Reduced fertility in high-yielding dairy cows: are the oocyte and embryo in danger? Part I. The importance of negative energy balance and altered corpus luteum function to the reduction of oocyte and embryo quality in high-yielding dairy cows

Fertility in high yielding dairy cows is declining, and there is increasing evidence to presume that oocyte and embryo quality are major factors in the complex pathogenesis of reproductive failure. In this report we present an overview of possible mechanisms linking negative energy balance (NEB) and deficiencies in oocyte and embryo developmental competence; specifically, in the high producing dairy cow. Changes in follicular growth patterns during a period of NEB can indirectly affect oocyte quality. The endocrine and biochemical changes, which are associated with NEB, are reflected in the microenvironment of the growing and maturing female gamete, and likely result in the ovulation of a developmentally incompetent oocyte. Even after an oocyte is successfully ovulated and fertilized, a full-term pregnancy is still not guaranteed. Inadequate corpus luteum function, associated with reduced progesterone, and probably also low insulin-like growth factor concentrations, can cause a suboptimal microenvironment in the uterus that is incapable of sustaining early embryonic life. This may partly account for the low conception rates and the high incidence of early embryonic mortality in high yielding dairy cows.

Effects of ovum pick-up frequency and FSH stimulation: a retrospective study on seven years of beef cattle in vitro embryo production

The aim of this retrospective study was to compare the number of follicles, cumulus oocyte complexes (COCs) and cultured In Vitro Produced (IVP) embryos obtained from 1396 non-stimulated Ovum Pick-up (OPU) sessions on 81 donor animals in a twice weekly OPU scheme. Results were obtained from 640 sessions following FSH-LH superstimulation, on 112 donors subjected to OPU once every 2 weeks. The stimulation protocol started with the insertion of an ear implant containing 3 mg norgestomet (Crestar, Intervet, Belgium) 8 days before puncture (day -8). The dominant follicle was ablated by ultrasound-guided follicle puncture on day -6. On day -3 and day -2, cows were injected with FSH (Ovagen, ICP) twice daily (8 am to 8 pm), i.e. a total dose of 160 mug FSH and 40 mug LG per donor per stimulation cycle. Animals were punctured 48 h after the last FSH injection (day 0). Progesterone implants were removed the next day. Stimulated donor cows were treated with this protocol at 14-day intervals. Follicles were visualized with a Dynamic Imaging ultrasound scanner, equipped with a 6.5 MHz sectorial probe. Follicles were punctured with 55 cm long, 18 gauge needles at an aspiration pressure corresponding to a flow rate of 15 ml/min. Cumulus oocyte complexes were recovered and processed in a routine IVF set-up. Results demonstrate that, expressed per session, FSH stimulation prior to OPU increases production efficiency with significantly more follicles punctured and oocytes retrieved. However, when overall results during comparable 2-week periods are considered (four non-stimulated sessions vs one stimulated), more follicles are punctured and more oocytes are retrieved using the non-stimulated protocol. No significant differences in the number of cultured embryos could be detected, indicating that FSH/LH stimulation prior to OPU might have a positive effect on in vitro oocyte developmental competence as more embryos are cultured with less, presumably better-quality, oocytes.

66 INDIRECT SOLID-SURFACE VITRIFICATION OF MURINE OVARIAN BIOPSIES AND ISOLATED FOLLICLES

Vitrification is a quick and relatively easy cryopreservation technique, but requires high cryoprotectant concentrations and extremely high cooling rates. Possible disadvantages include contamination of specimens with liquid nitrogen (LN2)-born pathogens and compromised post-thaw survival due to cryoprotectant toxicity and/or osmotic shock. The aims of the current research were to vitrify murine ovarian biopsies and isolated follicles using the Cryologic Vitrification Method 1 (CVM1™, Linde Gas Cryoservices, Hedel, The Netherlands), and assess tissue viability after thawing. Ovaries from 5 mice were sectioned into small biopsies (≤0.5 mm3), and ovaries from 5 additional animals were enzymatically digested (collagenase 1 mg mL–1) and filtered over a 100-µm sieve to isolate preantral follicles. Specimens were exposed to a series of vitrification solutions at 25�C, with the final solution consisting of sucrose (0.6 m), ethylene glycol (20%), and DMSO (20%). After 20 to 40 s of equilibration in the final medium, specimens were loaded into 3-µL droplets onto the hook of a plastic Fibreplug™. Droplets were vitrified by contact with the surface of the CVM1 metal block, and pre-cooled by partial submersion in LN2. Fibreplugs were subsequently inserted into pre-chilled straws and plunged into LN2 for 24 h. Specimens were warmed by removing the Fibreplug from the straw; the vitrified droplets were immersed in a series of sucrose solutions (0.3 m, 0.3 m, and 0.2 m) for 5 min at 25�C, and then transferred to PBS supplemented with 5 mg mL–1 BSA. Post-warming viability of isolated follicles and biopsies was assessed by the fluorescent live/dead probe calcein-ethidium. Follicle survival was also appraised in vivo by autotransplantation of either devitrified isolated follicles or biopsies (6 to 12) to the left kidney capsule of the donor animals. The recipients were euthanized 7 days posttransplantation by CO2 inhalation. Grafted tissue was fixed, paraffin-embedded, serially sectioned, and stained with hematoxylin-eosin for histological evaluation. Additional slides were immunohistochemically stained with proliferating cell nuclear antigen (PCNA) to differentiate between growing and non-growing follicles. In all digested samples, more than 80% of thawed isolated follicles were viable, as demonstrated by live/dead staining. In addition, fluorescent probes confirmed the presence of live follicles in 100% of thawed biopsies. In each of the 5 biopsy-transplanted animals, several biopsies survived, and in 3 mice grafted with isolated follicles, vital tissue could be retrieved. Histological examination of the 8 grafts revealed PCNA-positive follicles. These results indicate that indirect solid-surface vitrification of murine ovarian biopsies and isolated preantral follicles is a viable option to slow-rate freezing. The growing follicles in transplanted frozen–thawed tissue confirm the viability of surviving follicles. As specimens do not come into direct contact with LN2 during the vitrification process, the contamination risk is greatly reduced.

