Influence of sire fertility status on conceptus-induced transcriptomic response of the bovine endometrium

The aim was to examine the effect of sire fertility status on conceptus-induced changes in the bovine endometrial transcriptome. To generate elongated conceptuses, Day 7 blastocysts produced in vitro using frozen-thawed sperm from Holstein Friesian bulls (3 High fertility, HF and 3 Low fertility, LF) were transferred in groups of 5–10 into synchronized heifers (n = 7 heifers per bull) and recovered following slaughter on Day 15. Day 15 endometrial explants recovered from the uterine horn ipsilateral to the corpus luteum were recovered from synchronized cyclic heifers (n = 4). Explants from each heifer were co-cultured for 6 h in RPMI medium alone (Control) or with 100 ng/ml ovine recombinant interferon tau (IFNT) or with a single conceptus from each HF or LF bull. After 6 h, explants were snap frozen and stored at −80°C. Extracted mRNA was subjected to RNA-seq and the resulting data were analyzed with R software. The numbers of differentially expressed genes (DEG; FDR<0.05) were: HF vs. Control: 956; LF vs. Control: 1021; IFNT vs. Control: 1301; HF vs. LF: 2. Unsurprisingly, the majority of DEG (658) were common to all comparisons and were related to IFNT-induced changes in the endometrium. Prior to applying the adjusted p-value, there were 700 DEG between HF and LF, with 191 and 509 genes more expressed in HF or LF, respectively (p < 0.05). Overrepresentation analysis of KEGG pathways (FDR<0.05), revealed that DEG with higher expression in LF were involved in cell cycle and proteolysis, while those upregulated DEG by HF conceptuses were strongly associated with immune process pathways, such as TNF, NF-kappa B, cytokine-cytokine receptor interaction, and TLR signaling. These pathways were also enriched by DEG upregulated by IFNT compared to the Control. Furthermore, only the HF, and not the LF group, affected the expression of most genes in these pathways (p < 0.05) according to a negative binomial regression model. Finally, a weighted gene co-expression network analysis revealed two clusters of co-expressed genes associated with the HF conceptuses (p < 0.05), which were also enriched for the aforementioned pathways. In conclusion, HF conceptuses, similar to IFNT treatment, stimulated multiple pathways involved in immune response, which were apparently not affected by LF conceptuses.

O-295 Passive sperm sorting does not select for sperm with lower DNA fragmentation levels compared to density gradient centrifugation in split samples

Study question

Does the passive sperm separation device, Zymot, select sperm with lower DNA fragmentation levels compared to Density Gradient Centrifugation (DGC)?

Summary answer

The sperm separation device Zymot did not select sperm with lower DNA fragmentation levels compared to sperm selected by DGC or the neat sample.

What is known already

Previous studies have shown that sperm with high DNA fragmentation levels result in lower fertilisation rates, impaired embryo development, lower pregnancy rates and increases the risk of miscarriage. Currently, prior to fertility treatment, the method of choice for sperm selection is using DGC, which involves the centrifugation of sperm. Therefore, there is a clinical need for a sperm selection method that avoids centrifugation, while mimicking the natural process of sperm selection in the female reproductive tract and selects sperm with intact DNA.

Study design, size, duration

This blinded controlled study included 29 patients from which semen samples were obtained between May 2021- January 2022 at ReproMed fertility clinic (Dublin, Ireland). Ejaculates were split and processed using either DGC, passive separation device (Zymot; 850 uL) or unprocessed (neat; control) and assessed for sperm quality in terms of motility (progressive, non-progressive and immotile), morphology and DNA fragmentation (assessed using the COMET assay). Two hundred sperm were assessed for each analysis.

Participants/materials, setting, methods

Motility and morphology were assessed using microscopy techniques as per WHO guidelines. DNA fragmentation was assessed using the COMET assay and each sample was given an Average COMET score (ACS), Low COMET score (LCS) and High COMET score (HCS). All data were checked for normality of distribution following which they were analysed using analysis of variance (ANOVA) with Bonferroni post-hoc tests. All values presented are mean ± standard error of the mean.

Main results and the role of chance

Sperm sorted by the Zymot device had higher progressive motility (78.7 + 3.42%) than both the neat (53.3 + 3.40%) and DGC (51.8 + 3.74%%) samples (P < 0.001). Sperm selected by DGC had a greater percentage of sperm with non-progressive motility (16.0 + 2.02%) compared to the neat sample (8.6 + 1.11%) and the Zymot device (9.9 + 1.60%). The overall percentage of normal morphology in the neat sample was 4.3 + 0.16% and there was no effect of sperm selection method on the percentage of sperm with normal morphology (P > 0.05). The ACS in the neat sample was 32.5 + 1.48% and neither DGC (28.2 + 1.45%) or Zymot (29.1 + 1.50%) improved this (P > 0.05). In line with this, neither LCS nor HCS differed between the treatments (P > 0.05).

Limitations, reasons for caution

A higher number of patient samples are needed to validate the efficacy of the Zymot sperm separation device on DNA fragmentation levels. Also, targeting patients with higher DNA fragmentation in the neat sample may yield greater benefits.

Wider implications of the findings

The results of this study indicate that the passive sperm selection device, Zymot, selects more motile sperm but does not select sperm with intact DNA. There is a need for a non-cell destructive method to select sperm with intact DNA to improve the outcomes for couples undergoing fertility treatment.

Trial registration number

Not Applicable

Heat illness experience at BMH Shaibah, Basra, during Operation TELIC: May-July 2003

This is an observational study of heat-related illness in UK Service Personnel deployed into summer conditions in Northern Kuwait and Southern Iraq. Among 622 hospitalisations reported during a 9-week period at the historical British Military Hospital, Shaibah, 303 consecutive admissions are reviewed in detail. Several clinical syndromes attributable to thermal stress were observed. These ranged from self-limiting debility to life-threatening failures of homeostasis, with 5.0% developing a critical care requirement. Hyponatraemia was a commonly occurring electrolyte disturbance by which, relative to the local reference range, a majority of heat-attributed admissions were affected. Reductions in measured serum sodium could be profound (<125 mmol/L in 20.1% of all heat-related casualties). Hypokalaemia was observed in half of cases, though only a minority were affected by severely low potassium (<2.5 mmol/L in 4.0%). Despite preventive measures prescribed on hospital discharge, illness and significant biochemical derangements could recur upon return to duties in the heat. We reiterate the need for primary prevention of heat illness wherever possible and importance of early, effective interventions to treat and protect Service Personnel from secondary injury. We also highlight the requirement for comprehensive assessment to inform prognostication and occupational decision-making in relation to extreme climatic heat, including aeromedical evacuation. We draw additional attention to the contribution of psychological factors in select cases and identify research questions to improve understanding of environment-induced incapacitation in general.

