the T2 treatment group (p < 0.05). No significant differences (p > 0.05) were observed between the Cp and T4 treatment groups. Compared to the Cn treatment group, the mRNA expression levels of pituitary follicle stimulating hormone subunit beta and luteinizing hormone subunit beta, as well as ovarian 17β-hydroxysteroid dehydrogenase type 3, were significantly higher in the T2 treatment group, followed by Cp and T4 treatment groups. Fish in the T2 treatment group displayed fewer mature oocytes and numerous post-ovulatory follicles in their ovaries. Additionally, the ovarian histology of fish in the T4 treatment group closely resembled that of the Cp treatment group. The results indicate that the chitosan nanoconjugated formulation of Salmon GnRH analogue might contribute to maintaining elevated levels of gonadotropic and steroid concentrations, resulting in improved reproductive output in female magur breeders. It is also revealed that the induced breeding of magur cannot be achieved without using dopamine inhibitors in GnRH analogue injection. Using chitosan nanoparticles as a nano-delivery system could reduce the Salmon GnRH analogue dose without compromising the reproductive performance of female magur breeders.

Treatment of Inactive Ovaries of Holstein Dairy Cows by Epidural Injection of GnRH Analogue (Receptal) and Its Impact on the Reproductive Hormones, Oxidant/Antioxidant Profile and Micro and Macro-Elements Profile

This study was designed to evaluate a new therapeutic approach for inactive ovaries based on the epidural administration of a GnRH agonist (Receptal) and an investigation of the impact of this treatment on the hormonal, oxidant/antioxidant and micro- and macro-element profiles. Sixty cows with postpartum anestrus were divided into two groups: the first group (group Repid, n = 30) was administered an epidural injection of Receptal, while the second group (group Cepid, n = 30) received saline and was considered the control group. Evaluation of hormonal (progesterone, FSH, LH, testosterone, and cortisol), oxidant/antioxidant (MDA, SOD, GPx and TAC) as well as micro- and macroelement (calcium, phosphorus, manganese and magnesium) profiles was done in serum. The results showed that the epidural injection of Receptal has the potential to induce estrus response and conception incidence in treated cows. Compared to the control group, progesterone, FSH, and LH concentrations were significantly increased in the treated group, whereas testosterone and cortisol decreased (p < 0.05) following treatment. In addition, the treated group had greater TAC and GPx concentrations than the control group. Serum concentrations of magnesium increased (p < 0.05) following receptal treatment, but differences in other minerals were not detected. This research suggests a novel, effective method of treating inactive ovaries with epidural infusion of a GnRH agonist.

Rhythmic Changes in Serum Progesterone and Estradiol-17β in Surti Goats under Different Synchronization Protocols

Background: Success of any estrous synchronization protocol to optimize production and reproduction in goats requires deeper insight of dynamic regulation of hormones progesterone and estradiol-17β. Surti goats reared mostly by marginal livestock owners are native to Gujarat. Present study was conducted to study rhythmic changes in serum progesterone and estradiol-17β in Surti goats under different synchronization protocols.Methods: 18 Surti goats were divided equally (n=6) in 3 groups viz. G1, G2 and G3 (control). G1 and G2 groups were injected with GnRH analogue (day 0 and 11) and PGF2α analogue (day 9). Progestogen sponge was kept intravaginal in G1 group (day 0) and removed (day 11) before GnRH analogue injection. G3 group (control) received placebo of 2 ml normal saline simultaneous to treatment groups.Result: Levels were higher at estrus and lower at day 30 for Estradiol-17β and vice versa for progesterone. Coefficient of variation for estradiol-17β at estrus and for progesterone at day 30 was lower for G1 and higher in control. It was concluded that GPG synchronization protocol with intravaginal progestogen was better to synchronize estrus and establish reproductive cyclicity in Surti goats as it effectively minimized variability of progesterone during pregnancy and estradiol-17β at estrus.