128 EFFECT OF OXYGEN TENSION ON INDIVIDUAL IN VITRO BOVINE EMBRYO DEVELOPMENT IN CUMULUS CELL COCULTURE

An in vitro production system, in which a single oocyte can be followed from the moment of retrieval up to the blastocyst stage, would be a valuable tool for studies linking developmental competence and embryo metabolism to immature oocyte quality and follicular environment. Earlier studies revealed that cumulus cell (CC) coculture during IVC enhances individual development, in contrast to group culture. These studies were performed in 5% O2, whereas generally an atmosphere of 20% oxygen is used for coculture with somatic cells. This study aimed to investigate the effect of oxygen tension on individual embryo development in CC coculture. As a control, the effect of oxygen tension on embryo group culture without CC was assessed simultaneously. Therefore, 692 COC from slaughterhouse ovaries (4 replicates) were routinely matured (TCM-199 + 20% serum) and fertilized in groups and then assigned to 4 culture treatments (SOF + 5% serum under oil). Treatments were T1 = 1 zygote in 20 μL + CC in 5% O2; T2 = 1 zygote in 20 μL + CC in 20% O2; T3 = 20 to 25 zygotes in 50 μL in 5% O2; and T4 = 20 to 25 zygotes in 50 μL in 20% O 2. Cleavage, blastocyst, and hatching rates were assessed 2, 8, and 10 days after fertilization, respectively. Possible effects of oxygen tension in individual and group culture were evaluated with binary logistic regression. No interactions between replicate and treatment could be found. Cleavage rates of individual culture showed a tendency (P < 0.1) to be lower in 5% O2 (62.1 v. 71.0% in 20% O2), whereas blastocyst rates were significantly (P < 0.05) higher in 5% O2 (26.6 v. 16.6% in 20% O2). Hatching rates did not differ significantly between the 2 individual treatments (Table 1). Oxygen tension did not have a significant effect on cleavage rates when embryos were cultured in groups, but blastocyst rates were significantly higher in 5% O2 (41.7 v. 27.6% in 20% O2). The group results confirm other studies (Yuan YQ et al. 2003 Theriogenology 59, 1585–1596). In conclusion, higher blastocyst rates can be obtained when an atmosphere of 5% O2 is used for culturing individual zygotes in CC coculture. Because cleavage rates showed a tendency to be higher in 20% O2, an alternating treatment, with 20% O2 until 2 days after fertilization, followed by 5% O2 until the blastocyst stage, should be investigated. Table 1. Cleavage, blastocyst, and hatching rates in 5 and 20% oxygen

Hormonal treatments for increasing the oocyte and embryo production in an OPU–IVP system

The objective was to enhance the inherent developmental ability of bovine oocytes retrieved by ultrasound-guided transvaginal aspiration. Various hormonal regimes were utilized to produce partially matured oocytes in vivo, in order to improve embryo development following IVF. In the first experiment, a two-by-two factorial design was used with FSH (multiple versus single dose) and im administration of LH (yes versus no) 6h prior to OPU. In all protocols (which lasted for nine consecutive weeks), ovarian stimulation was performed in the presence of a CIDR. One FSH administration was adequate for ovarian stimulation (9.33+/-0.7 and 10.14+/-0.7 follicles per cow per OPU session); however, multiple injections increased (P<0.05) follicular response (12.97+/-0.7 and 13.97+/-0.7). In the second experiment, a two-by-two factorial design was used to compare the effects, during ovarian stimulation, of the presence or absence of CIDR, and iv treatment with LH 6h prior to OPU (yes versus no), on oocyte competence (judged by blastocyst development rates following IVF). Presence of CIDR during superstimulation had no effect on the follicular response. Administration of LH 6h prior to OPU increased (P<0.05) the oocytes of higher morphological grades, and in the absence of a CIDR, improved (P<0.05) blastocyst development rate. Treatment with LH, 6h prior to OPU without the use of CIDR during ovarian stimulation, resulted in 2.89+/-0.4 blastocysts per cow per OPU session as compared to 1.56+/-0.4, 1.56+/-0.4 and 1.33+/-0.4 for all other groups. In conclusion, compared to single administration, multiple FSH administration increased (P<0.05) available follicles for aspiration. Moreover, when ovarian stimulation in the absence of CIDR was followed by administration of LH 6h prior to OPU, it increased (P<0.05) the number of blastocysts per OPU session.