Comparison of the uterine inflammatory response to frozen-thawed sperm from high and low fertility bulls

Some bulls with apparently normal semen quality yield unacceptably low pregnancy rates. We hypothesised that a differential uterine immunological response to sperm from high and low fertility bulls may contribute to these differences. The experimental model used was heifer follicular phase uterine explants incubated with frozen-thawed sperm from high and low fertility bulls (3-5 replicates per experiment). Inflammatory gene expression of IL1A, IL1B, IL6, TNFA and CXCL8 were assessed by qPCR and IL1-β and IL-8 were quantified in explant supernatants by ELISA. Neutrophil binding affinity to sperm from high and low fertility bulls was also assessed. There was a significant up-regulation of IL1A, IL1B and TNFA from frozen-thawed sperm, irrespective of fertility status, compared to the unstimulated control. This response was confirmed at the protein level, with an increase of IL-1β and IL-8 protein concentrations by 5 and 2.7 fold, respectively (P < 0.05). Although no significant differences in the inflammatory response at the gene or protein level were evident between high and low fertility bulls, more sperm from low compared to high fertility bulls bound to neutrophils (P < 0.05). Using bulls of unknown fertility, cauda epididymal sperm (CES) plus seminal plasma (SP) upregulated IL6 (P < 0.05) but there was no upregulation of any inflammatory gene expression for CES alone. Overall, this ex vivo study demonstrated an upregulation of inflammatory gene expression in the uterus in response to frozen-thawed bull sperm. While there was no difference between sperm from high and low fertility bulls, there was a greater binding affinity of low fertility sperm by neutrophils.

Diagnosis, management, and outcomes of venous thromboembolism in COVID-19 positive patients: a role for direct anticoagulants?

Coronavirus disease 2019 (COVID-19) has been associated with an increased risk of thromboembolic complications due to systemic coagulation activation. Little is known about the role of direct anticoagulants (DOACs) in COVID-19 related thrombosis. In this audit we sought to distinguish COVID-19 hospitalised patients with a diagnosis of venous thromboembolism (VTE) and record their outcomes over a period of 3 months (01/02/2020–30/04/2020). A total of 1583 patients were diagnosed with laboratory proven COVID-19 disease. Amongst them, 38 patients (0.82%) suffered VTE (median age 68 years, male/female: 20/18). VTE was the presenting symptom on admission in 71%. Pulmonary embolism was diagnosed in 92% of patients; 5 patients required intensive care and 3 underwent thrombolysis. 27 patients received initial treatment with unfractionated heparin/low molecular weight heparin (LMWH) while 10 were treated with direct anticoagulants (DOACs). After a median follow up of 25 days, 29 (76%) patients were alive while 5 were still hospitalised. Most patients (83%) were discharged on DOACs, no VTE recurrence or bleeding was recorded post-discharge. Our results suggest that direct anticoagulants could be a safe and effective treatment option in selected COVID-19 positive patients who have suffered venous thromboembolism.

Sire contribution to fertilization failure and early embryo survival in cattle

Despite passing routine laboratory tests of semen quality, bulls used in artificial insemination (AI) exhibit a significant range in field fertility. The objective of this study was to determine whether subfertility in AI bulls is due to issues of sperm transport to the site of fertilization, fertilization failure, or failure of early embryo or conceptus development. In experiment 1, Holstein-Friesian bulls (3 high fertility, HF, and 3 low fertility, LF) were selected from the national population of AI bulls based on adjusted fertility scores from a minimum of 500 inseminations (HF: +4.37% and LF: -12.7%; mean = 0%). Superovulated beef heifers were blocked based on estimated number of follicles at the time of AI and inseminated with semen from HF or LF bulls (n = 3-4 heifers per bull; total 19 heifers). Following slaughter 7 d later, the number of corpora lutea was counted and the uteri were flushed. Recovered structures (oocytes/embryos) were classified according to developmental stage and stained with 4',6-diamidino-2-phenylindole to assess number of cells and accessory sperm. Overall recovery rate (total structures recovered/total corpora lutea) was 52.6% and was not different between groups. Mean (± standard error of the mean) number of embryos recovered per recipient was 8.7 ± 5.2 and 9.4 ± 5.5 for HF and LF, respectively. Overall fertilization rate of recovered structures was not different between groups. However, more embryos were at advanced stages of development (all blastocyst stages combined), reflected in a greater mean embryo cell number on d 7 for HF versus LF bulls. Number of accessory sperm was greater for embryos derived from HF than for LF bulls. The aim of experiment 2 was to evaluate the effect of sire fertility on survival of bovine embryos to d 15. Day 7 blastocysts were produced in vitro using semen from the same HF (n = 3) and LF (n = 3) bulls and transferred in groups of 5-10 to synchronized heifers (n = 7 heifers per bull; total 42 heifers). Conceptus recovery rate on d 15 was higher in HF (59.4%,) versus LF (45.0%). Mean length of recovered conceptuses for HF bulls was not affected by fertility status. In conclusion, while differences in field fertility among AI sires used in this study were not reflected in fertilization rate, differences in embryo quality were apparent as early as d 7. These differences likely contributed to the higher proportion of conceptuses surviving to d 15 in HF bulls.

