The effect of ensiled paulownia leaves in a high-forage diet on ruminal fermentation, methane production, fatty acid composition, and milk production performance of dairy cows

BACKGROUND

The use of industrial by-products rich in bioactive compounds as animal feeds can reduce greenhouse gas production. Paulownia leaves silage (PLS) was supplemented to dairy cows' diet and evaluated in vitro (Exp. 1; Rusitec) and in vivo (Exp. 2, cannulated lactating dairy cows and Exp. 3, non-cannulated lactating dairy cows). The study investigated the PLS effect on ruminal fermentation, microbial populations, methane production and concentration, dry matter intake (DMI), and fatty acid (FA) proportions in ruminal fluid and milk.

RESULTS

Several variables of the ruminal fluid were changed in response to the inclusion of PLS. In Exp. 1, the pH increased linearly and quadratically, whereas ammonia and total volatile fatty acid (VFA) concentrations increased linearly and cubically. A linear, quadratic, and cubical decrease in methane concentration was observed with increasing dose of the PLS. Exp. 2 revealed an increase in ruminal pH and ammonia concentrations, but no changes in total VFA concentration. Inclusion of PLS increased ruminal propionate (at 3 h and 6 h after feeding), isovalerate, and valerate concentrations. Addition of PLS also affected several populations of the analyzed microorganisms. The abundances of protozoa and bacteria were increased, whereas the abundance of archaea were decreased by PLS. Methane production decreased by 11% and 14% in PLS-fed cows compared to the control in Exp. 2 and 3, respectively. Exp. 3 revealed a reduction in the milk protein and lactose yield in the PLS-fed cows, but no effect on DMI and energy corrected milk yield. Also, the PLS diet affected the ruminal biohydrogenation process with an increased proportions of C18:3 cis-9 cis-12 cis-15, conjugated linoleic acid, C18:1 trans-11 FA, polyunsaturated fatty acids (PUFA), and reduced n6/n3 ratio and saturated fatty acids (SFA) proportion in milk. The relative transcript abundances of the 5 of 6 analyzed genes regulating FA metabolism increased.

CONCLUSIONS

The dietary PLS replacing the alfalfa silage at 60 g/kg diet can reduce the methane emission and improve milk quality with greater proportions of PUFA, including conjugated linoleic acid, and C18:1 trans-11 along with reduction of SFA. Graphical abstract of the experimental roadmap.

Dietary Coleus amboinicus Lour. decreases ruminal methanogenesis and biohydrogenation, and improves meat quality and fatty acid composition in longissimus thoracis muscle of lambs

Background

Methane production and fatty acids (FA) biohydrogenation in the rumen are two main constraints in ruminant production causing environmental burden and reducing food product quality. Rumen functions can be modulated by the biologically active compounds (BACs) of plant origins as shown in several studies e.g. reduction in methane emission, modulation of FA composition with positive impact on the ruminant products. Coleus amboinicus Lour. (CAL) contains high concentration of polyphenols that may potentially reduce methane production and modulate ruminal biohydrogenation of unsaturated FA.

This study aimed to investigate the effect of BAC of Coleus amboinicus Lour. (CAL) fed to growing lambs on ruminal methane production, biohydrogenation of unsaturated FA and meat characteristics. In this study, the in vitro experiment aiming at determining the most effective CAL dose for in vivo experiments was followed by two in vivo experiments in rumen-cannulated rams and growing lambs. Experiment 1 (RUSITEC) comprised of control and three experimental diets differing in CAL content (10%, 15%, and 20% of the total diet). The two in vivo experiments were conducted on six growing, rumen-cannulated lambs (Exp. 2) and 16 growing lambs (Exp. 3). Animals were assigned into the control (CON) and experimental (20% of CAL) groups. Several parameters were examined in vitro (pH, ammonia and VFA concentrations, protozoa, methanogens and select bacteria populations) and in vivo (methane production, digestibility, ruminal microorganism populations, meat quality, fatty acids profiles in rumen fluid and meat, transcript expression of 5 genes in meat).

Results

CAL lowered in vitro methane production by 51%. In the in vivo Exp. 3, CAL decreased methane production by 20% compared with the CON group, which corresponded to reduction of total methanogen counts by up to 28% in all experiments, notably Methanobacteriales. In Exp. 3, CAL increased or tended to increase populations of some rumen bacteria (Ruminococcus albus, Megasphaera elsdenii, Butyrivibrio proteoclasticus, and Butyrivibrio fibrisolvens). Dietary CAL suppressed the Holotricha population, but increased or tended to increase Entodiniomorpha population in vivo. An increase in the polyunsaturated fatty acid (PUFA) proportion in the rumen of lambs was noted in response to the CAL diet, which was mainly attributable to the increase in C18:3 cis-9 cis-12 cis-15 (LNA) proportion. CAL reduced the mRNA expression of four out of five genes investigated in meat (fatty acid synthase, stearoyl-CoA desaturase, lipoprotein lipase, and fatty acid desaturase 1).

Conclusions

Summarizing, polyphenols of CAL origin (20% in diet) mitigated ruminal methane production by inhibiting the methanogen communities. CAL supplementation also improved ruminal environment by modulating ruminal bacteria involved in fermentation and biohydrogenation of FA. Besides, CAL elevated the LNA concentration, which improved meat quality through increased deposition of n-3 PUFA.

• Coleus amboinicus Lour. (CAL) into sheep diet decreased CH₄ emission.

• CAL did not reduce nutrient digestibility, but inhibited the methanogen community.

• CAL increased ruminal propionate proportion and decreased acetate/propionate ratio.

• CAL elevated n-3 fatty acid concentration in ruminal fluid and meat.

• Supplementation of CAL improved some meat quality traits.

[Lipid metabolism and developmental potential of mammalian oocytes and embryos]

Developmental potential of oocytes and embryos is one of the key factors determining success in reproduction. In vitro produced embryos display reduced quality thus development of non-invasive approaches for quality assessment is a priority. Lipid metabolism belongs to fundamental mechanisms affecting reproductive processes and shaping the quality of gametes and embryos. The cytoplasm of oocytes and embryos contains specialized organelles for lipid storage (lipid droplets) whose number and size is species dependent. The growth and maturation of the oocyte/embryo is accompanied by a great fluctuation in lipid quality and quantity which in turn affects their quality and freezing suitability. There is a possibility to modify lipid parameters both in vivo and in vitro by supplementing fat to diet and culture media. The manuscript presents the current state of knowledge on lipid engagement in the process of quality acquirement by oocytes and embryos of two livestock species – cattle and pig.