180 DEVELOPMENTAL CAPACITY OF SINGLE CULTIVATED EMBRYOS IN SMALL AND BIG DROPLETS

An in vitro production system where a single oocyte can be followed from the ovary to the blastocyst stage would be a useful tool for studies concerning developmental competence or follicular environment. Unfortunately, until now, only low blastocyst rates could be obtained after single embryo production, and there is still discussion about the ideal droplet size. The objective of the present experiment was to compare the developmental competence of single cultivated zygotes in 20- and 500-µL droplets. Cumulus–oocyte complexes were obtained from slaughterhouse ovaries and were matured and fertilized in groups of 100 for 22 h; the presumptive zygotes were divided into 4 groups. In treatment 1, 25 zygotes were transferred into 50 µL of SOF medium supplemented with 5% serum under oil, whereas in treatment 2, 25 zygotes were transferred into 500 µL of medium. Zygotes were cultivated separately in treatments 3 and 4: in treatment 3 in 20 µL of medium under oil and in treatment 4 in 500 µL of medium. Cleavage rates and division stages were assessed after 3 days of cultivation (5% CO2, 5% O2, 90% N2); blastocyst rates were determined after 7 days. Statistical analysis was performed by logistic regression using SAS (PROC LOGISTIC). There was no difference in cleavage rates between the 2 group treatments or between the 2 single treatments. Also, the division stages were not different between the 2 single treatments (16-cell: 2.0 vs. 1.3%; 8-cell: 25.8 vs. 31.6%; 4-cell: 41.2 vs. 38.0%; and 2-cell: 31.0 vs. 29.1% for the 20 µL and the 500 µL droplet sizes, respectively). Group cultivation after 7 days in 50 µL was significantly better than in 500 µL; however, both treatments resulted in significantly higher blastocyst rates compared with the individual cultures in 20 or 500 µL, between which no significant difference could be found. Noteworthy, only 4-cell and 8-cell stages on Day 3 resulted in blastocysts on Day 7 of cultivation. In conclusion, these results indicate that cultivation in groups gives higher blastocyst rates, although the same embryo density is used as in individual cultivation (1 embryo 20 µL in treatments 2 and 3). Moreover, no significant difference could be found between single cultivation in small and big droplets. This is confirmed by the cleavage stages on Day 3, which indicate no difference in timing of cleaving between small and big droplets; time of cleaving is indicative of further developmental capacity. Table 1.Cleavage and blastocyst rates after single and group cultivation

15 EFFECT OF BULL EPIDIDYMIS STORAGE CONDITIONS ON CRYOPRESERVED EPIDIDYMAL SPERM IN VITRO FERTILITY AND LIPID PEROXIDATION STATUS

Although cryopreservation of epididymal sperm has been studied extensively in several species, some factors that could negatively influence its quality are still unknown, such as the storage conditions of the epididymides prior to sperm collection. Studies indicate that the lower the storage temperature, the better the sperm quality after collection (Kaabi et al. 2003 Theriogenology 60, 1249–1259). An additional factor is lipid peroxidation in which sperm membrane resistance against reactive oxygen species (ROS) attacks is an important component. The objective of this experiment was to study whether the epididymis storage temperature following slaughter, as well as the intrinsic resistance against oxidative stress, affects the fertilizing capacity of cryopreserved epididymal bull sperm in vitro. Twelve epididymides (6 bulls) were collected after slaughter and divided into 2 groups, (stored at either 4 or 37�C for 2), after which semen was collected from the caudae epididymides and cryopreserved. Subsequently, one aliquot of the frozen–thawed semen samples was subjected to induced lipid peroxidation with ferrous sulfate and ascorbate (37�C; 2 h), after which tiobarbituric acid-reactive substances (TBARS), as an index of lipid peroxidation, were measured according to a method previously described (Beorlegui et al. 1997 Andrologia 29, 37–42). A second aliquot was used for in vitro fertilization in a routine IVF–IVC setup in duplicate (24-h maturation, SOF culture medium in 5% CO2, 5% O2, and 90% N2). In vitro embryo production results at Day 7 and TBARS levels were statistically analyzed using SAS (SAS Institute, Inc., Cary, NC, USA). No influence of storage temperature was observed at either TBARS level (4�C: 943.6 � 173.4; 37�C: 751.4 � 136.2 ng of TBARS/108 spermatozoa; P = 0.3) or on blastocyst rates (4�C: 23.0 � 2.8; 37�C: 18.7 � 3.6% of blastocysts; P = 0.2). However, the percentage of hatched blastocysts tend to be higher for epididymides stored at 4�C when compared to those stored at 37�C (6.4 � 1.8 and 2.3 � 0.9, respectively; P = 0.06). In addition, a negative correlation was found between TBARS concentrations and blastocyst rates (R = –0.57; P &lt; 0.05). Compared to fresh samples collected from epididymides under the same conditions (unpublished data), levels of TBARS were two- to threefold higher for the cryopreserved sperm, indicating that lipid peroxidation appears to play a role in the decrease in quality of cryopreserved epididymal sperm. In conclusion, temperature during the epididymides short-term storage prior to sperm cryopreservation did not seem to influence the sperms&apos; in vitro fertilizing capacity. On the other hand, an alternative to improve cryopreserved epididymal sperm in vitro fertility (or fertilizing capacity) could be the addition of antioxidants to semen extenders. Further studies are necessary to confirm this hypothesis.

