Biomedical subjects

P Chemineau

Publications and source records attributed to P Chemineau.

At least 19 recordsLinked to original sources

PubMed2003

Origin of cerebrospinal fluid melatonin and possible function in the integration of photoperiod.

Melatonin, which is synthesized at night by the pineal gland, is present in the cerebrospinal fluid (CSF), but its entry site and its role in this compartment are not known. Using several approaches, we tested the hypothesis that melatonin enters the CSF through the pineal recess, an evagination of the third ventricle. CSF melatonin concentrations are higher near the pineal gland than in the anterior part of the third ventricle, and decrease markedly (80%) after sealing off the pineal recess. Moreover, ultrastructure and permeability analyses of the pineal-CSF interface showed that melatonin could reach the CSF either via delivery in situ by protruding pinealocytes that make direct contact with the CSF or via extracellular secretion and interstitial fluid draining into the ventricular lumen. These data indicate that melatonin in the CSF probably originates from a few pinealocytes of the basal part of the pineal gland neighbouring the pineal recess. Melatonin carried to the brain by the blood appears to be able to mediate the effects of photoperiod on reproduction, but it is unclear whether melatonin in CSF may fine-tune this response both in terms of timing and amplitude. It is critical to determine which pathway, blood or CSF, allows melatonin to reach its central targets more efficiently.

Animals↗

PubMed2002

Male effect in seasonally anovulatory lactating goats depends on the presence of sexually active bucks, but not estrous females.

A study was conducted in subtropical northern Mexico (26 degrees N) to determine whether the presence of estrous females can improve the response of seasonally anovulatory goats to the introduction of bucks in the group. The induction of estrous activity was studied in three groups of anovulatory lactating goats during seasonal anestrus. These females were of the Mexican Creole breed. In the control group (sexually inactive (SI), n = 20), two control (SI) bucks exposed to normal seasonal daylength variations were used. In the second group (SI + E, n = 20 + 3), two control males were also used, but in addition, three females of the group were in estrus at the time of male introduction. In the third group (sexually active, SA + E, n = 19 + 4), anovulatory females were exposed to two bucks made sexually active by exposure to 2.5 months of long days (16L:8D) followed by two subcutaneous 18 mg melatonin implants, and four estrous females were also present when introducing the bucks. In all groups, males were introduced on 15 March and estrous detection was conducted twice daily for 15 days. The sexual activity of the bucks was observed from 08:00 to 10:00 h during the first five days of exposure to females. More females displayed estrous behavior in the first 15 days following the introduction of the males in the SA + E group (18/19) as compared with the SI or SI + E groups (2/20 and 0/20, respectively; P < 0.001). No difference was observed between the two latter groups. Thirteen females of SA + E group showed a second estrus between days 6 and 11 (short estrous cycle duration: 5.4 +/- 0.4 days). By contrast, in the SI group none showed a second estrus. The sexual behavior of the males in the SA + E group was greater as compared with that of the males in SI and SI + E groups (over 80% of the total sexual activity recorded in the three groups; P < 0.001). By contrast, no differences were found between SI and SI + E males. These results indicate that the presence of estrous females alone at the time of buck introduction is not sufficient to induce an adequate stimulation of seasonally inactive males. The use of sexually active bucks is necessary to induce reproductive activity in anovulatory females, whereas preparation of the bucks with long days followed by melatonin implants allows them to gain such a capacity.

Animals↗

PubMed2002

Neuroendocrine interactions and seasonality.

Sheep in temperate latitudes are seasonal breeders. Of the different seasonal cues, photoperiod is the most reliable parameter and is used by animals as an indication of the time of the year to synchronize endogenous annual rhythms of reproduction and physiology. The photoperiodic information is transduced into neuroendocrine changes through variations in melatonin secretion from the pineal gland. Melatonin triggers variations in the secretion of luteinizing hormone-releasing hormone, luteinizing hormone and follicle stimulating hormone (LHRH/LH/FSH) responsible for seasonal changes in reproductive activity. In female sheep, the seasonal changes in the hormonal LH pattern mainly reflect an increase in the negative feedback exerted by estradiol under long days on the frequency of pulsatile LH secretion. The resulting seasonal inhibition of LH secretion involves the activation of monoaminergic and especially dopaminergic systems by estradiol. Other types of physiological regulation subject to seasonal changes such as voluntary food intake (VFI), fat metabolism, body mass and pelage growth also occur in sheep, goats or related wild species. Several neuroendocrine intermediates seem to be shared by these different systems and may participate in their synchronization, providing the advantage that this helps mammalian species to adapt to their environment.