Intrafollicular Injection of Prostaglandins in the Preovulatory Follicle of the Mare

The aim of this study was to evaluate the effectiveness of a protocol based on GnRH and PGF2α to synchronize the emergence of a new wave of ovarian follicular development in llamas and, therefore, when a new dominant follicle develops. Llamas (n = 18) were assigned to growing, mature or regressing follicle groups according to the phase of the follicular wave at the beginning of treatment. The protocol was initiated with a GnRH analogue (GnRHa) injection on Day 0 followed 7 days later with a d-cloprostenol injection and a second GnRHa injection on Day 10. Ovulation rate after the first GnRHa treatment, day of new follicle emergence, mean plasma progesterone concentration and percentage of animals with a newly developed dominant follicle ≥ 7 mm on Day 10 were evaluated. Ovulation rate after the first GnRHa was less in the regressing than mature and growing follicle groups and new follicular wave emergence occurred earlier in the regressing follicle group than in the other two groups. Mean plasma progesterone concentration in females that had ovulations after the first GnRHa injection was similar. The percentage of animals that had a new follicle ≥ 7 mm on Day 10 was not different among groups and the overall percentage was 66.6%. The total synchronization rate for development of a new wave of follicular development on Day 10 was greater in females having ovulations after the first GnRHa injection than in those that did not have ovulations. In conclusion, the protocol used in the present study was useful for synchronizing ovarian follicular development in 66% of the llamas regardless of the phase of the follicular wave development at the beginning of treatment.

Synchronization of time of ovarian follicular development in llamas (Lama glama) using a protocol based on GnRH and PGF2α

The aim of this study was to evaluate the effectiveness of a protocol based on GnRH and PGF2α to synchronize the emergence of a new wave of ovarian follicular development in llamas and, therefore, when a new dominant follicle develops. Llamas (n = 18) were assigned to growing, mature or regressing follicle groups according to the phase of the follicular wave at the beginning of treatment. The protocol was initiated with a GnRH analogue (GnRHa) injection on Day 0 followed 7 days later with a d-cloprostenol injection and a second GnRHa injection on Day 10. Ovulation rate after the first GnRHa treatment, day of new follicle emergence, mean plasma progesterone concentration and percentage of animals with a newly developed dominant follicle ≥ 7 mm on Day 10 were evaluated. Ovulation rate after the first GnRHa was less in the regressing than mature and growing follicle groups and new follicular wave emergence occurred earlier in the regressing follicle group than in the other two groups. Mean plasma progesterone concentration in females that had ovulations after the first GnRHa injection was similar. The percentage of animals that had a new follicle ≥ 7 mm on Day 10 was not different among groups and the overall percentage was 66.6%. The total synchronization rate for development of a new wave of follicular development on Day 10 was greater in females having ovulations after the first GnRHa injection than in those that did not have ovulations. In conclusion, the protocol used in the present study was useful for synchronizing ovarian follicular development in 66% of the llamas regardless of the phase of the follicular wave development at the beginning of treatment.

Umbilical Endometriosis without Pelvic Surgery

We report a recently observed case of primary umbilical endometriosis without previous pelvic surgery. A 41-year-old Japanese woman complained of umbilical nodular tumor. Histopathology revealed endometriosis of an approximate 10 mm resected mass. The stromal cells in endometriosis were immunohistochemically positive for CD10. Two months later the first umbilical surgery, she underwent a left salpingo-oophorectomy and release of adhesion around the left adnexa under a laparoscope. She was treated with dienogest (2 mg/day) for six months after four injections of GnRH analogue for four months. After three years of the follow-up, there were no signs of local relapse and no clinical and ultrasonographic abnormalities due to endometriosis.

