Sperm transport into the oviducts of heifers mated early in oestrus

Frozen Bovine Semen Storage, Semen Handling, and Site of Deposition

Artificial insemination (AI) is an effective strategy to distribute semen from elite sires and improve the genetics of a herd. Commercial studs provide a fertile semen product to their customers. Consequently, the maintenance of sire fertility is dependent upon appropriate semen storage, handing, and site of semen deposition. When retrieving a straw of frozen semen, the cane (and canister containing canes) should be held below the frost-line and limited to 8 seconds in the neck of the tank. After appropriate thawing, and continuous thermoregulation of the AI gun containing the thawed semen, semen should be deposited in the uterine body.

Motility, oxidative status and morphology of frozen-thawed bovine semen are not impacted by fatty acid exposure in vitro

While sperm migrate within the reproductive tract of cows experiencing negative energy balance (NEB), they come into contact with elevated concentrations of non-esterified fatty acids (NEFA). For this reason, this study aimed to investigate the effects of three different NEFA - palmitic acid (PA), stearic acid (SA), and oleic acid (OA) - on bovine sperm motility, kinetic parameters, oxidative status, and morphology. Frozen thawed semen samples from Bos taurus bulls were incubated with varying concentrations of each fatty acid, and the sperm's characteristics were analysed at different time points. Computer-Assisted Sperm Analysis (CASA) was employed to assess sperm motility and kinetic parameters. Concurrently, the production of the reactive oxygen species (ROS) and total antioxidant capacity were measured to determine the oxidative status. Additionally, sperm morphology was evaluated. In Experiment 1, different concentrations of PA did not show significant effects on total motility, progressive motility, or any kinetic parameters analysed. Similarly, PA did not have a significant impact on the oxidative status or sperm morphology. In Experiment 2, SA at various concentrations did not lead to significant changes in total motility, progressive motility, or any kinetic parameters evaluated. Furthermore, SA did not affect oxidative status or sperm morphology. In Experiment 3, the concentrations of OA used did not result in significant changes in total motility, progressive motility, or any kinetic parameters studied. Likewise, OA did not induce any alterations in oxidative status or sperm morphology. Overall, the results from all three experiments indicate that PA, SA and OA, at the in vitro conditions and tested concentrations, do not exert detrimental effects on bovine sperm function and morphology. These results provide insights that contribute to our understanding of how fatty acids can impact the reduction of fertility rates in cows facing NEB. This, in turn, lays the foundation for additional critical investigations in this area. Further studies are necessary to validate these findings in vivo.

Transcriptomic profiling of the bovine endosalpinx and endometrium to identify putative embryokines

The objectives of the present study were to characterize the expression of genes encoding for cell signaling ligands in the bovine endosalpinx and endometrium and analyze spatial changes in gene expression. RNA sequencing was performed for the endosalpinx from the ampulla of the oviduct and endometrium from the upper and middle uterine horn and uterine body at day 2 after ovulation from ipsilateral and contralateral sides relative to the ovulatory ovary. Of the 17,827 unique mRNA transcripts mapped, 2,072 were affected by cranial-caudal position in the reproductive tract and 818 were affected by side (false discovery rate < 0.05). There were 334 genes encoding for cell signaling ligands, with 128 genes having greater than two transcripts per million on average. A total of 81 cell signaling ligand genes were affected by position and 24 were affected by side. A data set of the transcriptome of two to four cell embryos was used to identify cell signaling ligand genes that were highly expressed in the ampulla for which there was high expression of the receptor in the embryo. The most expressed ligand-receptor pairs were PSAP/SORT1, MIF/CXCR4, GPI/AMFR, and KITLG/KIT. These cell signaling ligands, as well as others whose gene is expressed in the endosalpinx and endometrium, may influence early embryonic development. Spatial changes throughout the reproductive tract highlight the distinctive expression profile of the oviduct versus the endometrium, including a set of the identified genes encoding for cell signaling ligands, and highlight the local influence of the ovary. The results also show the continuity of expression for large numbers of genes in the reproductive tract.NEW & NOTEWORTHY Examination of the transcriptome of the endosalpinx and endometrium revealed the degree to which gene expression in the reproductive tract varies spatially. The expression of genes encoding cell signaling molecules that could potentially regulate embryonic development was also identified.

Interaction of sperm cells with the female reproductive tract in cattle: Focus on neutrophil extracellular trap formation

After insemination of cows, either naturally or artificially, the deposition of semen into the vagina or uterus results in an immune reaction which is based on polymorphonuclear neutrophil activity. Sperm must be resistant to immune system actions of the female for an adequate time to allow fertilization to occur. Neutrophils, however, either directly phagocytize sperm through cell-cell attachment or entrap sperm cells in neutrophil extracellular traps (NETs), structures consisting of neutrophil nuclear DNA and associated proteins. In this review article, the interaction of neutrophils and sperm cells in t cattle will be described, with a special focus on the formation of neutrophil extracellular traps (NETs).

The effect of GnRH administration/insemination time on follicular growth rate, ovulation intervals, and conception rate of Nili Ravi buffalo heifers in 7 -day-CIDR Co-synch

The present study aimed to compare two different insemination times (72 vs 84 h) associated with an ovulation induction (GnRH) in a 7-day CIDR Co-synch to improve the conception rate of Nili Ravi buffalo heifers. Forty Nili Ravi buffalo heifers were randomly separated into two treatments based on artificial insemination (AI) timing (72 vs 84 h). All heifers were subjected to controlled internal drug release (CIDR), containing 1.38 g of progesterone for 7 days. On CIDR removal, both treatments received 150 µg of prostaglandin intramuscularly. In 7-day CIDR Co-synch (n = 20), animals were injected 100 µg of GnRH administration intramuscularly and inseminated concurrently at 72 h after CIDR removal. The remaining half (n = 20) were injected and inseminated concurrently at 84 h of CIDR removal. Pregnancy diagnosis was performed on day 40 of timed artificial insemination (TAI) with ultrasound. The follicular growth rate between 72 h after PGF_2α/CIDR removal to pre-ovulatory follicle in 7-day CIDR Co-synch was more (0.102 ± 0.005 mm vs 0.079 ± 0.003 mm; P = 0.01) at 84 than 72 h. The interval from GnRH administration/TAI to ovulation was high (26.8 ± 1.64 h vs. 15.1 ± 1.25 h, P = 0.01) in 72 than 84 h. Conception rates were considerably higher in buffalo heifers inseminated at 84 h (65%) than 72 h (25%) in 7-day CIDR Co-synch protocol. In conclusion that in Nili Ravi buffalo heifers, GnRH administration/TAI after 84 h of CIDR removal allows greater follicular growth rate and shortens interval from AI to ovulation compared to the GnRH administration/TAI after 72 h of CIDR removal in 7-day CIDR-Co-synch protocol.

Sperm interaction with the uterine innate immune system: toll-like receptor 2 (TLR2) is a main sensor in cattle

During the passage through the female reproductive tract, sperm interact with various compartments and their immune systems. The immune system that protects the female against pathogens also could destroy sperm or prevent them from reaching the site of fertilisation. In particular, the uterine innate immune response is crucial from the perspectives of both the sperm and the uterus. Following insemination, sperm immediately start to trigger inflammation in the uterus by entering uterine glands and activating an innate immune response. In cattle, the activation occurs mainly via TLR2 signalling, if not the only one, between sperm and the uterine epithelium lining the glands. This acute immune response is manifested as the upregulation of mRNA expression of IL8, TNFA, IL1B , and PGES . As a consequence, many sperm are trapped by polymorphonuclear neutrophils, the first and major component of innate immunity. The sperm-induced uterine innate immune responses apparently serve to clear the uterus of excess sperm and, importantly, prepare the endometrium for implantation. Pathophysiological conditions in the uterus seriously disrupt this phenomenon, and thus could directly decrease fertility.

Sperm interactions with the female reproductive tract: A key for successful fertilization in mammals

Sperm migration through the female genital tract is not a quiet journey. Uterine contractions quickly operate a drastic selection, leading to a very restrictive number of sperm reaching the top of uterine horns and finally, provided the presence of key molecules on sperm, the oviduct, where fertilization takes place. During hours and sometimes days before fertilization, subpopulations of spermatozoa interact with dynamic and region-specific maternal components, including soluble proteins, extracellular vesicles and epithelial cells lining the lumen of the female tract. Interactions with uterine and oviductal cells play important roles for sperm survival as they modulate the maternal immune response and allow a transient storage before ovulation. The body of work reported here highlights the importance of sperm interactions with proteins originated from both the uterine and oviductal fluids, as well as hormonal signals around the time of ovulation for sperm acquisition of fertilizing competence.

