The effect of melatonin implants during the seasonal anestrus on embryo production after superovulation in aged high-prolificacy Rasa Aragonesa ewes

Administration of melatonin prior to modified synchronization protocol improves the productive and reproductive efficiency of Chinese crossbred buffaloes in low breeding season

Introduction

Melatonin is a neurohormone involving various biological processes, including restoration of cyclicity in animals with seasonal breeding patterns. The use of melatonin in different forms has gained broader acceptance in different species, particularly in summer anestrous buffaloes.

Objectives

The objective of the current study was to evaluate the melatonin effect on the reproductive and productive performance of crossbred buffaloes during the low breeding season.

Methods

Sixty-five cyclic and reproductively sound crossbred buffaloes were randomly allocated to three groups: the G1 (n = 20) served as the control group and received no single melatonin, G2 received melatonin (n = 22; 18 mg/50 kg, body weight) once prior to synchronization and G3 group was administered multiple melatonin injections (n = 23; 6 mg/50 kg body weight) for three consecutive days before the start of the synchronization protocol. The reproductive performance, milk yield traits, and serum immunoglobulin M (IgM) and melatonin levels were evaluated in treated and untreated crossbred buffaloes.

Results

The results revealed that a single dose of melatonin administration has (p < 0.05) improved estrus response, ovulation occurrence and follicular growth in crossbred buffaloes compared to control groups. Higher pregnancy rates were observed in both melatonin-treated buffalo groups compared to the control. Following the administration of melatonin, serum IgM level increased in G2 and G3; however, an increment in melatonin level (p < 0.05) was detected in the G2 group only as compared to the control group subsequent day of melatonin administration. The milk compositions were not affected by melatonin administration except for milk urea nitrogen and somatic cell count (SCC). The melatonin administration (p < 0.05) decreased the somatic cell count in buffalo milk compared to untreated.

Conclusion

In conclusion, single or multiple doses of melatonin before initiating the synchronization protocol improved the ovulation, ovulatory follicle diameter and pregnancy rates in crossbred buffaloes during the low breeding season. Moreover, the administration of melatonin enhanced the IgM values along milk traits in terms of milk protein, MUN and somatic cell count in treated buffaloes.

Reproductive performance of hair ewes and rams implanted with melatonin previous to the anestrus season in northwest Mexico

Ovine reproductive behavior depends on annual photoperiodic cycle and its impact on endogenous melatonin secretion. In this regard, exogenous melatonin administration previous to the physiological anestrus period could modify the reproductive performance of sheep in the northwest of Mexico. Two independent studies were performed to evaluate such hypothesis in hair sheep implanted with melatonin prior to the anestrus season in latitudes 24° and 25° of Mexico. Study 1 involved 15 rams assigned to one of three treatments receiving 0mg (n=5), 18mg (n=5), or 36mg (n=5) of melatonin subcutaneously. Study variables were measured monthly since implantation (d0) and included testosterone concentration, scrotal circumference, mass motility, individual motility, and sperm concentration. Study 2 included 50 ewes assigned to one of two treatments receiving 0mg (n=25) or 18mg (n=25) of melatonin subcutaneously. In ewes, progesterone concentration and the frequency of females in anestrus were measured during the implantation (-30d), as well as at the beginning (0d) and at the end (45d) of the mating period, while pregnancy rate was determined by ultrasonography 45d after. Continuous variables were analyzed using a mixed effects model considering treatment, time, and the treatment by time interaction as fixed effects. Animal nested within treatment was the random effect. Binary variables were analyzed using the chi-square test. In males, melatonin improved testosterone and sperm concentrations (P<0.05), while in females, a 28% higher pregnancy rate was observed in implanted ewes (P<0.05). Therefore, melatonin enhanced reproductive parameters in both sexes and its exogenous administration previous to the anestrus season in northwest Mexico could be more effective in rams.

Redox Status and Hematological Variables in Melatonin-Treated Ewes during Early Pregnancy under Heat Stress

The preovulatory follicles and preimplantation stage embryos are found to be rather sensitive to heat stress due to their low potential for scavenging reactive oxygen species (ROS). The aim of the present study was to assess the impact of melatonin administration on redox status and hematological variables during the preovulatory period and early stages of embryogenesis in heat-stressed ewes in vivo. Forty Karagouniko-breed ewes were divided in two groups, the melatonin (M, n = 20) group and control (C, n = 20) one. All animals were subjected to heat stress throughout the study, which lasted forty days (D0 to D40). In M group, melatonin implants were administered on D0. Then, oestrous synchronization was applied (D19-D33). On D34, six rams were introduced into the ewe flock for mating. Ultrasonographic examination was conducted on D73 for pregnancy diagnosis. The temperature humidity index (THI), the rectal temperature (RT), and the number of breaths per minute (BR) were evaluated twice daily. Redox biomarkers, namely total antioxidant capacity (TAC), reduced glutathione (GSH), and thiobarbituric acid reactive substances (TBARS), were assayed in blood samples collected on D0, D33, and D40. In addition, packed cell volume (PCV), white blood cells (WBCs), leukocyte differential count, and cortisol assessment were conducted in blood samples on D33 and D40. The results indicated improved fertility rate and mean number of lambs born per ewe due to improved redox status (p < 0.05) in ewes that received melatonin implants 34 days approximately before the onset of oestrus. The PCV decreased in both groups between the two time-points (p < 0.05). However, the NEU/LYMPH ratio decreased (p < 0.05) only in group M. The low cortisol levels and the decreased NEU/LYMPH ratio in both groups support the hypothesis that ewes of the indigenous Karagouniko breed may exhibit adaptation to environmental thermal stress. The administration of melatonin as an antioxidant regime may improve the reproductive competence of heat stressed ewes and may also enhance their ability to adapt at high ambient temperatures.