Animal Nutritional Physiological Phenomena↗

PubMed2002

Genetic variability in melatonin secretion originates in the number of pinealocytes in sheep.

Genetic variability in plasma melatonin concentrations in ewes results from variations in pineal weight. This study investigated whether it is due to a difference in the number of pinealocytes, or in their size. Two groups of lambs were assigned before birth to being extremes (18 High and 21 Low) by calculating their genetic value on the basis of the melatonin concentrations of their parents. Lambs were bled from 1 week of age until 14 weeks of age. Pineal gland, brain and pituitary weights, length and width of the brain, and length of the hypothalamus were recorded. A significant effect (ANOVA) of genetic group (P<0.05) and age (P<0.05) was detected on mean nocturnal plasma melatonin concentrations, as soon as the first week after birth (mean +/- s.e.m.; High: 51.7 +/- 10.7 vs Low: 31.9 +/- 3.2 pg/ml). There was no difference between the two genetic groups in any of the brain parameters measured, but the pineal glands of the High group were heavier and contained significantly more pinealocytes (High: 27.8 +/- 2.4 vs Low: 21.0 +/- 2.4 x 10(6); P<0.05) than those in the Low group. The mean size of pinealocytes did not differ between the two genetic groups. Thus, the genetic variability in nocturnal plasma melatonin concentrations in sheep is expressed by 1 week of age and higher levels of secretion are the consequence of larger pineal glands containing a greater number of pinealocytes.

Analysis of Variance↗

PubMed2002

Induction of sexual activity in lactating anovulatory female goats using male goats treated only with artificially long days.

Two experiments were conducted to determine the response of Creole male goats treated with long days and melatonin implants, and the response of the anovulatory does to male effect using males treated only with artificially long days. All animals were allocated to open sheds. In Exp. 1, one group of males was under natural photoperiod (CG; n = 7); the second group was submitted to 2.5 mo of long days followed by the insertion of two s.c. melatonin implants (LD+MEL; n = 7); the third group was subjected only to 2.5 mo of long days (LD; n = 7). Testicular weight was measured every 2 wk. Plasma testosterone concentrations were determined weekly. A treatment x time interaction was detected (P < 0.001) for testicular weight and plasma testosterone concentration. In the LD+MEL and LD groups, testicular size and plasma testosterone levels varied in a similar way, but differed from those observed in CG (P < 0.001). In this latter group, testicular weight displayed seasonal variations and peaked in June, whereas in treated groups this peak occurred in March. In CG, testosterone varied in a seasonal manner and plasma concentrations increased in June and remained elevated throughout the study. In experimental groups, testosterone increased in February and peaked in March. In Exp. 2, one group of males was left under natural photoperiod (CG, n = 5) and the other one was submitted to 2.5 mo of artificially long days (LD, n = 4). On March 16, two control and two treated males were put in contact with 20 and 19 females, respectively. Sexual behavior of the bucks was observed during the 5 d following male introduction. Progesterone assays and estrous behavior were used to determine ovarian and behavioral responses of the females to teasing. The anogenital sniffing, nudging, and mount instances registered in LD-treated males were greater than those observed in CG (P < 0.05). Of the does exposed to CG, none ovulated and only two of 20 females displayed estrous behavior. All does in contact with LD-treated males ovulated and showed at least one estrous behavior during the 15 d following joining (P < 0.001). These results indicate that the sexual activity of male goats from subtropical latitudes can be induced using only artificially long days. In addition, males treated in this way are capable of stimulating sexual activity in anovulatory females by the male effect.

Animals↗

PubMed2002

Melatonin and seasonal reproduction: understanding the neuroendocrine mechanisms using the sheep as a model.

The mechanisms by which melatonin controls seasonal reproduction are poorly understood. The use of a large animal model, namely the sheep, has allowed progress in the understanding of these mechanisms, and is the subject of this review. Firstly, the contribution made by large animal models to demonstrating that melatonin acts in the hypothalamus and the identification of this hypothalamic target is reviewed. Secondly, the way in which large animal models have facilitated the demonstration of a specific mechanism of release of melatonin in the cerebrospinal fluid and, thus, raised the question of the route used by melatonin to reach its central targets is discussed. Finally, the human and agricultural relevance of the data presented is considered.

Animals↗

PubMed2002

Sheep as a mammalian model of genetic variability in melatonin.

