Obese outbred mice only partially benefit from diet normalization or calorie restriction as preconception care interventions to improve metabolic health and oocyte quality

STUDY QUESTION

Can diet normalization or a calorie-restricted diet for 2 or 4 weeks be used as a preconception care intervention (PCCI) in Western-type diet-induced obese Swiss mice to restore metabolic health and oocyte quality?

SUMMARY ANSWER

Metabolic health and oocyte developmental competence was already significantly improved in the calorie-restricted group after 2 weeks, while obese mice that underwent diet normalization showed improved metabolic health after 2 weeks and improved oocyte quality after 4 weeks.

WHAT IS KNOWN ALREADY

Maternal obesity is linked with reduced metabolic health and oocyte quality; therefore, infertile obese women are advised to lose weight before conception to increase pregnancy chances. However, as there are no univocal guidelines and the specific impact on oocyte quality is not known, strategically designed studies are needed to provide fundamental insights in the importance of the type and duration of the dietary weight loss strategy for preconception metabolic health and oocyte quality.

STUDY DESIGN, SIZE, DURATION

Outbred female Swiss mice were fed a control (CTRL) or high-fat/high-sugar (HF/HS) diet. After 7 weeks, some of the HF mice were put on two different PCCIs, resulting in four treatment groups: (i) only control diet for up to 11 weeks (CTRL_CTRL), (ii) only HF diet for up to 11 weeks (HF_HF), (iii) switch at 7 weeks from an HF to an ad libitum control diet (HF_CTRL) and (iv) switch at 7 weeks from an HF to a 30% calorie-restricted control diet (HF_CR) for 2 or 4 weeks. Metabolic health and oocyte quality were assessed at 2 and 4 weeks after the start of the intervention (n = 8 mice/treatment/time point).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Changes in body weight were recorded. To study the impact on metabolic health, serum insulin, glucose, triglycerides, total cholesterol and alanine aminotransferase concentrations were measured, and glucose tolerance and insulin sensitivity were analyzed at PCCI Weeks 2 and 4. The quality of in vivo matured oocytes was evaluated by assessing intracellular lipid droplet content, mitochondrial activity and localization of active mitochondria, mitochondrial ultrastructure, cumulus cell targeted gene expression and oocyte in vitro developmental competence.

MAIN RESULTS AND THE ROLE OF CHANCE

Significant negative effects of an HF/HS diet on metabolic health and oocyte quality were confirmed (P < 0.05). HF_CTRL mice already showed restored body weight, serum lipid profile and glucose tolerance, similar to the CTRL_CTRL group after only 2 weeks of PCCI (P < 0.05 compared with HF_HF) while insulin sensitivity was not improved. Oocyte lipid droplet volume was reduced at PCCI Week 2 (P < 0.05 compared with HF_HF), while mitochondrial localization and activity were still aberrant. At PCCI Week 4, oocytes from HF_CTRL mice displayed significantly fewer mitochondrial ultrastructural abnormalities and improved mitochondrial activity (P < 0.05), while lipid content was again elevated. The in vitro developmental capacity of the oocytes was improved but did not reach the levels of the CTRL_CTRL mice. HF_CR mice completely restored cholesterol concentrations and insulin sensitivity already after 2 weeks. Other metabolic health parameters were only restored after 4 weeks of intervention with clear signs of fasting hypoglycemia. Although all mitochondrial parameters in HF_CR oocytes stayed aberrant, oocyte developmental competence in vitro was completely restored already after 2 weeks of intervention.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

In this study, we applied a relevant HF/HS Western-type diet to induce obesity in an outbred mouse model. Nevertheless, physiological differences should be considered when translating these results to the human setting. However, the in-depth study and follow-up of the metabolic health changes together with the strategic implementation of specific PCCI intervals (2 and 4 weeks) related to the duration of the mouse folliculogenesis (3 weeks), should aid in the extrapolation of our findings to the human setting.

WIDER IMPLICATIONS OF THE FINDINGS

Our study results with a specific focus on oocyte quality provide important fundamental insights to be considered when developing preconception care guidelines for obese metabolically compromised women wishing to become pregnant.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Flemish Research Fund (FWO-SB grant 1S25020N and FWO project G038619N). The authors declare there are no conflicts of interest.

O-155 Dietary caloric normalization or restriction as preconception care strategies: impact on oocyte developmental competence and quality in high fat/high sugar-induced obese outbred mice

Study question

Can diet normalization or caloric restriction (CR) for two weeks be used as a preconception care intervention in obese Swiss mice to restore oocyte development and quality

Summary answer

Diet normalization or CR as short-term preconception care interventions in obese mice only partially restored oocyte quality but did improve overall developmental competence.

What is known already

Maternal metabolic disorders like obesity and metabolic syndrome may result in decreased oocyte and embryo quality, and thus reproductive failure. Overweight and obese patients are advised to lose weight before conception to increase the chance of a healthy pregnancy. However, as human studies show no univocal guidelines, more fundamental research might provide additional answers. In order to avoid interference with increased maternal age, the question remains if oocyte quality can be restored after only a short preconception care intervention (PCCI).

Study design, size, duration

Outbred mice were fed a control (CTRL) or high-fat/high-sugar (HF) diet for seven weeks. Afterwards, HF-mice were put on different PCCIs for two weeks, resulting in four treatment groups: control diet (9w; CTRL_CTRL), HF diet (9w; HF_HF), switch from HF (7w) to an ad libitum control diet for 2w (HF_CTRL) or to a 30% CR diet for 2w (HF_CR). Oocyte developmental competence (n = 357) and quality (12-16 oocytes /treatment, scored blinded) were determined, using 6-8 mice/treatment.

Participants/materials, setting, methods

Body weight changes were recorded. In vivo matured oocytes were collected after superovulation and analysed for quality or in vitro fertilized and cultured. Oocyte quality was determined by staining for lipid content (Bodipy) and mitochondrial inner membrane potential and active mitochondria localization (JC-1). Oocyte developmental competence [cleavage (24h p.i.) and blastocyst rates (5 days p.i.)] was scored. Categorical and numerical data were analysed using binary logistic regression and ANOVA, respectively and corrected for multiple testing.

Main results and the role of chance

Compared to the CTRL group, HF diet increased body weight after 7 weeks by 24.19% (P &lt; 0.001). After the start of the PCCI, both HF_CTRL and HF_CR mice progressively lost weight and reached values similar to control mice after two weeks. HF_HF diet increased the intracellular lipid content in oocytes with 54.3% compared to the CTRL_CTRL group (P &lt; 0.05). This increased content was (partially) normalized in both preconception care intervention groups, even similar to the control levels in the HF_CTRL group. Both HF_HF and HF_CR oocytes showed a tendency to an increased ratio of active/total mitochondria when compared to the CTRL_CTRL group (P = 0.081, P = 0.083 respectively). In addition, active oocyte mitochondria in the HF_HF group were less pericortically distributed compared to controls. This was also the case in both preconception care intervention groups (P &lt; 0.05). After two weeks of PCCI, oocytes from HF_HF mice displayed lower cleavage rates than those from CTRL_CTRL mice (36.26% vs. 64.52%, P &lt; 0.05) but blastocyst rates (26.37% vs. 35.48%, P &gt; 0.1) were not different. HF_CR, but not HF_CTRL, oocytes showed higher cleavage rates (68.48%, P &lt; 0.001) compared with HF_HF oocytes. Moreover, both HF_CTRL (44.64%, P &lt; 0.05) and HF_CR (59.78%, P &lt; 0.001) oocytes showed improved blastocyst rates when compared to the HF_HF group (26.37%).

Limitations, reasons for caution

Although using a mouse model has several advantages, translating these results to the human setting is a limitation of this study. However, to improve this translatability, an outbred mouse model was used. Additional data will be collected to gain more information regarding the best preconception care intervention advice.

Wider implications of the findings

This research aims to provide fundamental insights in order to be able to formulate clear preconception guidelines to obese women planning for pregnancy. In addition, we aim to find the shortest possible intervention period to improve fertility.

Trial registration number

Not applicable

Altered embryotrophic capacities of the bovine oviduct under elevated free fatty acid conditions: an in vitro embryo--oviduct co-culture model

Maternal metabolic stress conditions are of growing importance in both human and dairy cattle settings as they can have significant repercussions on fertility. Upregulated lipolysis is a common trait associated with metabolic disorders and results in systemically elevated concentrations of non-esterified fatty acids (NEFAs). The effects of high NEFA concentrations on the follicular environment, oocyte and embryo development is well documented. However, knowledge on the effects of NEFAs within the oviduct, representing the initial embryonic growth environment, is currently lacking. Therefore, the experiments outlined here were designed to obtain fundamental insights into both the direct and indirect interactions between NEFAs, bovine oviductal cells and developing zygotes. Hence, zygotes were co-cultured with NEFA-pre-exposed bovine oviductal cells or subjected to simultaneous NEFA exposure during the co-culture period. The outcome parameters assessed were embryo development with cleavage (48h post insemination (pi)), morula (120-126h pi) and blastocyst (192h pi) rates, as well as morula intracellular lipid content and blastocyst quality using Bodipy and differential staining respectively. Our data suggest a direct embryotoxicity of NEFAs as well as impaired embryo development through a reduced oviductal ability to support and protect early embryo development.

β-carotene and vitamin E in the dairy industry: blood levels and influencing factors – a case study in Flanders

In this case study performed in Flemish dairy herds, it is shown that lactation stage, farm type (grazing (fresh grass) or zero-grazing) and season are interrelated factors associated with circulating β-carotene (bC) and Vitamin E (VitE) concentrations. The iCheck bC is an easy applicable cow-side test to evaluate a cow’s bC status. One third of the dairy cows in the study had deficiencies in circulating bC and VitE, especially cows in early lactation and cows from zerograzing farms. Fresh grass in the diet could not resolve the early post-partum decline in plasma bC and VitE. However, the bC and VitE statuses of dry cows were significantly better on grazing farms. These findings can help updating antioxidant recommendations since it is clear that there is a need for optimization of antioxidant nutritional management in the Flemish dairy industry in order to feed for optimal dairy cow health.

65 Improvement of bovine early embryo development in vitro by coculture with endometrial epithelial cells

We optimized a bovine endometrial epithelial cell (BEEC) line as a valuable research model for the study of very early embryo-maternal interactions in vitro. In this study, we aimed to (1) characterise the BEEC monolayers along the primary culture and first passages with respect to the expression of epithelial and mesenchymal cell markers and abundance of functional key transcripts; (2) to test whether direct or indirect contact with endometrial cells alter the quality of the embryos in vitro; and (3) to test the specificity of the effect. In Exp. 1, after isolation from slaughterhouse uteri at the early luteal phase, BEEC were cultured in DMEM/F12 phenol red-free medium supplemented with 10% fetal bovine serum (FBS) from primary culture until subculture 3. Fixed samples were immunostained for cytokeratin and vimentin. Transcript abundances for cellular lineage markers (KRT18 and VIM), oestrogen receptor (ESR1), interferon α/beta receptor 1 (IFNAR1), and prostaglandin G/H synthase 1 (PTGS1) and 2 (PTGS2) were evaluated by real-time quantitative PCR. Statistical analyses were carried out by ANOVA and Tukey test. Immunofluorescence data revealed that the BEEC line co-expresses cytokeratin together with a mesenchymal marker (Vimentin). This indicates that these epithelial cells underwent an epithelial-mesenchymal transition in vitro. Gene expression data showed a 6-fold increased (P&lt;0.001) abundance of VIM mRNA from the primary culture to the subculture 1, which remained constant until subculture 3; however, KRT18, ESR1, IFNAR1, PTGS1, and PTGS2 were similar between the passages, suggesting that the cells conserved their functional characteristics. In Exp. 2, groups of 15 morulas (Day 5.5) were cultured in SOF medium supplemented with 5% FBS in the absence (control) or in the presence (co-culture) of BEEC at passage 2, for 48h. Embryos were placed on direct or indirect contact with a BEEC monolayer using a 96-well insert containing 8μm pores. Developmental rates were compared by chi-square test and P-values were adjusted by Tukey’s test. The percentage of embryos that had developed from morula into blastocyst stage on Day 7.5 was significantly higher in the direct and indirect contact co-culture (65%; P&lt;0.05) groups compared with the control (53%) group. Moreover, 63% of the blastocysts were expanded, hatching, or hatched in the co-culture groups, whereas a rate of 46% was found in the control counterparts (P&lt;0.05). In Exp. 3, the same experimental conditions from Exp. 2 were used, but groups of 15 Day 5.5 morulas were cultured in control, or conditioned medium from BEEC (CondBEEC) or bovine fibroblasts (CondFib). Blastocyst development rate on Day 7.5 was higher in the CondBEEC group (71%; P&lt;0.001) compared with the control (54%) and CondFib (50%) groups. In conclusion, based on the markers studied, BEEC monolayers undergo epithelial-mesenchymal transition in vitro but preserve functional characteristics after few passages. The co-culture system improves bovine embryonic development from morula into blastocyst stage. This support is BEEC specific and does not rely on a direct cell-to-embryo contact.