101 Heifer plane of nutrition during the prepubertal phase modifies reproductive development in male fetuses

Maternal nutritional perturbation during gestation influences fetal development which, in turn, can affect postnatal growth, gonad development, gamete quality, and health of the offspring. The objective of this study was to determine whether maternal diet during the pre-pubertal phase would induce modifications in future male fetal reproductive development. Angus×Holstein-Friesian heifers (n=80) with a mean (±s.d.) age of 141±8d and bodyweight (BW) of 119±23kg had unrestricted access to a perennial ryegrass dominated sward supplemented with either 0.5kg of concentrate daily to achieve an average daily gain (ADG) of 0.50kg (moderate, MOD) or concentrate ad libitum to achieve an ADG of &gt;1.0kg (high, HI). Heifers were offered these divergent dietary regimens from 4.5 to 8.5 months of age, after which they were all offered a moderate plane of nutrition. Heifers were bred to a synchronised oestrus at a mean age of 502±8.2d and mean BW of 360±46.7kg using semen from a single proven sire. Transrectal uterine ultrasonography was carried out 63 days post-AI to determine pregnancy and fetal sex; a cohort of heifers reflective of group average BW and age and carrying male fetuses were slaughtered on Day 100 of gestation (HI: n=10; MOD: n=12). Fetal crown–rump length and weight were recorded. One testis was snap frozen for RNA sequencing and the other was processed for stereology. Mean (±s.d.) fetal crown–rump length and weight were 19.5±0.69cm and 314.6±33.6g, respectively, and did not differ between groups. RNA sequencing revealed 45 differentially expressed genes (DEGs) between groups, 44 of which were upregulated in the HI group. A total of 29 biochemical pathways were identified as significantly enriched (P&lt;0.05), six of which were predicted to be involved in the development of the reproductive tract based on several DEGs. Histological analysis revealed greater (P&lt;0.05) fetal testicular interstitial tissue density in the MOD group and a strong tendency towards increased seminiferous tubule density (P=0.06) in the HI group. In conclusion, offering a high plane of nutrition during the prepubertal period not only increases the rate of sexual development in the heifer but also induces latent in utero modifications to the testicular development of their subsequent male progeny. The consequences for postnatal development of male progeny remain to be elucidated. This research was supported by Science Foundation Ireland (16/IA/4474).

Ewe breed differences in cervical anatomy and cervicovaginal mucus properties: An international study

In sheep, cervical artificial insemination (AI) involves depositing semen at the cervical opening, as it is not possible to traverse the cervix due to its complex anatomy. However, internationally this method yields low pregnancy rates when frozen-thawed semen is used. An exception to this is in Norway, in which vaginal deposition of frozen-thawed semen to a natural estrus yields pregnancy rates around 70%. As the cervix and its secretions are the principal factors influencing sperm transport to the site of fertilization the aim of this study was to characterise the differences in the cervical anatomy as well as the cervicovaginal mucus properties of six European ewe breeds across three countries known to have differences in pregnancy rates following cervical AI with frozen-thawed semen. These were Suffolk and Belclare in Ireland, Fur and Norwegian White Sheep (NWS) in Norway and Ile de France and Romanov in France (n = 28-30 ewes/breed). Cervicovaginal mucus was collected at the follicular and luteal phases of both a synchronized and natural cycle and assessed for mucus weight, viscosity and colour. The anatomical characteristics of the cervix (length of the cervix, number of cervical rings and the appearance of the external os) were assessed post-mortem. There was a type of the cycle by ewe breed interaction represented by no differences in mucus production between ewe breeds at the natural cycle for both the follicular and luteal phases of the cycle. However, there were differences between ewe breeds at the synchronized cycle (P < 0.05). Belclare had the lowest mucus production at the follicular phase while NWS had the lowest amount of mucus at the luteal phase of the synchronized cycle. Overall, across all ewe breeds, mucus production was higher at the follicular than at the luteal phase (P < 0.05). Despite reports of Suffolk and NWS having the most divergent pregnancy rates following cervical AI with frozen-thawed semen, both breeds had the lowest overall mucus viscosity at the follicular phase of both types of cycle with no differences between both ewe breeds (P > 0.05). The length of the cervix, number of cervical rings and the external os type were affected by ewe breed (P < 0.05). Suffolk ewes had longer cervices but lower number of cervical rings than NWS and Fur ewes (both with higher pregnancy rates). In conclusion, while mucus production and mucus viscosity was affected by breed, these changes are not consistent with the known differences between ewe breeds in their pregnancy rates following cervical AI with frozen-thawed semen.

Cervical mucus sialic acid content determines the ability of frozen-thawed ram sperm to migrate through the cervix

The aim of this study was to investigate the properties and to functionally characterize the cervical mucus that modulates sperm transport through the cervix by using ewe breeds with a divergent pregnancy rate (Belclare and Suffolk; high and low, respectively) following cervical insemination using frozen-thawed semen. Sperm number, as well as sialic acid and fucose content in both the channels and in the lumen of different regions of the cervix were quantified in inseminated Belclare and Suffolk ewes. Expression of glycosyltransferase and MUC genes, glycosidase activity and sialic acid speciation in follicular phase cervical tissue and mucus were assessed. More spermatozoa were found in the cervical channels in the region closest to the cervical os in Belclare than Suffolk ewes (P < 0.05) and Suffolk ewes had a higher sialic acid content in the cervical channels than Belclare ewes (P < 0.05) in all regions of cervix. Suffolk ewes had significantly higher expression of FUT1, ST6GAL1 and MUC5AC than Belclare ewes. There was no difference between the breeds in glycosidase activity (P > 0.05). Levels of Neu5Ac were higher in Belclare than Suffolk ewes (P < 0.05) and levels of Neu5Gc was higher in Suffolk than Belclare ewes (P < 0.05). Competitive sperm penetration assays demonstrated that frozen-thawed sperm progression increased when cervical mucus was incubated with sialyllactose prior to a sperm penetration test (P < 0.05). These results suggest that the difference between Belclare and Suffolk ewes in sperm transport with frozen-thawed semen is due to the higher concentration of sialic acid within channels, which binds to spermatozoa and reduces their ability to traverse the cervix.

The biological mechanisms regulating sperm selection by the ovine cervix

In species where semen is deposited in the vagina, the cervix has the unique function of facilitating progress of spermatozoa towards the site of fertilisation while also preventing the ascending influx of pathogens from the vagina. For the majority of species, advances in assisted reproduction techniques facilitate the bypassing of the cervix and therefore its effect on the transit of processed spermatozoa has been largely overlooked. The exception is in sheep, as it is currently not possible to traverse the ovine cervix with an inseminating catheter due to its complex anatomy, and semen must be deposited at the external cervical os. This results in unacceptably low pregnancy rates when frozen-thawed or liquid stored (>24 h) semen is inseminated. The objective of this review is to discuss the biological mechanisms which regulate cervical sperm selection. We assess the effects of endogenous and exogenous hormones on cervical mucus composition and discuss how increased mucus production and flow during oestrus stimulates sperm rheotaxis along the crypts and folds of the cervix. Emerging results shedding light on the sperm-cervical mucus interaction as well as the dialogue between spermatozoa and the innate immune system are outlined. Finally, ewe breed differences in cervical function and the impact of semen processing on the success of fertilisation, as well as the most fruitful avenues of further investigation in this area are proposed.

