Sperm Storage Tubules Research Articles

Morphology of the turkey vagina with and without an egg mass in the uterus

In this study we examined the gross anatomy of the uterus and vagina in turkeys in egg production. With no uterine egg mass, removal of the tunica serosa that enclosed the uterus revealed deep periodic in-folding of the muscularis transversely circumscribing the sac-like segment. When the connective tissue embracing the neutral buffered formalin fixed vagina was completely teased free, the exposed tubular segment was shaped as a counter-clockwise spiral or as a series of angular, random bends. The uterovaginal junction was flush with the uterine mucosa or projected slightly into the uterine lumen. With a uterine egg mass, the deep in-foldings of the uterus were abolished. The only alteration to the morphology of the vagina was that the uterovaginal junction appeared dilated and pressed into its juncture with the uterus. Whether an egg mass was present or not, uterovaginal junction folds that projected into the uterus possessed sperm storage tubules. An egg mass in the uterus compressed the uterovaginal junction folds, and its mucosa became contiguous with the uterine mucosa. Finally, from an evolutionary perspective, in the turkey and possibly other species possessing a nonintromittent phallus, vaginal pleomorphism may have been driven primarily by the need to accommodate the overall length of the vagina in a limited abdominal space and to a lesser extent on sexual selection.

Expression of Avian β-Defensin 3, an Antimicrobial Peptide, by Sperm in the Male Reproductive Organs and Oviduct in Chickens: An Immunohistochemical Study

The aim of this study was to determine whether chicken sperm express avian beta-defensin 3 (AvBD-3), an antimicrobial peptide, and retain it during the residence in the male and female reproductive tract. Immunocytochemistry to identify AvBD-3 was performed in the testis, epididymis, ductus deferens, ejaculated sperm, and utero-vaginal junction of the oviduct of inseminated hens. Reverse transcription-PCR analysis was also performed to confirm the synthesis of AvBD-3 by testicular cells and ejaculated sperm. The immunoreaction products for AvBD-3 were identified in the elongated spermatids attached to the seminiferous epithelium and in the sperm in the lumen of seminiferous tubules. Immunoreaction products were found in the sperm in the epididymal ducts and ductus deferens. In the ejaculated sperm, immunoreaction products were distributed in the midpiece and cephalic region of the tail of sperm, but not in the head. The AvBD-3 immunoreaction products were also identified in the sperm stored in the sperm storage tubules in the utero-vaginal junction. Reverse transcription-PCR analysis showed the expression of AvBD-3 mRNA in the testicular tissue, but not in the ejaculated sperm. These results suggest that AvBD-3 is synthesized by late stage of spermatids in the testis, and this molecule is retained by the sperm during the passage of male reproductive tract, and even in the sperm storage tubules of oviduct. The sperm AvBD-3 is assumed to play roles in protecting the sperm from the microbial infection and enable to survive in the male and female reproductive tracts.

REVIEW ARTICLE: Mechanism of Prolonged Sperm Storage and Sperm Survivability in Hen Oviduct: A Review

A unique property of the avian oviduct is to store sperm for a prolonged period. The sperm storage tubules (SST) are located in the utero‐vaginal junction of the oviduct, where sperm can be stored and survived for a few weeks after insemination or natural mating. The immune system in the oviduct is essential to prevent tissue infection by various microorganisms, and it may also affect the fate and survivability of sperm in the oviduct. Anti‐sperm immunoresponses including infiltration of leukocytes may be induced in the vagina of the oviduct. Sperm that will participate in fertilization may be selected by these immunoresponses. However, sperm stored in the SST may be protected from the immunoresponse by SST structures and transforming growth factor β, whose expression is increased during sperm storage in the SST. In this review, the mechanism of sperm survivability with reference to the regulation of anti‐sperm immunoresponses in hen oviduct is emphasized.