166 Mitochondrial stress responses in bovine cumulus cells and oocytes matured under lipotoxic conditions: a proteomic insight

Obesity and up-regulated lipolysis are commonly associated with increased free fatty acid (FFA) concentrations, predominantly palmitic acid (PA), in blood and ovarian follicular fluid, which have been strongly linked with reduced oocyte quality. Mitochondria are known to play a central role in regulating cellular stress responses to lipotoxicity, which is well described in somatic cells. Although mitochondrial functions in oocytes are crucial for developmental competence, their stress response capacity has not been clearly described. Networking with endoplasmic reticulum unfolded protein responses (UPR) and protein translation may be different in oocytes than in somatic cells. Understanding these mechanisms is important to develop treatments. The aim of this study was to compare PA-induced stress responses in oocytes to those in cumulus cells (CC). We exposed bovine cumulus-oocyte complexes (COC) to pathophysiological PA concentration (150 µM) or solvent during in vitro maturation (24h) as a model. Then, the CC were separated from the oocytes (from pools of 120 COC per treatment per replicate, 3 replicates), and their proteomic profiles were examined using shotgun proteomic analysis with tandem mass tags. Functional analysis of the differentially regulated proteins (DRP; P&lt;0.05, fold change &gt;10%, false discovery rate &lt;5%) was done using Ingenuity® Pathway Analysis (IPA®; Qiagen, Valencia, CA, USA). A total of 1843 and 1275 proteins were identified in CC and oocytes, respectively, of which 86 and 54 were differentially regulated by PA. In CC, 20/86 proteins were mitochondrial, 16 of which were down-regulated. Canonical pathway analysis in CC showed that pro-apoptotic UPR, mitochondrial dysfunction, and other related redox regulatory, metabolic, and apoptotic pathways were the most affected. In the enclosed oocytes, 12/54 proteins were mitochondrial, 8 of which were up-regulated. Functional analysis of the DRP in oocytes suggests that pro-survival mechanisms were predominant. Mitochondrion-specific H2O2-scavenging enzyme (peroxiredoxin-3), mitochondrial trifunctional protein (HADHB), heat shock protein A8 (HSPA8), as well as the NRF2-mediated oxidative stress response, among others, were key regulatory mechanisms induced by PA in the oocytes. However, an increase in the relative abundance of cytochrome C was evident, which may trigger apoptosis. This was accompanied by up-regulation of SLC24A5, which negatively regulates mitochondrial outer membrane permeabilization and may prevent such apoptotic trigger. These data show that the mitochondria in oocytes, despite being structurally immature, regulate adaptive signalling pathways in response to metabolic stress. Although the proteomic changes in oocytes were predominantly anti-apoptotic, certain defective pro-apoptotic changes were identified. These data provide a unique insight into the mitochondrial adaptive signalling pathways in metabolically compromised oocytes, and indicate specific mitochondrial target pathways through which the developmental capacity of metabolically compromised oocytes can be improved or protected.

Differential effects of high and low glucose concentrations during lipolysis-like conditions on bovine in vitro oocyte quality, metabolism and subsequent embryo development

Lipolytic metabolic conditions are traditionally associated with elevated non-esterified fatty acid (NEFA) concentrations, but may also be accompanied by hyperglycaemia in obesity or by hypoglycaemia during a negative energy balance status. Elevated NEFA concentrations disrupt oocyte and embryo development and quality, but little is known about whether the effects of lipolytic conditions on oocyte developmental competence are modulated by glucose availability. To answer this, bovine cumulus-oocyte complexes (COCs) were matured under different conditions: physiological NEFA (72µM) and normal glucose (5.5mM), pathophysiologically high NEFA (420µM) and normal glucose, high NEFA and high glucose (9.9mM), high NEFA and low glucose (2.8mM). Developmental potential, cumulus expansion and metabolism of COCs exposed to high NEFA and low glucose were affected to a greater extent compared with COCs matured under high NEFA and high glucose conditions. High NEFA and high glucose conditions caused a moderate increase in oocyte reactive oxygen species compared with their high NEFA and low glucose or control counterparts. Blastocyst metabolism and the transcriptome of metabolic and oxidative stress-related genes were not affected. However, both lipolytic conditions associated with hyper- or hypoglycaemia led to surviving embryos of reduced quality with regards to apoptosis and blastomere allocation.

The effect of elevated non-esterified fatty acid concentrations on bovine spermatozoa and on oocyte in vitro fertilisation

Elevated non-esterified fatty acid (NEFA) concentrations, present in follicular and oviductal fluid, have been postulated as a causative link between metabolic disorders and subfertility. High NEFA conditions can directly disrupt oocyte maturation and developmental capacity after fertilisation. However, their influence on sperm function and the fertilisation process is not known. This study investigated the fertilisation process under high NEFA conditions. To differentiate between effects on both spermatozoa and oocytes or on spermatozoa only, different experiments were conducted. In the first experiment both gametes were simultaneously incubated during IVF under different conditions: (1) NEFA-free, solvent-free control conditions, (2) solvent control, (3) physiological concentrations of oleic (OA), palmitic (PA) and stearic (SA) acids or (4) pathophysiological concentrations of OA, PA and SA. In the second experiment spermatozoa were incubated (4 h) under the same treatment conditions prior to routine IVF. Gamete co-incubation resulted in reduced fertilisation and cleavage rates and increased prevalence of polyspermy. In the second experiment embryo developmental capacity and quality were not affected, although sperm motility and plasma membrane integrity were decreased. In conclusion, lipolytic conditions affected the fertilisation process mainly through an effect on the oocyte. Spermatozoa were still able to fertilise even though these conditions reduced sperm function.

Maternal metabolic stress may affect oviduct gatekeeper function

We hypothesized that elevated non-esterified fatty acids (NEFA) modify in vitro bovine oviduct epithelial cell (BOEC) metabolism and barrier function. Hereto, BOECs were studied in a polarized system with 24-h treatments at Day 9: (1) control (0 µM NEFA + 0% EtOH), (2) solvent control (0 µM NEFA + 0.45% EtOH), (3) basal NEFA (720 µM NEFA + 0.45% EtOH in the basal compartment) and (4) apical NEFA (720 µM NEFA + 0.45% EtOH in the apical compartment). FITC-albumin was used for monolayer permeability assessment and related to transepithelial electric resistance (TER). Fatty acid (FA), glucose, lactate and pyruvate concentrations were measured in spent medium. Intracellular lipid droplets (LD) and FA uptake were studied using Bodipy 493/503 and immunolabelling of FA transporters (FAT/CD36, FABP3 and CAV1). BOEC-mRNA was retrieved for qRT-PCR. Results revealed that apical NEFA reduced relative TER increase (46.85%) during treatment and increased FITC-albumin flux (27.59%) compared to other treatments. In basal NEFA, FAs were transferred to the apical compartment as free FAs: mostly palmitic and oleic acid increased respectively 56.0 and 33.5% of initial FA concentrations. Apical NEFA allowed no FA transfer, but induced LD accumulation and upregulated FA transporter expression (↑CD36, ↑FABP3 and ↑CAV1). Gene expression in apical NEFA indicated increased anti-apoptotic (↑BCL2) and anti-oxidative (↑SOD1) capacity, upregulated lipid metabolism (↑CPT1, ↑ACSL1 and ↓ACACA) and FA uptake (↑CAV1). All treatments had similar carbohydrate metabolism and oviduct function-specific gene expression (OVGP1, ESR1 and FOXJ1). Overall, elevated NEFAs affected BOEC metabolism and barrier function differently depending on NEFA exposure side. Data substantiate the concept of the oviduct as a gatekeeper that may actively alter early embryonic developmental conditions.

Exposure of bovine oocytes and embryos to elevated non-esterified fatty acid concentrations: integration of epigenetic and transcriptomic signatures in resultant blastocysts

Background

Metabolic stress associated with negative energy balance in high producing dairy cattle and obesity in women is a risk factor for decreased fertility. Non-esterified fatty acids (NEFA) are involved in this pathogenesis as they jeopardize oocyte and embryo development. Growing evidence indicates that maternal metabolic disorders can disturb epigenetic programming, such as DNA methylation, in the offspring. Oocyte maturation and early embryo development coincide with methylation changes and both are sensitive to adverse environments. Therefore, we investigated whether elevated NEFA concentrations affect establishment and maintenance of DNA methylation in oocytes and embryos, subsequently altering transcriptomic profiles and developmental competence of resultant blastocysts.

Results

Bovine oocytes and embryos were exposed to different NEFA concentrations in separate experiments. In the first experiment, oocytes were matured in vitro for 24 h in medium containing: 1) physiological (“BASAL”) concentrations of oleic (OA), palmitic (PA) and stearic (SA) acid or 2) pathophysiological (“HIGH COMBI”) concentrations of OA, PA and SA. In the second experiment, zygotes were cultivated in vitro for 6.5 days under BASAL or HIGH COMBI conditions. Developmental competence was evaluated by assessing cleavage and blastocyst rate. Overall gene expression and DNA methylation of resultant blastocysts were analyzed using microarray. DNA methylation data were re-evaluated by pyrosequencing. HIGH COMBI-exposed oocytes and embryos displayed a lower competence to develop into blastocysts compared to BASAL-exposed counterparts (19.3% compared to 23.2% and 18.2% compared to 25.3%, respectively) (P < 0.05). HIGH COMBI-exposed oocytes and embryos resulted in blastocysts with altered DNA methylation and transcriptomic fingerprints, compared to BASAL-exposed counterparts. Differences in gene expression and methylation were more pronounced after exposure during culture compared to maturation suggesting that zygotes are more susceptible to adverse environments. Main gene networks affected were related to lipid and carbohydrate metabolism, cell death, immune response and metabolic disorders.

Conclusions

Overall, high variation in methylation between blastocysts made it difficult to draw conclusions concerning methylation of individual genes, although a clear overview of affected pathways was obtained. This may offer clues regarding the high rate of embryonic loss and metabolic diseases during later life observed in offspring from mothers displaying lipolytic disorders.

‘Le jumart’: myth or mystery in animal reproduction?

There was a time when science still had to ‘hatch’. An era during which man often extrapolated existing knowledge to a level beyond reality. That period is not as far behind us as we would like to believe. Breeding of animals has always stimulated man’s fantasy. Out of this, a very interesting myth - or is it a mystery? - was born: the existence of a hybrid between horse and cow, ‘Le Jumart’. On top of the very well-known hybrids between horses and donkeys, the French ‘capitaine des haras’ Francois Alexandre de Garsault (1692-1778) describes the procedure of how to create a hybrid between a cow and a horse in his widespread and well known ‘Nouveau Parfait Maréchal’, first published in 1741. In depth research showed that he was far from being the only one who believed in the existence of such a crossover species. Other well-respected contemporary scientists even dedicate chapters in their textbooks on this animal, such as the French naturalist and medical doctor Jean-Pierre Buchoz (1731-1807) in his ‘Traité Economique et Physique de Gros Menu Bétail’ published in 1778. Even opinion leaders Charles Bonnet (1720-1793) and Lazzarro Spallanzani (1729-99) were convinced that these animals really roamed around in France during the 18th century. Finally, even the founder of the first ‘Ecole Vétérinaire’ in the world, Claude Bourgelat (1712-1779) testified in a letter to Bonnet to have admired the product of a stallion and a cow with his own eyes. Fortunately, the debate could count on important disbelievers as well, with Albrecht von Haller taking the lead by publishing a paper in the ‘Supplément à l’Encyclopédie ou Dictionnaire Raisonné des Sciences, des Arts et Métiers’ (1777), in which he calls the existence of the Jumart a ‘fable’. It would take another century for André Suchetet (1849-1910) to publish an ‘Extrait des Mémoires de la Société Zoologique de France’ with the title ‘La Fable des Jumarts’ (1889). Extremely interested in hybridization, this 19th century politician and member of several scientific societies, faces the challenge to finally steer the scientific community to a general conclusion on this enigma. This paper describes in a chronological order the rise and fall of one of the most intriguing ‘fabula’ in reproductive medicine and how it took emerging modern science about 200 years to decide on ‘myth’ or ‘mystery’.