Implications of boar sperm kinematics and rheotaxis for fertility after preservation

Artificial insemination (AI) is the single most important assisted reproductive technique devised to facilitate the genetic improvement of livestock. In the swine industry, it has broadly replaced natural service over the last number of decades which has been made possible by the high pregnancy rates and litter sizes obtainable with semen extended, up to, and sometimes beyond 5 d. Central to achieving good reproductive performance is the ability of boar studs to monitor semen quality, the basis of which has long been the assessment of sperm motility by subjective and, more recently, by more objective computerised systems. In this review, the literature on the relationship between sperm motility and kinematic parameters and field fertility is summarised. We discuss how this relationship is dependent on factors such as the viscosity of the media and the use of standard operating procedures. Emerging evidence is discussed regarding the importance of sperm rheotaxis and thigmotaxis as long-distance sperm guidance mechanisms, which enable motile functional spermatozoa to avoid the backflow of fluid, mucus and semen from the sow's uterus in the hours post AI, facilitating the establishment of sperm reservoirs in the oviducts. The literature on the use of microfluidics in studying sperm rheotaxis in vitro is also summarised, and we discuss how these systems, when combined with techniques such as lensless microscopy, have the potential to offer more physiological assessments of the swimming patterns of boar spermatozoa. Finally, possible future avenues of further investigation are proposed.

Progesterone induces the release of bull spermatozoa from oviductal epithelial cells

The mechanism that causes the detachment of spermatozoa from the oviductal reservoir around the time of ovulation remains to be elucidated. Because the cumulus cells of the bovine oocyte are known to secrete progesterone (P4), and P4 has been shown to act upon cation channels of spermatozoa (CatSper) in human spermatozoa, it was hypothesised that P4 could induce hyperactivation due to an influx of extracellular calcium, and this would facilitate detachment of spermatozoa from oviductal epithelial cells. Therefore, this study aimed to investigate the role and mechanism of action of P4 in the release of spermatozoa from bovine oviduct epithelial cells (BOEC). Initial dose–response assessments on sperm hyperactivation determined the optimum concentration of P4 (10 nM), mibefradil (a non-specific Ca2+ channel antagonist; 5µM), NNC 55-0396 dihydrochloride (NNC; a CatSper antagonist; 2µM), mifepristone (a classical and membrane P4 receptor antagonist; 400nM) and AG205 (a membrane P4 receptor antagonist; 10μM). BOEC explants were incubated with frozen–thawed bovine spermatozoa for 30min, following which loosely bound spermatozoa were removed. Two experiments were completed. In Experiment 1, BOECs were treated for 30min with either no treatment, P4, NNC, mibefradil, P4+mibefradil, P4+NNC, P4+mibefradil+NNC or P4+EGTA. In Experiment 2, BOECs were treated for 30min with either no treatment, P4, mifepristone, AG205, mifepristone+AG205, P4+mifepristone, P4+AG205 or P4+mifepristone+AG205. The number of spermatozoa remaining bound per millimetre squared of BOEC explant was determined. Progesterone stimulated the release of bound spermatozoa from BOEC explants, whereas NNC, mibefradil and EGTA inhibited this release. The release of spermatozoa by P4 was inhibited in the presence of both mifepristone and AG205, whereas the combination of both had the greatest inhibitory action on P4 release of spermatozoa. These findings suggest the presence of a P4 membrane receptor on bovine spermatozoa and that P4-induced release of spermatozoa from BOECs is likely mediated by extracellular Ca2+.

Effect of Early Calf-Hood Nutrition on the Transcriptional Regulation of the Hypothalamic-Pituitary-Testicular axis in Holstein-Friesian Bull Calves

The aim of this study was to investigate the effect of early calf-hood nutrition on the transcriptomic profile of the arcuate nucleus of the hypothalamus, anterior pituitary and testes in Holstein-Friesian bulls. Holstein-Friesian bull calves with a mean (±S.D.) age and bodyweight of 19 (±8.2) days and 47.5 (±5.3) kg, respectively, were offered a high (n = 10) or low (n = 10) plane of nutrition in order to achieve an overall growth rate of 1.2 and 0.5 kg/day. At 126 (±3) days of age, calves were euthanized, hypothalamus (arcuate region), anterior pituitary and testicular parenchyma samples were harvested and RNAseq analysis was performed. There were 0, 49 and 1,346 genes differentially expressed in the arcuate nucleus, anterior pituitary and testicular tissue of bull calves on the low relative to the high plane of nutrition, respectively (P < 0.05; False Discovery Rate <0.05). Cell cycle processes in the anterior pituitary were down regulated in the low relative to the high plane of nutrition; there was no differential expression of genes related to reproductive processes. Gene expression involved in cholesterol and androgen biosynthesis in the testes were down regulated in animals on the low plane of nutrition. This study provides insight into the effect of early life plane of nutrition on the regulation of the HPT axis.

Role of early life nutrition on regulating the hypothalamic–anterior pituitary–testicular axis of the bull