WNT signalling supported by MEK/ERK inhibition is essential to maintain pluripotency in bovine preimplantation embryo

Capturing stable embryonic stem cell (ESC) lines from domesticated animals still remains one of the challenges of non-rodent embryology. The stake is high, as stable ESCs derived from species such as cattle present high economic and scientific value. Understanding of the processes leading to the embryonic lineage segregation is crucial to provide species-orientated molecular environment capable of supporting self-renewal and pluripotency. Therefore, the aim of this study was to validate the action of the two core regulatory pathways (WNT and MEK/ERK) during bovine embryo development. In vitro produced bovine embryos were obtained in the presence of inhibitors (i), which enable activation of the WNT pathway (via GSK3i, CHIR99021) and suppression of MEK signalling by PD0325901 in the 2i system and PD184325 and SU5402 in the 3i system. We have followed the changes in the distribution of the key lineage specific markers both at the transcript and protein level. Our results showed that WNT signalling promotes the expression of key inner cell mass (ICM) specific markers in bovine embryos, regardless of the MEK/ERK inhibitor cocktail used. MEK/ERK downregulation is crucial to maintain OCT4 and NANOG expression within the ICM and to prevent their exclusion from the trophectoderm (TE). At the same time, the classical TE marker (CDX2) was downregulated at the mRNA and protein level. As a follow up for the observed pluripotency stimulating effect of the inhibitors, we have tested the potential of the 2i and the 3i culture conditions (supported by LIF) to derive primary bovine ESC lines. As a result, we propose a model in which all of the primary signalling pathways determining embryonic cell fate are active in bovine embryos, yet the requirement for pluripotency maintenance in cattle may differ from the described standards. WNT activation leads to the formation (and stabilisation of the ICM) and MEK/ERK signalling is maintained at low levels. Unlike in the mouse, GATA6 is expressed in both ICM and TE. MEK/ERK signalling affects HP formation in cattle, but this process is activated at the post-blastocyst stage. With regard to self-renewal, 2i is preferable, as 3i also blocks the FGF receptor, what may prevent PI3K signalling, important for pluripotency and self-renewal.

Inhibitor mediated WNT and MEK/ERK signalling affects apoptosis and the expression of quality related genes in bovine in vitro obtained blastocysts

Culture conditions determine embryo quality, which may be affected on many levels (timing of development, blastomere count, transcripts, metabolite content, apoptosis). Molecular interactions of signalling pathways like MEK/ERK and WNT/β-catenin are critical for cell-to-cell communication and cellular differentiation. Both pathways are important regulators of apoptosis. We have aimed to verify the prolonged effect of MEK/ERK silencing and WNT activation by chemical inhibitors (2i or 3i systems) on bovine IVP embryos. Apoptotic index, total cell count and transcription of embryo quality markers were evaluated. A higher rate of apoptosis was observed in 2i blastocysts, but was not accompanied by changes in transcript content of genes controlling apoptosis (BAX, BCL2, BAK, BAX/BCL2 ratio). Therefore, alternative pathways of apoptotic activation cannot be ruled out. The expression of genes related to embryo quality (HSPA1A, SLC2A1) was not affected. GJA1 transcripts were significantly higher in 3i blastocysts, what indicates a stimulatory effect of the applied inhibitors on cell-to-cell interactions. The lowest mRNA level of the IFNT2 gene was found in 2i embryos. A variation in the SDHA gene transcript was observed (with the highest content in the 3i blastocysts), what may suggest their reduced quality. It may be concluded that the modifications of culture conditions (activation of the WNT and silencing of the MEK/ERK signalling) might alter pathways crucial for embryo development without causing embryonic death.

The consequences of porcine IVM medium supplementation with follicular fluid become reflected in embryo quality, yield and gene expression patterns

Oocyte and embryo developmental competence are shaped by multiple extrinsic and intrinsic factors. One of the most extensive research areas in the last decade is the regulation of lipid metabolism in oocytes and embryos of different species. We hypothesized that differences in developmental competence of oocytes and embryos between prepubertal and cyclic gilts may arise due to distinct fatty acid profiles in follicular fluid. We found that supplementation of oocyte maturation media with follicular fluid from prepubertal pigs affected quality and development of embryos from prepubertal pigs while embryos of cyclic pigs were not affected. PLIN2, SCD and ACACA transcripts involved in lipid metabolism were upregulated in embryos originating from oocytes of prepubertal pigs matured with autologous follicular fluid. The surface occupied by lipid droplets tend to increase in oocytes matured with follicular fluid from prepubertal pigs regardless oocyte origin. The change into follicular fluid of cyclic pigs increased the efficiency of embryo culture and improved quality, while gene expression was similar to embryos obtained from cyclic gilts. We assume that the follicular fluids of prepubertal and cyclic pigs influenced the quality of oocytes and embryos obtained from prepubertal pigs which are more susceptible to suboptimal in vitro culture conditions.

Changes in chromosome territory position within the nucleus reflect alternations in gene expression related to embryonic lineage specification

Loss of totipotentcy in an early embryo is directed by molecular processes responsible for cell fate decisions. Three dimensional genome organisation is an important factor linking chromatin architecture with stage specific gene expression patterns. Little is known about the role of chromosome organisation in gene expression regulation of lineage specific factors in mammalian embryos. Using bovine embryos as a model we have described these interactions at key developmental stages. Three bovine chromosomes (BTA) that differ in size, number of carried genes, and contain loci for key lineage regulators OCT4, NANOG and CDX2, were investigated. The results suggest that large chromosomes regardless of their gene density (BTA12 gene-poor, BTA5 gene-rich) do not significantly change their radial position within the nucleus. Gene loci however, may change its position within the chromosome territory (CT) and relocate its periphery, when stage specific process of gene activation is required. Trophectoderm specific CDX2 and epiblast precursor NANOG loci tend to locate on the surface or outside of the CTs, at stages related with their high expression. We postulate that the observed changes in CT shape reflect global alternations in gene expression related to differentiation.

Interactions of bovine oocytes with follicular elements with respect to lipid metabolism

Among many factors, lipid metabolism within the follicular environment emerges as an important indicator of oocyte quality. In the literature a crucial significance is described concerning follicular fluid (FF) composition as well as messenger RNA (mRNA) expression in follicular cells. The aim of this study was to describe the relationship between oocyte, FF and follicular cells with regard to lipid metabolism. The set of data originating from individual follicles comprised: lipid droplets (LD) number in oocytes (BODIPY staining), mRNA expression of seven genes in cumulus and granulosa cells (SCD, FADS2, ELOVL2, ELOVL5, GLUT1, GLUT3, GLUT8; real time polymerase chain reaction) and fatty acid (FA) composition in FF (gas chromatography). Obtained results demonstrate significant correlation between oocyte lipid droplets number and FA composition in FF. However, gene expression studies show significant correlation between LD number and GLUT1 gene only. Moreover, the present experiment revealed correlations between FA content in FF and expression of several genes (SCD, FADS2, ELOVL5, GLUT8) in granulosa cells, whereas only the SCD gene in cumulus cells. We suggest that the results of our experiment indicate the importance of glucose : lipid metabolism balance, which contributes to better understanding of energy metabolism conversion between oocytes and the maternal environment.