Microscopic organization of the sperm storage tubules in the oviducal gland of the female gummy shark (Mustelus antarcticus), with observations on sperm distribution and storage

Oviducal gland morphology, the microscopic organization of the terminal zone, and sperm storage were described in the female gummy shark (Mustelus antarcticus). Mustelus antarcticus is a nonplacental viviparous hound shark, which displays minimal histotrophy during embryonic development. The animals examined represented all stages of maturity and gestation. The oviducal gland was found to have the same fundamental zonation as in most chondrichthyans. Using recent terminology, the oviducal gland of chondrichthyans has an anterior club zone, followed by a papillary zone, both of which produce jelly that surrounds the egg, a baffle zone that elaborates the tertiary egg envelope and a terminal zone, where sperm storage occurs. Each zone is composed of simple tubular glands that connect to transverse grooves, which extend the full width of the gland. The exception is the terminal zone, which does not have transverse grooves but consists of individual tubules. The microscopic organization and histochemical nature of the zones display similar patterns to those of other chondrichthyan genera. Tubules of the terminal zone contain four types of cell: ciliated cells, alcian blue-positive secretory cells, periodic acid-Schiff and alcian blue-negative secretory cells, and secretory columnar cells. These tubules end in recesses, the sperm storage tubules, which extend beyond the periphery of the baffle zone. Sperm were stored in the sperm storage tubules of all maturing and mature animals examined. Of note is the observation of stored sperm in an animal 1 year prior to first ovulation. Sperm were also observed throughout the uterine sphincter, body of the uterus, isthmus, and oviduct of maturing and mature animals, and in the uterine sphincter of an immature animal. These sperm represent immediately postcopulation aggregations of sperm and sperm in the process of migrating to the site of storage or to the site of fertilization.

Changes in the expression of interleukin-1β and lipopolysaccharide-induced TNF factor in the oviduct of laying hens in response to artificial insemination

The aim of this study was to determine the physiological significance of interleukin-1beta (IL1B) and lipopolysaccharide-induced TNF factor (LITAF) in the fate of sperm in the oviduct of laying hens after artificial insemination (AI). Laying hens were inseminated with fresh semen, PBS or seminal plasma and tissues from different oviductal segments were collected to observe the general histology, changes in the mRNA expression of IL1B and LITAF and the localization of positive cells expressing immunoreactive IL1B (irIL1B). Semi-quantitative RT-PCR was used to observe the changes in mRNA expression of these molecules in the infundibulum, uterus, utero-vaginal junction (UVJ), and vagina after insemination. Intact sperm in the lumen and between the primary or secondary folds of the vagina were found until 6 h after insemination but were degraded at 12 h. The mRNA expression of IL1B and LITAF was significantly increased in the vagina until 6 h after AI but remained unchanged in the other oviductal segments. In the tissue of the vagina and UVJ, irIL1B was localized in the mucosal stroma. The number of irIL1B-positive cells was increased in the vagina but almost unchanged in UVJ after insemination with semen. Significant changes were not observed in the mRNA expression and irIL1B-positive cells in the vagina after PBS or seminal plasma insemination. The increase of IL1B and LITAF in the vagina may lead to sperm degradation and elimination by cilia of surface epithelium, whereas their lower levels in UVJ may permit sperm to survive in sperm storage tubules.

Seasonal variation in the oviduct of female Agkistrodon piscivorus (Reptilia:Squamata): An ultrastructural investigation

The annual oviductal cycle of the Cottonmouth, Agkistrodon piscivorus, is described using electron microscopy. This is only the second such study on a snake and the first on a viperid species. Specimens were collected in reproductive and nonreproductive condition throughout the year and five ultrastructurally unique regions were recognized: the anterior infundibulum, posterior infundibulum, glandular uterus, nonglandular uterus, and vagina. Except for the anterior infundibulum and vagina, which exhibit no seasonal variation in ultrastructure, the oviduct becomes highly secretory at the start of vitellogenesis. This includes the entire luminal border of the uterus, the tubular glands of the glandular uterus, and the luminal border and sperm storage tubules of the posterior infundibulum. The secretory materials produced in the oviduct vary among regions of the oviduct, and also can vary among time periods in the same region of the oviduct. Variation is especially evident in the sperm storage tubules. Secretory activity in the sperm storage tubules ceases after ovulation, but the tubular glands of the glandular uterus remain secretory until parturition, at which time secretory activity in the varying sections of the oviduct decreases dramatically. After parturition, the oviduct remains in a dormant state until the next reproductive season. The seasonal variation in oviducal morphology mirrors the temperate primitive reproductive cycle known for some pitvipers. Uterine glands of A. piscivorous are more similar in secretory activity to those of an oviparous lizard than a viviparous colubrid snake, suggesting variation in uterine gland morphology between snakes of different families.