The effect of a negative energy balance status on β-carotene availability in serum and follicular fluid of nonlactating dairy cows

Maternal metabolic pressure due to a cow's negative energy balance (NEB) has a negative effect on oocyte quality as a result of increased oxidative stress. In this study, we hypothesized that a NEB status may negatively affect the availability of β-carotene (bC, an antioxidant) in the micro-environment of the oocyte or follicular fluid (FF) and that daily bC supplementation can increase bC availability. We aimed to (1) determine the effect of a nutritionally induced NEB on bC concentrations in serum and FF as well as on the presence of bC metabolites, oxidative stress levels, and follicular growth in a nonlactating dairy cow model, and (2) investigate how this effect could be altered by dietary bC supplementation. Six multiparous nonlactating Holstein Friesian cows were subjected to 4 consecutive dietary treatments, 28 d each: (1) 1.2 × maintenance (M) or positive energy balance (PEB) without bC supplement (PEB-bC), (2) 1.2 × M with daily supplement of 2,000mg of bC comparable to the level of bC intake at grazing (PEB+bC), (3) 0.6 × M with 2,000mg of bC (NEB+bC), and (4) 0.6 × M (NEB-bC). At the end of each treatment, estrous cycles were synchronized and blood and FF of the largest follicle were sampled and analyzed for bC, retinol, α-tocopherol, free fatty acids, estradiol, and progesterone. Serum cholesterol, triglycerides, urea, insulin growth factor 1, growth hormone, total antioxidant status (TAS), and red blood cell glutathione (GSH) concentrations were determined as well. All cows lost body weight during both energy restriction periods and showed increased serum free fatty acid concentrations, illustrating a NEB. A dietary induced NEB reduced FF bC, but not plasma bC or plasma and FF retinol concentrations. However, bC and retinol concentrations drastically increased in both fluid compartments after bC supplementation. Follicular diameter was increased in supplemented PEB cows. Energy restriction reduced the TAS and red blood cell GSH, whereas daily bC supplementation could restore GSH concentrations, but not the TAS, to levels present in healthy PEB cows. In conclusion, daily bC supplementation can substantially improve bC and retinol availability in the oocyte's micro-environment, irrespective of the energy balance, which may affect follicular development and oocyte quality in the presence of maternal metabolic stress. This knowledge can be of importance to optimize nutritional strategies in the dairy industry to feed for optimal oocyte quality and fertility.

De Maréchal-Vétérinaire in de Grande Armée van Napoleon (1805-1815)

Op 18 juli 2015 was het precies tweehonderd jaar geleden dat Napoleon met zijn Grande Armée werd verslagen door de geallieerde strijdkrachten in wat de geschiedenis zou ingaan als de Slag bij Waterloo. Tijdens de tien jaar die aan deze nederlaag voorafgingen, bouwde de Franse keizer een gigantische troepenmacht uit waarin de bereden component of cavalerie een zeer belangrijke rol speelde. Omdat de paarden die hierin figureerden eerder al het onderwerp waren van een publicatie in dit tijdschrift, richt dit artikel specifiek de aandacht op de militaire veeartsen die als paardenarts instonden voor de verzorging van de honderdduizenden legerpaarden die tijdens het verloop van het keizerrijk onder de wapens werden gebracht. Na een korte inleiding over het ontstaan van het veeartsenijkundig onderricht, wat hand in hand ging met de geboorte van de militaire veearts, wordt dieper ingegaan op zijn rekrutering, statuut en werkomgeving. Hierbij wordt de rol van de keizer zelf beschreven met een bespreking van het decreet van Moskou dat voor het veeartsenijkundig onderwijs van zeer groot belang is geweest. Tenslotte worden de werkomstandigheden van de militaire veeartsen belicht aan de hand van enkele ooggetuigenverslagen.

Interaction between differential gene expression profile and phenotype in bovine blastocysts originating from oocytes exposed to elevated non-esterified fatty acid concentrations

Maternal metabolic disorders linked to lipolysis are major risk factors for reproductive failure. A notable feature of such disorders is increased non-esterified fatty acid (NEFA) concentrations in the blood, which are reflected in the ovarian follicular fluid. Elevated NEFA concentrations impact on the maturing oocyte and even alter subsequent embryo physiology. The aetiological mechanisms have not been fully elucidated. Therefore, in the present study, bovine in vitro maturing cumulus-oocyte complexes were exposed (24 h) to three different maturation treatments containing: (1) physiological (72 µM) NEFA concentrations (=control); (2) elevated (75 µM) stearic acid (SA) concentrations (=HIGH SA); and (3) elevated (425 µM) NEFA concentrations (=HIGH COMBI). Zygotes were fertilised and cultured following standard procedures. Transcriptomic analyses in resulting Day 7.5 blastocysts revealed that the major pathways affected are related to lipid and carbohydrate metabolism in HIGH COMBI embryos and to lipid metabolism and cell death in HIGH SA embryos. Furthermore, lower glutathione content and a reduced number of lipid droplets per cell were observed in HIGH SA-exposed oocytes and resulting morulae, respectively, compared with their HIGH COMBI-exposed counterparts. Vitrified embryos originating from HIGH SA-exposed oocytes tended to exhibit lower survival rates compared with controls. These data suggest possible mechanisms explaining why females across species suffering lipolytic disorders experience difficulties in conceiving.

Aderlatingen en etterdrachten verdrijven het ‘kwaad’ uit het lichaam

Eeuwenlang was bloed aflaten via een snede in de aders (flebotomie, aderlating) ontzettend populair in de geneeskunde van mens en dier. Naast het meest gebruikelijke ‘slaan van bloed’ in de halsader van paard en rund werd ook bloed afgelaten op diverse andere plaatsen, gaande van het gehemelte tot de staart. Behalve veneus bloed werd soms ook arterieel bloed afgetapt. In de humane geneeskunde was ook het kunstmatig verwekken van lokale capillaire bloedingen populair. Dit gebeurde met behulp van Hirudo (echels, bloedzuigers) en met zogenaamde ‘laatkoppen’ (vacuüm trekkende bokaaltjes op de huid). Het hoofddoel van al deze praktijken was zowel voor het volk als voor de artsen duidelijk: ziekteverwekkende stoffen (het ‘kwaad’) uit het lichaam laten ontsnappen. In de Hippocratisch-Galenische geneeskunde werd dit ingebed in theorieën over evenwicht (syncrasie) en onevenwicht (dyscrasie) van de verschillende lichaamsvochten (“humores”), waar mogelijk ook de verklaring lag voor de soms moeilijk toepasbare, lokale bloedafnamen dichtbij aangetaste lichaamsdelen. Een tweede, vooral in de diergeneeskunde ooit zeer belangrijke techniek bestond er in met behulp van de zogenaamde etterdrachten of andere irriterende middelen kunstmatig lokale ontstekingen op te wekken. Hoewel de gelijkenis met aderlaten niet evident is, berust het geloof in de heilzame werking van deze ingreep op het zelfde hoofdprincipe: de ziekteverwekkende stof, het ‘kwaad’, moet uit het lichaam verdreven worden.

128 ADDING SERUM OF COWS SUPPLEMENTED WITH β-CAROTENE DURING BOVINE IN VITRO EMBRYO CULTURE HAS NO EFFECT ON EMBRYO DEVELOPMENT

Elevated serum NEFA concentrations, typically present in negative energy balance (NEB) cows, are known to compromise bovine in vitro oocyte and embryo quality and developmental competence. These observations seem to be associated with oxidative stress. Therefore, antioxidant supplementation such as β-carotene (bC) can be a promising solution to ameliorate embryo quality and survival. However, little is known about the possible neutralizing effect of bC on NEB-compromised embryos. Accordingly, we hypothesise that bC can overcome the potential negative effects of metabolic conditions associated with NEB on embryo development. To investigate this we aimed to evaluate the effect of serum from bC-supplemented positive energy balance (PEB) or NEB cows on embryonic developmental competence. A total of 5 nonlactating Holstein-Friesian cows were subjected to 4 consecutive dietary treatments, 28 days each: 1) 1.2 × maintenance (M) (= PEB–bC), 2) 1.2 × M with daily 2000 mg of bC (Rovimix 10% bC, DSM) (= PEB+bC), 3) 0.6 × M + bC (= NEB+bC), and 4) after a 6 week acclimatization period 0.6 × M (= NEB–bC). Serum was collected 72 h after ovulation, pooled per dietary treatment, and heat inactivated during 30 min at 56°C. In total 1404 bovine slaughterhouse grade 1 cumulus-oocyte complexes were serum-free matured (4 repeats), routinely fertilized, and cultivated for 6.7 days with the addition of 10% serum of the 4 different treatments. Cleavage (48 h post-insemination), blastocyst rates (7.7 days post-insemination), and the rates of blastocysts from cleaved zygotes were calculated. Developmental competence data were compared between the 4 treatments using a binary logistic regression model taking replicate, treatment, and the interaction of both factors into account. The NEFA and bC data were analysed using a paired-samples t-test (IBM SPSS Statistics 20). Bonferroni correction was applied. Serum NEFA concentrations were significantly elevated in NEB compared to PEB (0.36 ± 0.18 mM v. 0.21 ± 0.11 mM; P = 0.011). β-Carotene supplementation drastically increased bC concentrations in serum in NEB (0.44 ± 0.18 μg mL–1 v. 3.28 ± 0.78 μg mL–1; P < 0.001) as well as in PEB (1.02 ± 0.91 μg mL–1 v. 3.04 ± 1.28 μg mL–1; P < 0.001). Unexpectedly no significant differences were found on cleavage rates (on average 81%), subsequent development until blastocyst stage (on average 29%), or blastocyst rates from cleaved zygotes (on average 36%). Briefly, our model was not able to indicate any negative effect of NEB serum on in vitro embryo development compared with PEB, and hence no extra beneficial effects of bC could be observed on the outcome. In conclusion, these data show that more research is needed to optimize this model to investigate the effect of specific dietary strategies on pre-implantation embryo quality.

2 ELEVATED NONESTERIFIED FATTY ACID CONCENTRATIONS HAMPER IN VITRO BOVINE OVIDUCTAL EPITHELIAL CELL PHYSIOLOGY

Elevated nonesterified fatty acids (NEFA) have been recognised as an important link between lipolysis-based metabolic conditions and impaired fertility in high-yielding dairy cattle. However, NEFA effects on the oviductal micro-environment currently remain unknown. We hypothesise that elevated NEFAs may contribute to the complex pathology of subfertility and infertility by exerting a negative effect on bovine oviductal epithelial cell (BOEC) physiology. Therefore, the objectives of this study were to elucidate NEFA toxicity effects on BOEC, both qualitatively and morphologically, by assessing BOEC-sperm binding affinity, monolayer integrity, proliferation capacity and morphology. The BOEC of 4 bovine oviducts (4 replicates) at Day 3–5 of the oestrous cycle from a local slaughterhouse were mechanically isolated, pooled, and cultured in a polarized cell culture system (ThinCert, Greiner Bio-One, Frickenhausen, Germany) with DMEM/F12-based culture medium for 9 days until transepithelial electric resistance (TER) reached at least 700 Ω cm2 to prevent leakage between the 2 compartments. At Day 10, monolayers were exposed to a 720 µM NEFA mixture of OA, SA, and PA, for 24 h in 4 treatment groups according to exposure side: control, basal (B), apical (A), and A+B. The BOEC were washed and monolayer quality was assessed by means of a sperm binding assay (30 min co-culture of BOEC monolayer and 106 spermatozoa mL–1), TER measurements (pre- and post-exposure) and a wound healing assay (8-h observation of BOEC proliferation capacity after over an artificial gap). Morphology of BOEC was assessed by scanning electron microscopy on cell polarity, presence of microvilli and cilia, and monolayer integrity. Data (mean ± s.d.) were analysed by mixed model ANOVA. In A+B, monolayers (31.28 ± 6.16 sp/0.05 mm2) showed a significantly reduced sperm binding affinity compared to the control (97.90 ± 10.76 sp/0.05 mm2; P < 0.05), and treatment A tended to be more affected (39.95 ± 19.30 sp/0.05 mm2) than treatment B (68.55 ± 15.38 sp/0.05 mm2; P = 0.051). The absolute TER increase post-NEFA exposure in the control (110 ± 11 Ω cm2) was significantly higher than in all the other treatments. Also, the TER increase differed significantly depending on the exposure side: in treatment A (3 ± 6 Ω cm2), the TER increase was lower than in treatment B (29 ± 8 Ω cm2), and monolayers in treatment A+B were even associated with a significant TER reduction (–15 ± 10 Ω cm2; P < 0.05). Cell proliferation capacity showed a significant closure of the gap in all treatments, but only the control group (41.64% closure) differed significantly (P < 0.05) from the other groups (B = 28.3%, A = 31.62%, A+B = 30.9% closure) irrespective of the exposure side; BOEC morphology was not affected. Depending on the exposure side, elevated NEFA exert a negative effect on BOEC physiology but not morphology. Ultimately, these physiological alterations in its micro-environment may result in suboptimal development of the pre-implantation embryo and a reduced reproductive outcome.