The objective of this study was to examine the effect of nutrition during the first 18 weeks of life on the physiological and transcriptional functionality of the hypothalamic (arcuate nucleus region), anterior pituitary and testes in Holstein–Friesian bull calves. Holstein–Friesian bull calves with a mean (±S.D.) age and bodyweight of 19 (±8.2) days and 47.5 (±5.3) kg, respectively, were assigned to either a HIGH (n = 10) or LOW (n = 10) plane of nutrition, to achieve an overall target growth rate of 1.2 or 0.5 kg/day, respectively. At 126 ± 1.1 days of age, all calves were euthanised. Animal performance (weekly) and systemic concentrations of metabolic (monthly) and reproductive hormones (fortnightly) were assessed. Testicular histology, targeted gene and protein expression of the arcuate nucleus region, anterior pituitary and testes were also assessed using qPCR and immunohistochemistry, respectively. The expression of candidate genes in testicular tissue from post pubertal 19-month-old Holstein–Friesian bulls (n = 10) was compared to that of the 18-week-old calves. Metabolite and metabolic hormone profiles generally reflected the improved metabolic status of the calves on the HIGH (P< 0.001). Calves offered a HIGH plane of nutrition were heavier at slaughter (P < 0.001), had larger testes (P < 0.001), larger seminiferous tubule diameter (P < 0.001), more mature spermatogenic cells (P < 0.001) and more Sertoli cells (P < 0.05) in accordance with both morphological and transcriptional data. Overall, testicular gene expression profiles suggested a more mature stage of development in HIGH compared with LOW and were more closely aligned to that of mature bulls. Ghrelin receptor was the only differentially expressed gene between LOW and HIGH calves in either the anterior pituitary (P < 0.05) or arcuate nucleus region of the hypothalamus (P < 0.10) and was upregulated in LOW for both tissues. This study indicates that an enhanced plane of nutrition during early calfhood favourably alters the biochemical regulation of the hypothalamus–anterior pituitary–testicular axis, advancing testicular development and hastening spermatogenesis.

Removal of sialic acid from bull sperm decreases motility and mucus penetration ability but increases zona pellucida binding and polyspermic penetration in vitro

This study tested the hypothesis that sperm sialic acid (Sia) is required to reach the site of fertilization, and that successful fertilization requires recognition of Sia from both the sperm and oocyte to occur. In addition, it has recently been reported that Siglecs (Sia-binding-immunoglobulin-like lectins) are present on the sperm surface. Thus, the possibility that the recognition of oocyte Sia was sperm-Siglec-mediated was also addressed. Sperm exposed to neuraminidase (NMase) exhibited lower overall and progressive motility, which translated to a decreased ability to swim through cervical mucus from cows in oestrus. In addition, when either sperm or cumulus-oocyte complexes (COCs) were treated with NMase, a decrease in cleavage and blastocyst rate was observed. However, incubation of sperm with increasing concentrations of anti-Siglec-2, -5, -6 and -10 antibodies prior to fertilization had no effect on their fertilizing ability. Interestingly, treatment with NMase increased the number of sperm bound to the ZP but also the rate of polyspermic fertilization. Flow cytometry analysis revealed no differences in the percentage of capacitated or acrosome-reacted sperm. These results suggest that Sia are required to reach the site of fertilization but need to be removed for sperm-oocyte interaction. However, fine regulation is needed to avoid abnormal fertilization which can lead to impaired embryo development.

Comparison of plant- and egg yolk-based semen diluents on in vitro sperm kinematics and in vivo fertility of frozen-thawed bull semen

Diluents using components of plant origin have been developed as an alternative to animal based extenders for the dilution of bull semen, however, it is unclear if use of these diluents results in in vivo fertility rates similar to those that occur with use of traditional egg yolk-based diluents. The aim of this study was to assess the effect of semen diluent on 60-day non-return rate (NRR) following artificial insemination (AI) with frozen-thawed bull semen. The effect of semen dilution in one of three different commercial diluents (BullXcell - egg yolk-based, OptiXcell - plant-based or AndroMed - plant-based) on post-thaw total and progressive motility as well as kinematic parameters (Experiment 1) and field fertility (Experiment 2, n = 1,480 inseminations) was assessed. Semen stored in OptiXcell had greater post-thaw total and progressive motility than AndroMed (P < 0.05) but did not differ from BullXcell. Semen stored in BullXcell had a greater beat cross frequency and straight line velocity compared to semen stored in AndroMed (P < 0.05) but did not differ when compared with use of OptiXcell; while values for these variables when using OptiXcell and AndroMed did not differ from each other (P > 0.05). There was no difference in any other sperm kinematic parameters (P > 0.05). There was no effect of diluent on 60-day NRR (71.5%, 67.8% and 70.6% for BullXcell, OptiXcell and AndroMed, respectively). In conclusion, while diluent significantly affected post-thaw sperm motility and kinematics, no effect on 60-day NRR was observed. Given that OptiXcell and AndroMed are animal protein-free media these diluents may be a suitable alternative to BullXcell for the storage of frozen-thawed bull semen.

Recombinant β-defensin 126 promotes bull sperm binding to bovine oviductal epithelia

Primate β-defensin 126 regulates the ability of spermatozoa to bind to oviductal epithelial cells in vitro. Bovine β-defensin 126 (BBD126) exhibits preferential expression in the cauda epididymis of the bull, but there have been few studies on its functional role in cattle. The aim of the present study was to examine the role of BBD126 in bull sperm binding to bovine oviductal epithelial cell (BOEC) explants. BBD126 has been shown to be highly resistant to the standard methods of dissociation used in other species and, as a result, corpus epididymal spermatozoa, which have not been exposed to the protein, were used to study the functional role of BBD126. Corpus epididymal spermatozoa were incubated with recombinant (r) BBD126 in the absence or presence of anti-BBD126 antibody. Addition of rBBD126 significantly enhanced the ability of epididymal spermatozoa to bind to BOEC explants (P < 0.05). Anti-BBD126 antibody blocked the BBD126-mediated increase in sperm binding capacity. Ejaculated spermatozoa, which are coated with native BBD126 protein but also a large number of seminal plasma proteins in vivo, were incubated with rBBD126 in the absence or presence of the anti-BBD126 antibody. Addition of rBBD126 significantly enhanced the ability of ejaculated spermatozoa to bind to BOEC explants (P < 0.05), whereas rBBD126 also reduced corpus sperm agglutination (P < 0.05). These results suggest that, similar to the role of its analogue in the macaque, spermatozoa with more BBD126 in their acrosome may represent spermatozoa with more oviduct binding capacity.