412 VIABILITY OF ENZYMATICALLY ISOLATED BOVINE PRIMORDIAL AND PRIMARY OVARIAN FOLLICLES COLLECTED BY THE BIOPSY PICK-UP TECHNIQUE

Our institution recently developed a new tool for transvaginal, ultrasound-guided collection of ovarian biopsies from living donor cows (Aerts et al. 2005 Theriogenology 64, 947–957). The biopsy pickup (BPU) device consists of a modified needle guidance system, which is equipped with a trocar needle and carries a 60-cm-long true-cut biopsy needle. In a previous experiment, the presence of primordial and preantral follicles in BPU-derived biopsies was demonstrated. As follicular integrity is a prerequisite for further culture or research, the aim of the present study was to assess the viability of enzymatically isolated primordial and primary ovarian follicles collected by the BPU instrument. Four cows were subjected to a one-time BPU procedure. Four cortical biopsies were collected per ovary from each animal. Follicle viability was determined by the dual fluorescent probe technique described by Cortvrindt and Smitz (2001 Fertil. Steril. 75, 588–593). In live cells, calcein-AM is converted into calcein by intracellular esterase enzymes, producing an intense green fluorescence. In dead cells, ethidium homodimer-I is able to penetrate the damaged plasma membrane and, upon binding to nucleic acids, undergo a 40-fold enrichment of fluorescence, thereby producing an intense red signal. Upon retrieval, the biopsies were immersed in HEPES-buffered minimum essential medium (GIBCO, Grand Island, NY, USA) at 4�C. In the laboratory, the tissue samples were transferred to 50-mL conical tubes containing 20 mL PBS supplemented with 1 mg mL-1 collagenase type IA (Sigma-Aldrich NV/SA, Bornem, Belgium) and were incubated in a water bath at 37�C for 60 min. The digestion was terminated by adding an equal volume of cold PBS. The resulting suspension was centrifuged at 300g for 10 min at 8�C. The pellet was resuspended in PBS and transferred to a Petri dish. Each Petri dish was examined under a phase-contrast inverted microscope (Olympus CHX41) equipped with an eyepiece micrometer, and the primordial and primary follicles were collected with a glass micropipette. Isolated follicles were mounted on a slide in 50-�L droplets of PBS containing 2 �mol L-1 calceine-AM and 5 �mol L-1 ethidium homodimer-I (Molecular Probes, Leiden, The Netherlands), and incubated in the dark for 45 min at 37�C. After incubation, the follicles were examined under a fluorescence microscope (Olympus BX61). A total of 95 enzymatically isolated follicles were analyzed for viability with fluorescent probes; 89 (93.7%) of these were viable. Viable follicles were retrieved from all animals. This experiment confirms that viable primordial and primary follicles can be retrieved from living donor cows by the BPU procedure, which makes the technique suited for further culture or research.

Roles of lipid peroxidation and cytoplasmic droplets on in vitro fertilization capacity of sperm collected from bovine epididymides stored at 4 and 34 degrees C

Sperm recovery from the cauda epididymis can be very advantageous, for example, in case of the unexpected death of a genetically highly valuable animal, for preserving endangered species, or when the collection of sperm by other means becomes impossible. Studies indicate that epididymides stored at cooler temperatures result in better quality sperm. One of the factors that could negatively affect sperm viability during storage is lipid peroxidation, in which the sperm membrane's ability to resist attacks by reactive oxygen species (ROS) plays an important role. Another factor is the presence of cytoplasmic droplets, which appear in high numbers in epididymal sperm, and are known to influence oxidative stress. The objectives of this study were: to determine whether the post-slaughter storage temperature of the epididymis would effect the sperm membrane's resistance to lipid peroxidation and/or the sperm cell's fertilizing capacity in vitro and to elucidate the role played by the cytoplasmic droplets. Forty-eight testicles with epididymides (24 bulls) were collected following slaughter, and divided into two groups. One testicle from each pair was stored at 4 degrees C, and the other at 34 degrees C, for 2h, after which sperm was collected from the caudae epididymides. Sperm concentration was measured, and an aliquot containing 10(8)sperm was subjected to induced lipid peroxidation with ferrous sulphate and ascorbate (37 degrees C, 2h). Subsequently, thiobarbituric acid reactive substances (TBARS), as an index of lipid peroxidation, were measured. A second aliquot of the same sample was used in a routine in vitro fertilization performed in duplicate. Sperm from caudae epididymides stored at 34 degrees C resulted in lower rates of total blastocyst formation and had a higher percentage of distal droplets, when compared to sperm from epididymides stored at 4 degrees C (21.2+/-2.42 and 71.8+/-4.7% versus 33.5+/-1.8 and 23.7+/-4.7%, respectively, P<0.05). Storage temperature had no effect on TBARS levels. For samples stored at 4 degrees C, TBARS were negatively correlated with distal droplets (r=-0.63, P<0.05) and positively correlated with proximal droplets (r=0.42, P<0.05). In conclusion, our results show that short-term storage of epididymides at 4 degrees C provided sperm of higher quality and in vitro fertilizing capacity than storage at 34 degrees C. Although resistance to oxidative stress could not be shown to directly influence these results, distal sperm droplets that appeared in high numbers in the cooled epididymal sperm samples, may have exerted an antioxidant effect. We hypothesize that this protection against ROS is one of the functions of distal sperm droplets in the epididymis.