186 THE EFFECT OF SHORT VERSUS LONG TERM ELEVATED NONESTERIFIED FATTY ACID CONCENTRATIONS DURING MURINE IN VITRO FOLLICLE GROWTH ON OOCYTE DEVELOPMENTAL COMPETENCE

Metabolic disorders, like obesity and type 2 diabetes are characterised by lipolysis-linked elevated nonesterified fatty acid (NEFA) concentrations. Exposure to high NEFA concentrations during the final phase of bovine in vitro oocyte maturation (24 h) impairs oocyte developmental competence and subsequent embryo quality. However, because elevated NEFA concentrations in vivo are often present for a longer period of time, our recent research focused on a more in vivo-like long-term NEFA exposure (12 d) of whole murine follicles in vitro. The model covers follicular growth from the early secondary to the antral stage in vitro, including final oocyte maturation after an ovulatory stimulus (OS). Results showed an altered follicular growth and physiology (steroid synthesis, gene expression) and a subsequent reduced oocyte developmental competence. However, it remains unclear what specific time frame in follicular development is the most sensitive to such metabolic insult. Therefore, we hypothesised that chronic elevated NEFA concentrations throughout follicle growth affect oocyte developmental competence more severely than short-term NEFA exposure limited to the final phase of oocyte maturation. The aim was to study the effect of elevated NEFA concentrations 1) during the final phase of follicular oocyte maturation (after the OS) and 2) during the whole period of in vitro murine follicle growth until the antral stage, including final oocyte maturation. Early secondary follicles, isolated from the ovaries of 13-day-old B6CBAF1 mice, were cultured in vitro until the antral stage (3 replicates). Follicles were exposed to: BASAL NEFA mix for 12 days (BASAL-BASAL, control); HIGH stearic acid (SA) for 12 days (SA-SA); HIGH NEFA mix for 12 days (NEFA-NEFA); HIGH SA after the OS (BASAL-SA); and HIGH NEFA mix after the OS (BASAL-NEFA). Oocytes were isolated out of antral follicles 20 hours after the OS, routinely fertilized and presumptive zygotes cultured. Cleavage (n cleaved zygotes/n oocytes) and blastocyst (n blastocysts/n oocytes) rates were documented and analysed by means of binary logistic regression. Cleavage rate was reduced for BASAL-BASAL (37%) compared to BASAL-NEFA embryos (52%; P = 0.045). The BASAL-NEFA treatment (43%) presented with a higher blastocyst percentage than BASAL-BASAL (23%; P = 0.004), NEFA-NEFA (26%; P = 0.037) and SA-SA (15%; P = 0.001) treatments. The BASAL-SA (30%) treatment performed better than the SA-SA treatment (P = 0.049). Even though BASAL-BASAL (control) embryo development was surprisingly low, the results indicate that long-term NEFA exposure during follicle growth in vitro affects oocyte developmental competence more severely than an exposure limited to the final phase of maturation after the OS. The results thus emphasise that the maternal micro-environment throughout follicular growth and not only during final oocyte maturation is essential for optimal oocyte quality.

169 INVASION OF MURINE ANNEXIN A1 IN BOVINE OVARIAN CORTEX TISSUE DURING SHORT-TIME XENOTRANSPLANTATION IN CONVENTIONAL AND IMMUNE DEFICIENT MICE

In 2012, 6.7 million women worldwide were diagnosed with cancer, including young women and children. Almost 85% of the latter survive the disease. However, the necessary cytotoxic treatment reduces their reproductive potential by damaging the stock of, basically preantral, ovarian follicles. Current fertility preservation techniques try to overcome this problem. Still, the success rate is low due to a lack of optimization and standardization. Nowadays, culturing preantral follicles in vitro is not yet routinely possible. Therefore, we used an in vivo model based on xenotransplantation of bovine ovarian cortex tissue in recipient mice, as an alternative to studying human reproduction. To further characterise this model, we assessed the influence from the host on the graft at the protein level. Visualising murine annexin A1, an anti-inflammatory protein, in the transplanted bovine cortex tissue should help to elucidate the process of immunological rejection. Hereto its distribution around the present bovine follicles is measured. In total, 12 mice (6 conventional fluorescent C57BL/6-eGFP and 6 immune deficient Balb/c-Nu) were used as graft recipients. All mice were anesthetized with an intraperitoneal injection and subsequently sterilized. Small pieces (max. 9 mm3) of adult bovine ovarian cortex, retrieved from slaughterhouse ovaries, were grafted retroperitoneal. After a transplantation period of 14 (3 mice/mice strain) or 28 (3 mice/mice strain) days, the mice were killed and all grafts were successfully recovered. These were fixed (4% formaldehyde) and processed into histological paraffin slides. Murine annexin A1 (Sigma-Aldrich HPA011271) was localised using immunofluorescence through a rhodamine label (RITC filter). We measured the shortest distances between 10 annexin fluorescent signals and the basal membrane of each follicle, found in the graft. We calculated the average of these measurements, resulting in one data point per follicle. The dataset was fitted in a linear mixed model with annexin as dependent variable, and transplantation period and mice strain as fixed effects. Fluorescent signals of murine annexin A1 were found in all grafts form both mice strains, surrounding bovine follicles. Data show no interaction between mice strain and the duration of the transplantation period. The influence of the mice strain showed a trend towards significance (P = 0.08), possibly due to the immunological state of the host. To our knowledge, this is the first time an attempt has been made to characterise the host/donor interaction in xenografting procedures. We can conclude that annexin A1 from the murine host (whether immunodeficient or immunocompetent) invades the bovine graft tissue in a short period of time.

Effects of neutral red assisted viability assessment on the cryotolerance of isolated bovine preantral follicles

PURPOSE

Fertility preservation strategies warrant non-invasive viability assessment of preantral follicles (PAF) such as staining with Neutral Red (NR) that is incorporated by viable follicles. To optimize the procedure, we firstly determined the lowest concentration and shortest exposure time needed for optimal viability screening of isolated bovine PAF. Secondly, we combined this protocol to a vitrification procedure to assess cryotolerance of the stained follicles.

METHODS

Isolated PAF (900, divided over 6 replicates) were cultured in DMEM/Ham's F12 (Culture Medium - Cm) for 4 days (38.5 °C, 5% CO2). On D0, D2 and D4, follicles were stained, by adding NR medium (NRm = Cm with different concentrations NR) after which viability was assessed by counting stained/non-stained PAF every 30 min for a period of 2 h.

RESULTS

Following a binary logistic regression analysis with staining as a result (yes/no) versus log-concentration, a probability model could be fitted, indicating that the proportion of stained follicles remained stable after 30 min when 15 μg/ml NR was used, without compromising follicular health and viability. Consequently, using this protocol, no significant effect of staining prior to vitrification, was found on PAF viability immediately after warming or following 4 days of culture.

CONCLUSIONS

In conclusion, we propose NR staining as a non-invasive, non-detrimental viability assessment tool for PAF, when applied at 15 μg/ml for 30 min, being perfectly compatible with PAF vitrification.

De handbibliotheek van de eerste studenten diergeneeskunde (Frankrijk 18de eeuw)

In deel 1 van deze korte reeks over de beschikbare veeartsenijkundige kennis voor de eerste studenten diergeneeskunde werd beschreven hoe zij het vóór 1750 moesten stellen met enkele standaardwerken over het paard en de paardenhouderij. Omdat er nog geen geformaliseerde opleiding diergeneeskunde bestond, hoeft het ook geen verbazing te wekken dat de echte veterinaire handboeken nog niet voorhanden waren. In dit tweede deel wordt dieper ingegaan op de periode rond en kort na de oprichting van de eerste veeartsenijschool door Claude Bourgelat (Lyon, 1761). Ongeveer tien jaar eerder publiceerde hij een eerste belangrijk werk en tijdens dezelfde periode brak ook Philippe-Etienne Lafosse door met een aantal erg educatieve publicaties. Vanaf dat moment kan gesteld worden dat er een aantal handboeken ter beschikking kwamen waarin werd afgerekend met tal van volkse remedies en waardeloze therapieën. De tot dan toe algemeen aanvaarde inzichten en gebruiken maakten plaats voor een meer wetenschappelijke benadering van het paard en -weliswaar schoorvoetend- een aantal andere huisdieren, inclusief het rundvee en de kleine herkauwers. Dit alles kaderde in een tijdsgeest die zou uitmonden in de Franse Revolutie, een keerpunt dat mee aan de basis lag van een heuse kennisexplosie en de publicatie van honderden werken over landbouw- en veeartsenijkunde die stilaan tot echte wetenschappen uitgroeiden.

De handbibliotheek van de eerste studenten diergeneeskunde (Frankrijk 18de eeuw)

In deel 1 van deze korte reeks over de beschikbare veeartsenijkundige kennis voor de eerste studenten diergeneeskunde werd beschreven hoe zij het vóór 1750 moesten stellen met enkele standaardwerken over het paard en de paardenhouderij. Omdat er nog geen geformaliseerde opleiding diergeneeskunde bestond, hoeft het ook geen verbazing te wekken dat de echte veterinaire handboeken nog niet voorhanden waren. In dit tweede deel wordt dieper ingegaan op de periode rond en kort na de oprichting van de eerste veeartsenijschool door Claude Bourgelat (Lyon, 1761). Ongeveer tien jaar eerder publiceerde hij een eerste belangrijk werk en tijdens dezelfde periode brak ook Philippe-Etienne Lafosse door met een aantal erg educatieve publicaties. Vanaf dat moment kan gesteld worden dat er een aantal handboeken ter beschikking kwamen waarin werd afgerekend met tal van volkse remedies en waardeloze therapieën. De tot dan toe algemeen aanvaarde inzichten en gebruiken maakten plaats voor een meer wetenschappelijke benadering van het paard en -weliswaar schoorvoetend- een aantal andere huisdieren, inclusief het rundvee en de kleine herkauwers. Dit alles kaderde in een tijdsgeest die zou uitmonden in de Franse Revolutie, een keerpunt dat mee aan de basis lag van een heuse kennisexplosie en de publicatie van honderden werken over landbouw- en veeartsenijkunde die stilaan tot echte wetenschappen uitgroeiden.

Dietary fat supplementation and the consequences for oocyte and embryo quality: hype or significant benefit for dairy cow reproduction?

In many countries, fat supplementation in the diet has become common in the dairy industry. There are several ideas as to how dietary fat could influence reproductive performance. Saturated fatty acids, such as palm oil, can increase milk yield but may aggravate negative energy balance and thus may impair fertility when fed during the first week post-partum. However, priming the lipid oxidation in the liver by feeding saturated fats during the dry period has recently been shown to be a potentially promising strategy to mitigate fat mobilization and liver accumulation post-partum. Furthermore, polyunsaturated fats (omega-3 fatty acids and conjugated linoleic acids) are fed to reduce the 'de novo' fat synthesis in the udder and thus the milk fat content, which may be of modest benefit for overall energy balance. Furthermore, omega-6 and omega-3 polyunsaturated fatty acids are reported to alter follicular growth, steroid synthesis and prostaglandin metabolism in the ovary and endometrium, respectively. Omega-6 fatty acids are believed to have pro-inflammatory and thus PGF2α-stimulating properties rendering them extra value as 'nutraceutical' early post-partum, while omega-3 fatty acids can weaken this inflammatory potency, leading to a higher chance of survival of the embryo when supplemented during the periconceptual period. Unfortunately, research results rarely provide a consensus in this perspective. The consequences of these fat-feeding strategies on oocyte and embryo quality remain an intriguing issue for debate. Fat feeding may alter the microenvironment of the growing and maturing oocyte of the early and older embryo and thus may affect reproductive outcome. We recently reported that dietary-induced hyperlipidaemic conditions can be harmful for embryo development and metabolism. However, to date, research results remain somewhat conflicting most probably due to differences in fat sources used, in diet and duration of supplementation and in experimental set-up in general.