Turkey Sperm Reside in the Tubular Glands in the Urodeum Following Artificial Insemination

A turkey hen in egg production requires 48 h after the last insemination to maximize the number of sperm in the uterovaginal junction sperm-storage tubules. Where the sperm that continue to fill the oviductal sperm-storage sites during this 48-h period reside remains unknown. Histological sections of the juncture of the vagina with the urodeum, the central compartment of the cloaca, revealed deep tubular glands containing periodic acid-Schiff-positive secretory material. When examined 36 h after the last artificial insemination, sperm were observed in the lumen of the tubular glands associated with the urodeum. We suggest that sperm reside in the tubular glands within the urodeum and are released in association with the secretory activity of the tubular glands. These sperm then may ascend the vagina to continue to populate the sperm-storage tubules. Alternatively, the sperm in the tubular glands of the urodeum may be evidence of spermatorrhea and have no functional role in the fertilization process.

Serotonin Localization in the Turkey Vaginal but not Sperm Storage Tubule Epithelia

Elucidating the cellular and molecular mechanisms regulating sperm selection and transport in the vagina of the hen had been the focus of a limited amount of research over the past decade. New observations indicate the presence of nonneuron endocrine cells in the epithelia lining the lumina of the turkey hen vagina and uterovaginal junction. Although no cells in the vagina or uterovaginal junction surface epithelia exhibited argentaffin staining, typical of cells containing neurosecretory granules, cells restricted to the vaginal and uterovaginal junction but not the sperm storage tubule epithelia were immunoreactive positive to serotonin. We speculate that if released into the vaginal lumen and submucosa, serotonin could augment cilia and sperm tail beat frequencies and facilitate smooth muscle contraction, respectively. If this is the response to sperm at insemination, it would represent the first evidence of a local control mechanism responding to sperm in the turkey vagina.

Ultrastructure of Anterior Uterus of the Oviduct and the Stored Sperm in Female Soft‐Shelled Turtle,Trionyx sinensis

Ultrastructure of sperm storage in female soft-shelled turtle, Trionyx sinensis was examined under light and electron microscopes. Sperm storage tubules are restricted to the anterior of the uterus. These tubules developed either by folding or fusion of the oviductal mucosal folds and are lined by both ciliated and secretory cells. Ciliated cells are characterized by a few microvilli and prominent cilia in the apical membranes. A prominent feature of the secretory cell is the presence of secretory granules in the supranuclear region. The size, shape, and electron density of these granules vary markedly. The secretory product is released mainly by exocytosis into the oviductal lumen, where it appears as flocculent material. The unique structure in the base of the epithelium, the basal border of the cell -- the basal lamina -- and a blood vessel layer, is presumed to be a important barrier, by which the nourishment exchange and the microenvironment maintenance are ensured. The gland cell is presented with numerous, round, membrane-bound secretory granules of moderate to high electron densities. We divide these granules into three types according to their appearance: (1) membrane bounded granules with high-homogeneous electron density, (2) membrane bounded granules with moderate-homogeneous electron density, (3) membrane bounded, electron dense granules with concentric structures. These granules are presented as different stages of the secretions in the gland cell. The junction complexes are markedly distributed between cells, which are important in keeping stability and the microenvironment maintenance of the sperm storage tubules. Sperm stored in the tubules are heterogeneous in cytology. In addition to the mature sperm in the lumen, sperm with large chromatic granules are found, which are presumed to be immature sperm and are being in the process of nuclear condensation. Several spermatozoa in the tubules are exhibited with definitive indications of degeneration of the nuclei. The nuclear volume increases. The electron density of the central cores in mitochondria declines, combined with the deterioration of concentric membrane structure. Those changes are possibly due to the long time storage of the sperm in sperm storage tubules, and the leakage of reactive oxygen species is suggested to be a major cause. We conclude that the ultrastructure character of sperm storage in the oviduct of Trionyx sinensis is unique, in addition to having a basal function in secretion and the cilia swing, the tubules also provide an available microenvironment for the sperm to long time stored. The degenerative sperm in the tubules might be related to paternity-specific reproductive adaptations, and the sperm competition might occur during long time storage.