Seasonal variation in semen quality in Bos indicus and Bos taurus bulls raised under tropical conditions

In the present study, we tested the hypothesis that Bos taurus taurus bulls have greater reactive oxygen species (ROS) and lower activity of antioxidant enzymes in their semen than Bos taurus indicus bulls. Sixteen Simmental bulls (B. t. taurus) and 11 Nelore bulls (B. t. indicus) were managed extensively in a tropical environment. Semen was collected twice annually (summer and winter) for 2 consecutive years. Simmental bulls had significantly higher percentages of major sperm defects during the summer than the winter (20.3+/-3.1% versus 12.2+/-2.4%, respectively; mean+/-S.E.M.). There was an interaction of breed and season for minor sperm defects (P=0.037; highest in Nelore bulls in the summer) and an effect of season on total defects (P=0.066; higher in summer). To evaluate oxidative damage, malondialdehyde (lipid-peroxidation metabolite) concentrations were indirectly measured by semen concentrations of thiobarbituric acid reactive substances (TBARS); these were higher in summer than in winter (728.1+/-79.3ng/mL versus 423.8+/-72.6ng/mL, respectively; P=0.01). Glutathione peroxidase/redutase (GPx) activity in semen was higher in Simmental versus Nelore bulls (741.6+/-62.1 versus 510.2+/-62.8; P<0.01). However, superoxide dismutase (SOD), another antioxidant enzyme, was not significantly affected by breed or season. There were correlations between TBARS and sperm primary defects during the summer for both Simmental and Nelore bulls (r=0.59, P=0.021 and r=0.40, P=0.034, respectively), and between SOD and primary defects during summer for Simmental bulls only (r=-0.51, P=0.041). In conclusion, there was a higher level of lipid peroxidation (ROS) in semen of Simmental versus Nelore bulls; apparently the higher GPx activity in Simmental bulls was insufficient to avoid damage that occurred concurrent with increased ROS production during the summer.

Evaluation of epididymal semen quality using the Hamilton–Thorne analyser indicates variation between the two caudae epididymides of the same bull

Epididymal semen is being more often considered as a potential source of valuable genes for genome resource banks. To utilize this resource as efficiently as possible, storage and freezing fertility and preservation characteristics of epididymal semen have to be examined. Because semen quality should be assessed as objectively as possible, we introduced computer assisted sperm analysis (CASA) of epididymal bull semen. The aims of this study were: to determine the quality of fresh cauda epididymal bull sperm, conventionally and by CASA (Hamilton-Thorne Ceros 12.1); to compare epididymal sperm movement with the motion characteristics of ejaculated semen; and to investigate whether equality of semen characteristics exists between both caudae epididymides of the same bull. In experiment 1, it is shown that epididymal sperm has a lower motility (total: 48.7% versus 79.9%, p < 0.0001 and progressive: 34.4% versus 58.4%, p < 0.0001) and moves less straight (80.5% versus 84.5%, p < 0.0009) with a higher amplitude (6.1 microm versus 5.0 microm, p < 0.0001) than ejaculated semen. The epididymal straight line velocity (85.2 microm/s versus 98.3 microm/s, p < 0.0001) is lower, but the curvilinear velocity (173.5 microm/s versus 156.4 microm/s, p < 0.0001) is higher than those of ejaculated semen. The data in experiment 2 are analysed to determine equality, rather than to find a difference. They illustrate that mean differences, for most semen parameters, between the semen from paired caudae epididymides, deviated more than 20% from the average values of these parameters from all bulls; the exceptions (those parameters within 20% of the average for all bulls) were the percentage of live spermatozoa, the linearity of sperm movement, the weights of testis and epididymis, the weights of the cauda epididymis alone, the volumes, and the amplitudes of movement of the semen (p < 0.05). The mean differences between the percentage of live spermatozoa and the amplitude of movement of the epididymal semen of both epididymides of one bull, were the only values smaller than 10% of the average value of this parameter (p < 0.05). This implies that sperm from one cauda epididymis should not be used as a control for the other because, for most of the semen parameters (concentration, morphology, motility, and beat cross frequency), equality between caudae epididymides of the same bull could not be established.