Effect of storage temperature, nitrogen gassing and sperm concentration on the in vitro semen quality and in vivo fertility of liquid bull semen stored in INRA96

The aim of this study was to assess the effect of storage temperature, nitrogen (N₂) gassing and sperm concentration on in vitro characteristics and calving rate (CR) following artificial insemination (AI) of liquid bull semen stored in INRA96. In Experiment 1 the effect of liquid bull semen diluted in either N₂ bubbled or non-bubbled INRA96 at a concentration of 5 × 10⁶ sperm per 0.25 mL insemination dose and stored at 5 or 15 °C was assessed subjectively for total and progressive motility on Days 0, 1, 2, 3 and 4 post collection. In Experiment 2a, the effect of stored liquid semen at three sperm concentrations (3, 4 or 5 × 10⁶ sperm per 0.25 mL insemination dose) on total and progressive motility was assessed subjectively on Days 0, 1 and 2 post collection. In Experiment 2b, the field fertility of liquid semen stored at ambient temperature at a concentration of 3, 4 or 5 × 10⁶ sperm per 0.25 mL dose and inseminated on Days 1 or 2 post collection was assessed in comparison to frozen-thawed semen (total of n = 5742). In Experiment 1, total and progressive motility decreased with increased duration of storage (P < 0.01); however, there was no effect of N₂ bubbling on motility on Days 0, 1, 2, 3 and 4 of storage. There was an effect of temperature on total and progressive motility, regardless of treatment, as semen stored at 15°C recorded higher motility values than semen stored at 5°C (P < 0.01). In Experiment 2a, there was no effect of sperm concentration on total or progressive motility on Days 0, 1 or 2 of storage. There was a linear decrease in motility with increased duration of storage (P < 0.01); however, there was no sperm concentration by day interaction. In Experiment 2b, there was an effect of sperm concentration on CR (P < 0.01); semen diluted to 3 and 4 × 10⁶ sperm per dose resulted in a lower CR after 2 days of storage (41.1 and 44.7%, respectively) in comparison to frozen-thawed semen (55.2%) but did not differ to CR of semen diluted to 5 × 10⁶ sperm per dose on Day 2 of storage. There was an effect of parity, fertility sub-index and days in milk (DIM) at AI on CR (P < 0.01). In conclusion, N₂ bubbling and sperm concentration had no effect on in vitro sperm motility of liquid semen, but this study demonstrated a reduction in CR on Day 2 of storage at lower sperm concentrations in comparison to frozen-thawed semen.

Comparative genomic identification and validation of β-defensin genes in the Ovis aries genome

Background

β-defensins are small, cationic, antimicrobial peptides found in species across the plant and animal kingdoms. In addition to microbiocidal activity, roles in immunity as well as reproduction have more recently been documented. β-defensin genes in Ovis aries (domestic sheep) have been poorly annotated, having been identified only by automatic gene prediction algorithms. The objective of this study was to use a comparative genomics approach to identify and characterise the β-defensin gene repertoire in sheep using the bovine genome as the primary reference.

Results

All 57 currently predicted bovine β-defensin genes were used to find orthologous sequences in the most recent version of the sheep genome (OAR v4.0). Forty three genes were found to have close genomic matches (>70% similarity) between sheep and cattle. The orthologous genes were located in four clusters across the genome, with 4 genes on chromosome 2, 19 genes on chromosome 13, 5 genes on chromosome 20 and 15 genes on chromosome 26. Conserved gene order for the β-defensin genes was apparent in the two smaller clusters, although gene order was reversed on chromosome 2, suggesting an inversion between sheep and cattle. Complete conservation of gene order was also observed for chromosome 13 β-defensin orthologs. More structural differences were apparent between chromosome 26 genes and the orthologous region in the bovine reference genome, which is known to be copy-number variable. In this cluster, the Defensin-beta 1 (DEFB1) gene matched to eleven Bovine Neutrophil beta-Defensin (BNBD) genes on chromosome 27 with almost uniform similarity, as well as to tracheal, enteric and lingual anti-microbial peptides (TAP, EAP and LAP), suggesting that annotation of the bovine reference sequence is still incomplete. qPCR was used to profile the expression of 34 β-defensin genes, representing each of the four clusters, in the ram reproductive tract. Distinct site-specific and differential expression profiles were detected across the reproductive tract of mature rams with preferential β-defensin gene expression in the epididymis, recapitulating observations for orthologous genes in other species.

Conclusions

This is the first comprehensive analysis of β-defensin genes encoded by the ovine reference sequence, and the first report of an expanded repertoire of β-defensin genes in this species. The preferential expression of these genes in the epididymis suggests a role in fertility, possibly providing immunoprotection for sperm within the female reproductive tract.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3666-x) contains supplementary material, which is available to authorized users.

In vitro addition of docosahexaenoic acid improves the quality of cooled but not frozen-thawed stallion semen

The aim of the present study was to assess the effect of the addition of docosahexaenoic acid (DHA) on the in vitro quality of cooled and frozen-thawed stallion semen. In Experiment 1, semen from 10 stallions was collected (three ejaculates per stallion). Semen was diluted to 100×10⁶ spermatozoa mL^-1 with 0.02mM vitamin E (VE) and 0, 1, 10 or 20ng mL^-1 DHA and frozen. Semen was thawed and total motility (TM), rapid progressive motility (PM), acrosome integrity, membrane fluidity and morphology were assessed. In Experiment 2, semen from three stallions was collected (three ejaculates per stallion) and frozen as in Experiment 1, but VE and DHA were added after thawing. TM and PM were assessed at 30, 60 and 120min and viability, acrosome integrity and membrane fluidity were evaluated at 30min. In Experiment 3, semen from five stallions was collected (one to three ejaculates per stallion), diluted to 20×10⁶ spermatozoa mL^-1 and stored at 4°C. After 1, 24, 48 and 72h, TM, PM, viability, membrane fluidity and lipid peroxidation were assessed. The addition of DHA had no effect on frozen semen (Experiments 1 and 2) but improved TM, PM and membrane fluidity in cooled stallion semen.

Effect of seminal plasma from high- and low-fertility bulls on cauda epididymal sperm function

The aim of this study was to characterise the effect of seminal plasma (SP) from bulls of high or low fertility on sperm function. First, the effect of SP on the motility of fresh cauda epididymal spermatozoa (CES) and frozen–thawed ejaculated spermatozoa was assessed (Experiment 1a). Seminal plasma was then collected from bulls of known high and low fertility. Pooled CES were incubated in the SP from each bull, diluted and assessed for motility and viability on Days 1, 2, 3 and 5 after packaging as fresh semen (Experiment 1b). Also assessed were motility, kinematics, viability and mitochondrial membrane potential after thawing (Experiment 1c) as well as hypotonic resistance (Experiment 2) and fertilisation potential using in vitro fertilisation (Experiment 3). Seminal plasma increased the motility of CES (P < 0.05); however, there was no effect of SP on the motility and viability of fresh CES or on CES post-thaw motility, viability and mitochondrial membrane potential (P > 0.05). The hypotonic resistance of CES was reduced by SP (P < 0.05), irrespective of whether the SP was from high- or low-fertility bulls. Seminal plasma from high- or low-fertility bulls had no effect on cleavage or blastocyst rates (P > 0.05). In conclusion, SP affects the physiological function of CES but there is no difference between SP from high- or low-fertility bulls.

