Bovine embryo development after IVF with spermatozoa having abnormal morphology

Can in vitro embryo production be estimated from semen variables in Senepol breed by using artificial intelligence?

Thoroughly analyzing the sperm and exploring the information obtained using artificial intelligence (AI) could be the key to improving fertility estimation. Artificial neural networks have already been applied to calculate zootechnical indices in animals and predict fertility in humans. This method of estimating the results of reproductive biotechnologies, such as in vitro embryo production (IVEP) in cattle, could be valuable for livestock production. This study was developed to model IVEP estimates in Senepol animals based on various sperm attributes, through retrospective data from 290 IVEP routines performed using 38 commercial doses of semen from Senepol bulls. All sperm samples that had undergone the same procedure during sperm selection for in vitro fertilization were evaluated using a computer-assisted sperm analysis (CASA) system to define sperm subpopulations. Sperm morphology was also analyzed in a wet preparation, and the integrity of the plasma and acrosomal membranes, mitochondrial potential, oxidative status, and chromatin resistance were evaluated using flow cytometry. A previous study identified three sperm subpopulations in such samples and the information used in tandem with other sperm quality variables to perform an AI analysis. AI analysis generated models that estimated IVEP based on the season, donor, percentage of viable oocytes, and 18 other sperm predictor variables. The accuracy of the results obtained for the three best AI models for predicting the IVEP was 90.7, 75.3, and 79.6%, respectively. Therefore, applying this AI technique would enable the estimation of high or low embryo production for individual bulls based on the sperm analysis information.

Aniline blue test for sperm protamination-a valuable add-on to the bull breeding soundness evaluation

Bull breeding soundness evaluation (BBSE) is the most common procedure used to predict bull potential fertility. However, the use of traditional methods for semen evaluation can affect its reliability. The inclusion of additional advanced test in BBSE may increase its accuracy. This study aimed to investigate the correlation between the degree of sperm protamination and BBSE main parameters of scrotal circumference (SC), progressive motility (PM), morphologically normal sperm (NS), and different categories of morphological defects. In addition, to determine the correlation between the three methods used for protamine assessment, five Brangus bulls were subjected to the BBSE. Semen samples were collected via electro-ejaculation and evaluated using traditional methods. Three different methods were used to determine the degree of sperm protamination: aniline blue (AB) staining, chromomycin A3 staining with fluorescent microscope (CMA3-FLM), and CMA3 with flow cytometry (CMA3-FCM). Sperm protamine deficiency assessed using the three methods exhibited significant differences among bulls according to their classification by BBSE, and showed significant negative correlation with semen quality parameters of NS and PM. A significant positive correlation was found between AB positivity and morphological abnormalities. The three methods used for protamine assessment also revealed significant positive correlations. Among the three tests, AB staining was the cheapest and easiest test that offers an objective assessment method for sperm protamination. Hence, it can be concluded that the assessment of protamination using AB staining test might serve as an additional valuable parameter or a replacement whenever detail sperm motility and morphology analyses in conducting BBSE to predict bull fertility are not possible.

Dissecting the relationship between artificial insemination success and bull semen quality in the arid region of Tiaret (Algeria)

Despite being subject to prior assortment, frozen bull sperms commercialized for artificial insemination may present certain morphological defects. The present study aims (i) to assess the artificial insemination success of the most common cattle breeds in Algeria and (ii) to evaluate the possible effects of commercialized bull’s semen quality on this operation. Artificial insemination was assessed through four years of field monitoring by inseminating different cattle breeds of normal fertility. However, semen quality was evaluated using light microscopy by measuring viability, motility, and morphological abnormalities of spermatozoa. Field study revealed a high percentage of normal calving in red and white Holstein breed (44.83 %) against the high percentage of embryonic mortality (46.43 %) and calving with a malformation (10.71 %) in Montbéliarde breed. Semen quality assessment revealed that sperm viability and motility were higher in Holstein breeds than in Montbéliarde. Furthermore, significant differences between semen bulls were found in the proportion of abnormal spermatozoa; a higher rate of sperms with the abnormal head was observed in the black and white Holstein breed (69.3±10.98 %). However, the percentage of abnormal sperms with tail defects was higher in the Montbéliarde breed (67.5±10.74 %). The lousy quality of the selected semen and/or the poor handling and storage of frozen semen constitute a determinant factor that hinders the success of artificial insemination in the arid region of Tiaret (Algeria).