Prepubertal heifers versus cows-The differences in the follicular environment

The oocyte quality is to a large extent influenced by the sexual maturity of the donor female. Although this phenomenon has already been broadly described in domestic animals, the underlying mechanisms are poorly understood. Published data focus on oocyte ultrastructure, fertilization abnormalities, and blastocyst developmental rate. The goal of the present experiment was to characterize the follicular environment (oocyte, cumulus [CC] and granulosa (GC) cells as well as follicular fluid [FF]) in ovarian follicles of prepubertal heifers and cows. Each experimental replicate included the following set of traits within individual follicles: lipid droplets (LDs) number in oocytes, expression of seven genes involved in energy metabolism (fatty acids [FAs] metabolism-ELOVL2, ELOVL5, SCD, FADS2, glucose transport-GLUT1, GLUT3, GLUT8) in CC and GC as well as FA composition and glucose concentration in FF. According to our results, cow oocytes were larger in diameter and contained more LD than those from prepubertal heifers, both before and after IVM. The LD number was also higher in cow oocytes after IVM, when compared to immature oocytes. The FF from cow follicles had elevated glucose content similarly to the majority of the analyzed FA. Transcript analysis revealed differences for five out of seven analyzed genes (ELOVL, FADS2, SCD, GLUT3, GLUT8) in CC and GC cells. However after considering the female category, the only difference was noticed for the mRNA of SCD gene, which was more abundant in cow GC. This finding may indicate distinct roles of CC and GC in follicular energy metabolism. In conclusions, we suggest that distinct properties of follicular environment in prepubertal heifers and cows may be responsible for differences in the quality of oocytes from the two categories of donors. We hypothesize that suboptimal environment in heifer follicles (glucose and FA lower content in FF) determines reduced quality of their oocytes (lower diameter and LD number) and limited maturation potential. Besides, energy demands of heifer oocytes may be restricted due to a low LD number, exerting a negative effect on the development of the future embryo. The advantages of cow gametes (e.g., higher LD number and diameter) attributed to oocytes of superior quality may support the statement that cows donate oocytes of better quality than heifers.

Differences in cytoplasmic maturation between the BCB+ and control porcine oocytes do not justify application of the BCB test for a standard IVM protocol

The Brilliant Cresyl Blue (BCB) test relies on G6PDH activity and a simple protocol for the selection of higher quality oocytes. Although the BCB+ oocytes of all the species that have been investigated are characterized by superior quality when compared to BCB- counterparts, application of the test for embryo production still remains an open issue. The aim of our study was to compare BCB+ and the control oocytes (not subjected to the BCB test) in terms of selected aspects of cytoplasmic maturation (mtDNA copy number, mitochondria distribution, relative transcript abundance of six marker genes). The results of our study revealed more relevant differences within the BCB+ and the control oocytes (before and after IVM) than between the two categories of oocytes. There was no difference in the transcript abundance of the BCB+ and the control oocytes in 5 out of 6 analyzed genes (BMP15, GDF9, ATP5A1, EEF1A, ZAR1) and in mtDNA content (pre-IVM 179609 vs. 176595 and post-IVM 187243 vs. 246984, respectively). With regard to mitochondria distribution in pre- and post-IVM oocytes, there was nonsignificant tendency for a more frequent occurrence of the expected patterns in the BCB+ group. The results of the present study do not support the application of BCB staining in a routine IVM protocol due to relatively high similarity in selected parameters characterizing cytoplasmic maturation of BCB+ and control oocytes. This high similarity may results from the limited amount of less competent BCB- oocytes (10%) still present among nonselected oocytes of proper morphology.

Multifactorial analysis of the follicular environment is predictive of oocyte morphology in cattle

Numerous attempts have been recently made in the search for a reliable, fast and noninvasive assay for selection of oocytes suitable for in vitro embryo production. Potential markers have been described in the follicle such as follicular fluid (FF) or cumulus cells (CCs). However, the reported findings are contradictory, which may reflect the complexity of metabolism of the ovarian follicle. In the present experiment, a data set from individual follicles of known diameter was obtained: cumulus-oocyte complex (COC) morphology, fatty acid composition and glucose concentration in FF as well as apoptotic index in CCs. The obtained data was statistically analyzed either separately (univariate analysis) or simultaneously (multivariate analysis) to examine its predictive value in morphology assessment of bovine COCs. Although the univariate analysis yielded a complex relation system of the selected parameters, no clear outcome could be established. In multivariate analysis, the concentration of the four fatty acids (C16:0, C16:1, C18:1cis9, C22:5n3) and Δ⁹-desaturase (16) as well as elongase activities were selected as covariates. This allowed prediction of the morphology of a COC with an accuracy of 72%, which is the most interesting finding of the experiment. The present study indicates that the multifactorial model comprising of selected parameters related to the follicle appeared more effective in predicting the morphology of a bovine COC, which may improve the effectiveness of in vitro production systems.

Changes in sub-cellular localisation of trophoblast and inner cell mass specific transcription factors during bovine preimplantation development

Background

Preimplantation bovine development is emerging as an attractive experimental model, yet little is known about the mechanisms underlying trophoblast (TE)/inner cell mass (ICM) segregation in cattle. To gain an insight into these processes we have studied protein and mRNA distribution during the crucial stages of bovine development. Protein distribution of lineage specific markers OCT4, NANOG, CDX2 were analysed in 5-cell, 8–16 cell, morula and blastocyst stage embryos. ICM/TE mRNA levels were compared in hatched blastocysts and included: OCT4, NANOG, FN-1, KLF4, c-MYC, REX1, CDX2, KRT-18 and GATA6.

Results

At the mRNA level the observed distribution patterns agree with the mouse model. CDX2 and OCT4 proteins were first detected in 5-cell stage embryos. NANOG appeared at the morula stage and was located in the cytoplasm forming characteristic rings around the nuclei. Changes in sub-cellular localisation of OCT4, NANOG and CDX2 were noted from the 8–16 cell onwards. CDX2 initially co-localised with OCT4, but at the blastocyst stage a clear lineage segregation could be observed. Interestingly, we have observed in a small proportion of embryos (2%) that CDX2 immunolabelling overlapped with mitotic chromosomes.

Conclusions

Cell fate specification in cattle become evident earlier than presently anticipated – around the time of bovine embryonic genome activation. There is an intriguing possibility that for proper lineage determination certain transcription factors (such as CDX2) may need to occupy specific regions of chromatin prior to its activation in the interphase nucleus. Our observation suggests a possible role of CDX2 in the process of epigenetic regulation of embryonic cell fate.

