Sperm miRNAs- potential mediators of bull age and early embryo development.

Background: Sperm miRNAs were reported to regulate spermatogenesis and early embryonic development in some mammals including bovine. The dairy cattle breeding industry now tends to collect semen from younger bulls under high selection pressure at a time when semen quality may be suboptimal compared to adult bulls. Whether the patterns of spermatic miRNAs are affected by paternal age and/or impact early embryogenesis is not clear.

Effects of follicular ablation and GnRH on synchronization of ovulation and conception rates in embryo recipient heifers.

Two experiments were performed to determine effects of follicular ablation (FA) and GnRH treatment on conception rate and synchronization in timing of ovulation among Holstein heifers. In Experiment 1, heifers were randomly allocated to four groups: Control (n = 84): prostaglandin F (PGF) IM on Day 0; FA-5/GnRH (n = 43): FA 5 days before PGF and GnRH on Day 2; FA-4/GnRH (n = 48):FA 4 days before PGF and GnRH on Day 2; andFA-3/GnRH (n = 21): FA 3 days before PGF and GnRH on Day 2. Ultrasonography was performed to determine follicular size, ovulation occurrence, and size of CL.

DNA methylation status of bovine blastocysts obtained from peripubertal oocyte donors.

In the dairy industry, the high selection pressure combined with the increased efficiency of assisted reproduction technologies (ART) are leading toward the use of younger females for reproduction purposes, with the aim to reduce the interval between generations. This situation could impair embryo quality, decreasing the success rate of the ART procedures and the values of resulting offspring. Young Holstein heifers (n = 10) were subjected to ovarian stimulation and oocyte collection at 8, 11, and 14 months of age.

The age of the bull influences the transcriptome and epigenome of blastocysts produced by IVF.

Genetic selection for the best suited offspring drives the dairy industry to use young genitors and assisted reproductive technologies (ART) to reduce generation intervals. However, sperm samples collected from peri-pubertal bulls have lower counts and quality compared to samples from adult bulls. Moreover, our previous study identified differentially methylated regions (DMRs) in sperms from early-, peri- and post-pubertal bulls.

The use of adenosine to inhibit oocyte meiotic resumption in Bos taurus during pre-IVM and its potential to improve oocyte competence.

One of the major challenges of artificial reproductive technologies is to develop new methods for producing greater numbers of embryos. An oocyte fosters the ability to develop into an embryo before oocyte meiotic resumption. The aim of the present study was to assess the effect of adenosine (ADO), a purine nucleoside found in follicular fluid, on the inhibition of oocyte meiotic resumption and the production of blastocysts.

Effect of heifer age on the granulosa cell transcriptome after ovarian stimulation.

Genomic selection is accelerating genetic gain in dairy cattle. Decreasing generation time by using younger gamete donors would further accelerate breed improvement programs. Although ovarian stimulation of peripubertal animals is possible and embryos produced in vitro from the resulting oocytes are viable, developmental competence is lower than when sexually mature cows are used.

Granulosa cells of prepubertal cattle respond to gonadotropin signaling and upregulate genes that promote follicular growth and prevent cell apoptosis.

Oocytes collected from prepubertal animals are known to be less developmentally competent than those from adult animals. There is evidence suggesting that acquisition of developmental competence in bovine oocytes may be linked to the expression profile of genes in the granulosa cells (GCs). Cumulus-oocyte complexes (COC) and GCs were collected from 12 Holstein heifers between 2 and 6 months of age (nine follicle-stimulating hormone [FSH] treated and three untreated) and eight FSH-treated cows.

Interval of gonadotropin administration for in vitro embryo production from oocytes collected from Holstein calves between 2 and 6 months of age by repeated laparoscopy.

Laparoscopic Ovum Pick-Up (LOPU) in calves followed by in vitro embryo production (IVEP) and transfer (ET) into adult recipients has great potential for accelerated genetic gain through shortening of the generation interval. In this study, 11 Holstein calves were subjected to up to six LOPU procedures between the ages of 2-6 months at 2-3 weeks interval. In all cases, the animals received a CIDR 5 days prior to LOPU and were gonadotropin-stimulated starting at 72 h before LOPU using one of three protocols that were rotated twice among the animals during the study.