De handbibliotheek van de eerste studenten diergeneeskunde (Frankrijk, 18de eeuw)

De diergeneeskunde vindt zijn oorsprong in de klassieke oudheid. De kennis die destijds bij de oude Grieken en Romeinen was vergaard, bleef ter beschikking dankzij meerdere vertalingen en compilaties. Het toenemende belang van het paard leidde in de 16de en 17de eeuw tot een sterke stijging van de interesse en tot de publicatie van enkele meer wijdverbreide standaardwerken over het paard en de paardrijkunst. De meeste rijscholen en academiën die aan de oorsprong lagen van de eerste veeartsenijschool (Lyon, 1761), konden een aantal van deze publicaties ter beschikking stellen van hun leerlingen en/of waren voor hun docenten een belangrijke bron van informatie. Deze veelal luxueuze uitvoeringen bevatten behoorlijke beschrijvingen van visueel waarneembare structuren en hun afwijkingen. De onderliggende functionele of fysiologische kennis ontbrak echter nagenoeg volledig. Het bestaan van meer klassieke handboeken zoals we ze nu kennen, was mede door het ontbreken van een formele vorm van veeartsenijkundig onderwijs vóór 1750, onbestaande. Na een korte inleiding over de kennis van de veeartsenijkunde bij de Grieken en Romeinen, wordt in dit eerste deel kort de (vooral Franse) diergeneeskundige literatuur belicht tot aan de publicatie van één van de meest bekende werken uit die tijd, ‘Le Nouveau Parfait Maréchal’ van François Alexandre de Garsault (Frankrijk, eerste uitgave 1741).

85 THE EFFECT OF 17α-ETHINYL ESTRADIOL EXPOSURE OF IN VITRO-CULTURED BOVINE MORULAE ON SUBSEQUENT EMBRYONIC DEVELOPMENT AND QUALITY

Research has shown that 17-α-ethinyl oestradiol (EE2), an important component of most oral birth-control pills, acts as a xeno-oestrogen after being released into the environment through urine and feces. Although this emphasizes the need for the evaluation of its toxicity, several oocyte and embryo-toxic effects have been reported (Beker-Van Woudenberg et al. 2012). Therefore, the aim of the present study was to evaluate the effect of EE2 exposure during bovine early embryonic development, specifically at the morula stage (18 h), on subsequent embryonic development and quality. Bovine cumulus–oocyte complexes (COC) from 2- to 6-mm-diameter follicles were matured in groups of 50 in 500 μL of TCM with 20 ng mL–1 epidermal growth factor (EGF) for 24 h and subsequently fertilized in groups of 100 in 500 μL of fertilization medium for 22h (5% CO2, 38.5°C). Presumptive zygotes were denuded and cultured in groups of  ±25 in 50 μL of SOF with ITS (5 μg mL–1 insulin, 5 μg mL–1 transferrin, 5 ng mL–1 selenium) and 2% BSA, covered with mineral oil (5% O2, 5% CO2, 38.5°C). Subsequently, embryonic developmental stage was determined at 135 h post-insemination (p.i.). Sole embryos at morula stage were selected and randomly allocated to treatment groups (n) divided over 5 replicates: (1) Control (67), (2) solvent control: 0.1% ethanol (49), (3) 10 ng mL–1 EE2 (49), or (4) 10 μg mL–1 EE2 (63). The morulas were cultured individually in 30 μL of standard SOF medium supplemented with the desired concentrations ethanol or EE2 (5% O2, 5% CO2, 38.5°C) in 96-well half-area culture plates, without oil coverage for 18 h. Following exposure, embryos were cultured singly in standard culture medium for 2 more days. Subsequently, developmental competence was evaluated and blastocyst rates calculated (blastocyst rate = total blastocyst/number of grade 1 selected morula). Expanded (EB) and hatched blastocysts (HB) were fixed with 4% paraformaldehyde, and total cell number and apoptotic cell ratio were determined by DAPI and TUNEL staining (13 EB and 7 HB per treatment). Comparable blastocyst rates were obtained in all treatment groups: solvent control (77.8%), 10 ng mL–1 EE2 (69.0%), and 10 μg mL–1 EE2 (84.0%) compared with the controls (88.2%; P > 0.05; binary logistic regression). In addition, no significant effect of treatment could be found on total cell number or apoptotic cell ratio: solvent control (149.70 ± 23.47 and 3.46 ± 1.73), 10 ng mL–1 EE2 (154.75 ± 23.26 and 3.22 ± 1.35), and 10 μg mL–1 EE2 (150.50 ± 26.69 and 4.23 ± 1.85) compared with the controls (145.02 ± 24.71 and 3.07 ± 2.03; P > 0.05; two-way ANOVA). Although our results show no immediate statistical significant effect of short-term EE2 exposure during the morula stage in in vitro culture on subsequent blastocyst development and quality, additional research is necessary to find out if EE2 may affect gene-expression patterns, eventually resulting in still unknown embryotoxic effects that might turn up during later embryonic development.

84 THE EFFECT OF β-MERCAPTOETHANOL ON CLEAVAGE RATES, DEVELOPMENTAL COMPETENCE AND QUALITY OF IN VITRO PRODUCED BOVINE EMBRYOS

The production of excessive levels of reactive oxygen species can be a major problem during in vitro embryo culture. Although studies have shown that supplementation with exogenous antioxidants can improve embryo quality, the results are controversial among researchers. In this study, we examined the effects of different concentrations of β-mercaptoethanol (β-ME) added to the culture media, on cleavage rates, the quality and developmental competence of in vitro-produced bovine embryos. The embryos were produced in vitro as described previously (Van Hoeck et al., 2013). Briefly, in total, 753 grade I cumulus–oocyte complexes (COC) from 2- to 6-mm-diameter follicles were matured in groups of 50 in 500 μL of TCM with 20 ng mL–1 EGF for 24 h, fertilized in groups of 100 in 500 μL of fertilization medium for 20 h (5% CO2, 38.5°C). Presumptive zygotes were denuded and randomly assigned to 4 treatments with different concentrations of β-ME: 0 μM (control), 50 μM, 100 μM, and 150 μM. They were cultured in groups of  ±25 in 50 μL of SOF supplemented with ITS (10 μg mL–1 insulin; 5.5 μg mL–1 transferrin; 6.7 ng mL–1 selenium) and 2% BSA and covered with mineral oil (5% O2, 5% CO2, 38.5°C). At 48 h post-insemination (p.i.), cleavage rate was evaluated and expressed as the number of cleaved embryos on total number of oocytes. At Day 7 p.i., blastocyst rate was determined (number of blastocysts on total number of oocytes), blastocysts were fixed in 4% paraformaldehyde, and total cell number was determined by DAPI staining. Data were analysed by ANOVA and post hoc test. Comparable cleavage rates were obtained in treated groups: control (80.8%), 50 μM (77.7%), 100 μM (77.9%), and 150 μM (73.6%; P > 0.05). Also, no significant effect of treatment could be found on blastocyst rates: control (36%), 50 μM (36.5%), 100 μM (38.4%), and 150 μM (30.4%). The total cell number per blastocyst increased significantly (P < 0.05) using 100 μM of β-ME compared with the controls (158.0 ± 24.3 v. 123.2 ± 9.72, respectively). These results suggest that the inclusion of 100 μM β-ME during in vitro embryo culture could be used for production of high quality bovine blastocysts.

Oocyte developmental failure in response to elevated nonesterified fatty acid concentrations: mechanistic insights

Elevated plasma nonesterified fatty acid (NEFA) concentrations are associated with negative energy balance and metabolic disorders such as obesity and type II diabetes. Such increased plasma NEFA concentrations induce changes in the microenvironment of the ovarian follicle, which can compromise oocyte competence. Exposing oocytes to elevated NEFA concentrations during maturation affects the gene expression and phenotype of the subsequent embryo, notably prompting a disrupted oxidative metabolism. We hypothesized that these changes in the embryo are a consequence of modified energy metabolism in the oocyte. To investigate this, bovine cumulus oocyte complexes were matured under elevated NEFA conditions, and energy metabolism-related gene expression, mitochondrial function, and ultrastructure evaluated. It was found that expression of genes related to REDOX maintenance was modified in NEFA-exposed oocytes, cumulus cells, and resultant blastocysts. Moreover, the expression of genes related to fatty acid synthesis in embryos that developed from NEFA-exposed oocytes was upregulated. From a functional perspective, inhibition of fatty acid β-oxidation in maturing oocytes exposed to elevated NEFA concentrations restored developmental competence. There were no clear differences in mitochondrial morphology or oxygen consumption between treatments, although there was a trend for a higher mitochondrial membrane potential in zygotes derived from NEFA-exposed oocytes. These data show that the degree of mitochondrial fatty acid β-oxidation has a decisive impact on the development of NEFA-exposed oocytes. Furthermore, the gene expression data suggest that the resulting embryos adapt through altered metabolic strategies, which might explain the aberrant energy metabolism previously observed in these embryos originating from NEFA-exposed maturing oocytes.

94 A POLARIZED CELL-CULTURE SYSTEM TO STUDY THE EFFECTS OF ELEVATED SERUM NONESTERIFIED FATTY ACID CONCENTRATIONS ON THE BOVINE OVIDUCTAL MICROENVIRONMENT IN VITRO

The detrimental consequences of elevated serum nonesterified fatty acid concentrations (NEFA) typical in negative energy balance, obesity, or type II diabetes have previously been demonstrated in ovarian follicles. However, regardless its key role in reproduction, the consequences of elevated NEFA on oviductal physiology are unclear. Therefore, the aim of this study was to 1) determine whether serum NEFAs can be found in the oviductal microenvironment using a polarized oviductal epithelial cell culture and more specifically to 2) study the effect of the BSA gradient and the direction of the NEFA gradient. Bovine oviductal epithelial cells from slaughterhouse oviducts in Day 3 to 5 of the luteal phase were mechanically isolated and cultured for 7 days in a flask. Cells were transferred in a polarized oviductal epithelial cell culture-system (Snapwell® polyester membrane, pore size 0.4 µm, 4 × 106 pores cm–2) with an apical (A) and basal (B) medium supporting cell growth until the transepithelial electric resistance reached 700 Ωcm2 (Day 6). Then, cells were exposed to a transmembranary BSA (0.75 or 3% BSA) or NEFA gradient (0 or 360 µM NEFA: 115 µM oleic acid, 140 µM stearic acid, 105 µM palmitic acid) for 48 h in 4 experimental setups: 1) A and B containing 0.75% BSA and B supplemented with NEFA, 2) same as in 1 but NEFAs were added in A, 3) A containing 0.75% BSA and B supplemented with 3% BSA and NEFA, 4) same as in 3 but with 3% BSA + NEFA in A and B contained 0.75% BSA. Samples were analyzed for total NEFA and specific fatty-acid concentrations by photometric and gas chromatographic assays. In total, 72 wells in 4 replicates were cultured and analyzed. Data were processed by paired sample t-tests and student t-tests. Exposure to NEFA did not alter the transepithelial electric resistance. In Exp. 1, the total NEFA concentration in A increased with 0.013 µM (21.11%) over 48 h of NEFA exposure in the basal compartment explained by a significant rise of stearic (8.52 µM, 20.68%) and oleic acid (12.86 µM, 45.17%) accompanied with only a 19.45% decrease of total NEFA in B (P < 0.05). When the transport direction was reversed in Exp. 2, the total NEFA concentration decreased 53.4% in A, with no obvious NEFA rise in B. Implementing a BSA gradient (Exp. 3 and 4) was associated with a slight decrease (13 and 15.7%, respectively; P < 0.05) of NEFA concentration in the supplemented compartment, but no obvious NEFA increase in the opposite compartment could be detected. Overall, these results suggest that NEFA transport in this culture system is tightly regulated and can only be influenced by the transport direction of the NEFA. Further research should focus on transport and metabolisation of the fatty acids added.