Large inter-individual variability in plasma melatonin concentration at night is a common mammalian trait. In sheep, it varies from < 50 pg ml(-1) to > 800 pg ml(-1) but is very consistent within individuals. This inter-individual variability is under strong genetic control, which depends on melatonin secretion from the pineal gland, but not on melatonin catabolism. This genetic variability does not originate from differences in the synthetic enzymes or from a difference in melatonin secretion per mg of tissue, but from a difference in pineal size, which is highly variable among lambs of the same age and live weight. The genetic difference among lambs is already expressed at birth and is due to a difference in the number of pinealocytes rather than in their size. Pineal size and number of pinealocytes correlate strongly with plasma melatonin concentrations. The variability in pineal mass is not associated with the variability in any other organ (for example, the pituitary). The identification of genetic markers in the genome associated with the size of the pineal gland may lead to identification of genes involved in development of the mammalian pineal gland. Divergent selection of sheep on the basis of plasma melatonin concentrations could be used to constitute a mammalian model for extreme plasma concentrations.

Animals↗

PubMed2001

Comparison of immune parameters of sheep with naturally high or low plasma concentrations of melatonin.

Studies in rodents and humans have suggested that the pineal gland and its secretory product melatonin play an important role in the modulation of the immune system. In this study, we tested the hypothesis of a difference in immune parameters between ewes with naturally high vs. low circulating melatonin. Thus, two comparable groups of 10 Ile-de-France sheep were selected from a large flock, for their naturally high and low plasma concentrations of melatonin. The mean plasma melatonin concentrations during daytime (09:00 hr) and nighttime (24:00 hr) were, respectively, 9 and 664 pg/mL (high group) and 5 and 169 pg/mL (low group; P<0.01). Animals from both groups were subjected to various in vitro and in vivo measurements of the characteristics of their immune system. The total number of white blood cells (lymphocytes, polymorphonuclears, and monocytes) and the assessment of the sub-populations of blood lymphocytes (T4, T8, T19, B, and monocytes) did not show any significant differences between the two groups, sampled during day or night. The level of blood leukocytes proliferation after in vitro culture with ConA, LPS, or CWF stimulation, before or after experimental immunization, did not reveal any differences. No significant differences were registered in the production of antibodies between the two groups of animals. The results of the present experiment suggest that in natural conditions a high level of circulating melatonin does not modify the activity of the immune system in sheep.

Animals↗

PubMed2001

Biology of mammalian photoperiodism and the critical role of the pineal gland and melatonin.

In mammals, photoperiodic information is transformed into a melatonin secretory rhythm in the pineal gland (high levels at night, low levels during the day). Melatonin exerts its effects in discrete hypothalamic areas, most likely through MT1 melatonin receptors. Whether melatonin is brought to the hypothalamus from the cerebrospinal fluid or the blood is still unclear. The final action of this indoleamine at the level of the central nervous system is a modulation of GnRH secretion but it does not act directly on GnRH neurones; rather, its action involves a complex neural circuit of interneurones that includes at least dopaminergic, serotoninergic and aminoacidergic neurones. In addition, this network appears to undergo morphological changes between seasons.

Animals↗

PubMed2001

Nocturnal melatonin and prolactin plasma concentrations in sheep selected for fertility in autumn lambing'.

Ewes selected for fertility in autumn lambing were used to evaluate correlated responses in nocturnal hormone levels. Four jugular blood samples were obtained during nighttime in August from each of 113 selected and 69 control ewes. Melatonin levels were lower for selected ewes (143 +/- 14 pg/mL) than for control ewes (184 +/- 13 pg/mL), and melatonin levels decreased with increases in estimated breeding values (EBV) for fertility (-2.23 +/- 0.79 pg mL(-1) x %(-1)). Prolactin levels were higher for selected ewes (90 +/- 7 ng/mL) than for control ewes (52 +/- 7 ng/mL), but significant line x ewe age interaction was also observed, with smaller differences in prolactin levels in 2-yr-old and older ewes (74 +/- 7 vs. 56 +/- 9 ng/mL for select and control ewes, respectively; P < 0.20 before and P = 0.05 after logarithmic transformation). Prolactin levels increased with both fertility EBV (1.23 +/- 0.53 ng mL(-1) x %(-1)) and maternal birth weight EBV (9.0 +/- 4.0 ng x ml(-1) kg(-1)). Heritability estimates were 0.43 (P < 0.02) for melatonin levels and 0.11 (P > 0.25) for prolactin levels. Thus, we conclude that selection for fertility in autumn lambing has affected patterns of melatonin and prolactin secretion during the dark phase.