High temperature-humidity index compromises sperm quality and fertility of Holstein bulls in temperate climates

Rising temperatures caused by climate change have adverse effects on cattle physiology, welfare, health, and reproduction. Heat stress in cows affects the oocyte and embryo directly through heat shock on cellular function. Fewer data are available on the effect of high temperatures on male fertility. Temperature-humidity index (THI) is a measure for assessing the risk of heat stress that combines the effects of temperature and humidity. The aim of this study was to determine the relationship between THI and fresh or frozen-thawed sperm quality of Holstein bulls kept in temperate climates. Bull sperm data of 29,170 ejaculates from 933 bulls collected at 3 Dutch artificial insemination centers between 2015 and 2018 were evaluated. The assessed variables included total sperm motility and morphology of fresh semen, and total sperm motility, morphology, and progressive motility of frozen semen 0 and 3 h after thawing. In addition, 56-d nonreturn rates were analyzed. The assessed effects were season and THI on the day of semen collection and during spermatogenesis (30 d before collection), bull, age of bull, year, and location. Bulls were divided into 2 categories according to their age: young (<36 mo) and older (>36 mo). Overall sperm quality of young bulls improved as age increased. No effect of THI on fresh sperm variables was observed in either young or older bulls. However, high THI at spermatogenesis negatively affected the cryotolerance of sperm cells. Sperm cells from young and older bulls showed a pronounced decrease (14-18%) of the assessed variables 3 h after thawing after the increase of THI during spermatogenesis in autumn. Remarkably, older bulls were more sensitive to THI at spermatogenesis compared with semen collection, showing up to a 3.8 times higher negative effect on frozen sperm quality. However, an elevated THI at semen collection produced a tendency toward decreased 56-d nonreturn rates as the age of the bull increased. Although this decrease was up to 4%, rising temperatures may still cause important economic losses in the future. For the first time, the present study confirmed that climate compromises not only sperm quality, but also dairy bull fertility.

Prenatal Bisphenol A Exposure Alters Epithelial Cell Composition in the Rhesus Macaque Fetal Oviduct

Bisphenol A (BPA) is an endocrine disrupting compound that is a pervasive environmental contaminant. Although it has been reported to affect the development of a variety of fetal reproductive tissues, data on the effect of fetal BPA exposure on oviducts were extremely limited and were only available in mice. To determine if there are adverse effects of gestational BPA exposure on fetal oviduct, we exposed pregnant rhesus macaques with female fetuses to oral or nonoral BPA during the last trimester of gestation (day 100 to term). After the treatment, fetal oviducts were collected for morphology evaluation. BPA exposure altered the percentages of different cell types (ciliated, nonciliated, and secretory) in the fetal oviduct and resulted in a significant high ciliated cell population in the BPA-exposed fetal oviduct. The distribution of ciliated cells on the epithelium in the BPA-exposed fetal oviduct was also altered. Gestational BPA exposure reduced the expression of mucosubstance and uteroglobin in secretory cells in the fetal oviduct. A comparison of the outcome of the fetal oviduct studies with similar outcomes previously reported in the lung from the same fetuses demonstrates that BPA exhibits opposite effects in these two organs. In conclusion, the BPA-associated alterations in the fetal oviduct could potentially affect the oviduct morphology and function later in life with a negative impact on fertility. The mechanisms of action of the differential response in the oviduct and the lung to BPA exposure require further investigation.

Bovine oviduct epithelial cells suppress the phagocytic activity of neutrophils towards sperm but not for bacteria in vitro: Immunofluorescence and electron microscopic observations

Previously, we reported that polymorphonuclear neutrophils (PMNs) are constantly existent in the bovine oviduct fluid during the pre-ovulatory stage under physiological conditions. Moreover, incubation of PMNs with bovine oviduct epithelial cells-conditioned medium (BOEC-CM) resulted in suppression of their phagocytic activity for sperm. During pathophysiological conditions, cows may be inseminated by infected semen which exposes oviductal PMNs to allogenic sperm simultaneously with pathogens. This study aimed to visually investigate the role of oviduct epithelium in regulating the phagocytic behavior of PMNs toward sperm as a physiological stimulus, with Escherichia coli (E. coli) as a pathological stimulus. In our experiment, PMNs were incubated for 2 h in BOEC-CM. Phagocytosis was then assayed by co-incubation of these PMNs either with sperm, E. coli, or latex beads. BOEC-CM significantly suppressed the direct phagocytosis of PMNs for sperm, but did not affect their phagocytic activity for E. coli or latex beads. Additionally, an investigation with scanning electron microscopy revealed that BOEC-CM suppressed the formation of DNA-based neutrophil extracellular traps (NETs) for sperm entanglement. BOEC-CM did not alter NETs formation towards E. coli. A quantification of NETs formation using an immunofluorescence microscopy showed that the areas of NETs formation for E. coli were significantly larger than those formed for sperm. Our data clearly show that the bovine oviduct, through secretions, protects sperm from phagocytosis by PMNs and eliminates bacterial dissemination through maintaining the phagocytic activity of PMNs towards bacteria.

Review: The epic journey of sperm through the female reproductive tract

Millions or billions of sperm are deposited by artificial insemination or natural mating into the cow reproductive tract but only a few arrive at the site of fertilization and only one fertilizes an oocyte. The remarkable journey that successful sperm take to reach an oocyte is long and tortuous, and includes movement through viscous fluid, avoiding dead ends and hostile immune cells. The privileged collection of sperm that complete this journey must pass selection steps in the vagina, cervix, uterus, utero-tubal junction and oviduct. In many locations in the female reproductive tract, sperm interact with the epithelium and the luminal fluid, which can affect sperm motility and function. Sperm must also be tolerated by the immune system of the female for an adequate time to allow fertilization to occur. This review emphasizes literature about cattle but also includes work in other species that emphasizes critical broad concepts. Although all parts of the female reproductive tract are reviewed, particular attention is given to the sperm destination, the oviduct.

Inducing ovulation with oestradiol cypionate allows flexibility in the timing of insemination and removes the need for gonadotrophin-releasing hormone in timed AI protocols for dairy cows

The effects of addition of gonadotrophin-releasing hormone (GnRH) to a progesterone plus oestradiol-based protocol and timing of insemination in Holstein cows treated for timed AI (TAI) were evaluated. Cows (n = 481) received a progesterone device and 2 mg oestradiol benzoate. After 8 days, the device was removed and 25 mg dinoprost was administered. Cows were allocated to one of three (Study 1; n = 57) or four (Study 2; n = 424) groups, accordingly to ovulation inducer alone (Study 1; oestradiol cypionate (EC), GnRH or both) or ovulation inducer (EC alone or combined with GnRH) and timing of insemination (48 or 54 h after device removal; Study 2). In Study 1, the diameter of the ovulatory follicle was greater for GnRH than EC. Oestrus and ovulation rates were similar regardless of ovulatory stimuli. However, time to ovulation was delayed when GnRH only was used. In Study 2, cows treated with GnRH or not had similar pregnancy per AI (P/AI) 30 days (41.5% vs 37.3%; P = 0.28) and 60 days (35.9% vs 33.0%; P = 0.61) after TAI. TAI 48 and 54 h after device removal resulted similar P/AI at 30 days (40.3% vs 38.5%; P = 0.63) and 60 days (33.8% vs 35.1%; P = 0.72). Thus, adding GnRH at TAI does not improve pregnancy rates in dairy cows receiving EC. The flexibility of time to insemination enables TAI of a large number of cows using the same protocol and splitting the time of AI.

Sperm Binding to Oviduct Epithelial Cells Enhances TGFB1 and IL10 Expressions in Epithelial Cells as Well as Neutrophils In Vitro: Prostaglandin E2 As a Main Regulator of Anti-Inflammatory Response in the Bovine Oviduct

Sperm are allogenic to the female genital tract; however, oviducts provide optimal conditions for survival and capacitation of these non-self cells until fertilization. Recently, we showed that oviduct-conditioned media and prostaglandin E₂ (PGE₂) suppress sperm phagocytosis by polymorphonuclear neutrophils (PMNs) under physiological conditions. We hypothesized that sperm binding to bovine oviduct epithelial cells (BOECs) could change the local innate immunity via PGE₂. As the first step to obtain basic information, sub-confluent BOEC monolayers were co-cultured with swim-up sperm for 2 h. BOECs with viable bound sperm were cultured for an additional 3, 6, 12, or 24 h. Then, we confirmed the impact of the sperm-BOEC binding on both BOECs and PMN gene expression. Immunohistochemistry revealed that BOECs strongly express TGFB1 and IL10 in the oviduct. Sperm binding to BOECs in culture induced the anti-inflammatory cytokines (TGFB1 and IL10) and PGE₂ production by BOECs. Exogenous PGE₂in vitro suppressed pro-inflammatory cytokine expression (TNF and IL1B) in BOECs. Moreover, pre-exposure of PMNs to BOEC-conditioned media suppressed the TNF expression, but the BOEC media co-cultured with sperm stimulated PMNs to express TGFB1 and IL10, with increasing PGE₂ secretion. Of note, exogenous PGE₂ led PMNs in vitro to decrease their TNF expression and increase anti-inflammatory cytokines expression. Our findings strongly suggest that BOECs provide an anti-inflammatory environment under physiological conditions and the sperm-BOEC binding further strengthens this milieu thus suppresses PMNs in the bovine oviduct. PGE₂ is likely to drive this stable anti-inflammatory environment in the oviduct.