Comparison of different transvaginal ovum pick-up protocols to optimise oocyte retrieval and embryo production over a 10-week period in cows

The objective was to develop a simple and effective ovum pick-up (OPU) protocol for cows, optimised for oocyte harvest and subsequent in vitro embryo production (IVP). Five protocols differing in collection frequency, dominant follicle removal (DFR) and FSH stimulation were tested on groups of three cows each, over an interval of 10 consecutive weeks. Performance was evaluated on per OPU session, per week and pooled (3 cowsx10weeks) basis. Among the non-stimulated groups, on a per cow per session basis, once- or twice-weekly OPU had no effect on the mean (+/- S.E.M.) number of follicles aspirated, oocytes retrieved and blastocysts produced (0.6+/-0.8 and 0.7 +/- 0.7, respectively). However, DFR 72 h prior to OPU almost doubled blastocyst production (1.2 +/- 1.3). In stimulated groups, FSH treatment (80 mg IM and 120 mg SC) was given once weekly prior to OPU. Treatment with FSH, followed by twice-weekly OPU, failed to show any synergistic effect of FSH and increased aspiration frequency. When FSH was given 36 h after DFR, followed by OPU 48 h later, more (P < 0.05) follicles (16.0 +/- 5.0), oocytes (10.6 +/- 4.5) and embryos (2.1 +/- 1.2) were obtained during each session, but not on a weekly basis. Pooled results over 10 weeks showed an overall improved performance for the treatment groups with twice-weekly OPU sessions, due to double the number of OPU sessions performed. However, the protocol that consisted of DFR, FSH treatment and a subsequent single OPU per week, was the most productive and cost-effective, with potential commercial appeal.

307 EFFECT OF BULL EPIDIDYMIS STORAGE CONDITIONS ON SPERM RESISTANCE AGAINST LIPID PEROXIDATION AND SUBSEQUENT IN VITRO EMBRYO PRODUCTION

Sperm recovery from the cauda epididymis can be a usefull tool in case of unexpected death of genetic high-value animals or endangered species or when the collection of sperm by other means becomes impossible. Studies indicate that the lower the temperature of epididymis storage, the better the sperm quality after collection (Kaabi et al. 2003 Theriogeneology 60, 1249-1259). One of the main factors that can negatively affect sperm viability during storage is lipid peroxidation, where sperm membrane resistance against reactive oxygen species (ROS) attacks is an important factor. The objective of this experiment was to study whether the temperature of epididymis storage following slaughter would have an influence on the membrane's resistance against lipid peroxidation and on the sperm cell's fertilizing capacity. Sixteen epididymides (from eight bulls) were collected after slaughter and divided into two groups, one stored at 4�C and the other at 37�C for 2 h, after which semen was collected from the caudae epididymides. Sperm concentration was measured and an aliquot containing 108 sperm cells was submitted to induced lipid peroxidation with ferrous sulfate and ascorbate (37�C; 2 h). Subsequently, thiobarbituric acid reactive substances (TBARS), as an index of lipid peroxidation, were measured according to a method previously described (Beorlegui et al. 1997 Andrologia 29, 37-42). A second aliquot of the sample was used for fertilization in a routine IVF-IVC set up in duplicate (24-h maturation, SOF culture medium in 5% CO2, 5% O2, and 90% N2). In vitro embryo production and level of TBARS were statistically analyzed using SAS (SAS Institute, Inc., Cary, NC, USA). TBARS levels were transformed to logarithm form in order to obey the residue normality being analyzed using PROC GLM. The percentage of blastocysts was analyzed using the Wilcoxon test. When compared to the samples stored at 4�C, semen of caudae epididymides stored at 37�C showed higher levels of TBARS and lower mean blastocyst rates (324.7 � 59.6 and 36.6 � 1.6 vs. 466.9 � 67.9 ng of TBARS/108 spermatozoa and 28.8 � 2.9%, respectively; P < 0.05). A negative correlation was found between TBARS and blastocyst rates (R = -0.43). The lower quality of sperm collected from epididymides maintained at higher temperatures may be related to a decrease in sperm resistance against lipid peroxidation which would further impair sperm fertilizing capacity. However, further studies are necessary in order to study the effect of temperature on the sperm membrane lipid profile, because the content of polyunsaturated fatty acids may be affected by temperature; this is an important factor relative to sperm membrane lipid peroxidation susceptibility (Ollero et al. 2000 Mol. Reprod. Dev. 55, 326-334). Another important factor is the epididymal environment because interactions between the sperm membrane and its surroundings can play an important role on the membrane's antioxidant protection.