Assessment of gonadotrophin suppression in girls treated with GnRH analogue for central precocious puberty; validity of single luteinizing hormone measurement after leuprolide acetate injection

Intravenous GnRH stimulation test has often been used as gold standard test for the evaluation of hypothalamic-pituitary-gonadal axis in the diagnosis of central precocious puberty (CPP) and in the assessment of pubertal suppression. However, this test is time-consuming, costly and uncomfortable for the patients. We aimed to analyse the validity of single LH sample 90 min after GnRH analogue (GnRHa) administration in the evaluation of gonadotrophin suppression during CPP therapy and to determine a cut-off level for LH indicating adequate suppression. Prospective study. One hundred and forty-two patients with CPP were included in this study. Peak LH level during iv GnRH stimulation test after the third dose of GnRHa was compared with LH level 90 min after injection of the 3rd dose of GnRHa. There was a positive correlation between LH level following a GnRHa injection and peak LH during standard iv GnRH stimulation test (r = 0·83; P < 0·0001). A LH value of 2·5 mIU/ml or less 90 min after GnRHa injection was considered to be the cut-off for the determination of pubertal suppression (sensitivity and specificity was 100% and 88%, respectively). In 117 patients, gonadotrophin suppression was existed according to both GnRHa and iv GnRH tests. In 25 patients, gonadotrophin suppression was not found in the GnRHa test. However, 16 of them were suppressed according to the iv GnRH test. Single LH determination 90 min after GnRHa administration using a cut-off level of 2·5 mIU/ml reflects pubertal suppression with a high sensitivity and specificity. However, this test may fail to show pubertal suppression in some cases. Those patients who appear to be inadequately suppressed should be reassessed using standard iv GnRH stimulation test for optimal dose adjustment.

Therapeutic Effect of Frequent Injections of GnRH Analogue in a Beagle with Knobbed Acrosome Abnormality of Sperm

A Beagle dog (3 years old) that ejaculated high percentages (mean ± SE: 29.1 ± 1.2%) of sperm with a knobbed acrosome abnormality and a low number of sperm and that also had a low plasma testosterone (T) level was given 10 subcutaneous injections of 1 µg of gonadotropin-releasing hormone analogue (GnRH-A) at 3-day intervals. The plasma T level and number of sperm increased 12-14 weeks after the first injection. Although the percentages of sperm with knobbed acrosome abnormality did not change after the GnRH-A therapy, the number of sperm and percentage of actively motile sperm increased after the therapy, and a bitch gave birth to 5 healthy puppies after intravaginal artificial insemination with fresh semen collected 14 weeks after the first injection.

Induction of spawning and spermiation in captive Peruvian anchovy Engraulis ringens (Jennyns) using GnRH analogue injection

Induction of spawning and spermiation in captive Peruvian anchovy Engraulis ringens (Jennyns) using GnRH analogue injection

Effects of the levonorgestrel-releasing intrauterine system on cardiovascular risk markers in patients with endometriosis: a comparative study with the GnRH analogue

Background The study was conducted to evaluate the cardiovascular risk markers associated with endometriosis and the influence of the levonorgestrel intrauterine system (LNG-IUS) compared with the GnRH analogue (GnRHa) leuprolide acetate on these risk markers after 6 months of treatment. Study Design This was a randomized, prospective, open clinical study, with 44 patients with laparoscopically and histologically confirmed endometriosis. Patients were randomized into two groups: the LNG-IUS group, composed of 22 patients who underwent LNG-IUS insertion, and the GnRHa group, composed of 22 patients who received a monthly GnRHa injection for 6 months. Body mass index; systolic and diastolic arterial blood pressure; heart rate; and laboratory cardiovascular risk markers such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), C-reactive protein (CRP), homocysteine (HMC), lipid profile, total leukocytes and vascular cell adhesion molecule (VCAM) were measured before and 6 months after treatment. Results After 6 months of treatment, a significant reduction in pain score occurred in both groups with no significant difference in improvement between the two medications evaluated. In the LNG-IUS group, from pretreatment to posttreatment period, there was a significant reduction in the levels (mean±SD) of VCAM (92.8±4.2 to 91.2±2.7 ng/mL, p=.04), CRP (0.38±0.30 to 0.28±0.21 mg/dL, p=.03), total cholesterol (247.0±85.0 to 180.0±31.0 mg/dL, p=.0002), triglycerides (118.0± 76.0 to 86.5±41.5 mg/dL, p=.003), low-density lipoprotein cholesterol (160.5±66.0 to 114.5±25.5 mg/dL, p=.0005) and high-density lipoprotein cholesterol (63.0±20.5 to 48.5±10.5 mg/dL, p=.002). The GnRHa group showed an increase in HMC levels (11.5±2.9 to 13.0±2.7 μmol/L, p=.04) and a reduction in IL-6 levels (4.3±3.9 to 2.3±0.8 pg/mL, p=.005), VCAM (94.0±3.8 to 92.0±1.6 ng/mL, p=.03) and total leukocytes (7330±2554 to 6350±1778, p=.01). In the GnRH group, the remaining variables, including lipid profile, did not show any statistical difference. Conclusions This study shows that some cardiovascular risk markers are influenced by both GnRHa and the LNG-IUS, but the latter had a greater positive impact on the lipid profile, which could lead to a favorable effect during long-term treatment.