ASAS-SSR Triennial Reproduction Symposium: The use of natural cycle's follicular dynamic to improve oocyte quality in dairy cows and heifers.

The selection of the best dairy heifers is mainly driven by the genetic value of their parents. The phenotype analysis of cows and of the daughters of bulls has been used to identify the best genetic value for decades before being replaced by genomic selection of individuals that are not yet parents. Because it is possible to predict the future value of an individual by its genetic makeup, it becomes feasible to do it as early as the blastocyst stage and to decide which should be transferred or not.

Spermatozoa DNA methylation patterns differ due to peripubertal age in bulls.

In the dairy industry, using semen as soon as the bull is mature enough to produce it is advantageous for breeding purposes. Mammalian spermatogenesis is a hormone-dependent developmental program in which a complex cascade of events must take place to ensure that germ cells reach the proper stage of development at the proper time. Conventional indicators of semen quality such as sperm cell motility and viability usually improve as bulls mature, meeting quality criteria satisfactorily at around 16 months.

Influence of luteinizing hormone support on granulosa cells transcriptome in cattle.

In cows, the use of follicle-stimulating hormone (FSH) to stimulate follicular growth followed by a short period of FSH withdrawal has been shown to be beneficial for oocyte developmental competence. Although this treatment represents a useful optimization to generate highly competent oocytes, the underlying physiological process is not completely understood. The goal of this study was to investigate the role of luteinizing hormone (LH) action during FSH withdrawal before ovulation.

The effect of age and length of gonadotropin stimulation on the in vitro embryo development of Holstein calf oocytes.

The use of oocytes recovered from prepubertal donors for in vitro embryo production has great potential for accelerating the rate of genetic gain in the dairy industry. However, these oocytes are known to be less developmentally competent than those from adult donors. In this study, we investigated the effect of age and gonadotropin stimulation in Holstein heifers subjected to oocyte collection every two weeks between 2 and 6 months of age.

Comparative analysis of granulosa cell gene expression in association with oocyte competence in FSH-stimulated Holstein cows.

Ovarian stimulation with exogenous FSH followed by FSH withdrawal or 'coasting' is an effective means of increasing the number of oocytes obtainable for the in vitro production of cattle embryos. However, the quality of the oocytes thus obtained varies considerably from one cow to the next. The aim of the present study was to gain a better understanding of the follicular conditions associated with low oocyte developmental competence.

Transcriptomic evaluation of bovine blastocysts obtained from peri-pubertal oocyte donors.

Assisted reproduction technologies (ART) and high selection pressure in the dairy industry are leading towards the use of younger females for reproduction, thereby reducing the interval between generations. This situation may have a negative impact on embryo quality, thus reducing the success rate of the procedures. This study aimed to document the effects of oocyte donor age on embryo quality, at the transcriptomic level, in order to characterize the effects of using young females for reproduction purpose.

Transcriptome meta-analysis of three follicular compartments and its correlation with ovarian follicle maturity and oocyte developmental competence in cows.

Oocyte developmental competence in superstimulated cows is dependent in part on the duration of the FSH coasting. FSH coasting refers to superstimulation with FSH (2 days of endogenous FSH following follicle ablation and 3 days of FSH injections) followed by no FSH for a specific duration. The optimal duration varies among individuals.

Effect of cow age on the in vitro developmental competence of oocytes obtained after FSH stimulation and coasting treatments.

The use of oocytes obtained from younger donors for IVF followed by embryo transfer represents an opportunity to accelerate genetic gain by reducing generation time. In this study, we investigated the relationship between donor age and the in vitro developmental competence of oocytes obtained from Holstein females (aged 5-18 months) after FSH stimulation and coasting. The follicle size patterns showed a significantly higher total number of small follicles (5-6 mm) from donors aged 5 to 10 months and a higher total number of medium-sized follicles (7-10 mm) in donors aged 6 to 7 months.

Genome-wide analysis of sperm DNA methylation from monozygotic twin bulls.