The effects of differing nutritional levels and body condition score on scrotal circumference, motility, and morphology of bovine sperm

Bulls often experience various levels of nutrient availability throughout the year. Nutritional management is a critical factor on overall ejaculate composition and the ability to get females pregnant. We hypothesized that differing nutritional levels and body condition score (BCS) affect reproductive fertility parameters in bulls. Mature Angus bulls (n = 11) were individually housed and randomly assigned to one of two dietary regimens: 1) over-fed (n = 5) or 2) restricted (n = 6). Bulls were fed the same ration at different volumes to achieve desired effects resulting in eight individual treatments: gain to an over-fed body condition score ([BCS]; GO), gain after nutrient restriction (GR), loss after an over-fed BCS (LO), loss from nutrient restriction (LR), maintenance at ideal adiposity (BCS = 6) after overfeeding (IMO), maintenance at ideal adiposity after nutrient restriction (IMR), maintenance at an over-fed BCS (BCS = 8; MO), and maintenance at a restricted BCS (BCS = 4; MR). Body weight (BW) and BCS were recorded every 2 wk to monitor bull weight and BCS changes. Scrotal circumference was measured every 28 d. Body fat and sperm motility and morphology were evaluated every 84 d. Scrotal circumference, motility, and morphology were normalized to the initial value of each bull. Thus, allowing the individual bull to serve as a control. Statistical analyses were conducted with PROC GLIMMIX of SAS as a complete randomized design to determine if treatment influenced BW, BCS, scrotal circumference, motility, morphology, and adipose thickness. Scrotal circumference (P < 0.001) had the least amount of deviation from initial during the LR (0.29 ± 0.44) treatment and the greatest during the MO (3.06 ± 0.44), LO (2.28 ± 0.44), MR (2.43 ± 0.44), GR (3.03 ± 0.44), and IMR (2.91 ± 0.44) treatments. Sperm motility was not affected by nutritional treatments (P = 0.55). Both head and total defects of sperm differed (P = 0.02) due to nutritional treatments. Increased head abnormalities occurred during the LO (37.60 ± 8.61) treatment, with no differences between the other treatments. Total defects increased during the LO (43.80 ± 9.55) treatment with similar increases in bulls during the GR (29.40 ± 9.55) and IMR (35.60 ± 9.55) treatments. In conclusion, male fertility was impacted when a deviation from a BCS of 6 occurred which could be detrimental to reproductive and beef production efficiency.

Effects of breed and ejaculate volume on sperm morphology and semen parameters of boars

The aim of the study was to determine the relation between the semen quality, frequency of sperm defects, sperm dimensions and shape, and the ejaculate volume of Large White and Landrace boars. A total of 648 ejaculates collected from 31 Large White and 30 Landrace boars were divided into three groups according to the criterion of the ejaculate volume. In this study Landrace boars produced ejaculates with higher volume, sperm concentration, and total numbers of spermatozoa than Large White boars. Landrace boars also showed a lower frequency of sperm with morphological abnormalities (P < 0.05). Landrace boars sperm had larger heads, which were by 0.15 μm longer, and by a larger perimeter and area (P < 0.05). Landrace boar spermatozoa also had a longer flagellum and were generally larger and by 2.07 μm longer than Large White boar sperm (P < 0.05). Significant differences were also found in the shape of sperm of the two breeds (P < 0.05). Landrace boars sperm had more elongated heads, and the ratio of head size to flagellum length was lower than in Large White boars sperm (P < 0.05). Sperm from ejaculates with low volume had a shorter flagellum and a greater head length/flagellum length ratio than sperm from medium- and high-volume ejaculates (P < 0.05).