Local immune system in oviduct physiology and pathophysiology: attack or tolerance?

The local immune system in the oviduct has a unique ability to deal with pathogens, allogeneic spermatozoa, and the semi-allogeneic embryo. To achieve this, it seems likely that the oviduct possesses an efficient and strictly controlled immune system that maintains optimal conditions for fertilization and early embryo development. The presence of a proper sperm and/or embryo-oviduct interaction begs the question of whether the local immune system in the oviduct exerts beneficial or deleterious effects on sperm and early embryo; support or attack?. A series of studies has revealed that bovine oviduct epithelial cells (BOECs) are influenced by preovulatory levels of Estradiol-17β, progesterone, and LH to maintain an immunologic homeostasis in bovine oviduct, via inhibition of proinflammatory responses that are detrimental to allogenic sperm. Under pathologic conditions, the mucosal immune system initiates the inflammatory response to the infection; the bacterial lipopolysaccharide (LPS) at low concentrations induces a proinflammatory response with increased expression of TLR-4, PTGS2, IL-1β, NFκB1, and TNFα, resulting in tissue damage. At higher concentrations, however, LPS induces a set of anti-inflammatory genes (TLR-2, IL-4, IL-10, and PTGES) that may initiate a tissue repair. This response of BOECs is accompanied by the secretion of acute phase protein, suggesting that BOECs react to LPS with a typical acute proinflammatory response. Under physiological conditions, polymorphonuclear neutrophils (PMN) are existent in the oviductal fluid during preovulatory period in the bovine. Interestingly, the bovine oviduct downregulates sperm phagocytosis by PMN via prostaglandin E2 (PGE2) action. In addition, the angiotensin-endothelin-PGE2 system controlling oviduct contraction may fine-tune the PMN phagocytic behavior to sperm in the oviduct. Importantly, a physiological range of PGE2 supplies anti-inflammatory balance in BOEC. Our recent results show that the sperm binding to BOECs further shift the local immunity toward anti-inflammatory conditions with upregulation of IL-10, TGFβ, and PGE2. In addition, this local environment leads PMN to express anti-inflammatory cytokines. In conclusion, the oviduct displays mucosal immunity that maintains an anti-inflammatory environment under physiological conditions that supports the sperm. Under pathologic condition, however, the oviduct supplies the innate immunity that may attack the sperm. Moreover, the oviduct-sperm interaction further suppresses the innate immune cells and strengthens the anti-inflammatory balance in the oviduct. Therefore, the oviduct immunity ensures sperm viability before fertilization.

Characterization of plasma membrane associated type II α-D-mannosidase and β-N-acetylglucosaminidase of Aquarius remigis sperm

For successful fertilization to occur, molecules on the surface of male and female gametes must recognize each other in a complementary manner. In some organisms, sperm possess a glycosidase on the plasma membrane overlying the head while eggs have glycoproteins that are recognized by those glycosidases resulting in sperm-egg recognition. In this study, two glycosidases, mannosidase and β-N-acetylglucosaminidase, were identified and biochemically characterized in Aquarius remigis sperm. The mannosidase had a Km of 2.36 ± 0.19 mM, a Vmax of 27.49 ± 0.88 pmol/min and a Hill coefficient of 0.94 ± 0.18 at its optimal pH of 7.0. The mannosidase was extracted most efficiently with CHAPSO but was also efficiently extracted with sodium chloride. Mannosidase activity was effectively inhibited by swainsonine, but not by kifunesine, and was significantly reduced in the presence of Mn(2+) and Mg(2+), but not Zn(2+). N-acetylglucosaminidase had a Km of 0.093 ± 0.01 mM, a Vmax of 153.80 ± 2.97 pmol/min and a Hill coefficient of 0.96 ± 0.63 at its optimal pH of 7.0. N-acetylglucosaminidase was extracted most efficiently with potassium iodide but was also efficiently extracted with Triton X-100 and Zn(2+), but not Ca(2+), Co(2+), Mn(2+) or Mg(2+), significantly inhibited its activity. Taken together, these results indicate that the A. remigis sperm surface contains at least two glycosidases that may recognize complementary glycoconjugates on the surface of water strider eggs.

Expression and detection of estrus in dairy cows: the role of new technologies

Despite the widespread adoption of hormonal synchronization protocols that allow for timed artificial insemination (AI), detection of estrus plays an important role in the reproductive management program on most dairies in the United States. Increased physical activity is a secondary sign of estrus in dairy cattle, and a new generation of electronic systems that continuously monitor physical activity to predict timing of AI have been developed and marketed to the dairy industry. A variety of management and physiologic challenges inhibit detection of behavioral estrus on farms, but the prevalence of anouvular cows near the end of the voluntary waiting period is particularly problematic. Only 70% of lactating Holstein cows were detected in estrus when using an activity monitoring system, with the remaining 20% of cows classified as anovular and 10% ovulating without showing signs of activity. Mean time of AI in relation to ovulation based on the activity monitoring system was acceptable for most of the cows with increased activity, however, variability in the duration of estrus and timing of AI in relation to ovulation could result in poor pregnancy outcomes in some cows. Use of a Presynch-Ovsynch protocol for submission of cows for first AI has been widely adopted by dairies in the United States, and a combined approach in which AI based on activity is followed by submission of cows not detected with activity to timed AI after synchronization of ovulation may be an effective strategy for submission of cows to first AI. Based on a field trial on a large commercial dairy in the United States, the activity monitoring system detected 70% of cows with increased activity after the second PGF2α injection of a Presynch-Ovsynch protocol, however, cows inseminated to increased activity had fewer pregnancies per AI (P/AI) compared with cows with increased activity after the second PGF2α injection that received timed AI after completing the Presynch-Ovsynch protocol. Based on an economic model comparing reproductive management programs with varying levels of AI to estrus v. timed AI, the rate of estrus detection and the P/AI to inseminations based on AI to detected estrus v. timed AI affected the decision to inseminate based on activity v. timed AI. In conclusion, an activity monitoring system detected increased activity in about 70% of lactating Holstein cows on a large commercial dairy in the United States, however, synchronization of ovulation and timed AI was beneficial to inseminate cows not detected with increased activity by the activity monitoring system.

Assessment of an accelerometer system for detection of estrus and treatment with gonadotropin-releasing hormone at the time of insemination in lactating dairy cows

Two experiments were conducted to evaluate an accelerometer system (Heatime; SCR Engineers Ltd., Netanya, Israel) to manage reproduction in lactating dairy cows. In experiment 1, lactating Holstein cows (n=112) were fitted with an accelerometer system and were treated with GnRH followed 7d later by PGF(2α) to synchronize estrus. A total of 89 cows that had a follicle >10mm in diameter and a functional corpus luteum at the PGF(2α) injection that regressed by 48 h after induction of luteolysis were included in the analysis. Overall, 71% of cows were detected in estrus by the accelerometer system and 95% of cows showing estrus ovulated within 7d after induction of luteolysis. Of the cows not detected in estrus by the accelerometer system, 35% ovulated within 7d after induction of luteolysis. Duration of estrus activity (mean ± SD) was 16.1±4.7 h and was neither affected by parity nor milk production. Intervals (means ± SD) from induction of luteolysis, onset of activity, peak raw activity, and peak weighted activity to ovulation was 82.2±9.5, 28.7±8.1, 20.4±7.8, and 16.4±7.4 h, respectively, and the interval from AI to ovulation was 7.9±8.7 h, but ranged from -12 to 26 h. In experiment 2, cows were assigned randomly to receive an intramuscular injection of GnRH at artificial insemination (AI) after detection of estrus by the accelerometer system or receive no treatment (control). Nine hundred seventy-nine AI services from 461 cows were analyzed. Treatment with GnRH at AI did not affect fertility at 35 or 65 d after AI, and no interaction was detected between treatment and season or treatment and AI number. Overall, two-thirds of the cows that were considered properly synchronized were inseminated based on the accelerometer system and ovulated after AI. The remaining cows either were not inseminated because they were not detected in estrus or would not have had a chance to conceive to AI because they failed to ovulate after estrus. Furthermore, mean time of AI in relation to ovulation determined by the accelerometer system was acceptable for most of the cows that displayed estrus; however, variability in the duration of estrus and timing of AI in relation to ovulation could lead to poor fertility in some cows. For lactating dairy cows detected in estrus by the accelerometer system, treatment with GnRH at the time of AI without reference to the onset of estrus did not increase fertility.