The Melatonin Treatment Improves the Ovarian Responses After Superstimulation in Thai-Holstein Crossbreeds Under Heat Stress Conditions

The effect of heat stress with melatonin treatment on the superovulatory responses and embryo characteristics in Thai-Holstein crossbreeds under heat stress conditions was examined. Six non-lactating cows (replication = 4; n = 24) were assigned to one of 2 treatments in double cross-over design. All cows were superstimulated with traditional treatment. Melatonin group (n = 12): cows received intramuscularly injection 18 mg/50 kg. simultaneously with GnRH injection, while those in the control group (n = 12) received none. Bloods samples were taken to determine lipid peroxidation (MDA) and the activity of the antioxidant enzymes (superoxide dismutase; SOD). The experiment was conducted from April to September, which determined severe heat stress (the mean temperature-humidity index above 77). The results revealed that numbers of large follicles and corpora lutea were higher in the melatonin group than in the control group (p &lt; 0.01). Numbers of recovered ova/embryos, fertilized ova, and transferable embryos were higher in the melatonin group (p &lt; 0.01); meanwhile, more degenerated embryos were found in the control group (p &lt; 0.01). Increased activity of the antioxidant enzymes SOD after melatonin administration decreased MDA levels (p &lt; 0.05). In summary, melatonin administration benefited the ovarian response and embryo quality in superstimulated Thai-Holstein crossbreed affected by heat stress.

Towards Improving the Outcomes of Multiple Ovulation and Embryo Transfer in Sheep, with Particular Focus on Donor Superovulation

Considerable improvements in sheep multiple ovulation and embryo transfer (MOET)protocols have been made; however, unlike for cattle, MOET is poorly developed in sheep, and thus has not been broadly applicable as a routine procedure. The tightly folded nature of the ewe cervix, the inconsistent ovarian response to various superovulatory treatments, and the requirement of labor to handle animals, particularly during large-scale production, has limited the implementation of successful MOET in sheep. Moreover, several extrinsic factors (e.g., sources, the purity of gonadotrophins and their administration) and intrinsic factors (e.g., breed, age, nutrition, reproductive status) severely limit the practicability of MOET in sheep and other domestic animals. In this review, we summarize the effects of different superovulatory protocols, and their respective ovarian responses, in terms of ovulation rate, and embryo recovery and transfer. Furthermore, various strategies, such as inhibin immunization, conventional superovulation protocols, and melatonin implants for improving the ovarian response, are discussed in detail. Other reproductive techniques and their relative advantages and disadvantages, such as artificial insemination (AI), and donor embryo recovery and transfer to the recipient through different procedures, which must be taken into consideration for achieving satisfactory results during any MOET program in sheep, are also summarized in this article.

Two melatonin treatments improve the conception rate after fixed-time artificial insemination in beef heifers following synchronisation of oestrous cycles using the CoSynch-56 protocol

OBJECTIVE

This study investigated the effect of melatonin administration in combination with the CoSynch-56 protocol on the conception rate after artificial insemination (AI) in beef heifers.

METHODS

Eighty-six beef heifers were allocated to four treatments in combination with CoSynch-56 treatment. All heifers, excluding the control group (CTR = 25), were injected with melatonin on day 1. The melatonin (MT = 20) and MT + human chorionic gonadotropin (MT + hCG = 21) groups received no further treatment with melatonin. Each heifer was treated with gonadotropin-releasing hormone (GnRH) on day 4, prostaglandin F2α (PGF2α) on day 11, and GnRH and AI 56 h later. The fourth group (2MT = 20) was injected again with melatonin concurrent with AI, and the MT + hCG group received hCG on day 19. Pregnancy diagnosis was performed using transrectal ultrasonography 45 days after AI and blood samples were collected via caudal venipuncture on days 0-1, 14-15, 24 and 59. Concentrations of progesterone (P4) and the activities of oxidative stress-related enzymes were determined using enzyme-linked immunosorbent assay.

RESULTS

The conception rate was greater in the 2MT group (75%) than in the other groups, while there was no significant difference among the CTR (44%), MT (45%) and MT + hCG (38.1%) groups. Treatment with melatonin increased superoxide dismutase and glutathione peroxidase activities and decreased malondialdehyde concentrations but did not significantly affect the concentration of P4.

CONCLUSION

Our results indicate that the administration of melatonin twice during the CoSynch-56 protocol may increase conception rates in beef heifers.

Melatonin treatment and male replacement every week on the reproductive performance in Sarda sheep breed

The aim of this study was to highlight whether the combination of melatonin treatment and weekly male replacement could influence reproductive performances in Sarda sheep breed. In a preselected farm, on 5th March 2016, 400 lactating ewes were identified, aged 3-5 years, with body condition score (BCS) 2.5-4.0, who lambed between 20th October and 1st December 2015. The 400 chosen animals were subsequently divided into 4 groups with 100 animals in each group (M, MR, C and CR). On 20th March 2016 the animals of Group M and MR (consisting of 100 ewes each) were treated with melatonin implants and on 24th April 2016 five entire rams were introduced into each group. In groups MR and CR, males were replaced each week with other males whereas in groups M and C the introduced males were not replaced. The MR group showed the highest fertility (number of lambed ewes) compared to the other three groups (P < 0.01). Both the melatonin treated groups (M and MR) exhibited an increase in fertility greater than the controls groups C and CR (P < 0.01). However, when the two groups treated with melatonin were compared, the MR group showed a higher fertility than the M group (P < 0.01). The same can be said for the two control groups, of which the CR group showed a greater increase in fertility than the C group (P < 0.01). The mean interval of days from male introduction to lambing was lower in the treated than in the control groups (P < 0.05). The MR group presented the lowest mean interval of days from male introduction to lambing amongst all of the groups (P < 0.05). A similar trend was recorded for group CR when compared to group C (P < 0.05). In the MR and M groups the lambing peak was recorded close to 170 days after the males introduction, whereas the CR group and the C group were reported to be around 180 days and 190 days, respectively. At the 170th day from the male introduction the number of ewes lambed in the MR group was greater than that of the M group (P < 0.05) (60 vs. 42), and more than double of that of the C and CR groups (P < 0.01). In conclusion, weekly male replacement improved the reproductive activity and strengthened the effect of the pineal hormone on reproductive efficiency. Therefore male replacement either in untreated animals or in association with the melatonin implants, can be straightforwardly applied to guarantee a more efficient reproduction in sheep breeding.