The effect of dietary supplementation of algae rich in docosahexaenoic acid on boar fertility

The objective of this study was to assess the effects of dietary supplementation of a commercial algal product rich in docosahexaenoic acid (DHA) on boar fertility as assessed in vitro and in vivo. Boars were fed one of three experimental diets for 19 weeks: (i) Control (Ctl) diet (n = 31), (ii) Ctl diet plus 75g All-G-Rich per day (n = 31) or (iii) Ctl diet plus 150g All-G-Rich per day (n = 30). Parameters assessed were (i) raw semen quality; volume, sperm concentration, total motility and morphology (ii) liquid semen quality; progressive motility, viability, hypotonic resistance and acrosomal integrity (iii) frozen-thawed semen quality; motility, thermal stress, viability, membrane fluidity and mitochondrial activity (iv) sperm and seminal plasma (SP) fatty acid composition (FAC) (v) total antioxidant capacity (TAC) of SP and (vi) farrowing rates and litter sizes of sows (n = 1158) inseminated with liquid semen. Boars consuming 75g All-G-Rich had a larger semen volume (P < 0.05) and a higher total sperm number (P < 0.01) than the Ctl treatment, however, there was no effect of treatment on any other semen quality parameter (P > 0.05). There was no effect of dietary treatment on the FAC and TAC of SP or on farrowing rate and litter size (P > 0.05). There was an effect of dietary treatment on the FAC of sperm, represented by an 1.72 and 1.60 fold increase in the DHA content for 75 and 150g treatments, respectively, compared to the Ctl treatment. In conclusion, a significant increase in semen volume and total sperm number in boars supplemented 75g All-G-Rich daily, resulted in an increase in production of 3 to 4 more doses per ejaculate, thus, indicating that the feeding regime described within this study has the potential for increasing the output of boar studs.

Relationship between in vitro sperm functional assessments, seminal plasma composition, and field fertility after AI with either non-sorted or sex-sorted bull semen

The hypothesis of this study was that different in vitro parameters are required to predict the in vivo fertility of non-sorted (NS) and sex-sorted (SS) semen. Thus, the aim was to correlate in vitro bull sperm functional parameters (experiment 1) and seminal plasma composition (experiment 2) with pregnancy rates using 2 cohorts of bulls (NS and SS). Experiment 1: ejaculates from each bull (n = 3 ejaculates per bull; n = 6 bulls for both NS and SS) were assessed for motility, thermal stress tolerance and morphology using microscopy, and viability, osmotic resistance, mitochondrial membrane potential, and acrosome integrity using flow cytometry. Fertilizing ability was assessed using IVF. Experiment 2: ejaculates (n = 3 per bull; n = 8 and 6 bulls for NS and SS, respectively) were collected, seminal plasma harvested and frozen and later analyzed for amino acid and fatty acid composition using gas chromatography mass spectrometry. In the NS cohort of bulls, there was no correlation between pregnancy rate and any of the sperm functional parameters assessed. However, within the SS cohort, motility and viability were correlated with pregnancy rate (r = 0.84 and 0.80, respectively; P < 0.05). There was no correlation between IVF outcome and pregnancy rate in either the SS or NS cohort of bulls. In the NS cohort of bulls, concentrations of the amino acid isoleucine and the fatty acid tricosylic acid (C23:0) were correlated with pregnancy rate (r = 0.80 and 0.74, respectively; P < 0.05). Within the SS cohort of bulls, the amino acid glutamic acid and the fatty acid arachidic acid (C20:0) were correlated with pregnancy rate (r = 0.84 and 0.82, respectively; P < 0.05). In conclusion, this study suggests that different in vitro markers of fertility are required to predict the fertility of NS and SS sperm.

3 ROLE OF β-DEFENSIN 126 IN PROMOTING SPERM MOTILITY IN CATTLE

As immature sperm migrate through the epididymis, they are bathed in region-specific epididymal fluid, which leads to a sequential addition, deletion, and modification of their surface proteins. These changes ultimately result in the acquisition of motility and fertilising abilities. Among the hundreds of proteins secreted by the epididymis, several β-defensins have been identified and correlated with male fertility in multiple species. In cattle, β-defensin 126 (BD126) is exclusively detected in the reproductive tract of pubertal males, with preferential mRNA expression in the epididymis. Both the macaque and human orthologs have been shown to play a role in the ability of sperm to migrate through cervical mucus. The aim of this study was to examine the role of bovine BD126 in sperm function. Western blot revealed that the peptide is uniquely present in both the cauda epididymis sperm and fluid and is absent from sperm recovered from other proximal epididymal regions, or the ejaculate of vasectomised animals. Confocal analysis showed immunofluorescent labelling of BD126 specific to the tail and acrosomal region in cauda sperm only, suggesting a role in motility. We hypothesised that addition of cauda epididymal fluid (CEF) or recombinant BD126 (rBD126) to immature corpus sperm would improve ability to penetrate cervical mucus. Testes from adult bulls were collected at an abattoir, and sperm from the corpus and cauda epididymis, as well as CEF, were recovered. Corpus sperm were incubated for 1 h with CEF in the absence or presence of BD126 antibody, or with different rBD126 concentrations (30 or 60 μg mL–1); untreated corpus and cauda sperm were used as controls. A higher number of cauda than corpus sperm migrated through cervical mucus from oestrus cows (P < 0.001), and addition of CEF increased the number of corpus sperm migrating through this matrix (P < 0.05). The presence of the BD126 antibody in CEF failed to abrogate this effect. Western blot analysis of the sperm samples revealed the antibody was not successful in blocking BD126 from binding onto the sperm surface, which would explain the lack of differences observed. Furthermore, the addition of rBD126 did not increase corpus sperm migration through mucus. In conclusion, we have characterised the expression of bovine BD126 protein in the bovine testis and epididymis. Incubation of sperm from the corpus with CEF from the cauda resulted in enhanced sperm migration through cervical mucus. However, incubation of sperm with rBD126 in the absence of other factors and proteins from the CEF failed to produce the same effect. These results suggest that the role of BD126 in cattle is different from that observed in primates. We are currently investigating other roles of BD126 and related β-defensins in mediating bovine sperm function. This work was supported by a grant from the Irish Department of Agriculture, Food and The Marine under the Research Stimulus Programme (Grant No. 11S 104).