Sperm aggregations in female Agkistrodon piscivorus (Reptilia:Squamata): A histological and ultrastructural investigation

Upon copulation in female Agkistrodon piscivorus, sperm migrate up the oviduct to sperm storage tubules (SSTs) in the posterior infundibulum. The epithelium of the SSTs is composed of ciliated and secretory cells and differs ultrastructurally from that of the epithelium lining the lumen of the posterior infundibulum. Sperm pass through an area composed primarily of ciliated cells at the opening of each gland before aligning themselves in parallel arrays with their nuclei facing an area composed primarily of secretory cells at the base of the tubules. Sperm are also found embedded inter- and intracellularly in the SSTs. The secretory vacuoles in the SSTs become highly electron dense after the start of the fall mating season along with the synthesis of lipid droplets. Histochemical analysis reveals that the alteration in secretory material density is caused by the production of neutral carbohydrates. Some sperm remain in aggregates in the nonglandular section of the posterior uterus until the time of ovulation. However, ultrastructural evidence indicates these sperm degrade before ovulation. Therefore, sperm in posterior aggregates have no role in fertilization of ovulated ova. The data presented here support the hypothesis that infundibular sperm storage is the mode that snakes utilize to sequester viable sperm until ovulation.

Alkaline phosphatase reactivity in the vagina and uterovaginal junction sperm-storage tubules of turkeys in egg production: implications for sperm storage

1. Currently there remains contradictory information on the localisation and possible role of alkaline phosphatase (AP) in the chicken and Japanese quail oviducts. 2. Using turkeys with a hard-shelled egg in their uteri, vaginal and uterovaginal junction mucosae were stretched and fixed as whole mounts prior to the histochemical localisation of AP activity. 3. Scattered AP reactive cells were observed in the vaginal and uterovaginal junction surface epithelia and intense AP reactivity of the sperm-storage tubule (SST) epithelium, localised to its apical border. 4. We suggest that such AP reactivity in hens in egg production may reflect cell differentiation and proliferation in the vagina and SST and possibly a mechanism for the transfer of lipid from the SST epithelia to resident sperm.

Specific features of in vivo and in vitro sperm storage in birds

This review focuses on some of the main features of sperm selection and storage in birds mainly on the basis of studies performed in poultry species, with emphasis on the initial selection of sperm at the female vagina level prior to migration towards the sperm storage tubules. Sperm originating from low-quality males or subjected to inappropriate in vitro storage conditions are rapidly discarded, resulting in impaired fertility in corresponding flocks. In the absence of accessible and appropriate technology for matching the ‘storing’ potential of sperm in the oviduct, conditions for prolonged sperm storage under a liquid (through the use of semen extenders) or a solid state (cryopreservation) have received only limited attention, despite their potential interest to facilitate male and female management in poultry flocks. Despite this, technology for short-term liquid storage is currently used in turkeys, guinea fowl and muscovy ducks and also in progress in chickens. In addition, technology for cryopreservation of avian semen has become available for some species (chicken, goose) to facilitate the management of genetic resources, including the preservation of rare and economically important breeds.

Expression of transforming growth factor-β isoforms and their receptors in utero-vaginal junction of hen oviduct in presence or absence of resident sperm with reference to sperm storage

Our goal was to determine whether transforming growth factor beta (TGFbeta) isoforms were involved in the process of sperm survivability in the sperm-storage tubules (SST) in the utero-vaginal junction (UVJ) of hen oviduct. The birds were artificially inseminated. The mRNA expressions of three types of TGFbeta isoforms (TGFbeta2, TGFbeta3, and TGFbeta4) and three types of receptors (TbetaR1, TbetaR2, and TbetaR3) were examined in the presence or in the absence of resident sperm in SST by semi-quantitative reverse transcriptase-PCR. The mRNA expression of TGFbetas and TbetaRs in sperm was also examined. Immunocytochemistry and western blot were performed for TbetaR2 to confirm its localization in UVJ. The sperm were observed at least 10 days after insemination by histology. The mRNA expressions of TGFbetas and TbetaRs were significantly increased in UVJ in the presence of resident sperm in SST. The mRNA expressions of TGFbetas and TbetaRs were also observed in sperm. Immunohistochemistry revealed that TbetaR2 were located in lymphocytes in UVJ and SST cells. The presence of TbetaR2 in UVJ was also confirmed by western blot. These results suggest that enhanced expressions of TGFbetas and TbetaRs in UVJ may protect sperm in SST, probably by suppressing anti-sperm immunoreactions.