Monozygotic (MZ) twins are of great interest to elucidate the contributions of pre- and postnatal environmental factors on epigenetics in the expression of complex traits and diseases. Progeny testing recently revealed that MZ twin bulls do not necessarily lead to identical genetic merit estimates (i.e.

Breed-specific factors influence embryonic lipid composition: comparison between Jersey and Holstein.

Some embryos exhibit better survival potential to cryopreservation than others. The cause of such a phenotype is still unclear and may be due to cell damage during cryopreservation, resulting from overaccumulation and composition of lipids. In cattle embryos, in vitro culture conditions have been shown to impact the number of lipid droplets within blastomeres.

Impact of whole-genome amplification on the reliability of pre-transfer cattle embryo breeding value estimates.

Background: Genome-wide profiling of single-nucleotide polymorphisms is receiving increasing attention as a method of pre-implantation genetic diagnosis in humans and of commercial genotyping of pre-transfer embryos in cattle. However, the very small quantity of genomic DNA in biopsy material from early embryos poses daunting technical challenges. A reliable whole-genome amplification (WGA) procedure would greatly facilitate the procedure.

Improvement of bovine in vitro embryo production by vitamin K₂ supplementation.

Mitochondria play an important role during early development in mammalian embryos. It has been shown that properly controlled follicular preparation increases the likelihood of in-vitro-produced bovine embryos reaching the blastocyst stage and that competent embryos exhibit heightened expression of genes associated with mitochondrial function. We hypothesized that apparently incompetent embryos could be rescued by restoring mitochondrial function.

Gene expression analysis of bovine oocytes at optimal coasting time combined with GnRH antagonist during the no-FSH period.

Ovarian stimulation with FSH combined with an appropriate period of FSH withdrawal (coasting) before ovum pick-up now appears to be a successful way to obtain oocytes with high developmental competence in bovine. Recent results showed that extending follicular growth by only 24 hours has a detrimental effect on oocyte quality as shown by the reduced blastocyst formation rate. Although these treatments are initiated during the luteal phase with low LH level, the small LH pulsatility present at that time could potentially impact follicular development as well as oocyte quality.

Changes in granulosa cells' gene expression associated with increased oocyte competence in bovine.

One of the challenges in mammalian reproduction is to understand the basic physiology of oocyte quality. It is believed that the follicle status is linked to developmental competence of the enclosed oocyte. To explore the link between follicles and competence in cows, previous research at our laboratory has developed an ovarian stimulation protocol that increases and then decreases oocyte quality according to the timing of oocyte recovery post-FSH withdrawal (coasting).

Gene expression analysis of bovine oocytes with high developmental competence obtained from FSH-stimulated animals.

Recent progress in the ovarian stimulation protocol used for bovine in vitro maturation and fertilization, especially through optimization of the follicle-stimulating hormone (FSH) withdrawal period ("coasting") after ovarian pre-treatment with FSH, has significantly improved blastocyst outcome. Despite this important success, the underlying factors leading to improved oocyte quality have not yet been identified. The aim of this project was to compare the transcriptome of germinal vesicle-stage oocytes collected from FSH-stimulated cows after various coasting periods (20, 44, 68, and 92 hr) to determine which transcripts were accumulated or depleted during the rise and fall of competence.

Contribution of oocyte source and culture conditions to phenotypic and transcriptomic variation in commercially produced bovine blastocysts.

Bovine embryo production is practiced worldwide for commercial purposes. A major concern of embryo suppliers is the impact of in vitro production systems on embryo quality. In the present study, we compared Buffalo Rat Liver cell coculture with semidefined, medium-based culture, oocytes recovered postmortem with those obtained from live animals, and in vitro with in vivo embryo development.

Impact of the LH surge on granulosa cell transcript levels as markers of oocyte developmental competence in cattle.

In the case of in vitro embryonic production, it is known that not all oocytes detain the developmental capacity to form an embryo. This capacity appears to be acquired through completion of folliculogenesis, during which the oocyte and follicular cells influence their respective destinies. The differentiation status of granulosa cells (GCs) could therefore offer an indicator of oocyte quality.