5 THE EFFECT OF ELEVATED NONESTERIFIED FATTY ACID CONCENTRATIONS ON MURINE IN VITRO FOLLICULOGENESIS AND SUBSEQUENT OOCYTE DEVELOPMENTAL COMPETENCE

Metabolic disorders, like negative energy balance and obesity, are characterized by elevated serum non-esterified fatty acid (NEFA) concentrations, due to upregulated lipolysis. We previously showed that short-term (24-h) NEFA exposure of bovine oocytes during their final maturation is detrimental to oocyte and embryo quality (Van Hoeck et al. 2011 PLoS ONE 6, e23183). However, the typical chronic exposure as present in diseased females has never been studied before. Therefore, we aimed to use a murine preantral follicle culture model to study the effect of long-term NEFA exposure on folliculogenesis, antrum formation, and the developmental competence of the enclosed oocyte. Early secondary murine follicles (n = 629) from 13-day-old B6CBAF1 mice were individually cultured for 12 days. Follicles were exposed to 4 treatments containing physiological or pathological concentrations of stearic acid (SA), palmitic acid (PA), or oleic acid (OA) for 12 days: BASAL (72 µM NEFA mix, n = 154), high SA (280 µM SA, n = 160), high OA (210 µM OA, n = 159), and NEFA (720 µM NEFA mix, n = 156). Oocytes were routinely fertilized 20 h after a final maturation stimulus [hCG, epidermal growth factor (EGF)]. Presumptive zygotes were denuded and cultured until the blastocyst stage (Day 5 pre-implantation). Data were analyzed with a mixed-model ANOVA or binary logistic regression. The SA-exposed follicles displayed a reduced Day-12 antrum formation, compared to BASAL and NEFA follicles (68 v. 78 and 83%, P = 0.03 and P < 0.01), which was similar for OA follicles compared with the NEFA follicles (72 v. 83%, P = 0.04). Follicles cultured in SA conditions were, on average, 10, 13, and 11% smaller in diameter compared with BASAL, OA, and NEFA follicles (P = 0.05, P = 0.01, and P = 0.04, respectively). Likewise, the follicular growth during the 12-day culture was significantly reduced for SA follicles compared with BASAL and NEFA follicles (P < 0.01). Neither Day-12 oocyte diameter nor oocyte growth were affected by treatment. After fertilization, the oocytes from NEFA-exposed follicles showed a decreased cleavage rate on Day 1 pre-implantation, compared with BASAL oocytes (53 v. 69%; P < 0.01). Accordingly, the percentage of Day-5 blastocysts was reduced for oocytes from NEFA follicles compared with BASAL follicles (42 v. 63%; P < 0.01). Also, oocytes from SA and OA follicles showed reduced blastocyst rates compared with BASAL oocytes (32 and 33 v. 63%; P < 0.01). Exposure of follicles to SA or OA seems to slightly impair antrum formation and follicle growth. Furthermore, oocytes originating from NEFA-, OA-, and SA-exposed follicles had a dramatically reduced developmental competence compared with oocytes from follicles cultured in physiological BASAL conditions, an effect most apparent at blastocyst formation. In conclusion, we show for the first time that elevated NEFA concentrations affect murine follicular development and that this negative effect is carried through to the oocyte and pre-implantation embryo development. Ongoing research focuses on the pathways involved.

139 THE EFFECT OF STARCH AND SATURATED OR POLYUNSATURATED RICH DIETS ON IN VITRO BOVINE EMBRYO DEVELOPMENT AND QUALITY

In humans, diets rich in carbohydrates and saturated fatty acids are common and the subsequent altered metabolism has been linked to reduced fertility. Also, modern dairy cows are fed milk-stimulating diets rich in starch and fatty acids. The pre-implantation embryo is vulnerable to nutritionally induced changes in its micro-environment. We have shown that a dietary induced hyperlipidemia has detrimental consequences on development, quality and gene expression patterns of the pre-implantation embryo (Leroy et al. 2010 Hum. Reprod. 25, 768–778). Hyperlipidemia was induced by feeding starch- and saturated-fat-rich diets and the collected serum was added during bovine embryo culture. In the present study, we hypothesized that changing the saturated into a polyunsaturated fat source could alleviate these negative effects. We furthermore hypothesized that the sequence in which the different fat sources are given can affect embryo development and quality. Therefore, in the first setup: bovine zygotes (n = 1104; 4 replicates) were cultured in SOF medium supplemented with 10% serum collected from 3 synchronized heifers after 3 successive dietary treatments each fed during 4 weeks: control serum after a hay-based maintenance diet, saturated serum (SAT1) after a carbohydrate rich diet supplemented with saturated fatty acids (twice maintenance, C16 : 0, palmitic acid, 4.5% total fat), or unsaturated serum (UNSAT1) after a carbohydrate-rich diet supplemented with unsaturated fatty acids (twice maintenance, C18 : 3, linolenic acid, 4.45% total fat). In the second setup (n = 1483; 5 replicates): bovine zygotes were cultured in SOF medium supplemented with 10% serum from 3 synchronized heifers successively fed the 3 same dietary treatments in different order: control, unsaturated (UNSAT2), or saturated serum (SAT2). Day 7 blastocyst developmental competence (binary logistic regression), total cell number, and apoptotic cell ratio (ACR) (mixed model ANOVA) were evaluated. Supplementation of SAT1 serum in culture significantly reduced blastocysts from cleaved zygotes (36.7% v. 44.7%) and significantly increased ACR (0.1% ± 0.05 v. 0.06% ± 0.04) compared to controls (P < 0.05). Zygotes cultured in UNSAT1 displayed a significant higher cell number than control and SAT1 blastocysts (126.4 ± 25.7 v. 120.4 ± 24.3 and 108.3 ± 15.5, respectively; P ≤ 0.05) and lower ACR compared to SAT1 blastocysts (0.06% ± 0.03 v. 0.1% ± 0.05; P < 0.05). However, UNSAT1 zygotes showed a tendency for reduced development into blastocysts compared to control zygotes (P = 0.05). By contrast, UNSAT2 serum significantly improved blastocysts development from cleaved zygotes (40.0% v. 26.7%) and led to a lower ACR (0.06% ± 0.04 v. 0.1% ± 0.05) compared to SAT2 embryos (P < 0.05). In conclusion, our study confirmed the negative effects diets rich in starch and saturated fat on pre-implantation embryo development and quality. Changing the fat source to polyunsaturated eliminated these negative effects. Furthermore, we showed that the order in which different fat types are fed affects the zygote’s ability to sustain further development.

181 XENOTRANSPLANTATION OF BOVINE OVARIAN CORTEX IN SEVERE COMBINED IMMUNODEFICIENT MICE TO STUDY PRE-ANTRAL FOLLICULAR DEVELOPMENT: DETERMINATION OF THE OPTIMAL GRAFT SITE

Nowadays, a lot of attention is given to female reproductive preservation strategies. However, opportunities to study the dynamics of pre-antral folliculogenesis in vitro are not readily available because routine procedures for culture of (ruminant) isolated follicles are still lacking. One of the current techniques to study follicular dynamics and activation is xenografting bovine ovarian cortex into immune-deficient mice. Several transplantation sites have been described (Bols et al. 2010 Theriogenology 73, 740–747), such as subcutaneously (SC), underneath the kidney capsule (SK), intramuscularly (IM), and underneath the peritoneum (SP). In the present study, our objective was to determine the optimal host type and graft location in order to maximize the success of graft retrieval and follicular development. In total, 22 mice [12 conventional, 10 severe combined immunodeficient (SCID)] were used as graft recipients. All mice were anesthetized with an intraperitoneal injection of ketamine and xylazine and subsequently sterilized. Small pieces (maximum dimension of 9 mm3) of adult bovine ovarian cortex, retrieved from slaughterhouse ovaries, were then grafted at 4 different sites: SC grafts were localised at the left-hand side of the neck of the host, IM at the left hamstring (between the semimembranosus and semitendinosus muscle), SK under the left kidney capsule or SP, namely on the left and right-hand side, retroperitoneal. Blood vessels were macroscopically localised and stimulated by curettage before the cortex piece was grafted. Fourteen days later, mice were killed and the graft was localised and retrieved (if possible), after which the presence of follicles was assessed by visualisation following hematoxilin-eosin staining of histological slides. Data (Table 1) show that graft retrieval rates were highest when cortex fragments were grafted underneath the peritoneum (SP site). Although the extent of follicular presence and quality assessment of the detected follicles surely require additional experiments, our data do not support a difference between SCID or a conventional mouse strain as an optimal host type when it comes to graft retrieval rates and the determination of follicular activity when grafts are left in place for a limited period of 14 days. Table 1.Graft retrieval and follicular activity of xenotransplanted, bovine adult cortex fragments: conventional strain compared with a SCID mouse strain

BMI-related metabolic composition of the follicular fluid of women undergoing assisted reproductive treatment and the consequences for oocyte and embryo quality

STUDY QUESTION

Is the metabolic composition of the follicular fluid of women undergoing assisted reproductive treatment (ART) related to serum composition and BMI and is it associated with oocyte and embryo quality?

SUMMARY ANSWER

We showed that metabolic alterations in the serum are reflected in the follicular fluid and that some of these alterations may affect oocyte quality, irrespective of BMI.

WHAT IS KNOWN ALREADY

Many studies have focused on the effect of metabolic disorders, such as obesity and type 2 diabetes, on assisted reproduction outcomes. There are, however, only few studies focusing on the importance of the correlation between serum and follicular fluid compositions and the composition of the follicular fluid as the oocyte's micro-environment, affecting its development and subsequent embryo quality.

DESIGN, PARTICIPANTS AND SETTING

In this prospective cohort study, patient information, fertility treatment outcome data, follicular fluid and serum were obtained from women undergoing ART. Patients were categorized according to their BMI (kg/m(2)) as normal (n = 60), overweight (n = 26) or obese (n = 20). Serum and follicular fluid samples were analyzed for urea, total protein, albumin, cholesterol, high-density lipoprotein cholesterol, triglycerides, non-esterified fatty acids, apolipoprotein A1, apolipoprotein B, glucose, lactate, C-reactive protein, insulin-like growth factor -1 (IGF-1), IGF-binding protein 3 (only in follicular fluid), free carnitine and total carnitine. Metabolite concentrations in serum and follicular fluid samples were correlated and were associated with BMI and fertility treatment outcome.

MAIN RESULTS

Most serum metabolite differences between patients were reflected in the follicular fluid (P < 0.05). Follicular fluid apolipoprotein A1 and follicular fluid total protein concentrations negatively affected oocyte quality parameters (P < 0.05). However, overall BMI-related associations were poor.

BIAS, CONFOUNDING AND OTHER REASONS FOR CAUTION

In this study, we included every patient willing to participate. Within this cohort, women with a BMI transcending 35 kg/m(2) were scarce (n = 2), because extremely overweight women are mostly advised to lose weight before starting ART. Furthermore, the number of patients in each BMI group was different, possibly masking associations between the metabolic composition of serum and follicular fluid and oocyte quality parameters.

GENERALIZABILITY TO OTHER POPULATIONS

There were significant associations indicating that metabolic changes in the serum are reflected in the follicular fluid, potentially affecting oocyte quality, irrespective of the patient's BMI. For ethical reasons, this study only focused on women already in need of artificial reproductive treatment. From a metabolic point of view, we consider this cohort as a representative sample of all women of reproductive age.

STUDY FUNDING

This study was funded by the special research fund, university of Antwerp (BOF UA). None of the authors has any conflict of interest to declare.

Anesthesie van kittens - een literatuuroverzicht met nadruk op de mogelijkheden in België

In België worden zelden electieve chirurgische ingrepen uitgevoerd bij zeer jonge kleine huisdieren. Veel dierenartsen hebben dan ook weinig ervaring met de anesthesie van pediatrische patiënten. In dit overzichtsartikel wordt kort ingegaan op de risicofactoren bij de anesthesie van kittens, gezien hun specifieke anatomie en fysiologie. Vervolgens wordt een overzicht gegeven van geschikte anesthetische protocollen. Injectieanesthesie op basis van combinaties met ketamine is een praktische, economische en efficiënte optie.