Bovine oviductal epithelial cells: their cell culture and applications in studies for reproductive biology

Epithelial cells of the mammalian oviduct play an important role in reproductive and developmental events that occur there. Oviductal epithelial cells from several mammalian species can be isolated and cultured in serum or serum-free medium in vitro and cell culture of bovine oviductal epithelial cells (BOEC) has been described by many investigators. Cultured BOEC show a wide variety of secretory activities and these secretory factors may influence early embryonic development or sperm function. Monolayer cultures of BOEC have been widely used for in vitro co-culture of bovine preimplantation embryos. The use of BOEC co-culture systems has improved embryonic development in nearly all the studies conducted. In addition, interaction of bovine spermatozoa with BOEC, in a similar manner to that observed for spermatozoa in vivo, induced specific changes in sperm capacitation and consequently improved the fertilizing capacity of bovine spermatozoa in vitro. Thus co-culture systems with BOEC may not only offer an excellent model for studying the mechanisms of capacitation and acrosome reaction of bovine spermatozoa but also provide a useful tool for the improvement of embryo development in vitro.

Distribution and viability of spermatozoa in the canine female genital tract during post-ovulatory oocyte maturation

BACKGROUND

Unlike other domestic mammals, in which metaphase-II oocytes are ovulated, canine ovulation is characterized by the release of primary oocytes, which may take 12 to up to 36 hours. Further 60 hours are needed for maturation to secondary oocytes which then remain fertile for about 48 hours. Oestrus takes 7 to 10 days on average and may start as early as a week before ovulation. This together with the prolonged process of post-ovulatory oocyte maturation requires an according longevity of spermatozoa in the female genital tract in order to provide a population of fertile sperm when oocytes have matured to fertilizability. Therefore the distribution and viability of spermatozoa in the bitch genital tract was examined during post-ovulatory oocyte maturation.

METHODS

Thirteen beagle bitches were inseminated on the day of sonographically verified ovulation with pooled semen of two beagle dogs containing one billion progressively motile spermatozoa. Ovariohysterectomy was performed two days later (group 1, n = 6) and four days later (group 2, n = 7). The oviduct and uterine horn of one side were flushed separately and the flushing's were checked for the presence of gametes. The oviducts including the utero-tubal junction and the uterine horns, both the flushed and unflushed, were histologically examined for sperm distribution.

RESULTS

The total number of spermatozoa recovered by flushing was low and evaluation of viability was limited. Prophase-I oocytes were collected from oviduct flushing in group 1, whereas unfertilized metaphase-II oocytes were detected in group 2. From day 2 to day 4 after ovulation a significant decrease in the percentage of glands containing sperm (P<0.05) and a marked reduction of the mean sperm number in uterine horn glands were observed. A concomitant diminution of spermatozoa was indicated in the utero-tubal junction accompanied by a slight increase in sperm numbers in the mid oviduct.

CONCLUSIONS

Oocyte maturation to metaphase-II stage is accompanied by a continuous sperm detachment and elimination in the uterine horns. Entrance of spermatozoa into the caudal oviduct seems to be steadily controlled by the utero-tubal junction thus providing a selected sperm population to be shifted towards the site of fertilization when oocyte maturation is completed.

Oviductal, endometrial and embryonic gene expression patterns as molecular clues for pregnancy establishment

In higher animals, the beginning of new life and transfer of genetic material to the next generation occurs in the oviduct when two distinct gametes cells unite resulting in the formation of a zygote. The zygote then undergoes serial developmental processes in the oviduct and enters into the uterus where it faces challenges and scrutiny from the endometrial ecosystem. Thus, embryos that are able to establish an appropriate embryo-maternal dialogue are capable of developing to term whereas the incompetent ones can perish any time during the gestation period. Although several lines of evidences indicated that pregnancy loss is a multi-factorial phenomenon, the biochemical composition of the embryo and maternal environment are the main players to determine pregnancy outcome. Indeed, expression patterns of the genes are the driving forces that induce biochemical composition changes in embryo, oviduct and uterine environment. Thus, examining the molecular signals that are associated with oviductal or endometrial receptivity and embryo implantation is essential for establishing strategies to improve pregnancy success. Therefore, this review focuses on the contribution of oviduct and its transcriptome profile on early stage embryo development and the impact of endometrium and its transcriptome changes on peri and post embryo implantation. In addition, this paper integrates established facts about hormonal and molecular signatures associated with endometrial receptivity. Finally, the blastocyst and pre-conception endometrial gene expression profiles have been discussed in relation to the pregnancy outcome to highlight the potentials of blastocyst and pre-transfer endometrial transcriptome profile approach for selecting appropriate recipient and developmentally competent embryo.

Artificial insemination at 56 h after intravaginal progesterone device removal improved AI pregnancy rate in beef heifers synchronized with five-day CO-Synch + controlled internal drug release (CIDR) protocol

The objective was to determine whether timed artificial insemination (TAI) 56 h after removal of a Controlled Internal Drug Release (CIDR, 1.38 g of progesterone) insert would improve AI pregnancy rate in beef heifers compared to TAI 72 h after CIDR insert removal in a 5-days CO-Synch + CIDR protocol. Angus cross beef heifers (n = 1098) at nine locations [WA (5 locations; n = 634), ID (2 locations; n = 211), VA (one location; n = 193) and WY (one location; n = 60)] were included in this study. All heifers were given a body condition score (BCS; 1-emaciated; 9-obese), and received a CIDR insert and 100 μg of gonadorelin hydrochloride (GnRH) on Day 0. The CIDR insert was removed and two doses of 25 mg of dinoprost (PGF(2α)) were given, first dose at CIDR insert removal and second dose 6 h later, on Day 5. A subset of heifers (n = 629) received an estrus detector aid at CIDR removal. After CIDR removal, heifers were observed thrice daily for estrus and estrus detector aid status until they were inseminated. Within farm, heifers were randomly allocated to two groups and were inseminated either at 56 h (n = 554) or at 72 h (n = 544) after CIDR removal. All heifers were given 100 μg of GnRH at AI. Insemination 56 h after CIDR insert removal improved AI pregnancy rate compared to insemination 72 h (66.2 vs. 55.9%; P < 0.001; 1 - β = 0.94). Locations, BCS categories (≤ 6 vs. > 6) and location by treatment and BCS by treatment interactions did not influence AI pregnancy rate (P > 0.1). The AI pregnancy rates for heifers with BCS ≤ 6 and > 6 were 61.8 and 60.1%, respectively (P > 0.1). The AI pregnancy rates among locations varied from 54.9 to 69.2% (P > 0.1). The AI pregnancy rate for heifers observed in estrus at or before AI was not different compared to heifers not observed in estrus [(65.4% (302/462) vs. 52.7% (88/167); P > 0.05)]. In conclusion, heifers inseminated 56 h after CIDR insert removal in a 5-days CO-Synch + CIDR protocol had, on average, 10.3% higher AI pregnancy rate compared to heifers inseminated 72 h after CIDR insert removal.