Changes in Plasma Testosterone Level and Semen Quality after Frequent Injections of GnRH Analogue in a Beagle Dog with Azoospermia

A Beagle with a low plasma testosterone (T) level and azoospermia was given 10 subcutaneous injections of 1 microg gonadotropin-releasing hormone analogue (GnRH-A) per head at intervals of 3 days (Experiment 1), and 6 months after the final injection was given, 15 subcutaneous injections of 2 microg GnRH-A were given at intervals of 2 days (Experiment 2). The plasma T level increased and peaked at 8 weeks after the first injection of GnRH-A in both Experiment 1 and Experiment 2. Motile sperm were detected in the semen collected 8 weeks and 7 weeks after the first injection in Experiment 1 and Experiment 2, respectively. The total number of sperm peaked 9 weeks after the first injection in both Experiment 1 (4.5 x 10(6)) and Experiment 2 (72.8 x 10(6)).

Blood flow in the wall of the preovulatory follicle and its relationship to pregnancy establishment in heifers

Color-Doppler ultrasonography was used to compare the vascularity of the preovulatory follicle between heifers that became pregnant compared with nonpregnant. Heifers ( n = 34) received a luteolytic dose of PGF2α when the diameter of the largest follicle of the second follicular wave reached ≥11 mm (actual diameter 11.63 ± 0.06 mm). An ovulation-inducing injection of GnRH analogue was given 36 h after the PGF2α treatment. Artificial insemination (AI) was performed 26 h after GnRH treatment, and ovulation occurred in all heifers within 3 h after AI. Follicle blood flow was assessed at Hour 0 (GnRH treatment) and at Hour 26 (AI). Follicle diameter at Hours 0 and 26 was greater (main effect of group; P < 0.03) in the group that became pregnant ( n = 25) compared with nonpregnant ( n = 9). Percentage of follicle wall with power Doppler signals of blood flow showed an interaction of group-by-hour ( P < 0.03), reflecting greater blood flow in the pregnant group than in the nonpregnant group at Hour 26 but not at Hour 0. Spectral-Doppler evaluation of the resistance index for a vessel in the follicle wall resulted in a group-by-hour interaction ( P < 0.03) from a lower index in the pregnant group at Hour 26. The lower index indicated greater downstream vascular perfusion in the follicle wall. Results supported the hypothesis of a positive relationship between the extent of blood flow of the preovulatory follicle and successful establishment of pregnancy in cattle.

Inducing ovulation and artificial insemination in the European brown hare ( Lepus europaeus Pallas, 1778)

The aim of the study was to show whether it is possible to induce ovulation in the hare by GnRH analogue administration and to carry out an effective artificial insemination (AI). The research was carried out during the breeding and non-breeding season. During the breeding season, plasma progesterone concentrations increased on the 4th day after intramuscular injection of GnRH analogue (buserelin), indicating induced ovulation and corpus luteum development. Prostaglandin F 2α (dinoprost) was an effective luteolytic agent on day 9. During the non-breeding season, the GnRH analogue injection does not cause an increase of progesterone. The 17β-estradiol concentrations during the breeding and non-breeding season were similar. It was shown that after GnRH analogue administration and artificial insemination with semen diluted in Tris buffer extender 80% females delivered live young (39–43 days after artificial insemination), which proves the effectiveness of inducing ovulation in the hare by means of hormonal stimulation.