Intrafollicular conditions as a major link between maternal metabolism and oocyte quality: a focus on dairy cow fertility

Reduced oocyte and embryo quality are recognised as major factors in the problem of disappointing fertility in high producing dairy cows. This review aims to shed more light on the importance of the intrafollicular environment in the subfertility problem in dairy cows. Metabolic disturbances associated with negative energy balance (NEB) early postpartum are associated with ovarian dysfunction. Changes in the growth pattern of the ovarian follicle during a period of NEB can indirectly affect oocyte quality. Furthermore, a maternal metabolic disorder (linked with NEB or nutritionally induced) may alter the endocrine and biochemical composition of the follicular fluid, the micro-environment of the growing and maturing female gamete. The maturing oocyte is very sensitive to any perturbation in its direct environment and in vitro maturation models revealed that some of these metabolic changes reduce the oocyte’s developmental competence. Also, embryo quality is significantly reduced due to maturation in adverse conditions. Well balanced and timed oocyte metabolism and gene expression are crucial to safeguard an optimal oocyte development. In that perspective, metabolome and transcriptome parameters of the oocyte may serve to predict reproductive success rates. Finally, there is growing evidence that adverse conditions for oocyte growth and maturation may also jeopardise the health and performance of the offspring.

Unravelling the needs of singly in vitro-produced bovine embryos: from cumulus cell co-culture to semi-defined, oil-free culture conditions

Producing bovine in vitro embryos individually is a challenge as it generally leads to impaired embryo development. Earlier research optimised a single embryo in vitro production (IVP) protocol using serum, cumulus cells and oil during culture. As some of these factors are undesirable in certain circumstances, the present study investigated their necessity and possible interactions, and defined their role during single-embryo culture. Although the cumulus cell monolayer produced progesterone, it appeared not to be a key factor in supporting single-embryo development. Because in vitro culture in large medium volumes was shown to impair single-embryo development, two new oil-free culture protocols were tested. Using a 30-µL droplet of medium in 96-well plates with a small surface area resulted in comparable blastocyst rates to those obtained under oil. When serum was used, co-culture with cumulus cells seems necessary, leading to consistently high blastocyst rates. Finally, a serum-free, oil-free culture system using insulin, transferrin, selenium and BSA resulted in embryos with similar total cell numbers and apoptotic cell ratios, but blastocyst rates did not equal those obtained with serum and co-culture. This research additionally stresses the fact that specific interaction mechanisms between somatic cells and a developing in vitro embryo are far from unravelled.

210 CO-CULTURE WITH AUTOLOGOUS CUMULUS CELLS SUPPORTS THE INDIVIDUAL DEVELOPMENT OF SINGLY IN VITRO-MATURED AND FERTILIZED BOVINE OOCYTES

The ability to produce embryos singly in vitro (in vitro production, IVP) would be a useful tool for many purposes. Without the interfering effects of other developing or degenerating oocytes or embryos, such an individual IVP system is the tool of choice for studies on oocyte quality and oocyte–embryo metabolism. Unfortunately, individual IVP in most cases leads to unsatisfactorily low blastocyst rates. Earlier work showed that individual culture of zygotes on a cumulus cell (CC) monolayer resulted in comparable numbers of good-quality embryos, as obtained following regular group culture (Goovaerts et al. 2009 Theriogenology 71, 729–738). However, co-culture with somatic cells is often criticised because of the undefined culture conditions and for sanitary reasons. In the cited study, CC for monolayer production were obtained from a different batch of ovaries. Our specific aim was to use CC from the zygote itself (autologous CC). Grade I COC (n = 660) were collected from slaughterhouse ovaries and randomly assigned to 2 treatments (5 replicates): a completely individual ‘single-oocyte’ IVP protocol, or routine group IVP as a control. Individual maturation (TCM-199 + 20% serum) and fertilization were performed in 20-μL droplets under oil in 24-well plates. Subsequently, each zygote was stripped and cultured in 20 μL of medium (SOF + 5% serum, 90% N2, 5% CO2, 5% O2), to which the autologous stripped CC were added. Group maturation and fertilization were carried out per 100 COC in 500 μL, whereas group culture was performed per 25 zygotes in 50-μL droplets under oil. Cleavage, blastocyst, and hatching rates were determined 2, 8, and 10 days post-fertilization, respectively. Possible effects of the individual and group cultures were evaluated with binary logistic regression (SPSS 15.0, SPSS Inc., Chicago, IL). No interactions between replicate and treatment were found (P > 0.05). Although a blastocyst rate of 15.1% was obtained using single IVP, the general efficacy of the single-embryo production system was lower when compared with group culture (Table 1). In conclusion, although developmental competence was impaired using individual IVP, co-culture with autologous cumulus cells can be useful in specific experimental setups in which the influence of other oocytes or embryos or heterologous somatic cells is unacceptable. Table 1.Cleavage, blastocyst, and hatching rates after individual and group in vitro production (IVP)

167 VISUALISATION OF FAT ACCUMULATION IN BOVINE PREANTRAL AND ANTRAL OOCYTES USING 2-PHOTON MICROSCOPY

Fat metabolism is important in oocyte development (Kim et al. 2001; Sturmey et al. 2009). Our main objective was to develop a straightforward method that allows us to describe fat distribution and quantify fat accumulation in bovine oocytes throughout folliculogenesis. Fat accumulation dynamics can be studied by making microscopically repeated cross-sections or Z-stacks through oocytes of different developmental stages. The most important limiting factor in oocyte 3D visualisation studies is the size of the oocyte (between 110 and 120 μm in diameter), making it impossible to visualise it as a whole. If visualisation of the bottommost hemisphere is desirable, overlying Z-stacks will disperse the excitation and emission light, creating artefacts that will distort the image and trouble the results (indicated by former unpublished results). Therefore, we investigated the use of an alternative visualisation protocol staining the oocytes with Nile Red as an intracellular, triglyceride-specific (when emission is captured at 590 nm), fluorescent dye (Greenspan et al. 1985; Leroy et al. 2005), this combined with 2-photon excitation technology. In total, ovaries from 10 cows were collected at slaughter. Ovaries were pooled per cow. Only cows with apparent follicular activity on both ovaries were selected. Antral follicles with a diameter of <3 mm, between 3 and 6 mm, and >6 mm were aspirated. Apart from oocytes collected from each of these 3 follicle classes, preantral follicles were harvested from ovarian cortex tissue through mechanical isolation and enzymatic digestion by collagenase type IA. In total, 3 oocytes per follicle class were collected for each pair of ovaries. They were fixed in 2% glutaraldehyde and 2% formaldehyde and stained with Nile Red (1 μg mL–1). After mounting, images were acquired with a Zeiss LSM 510 reversed 2-photon microscope (Carl Zeiss GmbH, Jena, Germany) using an excitation wavelength of 807 nm, with an emission spectrum covered between 580 and 591 nm. Our results show that even with biphoton excitation, it remains very difficult to visualise fat droplet distribution in >100-μm oocytes. However, accurate images can be obtained of the upper hemisphere of the oocyte. These images can be used in future research on the dynamics of the distribution and the accumulation of lipid. Preliminary descriptive results clearly show that the relative amount of lipid droplets is lower and their size is smaller in oocytes from preantral follicles compared with antral counterparts. We can preliminary conclude that fat accumulation and the aggregation in fat droplets might take place preceding or even during antral development. We can visualise preantral oocytes as a whole in contrast to antral oocytes where only the upper hemisphere is visible without distortions. Image analysis software is currently applied to allow for a more quantitative interpretation. D. De Rijck.

239 POSSIBLE MECHANISMS OF SPERM DAMAGE CAUSED BY HEAT STRESS IN EUROPEAN BULLS RAISED IN TROPICAL ENVIRONMENTS

Previous studies have indicated that semen of heat-stressed bulls shows impaired mitochondrial activity and high levels of oxidative stress, which may cause structural damage to biomolecules, DNA, lipids, carbohydrates and proteins, as well as other cellular components (Nichi et al. 2006 Theriogenology 66, 822–828). Disruption of the sperm mitochondria could have a potential damaging effect not only on an individual sperm cell but also on the surrounding cells, especially regarding the sperm membrane, possibly due to the release of a high amount of reactive oxygen species (ROS) produced in this environment (rich in electrons) that would then lead to oxidative stress. To test this hypothesis, semen samples of 11 Simmental bulls kept in tropical environments were collected during the summer months. Semen was evaluated as follows: the 3-3′ diaminobenzidine stain (DAB) as an index of mitochondrial activity, the hypo-osmotic swelling test (HOST) as an index of membrane integrity, measurement of thiobarbituric acid reactive substances (TBARS) as an index of lipid peroxidation, and measurement of the enzymatic antioxidants superoxide dismutase, catalase and glutathione peroxidase activities. For correlation analysis, the Pearson test was used (variables were transformed when necessary), and for nonparametric variables, the Spearman rank test was used. A high positive correlation was found between sperm cells with highly active mitochondria (DAB class I) and the percentage of cells with intact membrane by HOST (r = 0.93; P < 0.05), and a negative correlation between the latter and the percentage of inactive mitochondria (r = –0.91; P < 0.05), indicating that the higher the percentage of cells showing impaired mitochondrial activity, the higher the percentage of cells with damaged membrane. There was also a positive correlation between TBARS and the percentage of cells with disrupted mitochondria (r = 0.86; P < 0.05), indicating that the higher the percentage of sperm with impaired mitochondrial activity, the higher the oxidative stress. No correlation existed between the enzymatic antioxidants and any of the variables studied. The results indicate that heat stress may lead to an increase in testicular ROS levels, overcoming the seminal antioxidant protection. This, in turn, may cause damage of the mitochondria and a subsequent release of more pro-oxidative substances, and an exponential increase of oxidative stress. Understanding these mechanisms may lead to more tailored antioxidant therapies in the future. The authors thank FAPESP for the scholarship and financial support.

273 CONSEQUENCE OF HIGH NONESTERIFIED FATTY ACID CONCENTRATIONS DURING BOVINE OOCYTE IN VITRO MATURATION ON mRNA TRANSCRIPT ABUNDANCE OF BLASTOCYSTS

In recent years, high nonesterified fatty acid (NEFA) concentrations have been intensively discussed as an important metabolic cue linking negative energy balance in high yielding dairy cows early postpartum to disappointing fertility. Previous research has shown that high NEFA concentrations during in vitro oocyte maturation not only induce significant negative effects on the developmental capacity of oocytes but also reduce the quality and viability of the subsequent embryos that do survive until 7 days post-insemination. Because NEFA are known to regulate gene expression, the objective of this study was to investigate the effect of NEFA exposure during bovine in vitro oocyte maturation on the relative transcript abundance in the resultant day 7 blastocysts. This study focused on key genes related to embryonic quality, apoptosis, adaptation to stress, metabolism, DNA methylation, growth factors, and fatty acid synthesis. During a serum-free maturation period of 24 h, bovine cumulus–oocyte complexes were exposed to maturation medium (0.75% BSA) supplemented with 1) physiological NEFA concentrations (control; 150 μM of total NEFA, i.e. oleic, stearic, and palmitic acid), 2) elevated stearic acid concentrations (HSA; 75 μM of stearic acid), and 3) elevated NEFA concentrations (HCOMBI; 425 μM of total NEFA). Following IVF using semen from a bull of proven fertility, zygotes were cultured in SOF (+5% of FCS) medium for 7 days. Studied mRNA transcripts were quantified by real-time quantitative RT-PCR. Experiments were conducted to determine levels of each transcript relative to H2AZ in every sample. Relative mRNA abundance differences among groups were analysed by one-way ANOVA. Significant increases (P < 0.05) in relative mRNA abundance of the HCOMBI embryos were found for genes related to DNA methylation (DNMT3A), growth factors (IGF2R), glucose transport (SLC2A1), and fatty acid synthesis (ACSL1 and ACACA) compared with control embryos. Furthermore, HCOMBI embryos revealed a significantly higher expression (P < 0.05) of IGF2R and ACSL1 than did HSA embryos. The level of transcripts of genes related to mitochondrial biogenesis (TFAM) and the adaptation to stress (MNSOD) also tended to be increased in HCOMBI embryos compared with control embryos (P = 0.09 and P = 0.10, respectively). In conclusion, there is ample evidence that embryos originating from oocytes matured under negative energy balance conditions show aberrant transcriptional activities. These results might improve our current understanding of the possible mechanisms through which NEFA exposure during oocyte maturation affects the developmental capacity, quality, and viability of the resultant embryo.