Altered expression of porcine Piwi genes and piRNA during development

Three Sus scrofa Piwi genes (Piwil1, Piwil2 and Piwil4) encoding proteins of 861, 985 and 853 aminoacids, respectively, were cloned and sequenced. Alignment of the Piwi proteins showed the high identity between Sus scrofa and Homo sapiens. Relative transcript abundance of porcine Piwil1, Piwil2 and Piwil4 genes in testes, ovaries and oocytes derived from sexually immature and mature animals was examined using Real-Time PCR. Expression of the three Piwi mRNAs was proved to be tissue specific and restricted exclusively to the gonads. In testes of adult pigs the highest relative transcript abundance was observed for the Sus scrofa Piwil1 gene. On the other hand, in testes of neonatal pigs the Piwil1 transcript level was over 2-fold reduced while the level of Piwil2 transcript was higher. As regards the expression of the Piwil4 transcript, its level was 34-fold elevated in testes of neonatal piglet when compared to adult male. In ovaries of prepubertal and pubertal female pigs transcript abundance of the three Piwi genes was significantly reduced in comparison with testes. However, similarly to testes, in ovaries of neonatal pigs the Piwil2 gene was characterized by the highest relative transcript abundance among the three Piwi genes analysed. In prepubertal and pubertal oocytes Piwil1 transcript was the most abundant whereas the expression of Piwil4 was undetectable. We also demonstrated that expression of piRNA occurs preferentially in the gonads of adult male and female pigs. Moreover, a piRNA subset isolated from ovaries was 2-3 nucleotides longer than the piRNA from testes.

Early cleaved bovine embryos show reduced incidence of chromosomal aberrations and higher developmental potential on day 4.5 post-insemination

The present study aimed to investigate whether the timing of the first zygotic cleavage (FZC) influences the speed of embryo development expressed by the total cell count and the rate of chromosomally aberrant embryos. Bovine embryos were produced in vitro and divided into two categories according to the timing of FZC: early cleavers (at 30 hpi; EC) and non-early cleavers (at 48 hpi; NEC). On day 4.5 pi, embryos were grouped into three classes depending on the number of blastomeres: delayed (<8 BL), normal (8-16 BL) and advanced (>16 BL). We applied fluorescence in situ hybridization (FISH) with probes for bovine chromosomes 6 and X. The only form of chromosomal imbalance observed was mixoploidy [(2n/3n; 2n/4n); 19.9%, 54/271]. Early cleavers were less often chromosomally unbalanced (13.9%, 20/144) than their NEC counterparts (26.7%, 34/127). Among embryos developing at a normal speed, the NEC embryos were more often abnormal (NEC 20/80; EC 10/79; p < 0.05). The advanced embryos were not observed among the NEC category, whereas such embryos from EC category displayed no chromosomal aberrations. The majority of embryos arrested at the 8 BL stage were of NEC category and were carriers of chromosomally abnormal blastomeres. With regard to embryonic sex, we demonstrated that although males dominate among bovine embryos developing in vitro, the incidence of mixoploidy was equal for both sexes. It can be suggested that a good-quality bovine embryo is usually an early cleaver that develops at higher speed and contains less aberrant cells. The present study also confirmed the usefulness of the FZC as a marker of embryo quality by demonstrating a significantly lower incidence of aberrations in early embryos.

124 SUPPLEMENTATION OF IN VITRO MATURATION MEDIUM WITH GROWTH HORMONE DID NOT AFFECT THE TIMING OF THE FIRST ZYGOTIC CLEAVAGE BUT SIGNIFICANTLY IMPROVED THE QUALITY OF RESULTING BOVINE BLASTOCYSTS

It is well documented that growth hormone (GH) supplemented to maturation medium positively affects in vitro oocyte maturation and embryonic development in cattle. Conditions of in vitro maturation significantly influence oocyte competence for successful fertilization and preimplantation embryo development. It has been shown that bovine zygotes that cleave early are characterized by better quality than their later cleaving counterparts. In this context, the aim of this study was to determine whether supplementation of maturation media with GH affects the timing of the first zygotic cleavage and quality of produced blastocysts. Oocytes were matured in TCM-199 supplemented with fatty acid free BSA and hormones (FSH and GH) and then fertilized (Parrish et al. 1998 Biol. Reprod. 38, 1171–1180), whereas embryos were cultured in sequential media (Lane et al. 2005 Theriogenology 60, 407–419). All embryos that cleaved by 30hpi (early cleavers, EC) were selected and cultured separately. The remaining embryos cleaved by 48hpi (non early cleavers, NEC) were also incubated in separate drops. Blastocysts of proper morphology, collected at 176hpi, were subjected to TUNEL assay and differential staining (TE:ICM ratio). Due to technical problems only expanded blastocysts were analyzed by differential staining. The significance of GH supplementation in relation to apoptotic index and blastomere number (total, TE, ICM) was analyzed by ANOVA. This experiment included 250 blastocysts obtained from 1092 oocytes. The presence of GH did not influence the basic developmental parameters: cleavage rate, percentage of EC embryos and blastocysts (P > 0.05). Blastocysts derived from oocytes matured with GH more often hatched regardless of the timing of the first zygotic cleavage when compared with blastocysts that developed from the control group (P < 0.05). GH supplementation to IVM medium significantly reduced apoptotic index in EC blastocysts (2.9 and 4.8% for control, P < 0.05). Interestingly, blastocysts containing none or one apoptotic blastomere were observed only among EC embryos (20.6%). Although exogenous GH did not affect the cell count in TE and ICM of expanded EC blastocysts, it increased total cell number and reduced the TE:ICM ratio in embryos derived from oocytes culture with GH. In summary, although exogenous GH was previously shown to accelerate the kinetics of oocyte maturation, it has no effect on the timing of the first zygotic cleavage in cattle. The results of the present work support previously published data on GH as growth stimulating and antiapoptotic factor. Its stimulatory effect was especially evident in NEC blastocysts. Those embryos exhibited even better quality (higher cell count, lower apoptotic index) than control EC blastocysts. This work was supported by the project No. 3780/P01/2006/31 of the Ministry of Science and Higher Education, Poland.