Amelioration of heat stress-induced damage to testes and sperm quality

Heat stress (HS) occurs when temperatures exceed a physiological range, overwhelming compensatory mechanisms. Most mammalian testes are ∼4-5 °C cooler than core body temperature. Systemic HS or localized warming of the testes affects all types of testicular cells, although germ cells are more sensitive than either Sertoli or Leydig cells. Increased testicular temperature has deleterious effects on sperm motility, morphology and fertility, with effects related to extent and duration of the increase. The major consequence of HS on testis is destruction of germ cells by apoptosis, with pachytene spermatocytes, spermatids and epididymal sperm being the most susceptible. In addition to the involvement of various transcription factors, HS triggers production of reactive oxygen species (ROS), which cause apoptosis of germ cells and DNA damage. Effects of HS on testes can be placed in three categories: testicular cells, sperm quality, and ability of sperm to fertilize oocytes and support development. Various substances have been given to animals, or added to semen, in attempts to ameliorate heat stress-induced damage to testes and sperm. They have been divided into various groups according to their composition or activity, as follows: amino acids, antibiotics, antioxidant cocktails, enzyme inhibitors, hormones, minerals, naturally produced substances, phenolic compounds, traditional herbal medicines, and vitamins. Herein, we summarized those substances according to their actions to mitigate HS' three main mechanisms: oxidative stress, germ cell apoptosis, and sperm quality deterioration and testicular damage. The most promising approaches are to use substances that overcome these mechanisms, namely reducing testicular oxidative stress, reducing or preventing apoptosis and promoting recovery of testicular tissue and restoring sperm quality. Although some of these products have considerable promise, further studies are needed to clarify their ability to preserve or restore fertility following HS; these may include more advanced sperm analysis techniques, e.g. sperm epigenome or proteome, or direct assessment of fertilization and development, including in vitro fertilization or breeding data (either natural service or artificial insemination).

Influence of Sexcel™ (gender ablation technology) gender-ablated semen in fixed-time artificial insemination of beef cows and heifers

Previous research has indicated that gender-sorted semen has decreased conception rates compared to conventional semen. A new method to skew the gender ratio of semen has been developed that does not use traditional sorting technology. Thus, the objective of this study was to evaluate the use of gender-ablated semen in a fixed-time AI protocol. Beef heifers and cows (n = 878) from six herds were synchronized with the 7-d CO-Synch plus CIDR protocol, and artificially inseminated (AI) after CIDR removal (cows 60-66 h; heifers 52-56 h). Estrus detection aids were applied at CIDR removal and estrus activity was determined at time of AI. Animals remained separated from bulls for at least 10 d after AI. Pregnancy success and fetal age were determined between d 28 and 70 after AI. Semen from five sires was utilized in this study, with two sires used in each herd. Sire 1 was used in all herds and the use of the second sire varied by herd (both conventional and gender-ablated semen from each sire was used in each herd). Data were analyzed using the GLIMMIX procedure in SAS and included the influence of semen type, estrus expression, semen type by estrus expression, dam age, and sire in the model. Herd was included as a random variable. Overall, conventional semen had greater conception rates compared to gender-ablated semen (P < 0.01; 67% vs 52%), and cows that had fully activated patches and partially activated patches had greater conception rates compared to animals that had not exhibited estrus (P < 0.01; 69%, 65%, and 45%). There was no semen type by estrus expression interaction (P = 0.24). Conception rates tended to be greater for conventional semen among animals that had activated patches (P = 0.06; 73% vs 65%) and partially activated patches (P = 0.06; 72% vs 59%). Conception rates were greater for conventional semen (P < 0.01; 56% vs 33%) among animals that did not exhibit estrus. There was no effect of dam age (P = 0.40) or sire (P = 0.92) on conception rates. In conclusion, Sexcel™ gender-ablated semen can successfully be used in fixed-time AI protocols among animals that exhibit estrus, but caution should be used among animals that do not exhibit estrus.

Selected sperm traits are simultaneously altered after scrotal heat stress and play specific roles in in vitro fertilization and embryonic development

Improvements in the estimation of male fertility indicators require advances in laboratory tests for sperm assessment. The aims of the present work were (1) to apply a multivariate analysis to examine sperm set of alterations and interactions and (2) to evaluate the importance of sperm parameters on the outcome of standard IVF and embryonic development. Bulls (n = 3) were subjected to scrotal insulation, and ejaculates were collected before (preinsulation = Day 0) and through 56 days (Days 7, 14, 21, 28, 35, 42, 49, and 56) of the experimental period. Sperm head morphometry and chromatin variables were assessed by a computational image analysis, and IVF was performed. Scrotal heat stress induced alterations in all evaluated sperm head features, as well as cleavage and blastocyst rates. A principal component analysis revealed three main components (factors) that represented almost 89% of the cumulative variance. In addition, an association of factor scores with cleavage (factor 1) and blastocyst (factor 3) rates was observed. In conclusion, several sperm traits were simultaneously altered as a result of a thermal insult. These sperm traits likely play specific roles in IVF and embryonic development.