Timing of insemination and fertility in dairy and beef cattle receiving timed artificial insemination using sex-sorted sperm

The objective was to evaluate the effects of timing of insemination and type of semen in cattle subjected to timed artificial insemination (TAI). In Experiment 1, 420 cyclic Jersey heifers were bred at either 54 or 60 h after P4-device removal, using either sex-sorted (2.1 × 10(6) sperm/straw) or non-sorted sperm (20 × 10(6) sperm/straw) from three sires (2 × 2 factorial design). There was an interaction (P = 0.06) between time of AI and type of semen on pregnancy per AI (P/AI, at 30 to 42 d after TAI); it was greater when sex-sorted sperm (P < 0.01) was used at 60 h (31.4%; 32/102) than at 54 h (16.2%; 17/105). In contrast, altering the timing of AI did not affect conception results with non-sorted sperm (54 h = 50.5%; 51/101 versus 60 h = 51.8%; 58/112; P = 0.95). There was an effect of sire (P < 0.01) on P/AI, but no interaction between sire and time of AI (P = 0.88). In Experiment 2, 389 suckled Bos indicus beef cows were enrolled in the same treatment groups used in Experiment 1. Sex-sorted sperm resulted in lower P/AI (41.8%; 82/196; P = 0.05) than non-sorted sperm (51.8%; 100/193). In addition, there was a tendency for greater P/AI (P = 0.11) when TAI was performed 60 h (50.8%; 99/195) versus 54 h (42.8%; 83/194) after removing the progestin implant. In Experiment 3, 339 suckled B. indicus cows were randomly assigned to receive TAI with sex-sorted sperm at 36, 48, or 60 h after P4 device removal. Ultrasonographic examinations were performed twice daily in all cows to confirm ovulation. On average, ovulation occurred 71.8 ± 7.8 h after P4 removal, and greater P/AI was achieved when insemination was performed closer to ovulation. The P/AI was greatest (37.9%) for TAI performed between 0 and 12 h before ovulation, whereas P/AI was significantly less for TAI performed between 12.1 and 24 h (19.4%) or >24 h (5.8%) before ovulation. In conclusion, sex-sorted sperm resulted in a lesser P/AI than non-sorted sperm following TAI. However, improvements in P/AI with delayed time of AI were possible (Experiments 1 and 3), and seemed achievable when breeding at 60 h following progestin implant removal, compared to the standard 54 h normally used in TAI protocols.

Is there a role for endocannabinoids in sperm–oviduct interaction?

The endocannabinoid system (ECS) has been found in reproductive cells and tissues in several mammals. Spermatozoa are able to respond to anandamide, and the oviduct is able to synthesize and modulate the concentration of this endocannabinoid along the isthmic and ampullary regions. The main aim of this study was to understand whether the ECS has a role during sperm storage and release within the oviduct in cattle. Data showed that 1) the endocannabinoid receptors 1 and 2 (CB1 and CB2) are present in bovine spermatozoa both in the initial ejaculate and in spermatozoa bound to the oviduct in vitro; 2) CB1 receptor is still detectable in spermatozoa released from the oviduct through penicillamine but not in those released through heparin; 3) arachidonylethanolamide (AEA) does not affect sperm viability, whereas it depresses sperm progressive motility and kinetic values; 4) sperm–oviduct binding and release in vitro are not influenced by AEA; 5) AEA depresses sperm–zona pellucida (ZP) binding; 6) binding of heparin-capacitated spermatozoa to the ZP is not affected by AEA; 7) N-acylphosphatidylethanolamine-selective phospholipase D, the main enzyme involved in anandamide synthesis, is expressed in oviductal epithelial cells. In conclusion, secretion of AEA from epithelial cells might contribute to the oviduct sperm-reservoir function, prolonging the sperm fertile life through the depression of motility and capacitation. Capacitation signals, such as heparin, that promote sperm release, might remodel the sperm surface and cause a loss of the sperm sensitivity to AEA.

When is a cow in estrus? Clinical and practical aspects

Good detection of estrus is critically important in dairy husbandry. Incorrect detection of estrus is related to loss of profit due to extended calving intervals, milk loss, veterinary costs, etc. Detection of estrus remains a major problem despites enormous progress in the knowledge of reproductive physiology of the cow and in development of estrus detection aids. To achieve good estrus detection, many factors have to be taken into account. On one hand a cow has to express estrus and on the other hand the farmer has to detect it. Combined action of several hormones causes physiological changes that lead to ovulation and an environment in the uterus that allows sperm to fertilize the egg. Besides these internal actions, a number of external changes can be observed. When using visual observations, time of the day and time spend on observation have a great impact on detection rates. Many devices are available to aid in estrus detection, such as pedometers, mount devices, temperature, and hormone measurements. Expression of estrus can be influenced by many factors. Heritability, number of days postpartum, lactation number, milk production, and health are known to influence estrus expression. Environmental factors like nutrition, season, housing, herd size, etc. also play a role in estrus expression. To evaluate estrus detection, record keeping is very important; a number of formulas can be used to assess detection efficiency. Besides the farmer, the veterinarian and inseminator can play an important role in estrus confirmation and good insemination strategy. In the end, the time of ovulation and the age of the egg at sperm penetration is critical for conception. Therefore, emphasis in research needs to be on the timing of insemination relative to ovulation, and thus on the detection of ovulation.

Altering the time of the second gonadotropin-releasing hormone injection and artificial insemination (AI) during Ovsynch affects pregnancies per AI in lactating dairy cows

Based on previous research, we hypothesized that Cosynch at 72 h [GnRH-7 d-PGF(2alpha)-72 h-GnRH + artificial insemination (AI)] would result in a greater number of pregnancies per AI (P/AI) than Cosynch at 48 h. Further, we hypothesized that P/AI would be improved to a greater extent when GnRH was administered at 56 h after PGF(2alpha) before AI at 72 h due to a more optimal interval between the LH surge and AI. Nine hundred twenty-seven lactating dairy cows (n = 1,507 AI) were blocked by pen, and pens rotated through treatments. All cows received GnRH followed 7 d later by PGF(2alpha) and then received one of the following: 1) GnRH + timed AI 48 h after PGF(2alpha) (Cosynch-48); 2) GnRH 56 h after PGF(2alpha) + timed AI 72 h after PGF(2alpha) (Ovsynch-56); or 3) GnRH + timed AI 72 h after PGF(2alpha) (Cosynch-72). Pregnancy diagnoses were performed by ultrasound at 31 to 33 d post-AI and again at 52 to 54 d post-AI. Overall P/AI were similar for the Cosynch-48 (29.2%) and Cosynch-72 (25.4%) groups. The Ovsynch-56 group had a greater P/AI (38.6%) than Cosynch-48 or Cosynch-72. Presynchronized first-service animals had greater P/AI than cows at later services in Cosynch-48 (36.2 vs. 23.0%) and Ovsynch-56 (44.8 vs. 32.7%) but not in Cosynch-72 (24.6 vs. 26.2%). Similarly, primiparous cows had greater P/AI than multiparous cows in Cosynch-48 (34.1 vs. 22.9%) and Ovsynch-56 (41.3 vs. 32.6%), but not Cosynch-72 (29.8 vs. 25.3%). In conclusion, we found no advantage to Cosynch at 72 h vs. 48 h. In contrast, we found a clear advantage to treating with GnRH at 56 h, 16 h before a 72-h AI, probably because of more-optimal timing of AI before ovulation.

Sperm release from oviduct epithelial binding is controlled hormonally by peri-ovulatory graafian follicles

To avoid inappropriate conclusions being drawn from the extensive use of in vitro preparations of sperm-oviduct epithelial binding, it is recalled that events in the genital tract of mammals are regulated by the gonads, primarily by their changing secretion of steroid hormones. Key observations from in vivo models are used to emphasise the dynamic interactions between viable sperm cells and the caudal (distal) portion of the oviduct isthmus, the site of the functional sperm reservoir. These include (1) pre-ovulatory arrest and epithelial binding of intact sperm cells and thereby suppression of completion of capacitation, (2) peri-ovulatory activation and release from binding of discrete sub-populations of competent spermatozoa, and (3) post-ovulatory liberation of large numbers of spermatozoa. These observations underline the influence of endocrine regulation of sperm binding and release by peri-ovulatory Graafian follicles, a point brought out by the enhanced sperm release prompted by diverse treatments with solutions of progesterone. In the light of this evidence, the suitability of in vitro preparations for clarifying physiological events should be questioned, especially if myosalpingeal catecholamines diffusing out of the autonomic nervous system contribute to sperm activation and/or release. None of this is to infer that sperm cells themselves are without influence on their epithelial binding reaction(s). Nor is it to suggest that in vitro models of sperm-oviduct binding are without relevance to the development of sperm evaluation technologies. However, pre-ovulatory sperm-epithelial binding and a regulated peri-ovulatory release should be seen as vital tactics in the overall strategy of achieving successful monospermic fertilisation.