132 TIMING OF THE FIRST ZYGOTIC CLEAVAGE WAS NOT RELATED TO THE SHIFT IN SEX RATIO OF BOVINE BLASTOCYST IN VITRO

It has been shown that embryos which cleaved earlier (<30 h postinsemination, hpi) have greater chance to develop to blastocyst. It has been shown that in in vitro conditions male embryos develop faster than females. Further, spermatozoa with the Y chromosome more frequently penetrate oocytes during the first 6 hpi. The aim of this experiment was to investigate the sex-related embryo growth rate in relation to the timing of the first zygotic cleavage and GH presence during IVM. Oocytes were matured in TCM-199 supplemented with fatty acid free BSA and hormones (FSH and GH) and then inseminated (Parrish et al. 1998 Biol. Reprod. 38, 1171–1180), whereas embryos were cultured in sequential media (Lane et al. 2005 Theriogenology 60, 407–419). All embryos that cleaved by 30 hpi (early cleavers, EC) were selected and cultured separately. The remaining embryos cleaved by 48 hpi (non early cleavers, NEC) were also incubated in separate drops. Blastocysts of proper morphology were collected at 176 hpi and subjected to sex determination by PCR (AMGL gene). The significance of developmental stage, timing of the first zygotic cleavage and GH supplementation in relation to the sex ratio was evaluated by the chi-square test. All straws with frozen semen of 2 bulls used in this experiment were derived from single ejaculates. The sex ratio of sperm samples used for IVF was evaluated by FISH with locus-specific probes. The experiment was done on 266 embryos obtained from 1249 oocytes. A significant predominance of male blastocysts regardless of the experimental conditions was observed [the male to female ratio (M:F) 2:1, P < 0.001]. FISH analysis revealed that there was no deviation from the expected 1:1 ratio of X and Y spermatozoa in sperm samples used for IVF. When the timing of the first zygotic cleavage was considered, shift in M:F ratio in favor of males (P < 0.01) in blastocysts derived from EC zygotes was noticed. Due to a very low number of NEC embryos, this category was not included in analysis. Although the M:F ratio was shifted towards males, the rate of female embryos was greater in the control group (25F/38M) v. GH group (16F/39M) of EC expanded blastocysts. This phenomenon was not observed among hatched blastocysts; however, GH presence caused an increase (P < 0.01) in the number of females at this stage. Therefore GH may stimulate embryonic growth, especially embryos of reduced quality, through its positive influence on cytoplasmic oocyte maturation. In conclusion, the predominance of male blastocysts observed in this study may be attributed to the applied IVF procedure because the X:Y ratio in spermatozoa was not different from the expected 1:1 ratio. Moreover, significantly fewer females among analyzed blastocysts may suggest that the developmental potential of female embryos in applied in vitro conditions was somehow reduced when compared with males. This became evident when the transition from expanded to hatched blastocysts was observed. This work was supported by the project No. N302 046 31/3780 of the Ministry of Science and Higher Education, Poland.

Gilts and sows produce similar rate of diploid oocytes in vitro whereas the incidence of aneuploidy differs significantly

Oocytes derived from prepubertal gilts show reduced developmental competence when compared to oocytes collected from adult sows. Therefore, the aim of the study was to investigate whether gilts (4-5 months old) and adult sows (average age 3.5 years) of the same breed (Polish Landrace x Polish Large White crossbred) differ with regard to the rate of chromosomally unbalanced oocytes after IVM. COCs derived from individual pairs of slaughterhouse ovaries were matured in vitro and analyzed cytogenetically by conventional staining (Giemsa) and FISH methods (probes corresponding to centromeric regions of pig chromosomes 1 and 10). Altogether, 72 females (31 sows, 41 gilts) and 430 secondary oocytes (194 and 236 oocytes of sows and gilts, respectively) were investigated. Cytogenetic analysis revealed diploid (Giemsa, FISH) and aneuploid (FISH) spreads. The incidence of diploid oocytes was similar for sows (26.0%) and gilts (24.5%) whereas the rate of aneuploid oocytes (nullisomic/disomic) was eight times higher in gilts (10.8%) than in sows (1.3%). Diploid and aneuploid oocytes were observed in 64% of investigated females. Pig chromosome 10 was more frequently disomic/nullisomic compared to chromosome 1 suggesting, that like in human, small porcine chromosomes are often involved in the nondisjunction process. In conclusion, chromosomal imbalance significantly contributes to in vitro embryo production in the pig, since over 60% of females produced diploid or aneuploid gametes. The significantly higher rate of aneuploidy among oocytes derived from gilt ovaries may contribute to the reduced developmental competence of gametes collected from nonmature female pigs.

Maturation medium supplements affect transcript level of apoptosis and cell survival related genes in bovine blastocysts produced in vitro

The aim of the present study was to investigate whether protein or macromolecule supplements to in vitro maturation media affect transcript abundance of seven genes (Bax, Bcl2, Hsp70, IGF1, IGF1R, IGF2, and IGF2R) in oocytes and blastocysts. Cumulus-oocyte complexes aspirated from slaughterhouse ovaries were matured in TCM199 medium supplemented either with 10% FBS, 6% fatty acid free BSA (fafBSA) or 4% PVP40, then inseminated and cultured in vitro for 9 days. Transcript abundance analysis was carried out on immature and in vitro matured oocytes, as well as on blastocysts. Total RNA was isolated from pools of oocytes and embryos, reverse transcribed into cDNA and subjected to transcript analysis by real-time PCR. No transcript of IGF1 gene was detected either in oocytes or in blastocysts. Maturation conditions significantly affected transcript levels of investigated loci in blastocysts but not in matured oocytes, with one exception. Only relative abundance (RA) of IGF2 gene was higher in oocytes matured with fafBSA. Moreover, oocyte maturation with fafBSA elevated transcript abundance of IGF1R, IGF2, and IGF2R genes in resulting blastocysts, whereas Hsp70 transcription was stimulated by FBS supplementation. Thus, under described conditions, fafBSA may be the optimal supplement to IVM medium due to higher transcript level of growth factor coding genes accompanied by a lower transcript level of Hsp70.

Supplements to in vitro maturation media affect the production of bovine blastocysts and their apoptotic index but not the proportions of matured and apoptotic oocytes

The objective of this study was to compare the effect of different supplements to the basic IVM medium (TCM199) on the efficiency of cattle oocyte maturation and blastocyst production, and the incidence of apoptosis in both oocytes and blastocysts. Two protein supplements (FBS and fafBSA) and a macromolecule (PVP40) were compared in a 3 treatmentsx9 replicates design. Cumulus-oocyte complexes (COCs) aspirated from slaughterhouse ovaries were matured for 24h in TCM199 medium supplemented with 10% FBS, 6% fafBSA or 4% PVP40 (50-70 COCs in each treatment/replicate), then inseminated and cultured in vitro for 8 days. Immature and mature oocytes as well as Day 8 blastocysts were subjected to TUNEL analysis. Cleavage rate was monitored on Day 2 post-insemination (pi), whereas blastocyst yield on Day 8 pi. The composition of maturation media did not affect zygotic cleavage rate on Day 2 (on average 71.0%), however the blastocyst rate on Day 8 pi was significantly lower (P<0.001) for embryos derived from oocytes matured with PVP40 (16.0%) than for those matured with FBS (22.4%) or fafBSA (22.1%). The rate of TUNEL positive oocytes differed significantly between immature (1.4%) and mature (11.2%) oocytes (P<0.01). Supplements to maturation medium were not related to the incidence of apoptosis in mature oocytes (11.2%) and the rate of oocytes at the second metaphase stage (71.5%). Cumulus cell expansion was reduced by maturation in medium supplemented with PVP40. This macromolecule was also correlated with higher apoptotic index in blastocysts (5.8%) when compared to FBS (3.2%) and fafBSA (3.1%; P<0.001). In conclusion, lower blastocyst rate and elevated apoptotic index in embryos derived from oocytes matured with PVP40 may suggest that synthetic macromolecule provides less balanced environment for oocyte maturation and therefore should be treated with caution.