Sperm Mobility: Deduction of a Model Explaining Phenotypic Variation in Roosters (Gallus domesticus)1

In previous work, variation in sperm mobility phenotype was attributed to the proportion of ejaculated fowl sperm containing dysfunctional mitochondria. In the present work, latent mitochondrial dysfunction was inferred from patterns of sperm egress from the oviduct's sperm-storage tubules. In addition, experiments were performed to help explain how mitochondrial function could be compromised in viable sperm cells. Confocal microscopy demonstrated that sperm Ca2+ content differed between low and high sperm-mobility phenotypes when sperm were stained with rhod-2 AM, a Ca2+ -specific dye. Fluorescence was associated with the nuclear envelope, a variant of the endoplasmic reticulum, and greater fluorescence was observed in sperm from low sperm-mobility males. Fluorescence was reduced by 50% when motile sperm were rendered immotile by incubation with a Ca2+ chelator. Thus, a relationship was established between a dynamic intracellular Ca2+ pool and sperm motility. Sperm N-methy-D-aspartic acid (NMDA) receptors were inferred by the action of D-homocysteinesulfinic acid, a potent NMDA receptor agonist. Seminal plasma from low sperm mobility males was characterized by an elevated glutamate concentration. Thapsigargin, which inhibits the smooth endoplasmic reticulum Ca2+ pump and thereby promotes Ca2+ efflux, rendered sperm immotile. This effect was blocked by cyclosporin A, which prevents the formation of the mitochondrial permeability transition pore (PTP) in response to elevated mitochondrial Ca2+ content. In summary, we propose that 1) glutamate enables Ca2+ uptake into sperm before ejaculation, 2) excessive Ca2+ uptake triggers formation of the PTP in a subpopulation of sperm, and 3) sperm mobility is decreased in proportion.

Changes in the expression of estrogen receptor mRNA in the utero-vaginal junction containing sperm storage tubules in laying hens after repeated artificial insemination

The objective was to determine whether expression of estrogen receptor (ER) mRNA in the utero-vaginal junction (UVJ) of laying hens was altered after repeated artificial insemination (AI). Semi-quantitative RT-PCR was used to determine the expression of mRNA of the two types of receptor, ERα and ERβ. Only ERα mRNA was expressed in all segments of the oviducts of both virgin and artificially inseminated birds, whereas ERβ mRNA was expressed in ovarian follicles but not in the oviduct. The expression of ERα mRNA in the UVJ was significantly decreased after repeated AI, whereas that in the uterus was not significantly different between virgin and inseminated birds. Since estrogen may be involved in maintaining the sperm storage function of sperm storage tubules, the decreased expression of ERα mRNA in the UVJ after repeated AI may contribute to reduced fertility in these birds.

Age effect of broiler breeders on fertility and sperm penetration of the perivitelline layer of the ovum

The objective of this study was to determine the age effect of a broiler breeder flock on duration of fertility and number of spermatozoa penetrating the perivitelline layer overlying the germinal disc (SP/mm 2 GDIPVL). Moreover, in the second half of the flock's reproductive life, the effect of using ejaculates of young roosters (CA2) in artificial insemination (AI) on the above parameters of fertility was estimated. The commercial flock of broiler breeder hens ( n = 100) was inseminated six times from 31 to 62 weeks of age. Additional inseminations, with ejaculates of roosters aged 31 and 36 weeks (CA2), were performed at 56 and 62 weeks of age. AI was performed during two consecutive days (D0 and D1) with an insemination dose of 125 × 10 6 spermatozoa/0.06 ml containing pooled ejaculates. The following parameters were studied: the effective and maximum duration of fertility (De and Dm), percent of fertility on different days after AI (FD10, FD15 and FD20), indices of duration of sperm penetration (DSP, SP ≤ 3/GDIPVL), SP/mm 2 GDIPVL in eggs laid on successive days after insemination of hens at different age, and correlations between some fertility indices. Both for De and Dm, the highest values were noted after AI of the layers at 36 weeks of age (14.8 ± 0.49 and 17.4 ± 0.46 days, respectively), which were about 2 days longer than at 56 weeks. All fertility indices decreased gradually with age, starting from AI at peak egg production (31–36 weeks of age), while the use of ejaculates from CA2 did not help to increase them significantly. Correlation coefficients between SP/mm 2 GDIPVL and the other fertility indices were positive and highest for eggs laid on D3. It is concluded that high De values can be obtained from broiler breeders in adequate environmental and technological conditions of AI. It is suggested that the age-related decrease in fertility is more pronounced in females, in which the efficiency of sperm storage tubules decreases. The present fertility indices indicate the possibility of lengthening AI intervals, especially at peak egg production.