Melatonin-induced demethylation of antioxidant genes increases antioxidant capacity through RORα in cumulus cells of prepubertal lambs

Physical damage and oxidative stress may occur in prepubertal cumulus cells, due to insufficient glutathione synthesis. To determine potential epigenetic mechanisms related to antioxidant effects of melatonin on ovine prepubertal cumulus cells, 30 lambs, 4-wk-old were randomly allocated into two groups: a control (C, n = 20) group and a melatonin (M, n = 10) group given a subcutaneous implant containing 18 mg melatonin. All lambs were superovulated (250 IU FSH and 250 IU eCG). Cumulus cells from germinal vesicle stage cumulus oocyte complexes (COCs) were collected by ovarian follicular aspiration and dissociated with hyaluronidase. Compared to the C group, the M group had greater superovulation, better antioxidant capacity, a higher proportion of fully expanded COCs and a lower proportion of apoptotic cumulus cells (P < 0.05). Melatonin up-regulated mRNA expression of genes for melatonin receptors MT1 and nuclear binding site RORα, antioxidants (SOD1, GPx4 and CAT) and cumulus cell expansion (PTX3, HAS2 and PTGS2), as well as Bcl2, but down-regulated expression of Bax (P < 0.05). Regarding epigenetics, there were less methylation at five CpG sites of SOD1, three CpG sites of GPx4 and two CpG sites of CAT in M versus C groups (P <  0.05), leading to lower total methylation of SOD1, GPx4 and CAT promoters region on M group (P < 0.05). In a mechanistic study, addition of MT1 or RORα antagonist increased ROS and MDA concentrations, but decreased T-AOC, GPx, CAT and T-SOD concentrations (P < 0.05), whereas there were no significant difference between the melatonin and MT2 antagonist treatment groups for T-AOC, GPx, CAT and T-SOD concentrations. Furthermore, addition of RORα agonist decreased total DNA methylation of SOD1, GPx4 and CAT, with no significant difference after MT1 agonist treatment. These studies provided new information regarding epigenetic mechanisms by which melatonin promoted ovine prepubertal cumulus cells antioxidant through RORα, both in vitro and in vivo.

Role of melatonin on embryo viability in sheep

Melatonin is a natural hormone synthesised in the pineal gland, the activity of which is regulated by day-night perception and dictates seasonal rhythms in reproduction in ovine species. Exogenous melatonin, administered via subcutaneous implants, is used to prolong the breeding season of ewes and can increase the proportion of pregnant ewes (fertility rate) and litter size. The increased proportion of ewes that become pregnant and the number of lambs born per lambing among melatonin-treated sheep may be caused by increased embryo survival, through enhanced luteal function, reduced antiluteolytic mechanisms, or improved embryo quality. This review focuses on the effects of melatonin on embryo viability and summarises the processes by which this hormone affects the ovary, follicle, oocyte, corpus luteum and embryo. Moreover, the effects of melatonin on the mechanisms of invivo maternal recognition of pregnancy in sheep and the protective action that it appears to have on the invitro procedures that are used to obtain healthy embryos are reviewed.

Female Reproductive Performance in the Mouse: Effect of Oral Melatonin

Although melatonin has some of the broadest ranges of actions on the physiology of vertebrates, especially on their reproductive processes, the mechanism by which melatonin regulates animal reproduction is still incompletely understood. This study was designed to determine the effect of oral melatonin on the reproductive performance of female mice. Female ICR mice (7 weeks old) were given melatonin-containing water (3, 30 and 300 μg/mL; melatonin) or water only (control) until 10 weeks of age. Then, some of the mice were successfully mated (confirmed by vaginal plugs), and the number of live births and their weights were recorded. Some mice were used for a histological analysis of the number of follicles in the ovaries. Others were used for oocyte collection after superovulation, and in vitro fertilization (IVF) was performed. The mRNA expression of the apopotosis-related genes (BAX, BCL2) in the IVF embryos were analyzed. After melatonin administration, the mice showed similar serum melatonin levels to that of the control. The number of antral follicles per mm² unit area in the 30 μg/mL melatonin-treated group (14.60) was significantly higher than that of the control (7.78), which was lower than that of the 3 μg/mL melatonin-treated group (12.29). The litter size was significantly higher in the 3 μg/mL melatonin-treated group (15.5) than in the control (14.3). After IVF, the hatched blastocyst formation rate in the 30 μg/mL melatonin-treated group (85.70%) was significantly higher than that of the control (72.10%), and it was the same for the BCL2/BAX expression ratio. Although oral melatonin did not appear to have an effect on the serum melatonin rhythm in the mouse, melatonin did increase litter size at the 3 μg/mL dose level, and improved the developmental competency of IVF embryos at the 30 μg/mL level.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Alterations in uteroplacental hemodynamics during melatonin supplementation in sheep and cattle

Compromised placental function can result in fetal growth restriction which is associated with greater risk of neonatal morbidity and mortality. Large increases in transplacental nutrient and waste exchange, which support the exponential increase in fetal growth during the last half of gestation, are dependent primarily on the rapid growth and vascularization of the uteroplacenta. The amplitude of melatonin secretion has been associated with improved oxidative status and altered cardiovascular function in several mammalian species; however, melatonin mediated alterations of uteroplacental capacity in sheep and cattle are lacking. Therefore, our laboratories are examining uteroplacental blood flow and fetal development during maternal melatonin supplementation. Using a mid- to late-gestation ovine model of intrauterine growth restriction, we examined uteroplacental blood flow and fetal growth during supplementation with 5 mg/d of dietary melatonin. Maternal nutrient restriction decreased uterine arterial blood flow, while melatonin supplementation increased umbilical arterial blood flow compared with non-supplemented controls. Although melatonin treatment did not rescue fetal weight in nutrient restricted ewes; we observed disproportionate fetal size and fetal organ development. Elevated fetal concentrations of melatonin may result in altered blood flow distribution during important time points of development. These melatonin specific responses on umbilical arterial hemodynamics and fetal development may be partially mediated through vascular melatonin receptors. Recently, we examined the effects of supplementing Holstein heifers with 20 mg/d of dietary melatonin during the last third of gestation. Uterine arterial blood flow was increased by 25% and total serum antioxidant capacity was increased by 43% in melatonin supplemented heifers vs. non-supplemented controls. In addition, peripheral concentrations of progesterone were decreased in melatonin supplemented heifers vs. non-supplemented controls. Using an in vitro model, melatonin treatment increased the activity of cytochrome P450 2C, a progesterone inactivating enzyme, which was blocked by treatment with the melatonin receptor antagonist, luzindole. Elucidating the consequences of specific hormonal supplements on the continual plasticity of placental function will allow us to determine important endogenous mediators of offspring growth and development.