285 TRANSCRIPT LEVEL OF Hsp70 AND IGF2R GENES IN BOVINE INDIVIDUAL BLASTOCYSTS DERIVED FROM OOCYTES MATURED WITH FBS OR FATTY ACID-FREE BSA

The efficiency of in vitro embryo production in cattle varies between 30 and 40% of blastocysts derived from oocytes matured in vitro. Despite a rigorous selection, some embryos at blastocyst stage displaying normal morphology are not competent to develop after hatching (Maddox-Hyttel et al. 2003 Reproduction (Suppl. 61), 103–116). Therefore, a lot of attention has been focused on embryo quality. Supplements to culture media are one of the factors significantly contributing to this phenomenon. Serum (FBS) and albumin (fatty acid-free BSA, fafBSA) are widely used protein supplements; however, their effect on embryo quality is still variable (Rizos et al. 2003 Biol. Reprod. 68, 236–243). The aim of the present study was to investigate whether good-quality blastocysts (hatched or expanded) derived from oocytes matured in media supplemented with FBS or fafBSA differ in transcript level of 2 genes: heat shock protein (Hsp70) and receptor for insulin-like 2 factor (IGF2R). Bovine Day 8 blastocysts were produced in vitro from oocytes aspirated from slaughterhouse ovaries after maturation in TCM-199 medium supplemented with 10% FBS or 6% fafBSA, as previously described (Makarevich and Markkula 2002 Biol. Reprod. 66, 386–392). On Day 8 post-insemination (pi), good-morphology blastocysts were allocated into 3 groups: (1) hatched, (2) expanded of excellent quality, and (3) expanded of good quality, and individually frozen in liquid nitrogen. Each embryo was processed individually through RNA extraction and cDNA synthesis. Transcript quantitation protocol included: real-time PCR with SYBR Green I, β-actin gene as an internal standard, and relative standard curve method. Data analysis was performed by 2-way ANOVA. In each reaction, an equivalent of 0.125 embryo (2.5 �L of cDNA) was used, and 43 blastocysts were analyzed. All analyzed embryos were positive for the Hsp70 transcript, whereas IGF2R mRNA was detected in only 58% of blastocysts regardless of the maturation medium. A large variation in relative abundance (RA) was observed among individual embryos: coefficients of variation were 114.5 and 323.6% for IGF2R and Hsp70, respectively. Due to the distribution of Hsp70 RA, log transformation was performed. Real-time PCR data revealed a maximum 100-fold variation for the reference gene. Hatched blastocysts were characterized by a significantly lower RA for both analyzed genes. The 2 classes of expanded blastocysts did not differ in transcript level. With regard to protein supplements, only the RA for Hsp70 gene was significantly affected. This transcript was more abundant in embryos derived from fafBSA-supplemented IVM medium. The present results confirmed previously the described phenomenon concerning a large variability in mRNA content in single pre-implantation embryos. Moreover, because embryos able to hatch significantly differed in RA from their expanded counterparts, it is possible to relate embryo quality to transcript level.

IVM media, oocyte diameter and donor genotype at RYR1 locus in relation to the incidence of porcine diploid oocytes after maturation in vitro

In the present study three factors were investigated that may affect the process of the first polar body extrusion in pig oocytes matured in vitro: IVM medium, oocyte diameter and donor genotype at the ryanodine receptor (RYR1) locus. In the first experiment, COCs were collected by the aspiration of slaughterhouse ovaries. Oocytes were matured in vitro at 39 degrees C, in humidified 5% CO(2) atmosphere for 44 h using the following media: (1) TCM199+hCG+eCG+follicular fluid (FF), (2) TCM199+hCG+17beta-estradiol and (3) NCSU23+hCG+eCG+FF. According to cytogenetic analysis, 98.1% of cells reached the second metaphase stage (MII). No significant differences were observed among IVM groups in terms of diploidy level. In the second experiment, oocytes collected by the aspiration or slicing of individual ovaries were matured in vitro in groups reflecting their origin. One ovary was considered a donor. IVM was carried out under conditions described in experiment I, with the use of TCM199+hCG+17beta-estradiol. A total of 68 ovaries/donors were included in this study. Granulosa cells collected from each ovary were used as DNA source in molecular (RFLP) analysis. Genotype frequencies at the RYR1 locus were as follows: CC, 0.46; CT, 0.48 and TT, 0.06. After maturation the diameter of each denuded oocyte was determined with the use of a computer aided system. Five size categories were distinguished: <90, 90-100, 100.1-110, 110.1-120 and >120 microm. The average diameter of haploid oocytes at MII stage was 111.7 microm, whereas that of diploid cells was 110.4 microm. According to statistical analysis, diploidy was not related to the oocyte diameter. That trait, however, was influenced by the donor genotype at the RYR1 locus. The TT genotype was associated with a higher rate of diploidy.

302 PROTEIN SUPPLEMENTATION TO IVM MEDIUM IN RELATION TO THE INCIDENCE OF APOPTOSIS IN BOVINE OOCYTES MATURED IN VITRO

Mammalian embryos derived from in vitro fertilization display lower developmental competence and quality when compared to their in vivo counterparts. The composition of culture media significantly contributes to this phenomenon. Media supplemented with FBS or the serum derivate BSA are described as biochemically undefined. Those macromolecules were shown to exert a wide range of effects on cultured embryos, dependent on batch-to-batch variability. Therefore, replacement of these protein sources with a synthetic macromolecule such as polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) provides a possibility to use a chemically defined culture medium (Ali et al. 2002 Biol. Reprod. 66, 901–905). Apoptosis as programmed cell death naturally occurs in mammalian oocytes and embryos; however, its incidence is significantly higher in vitro. The aim of this study was to investigate whether protein supplementation (FBS, fatty acid-free (faf)-BSA, PVP40) of IVM medium affects the incidence of apoptotic oocytes. In the present study, the IVM system previously described by Makarevich et al. (2002 Biol. Reprod. 66, 386–392) was used. Briefly, follicular oocytes aspirated from slaughterhouse ovaries were matured in vitro in one of three maturation media supplemented with FBS (10%), faf-BSA (6 mg mL−1) or PVP40 (4 mg mL−1). The terminal TUNEL assay kit was used to detect the DNA fragmentation in apoptotic cells (DeadEndTM Fluorometric TUNEL system, Promega, Madison, WI, USA). The data were analyzed by chi-square test of independence. Altogether, 630 oocytes collected during 12 IVM experiments were subjected to the Tunel test, and 563 (89.4%) of them were successfully investigated: 426 after maturation in vitro and 137 follicular, non-matured. The remaining 67 cells were lost during manipulation. The rate of Tunel-positive cells differed (P < 0.001) between matured (11.8%) and follicular oocytes (1.5%). Protein supplementation of IVM media did not significantly affect the rate of apoptotic oocyte occurrence, which was 9% in the faf-BSA group, 11.5% in the FBS group, and 15% in the PVP group. No differences were observed in the rate of Tunel-positive cells between oocytes at MII and MI stages. In conclusion, protein supplementation of IVM medium used in the present study did not affect the incidence of apoptotic oocytes after maturation in vitro. This research was supported by the State Committee for Scientific Research as a Solicited Project PBZ-KBN-084 from 2003 to 2005 year.