Sperm binding properties and secretory activity of the bovine oviduct immediately before and after ovulation

The possibility that differences in hormonal regimes between the two oviducts in the cow around ovulation affects secretory activity of the oviduct epithelial cells and/or sperm-oviduct binding was studied. Oviducts were collected immediately after slaughter at 6 hr before to 5 hr after timed ovulation of 14 normally cyclic cows that had been inseminated (n = 6) or not (n = 8) and material obtained from the same cows was processed in three ways. First, in vivo, after artificial insemination of the cows, low numbers of sperm cells (approx. 15 per oviduct) were found within the entire oviducts as observed by scanning electron microscopy (SEM). Almost all sperm were located in the isthmus and then only on ciliated cells and showed without exception fully matured, intact morphology. Secretory activity of noninseminated oviduct epithelia was induced after ovulation which was most predominant in the pockets of the ipsi-lateral ampulla compared to the contra-lateral ampulla (P < 0.01). Second, ex vivo, explants dissected from oviducts of the noniseminated cows were incubated with sperm. In all cases, the sperm bound to the explants in a similar pattern as observed in vivo and this binding was strictly fucose-dependent. The main difference with in vivo experiments was the high numbers of sperm bound at any site of the oviduct ( approximately 3,000 cells per mm(2)) indicating the high sperm binding capacity of the oviduct epithelia. Ovulation induced a striking drop in sperm binding capacity in the oviducts and was most pronounced in the isthmus ( approximately 1,300 cells per mm(2); P < 0.001) and to a lesser extent in the ampulla ( approximately 2,000 cells per mm(2), P < 0.01). Third, in vitro, pieces of tissue dissected from oviducts of the noninseminated cows were cultured to mono-layers. Culturing epithelial cells resulted in loss of their normal morphological appearance. In all cases, the sperm binding capacity in monolayers was very low (<50 cells per mm(2)) when compared to corresponding explants (P < 0.0001). Sperm binding to monolayers originating from the isthmus (<25 cells per mm(2)) was lower than in those from the ampulla (40-50 cells per mm(2); P < 0.01) and remained similar after ovulation. In all three approaches, no significant differences were found in sperm-oviduct binding characteristics and sperm-distribution in the ipsi- versus contra-lateral oviducts. This indicates, that systemic endocrine changes around ovulation rather than specific oviduct changes at the ipsi-lateral oviduct induce secretion in oviduct epithelial cells, and thus induce sperm release.

Experimental Evidence for the Influence of Cumulus-Oocyte-Complexes on Sperm Release from the Porcine Oviductal Sperm Reservoir

In the pig, a temporal relationship is suggested between sperm release from the sperm reservoir (SR) and ovulation, but the mechanism(s) is still under discussion. In two experiments, the influence of transferred ova on the release of SR-spermatozoa at ovulation and the effect of supplementation with non-sulfated glycosaminoglycan hyaluronan (HA) on embryo development and the number of accessory spermatozoa, respectively, were examined. PMSG/hCG primed ovectomized gilts that had previously received endoscopic low-dose insemination into the cranial uterine horn were used as an experimental model. After salpingectomy, tubal segments (ampulla, cranial, and caudal isthmus) were flushed and sperm numbers or respective accessory spermatozoa were counted. In Experiment 1, the distribution of the sperm population was altered in the presence of cumulus-oocyte-complexes (COCs). A higher proportion of spermatozoa was found after transfer of COCs into one oviduct in the ampulla and cranial isthmus segments compared with the controls (17.5 vs. 4.9%, p<0.05). In Experiment 2, the quality of the transferred ova and treatment influenced the presence of accessory spermatozoa. Transfer of COCs together with HA increased (p<0.05) the number of accessory spermatozoa compared with the other treatment groups and was similar to those in the "undisturbed" controls. No modifications were obtained regarding mean blastomere numbers (2.6 +/- 0.2 to 3.1 +/- 0.2). In summary, this study was demonstrated that cumulus-oocyte-complexes may be involved in triggering sperm release from the pig oviductal SR and that HA might be related to sperm release.

Intracellular calcium and protein tyrosine phosphorylation during the release of bovine sperm adhering to the fallopian tube epithelium in vitro

In mammals, sperm adhesion to the epithelial cells lining the oviductal isthmus plays a key role in the maintenance of motility and in the selection of superior quality subpopulations. In the bovine species, heparin and other sulfated glycoconjugates powerfully induce the synchronous release of sperm adhering to tubal epitheliumin vitroand may represent the signal which triggers release at ovulationin vivo. Sperm detachment may be due either to surface remodeling or to hyperactivation brought about by capacitation. In this paper, the dynamics of intracellular free Ca2+concentration ([Ca2+]i) and protein tyrosine phosphorylation in sperm during and after heparin-induced release fromin vitrocultured oviductal monolayers were assessed to determine whether this event is due to capacitation. Moreover, Ca2+-ionophore A23187, thapsigargin, thimerosal and caffeine were used to determine whether [Ca2+]iincrease and/or hyperactivation can induce sperm release. Results showed that: 1. heparin-released sperm have significantly higher [Ca2+]ithan adhering sperm; 2. heparin induces a [Ca2+]ielevation in the sperm head followed by detachment from the monolayers; 3. external Ca2+is not required for heparin-induced release; 4. [Ca2+]iincrease and/or hyperactivation are unable to release sperm; and 5. heparin-released sperm have an increased level of tyrosine phosphorylated proteins compared with adhering sperm. In conclusion, although heparin is considered a long-lasting capacitation agent, it quickly modulates the capacitation of bovine sperm adhering to the fallopian epithelium, probably leading to surface remodeling and therefore to the release of sperm selected and stored within the oviduct through adhesion.

Distribution of spermatozoa in the female reproductive tract of the domestic cat in relation to ovulation induced by natural mating

The purposes of this study were to demonstrate the localization of spermatozoa in the reproductive tract of female domestic cats before (30 min and 3 h after mating) and after ovulation (48 and 96 h after mating), and to evaluate the efficiency of two techniques for studying sperm distribution. Estrus was induced in twenty-four female cats using 100 IU eCG and the females were divided into four groups with six females per group. The same male cat was used for mating with all the females. One group of six females was mated once; the others were mated four times in 1 h. Ovariohysterectomy was performed at 30 min, 3 h, 48 h, and 96 h after mating and the excised reproductive tracts were divided into seven segments on each side: infundibulum, ampulla, isthmus, uterotubal junction (UTJ), cranial and caudal uterine horn, and uterine body. The vagina and the lumina of the segments from one side were flushed with 0.5 ml PBS. The flushed and the non-flushed segments from the contralateral side were then fixed in 3% neutral buffered formalin and processed for routine histology. The numbers of spermatozoa in the flushings and in 40 histological sections from each segment were counted. Before ovulation, the majority of spermatozoa was detected in the vagina and the uterine segments, whereas after ovulation, significantly higher numbers of spermatozoa were present in the uterine tubal segments. The decreasing gradient in sperm numbers at 30 min and 3 h after mating between the vagina, the uterine segments, including the UTJ, and the uterine tubal segments indicated that the cervix and the UTJ served as barriers for sperm transport in the cat. The UTJ and the uterine crypts acted as sperm reservoirs before ovulation whereas the isthmus was a sperm reservoir around the time of ovulation. There was no difference in sperm numbers in the tissue sections between flushed and non-flushed segments, implying that the flushing technique only recovered some intraluminal spermatozoa while most of the spermatozoa remained in the epithelial crypts. This was further supported by the finding that significantly higher numbers of spermatozoa were recovered in the flushings at 30 min and 3 h after mating, when more spermatozoa were free in the lumina, than at 48 and 96 h after mating, when the majority of the spermatozoa were entrapped in the uterine epithelial crypts.

Capacitation of mammalian spermatozoa in vivo, with a specific focus on events in the fallopian tubes

This essay argues strongly that for those sperm cells involved in fertilisation, the process of capacitation represents an active and specific coordination within succeeding regions of the female tract and one whose completion is synchronised with the events of ovulation. Observations on the time-course of capacitation when spermatozoa are first exposed to the uterus and then progress to the Fallopian tubes indicate a synergistic influence of these adjoining portions of the female tract on the rate of capacitation. Three concepts on the control of capacitation are introduced to emphasise the importance of integration in vivo, namely that (1) completion of capacitation is a peri-ovulatory event, (2) suppression of completion of capacitation is an essential storage strategy during a long pre-ovulatory interval, and (3) the process of capacitation comes under the influence of local and systemic ovarian control mechanisms, especially the secretion of progesterone from Graafian follicles soon to ovulate. The last would act to coordinate the final maturation and meeting of male and female gametes. Despite the preceding points, the requirement for such integrated in vivo programming of sperm cell maturation can clearly be overridden in systems of culture. The most reasonable interpretation here would be that a microdrop of culture medium containing eggs, follicular cells and components of follicular fluid would to a considerable extent represent a post-ovulatory environment. Within such a preparation, there would be leaching of the sperm surface among the relatively vast and heterogeneous population of cells, and a proportion of spermatozoa could then respond to 'post-ovulatory signals', not least to molecular influences of the zona pellucida and vitelline products for completion of capacitation. Nonetheless, a physiologically meaningful interpretation of capacitation calls for a stepwise analysis of the dynamic interactions between sperm cell and female tract at successive stages between the uterus and ampullary-isthmic junction.