Supplementation of Slow-Release Melatonin Improves Recovery of Ovarian Cyclicity and Conception in Summer Anoestrous Buffaloes (Bubalus bubalis)

The role of melatonin as a protective neurohormone against restoring cyclicity in summer anoestrous animals in photoperiod species has gained wider acceptance. This study was designed to uncover the evidence the slow-release melatonin (MLT) has on initiation of ovarian cyclicity and conception rate (CR) in summer anoestrous buffaloes. Thus, buffaloes diagnosed as summer anoestrous (absence of overt signs of oestrus, concurrent rectal examination and radioimmunoassay for serum progesterone at 10 days interval) were grouped as untreated (Group I, sterilized corn oil, n = 8) and treated (Group II, single subcutaneous injection of MLT @18 mg/50 kg bwt in sterilized corn oil, n = 20). Animals treated and detected in oestrus were artificially inseminated (AI) followed by division into Group III (second dose of MLT on 5th day post-AI, n = 8) and Group IV (no melatonin administration, n = 10). Blood samples were collected at 4 days interval for estimation of serum MLT, progesterone and oestrogen using radioimmunoassay kit. Mean oestrous induction rate (OIR), oestrous induction interval (OII), interoestrous interval (IOI) and CR were estimated. Compared to control, concentration of melatonin was significantly (p < 0.05) higher in treated group ranging from 14.34 ± 1.72 to 412.31 ± 14.47 pg/ml whereas other two hormones did not show any concentration difference. Melatonin-administered buffaloes showed significantly (p < 0.05) higher (90%) OIR with OII of 18.06 ± 1.57 days. Results showed improvement in conception rate in buffaloes administered with post-insemination melatonin. It can be concluded from the study that slow-release melatonin supplementation restored cyclicity in summer anoestrous animals resulting in improvement in conception rate in buffaloes.

Melatonin treatment in spring and reproductive recovery in sheep with different body condition score and age

With the aim to evaluate the effect of melatonin treatment on the advanced reproductive recovery in sheep with different body condition score (BCS) and age, 800 ewes were selected from two farms. These ewes (3-6 years old, multiparous and with BCS 2.5-4.0) were subdivided into two Groups (200 M and 200 C), balanced on their BCS and age. On 20 March, Group M was treated with one melatonin implant (18 mg). Group C was untreated. Males were introduced to the groups 35 days after treatment. Gestation was diagnosed between day 45 and 90 after mating by transabdominal ultrasonography. From day 150 to 190 after rams introduction, lambing date and newborns' number were recorded. The average time in days between male introduction and lambing resulted shorter in treated than in control ewes (166.4 ± 0.48 vs. 172.5 ± 0.50) (P < 0.05). At day 160 and 170 from ram introduction the fertility rate was higher in Group M than in C (P < 0.05). The overall fertility at day 190 from rams introduction showed no differences between Group M and C (337 and 339, respectively). At day 170 from male introduction the number of the 5-6 years-old lambed ewes were 2-fold higher than the youngers (P < 0.05). The animals with a BCS 3.5-4.0 had a faster response to male effect, and a shorter mean distance in days from rams introduction to lambing, compared to those scored 2.5-3.0 (166.1 ± 0.48 vs. 174.8 ± 0.51) (P < 0.05). We concluded that the ewes with BCS 3.5-4.0 and aged 5-6 years showed a better response to melatonin treatment in spring.

Melatonin promotes superovulation in sika deer (Cervus nippon)

In this study, the effects of melatonin (MT) on superovulation and reproductive hormones (melatonin, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and PRL) were investigated in female sika deer. Different doses (40 or 80 mg/animal) of melatonin were subcutaneously implanted into deer before the breeding season. Exogenous melatonin administration significantly elevated the serum FSH levels at the time of insemination compared with levels in control animals. During superovulation, the serum LH levels in donor sika deer reached their highest values (7.1 ± 2.04 ng/mL) at the point of insemination, compared with the baseline levels (4.98 ± 0.07 ng/mL) in control animals. This high level of LH was sustained until the day of embryo recovery. In contrast, the serum levels of PRL in the 80 mg of melatonin-treated group were significantly lower than those of control deer. The average number of corpora lutea in melatonin-treated deer was significantly higher than that of the control (p < 0.05). The average number of embryos in the deer treated with 40 mg of melatonin was higher than that of the control; however, this increase did not reach significant difference (p > 0.05), which may be related to the relatively small sample size. In addition, embryonic development in melatonin-treated groups was delayed.

Role of melatonin on production and preservation of gametes and embryos: a brief review

The aim of this brief review is to clarify the role of melatonin in the production and preservation of mammalian gametes and embryos. Melatonin is an indoleamine synthesized from tryptophan in the pineal gland and other organs that operates as a hypothalamic-pituitary-gonadal axis modulator and regulates the waxing and waning of seasonal reproductive competence in photoperiodic mammals. A major function of the melatonin rhythm is to transmit information about the length of the daily photoperiod to the circadian and circannual systems in order to provide time-of-day and time-of-year information, respectively, to the organism. Melatonin is also a powerful antioxidant and anti-apoptotic agent, which is due to its direct scavenging of toxic oxygen derivatives and its ability to reduce the formation of reactive species. Mammalian gametes and embryos are highly vulnerable to oxidative stress due to the presence of high lipid levels; during artificial breeding procedures, these structures are exposed to dramatic changes in the microenvironment, which have a direct bearing on their function and viability. Free radicals influence the balance between oxidation-reduction reactions, disturb the transbilayer-phospholipid asymmetry of the plasma membrane and enhance lipid peroxidation. Melatonin, due to its amphiphilic nature, is undoubtedly useful in tissues by protecting them from free radical-mediated oxidative damage and cellular death. The supplementation of melatonin to semen extender or culture medium significantly improves sperm viability, oocyte competence and blastocyst development in vitro.

Potency of melatonin in living beings

Living beings are surrounded by various changes exhibiting periodical rhythms in environment. The environmental changes are imprinted in organisms in various pattern. The phenomena are believed to match the external signal with organisms in order to increase their survival rate. The signals are categorized into circadian, seasonal, and annual cycles. Among the cycles, the circadian rhythm is regarded as the most important factor because its periodicity is in harmony with the levels of melatonin secreted from pineal gland. Melatonin is produced by the absence of light and its presence displays darkness. Melatonin plays various roles in creatures. Therefore, this review is to introduce the diverse potential ability of melatonin in manifold aspects in living organism.