Comparison of embryo quality in high-yielding dairy cows, in dairy heifers and in beef cows

The purpose of this study was to compare embryo quality of lactating Holstein Friesian cows (LHFC), non-lactating Holstein Friesian heifers (NLHFH) and Belgian Blue beef cows (BB) and to identify factors that are associated with embryo quality in LHFC and NLHFH. After superovulation and embryo recovery at Day 7, embryos (n=727 from 47 LHFC, 27 NLHFH and 50 BB) were scored morphologically for quality, colour and developmental stage. Blood samples and data concerning parity, age, milk production and management were collected. Data were compared univariably between the three groups. A multivariable regression model was built with quality and colour of the LHFC and NLHFH embryos as dependent variables. Only 13.1% of LHFC embryos were categorized as excellent compared to 62.5% and 55.0% of the embryos in NLHFH and BB, respectively. Almost none of the NLHFH or BB embryos displayed a dark appearance of the cytoplasm compared to 24.1% of the LHFC embryos. Only 4% of all LHFC embryos reached blastocyst stage compared to 23.2% and 17.3% in NLHFH and BB. Based on the multivariable regression analysis, "physiological status" (lactating or not) together with the serum total protein concentration of LHFC and NLHFH, was significantly associated with embryo quality and colour. Thus, LHFC display an inferior embryo quality compared to NLHFH and BB. Producing milk or not seems to be significantly associated with embryo quality. Therefore, reduced embryo quality on Day 7 following AI, could be an important factor in the subfertility problem in modern high-yielding dairy cows.

Characterisation of low, medium and high responders following FSH stimulation prior to ultrasound-guided transvaginal oocyte retrieval in cows

In human IVF, the concept of 'low responders' is well known and generally defined as women with poor-response to gonadotrophin stimulation in a previous induction cycle. The objective of this retrospective study is to describe and characterise the concepts of 'low-, medium-, and high-response' and 'low, medium, and high responders' in bovine-assisted reproduction by analysing the OPU-IVF results obtained following 665 gonadotrophin-stimulated sessions conducted in 112 animals, nearly all of which were previously unsuccessful in traditional multiple ovulation and embryo transfer (MOET) programs. They were submitted to OPU and IVP between 1999 and 2003. In reference to these 665 OPU sessions, categories of response were defined based on the overall mean+/-S.D. follicles aspirated and COC obtained i.e., for follicles 14.7+/-9.8 and for COCs 11.7+/-8.1. So arbitrary cut-off values to define the categories of sessions were for follicles 5 and 25, and for COC 4 and 20. The three categories for follicles punctured in one session were therefore follicle low-response (FLR)<or=5 follicles, follicle medium-response (FMR) 6-24 follicles or follicle high-response (FHR)>or=25 follicles and for COCs recovered in one session COC low-response (CLR)<or=4 COC, COC medium-response (CMR) 5-19 COC or COC high-response (CHR)>or=20 COC. In addition, four categories of animals were also defined: (1) a low responder animal (LRA) had at least one OPU session in which FLR and CLR were observed (genuine low-response, see Section ); these animals did not have any high-response sessions, (2) a medium responder animal (MeRA) had only medium-responses, (3) a high responder animal (HRA) had at least one OPU session in which FHR and CHR were observed; these animals did not have any low-response sessions, and (4) mixed responder animals (MiRA) had both low and high-responses. Finally, we distinguished biological (animals) and technical (recovery rate and ultrasound resolution) causes of response differences. In 'low, high, medium and mixed reponders,' different results were obtained (p<0.05): mean follicle numbers (8.8+/-4.8a, 22.4+/-10.5c, 13.2+/-5.2b,15.1+/-10.2d), COC numbers (6.3+/-3.9a, 18.5+/-8.2c, 10.4+/-4b, 12.0+/-8.3d), embryo numbers (1.8+/-2.1a, 5.6+/-4.9c, 2.5+/-2.7b, 3.5+/-3.8d) and also for recovery rate (72%a, 83%b,79%, 79%) and percentage embryo development (29%, 30%a, 24%b, 29%). In conclusion, the results of this study demonstrate that variability in OPU results has technical (ultrasound resolution and recovery rate) as well as biological (animal) aspects. Selection of animals with extreme (high or low) follicle and COC production results allows us to distinguish three populations: 'low, medium, and high responders' to FSH stimulation.

Puncture of immature ovarian follicles in bovine assisted reproduction

Transvaginal, ultrasound-guided follicular aspiration (OPU) is the method of choice to retrieve immature oocytes from highly valuable living donor cows for in vitro embryo production. In the introduction, we comment on general techniques of oocyte retrieval. In the second part, we describe the OPU technique from a technical point of view, and we discuss the factors that influence the quality and quantity of the oocytes retrieved. Firstly, there is a group of technical factors such as aspiration procedure, needle type, and the influence of the aspiration vacuum on cumulus oocyte complex morphology. Secondly, there is a huge group of biological influences, e.g. hormonal stimulation prior to follicle puncture, timing of the procedure relative to the estrous cycle, age, breed, and physiological condition of the donor. Subsequently, the use of OPU in combination with in vitro embryo production for the treatment of bovine sterility patients is discussed, as a way to obtain additional offspring from donors with impaired fertility. Reports on donor animal health and reproductive performance following repeated OPU are commented upon. Finally, future research possibilities related to the OPU technique are discussed. Additional gain is expected from the development of better ultrasound equipment, permitting optimal visualization of the smallest follicles. In addition, OPU equipment will be used for related purposes, such as repeated retrieval of ovarian biopsies, and the injection of local ovarian mediators, which will permit to study local paracrine hormonal effects, and their influence on oocyte quality.