Altered chromatin condensation of heat-stressed spermatozoa perturbs the dynamics of DNA methylation reprogramming in the paternal genome after in vitro fertilisation in cattle

Shortly after penetration of the oocyte, sperm DNA is actively demethylated, which is required for totipotent zygotic development. Aberrant DNA methylation is thought to be associated with altered chromatin condensation of spermatozoa. The objectives of this study were to investigate the dynamics of DNA methylation reprogramming in the paternal pronucleus and subsequent fertilisation potential of heat-stressed bull spermatozoa having altered chromatin condensation. Hence, bovine zygotes (n=1239) were collected at three different time points (12, 18 and 24h post insemination, hpi), and stained with an antibody against 5-methylcytosine. Fluorescence intensities of paternal and maternal pronuclei were measured by ImageJ. DNA methylation patterns in paternal pronuclei derived from heat-stressed spermatozoa did not differ between time points (P>0.05), whereas control zygotes clearly showed demethylation and de novo methylation at 18 and 24hpi, respectively. Moreover, heat-stressed spermatozoa showed a highly reduced (P<0.01) fertilisation rate compared with non-heat-stressed or normal control spermatozoa (53.7% vs 70.2% or 81.5%, respectively). Our data show that the normal pattern of active DNA demethylation followed by de novo methylation in the paternal pronucleus is perturbed when oocytes are fertilised with heat-stressed spermatozoa, which may be responsible for decreased fertilisation potential.

High resistance of Acropora coral gametes facing copper exposure

Pollution by heavy metals remains today an important threat to the health of humans and ecosystems, but there is still a paucity of data on the response of early life stages of key organisms. In this context, the present work assessed the fertilization success rate of two Acropora species (A. cytherea and A. pulchra) from the French Polynesia reefs exposed to six increasing copper concentrations in seawater. The two species showed a relatively high tolerance to copper (4h30-EC50 was 69.4 ± 4.8 μg L(-1) and 75.4 ± 6.4 μg L(-1) for A. cytherea and A. pulchra, respectively). As Cu concentration increases, an increasing proportion of deformed embryos was recorded (67.6% and 58.5% for A. cytherea and A. pulchra, respectively, at 220 μg Cu L(-1)). These results demonstrated thus, that high levels of copper could negatively impair the normal fertilization process of coral gametes and therefore alter the renewal of coral populations. Since the two Acropora species investigated in this study displayed a high resistance to copper, these results should be considered in the context of multiple stressors associated with climate change, where rising temperature or ocean acidification may significantly exacerbate copper toxicity.

Bovine spermatozoa react to in vitro heat stress by activating the mitogen-activated protein kinase 14 signalling pathway

Heat stress has long been recognised as a cause of subfertility in farm animals. The objectives of the present study were to elucidate the effect of heat stress on sperm function and involvement of the mitogen-activated protein kinase (MAPK) 14 signalling pathway. Spermatozoa incubated for 4 h at a physiological temperature (38.5°C) exhibited significantly (P < 0.05) reduced motility, plasma membrane integrity and mitochondrial potential compared with non-incubated spermatozoa; the reductions in these parameters were more severe following incubation at a hyperthermic (41°C) temperature (P < 0.01). Percentages of fertilisation and embryo development were highly affected in spermatozoa incubated at 41°C compared with non-incubated spermatozoa (P < 0.01). Similarly, embryo quality was adversely affected by sperm incubation at 41°C, as indicated by a higher apoptotic cell ratio in Day 7 blastocysts compared with that in the non-incubated control group (14.6% vs 6.7%, respectively; P < 0.01). Using SB203580 (10 µg mL–1), a specific inhibitor of the p38 MAPK pathway, during sperm hyperthermia reduced MAPK14 activation (24.9% vs 35.6%), increased sperm motility (45.8% vs 26.5%) and reduced DNA fragmentation (16.9% vs 23.4%) compared with the untreated control group, but did not improve subsequent fertilisation and embryo development. In conclusion, heat stress significantly affects the potential of spermatozoa to penetrate oocytes, as well as subsequent embryo development and quality. Notably, the data show that the MAPK14 signalling pathway is largely involved in heat-induced sperm damage. However, further research is needed to elucidate other signalling pathways possibly involved in heat-induced sperm damage.