Can advance of first lambing induced by melatonin implants influence the next lambing time in Sarda breed sheep?

Carcangiu, V., Mura, M. C., Bini, P. P., Vacca, G. M., Daga, C. and Luridiana, S. 2012. Can advance of first lambing induced by melatonin implants influence the next lambing time in Sarda breed sheep? Can. J. Anim. Sci. 92: 67–71. In adult sheep, exogenously administered melatonin from continuous slow-release implants has been shown to advance the onset of the breeding season by mimicking the stimulatory effect of short days. The aim of this study was to verify if treatment with one or two melatonin implants was effective in advancing the first conception in Sarda ewe lambs, and if this advance would also be seen in the second lambing too. In the first year, 600 ewe lambs were randomly assigned to groups M, M+M and C, each with 200 animals. On Jun. 30, group M received a single implant while group M+M received two implants. Group C was untreated. On Aug. 04, 25 rams were introduced in the groups and removed after 70 d. From these 600 animals the 420 head that lambed prior to Mar. 12 were chosen for the second year. These ewes were subdivided into two groups T1 (ewes who lambed between 2007 Jan. 01 and Feb. 10) and T2 (ewes which lambed between 2007 Feb. 11 and Mar. 12). Both in T1 and T2 the distribution of the animals in M, M+M and C group was maintained. In the first year, the treated animals lambed earlier (P<0.05) and showed higher numbers of lambed ewes at Feb. 10 (P<0.01) and at March 12 (P<0.05) compared with untreated control animals. The animals that showed an advance in the period of their first conception, also showed, in the second breeding year, an advance in the lambing time (P<0.001). This study provides evidence that the advance of first conception, obtained with melatonin treatment also influenced the reproductive activity in the following breeding season.

Melatonin supplementation alters uteroplacental hemodynamics and fetal development in an ovine model of intrauterine growth restriction

Using a mid- to late-gestation ovine model of intrauterine growth restriction (IUGR), we examined uteroplacental blood flow and fetal growth during melatonin supplementation as a 2 × 2 factorial design. At day 50 of gestation, 32 ewes were supplemented with 5 mg of melatonin (MEL) or no melatonin (CON) and were allocated to receive 100% [adequate; (ADQ)] or 60% [restricted (RES)] of nutrient requirements until day 130 of gestation. Umbilical artery blood flow was increased from day 60 to day 110 of gestation in MEL vs. CON dams, while umbilical artery blood flow was decreased from day 80 to day 110 of gestation in RES vs. ADQ dams. At day 130 of gestation, uteroplacental hemodynamics, measured under general anesthesia, and fetal growth were evaluated. Uterine artery blood flow was decreased in RES vs. ADQ dams, while melatonin supplementation did not affect uterine artery blood flow. Total placentome weight and placentome number were not different between treatment groups. Fetal weight was decreased by nutrient restriction. Abdominal girth and ponderal index were increased in fetuses from MEL-ADQ dams vs. all other groups. Fetal biparietal distance was decreased in CON-RES vs. CON-ADQ dams, while melatonin supplementation rescued fetal biparietal distance. Fetal kidney length and width were increased by maternal melatonin treatment. Fetal cardiomyocyte area was altered by both maternal melatonin treatment and nutritional plane. In summary, melatonin may negate the consequences of IUGR during specific abnormalities in umbilical blood flow as long as sufficient uterine blood perfusion is maintained during pregnancy.

Use of laparoscopic intrauterine insemination associated with a simplified superovulation treatment for in vivo embryo production in sheep: a preliminary report

This study evaluated the reproductive performance of sheep that were subjected to superovulatory treatment and intrauterine insemination with two different doses of semen. The main objective was to determine whether intrauterine insemination is associated with higher rates of embryo recovery than existing procedures. In the first experiment 30 Ojalada de Soria ewes were used at the end of their productive life and nine younger ewes of the same breed were used in Experiment 2. Synchronisation of oestrus was conducted with intravaginal sponges and the superovulation treatment consisted of an intramuscular injection of 210 IU pFSH and 500 IU eCG administered 24 h before sponge removal. After 48 h of sponge withdrawal, ewes were inseminated by laparoscopy. They were divided into two groups: low dose group (LD, 25 × 106 sperm; n = 14 Expt 1 and n = 5 Expt 2) and high dose group (HD, 100 × 106 sperm; n = 14 Expt 1 and n = 4 Expt 2). Embryos were recovered 7 days after the onset of oestrus by laparotomy and uterine flushing. Two blood samples were collected in order to analyse cortisol, at sponge insertion and the day the embryos were recovered. The same protocol was repeated twice in Experiment 1, with an interval of 2 months between two consecutive treatments. Results show a significant effect of the number of recovery on ovulation rate (21.7 ± 2.2 v. 11.8 ± 1.1 corpora lutea for first and second recoveries, respectively), and number of structures recovered (11.4 ± 1.6 v. 5.2 ± 1.1, P < 0.01). Differences of embryo performance in the second recovery compared with the first one were more evident in the LD group compared with the HD group. In Experiment 2, results reflected a significant superiority of the HD group compared with the LD group, especially rate of fertilisation, which was 25% higher. Sheep producing non-fertilised embryos had higher cortisol levels at the time of flushing than those with embryos (P < 0.01). It is concluded that the use of simplified and consecutive superovulatory treatments associated with intrauterine insemination is a potential means of obtaining embryos, although the response seems to depend on donor sheep age. The use of a higher number of sperm cells per millilitre results in better outcomes in terms of embryos produced.