Optimization of in vitro bovine embryo production: effect of duration of maturation, length of gamete co-incubation, sperm concentration and sire

The aim of these experiments was to investigate the effect of duration of IVM, duration of gamete co-incubation, and of sperm dose on the development of bovine embryos in vitro. In addition, the speed of sperm penetration of six bulls of known differing in vivo and in vitro fertility was examined. In Experiment 1, following IVM for 16, 20, 24, 28 or 32 h, cumulus oocyte complexes (COCs) were inseminated with 1 x 10(6) spermatozoa/ml. After 24 h co-incubation, presumptive zygotes were denuded and placed in droplets of synthetic oviduct fluid (SOF). In Experiment 2, following IVM and IVF, presumptive zygotes were removed from fertilization wells at 1, 5, 10, 15 or 20 h post insemination and placed in culture as described above. In Experiment 3, following IVM, COCs were inseminated with sperm doses ranging from 0.01 x 10(6) to 1 x 10(6) spermatozoa/ml. Following co-incubation for 24 h, presumptive zygotes were placed in culture as described above. In Experiment 4, following IVM, oocytes were inseminated with sperm from six bulls of known differing field fertility. To assess the rate of sperm penetration, oocytes were subsequently fixed every 3 h (up to 18 h) following IVF. Based on the results of Experiment 4, in Experiment 5, following IVM for 12, 18 or 24 h, COCs were inseminated with sperm from two sires with markedly different penetration speeds. After 24 h co-incubation, presumptive zygotes were denuded and placed in culture. The main findings from this study are that (1) the optimal duration of maturation of bovine oocytes in vitro to maximize blastocyst yield is 24 h, (2) sperm-oocyte co-incubation for 10 h is sufficient to ensure maximal blastocyst yields, (3) sperm concentrations of 0.25 x 10(6) and 0.5 x 10(6) spermatozoa/ml yielded significantly more blastocysts than any other concentration within the range of 0.01 x 10(6) 1 x 10(6) spermatozoa/ml, (4) there are marked differences in the kinetics of sperm penetration between sires and this may be a useful predictor of field fertility, and (5) the inferior development associated with slower penetration rates may in part be overcome by carrying out IVF at a time when the actual penetration is most likely to coincide with the completion of maturation.

Effect of time of insemination on number of accessory sperm, fertilization rate, and embryo quality in nonlactating dairy cattle

Two experiments were conducted to determine the effect of insemination time on number of accessory sperm per embryo (ovum), fertilization rate, and embryo quality. Semen was collected from three fertile Holstein bulls and cryopreserved in egg yolk-citrate-glycerol. In experiment 1, cows were continuously monitored for behavioral estrus by the HeatWatch estrous detection system and were artificially inseminated (AI) with one 0.5-ml straw (25 x 10(6) sperm) at the onset of estrus (AI 0 h), 12 h after onset (AI 12 h), or received natural service at 0 h (Nat 0 h) from one of three bulls. From 150 inseminations, 115 embryos and ova (AI 0 h: n = 39; AI 12 h: n = 39; Nat 0 h: n = 37) were recovered 6 or 7 d after insemination. Fertilization rates differed between treatments (AI 0 h: 67%; AI 12 h: 79%; Nat 0 h: 98%). Median accessory sperm per embryo (ovum) also differed (AI 0 h: 1; AI 12 h: 10; and Nat 0 h: 27) and paralleled the fertilization rate. Embryo quality was not affected by insemination time or natural service. In experiment 2, cows received AI at 0, 12, or 24 h (AI 24 h) after the onset of estrus as determined by HeatWatch. From 154 inseminations, 117 embryos and ova (AI 0 h: n = 39; AI 12 h: n = 39; AI 24 h: n = 39) were recovered 6 or 7 d after insemination. Fertilization rates did not differ in experiment 2 (AI 0 h: 66%; AI 12 h: 74%; AI 24 h: 82%); however, a trend toward a higher fertilization rate accompanied AI 24 h. Median accessory sperm values increased from AI 0 h (1) to AI 24 h (4). Embryo quality declined with AI at increasing intervals after onset of estrus, as percentages of excellent and good, fair and poor, and degenerate embryos were as follows: 77, 15, 8; 52, 38, 10; and 47, 19, 34 for the 0-, 12-, and 24-h inseminations, respectively. Results indicate AI 12 h after the onset of estrus provides a compromise between potential fertilization failure (AI 0 h) and embryo failure (AI 24 h), despite increased accessory sperm per embryo (ovum) after AI 24 h. Artificial insemination 12 h after onset of estrus should optimize fertility of dairy cattle through an acceptable fertilization rate, number of accessory sperm per embryo, and desirable embryo quality.

Sulfated glycoconjugates are powerful modulators of bovine sperm adhesion and release from the oviductal epithelium in vitro

The mechanisms of sperm adhesion and release within the mammalian oviduct are still poorly understood. In this in vitro study, a previously developed adhesion assay was used to analyze the effects of heparin, N-desulfated heparin, fucoidan, dextran sulfate, and dextran on bovine sperm-oviductal cell adhesion and release. Results showed that 1) all sulfated glycoconjugates were powerful inhibitors of sperm binding to oviductal monolayers in a dose-dependent manner, whereas N-desulfated heparin and dextran had no effect; 2) sperm pretreatment with heparin and fucoidan markedly inhibited adhesion; 3) treatment of oviductal monolayers with heparinase I, II, or sodium chlorate (an inhibitor of sulfation) had no effect on sperm adhesion; 4) sulfated glycoconjugates were also powerful and quick inducers of sperm release from oviductal monolayers; and 5) addition of sulfated glycoconjugates to the cocultures caused a sudden increase of bound-sperm flagellar beat frequencies, followed by a release of highly motile sperm. In conclusion, these data support the hypothesis that sulfated glycoconjugates may act as signals that induce sperm release and migration from the oviductal reservoir.

Automated electronic systems for the detection of oestrus and timing of AI in cattle

For the majority of dairy herds where artificial insemination (AI) is practiced, the limiting factor toward obtaining efficient reproductive performance is the failure to detect oestrus in a timely and accurate manner. Periodic visual observation has been the dominant method used to identify cows in oestrus. New approaches are being developed to provide automated systems of detection of oestrus using electronic technology. The goal of an oestrus detection program should be to identify oestrus positively and accurately in all cycling animals and consequently to identify animals not cycling. The ultimate goal should be to predict the time of ovulation, thus allowing for insemination that will maximize the opportunity for conception. Unfortunately, most studies designed to evaluate the optimal time of AI generally contained two technical deficiencies: inadequate numbers of cows for valid statistical comparisons and inaccurate knowledge of the onset of oestrus because of low frequency of visual observations and/or efficiency of methods used for the detection of oestrus. Studies using pedometry and a pressure sensing radiotelemetric system will be reviewed as each have independently obtained an optimal time of AI of 5 to 17 h after either the increase in locomotive activity or following the first standing event associated with the onset of oestrus.

In vitro-cultured bovine oviductal cells bind acrosome-intact sperm and retain this ability upon sperm release

The mammalian oviduct plays a key role in sperm storage, capacitation, and selection. Specific oviduct secretions and/or binding to oviductal cells are thought to be responsible for the extension of the fertile life span of sperm. In this in vitro study, a quantitative assay for sperm binding was developed to analyze the mechanisms of sperm-oviductal cell adhesion and release in the bovine species. Distribution and acrosomal status of sperm bound to in vitro-cultured ampullary and isthmic cell monolayers were followed until the time of sperm release by means of fluorescence labeling techniques. In order to understand whether release is due to surface changes of sperm or oviductal cells, double incubation experiments with unlabeled and Hoechst-labeled sperm have been performed. Main findings demonstrate that (1) only acrosome-intact sperm bind specific bovine oviductal epithelial cells; (2) acrosomes of bound sperm are preserved intact over time; and (3) release of unreacted sperm is likely to be due to changes of the sperm surface, probably triggered by capacitation. These findings support the hypothesis that binding to oviductal cells is essential for preserving the sperm fertilization competence during the interval from the onset of estrus to ovulation.