Development of a modified straw method for vitrification of in vitro-produced bovine blastocysts and various genes expression in between the methods

This study evaluated a modified plastic straw loading method for vitrification of in vitro-produced bovine blastocysts. A modified straw was used with a depressed area on its inner surface to which embryos attach. In vitro-produced blastocysts were randomly assigned into three groups: (i) blastocysts attached to the inner surface of a plastic straw (aV), (ii) blastocysts attached to the inner surface of a modified plastic straw (maV), and (iii) non-vitrified blastocysts (control). The recovery rates were not significantly different between aV and maV groups (95.8% vs. 94.3%). The post-thaw survival rate did not significantly differ between aV and maV groups (86.4% vs. 88.2%). The total cell numbers of blastocyst was higher in control than in aV and maV groups (142 ± 21.8 vs. 117 ± 29.7 and 120 ± 25.2; P < 0.05), but not significantly differ between aV and maV groups. The mRNA levels of pro-apoptosis related genes Bax and Caspase-3 were higher in aV and maV than in control (P < 0.05). By contrast, the mRNA levels of anti-apoptotic genes Bcl-2 and Mcl-1 and of antioxidant-related genes MnSOD and Prdx5 were lower in aV and maV than in control (P < 0.05). Confocal microscopy analysis of Golgi apparatus and mitochondria showed that the fluorescence intensity of Golgi apparatus and mitochondria was higher in control than in aV and maV groups. In conclusion, both aV and maV methods can be used to successfully vitrify IVP blastocysts, with maV method to be preferable because of its easiness in embryo loading.

Heat stress response of male germ cells

The vast majority of mammalian testes are located outside the body cavity for proper thermoregulation. Heat has an adverse effect on mammalian spermatogenesis and eventually leads to sub- or infertility. Recent studies have provided insights into the molecular response of male germ cells to high temperatures. Here, we review the effects of heat on male germ cells and discuss the mechanisms underlying germ cell loss and impairment. We also discuss the role of translational control in male germ cells as a potential protective mechanism against heat-induced germ cell apoptosis.

Impact of proximal cytoplasmic droplets on quality traits and in-vitro embryo production efficiency of cryopreserved bull spermatozoa

Background

Proximal cytoplasmic droplets (PCDs), a remnant of germ cell cytoplasm, are common non-specific morphological defects in bovine semen. This study evaluated the effect of higher percentages of PCDs on the quality of frozen-thawed bovine semen, embryo production and early embryo development.

Methods

Three ejaculates from each of five (group 1: PCD ≤ 1%, control) and eight adult Bos indicus bulls (group 2: PCD ≥ 24%) were analysed. Semen samples were examined for: post-thaw motility, vigour of movement, concentration, sperm morphology, slow thermoresistance test (STT), membrane integrity, acrosome status, mitochondrial function using fluorescent probes association (FITC-PSA, PI and JC-1) and sperm chromatin integrity using acridine orange assay. Two bulls from group 2, with 28.5% and 48.5% PCD, respectively, and three bulls from the control group, each with 0% PCD, were selected for IVF (in vitro fertilisation).

Results

Semen analyses revealed a significant correlation (P < 0.01) between increased rates of PCD and sperm quality traits. Nevertheless, no differences were observed in sperm motility and vigour either before or after the STT or in the percentage of intact acrosomes (analysed by differential interference contrast microscopy (DIC) after STT), but membrane integrity, acrosome status (evaluated with FITC-PSA staining method after thawing) and mitochondrial function were reduced, when compared with group 1 (P < 0.05). The higher incidence of PCD was positively correlated to chromatin damage, especially after three hours of incubation at 37°C. IVF showed similar results for bull C2 (group 1, control) and bull P2 (group 2, group with higher PCDs).

Conclusion

Higher PCD levels influenced spermatozoa quality traits. IVF and embryo development data showed that cleavage, blastocyst formation and blastocyst hatching may have been influenced by the interaction of morphology traits and individual bull effects.