Effects of Repeated Artificial Insemination on the Structure and Function of Oviducal Sperm Storage Tubules in Hens

The goal of this study was to determine the mechanism by which the fertility was declined by repeated artificial insemination (AI) in laying hens. The structures of sperm storage tubules (SST) and lymphocytes population in the uterovaginal junction (UVJ) of Rhode Island Red hens showing a declined fertility after repeated AI with Tosa-jidori semen and of virgin hens were examined histologically in experiment 1. Then, the sperm storage abilities of those hens were examined in experiment 2. In experiment 1, the SST was swollen with thinning of epithelium, and the population of lymphocytes was greater in the UVJ of hens showing a declined fertility after repeated AI compared with virgin hens. In hens showing a lower fertility, few sperm were present in SST, and lymphocytes invading into SST lumen after AI were observed (experiment 2). These results suggest that repeated AI may cause the destruction and abnormality in the functions of SST, and anti-sperm immunoresponse may occur in those SST in the birds used for current study. In these birds sperm could not be retained in SST, resulting in decline of fertility. Such abnormality of SST may be one of the factors involved in the decline of fertility by repeated AI in the other breeds that are reported elswhere.

Fertilized female quail avoid conspecific males: female tactics when potential benefits of new sexual encounters are reduced

In a pair of experiments, we determined whether recently fertilized Japanese quail, Coturnix japonica, with less to gain from new sexual encounters than females without sperm in their sperm-storage tubules, would reduce their probability of sexual harassment by avoiding conspecific males (experiment 1) and affiliating with conspecific females (experiment 2). We found that after copulating with a male, female quail that were laying fertilized eggs spent less time near males and more time near females than female quail laying unfertilized eggs. Furthermore, females that were denied access to males for 14 days (i.e. those with empty sperm-storage tubules) and females that failed to lay fertile eggs after copulation behaved similarly towards conspecific males and females. We interpret these results as indicating that the cost to female quail of interacting with males of their species has led to the evolution of female tactics to avoid male harassment when females' eggs are successfully fertilized and potential reproductive benefits of additional sexual encounters are reduced.

Localization of Aquaporins in the Sperm Storage Tubules in the Turkey Oviduct

Oviductal sperm storage tubules (SST), located at the uterovaginal junction, are the primary site of sperm storage in turkeys. Sperm reside within these storage sites and may be released via a dynamic interaction between sperm mobility and a fluid current generated by the SST epithelial cells. In this study, aquaporins 2, 3, and 9 (proteins that form water channels in the plasmalemma of a variety of cells) were immunocytochemically localized within the apical aspect of the epithelial cells that form the SST. These observations support the contention that the SST epithelial cells are capable of water exchange that may interact with sperm residing within the SST.

Practical aspects of fertility in poultry

Birds, reptiles and insects (e.g. Hymenoptera) share fundamental similarities in their reproductive strategies due to the presence, in the female tract, of specialized sites in which spermatozoa may reside for prolonged periods upon a single mating. In avian species, two distinct storage sites are present, one located in the utero-vaginal junction and the other in the lower portion of the infundibulum. At both sites, spermatozoa are stored in sperm storage tubules (SSTs) which are discrete, generally non-branched invaginations of the luminal epithelium (see review by Bakst et al., 1994). The SSTs located in the uterovaginal junction are considered as the main site of residence of spermatozoa upon their deposition in the lower portion of the vagina. The fertilizing potential of females along the reproductive season is at first dependent on their ability to store and maintain adequate populations of spermatozoa in their SST in order to repeatedly provide the site of fertilization with sufficient numbers of “fit” spermatozoa after each ovulation. As a consequence in poultry species, eggs from females with prolonged sperm storage potential have also a natural tendency to maintain optimal fertility rates for prolonged periods. This situation may be highly desirable to sustain high fertility in the case of partial failure of the males during the season.This review is an attempt to address the main intrinsic and extrinsic factors capable of favouring or altering fertility in poultry species. Unfortunately, most of the information available is obtained from two species, namely the domestic fowl and turkey, which, in certain circumstances, may not reveal enough to pinpoint the controlling factors of fertility in other poultry species.