The combined effects of temperature and GnRHa treatment on the final stages of sexual maturation in Atlantic salmon (Salmo salar L.) females

Atlantic salmon (Salmo salar L.) females (2 SW), maturing for the first time, were reared under one of three temperature regimes (high: 14.3 +/- 0.5 degrees C; natural: 10.6 +/- 1.0 degrees C; and cold: 6.9 +/- 1.0 degrees C) in combination with one of two experimental treatments; an injection of GnRH analogue (GnRHa) contained in biodegradable microspheres, or a sham injection (microspheres only). The six experimental groups were then reared under simulated natural photoperiod for 4 weeks. Blood samples were drawn for analysis of plasma steroid levels and the fish were inspected for ovulation weekly. Batches of stripped eggs were incubated in triplicate incubators in raceways until the eyed stage. Treatment with GnRHa resulted in a substantial advancement and synchronization of ovulation at all temperatures, while exposure to cold water also appeared to advance ovulation slightly. While 75% (warm and cold) to 90% (natural) of GnRHa fish ovulated during the 4-week trial, only 30% of sham-treated females exposed to cold water, and none of the sham-treated fish held at higher temperatures, ovulated during this period. Survival rates of embryos to the eyed-stage were significantly higher for broodstock exposed to cold water. Plasma levels of testosterone (T), 17beta-oestradiol (E2), and 17alpha,20beta-dihydroxy-4-pregnen-3-one (17,20betaP) were all significantly affected by treatment with GnRHa and, to a lesser extent, temperature. The efficiency of GnRHa in counteracting the negative effects of high temperature on ovulation and the associated changes in circulating sex steroids suggest that temperature inhibition operates at least in part at the brain or pituitary.

The Significance of Endogenous Testosterone on the Adaptation to Strength Training

Endogenous testosterone (ET) interacts with skeletal muscle and is a component of an integrated endocrine system that seems to mediate the adaptive changes in muscles as a result of strength training (ST). In addition, the myogenic regulating factors (MRFs) including myoD and myogenin seem to play an essential role in the ST induced muscle hypertrophy. The interaction between ST, levels of ET, myoD and myogenin, muscle hypertrophy and increased strength has not been examined. PURPOSE: Suppression of ET will inhibit the adaptation to ST with a concomitant decrease in the mRNA expression of myoD and myogenin, leading to a less pronounced increase in lean mass and muscle strength. METHODS: Twenty-two moderately trained young men with no experience of ST volunteered to participate in this randomized, placebo-controlled, intervention study. The subjects were divided in two groups (zoladex (Z) n = 1 2 and placebo (P) n = 1 0). ET levels were suppressed using injections of GnRH-analogue (Zoladex, AstraZeneca). Zoladex (3.6 mg) or placebo (saline) was administered sub cutaneous ly every 4 wk for a period of 12 wk. The ST period started 3 wk after the first injection and the subjects were assigned to a full body ST program emphasizing the legs for 8 wk. Subjects trained 6–10 reps with corresponding 6–10 RM loads x 3 – 4 sets per exercise, 3/wk. Before and after the ST period strength test (Kin-Com 500H, USA) and whole body DEXA scan (Hologic 4500) were performed. Biopsies were taken in the right vastus lateralis at 4 time points to measure the mRNA expression of myoD and myogenin. Before (biopsy nr. 1.) and after (nr. 2.) the ST period and in relation to the last ST session (pre (nr. 2.), 4 h post (nr. 3.) and 24 h post (nr. 4.)). MyoD and myogenin mRNA expression were normalized to GAPDH. RESULTS: Absolute isometric strength increased significantly after 8 wk of ST in P from 240.2 ± 41.3 (SD) Nm to 264.1 ± 35.3 Nm (p<0.05) while Z showed no changes 224.8 ± 44.4 to 230.0 ± 39.8 Nm (p = 0.05 between groups). Lean mass for the legs increased 0.38 ± 0.1 kg in Z and 0.57 ± 0.3 kg in P (p<0.05 within and p = 0.05 between groups). MyoD expression showed no changes between different time points, whereas myogenin expression was nearly 4 fold higher when comparing biopsy nr. 3. with biopsy nr. 2. (p<0.05). In addition, biopsy nr. 3. and 4. was significantly higher than biopsy nr. 1. and 2. (p<0.05). There were no differences between the myogenin expression in the two groups. CONCLUSIONS: This study showed that ST with suppression of ET production does not inhibit local cellular mRNA expression of myogenin but leads to a less pronounced increase in lean mass and no increase in muscle strength.