Expression pattern of apoptotic genes in vitrified-thawed bovine oocytes

This study describes a method for quantification of transcripts from low numbers of bovine oocytes using real time RT-PCR. The objective was to evaluate the expression pattern of apoptotic genes (Fas, FasL, Bax and Bcl-2) in vitrified-thawed oocytes. Oocytes were evaluated at germinal vesicle stage; at 15 h of maturation; after vitrification and warming at 15 h of maturation and at 9 h of additional maturation. All transcripts showed an increase in at least 1.2-fold change post-vitrification warming, but the levels tended to decrease at 9 h of maturation post-vitrification warming. Transcript abundance for Fas mRNA was 1.4-fold for oocytes after vitrification and warming. The level of Fas mRNA upon maturation was 0.8-fold. The increase in the abundance of FasL mRNA was 2.1, while it was 0.5-fold relative to control. Vitrification resulted in 1.5-fold change in Bax mRNA expression in oocytes. After 9 h of maturation post-vitrification warming, the level for Bax mRNA was 0.6-fold. The mRNA for Bcl-2 was nearly the same after vitrification and warming. The abundance of mRNA for Bcl-2 was 1.2-fold in vitrified oocytes and fell (p = 0.05) to 0.5 at 9 h of maturation post-vitrification and warming. The up-regulation of apoptotic genes in vitrified oocytes may be an early indicator of reduced developmental competence following vitrification. Yet, results from terminal deoxynucleotidyl transferase dUTP nick end labelling and caspase assays did not support the evidence of apoptosis in embryos derived from large numbers of vitrified oocytes.

Vitrification of bovine oocytes: implications of follicular size and sire on the rates of embryonic development

PURPOSE

The objectives were to test how the source of oocytes and semen impacted vitrification of large numbers of bovine oocytes and subsequent IVF and early embryo development to test procedures that may assist with assisted reproductive technologies in humans.

METHODS

Bovine oocytes were vitrified from follicles of different diameters, small (< or =4 mm) and medium (4 to 10 mm), using nylon mesh. Oocytes were exposed to the cryoprotectant composed of 40% (v/v) ethylene glycol, 18% (w/v) Ficoll-70, and 0.3 M sucrose in three stepwise dilutions. Thawing was conducted with a series of 0.5, 0.25 and 0.125 M sucrose dilutions in 20% fetal bovine serum.

RESULTS

The cleavage (39.1% vs. 58.5%) and blastocyst rates (5.1% vs. 22.9%) were significantly lower for the vitrified oocytes. Follicle size had a significant impact on the development of embryos. Sires had significant effects on embryonic developmental rates.

CONCLUSIONS

We conclude that differences in development exist due to follicle source and sire used for IVF after vitrification.

In vitro development of bovine embryos cultured with stem cell factor or insulin-like growth factor-I following IVF with semen of two bulls having different field fertility

The usefulness of IVF as a potential tool to evaluate the field fertility of bulls is equivocal and growth factor addition to culture media research is needed to delineate components needed for providing defined environments for embryos. The overall aim was to evaluate the in vitro development of embryos derived using a serum supplemented and serum-free production systems and semen from two bulls of different field fertility. The study was conducted to determine the combinatorial effect of stem cell factor (SCF) and/or insulin-like growth factor-I (IGF-I) in culture on subsequent embryo development in cattle. Oocytes were aspirated separately from >or=3 to <3mm follicles to test different follicle size populations and were matured in TCM-199 supplemented with LH, FSH, estradiol and BSA (Fraction V). Matured oocytes were fertilized in BSA supplemented synthetic oviductal fluid (SOF)-IVF medium. Presumptive zygotes were cultured for 8d (in humidified 5% CO(2) at 38.5 degrees C) in BSA supplemented SOF-in vitro culture (IVC) medium. SOF-IVC medium was supplemented with fetal bovine serum (4%), IGF-I (100ng/mL), SCF (50ng/mL) or IGF-I (100ng/mL)+SCF (50ng/mL). The development competence of embryos did not differ between the bulls and among the culture environments. Nevertheless, there was an effect of follicle size on cleavage rate (P<0.05) and a greater cleavage rate resulted from oocytes aspirated from >or=3mm follicles (71.0+/-1.5%) compared to those collected from <3mm follicles (64.8+/-1.6%). The overall cleavage rate (%); blastocyst formation (%); and expanded/hatched blastocyst formation (%) were 68.2+/-1.5 and 67.7+/-1.7; 29.4+/-1.4 and 28.6+/-1.5; and 18.6+/-1.2 and 18.5+/-1.1, respectively, for the bull of above and below average field fertility. The results indicate that follicle size for oocyte aspiration is effective for determining IVC success and that IVF may not discriminate among bulls of different field fertility.