Metabolic changes in follicular fluid of the dominant follicle in high-yielding dairy cows early post partum

Characteristics of the intrafollicular environment to which the preovulatory oocyte is exposed may be one of the major factors determining subsequent fertility. The aim of our study was to examine to what extent metabolic changes that occur in early post partum high-yielding dairy cows are reflected in the follicular fluid (FF) of the dominant follicle (>8 mm). Nine blood samples were taken per cow from nine high-yielding dairy cows between 7 days before and 46 days after parturition. From Day 14 post partum on and together with blood sampling, FF samples of the largest follicle were collected from the same cows by means of transvaginal follicle aspiration. Serum and FF samples were analyzed using commercial clinical and photometric chemistry assays for glucose, beta-hydroxybutyrate (beta-OHB), urea, total protein (TP), triglycerides (TG), non-esterified fatty acids (NEFA) and total cholesterol (TC). All cows lost body condition during the experimental period (0.94+/-0.09 points) illustrating a negative energy balance during the experimental period. In FF, glucose concentrations were significantly higher and the TP, TG, NEFA and TC concentrations were significantly lower than in serum (P<0.05). The concentrations of glucose, beta-OHB, urea and TC in serum and in FF changed significantly over time (P<0.05). Throughout the study, changes of all metabolites in serum were reflected by similar changes in FF. Especially for glucose, beta-OHB and urea the correlations were remarkably high. The results from the present study confirm that the typical metabolic adaptations which can be found in serum of high-yielding dairy cows shortly post partum, are reflected in follicular fluid and, therefore, may affect the quality of both the oocyte and the granulosa cells.

A comparison of a mechanical sector and a linear array transducer for ultrasound-guided transvaginal oocyte retrieval (OPU) in the cow

A comparison was made between a linear array and a mechanical multiple angle sector (MAP) transducer for ultrasound-guided transvaginal oocyte retrieval (ovum pick-up, OPU) in the cow. The ovaries of five dairy cows were punctured, in a twice-weekly OPU program lasting for 4 weeks, using two different 5.0-MHz transducers equipped with an identical disposable needle-guidance system. Both ovaries were visualized using each transducer before puncture and the number of follicles with a diameter of less than 5 mm (small) and with a diameter equal to or greater than 5 mm (large) was recorded. Subsequently, one ovary of the pair was punctured guided by the MAP, while the other was punctured using the linear array transducer. During the next puncture session on a given animal, the two systems were switched and used on the alternate ovary in a crossover design. Parameters assessed for each system were: the total number of follicles visualized in each diameter class, and the total number of retrieved oocytes per cow. A significant difference was found for the ability to visualize smaller follicles in favor of the MAP transducer, with an average visualization of 71.6 +/- 30.3 small follicles per cow during the 4-week trial period, compared to 59.8 +/- 25.7 for the linear array transducer (t-test for paired samples, P = 0.007). No differences were found in the visualization of large follicles. A numerically greater number of oocytes were retrieved using the MAP transducer, compared to the linear array, (averages of 14.2 +/- 7.2 versus 7.4 +/- 6.1, respectively), although these differences were not statistically significant. In conclusion, both systems can be effectively used for oocyte retrieval in the cow, however, the MAP transducer demonstrated superior visualization of small follicles.

Metabolite and ionic composition of follicular fluid from different-sized follicles and their relationship to serum concentrations in dairy cows

Metabolic changes in blood serum may be reflected in the biochemical composition of follicular fluid and could indirectly influence oocyte quality. The purpose of this study was to examine the biochemical composition of follicular fluid harvested from different-sized follicles and its relationship with that of blood serum in dairy cattle. Following slaughter, blood samples were collected from dairy cows n=30 and follicular fluid aspirated from three size classes of non-atretic follicles (<4 mm, 6-8 mm and >10 mm diameter). Samples remained independent between cows and between size classes within cows. Serum and follicular fluid samples were assayed using commercial clinical and photometric chemistry assays for ions (sodium, potassium and chloride) and metabolites (glucose, beta-hydroxybutyrate (beta-OHB), lactate, urea, total protein, triglycerides, non-esterified fatty acids (NEFA) and total cholesterol). Results showed that follicular fluid concentrations of glucose, beta-OHB and total cholesterol increased from small to large follicles and decreased for potassium, chloride, lactate, urea and triglycerides. There was a significant concentration gradient for all variables between their levels in serum and follicular fluid (P<0.05). Significant correlations were observed for chloride (r=0.40), glucose (r=0.56), beta-OHB (r=0.85), urea (r=0.95) and total protein (r=0.60) for all three follicle size classes and for triglycerides (r=0.43), NEFA (r=0.50) and total cholesterol (r=0.42) for large follicles (P<0.05). The results from the present study suggest that the oocyte and the granulosa cells of dairy cows grow and mature in a biochemical environment that changes from small to large follicles. Furthermore, the significant correlation between the composition of serum and follicular fluid for the above-mentioned metabolites suggests that metabolic changes in serum levels will be reflected in the follicular fluid and, therefore, may affect the quality of both the oocyte and the granulosa cells.