Timing of insemination for dairy cows identified in estrus by a radiotelemetric estrus detection system

The optimal time of artificial insemination (AI) was determined from data for 2661 AI in 17 herds utilizing a radiotelemetric system for estrus detection that has the potential for continuous 24-h surveillance to monitor behavioral events associated with estrus. The system consisted of pressure-sensitive radio frequency transmitters affixed over the sacrum region of cows. The activation of the sensor sent a radiotelemetric signal to a microcomputer via a fixed antenna. Cow identification, date, time, and duration of each standing event were recorded in the software program provided with the system. Each farm selected a 3-h interval to AI for cows that were identified in estrus during the previous 24 h. Pregnancy status was determined from data for return to estrus and palpation of the uterus 35 to 75 d following AI. Standing events during estrus averaged (+/- SD) 8.5 +/- 6.6 per cow, and the number of events per estrus across herds averaged from 6.2 +/- 5.1 to 12.8 +/- 9.9 per cow. The duration of estrus ranged from 5.1 +/- 3.8 to 10.6 +/- 6.8 h across herds; the mean was 7.1 +/- 5.4 h. The interval from the first standing event to AI affected the probability of pregnancy; the highest conception rates for AI occurred between 4 and 12 h after the onset of standing activity. The probability of pregnancy was higher for cows > 100 d in milk, exhibiting > 2 standing events during estrus, and inseminated during March, April or May.

Can spermatozoa with abnormal heads gain access to the ovum in artificially inseminated super- and single-ovulating cattle?

The collective efficiency of barriers in the female tract against spermatozoa with abnormal heads was studied. In Experiment 1, Day 6 ova/embryos were recovered nonsurgically from superovulated (n = 24) and single-ovulating (n = 44) cows following artificial insemination with semen of bulls selected for normal spermatozoal motility (> or = 50%) and high content (> 30%) of spermatozoa with misshapen heads, random nuclear vacuoles or the diadem defect. To assess characteristics of spermatozoa capable of traversing barriers in the female tract, accessory spermatozoa were classified morphologically (x 1250) and compared with those of the inseminate. Superovulated cows proved inadequate for assessment of accessory spermatozoa due to evidence of poor sperm retention in the zona pellucida; thus, only single-ovulating cows were used. Accessory spermatozoa (n = 479) from 31 ova/embryos recovered from 44 cows were more normal in head shape than those in the inseminate (76 vs 62%; P < 0.05). Spermatozoa with normal head shape, but with nuclear vacuoles appeared as accessory spermatozoa at the same frequency as they were found in the inseminate (20 vs 17%, respectively). Only sperm cells with subtly misshapen heads appeared as accessory spermatozoa. In Experiment 2, semen pooled from 4 bulls having large numbers of spermatozoa exhibiting a gradation from severely asymmetrically misshapen heads to subtly misshapen heads was evaluated. Again, the accessory sperm population (960 sperm cells recovered from 64 ova/embryos) was enriched with spermatozoa of normal head shape relative to the inseminate (53 vs 26%, respectively; P < 0.05). Sperm cells with only nuclear vacuoles and those with subtly misshapen heads were not different between the accessory and inseminate populations (11 vs 8%, and 20 vs 25%, respectively). We conclude that morphologically abnormal spermatozoa are excluded from the accessory sperm population based upon severity of head shape distortion.

Factors associated with variation in the superovulatory response of cattle

Kafi, M., McGowan, M.R., 1997. Factors associated with variation in the superovulatory response of cattle. Anim. Reprod. Sci. Variability in the superovulatory response of cattle is still one of the major limiting factors in extensive usage of embryo transfer technology. A variety of approaches including recent attempts to eliminate the suppressive effect of the dominant follicle have been used to reduce the unpredictability of the superovulatory response of cattle. The development of techniques such as transrectal ultrasonography, have enabled a re-evaluation of ovarian dynamics during superovulation of cattle. In addition, advances in reproductive hormone assays have increased knowledge of the mechanisms controlling follicular development, ovulation and corpus luteum function. This review focuses on the current understanding of factors affecting the superovulatory response of cattle. Also, abnormalities of ovulation and endocrine disorders that may occur during superovulation are reviewed.

Oestrous behaviour of Holstein cows during cooler and hotter tropical seasons

Seasonal effects on post-partum ovarian activity, duration and intensity of sexual behaviour were determined for Holstein dairy cattle imported from a temperate climate into a tropical region. Animals were observed continuously during the cooler (temperature-humidity index (THI) < 25) and hotter (THI > 25) seasons for 2 years. They were restricted to a cement footing in the hotter season observation period in Year 1, but had access to both concrete and dirt footing during all other seasons. Sequential milk progesterone profiles provided an indication of when follicular phases occurred, and recorded sexual behaviour was compared with these to determine if oestrous signs accompanied ovulations. Most cows had normal ovarian cycles and ovulated regularly during both seasons, but quiet ovulations occurred with greater frequency during the hotter times of the year (P < 0.05). Demonstrations of sexual behaviour were affected by choice of footing rather than season. The actual time when cows stood passively and allowed herdmates to complete mounting ranged from 5.1 +/- 0.7 to 5.8 +/- 1 h with access to exercise yards and cement or dirt footing, but declined to only 1.3 +/- 1.1 h when animals were confined to cement (P < 0.05). Similarly, the total duration of oestrus and mean number of interactions were significantly (P < 0.05) reduced during the observation period conducted with cows confined to concrete footing. These findings further emphasize that the duration of oestrus in dairy cows in considerably shorter than the commonly quoted 18 h.

In vitro-cultured bovine granulosa and oviductal cells secrete sperm motility-maintaining factor(s)

Since bovine cumulus oophorous and oviductal cell cultures are known to support and maintain frozen-thawed bovine sperm viability and motility for extended time periods, we investigated whether granulosa cell (GC)- and oviductal cell (OC)-conditioned media have similar effects. GC and OC were cultured for 3 days in TCM-199 medium supplemented with 10% fetal calf serum. At that time, the supernatant was discarded from GC and the monolayers were covered with Sp-TALP medium containing 6 mg/ml bovine serum albumin, while the OC were recovered by centrifugation and transferred to culture bottles containing Sp-TALP. Two days later, GC-conditioned and OC-conditioned Sp-TALP were recovered and dialyzed, and their retentates were lyophilized. Bovine follicular fluid (BFF) was also dialyzed, and its retentate was lyophilized. When sperm were incubated in GC- or OC-conditioned media, motility remained above 62% and 42% at 6 hr and 30 hr, respectively, and motility was higher than that of the control both at 6 hr (39%; P < 0.001) and at 30 hr (9%; P < 0.0001). Similarly, when sperm were incubated in the lyophilized retentates of GC- and OC-conditioned media and in BFF at a dose of 0.1, 0.5, or 1.0 mg/ml, the motility rates were higher both at 6 hr (P < 0.05) and at 30 hr (P < 0.01) compared to the control. The increase in motility was dose dependent; a 1.0 mg/ml dose improved (P < 0.05) motility compared to a 0.1 mg mg/ml dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Sperm transport in the human female reproductive tract--a dynamic interaction

The interaction between sperm and the human female tract has been largely ignored. This review summarizes the data available from animal species with specific reference to sperm in the oviduct. Our knowledge of sperm transport within the human female tract is explored and, using the data available from animal species, three lines of future experimental design are suggested. Firstly, there is the need to improve and develop techniques to recover sperm successfully from the tract. Second, an in-vitro approach which examines the modulation of reproductive tract fluids on sperm function is advocated. Third, an in-vitro tissue/cell culture system is required to investigate in more detail the interaction between the epithelium and sperm. Using such approaches many of the questions posed in this review can be addressed confidently in the near future.

Distribution, morphology and epithelial interactions of bovine spermatozoa in the oviduct before and after ovulation: a scanning electron microscope study

In cows undergoing spontaneous oestrous cycles and mated during the first 6 hours of oestrus, the distribution of spermatozoa in the oviduct isthmus and changes in their surface membranes and neighbouring epithelium have been examined shortly before and after ovulation. In agreement with previous histological studies, relatively few spermatozoa were detected in the oviduct lumen: most were located in the caudal isthmus before ovulation, frequently among folds and in the presence of a viscous secretion. A majority of spermatozoa in this region showed strands and droplets of secretory material distributed over the anterior portion of an intact head before ovulation, whereas distribution of material over the post-nuclear cap of spermatozoa close to vesiculation or already acrosome-reacted was characteristic of the post-ovulatory situation. These changes in sperm head membranes were viewed as an expression of the completion of capacitation, and seemingly permit microvillous engagement with the rostral tip of the head. In conjunction with a narrow lumen and viscous secretions in the caudal isthmus, microvilli may thus serve to regulate periovulatory sperm progression towards the site of fertilisation, and be the basis of intermittent phases of adhesion to the oviduct epithelium as seen by phase-contrast microscopy. Although cilia do not similarly engage the heads of bull spermatozoa (cf. boar spermatozoa), they may act to regulate progression of capacitated spermatozoa by contacting the principal piece of the flagellum. In the light of these observations, changes in the molecular composition of sperm surface domains during the process of capacitation in vivo now require specific definition.