Synchronization of ovulation in yaks ( Poephagus grunniens L.) using PGF 2α and GnRH

The objective of this study was to test the efficacy of estrus synchronization in yaks using the Ovsynch protocol. To eight non-lactating cycling yaks were administered GnRH analogue followed by PGF 2α analogue treatment 7 days later and further injected with a second injection of same GnRH analogue 2 days after the PGF 2α analogue administration. Ovulation was detected by rectal palpation at 2 h intervals from the initial signs of estrus till ovulation. For LH and progesterone the blood samples were collected at 15 min intervals starting from 1 h prior to the second injection of GnRH analogue until 6 h later and further at 2 h intervals till 2 h after the ovulation. Ovulation was detected in seven out of eight yaks after Ovsynch treatment. The mean time interval from the second GnRH injection to ovulation was 24.8 ± 1.95 h with a range of 20–34 h and the mean interval from the LH peak and ovulation was 19.96 ± 1.91 h with a range of 14–29 h. The high degree of ovulation synchronization could be attributed to the highly synchronized LH peaks in the treated animals. It was concluded that this estrus synchronization protocol could be applied for fixed time AI in yak.

Effects of GnRH Administered to Cows at the Onset of Estrus on Timing of Ovulation, Endocrine Responses, and Conception

Two experiments examined effects of GnRH administered within 3h after onset of estrus (OE) on ovulation and conception in dairy cows. In experiment 1, 46 cows received either saline, 250μg of GnRH, or 10μg of the GnRH analogue, Buserelin. Cows were observed for estrus, blood samples were collected, and ovulations were monitored by ultrasound. In controls, 76% of cows had intervals from estrus to ovulation of≤30h and 24% had intervals>30h. Treatment with either GnRH or GnRH analogue (data combined) increased magnitude of LH surges and decreased intervals from estrus to LH surge or to ovulation. Treated cows all ovulated≤30h after OE. Among control cows, plasma estradiol concentrations before estrus correlated positively with amplitudes of LH surges. Higher plasma progesterone was observed in the subsequent estrous cycle in GnRH-treated cows compared to control cows with delayed ovulations. Experiment 2 included 152 primiparous and 211 multiparous cows in summer and winter. Injection of GnRH analogue at OE increased conception rates (CR) from 41.3 to 55.5% across seasons. In summer, GnRH treatment increased CR from 35.1 to 51.6%. Across seasons, GnRH increased CR from 36.0 to 61.5% in cows with lower body condition at insemination and GnRH increased CR (63.2 vs. 42.2%) in primiparous cows compared to controls. Use of GnRH eliminated differences in CR for cows inseminated early or late relative to OE and increased CR in cows having postpartum reproductive disorders. In conclusion, GnRH at onset of estrus increased LH surges, prevented delayed ovulation, and may increase subsequent progesterone concentrations. Treatments with GnRH increased conception in primiparous cows, during summer, and in cows with lower body condition.

The effect of increased dietary intake on superovulatory response to FSH in heifers