Age Factors↗

PubMed2001

Induction of sexual activity of male creole goats in subtropical northern Mexico using long days and melatonin.

The aim of this study was to determine whether the sexual activity of local male Creole goats in subtropical Mexico can be induced during the non-breeding season by a long-day treatment followed by insertion of two melatonin implants. The experiment was carried out in the Laguna region in the State of Coahuila, Mexico (26 degrees N). Fourteen male goats were allocated to two balanced groups (n = 7 each) according to body and testicular weights. Males were kept together in two separate groups and fed lucerne hay for ad libitum intake and 300 g of commercial concentrate and had free access to water and mineral blocks. The control group remained in open sheds under natural photoperiod and ambient temperature conditions. The experimental group was placed in a light-proof building and exposed to 2.5 mo of long days (16 h of light/d) from November 1 to January 15. On January 16, each male received two s.c. melatonin implants and was exposed to natural photoperiodic changes in an open shed. In the control group, testicular weight exhibited seasonal variations; the highest value occurred on May 30 (146 +/- 10 g). Treated males reached maximum testicular weight earlier (March 15; 147 +/- 11 g), and sperm quality from January to March was higher than that observed in the control group (P < 0.05). Treatment caused an increase in LH pulse frequency (2.0 +/- 0.5 vs 0.3 +/- 0.2 pulse/8 h in February, 4.6 +/- 1.1 vs 0.1 +/- 0.1 pulse/8 h in March; experimental vs control group, respectively). In the control group, plasma testosterone remained low until mid-June and increased thereafter to remain elevated until the end of the study. In the experimental group, elevated plasma testosterone was observed from February to April and from July to November. Treating male goats in subtropical latitudes with artificial long days and melatonin can induce an intense sexual activity during the natural nonbreeding season.

Animals↗

PubMed2000

Association between expression of reproductive seasonality and alleles of the gene for Mel(1a) receptor in the ewe.

To determine whether a link exists between reproductive seasonality and the structure of the gene for melatonin receptor Mel(1a), the latter was studied in two groups of Mérinos d'Arles (MA) ewes previously chosen for their genetic value, which took into account their own out-of-season ovulatory activity adjusted by environmental parameters and that of their relatives. The genomic DNA of 36 ewes found regularly cycling in spring (group H) and that of 35 ewes never cycling in spring (group L) during the 2-3 yr before the present study was prepared, and the cDNA corresponding to almost all exon II was amplified and checked for the presence of MnlI restriction sites. The presence (+) or absence (-) of an MnlI site at position 605 led to genotypes "++", "+-", and "--", whose frequencies differed significantly (P < 0.001) between the H and L groups: 52.8%, 47.2%, and 0% vs. 28.5%, 42.9%, and 28.5%, respectively. Sequencing of exon II cDNA in group L ewes with genotype -- showed the presence of only one allele - with 4 mutations, while that in ewes with genotype ++ showed different types of alleles unrelated to the H or L groups. These + alleles exhibited a combination of 1 to 7 of the 8 mutations recorded in the part of exon II studied. The genotyping of 29 ewes from the more seasonal Ile-de-France breed indicated that 38% of animals had a -- genotype and exhibited the same mutations as in the MA ewes. Finally, a comparison of (125)I-melatonin binding to membrane preparations of pars tuberalis showed a lower number of binding sites (P < 0. 0005) in MA ewes with genotype ++ than in those with genotype -- (43. 2 +/- 4.4 vs. 75.4 +/- 8.4 fmol/mg protein in genotype ++ and genotype --, respectively). In conclusion, the data show an association between genotype -- for site MnlI at position 605 and seasonal anovulatory activity in MA ewes.

Alleles↗

PubMed2000

Male reproductive condition is the limiting factor of efficiency in the male effect during seasonal anestrus in female goats.