Consequences for the bovine embryo of being derived from a spermatozoon subjected to post-ejaculatory aging and heat shock: development to the blastocyst stage and sex ratio

The objective was to determine whether aging of sperm caused by incubation at normothermic (38.5 C) or heat shock (40 C) temperatures for 4 h prior to oocyte insemination affects sperm motility, fertilizing ability, competence of the resultant embryo to develop to the blastocyst stage and blastocyst sex ratio. In the first experiment, the percent of sperm that were motile was reduced by aging (P<0.001) and the reduction in motility was greater for sperm at 40 C compared to sperm at 38.5 C (P<0.01). In the second experiment, oocytes were inseminated with aged sperm. A smaller percent of oocytes fertilized with sperm aged at either temperature cleaved by Day 3 after insemination than oocytes fertilized with fresh sperm (P<0.05). There was no effect of sperm aging on the percent of oocytes or cleaved embryos that developed to the blastocyst stage. Aging of sperm before fertilization at 38.5 C reduced the percent of blastocysts that were male (P=0.08). In the third experiment, incubation of sperm at 38.5 C or 40 C for 4 h did not reduce fertilizing ability of sperm as determined by pronuclear formation at 18 h post insemination. In conclusion, aging of sperm reduced cleavage rate and the percent of blastocysts that were males but had no effect on the developmental capacity of the embryo. The effect of aging on cleavage rate may represent reduced motility and errors occurring after fertilization and pronuclear formation. Aging at a temperature characteristic of maternal hyperthermia had little additional effect except that polyspermy was reduced. Results indicate that embryo competence for development to the blastocyst stage is independent of sperm damage as a result of aging for 4 h at normothermic or hyperthermic temperatures.

Influence of the male on embryo quality

Early pregnancy failure or loss (EPL) represents a major source of wastage and inefficiency in livestock production systems. Although successful embryo development is dependent upon genetic and epigenetic contributions from both the male and female, potential adverse male affects on embryo quality and development are probably often underestimated. Of adverse male effects which have been identified, those associated with sperm and semen "quality" have been best characterized. In turn, although many factors can adversely impact semen quality, the mechanisms involved are relatively few. This presents opportunities for identifying biological markers for spermatogenic damage, as well as protective measures.

Assessment of pronuclear formation following in vitro fertilization with bovine spermatozoa obtained after thermal insulation of the testis

This study was conducted to follow the chronology of pronuclear formation in bovine zygotes after in vitro insemination with a population of spermatozoa having abnormal morphology. Semen samples were obtained and cryopreserved from four Holstein bulls before and after a scrotal insulation period of 48 h (Day 0). A pre-insult (Day 5) and a Day 20 post-insult semen sample were evaluated for morphology and used for IVF after standard swim-up sperm separation protocols. Pronuclear formation was scored on subpopulations of presumptive zygotes after they were fixed and stained at 3-h time intervals from 6 to 18 h post in vitro insemination (hpi). Post-thaw morphological evaluation of semen samples revealed a decrease in the percentages of normal spermatozoa in the post-insult samples compared with the pre-insult samples for Bull I (74-22%) and Bull III (68-1%). The sperm penetration rate decreased (P<0.05) between the pre- and post-insult samples for Bulls I (90-76%) and III (92-70%), but was not different for Bulls II (92-90%) and IV (78-85%). The pronuclear formation rates for post-insult zygotes for Bulls II and IV had comparable increases in development over time, whereas there was no increase in the pronuclear development for the zygotes from the post-insult samples for Bulls I and III, and generally a condensed sperm head was observed in the oolemma. At 18 hpi the fertilization rate between the pre- and post-insult samples for Bulls I (51-4%), II (88-75%) and III (94-2%) decreased (P<0.01), but there was no change for Bull IV (66%). In conclusion, we inferred that the failure in normal pronuclear formation was associated with an absence of normal decondensation of the penetrating spermatozoon; this suggested that the effect of morphologically abnormal spermatozoa occurred prior to cleavage, thus limiting early development.