Melatonin protects against clomiphene citrate-induced generation of hydrogen peroxide and morphological apoptotic changes in rat eggs

The present study was aimed to determine whether clomiphene citrate-induces generation of hydrogen peroxide in ovary, if so, whether melatonin could scavenge hydrogen peroxide and protect against clomiphene citrate-induced morphological apoptotic changes in rat eggs. For this purpose, forty five sexually immature female rats were given single intramuscular injection of 10 IU pregnant mare's serum gonadotropin for 48 h followed by single injections of 10 IU human chorionic gonadotropin and clomiphene citrate (10 mg/kg bw) with or without melatonin (20 mg/kg bw) for 16 h. The histology of ovary, ovulation rate, hydrogen peroxide concentration and catalase activity in ovary and morphological changes in ovulated eggs were analyzed. Co-administration of clomiphene citrate along with human chorionic gonadotropin significantly increased hydrogen peroxide concentration and inhibited catalase activity in ovary, inhibited ovulation rate and induced egg apoptosis. Supplementation of melatonin reduced hydrogen peroxide concentration and increased catalase activity in the ovary, delayed meiotic cell cycle progression in follicular oocytes as well as in ovulated eggs since extrusion of first polar body was still in progress even after ovulation and protected against clomiphene citrate-induced egg apoptosis. These results clearly suggest that the melatonin reduces oxidative stress by scavenging hydrogen peroxide produced in the ovary after clomiphene citrate treatment, slows down meiotic cell cycle progression in eggs and protects against clomiphene citrate-induced apoptosis in rat eggs.

Melatonin receptor 1A gene polymorphism associated with polycystic ovary syndrome

BACKGROUND/AIMS

Melatonin receptor 1A (MTNR1A) gene is a regulator of circadian rhythms and reproductive processes. The MTNR1A gene is also a potential candidate gene of polycystic ovary syndrome (PCOS). The aim of the present study was to determine whether or not the MTNR1A gene polymorphism is associated with a predisposition to PCOS.

METHODS

The single nucleotide polymorphism (SNP) rs2119882 in the MTNR1A gene was detected in 482 patients with PCOS and 522 healthy Chinese Han women. Subsequently, the association of MTNR1A gene variants with plasma glucose, insulin levels during oral glucose tolerance tests (OGTTs) and hormone levels was investigated.

RESULTS

The frequencies of genotypes and allelotypes of SNP rs2119882 differed significantly between PCOS cases and healthy controls (p < 0.001 and p = 0.002, respectively). SNP rs2119882 was associated with higher fasting plasma glucose concentrations (p = 0.021) and OGTT-induced insulin release at 0, 30, 60, and 120 min (all p < 0.05) in PCOS cases, as well as an increased homeostasis model assessment for insulin resistance (p = 0.005).

CONCLUSION

SNP rs2119882 is associated with PCOS.

Repeated superovulation using a simplified FSH/eCG treatment for in vivo embryo production in sheep

This study investigated the efficacy of a simplified repeated superovulation treatment (eCG plus FSH in a single dose, rather than the usual protocol of six decreasing doses of FSH) in the in vivo embryo production in Ojalada donor ewes during the breeding season. In vitro viability after vitrification and warming of embryos recovered from both treatments was also assessed. In addition, the study examined the effects of the concentration of anti-eCG antibodies before each eCG/FSH treatment on in vivo embryo production. Thirty-eight females at the end of their reproductive lives were given the decreasing (n = 19) or simplified (n = 19) superovulatory treatment up to three times at intervals of ≥ 50 d. The onset of estrus was 5 h earlier (P < 0.05) among ewes that received the eCG/FSH protocol (25.2 ± 0.80 h) than it was among those that received the decreasing superovulatory treatment (30.1 ± 1.0 h), but the two treatments did not differ significantly in ovulation rates or the number and viability of embryos recovered. Both of the superovulatory protocols were significantly (P < 0.05 to P < 0.01) less effective after the first application. After three superovulatory treatments, the average number of viable embryos per ewe was 14.1 ± 2.3 and 13.7 ± 2.5 in the decreasing and simplified protocols, respectively. High anti-eCG antibody concentrations just before the superovulatory treatment with eCG/FSH were associated with a significant decrease (P < 0.05) in the rates of fertilization, viability, and freezability, especially in the second and third recoveries. Repeated superovulatory treatments with eCG/FSH can provide an efficient means of producing high quality embryos in the ewes of endangered breeds at the end of their reproductive lives, although further studies are needed to characterize the response associated with high concentrations of anti-eCG antibodies.

Effects of exogenous melatonin on in vivo embryo viability and oocyte competence of undernourished ewes after weaning during the seasonal anestrus

This study investigated the effects of exogenous melatonin on embryo viability and oocyte competence in post-partum undernourished ewes during the seasonal anestrus. At parturition (mid-Feb), 36 adult Rasa Aragonesa ewes were assigned to one of two groups: treated (+MEL) or not treated (-MEL) with a subcutaneous implant of melatonin (Melovine(R), CEVA) on the day of lambing. After 45 d of suckling, lambs were weaned, ewes were synchronized using intravaginal pessaries, and fed to provide 1.5x (Control, C) or 0.5x (Low, L) times daily maintenance requirements. Thus, ewes were divided into four groups: C-MEL, C+MEL, L-MEL, and L+MEL. At estrus (Day=0), ewes were mated. At Day 5 after estrus, embryos were recovered by mid-ventral laparotomy and classified based on their developmental stage and morphology. After embryo collection, ovaries were recovered and oocytes were classified and selected for use in in vitro fertilization (IVF). Neither diet nor melatonin treatment had a significant effect on ovulation rate and on the number of ova recovered per ewe. Melatonin treatment significantly improved the number of fertilized embryos/corpus luteum (CL) (-MEL: 0.35 +/- 0.1, +MEL: 0.62 +/- 0.1; P = 0.08), number of viable embryos/CL (-MEL: 0.23 +/- 0.1, +MEL: 0.62 +/- 0.1; P < 0.01), viability rate (-MEL: 46.6%, +MEL: 83.9%; P < 0.05), and pregnancy rate (-MEL: 26.3%, +MEL: 76.5%; P < 0.05). In particular, exogenous melatonin improved embryo viability in undernourished ewes (L-MEL: 40%, L+MEL: 100%, P < 0.01). Neither nutrition nor exogenous melatonin treatments significantly influenced the competence of oocytes during IVF. Treatment groups did not differ significantly in the number of healthy oocytes used for IVF, number of cleaved embryos, or number of blastocysts and, consequently, the groups had similar cleavage and blastocyst rates. In conclusion, melatonin treatments improved ovine embryo viability during anestrus, particularly in undernourished post-partum ewes, although the effects of melatonin did not appear to be mediated at the oocyte competence level.

Effects of annual rainfall and farm on lamb production after treatment with melatonin implants in Merino sheep: a 4-year study

AIM

To determine the effects of annual rainfall and farm on the efficacy of melatonin implants in improving lamb production in Merino sheep in Spain.