Two experiments were conducted to determine whether the failure of males to induce sexual activity in goats during seasonal anestrus is due to unresponsiveness of females to male stimulus or insufficient stimulation from males. In the first study, one group of males (sexually inactive, SI; n = 4) was kept under natural photoperiod while the other (sexually active, SA; n = 4) was subjected to 2.5 mo of long days (16L:8D) and received 2 s.c. implants of melatonin. Two mo later, 2 different flocks of anovulatory goats previously separated from bucks were exposed to either SI (n = 34) or SA (n = 40) bucks. Progesterone assays and estrous behavior were used to determine ovarian and behavioral responses of the females to teasing. Of the goats exposed to SI males, only 2 ovulated, and none showed estrous behavior during the 35 days of the study. In contrast, all females (40 of 40) in contact with SA males ovulated and showed at least one estrous behavior during the first 11 days following male introduction (P < 0.001). Overall, 38 of 40 females stimulated with SA bucks were diagnosed pregnant at Day 35, according to progesterone assay (versus 0 in SI-treated group: P < 0.001). To control for a possible difference of responsiveness between flocks, the experiment was repeated 1 yr later using a single flock of goats divided into 2 groups. Again, over the first 14 days, 1 of 33 goats showed estrous behavior in the SI-treated group versus 27 of 33 in the SA-treated group (P < 0.001). Therefore, treating bucks with long days and melatonin increased their teasing capacity to induce sexual activity in females during anestrus. These results indicate that the absence of response to teasing at this time of the year is not due to female unresponsiveness, but to insufficient stimulation from the male.

Animals↗

PubMed1999

Sheep 5HT2A receptors: partial cloning of the coding sequence and mRNA localization by in situ hybridization in the ewe hypothalamus.

UNLABELLED: Serotonin and serotonin receptors of class II (5HT2-R) are thought to be involved in the neural mechanisms which regulate the LH release associated with photoperiodic changes in sheep. A specific premammillary hypothalamic area displaying a significant binding of 3H-ketanserin, a potent 5HT2-R antagonist, was previously identified. The aim of the present study was to ascertain by in situ hybridization (ISH) that 5HT2-R mRNA-containing cells were also present in this specific hypothalamic area. Total RNA was prepared from sheep pars tuberalis/median eminence, and a cDNA fragment of 546 bp was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) using degenerated primers deduced from the human and rat 5HT2A-R sequences. After cloning and sequencing, the sheep nucleotide sequence had the highest homology (85.1-92.3%) with the other known mammalian 5HT2-R or 5HT2A-R sequences. Homology with other 5HT-R subtypes or other monoamine receptors was much lower, 60% at maximum. After ISH using sense and antisense 35S-riboprobes, specific labelling was found in different parts of the hypothalamus, especially in the mammillary bodies where the binding was higher. Within the hypothalamus, the density of labelled cells, mainly neurons, varied considerably. It was maximal in the mammillary bodies and also in a restricted ventral region of the premammillary hypothalamus located from about 500/700 micrometer to 1200/1400 micrometer in front of the mammillary recess, where 3H-ketanserin binding was previously reported. IN CONCLUSION: (1) the structural study of the sequence indicated that the new cloned cDNA corresponds to the sheep 5HT2-R class and, probably, to the 5HT2A-R subtype and (2) the ISH studies revealed that a restricted area of the premammillary hypothalamus shows a large number of 5HT2-R mRNA-containing neurons.

Animals↗

PubMed1999

Evidence for an annual reproductive rhythm independent of food availability in male Creole goats in subtropical northern Mexico.

The aim of this study was to determine if there is a seasonal pattern of sexual activity dependent on food availability in male Creole goats in subtropical Mexico. The study was conducted in the Laguna Region in the State of Coahuila, Mexico (26 degrees N). Male Creole goats (n = 8) were kept in a shed, fed alfalfa ad libitum and given 200 g of concentrate daily throughout the study. Live weight and testicular weight were determined every 2 wk. Sexual behavior and sperm production were determined monthly. Blood samples were obtained weekly to determine testosterone plasma concentrations. All variables were subjected to sinusoidal modeling procedures and showed important seasonal variations (P < 0.0001) with different phase angles for body weight, testicular weight and testosterone plasma concentrations. The nadir of live weight occurred in November and the peak in May. The lowest testicular weight (90 g) and testosterone plasma concentrations (0.1 ng/mL) were observed in January and February, respectively, while the peaks were observed in July and August (145 g and 10 ng/mL, respectively). Ejaculation latency also varied during the study, being low between May and November (96 sec) and reaching a peak in April (183 sec). Minimum number of spermatozoa per ejaculate occurred between February and April (1.4 x 10(9) cells/ejaculate) while the maximum number was observed between May and September (2.8 x 10(9) spermatozoa/ejaculate). Progressive sperm motility was low between January and April (3.04 on average) and high between May and November (about 3.55 on average). The percentage of live spermatozoa diminished between January and April (68% in April) and then increased to values around 80% between May and November. These results lead us to conclude that male Creole goats in Northern Mexico, fed constantly throughout the year, exhibit seasonality in their reproductive activity. Intense sexual activity occurred between May and December.