Immunohistochemical visualization of insulin receptors in formalin-fixed bovine ovaries post mortem and in granulosa cells collected in vivo

Insulin is crucial for granulosa cell (GC) function, follicle growth and ovulation in cows; low insulin levels increase the risk for anoestrus. Apart from insulin concentration, alterations in the insulin receptor (IR) density on GC may affect follicular growth and steroidogenesis. Data about the IR protein distribution in the bovine follicle are scarce. Therefore, we aimed to develop a quantifiable staining method for IR protein on histological sections of bovine follicles in different developmental stages, and to apply this technique on GC obtained in living cows. In a first experiment, bovine ovaries were collected post mortem, formalin fixed, routinely processed, and stained with monoclonal murine IR-antibodies, peroxidase-labeled goat anti-mouse antibodies, and substrate chromogen. Based on their diameter, follicles were morphologically classified as small antral (SAF; n = 141), dominant (DF; n=28) or subordinate (SF; n=8); DF and SF were further classified as healthy or atretic based on the ratio of estrogen and progesterone concentrations in their follicular fluid. Using specialized software, the proportion of pixels displaying a positive staining signal was computed as a measure for IR density in three selected follicular regions: GC, theca (T) and stroma (STR). Results were analyzed in an ANOVA model with follicle type, region and health status as fixed factors. In SAF, DF, and SF, IR density was notably higher in GC than T or STR; the latter two displayed very low or no IR presence. The IR density in SAF was stronger than in DF and tended to be stronger than in SF. Staining intensity was not altered in atretic compared to healthy follicles. In corpus luteum, cumulus-oocyte complexes and pre-antral follicles, no IR could be detected. In a second experiment, GC samples were collected from 20 live cows on 30 and 70 d post partum by transvaginal follicular fluid aspiration, projected on glass slides, and stained using the protocol described above. Most samples yielded sufficient GC and IR was clearly visualized. However, objective quantification of the staining signal was impeded by extensive variation in the arrangement and density of GC and the amount of cellular debris on the slides. Altogether, strong IR presence in GC, most notably in SAF, suggests acquisition of IR as a key event in early follicle growth. Furthermore, we have developed a quantifiable staining technique for bovine follicles that may be applicable for GC obtained in live cows, although this method requires further standardization.

358 THE CONSEQUENCE OF HIGH NON-ESTERIFIED FATTY ACID CONCENTRATIONS DURING OOCYTE IN VITRO MATURATION ON BOVINE EMBRYO QUALITY

High non-esterified fatty acid (NEFA) concentrations in the blood, associated with negative energy balance (NEB), obesity or diabetes Type II are known to alter the follicular micro-environment. These environmental changes have been associated with disappointing fertility outcome through disabled ovarian cell function and oocyte’s developmental competence. Our hypothesis was that elevated NEFA concentrations during final oocyte maturation might hamper the quality of the pre-implantation embryo as well. To assess embryo quality, the present study focused on total cell number and apoptotic index in 7-day-old embryos. Applied NEFA concentrations in the maturation medium were based on analyses in the follicular fluid of high yielding dairy cows early post partum during NEB. Bovine cumulus-oocyte complexes were exposed to 1) physiological NEFA concentrations, i.e. a combination of basal palmitic (25 μM), stearic (50 μM) and oleic acid (75 μM) concentrations (CONTROL), 2) elevated NEFA concentrations, i.e. a combination of high palmitic (75 μM), stearic (150 μM) and oleic acid (200 μM) concentrations (HIGH COMBI) and 3) elevated palmitic acid (75 μM) concentrations (HIGH PA). Palmitic acid has been recognized as a major saturated fatty acid in terms of cellular toxicity. After serum-free in vitro maturation (24 h) and fertilization (22 h), zygotes were cultured in SOF medium with 5% serum for 7 days. Blastocysts were evaluated for developmental competence, total cell number (by Propidium Iodide staining) and apoptotic index (by TUNEL detection kit). In total, 684 oocytes were cultured in 3 replicates. Data were analyzed with binary logistic regression and a mixed model ANOVA. Preliminary research showed that maturation in a combination of basal NEFA concentrations has no effect on oocyte’s developmental competence compared to the standard serum free maturation system. In the present study, maturation in HIGH COMBI resulted in significantly lower blastocyst rates (21.4%) compared to CONTROL (30.1%) (P = 0.03). No significant effect of HIGH PA maturation on blastocyst rate (24.1%) could be found. Also total cell number tended to be lower in the HIGH COMBI (104.7 ± 26.1) compared to CONTROL (125.8 ± 29.4) (P = 0.08). The apoptotic index was significantly increased in the HIGH PA group (0.22 ± 0.12) compared to the CONTROL group (0.11 ± 0.07) (P = 0.02) and tended to be higher than the HIGH COMBI group (0.14 ± 0.12) (P = 0.06). Maternal metabolic conditions, leading to increased lipolysis and high NEFA concentrations, can hamper fertility through a reduction of the oocyte’s developmental competence. The data of the present study furthermore suggest that elevated NEFAs might induce a negative carry over effect from the oocyte during its maturation to the embryo quality. This may ultimately lead to embryonic mortality and thus to a disappointing fertility outcome. Veerle Van Hoeck is supported by the Special Research Fund, University of Antwerp (Grant 22590).

317 RESISTANCE AGAINST DIFFERENT REACTIVE OXYGEN SPECIES IN BOVINE EPIDIDYMAL SPERM UNDER DISTINCT MATURATION STATUS

Oxidative stress is caused by reactive oxygen species (ROS) that may cause structural damage to biomolecules, DNA, lipids, carbohydrates and proteins, as well as other cellular components. Evidence indicates that oxidation products are also deleterious to biological systems. Spermatozoa are particularly susceptible the oxidative stress, mainly due to the reduced cytoplasm and the high content of polyunsaturated fatty acids in its membrane. The mechanisms by which sperm acquire antioxidant capacity are still not completely elucidated. The aim was to study the resistance of sperm derived from different epididymal compartments (caudae and head) to the different ROS and to the lipid peroxidation product malondialdehyde (MDA). Epididymal sperm samples from 4 testicles were collected from the head and caudae epididymides. Sperm samples were then incubated (1 h, 37°C) with 4 ROS inducer mechanisms: xanthine/xanthine oxidase (produces superoxide anion), hydrogen peroxide (4 mM), ascorbate and ferrous sulfate (4 mM; produces hydroxyl radical), and MDA. Samples were analyzed for 3-3′ diaminobenzidine stain, as an index of mitochondrial activity; the eosin nigrosin stain, as an index of membrane integrity; the simple stain (fast green/Bengal rose), as an index of acrosome integrity; and the measurement of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation. Statistical analysis was performed using the SAS System for Windows (SAS Institute Inc., Cary, NC, USA; least significant differences test and Pearson correlation). Results showed that immature sperm (head epididymides) were significantly more susceptible to the MDA and to the hydroxyl radical in all studied variables, especially acrosomes, membranes, and mitochondrial potential. Semen derived from the caudae epididymides was more susceptible to the hydrogen peroxide and to the MDA, especially regarding mitochondrial potential. In semen from the epididymal head, a positive correlation was found between TBARS and sperm showing no mitochondrial potential (r = 0.66, P = 0.01). On the other hand, negative correlations were found between TBARS and sperm with damaged acrosome and membrane (r = -0.63, P = 0.01 and r = -0.58, P = 0.02, respectively) in samples collected from the caudae epididymides. The present results suggest that sperm susceptibility to the attack of ROS is different throughout maturation. Although immature sperm are more susceptible to the hydroxyl radical, mature sperm are more susceptible to the hydrogen peroxide. Furthermore, MDA, a product of lipid peroxidation, is also deleterious to the sperm, indicating that once oxidative stress starts, further damage may be caused by their products. The authors thankNutricell for the media used in the experiment andFAPESP for financial support (process #06/05736-1).

207 DEVELOPMENT OF A ROUTINE IN VITRO EMBRYO PRODUCTION SYSTEM USING SINGLY IN VITRO-MATURED, FERTILIZED, AND CULTURED BOVINE OOCYTES

An in vitro embryo production system (IVP), in which a single oocyte can be tracked from the moment of retrieval up to the blastocyst stage, would be a valuable tool for studies linking developmental competence and embryo metabolism to oocyte quality and follicular environment. Unfortunately, to date, data on individual IVP are inconsistent, and in most cases show unsatisfactory blastocyst rates. Earlier studies revealed that individual culture on a cumulus cell (CC) monolayer resulted in comparable numbers of good-quality embryos as obtained after regular group culture (Goovaerts et al. 2008 Reprod. Dom. Anim. 43 (Suppl. 3), 190). Because, in the latter study, single culture was performed after group maturation and fertilization, the aim of this study was to develop and test an individual IVP system using bovine oocytes or zygotes obtained after single maturation and single fertilization. Therefore, 532 grade I COC from slaughterhouse ovaries (3 replicates) were randomly assigned to 1 of 2 treatments: a complete individual IVP protocol, or a routine group IVP as a control. Individual maturation (TCM-199 + 20% serum) and fertilization were performed in 20-μL droplets under oil in 24-well plates. Subsequently, each zygote was cultured in 20 μL of medium (SOF + 5% serum, 90% N2, 5% CO2, 5% O2) on a 6-day-old monolayer of matured CC (5% CO2 in air). Group maturation and fertilization were carried out per 100 COC in 500 μL, whereas group culture was performed per 25 zygotes in 50-μL droplets under oil. Cleavage, blastocyst, and hatching rates were assessed 2, 8, and 10 days postfertilization, respectively. Possible effects of individual and group culture were evaluated with binary logistic regression (SPSS 15.0). No interactions between replicate and treatment could be found (P > 0.05). Cleavage and blastocyst rates were significantly lower after individual IVP, compared with group IVP, whereas the blastocyst rates on cleaved zygotes and the hatching rates did not differ significantly (Table 1). In conclusion, acceptable blastocyst rates (25.1%) could be obtained after individual IVP. The lower blastocyst rates were associated with the lower cleavage rates, and no effect of the individual embryo culture system on embryo development could be found. Table 1.Cleavage, blastocyst, and hatching rates after individual and group in vitro embryo production (IVP)

Ovarian follicular dynamics. A review with emphasis on the bovine species. Part II: Antral development, exogenous influence and future prospects

During an oestrous cycle, a cohort of antral follicles develops into--depending on the species--one or more ovulatory follicles. The bovine oestrous cycle is characterized by two to three such cohorts or growth waves, only the last of which will result in an ovulation. In every growth wave, several antral follicles are recruited for development. Recruited follicles are subjected to a selection process, whereby ever decreasing levels of follicle stimulating hormone (FSH) are available to the FSH dependent follicles. In the cow, a single follicle from the cohort will acquire dominance. The ability of the dominant follicle to prosper under basic FSH levels is ascribed to a transition in hormone dependency from FSH to luteinizing hormone. The exact follicle selection mechanism remains, however, to be elucidated. The beginning of this article focuses on the recruitment, selection and dominance phases in antral follicle development. Subsequently, the conditions leading to successful maturation and ovulation are discussed. The next section expounds upon the mechanisms for exogenous modulation of follicular dynamics with the aim of superovulation/superstimulation, and finally prospective future research directions are sketched.

Ovarian follicular dynamics: a review with emphasis on the bovine species. Part I: Folliculogenesis and pre-antral follicle development

Recent scientific research into pre-antral follicular dynamics has resulted in the discovery of a wide range of hormones and local factors that influence primordial follicle activation and contribute to follicular development. The putative role of several of these mediators in the follicle growth process has been elucidated by genetic and molecular investigations. Crucial questions, such as the mechanism for primordial follicle initiation and the interplay between oocyte and granulosa cells in this process, remain however unresolved. This review article commences with a description of the embryogenesis of the ovary and follicles. Next, the different stages in the development from primordial to pre-antral follicle are discussed. Thereafter, a short overview of the various in vitro models for the study of follicular dynamics is presented. Finally, an in-depth discussion of pre-antral follicle development engages in the current hypotheses regarding primordial follicle activation, and the role of gonadotrophins and angiogenesis.