METHODS

A study was conducted on 3,871 Merino sheep on six farms over a 4-year period (2004-2007). Melatonin implants were inserted during the second half of February or early March (winter) (Melatonin group) or not (Control group). Multinomial logistic regression was used to determine the effects of melatonin, farm and year, and their interactions, on reproductive outcomes. Regression analysis was used to examine the relationship between annual rainfall and the percentage of ewes lambing, percentage of lambs born to ewes lambing, and overall lambing percentage, for each year and treatment group within farm.

RESULTS

Annual rainfall, farm and treatment with melatonin, and their interactions, had a significant effect on the reproductive performance of ewes (p<0.001). Treatment with melatonin increased the percentage of ewes lambing (Melatonin group = 77 (SEM 4)%, Control group = 44 (SEM 7)%; p<0.0001), and overall lambing percentage (Melatonin group = 109 (SEM 1)%, Control group = 59 (SEM 2)%; p<0.0001). Treatment differences were especially pronounced in 2005 and 2006, when annual rainfall was exceptionally low; ewes in the Control group had the lowest lambing rates those years. Lambing rates and overall lambing percentage were positively correlated (p<0.05) with the amount of annual rainfall but the correlation coefficients were higher in the Control than Melatonin group.

CONCLUSIONS

Melatonin implants are an effective means of improving lamb production of Merino ewes, especially in harsh environments where low annual rainfall limits the availability of food. When melatonin treatment was used, however, the responses of flocks on individual farms were difficult to predict because within a year, responses did not occur on all farms.

Effects of melatonin treatment on follicular development and oocyte quality in Chios ewes - short communication

Follicular development and oocyte quality were assessed by laparoscopic observation and in vitro fertilisation, respectively, in melatonin-treated (Group M) and control (Group C) anoestrous Chios ewes (n = 10 in each group). Fourteen days after melatonin insertion, all ewes had laparoscopic evaluation of the follicular population followed by oocyte pick-up (OPU); on day 22 intravaginal progestagen sponges were inserted for 14 days. Two days after sponge removal the follicular population was re-evaluated and a second follicular aspiration was performed. Collected oocytes from the second OPU underwent in vitro maturation, fertilisation and culture. The number of large follicles was higher in Group M than in the control ewes during the first OPU and tended to be so (P = 0.06) at the second. Morphologically, oocytes collected from controls were of better quality than those from Group M; however, more oocytes collected from melatonintreated animals fertilised and developed in vitro . These results indicate that melatonin is a potent regulator of follicular development and oocyte competence during the anoestrous period of the ewe.

Melatonin and reproduction revisited

This brief review summarizes new findings related to the reported beneficial effects of melatonin on reproductive physiology beyond its now well-known role in determining the sexual status in both long-day and short-day seasonally breeding mammals. Of particular note are those reproductive processes that have been shown to benefit from the ability of melatonin to function in the reduction of oxidative stress. In the few species that have been tested, brightly colored secondary sexual characteristics that serve as a sexual attractant reportedly are enhanced by melatonin administration. This is of potential importance inasmuch as the brightness of ornamental pigmentation is also associated with animals that are of the highest genetic quality. Free radical damage is commonplace during pregnancy and has negative effects on the mother, placenta, and fetus. Because of its ability to readily pass through the placenta, melatonin easily protects the fetus from oxidative damage, as well as the maternal tissues and placenta. Examples of conditions in which oxidative and nitrosative stress can be extensive during pregnancy include preeclampsia and damage resulting from anoxia or hypoxia that is followed by reflow of oxygenated blood into the tissue. Given the uncommonly low toxicity of melatonin, clinical trials are warranted to document the protection by melatonin against pathophysiological states of the reproductive system in which free radical damage is known to occur. Finally, the beneficial effects of melatonin in improving the outcomes of in vitro fertilization and embryo transfer should be further tested and exploited. The information in this article has applicability to human and veterinary medicine.

Exogenous melatonin positively influences follicular dynamics, oocyte developmental competence and blastocyst output in a goat model

The role of melatonin in modulating mammalian reproduction is of particular interest; however, its effects on ovarian follicles and their oocytes still remain to be characterized. This study determined the influence of melatonin treatment on follicular growth patterns and on in vitro oocyte developmental competence. In a first experiment, the effects of melatonin supplementation on follicular dynamics were evaluated using daily transrectal ultrasonographies for 21 days, in 7 multiparous Sarda goats receiving a subcutaneous implant of 18 mg of melatonin and in 5 control untreated does. Melatonin caused more follicular waves (5.2 +/- 0.2 versus 4 +/- 0.3; P < 0.05) as the waves were shortened at around 2 days when compared with the non-melatonin treated control goats (P < 0.001). Oocyte developmental competence was evaluated in a second experiment by applying procedures for in vitro embryo production. There were no significant differences in the total number of oocytes obtained from 6 control (n = 192) and 7 melatonin-treated (n = 265) goats given follicle stimulating hormone to induce follicular development. Differences in oocyte developmental competence between the two groups became evident after in vitro fertilization and culture; melatonin increased the rate of cleaved oocytes in comparison with control animals (82.5 versus 63.4%; P < 0.001), advanced timing of embryo development and enhanced blastocyst output (31.5 versus 16.3%; P < 0.01). However, blastocyst quality, as evaluated by cryotolerance and gene expression analysis, was not found to be different between the groups. In conclusion, in vivo melatonin treatment is beneficial for increasing ovarian follicle turnover and improving oocyte developmental competence and kinetics of the blastocyst.