113 THE DISTRIBUTION OF THE LEPTIN PROTEIN WITHIN BOVINE OOCYTES AND PRE-IMPLANTATION EMBRYOS MATURED AND FERTILIZED IN VITRO

It has recently been documented that leptin regulates processes linked to reproduction including preimplantation development, embryo implantation (trophoblast invasion), and fetal growth. Transcripts for the leptin gene (LEP) and the leptin receptor gene (LEPR) have been identified in ovary, testis, placenta, endometrium, ovarian follicles, and oocytes, and also in mouse, rat, human, and bovine pre-implantation embryos. Moreover, the leptin protein was detected in mouse and human oocytes and embryos, and its localization was polarized. The distribution of regulatory proteins within oocytes and pre-implantation embryos is critical for early mammalian development, such as determination of the animal pole and the establishment of the trophoblast and the inner cell mass cells (ICM). So far there is no published evidence concerning this phenomenon in bovine oocytes and embryos. Therefore, the aim of this work was to analyze the leptin protein distribution within bovine oocytes and preimplantation embryos matured and fertilized (in vitro). The material for this work consisted of oocytes collected from slaughterhouse ovaries and sperm collected from AI bulls. In vitro oocyte maturation and fertilization were carried out according to the method described by Makarevich and Markkula (2002 Biol. Reprod. 66, 386–392). The preliminary experiment of leptin protein localization by immunofluorescent staining included immature and matured oocytes and blastocysts. Oocytes and embryos were fixed in PBS containing 4% paraformaldehyde and reacted with affinity-purified polyclonal rabbit primary antibody directed against leptin (0.1 mg/mL; Ob (Y20), Santa Cruz Biotechnology Inc., Santa Cruz, CA, USA); and then exposed to secondary goat-anti-rabbit antibody (1.0 mg/mL; Santa Cruz Biotechnology Inc.)-fluorescein isothiocyanate (FITC) conjugate. Finally, chromatin was visualized by propidium iodide staining (0.5 μg/mL). Slides were examined under a conventional fluorescence microscope (Nikon) and confocal microscope (Zeiss). The preliminary results demonstrate that the distribution of leptin differed between immature and mature oocytes: it was spherical in immature oocytes (a rim beneath the oolemma) whereas it became evenly distributed after maturation. In blastocysts, leptin signals were present inboth the trophoblast cells and in the ICM cells. This is in contrast with studies on mouse embryos which showed the presence of the LEP protein in the trophoblast only. Future experiments will include studies of embryos at the 2-cell, 4-cell, 8–16-cell, and morula stages. The present study for the first time shows the pattern of leptin protein distribution within bovine oocytes and preattachment embryos.

Growth hormone gene expression in oocytes and zygotes produced by cows heterozygous (Leu127Val) at GH locus

The present work describes analysis of the growth hormone gene (GH) expression in non-matured and in vitro matured bovine oocytes as well as zygotes after in vitro fertilization. The Leu/Val polymorphism described in the 5th exon of the bovine GH gene was applied to investigate the expression of genetic variants in the analyzed material. Experiments were performed on oocytes collected from heterozygous (LV) cows. Since developmental stages analyzed in this study are not transcriptionally active with regard to the GH gene, the analyzed transcripts were exclusively of maternal origin. According to our findings, GH transcript was observed in each analyzed sample. The expected heterozygous pattern of GH gene expression was found in non-matured oocytes. However, an unexpected variation in allelic distribution was noticed in matured oocytes and zygotes. A tendency was observed of a gradual disappearance of the heterozygous pattern (variant LV) ranging from 100% in non-matured oocytes, 70% in matured cells and 20% in zygotes. In some of analyzed samples, the expected heterozygous pattern was replaced by the VV variant in matured oocytes and either by VV or LL variants in zygotes. Possible mechanisms underlying the described phenomenon (in vitro culture conditions, transcript polyadenylation) are discussed. These results indicate a possible influence of sub-optimal in vitro culture conditions on the distribution of genetic variants of GH gene transcripts in bovine oocytes and zygotes.

Sperm pre-incubation prior to insemination affects the sex ratio of bovine embryos produced in vitro

The objective of the present study was to determine whether sperm incubation prior to oocyte insemination in vitro affects the sex ratio of resulting blastocyst. Cumulus-oocyte-complexes (COCs) collected from slaughterhouse ovaries were matured in vitro and inseminated with frozen-thawed semen of three proven artificial insemination (AI) bulls pre-incubated in vitro in Sperm-Talp for 6 and 24 h. On day-9 blastocysts were collected and processed for sex determination. More than 80% of blastocyst were successfully sexed. There were no significant differences in cleavage and blastocyst rates using sperm pre-incubated for 6 h as compared with the 0-h pre-incubation control group. The cleavage and blastocyst rates were significantly lower in the 24-h pre-incubation group. The male to female ratio, when compared with the theoretical 1 : 1, differed significantly in favour of females among hatched (viable) blastocysts derived from sperm pre-incubated for 24 h prior to insemination as well as among all blastocytsts in the 6-h group. Moreover, when the sperm treatment was considered, the sex ratio was affected only among hatched blastocysts in 24-h pre-incubation group. It was concluded that prolonged sperm pre-incubation influences the rate of development and the sex ratio among hatched blastocysts.

Expression of growth hormone and its transcription factor, Pit-1, in early bovine development

During bovine embryogenesis, bovine growth hormone (bGH) contributes to proliferation, differentiation, and modulation of embryo metabolism. Pituitary-specific transcription factor-1 (Pit-1) is a transcription factor that binds to promoters of GH, prolactin (PRL), and thyroid-stimulating hormone-beta (TSHbeta) encoding genes. A polymorphism in the fifth exon of the bGH gene resulting in a leucine (Leu) to valine (Val) substitution provides an Alu I restriction site when the Leu allele is present. To determine the onset of embryonic expression of the bGH gene, oocytes derived from ovaries homozygous for Leu alleles were fertilized in vitro with spermatozoa obtained from a Val homozygote. For each developmental stage examined, three separate pools of embryos composed of approximately 100 cell samples underwent RNA isolation, reverse transcription to cDNA, and amplification by nested PCR (nPCR). Bovine GH gene transcripts were identified at 2- to 4-cell (n = 162), 8- to 16-cell (n = 73), morulae (n = 51), and blastocyst (n = 15) stages. Likewise, transcripts for Pit-1 were detected at 2-cell (n = 125), 4-cell (n = 114), 8-cell (n = 56), 12-to-32-cell (n = 32), morulae (n = 68), and blastocyst (n = 14) stages. After digestion with Alu1, bGH cDNA was genotyped by restriction fragment length polymorphism (RFLP) analysis. Bovine GH mRNA was present in all pools of stages examined. Both Leu and Val alleles (maternal and paternal) were only detected in pools of embryos that had reached 8- to 16-cell stage. Results suggest that transcription of the bGH gene begins at the 8- to 16-cell stage in bovine embryos, possibly under control of the transcription factor, Pit-1, and that RFLP analysis of the bGH gene can be used to determine parental origin of transcripts in early embryonic development.