Animal Feed↗

PubMed1999

Daily and light-at-night induced variations of circulating 5-methoxytryptophol (5-ML) in ewes with respectively high and low nocturnal melatonin secretion.

The aim of the present study was to determine whether the genetic differences previously reported in ewe plasma melatonin concentrations were correlated with differences in the synthesis and release of other 5-methoxyindoles. To determine if 5-methoxytryptophol (5-ML), which is known to be present in large amounts in the sheep pineal gland, is released, as is melatonin, into the general circulation, and if some temporal relationships between 5-ML and melatonin release could be observed, two groups of ewes were selected with respect to their endogenous melatonin secretion: in the first experiment, ten ewes from the low melatonin group (low group) and ten ewes from the high melatonin group (high group). 5-ML was measured every hour during a 24-hr period by radioimmunoassay. In all ewes, 5-ML was released during day-time, the rhythm of 5-ML concentrations being inversely related with the melatonin rhythm. Both day-time and night-time 5-ML concentrations were higher in the ewes from the high group than in the ewes from the low group (14.7 +/- 1.0 pg/mL plasma versus 6.4 +/- 0.3 pg/mL plasma during the day, 3.1 +/- 0.2 pg/mL plasma versus 1.9 +/- 0.2 pg/mL plasma during the night). The 5-ML/melatonin ratio appeared much higher during the day than during the night but was very similar in both groups (day-time: 1.03 in the high group versus 1.16 in the low group, night-time: 0.01 in both groups). In a second experiment, six low group and seven high group ewes were submitted to 1 hr of extra light at night. 5-ML increased and melatonin decreased during extra light. Our results clearly show for the first time a daily variation in circulating 5-ML, and that the strong genetic contribution in the variability in melatonin concentrations in sheep are clearly correlated with a similar variability in 5-ML concentrations. Whether 5-ML, like melatonin, plays a physiological role in the different adaptation processes to the environment remains to be determined.

Adaptation, Physiological↗

PubMed1999

Genetic variability in plasma melatonin in sheep is due to pineal weight, not to variations in enzyme activities.

This study was conducted to determine the origin of the high variability in the mean nocturnal plasma melatonin concentration (MC) in sheep. Two extreme groups of 25 lambs each [low (L) and high (H)] were obtained by calculating their genetic value on the basis of the MC of their parents. The MC of lambs was significantly higher in the H group than in the L group (L: 189.7 +/- 24.4 vs. H: 344.1 +/- 33.0 pg/ml, P < 0.001). Within each group, 13 lambs were slaughtered during the day (D) and 12 lambs during the night (N). Pineal weight was significantly higher in the H group than in the L group (L: 83.5 +/- 6.7 vs. H: 119.1 +/- 9.2 mg, P < 0.01) but did not differ between D and N. The amount of melatonin released in vitro per milligram of pineal gland, the arylalkylamine N-acetyltransferase (AANAT) activity, the AANAT protein content, and the level of AANAT mRNA differed significantly between D and N but not with genetic group. Hydroxyindole O-methyltransferase activity did not differ significantly between D and N or between genetic groups. Therefore, the genetic difference in MC between the two groups of lambs was attributed to a difference in pineal size, not in enzymatic activity of the pinealocytes.

Acetylserotonin O-Methyltransferase↗

PubMed1999

Implications of recent advances in reproductive physiology for reproductive management of goats.

The control of reproduction in goats is interesting for technical reasons (synchronization of kiddings, adjustment to forage availability or to economy), and for genetic reasons (identification and dissemination of improved genotypes). The use of short-light rhythms leads to markedly increased production of semen per buck and prevents occurrence of a 'resting' season. Recent identification of a bulbourethral lipase in goat spermatozoa opens new perspectives in sperm preservation. Light plus 'short day' treatments also allow induction of out-of-season oestrous cycles and ovulations leading to enhanced fertility. Repeated use of eCG provokes the production of antibodies, delays the timing of ovulation and causes a reduction in fertility after fixed-time artificial insemination. All steps of embryo production, freezing and transfer are now controlled and allow the attainment of satisfactory numbers of kids born per donor female, which are compatible with the development of the technique for exchanging genotypes between countries. In vitro production of embryos allows high development rates to be achieved after in vitro maturation and fertilization of oocytes, and will ensure the production of synchronous populations of one-cell zygotes at the stage required by new biotechnologies.

Animal Husbandry↗