Undernutrition and exogenous melatonin can affect the in vitro developmental competence of ovine oocytes on a seasonal basis

This study evaluated the effects of exogenous melatonin and level of nutrition on oocyte competence, in vitro fertilization (IVF), and early embryonic development in sheep during seasonal anoestrus (SA) and the reproductive season (RS). Adult Rasa Aragonesa ewes were assigned randomly to one of four treatment groups in two experiments based on a 2 x 2 x 2 factorial design. Individuals were treated (+MEL) or not treated (-MEL) with a subcutaneous implant of melatonin for 42 days and then were fed 1.5 (Control, C) or 0.5 (Low, L) times the daily maintenance requirements for 20 days. Ewes were synchronized and mated at oestrus (Day = 0). On Day 5, ovaries were collected and oocytes were used for IVF. Season had a significant (p < 0.01) effect on the number of oocytes recovered (RS: 19.6 +/- 1.0; SA: 14.5 +/- 1.0) and the number of healthy oocytes (RS: 13.9 +/- 0.7; SA: 9.0 +/- 0.7). In the RS, neither nutrition nor melatonin had a significant effect on the evaluated oocytes quality parameters although melatonin implants appeared to reduce the number of unhealthy oocytes in the undernourished group (p < 0.05). During SA, in undernourished ewes exogenous melatonin tended to increase the number of healthy (L+MEL: 9.4 +/- 1.0, L-MEL: 7.6 +/- 1.4; p < 0.1), and significantly improved both cleaved oocytes (L+MEL: 7.0 +/- 0.7, L-MEL: 4.1 +/- 0.9; p < 0.05) and blastocyst rate (L+MEL: 37.2, L-MEL: 21.9%; p < 0.05). In conclusion, oocyte competence in ewes was affected by season, and melatonin implants appeared to improve developmental competence in the seasonal anoestrous period, particularly in experimentally undernourished ewes.

Simplified superovulatory treatments in Corriedale ewes

Two experiments were designed to evaluate the possibility of simplifying superovulatory treatments in Corriedale ewes with use of ovine FSH (oFSH). Ewes received intravaginal progestogen sponges for 14 days. In Experiment 1, several simplified schedules were tested. Ewes were treated with 176 NIH-FSH-S1 units' oFSH given as a single injection in saline, along with 500 IU eCG 48 h before sponge removal (Group A1), in four equal doses (B1), or given as a single injection in a polyvinylpyrrolidone vehicle (C1) 24 h before sponge removal. In Experiment 2, the simplified protocol that exhibited the most desirable results in Experiment 1 (A2) was compared with the same protocol, but using less oFSH (132 units) (B2) and with the most conventional protocol (176 units of oFSH in eight decreasing doses; C2). Estrus was detected and ewes were naturally mated. The ovarian response and embryo production were assessed on Day 6 after estrus. LH was measured at 6h intervals from pessary withdrawal. The onset of estrus and the pre-ovulatory LH surge were advanced (P<0.05) in ewes treated with FSH and eCG. In Experiment 1, protocol A1 produced a greater percentage of superovulated ewes compared to C1 (100.0 compared with 58.3%; P<0.05), increased ovulation rate (13.8 corpora lutea compared with 6.2 and 4.7 for B1 and C1, respectively; P<0.05), and tended to increase the number of transferable embryos compared to B1 (P=0.08). In Experiment 2, percentages of superovulated ewes and ovulation rates were similar among groups; however, Group A2 tended to have more large follicles (P=0.07) than C2. The number of transferable embryos was similar among the three treatments. In conclusion, the reduced-dose oFSH given once along with eCG is the most appropriate superovulatory treatment because it combines simplicity and a lesser dose of gonadotropin, which also implies a reduction in cost, without reducing embryo production.

Effects of ageing and exogenous melatonin on pituitary responsiveness to GnRH in ewes during anestrus and the reproductive season

The study examined the effect of melatonin implants on in vivo pituitary responsiveness to GnRH in control, fully productive (5.7+/-0.4 years old, n=17) and aged (10.7+/-0.3 years old, n=14) ovariectomized, estradiol-treated Rasa Aragonesa ewes. On 27 February, eight ewes in each age group received a single implant containing 18 mg melatonin. On 10 April, blood samples to be assayed for LH were collected at 10-min intervals over 4h (starting at 09:00 and 22:00 h). After samples 6 and 18 were collected, ewes received a single i.v. injection of GnRH (20 ng/kg liveweight). The pituitary response to GnRH was assessed using the difference between plasma LH concentrations before and after (highest value) each injection (DLH1, DLH2)), and the area under the LH response curve for 1h after each GnRH injection (AUC1, AUC2). On 23 September, the previously implanted ewes received a new melatonin implant and, on 17 November, all of the ewes were subjected to the same diurnal and nocturnal sampling protocols, again. Generally, non-implanted aged ewes exhibited a lower pituitary response to GnRH than did non-implanted control ewes, particularly in November and after the first injection (P<0.05 for DLH1 and AUC1 in both the diurnal and nocturnal tests). The response was significantly affected by the interaction of age and melatonin treatment, particularly in the diurnal tests (P<0.1 for DLH1 and AUC1, and P<0.05 for AUC2 in April; P<0.05 for DLH1, AUC1 and AUC2 in November), which indicated that exogenous melatonin increased LH levels after GnRH injections in aged ewes compared to non-implanted ewes, this effect being the opposite in control females. Thus, melatonin can restore in ewes the functionality of the neuroendocrine system, after it has been reduced by senescence.

The effect of melatonin treatment on the ovarian response of ewes to the ram effect

To determine the ovarian response to the ram effect after treatment with melatonin, on 8 March, 71 Rasa Aragonesa ewes were randomly assigned to either the treatment group and given an 18mg melatonin implant or the untreated group. On 19 April (day 0), rams were introduced into the flock. Melatonin treatment produced a significantly higher percentage of cyclic ewes at ram introduction (P<0.05). Melatonin-treated ewes had their first oestrus after ram introduction significantly earlier than did untreated ewes (P<0.0001), and the groups differed in the distribution of their ovarian response. Most (80%) of the treated ewes exhibited a silent ovulation followed by a cycle of normal duration, whereas about half (52%) of the untreated ewes exhibited a silent ovulation, a short cycle, and another silent ovulation followed by a cycle of normal duration (P<0.05). At ram introduction, melatonin-treated ewes, cyclic and non-cyclic, had higher mean plasma progesterone concentrations than did untreated ewes. The proportion of ewes that mated within the first 17 days of the mating period was significantly higher among the treated ewes than in the untreated ewes (P<0.0001). Furthermore, at lambing, 39% of the melatonin-treated ewes lambed within the first 17 days of the lambing period, while none of the untreated ewes lambed in that period. The untreated group exhibited peaks in mating between days 18 and 21, and particularly, between days 22 and 25, when the majority of ewes lambed; peaks did not occur in the treatment group. Treated and untreated ewes did not differ significantly in fertility, litter size and fecundity. In conclusion, melatonin treatment modifies the ovarian response to the ram effect in ewes, which leads to modifications in mating patterns, and consequently, the lambing curve.