We have previously shown that the number of ovarian follicles <4 mm in diameter can be increased by enhanced dietary intake in heifers. This study investigated the effect of the same dietary treatment on superovulatory response. The estrous cycles of 24 mature Hereford×Friesian heifers were synchronized by a standard progesterone plus prostaglandin protocol. The animals were fed with either 100% (group M, n=12) or 200% (group 2M, n=12) maintenance requirements for a 3-week period. Starting from day 4 of the synchronized estrous cycle, all the animals were superovulated using a standard 4-day FSH regime followed by an injection of GnRH analogue (GnRHa) to induce ovulation. Rectal ultrasound scanning was carried out to assess ovarian follicular populations at the start of FSH treatment and on the day of GnRHa injection, and to determine the number of corpora lutea 5 days after GnRHa injection. The body weight (BW) and body condition score (BCS) were recorded weekly and plasma samples were collected throughout the experimental period. There were no differences in either BW or BCS between two groups at the start of the experiment. The BW and BCS were maintained during the experiment in the group M, whilst animals in the group 2M showed a non-significant ( P>0.05) increase in BW and BCS. Circulating concentrations of insulin were significantly ( P<0.01) higher in heifers from the group 2M throughout the controlled feeding period. The group 2M had significantly ( P<0.05) more follicles 2–4 mm in diameter at the start of FSH treatment and more ( P<0.01) follicles >9 mm in diameter on the day of GnRHa injection, when compared with the group M. Similarly, 5 days after GnRHa injection there were significantly ( P<0.01) more corpora lutea in the group 2M (18.1±2.2) than in the group M (10.6±3.0). In addition, plasma progesterone concentrations following GnRHa injection were significantly ( P<0.01) higher in heifers from the group 2M. In conclusion, these results confirm that increased dietary intake can enhance the recruitment of ovarian follicles in heifers. This treatment may provide a valuable approach to improving superovulatory response in cattle.

Effect of gonadotropin-releasing hormone analogue (GnRHa) and pimozide on plasma levels of sex steroids and ovarian development in sea bass ( Dicentrarchus labrax L.)

To synchronise and advance spawning, European sea bass females in late vitellogenesis were treated with two i.p. injections of GnRH analogue alone (5 and 20 μg/kg BW) given 12 h apart, or combined with pimozide (PIM) (10 mg/kg BW) either in the first or second injection. Saline-injected and untreated females were used as controls. Administration of GnRHa alone or combined with PIM accelerated the final oocyte maturation (FOM) and induced spawning. However, 48 h after the second injection the size of oocytes and the percentage of oocytes in GVBD stage were lower in the PIM-treated females. The number of eggs spawned was highest in the group that received GnRHa alone and lowest in the group that received PIM in the second injection. Plasma levels of 17β-oestradiol (E2) increased sharply at 12 h after the first injection of GnRHa alone or combined with PIM, decreasing after a second injection of GnRHa alone. However, the plasma E2 decreases was much slower in females that received the PIM in the first injection. Females that received PIM in the second injection still showed elevated plasma E2 during a longer period. Plasma testosterone (T) increase was parallel to the plasma E2 decrease and peaked earlier in the group that received GnRHa alone in both injections. Low and nonsignificant changes of 17α,20β-dihydroxy-4-pregen-3-one (17,20β-P) were observed in plasma during the time that the animals were sampled. The results demonstrate that the use of PIM does not improve the GnRHa treatment and the use of GnRHa alone during the last stages of vitellogenesis is enough to induce FOM in the European sea bass.

Effect of injection of GnRH analogue at the onset of oestrus on LH and FSH release and embryonic mortality in gilts

In the 1st of 2 experiments, 5 gilts were injected with saline at the onset of standing oestrus (control oestrus), and at the next cycle the same gilts were injected with 100 mu g GnRH analogue. The LH and FSH peaks in the GnRH-treated oestrus were not significantly different from those in the control oestrus, but both peaks were sharper in the GnRH-treated oestrus. In the 2nd experiment, 49 gilts were injected with 100 mu g GnRH at the onset of standing oestrus or were not treated (controls), and slaughtered on day 4, 11, 13 or 35 of pregnancy. For animals slaughtered on day 4, 11 or 13, compared with controls, treated animals had significantly more corpora lutea (16.3+or-2.3 vs. 14.8+or-1.5) and embryos (15.0+or-3.0 vs. 12.1+or-3.4). Embryonic mortality on day 35 was 24.7% in the treated group vs. 11.3% in controls. The av. number of corpora lutea for gilts slaughtered on all 4 days was greater in treated gilts than in controls (16.4+or-2.3 vs. 14.3+or-3.3), but the difference was not significant. A similar trend was observed for number of embryos (15.4+or-2.0 vs. 13.0+or-3.3).