A novel apical midpiece defect in the spermatozoa of a bull without an apparent decrease in motility and fertility. A case study

Despite some limitations as predictors of fertility, evaluation of sperm morphology and progressive motility is the commonest method to assess viability of frozen/thawed semen. In this article we describe by light and transmission electron microscopy a novel midpiece structural defect observed in 24-36% of frozen/thawed sperm cells from a Charolais bull, used in artificial insemination programs without any apparent ill effect to the fertility. After thawing, the sperm progressive motility ranged from 65 to 80% and the pregnancy rate for all artificial inseminations performed (43%) did not differ (p>0.05) from results obtained with insemination with semen of other bulls (40%). The defect consisted in mitochondrial aplasia at the neck region, mitochondrial segmental elongation and gaps and thickening of the outer dense fibers at the apical region of the midpiece, and loss of the cementing substance and development of plasma membrane extensions in the entire midpiece. No structural abnormalities were found in the capitulum, proximal centriole, striated columns, axoneme, annulus and fibrous sheath. The thickness of the outer fibers returned to normal at the distal region of the midpiece. Based on the examination it is suggested that the alterations might be originally caused by loss of the cementing substance that links mitochondria to the plasma membrane in association with mitochondrial aplasia at the neck region of the midpiece. The abnormality appeared not related to other described sperm defect syndromes, although it shared particular characteristics with the dag defect, segmental aplasia of the mitochondrial sheath, corkscrew defect and pseudodroplet defect.

Is apoptosis in bovine in vitro produced embryos related to early developmental kinetics and in vivo bull fertility?

Although several studies have indicated a paternal effect on bovine embryo development, no conclusive data exist on the effect of in vivo bull fertility on apoptosis. Therefore, it was the main objective of this study to compare the apoptotic cell ratio (ACR) in embryos originating from bulls with different in vivo fertility. However, since it is has been demonstrated before that bulls with different in vivo fertility differ in timing of first cleavage, it was necessary to investigate first the effect of timing of development on apoptosis in vitro in order to get an unbiased insight in the contribution of in vivo bull fertility on apoptosis in bovine blastocysts. In the first experiment, bovine embryos (n = 939) were allocated to different groups according to cleavage rate at 30, 36 and 48 hpi and blastocysts were selected at 7 and 8 dpi. The blastocyst rate at 7 dpi was significantly lower in embryos which had first cleaved at 48 hpi than in embryos from the 30 and 36 hpi group (P < 0.05). The ACR after TUNEL in day 7 blastocyst was significantly lower in the 30 hpi group in comparison with the 36 and 48 hpi group (P < 0.05) and lower in day 7 blastocysts than in day 8 blastocysts. In the second experiment, sperm of eight bulls with different non return rates was used for in vitro bovine embryo production (n = 3820 oocytes). Cleavage rates (30, 36 and 48 hpi) and blastocyst rate (7 dpi) were determined. Only very low negative correlations could be found between in vivo and in vitro bull fertility and ACR did not differ between groups derived from sires with either low or normal fertility (P > 0.05). Further research in serum free conditions is needed to confirm that the lower ACR in early cleaved embryos could be mediated by the cooperative interaction of embryos of good quality cultured in group. In vivo bull fertility could hardly be correlated with in vitro blastocyst yield and could not be correlated with appearance of apoptosis.

The incidence of apoptosis after IVF with morphologically abnormal bovine spermatozoa

Normal embryonic development depends on the maintenance of a population of normal healthy cells within each embryo. The aim of this study was to use a combination of apoptotic measures to assess differences in embryo quality after IVF with semen samples with high percentages of abnormal spermatozoa. Semen samples were obtained and cryopreserved from four Holstein bulls before (5 day prior) and after (2 week-post-insult; 2 week-PI and day 20; 3 week-PI) a scrotal insulation period of 48 h (day 0). The swim-up sperm separation method was used. The post-thaw morphology revealed a decrease (P < 0.01) in the percentages of normal spermatozoa in the 3 week-PI samples in comparison with the pre-insult samples for Bulls I and III (74-22.3 and 67.7-0.5%, respectively). The percentage of vacuolated spermatozoa increased significantly for Bull II. After 18 h of sperm-oocyte co-incubation, zygotes were cultured and subpopulations were removed from culture at day 8 and subjected to either the TUNEL or caspase assay. On day 8, caspase intensity increased significantly for both Bull I (217+/-147) and Bull III (229+/-98) for the 3 week-PI embryo groups compared to the equivalent embryo groups for Bull II (98+/-115) and Bull IV (90+/-111). In conclusion, the inability to consistently measure apoptosis with TUNEL alone complicated the assessment of differences in embryo quality. Thus, it is uncertain exactly when during early pre-implantation development the differences in embryo quality are first manifest. Despite discrepancies, our results clearly indicated a difference in the embryo quality between embryos obtained after IVF with semen samples from bulls that had an intense response to scrotal insulation.