The effect of the in vitro supplementation of exogenous long-chain fatty acids on bovine sperm cell function

This study aimed to investigate the effects of long-chain fatty acids (α-linolenic acid (ALA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), linoleic acid (LA), oleic acid (OA) and palmitic acid (PA)) at concentrations of 10-100 µM, on extended bull spermatozoa stored in vitro for up to 7 days. Progressive linear motion (PLM), viability (Experiments 1-3), ability to penetrate artificial mucus (Experiment 1), reactive oxygen species (ROS; Experiment 2) and superoxide production (Experiment 3) were assessed. Spermatozoa maintained the ability to penetrate artificial mucus up to Day 4, irrespective of treatment. In Experiments 2 and 3, DHA and EPA had detrimental effects on PLM and viability. PA preserved PLM and viability at levels greater than the control (P<0.05), whilst keeping ROS levels to a minimum, particularly on Days 1 and 3 (P<0.01) when ROS generation peaked in other treatments. In contrast, superoxide production peaked on Day 0 (Experiment 3) and declined thereafter with no significant effect of fatty acid. This study supports the notion that superoxide dominates on Day 0, whereas its breakdown products, hydrogen peroxide and the hydroxyl radical as assessed by CM-H2DCFDA, contribute to ROS generation on subsequent days.

Reducing sperm concentration is critical to limiting the oxidative stress challenge in liquid bull semen

Because of the short breeding season, the use of liquid bull semen is a viable option in seasonal grass-based dairy systems such as Ireland. Currently in Ireland, liquid bull semen contains approximately 5 million sperm per insemination dose and is used within 2.5d of collection. The hypothesis of this study was that reducing the sperm number per insemination dose would enable bull sperm to be stored for longer. Semen was collected at a commercial AI center and diluted to 1 (T1), 2 (T2), 3 (T3), 4 (T4), and 5 (T5) million sperm per 0.25-mL dose in caprogen diluent. On d 0.25 (6 h postcollection), 1, 2, 3, 4, and 5 postcollection, viability, oxidative stress, and mitochondrial activity were assessed using flow cytometry and the fluorescent probes propidium iodide, CM-H2DCFDA, and rhodamine 123, respectively. On the same days, glucose consumption, total antioxidant capacity, and progressive linear motility were assessed. We observed an effect of day and treatment on sperm cell viability, with the highest percentage live found in T 0005 and the lowest in T 0025 on all days. Oxidative stress in live sperm increased with duration of storage and was affected by treatment, being highest in T 0025 and lowest in T 0005 on all days (d 5: 56.4±2.76% and 28.8±1.22%, respectively; mean ± SEM). Both the total antioxidant capacity and percentage of live sperm positive for rhodamine 123 were unaffected by treatment. The concentration of glucose in caprogen declined with time and was lowest in T 0025 and highest in T 0005 on d 5. In conclusion, higher concentrations of sperm have detrimental effects on sperm cell viability and increase oxidative stress but have no effect on the mitochondrial activity of sperm.

In vitro assessment of sperm from bulls of high and low field fertility

The aim of this study was to investigate the reasons for differences in field fertility of bulls following insemination with frozen-thawed semen. The study was carried out in two separate parts over two years and comparisons were made between 5 high and 4 low fertility Holstein Friesian bulls as determined by their either 90 day non-return rate (Year 1) or calving rate (Year 2). Two high fertility Limousin bulls were included in Year 1 for comparative purposes. The ability of sperm from each bull to penetrate artificial mucus was assessed (Year 1 = 7 replicates; Year 2 = 5 replicates). Glass capillary tubes (2 per bull per replicate) were filled with artificial mucus and incubated with sperm stained in 1% Hoechst 33342 for 30 min at 37 °C. The number of sperm were subsequently counted at 10 mm intervals along the tube between 40 and 80 mm markers. Sperm mitochondrial activity of each bull was assessed by the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assay (4 replicates in each year). Sperm were incubated with MTT for 1 h at 37 °C following which the absorbance of formazan was read using a spectrophotometer. Sperm viability after thawing was assessed for each bull using a live/dead sperm viability kit (Year 1 = 3 replicates; Year 2 = 4 replicates). A minimum of 250 cells were assessed per bull in each replicate and classified as either live or dead. Finally, the ability of sperm to fertilize oocytes in vitro and their ability to develop to blastocyst stage embryos were assessed (5 replicates in each year involving 220 to 306 oocytes per bull). Data transformation to normalize residuals was required for mucus sperm penetration (square root) and IVF (cleavage and blastocyst rate) results (arcsin). The mean number of sperm counted at each 10 mm mark between 40 and 80 mm was higher in the high fertility (56.0; 95% CI 39.5 to 75.3) compared to the low fertility (42.9; 95% CI 29.3 to 59.1) Holstein Friesian bulls but the difference did not reach formal significance (P = 0.09). Fertility status had no effect on the ability of sperm to reduce MTT to formazan (mean absorbance 0.34 ± 0.051 and 0.30 ± 0.044) or on the percentage of live sperm per straw (mean 47.3 ± 5.47 and 32.4 ± 4.66) for high and low fertility Holstein Friesian bulls respectively. Oocyte cleavage rate following insemination with sperm from high fertility Holstein Friesian bulls was significantly higher than with sperm from low fertility Holstein Friesian bulls [76.7% (95% CI 60.9 to 89.4) and 55.3 (95% CI 40.4 to 69.7) respectively, P = 0.04]. There was no significant effect of bull fertility on blastocyst rate [34.7% (95% CI 21.1 to 49.6) and 24.2 % (95% CI 14.1 to 36.0) for the high and low fertility Holstein Friesian bulls, respectively; P = 0.2]. In conclusion, sperm from high fertility bulls tended to be more effective in penetrating artificial mucus and to have an increased ability to fertilize oocytes in vitro; however, once fertilization occurred subsequent embryo development was not significantly affected by fertility status.