The use of HOS test to evaluate membrane functionality of boar sperm capacitated in vitro

The functional and structural integrity of sperm membrane are crucial for the viability of spermatozoa. The commonly used staining test (eosin + nigrosin) for assessing sperm membrane measures only its structural integrity. The hypoosmotic swelling test (HOS) originally developed for human sperm (Jeyendran et al. 1984) has been also applied to several species of domestic animals (bull, pig, horse, dog). The test enables to evaluate the functional status of the sperm membrane. The principle of HOS is based on water transport across the sperm tail membrane under hypoosmotic conditions. It has previously been used to assess the semen quality (Revell and Mrode 1994), to analyse fertilizing capacity (Rota et al. 2000; Perez-Llano et al. 2001) and also to detect viable, immotile cells for ICSI (Intra-cytoplasmic sperm injection) in human (Zeyneloglu et al. 2000). There are two procedures commonly used for sperm capacitation in the pig-sperm washing and incubation before insemination (Nagai 1994). Capacitation involves several changes like removing molecules coating the sperm head membrane, changes in membrane fluidity and intracellular ion concentration (Green and Watson 2001). Thus the membrane integrity as well as functionality may be affected as shown by Harrison (1996). The aim of the present study was to analyse changes in sperm membrane integrity after in vitro capacitation by use of the HOS test.

Quantitative aspect of gene expression analysis in mammalian oocytes and embryos

In vitro produced embryos, due to their lower developmental potential when compared to the in vivo derived counterparts, have been currently subjected to an intensive scientific investigation. Qualitative as well as quantitative analyses of gene expression (reverse transcription-polymerase chain reaction; RT-PCR) belong to the powerful tools providing a wide spectrum of data on the quality of oocytes and embryos. The main research areas in this topic concern the following categories: oocyte quality, developmental competence of in vitro produced (IVP) embryos also with regard to their sex, embryo metabolism, gene expression levels, embryo manipulation and cloning. There are many methods that have been applied to study gene expression, but only some of them meet the requirement of analysing small cell samples which usually is the case with oocytes or early embryos. This paper deals with the description of the current methods commonly used for quantitative gene expression in mammalian oocytes and preimplantation embryos with a special attention paid to the real time PCR.

Distribution of polymorphic forms at the porcine GH locus in a population of day-10 pig embryos

The present study describes an analysis of genotype and allele distribution at the porcine GH locus among day-10 pig embryos. Embryos were collected post mortem from 6 crossbred (Danish Landrace x Yorkshire) sows inseminated with mixed Duroc semen and individually frozen for later analysis. After extraction, DNA was subjected to PCR amplification and restriction analysis with Msp I and Hae II enzymes. The genotype frequencies were: Msp I CD 0.17, DD 0.83; and Hae II AA 0.33, AB 0.58; and BB 0.09. The Msp I CC genotype was not found among analysed embryos. To our knowledge, this is the first report on the genotype and allele distribution at the GH locus among early pig embryos.

In vitro maturation and fertilisation of bovine oocytes in relation to GH gene polymorphism (Leu/Val)

The present study describes the analysis of the associations between the growth hormone gene polymorphism (Leu/Val) and oocyte maturation and in vitro fertilisation in cattle. Two independent experiments were carried out. In the first one, oocytes were collected from 49 single ovaries, matured in vitro, measured and cytogenetically analysed. One ovary was considered as a donor. The procedure of the donor's genotyping at the GH locus was based on DNA extracted from the granulosa cells. The GH genotype did not influence the oocyte diameter nor the number of oocytes collected, which were selected for maturation and matured. An unreduced chromosome number was found in 8.8% of the cells at the second metaphase stage and 42.9% of the donors. This anomaly was observed in all genotype groups with a higher frequency in the VV cows (P < 0.01). In the second experiment, the oocytes collected from 72 single ovaries were matured and fertilised in vitro. The GH genotype of a donor did not influence the number of zygotes cleaved on day-2. It has to be mentioned, that due to the low frequency of the VV genotype (0.03), the results of the present study should be treated as preliminary and need further analysis.

The ploidy of in vitro matured bovine oocytes is related to the diameter

The aim of the present study was to investigate a possible relationship between bovine oocyte diameter and the ploidy after maturation in vitro. The cumulus-oocyte-complexes (COCs) were collected by slicing slaughterhouse ovaries and were matured in vitro in standard conditions. Oocytes were collected separately from each ovary and then processed in groups according to their origin. After maturation, the inside zona pellucida diameter of each cell was measured and cytogenetic slides were made. Four size categories were distinguished: <110, 110-115, 115-120 and >120 microm. Altogether, 600 oocytes derived from single ovaries of 50 donors were measured and cytogenetically analyzed. The diploid chromosome number (2MII) was found for 8.4% of oocytes (36/427) and for 44% of donors (22/50). The observed number of 2MII cells varied between 1 and 6 per donor. The size of secondary oocytes with unreduced chromosome numbers was significantly smaller (P < 0.01) than the haploid ones. We conclude that bigger oocytes underwent normal meiotic division, whereas their smaller counterparts tended to follow an abnormal path of maturation.

Growth hormone gene polymorphism and reproductive performance of AI bulls

Relationships between the growth hormone gene RFLP polymorphism and bull sperm characteristics were the objects of the present study. DNA was extracted from blood or sperm samples collected from 113 AI bulls and submitted for polymerase chain reaction (PCR) followed by digestion with Alu I restriction enzyme. The bGH genotypes were visualized on 10% polyacrylamide gel. The analyzed population of AI bulls consisted of dairy (Holstein Fresian [HF] crossbred [HF x Polish Black and White]) and beef breeds (Limousine, Charolaise, Piemontese, Angus and Hereford). The frequency of the Leu allele was 0.86 among dairy bulls and 0.38 in beef bulls (0.14 and 0.62 for the Val allele, respectively). Eight sperm characteristics and Day 60 non-return rates (NRR) were analyzed. The 3 genotype groups (LL, VV and LV) and the effect of production type (dairy or beef) on sperm characteristics were considered. None of the traits showed significant variability in relation to the bGH genotype, although a tendency was observed for LL bulls to have a lower ejaculate volume and VV bulls higher NRR. Moreover some statistically significant associations with production type were noticed: beef bulls were superior in sperm concentration and non-return rate, whereas dairy bulls excelled in individual fresh sperm motility.