Estimate of the population of preantral follicles in the ovaries of Bos taurus indicus and Bos taurus taurus cattle

Selecting oocyte donors based on anti-Müllerian hormone (AMH) concentrations: A critical analysis of using cutoff values as exclusion criterion for an in vitro embryo production program in Gir cattle

The aims of this study were to determine anti-müllerian hormone (AMH) cutoff values for selecting Gir (Bos taurus indicus) oocyte donors and estimate the impact of using AMH concentrations as a selection criterion. In Exp. 1, Gir heifers (n=120) were sampled for AMH analysis and submitted to ovum pick-up and in vitro embryo production (OPU-IVEP). AMH cutoff values were calculated using ROC analysis or, alternatively, by the successive exclusion of heifers with the lowest AMH values. The correlations between AMH and OPU-IVEP outcomes were significant (P<0.001), though low or moderate (r= 0.34-0.52). We estimated an improvement (P<0.05) after the use of AMH cutoff values to select donors of +15.3% for total oocyes, +19.4% for viable COC, and +23.4% for blastocysts. This selection pressure, however, led to the exclusion of 32.8%, 37.9%, and 50.0% of the initial potential donors, respectively. In Exp. 2, we analyzed data from OPU-IVEP sessions of 658 Gir donors with known genomic values for predicted transmitting ability for milk (GPTAm) and age at first calving (GPTAafc). The selection based on the number of oocytes recovered had no effect (P>0.05) on the average GPTAm nor GPTAafc values of the remaining donors. In summary, plasma AMH ≥700 pg/mL is a cutoff value that can be used to select Gir heifers with a greater potential as oocyte donors. Nevertheless, this selection leads to the exclusion of up to 50% of potential donors. Finally, exclusion of poor responders had no effect on mean genomic estimates for milk production or age at first calving in the selected subset of donors.

Method of Isolation and In Vitro Culture of Primordial Follicles in Bovine Animal Model

The mammalian ovary is a substantial source of oocytes arranged into follicles at various stages of folliculogenesis, from the primordial to the ovulatory ones. Primordial follicles constitute the most abundant source of gametes inside the mammalian ovary at any given time.The isolation of a high number of primordial follicles, together with the development of protocols for in vitro follicle growth, would provide a powerful tool to fully exploit the female reproductive potential and boost the rescue and restoration of fertility in assisted reproduction technologies in human medicine, animal breeding, and preservation of threatened species. However, the most significant limitation is the lack of efficient methods for isolating a healthy and homogeneous population of viable primordial follicles suitable for in vitro culture. Here, we provide a fast and high-yield strategy for the mechanical isolation of primordial follicles from limited portions of the ovarian cortex in the bovine animal model.

Oocyte quality in adapted Bos taurus taurus cows

The objective of the current study was to determine the performance of creole cows of the Chino Santandereano breed in the ultrasound-guided follicular aspiration technique (OPU) and the quality of oocytes recovered. A total of 15 multiparous cows were selected from a herd located in the department of Santander with tropical climate. The cows were submitted to 5 sessions of follicular aspiration with an interval of 45 days. In each aspiration session, 7.9 ± 0.7 oocytes were recovered per cow, with a recovery rate of 64.9% ± 0.5 and a rate of viable and non-viable oocytes of 64.3% ± 0.6 and 35.7% ± 0.7, respectively. A difference (P < 0.05) in oocyte quality was presented for grades I, II and III (7.7 ± 0.4, 19.8 ± 0.5 and 36.8 ± 0.5, respectively). The results suggest that Chino Santandereano cows submitted to the OPU technique have a higher percentage of grade III oocytes recovered.

PTEN inhibitor and kit ligand increase in vitro activation and survival of primordial follicles in alpaca

In mammals, activation of primordial follicles to primary follicle is a progressive and highly regulated process. There is evidence in mice that phosphatase and tensin homologue deleted on Chromosome 10 (PTEN) silencing is an important negative regulator of phosphatidylinositol 3-kinase (PI3K), which initiates activation of dormant follicles. The objective of the study was to evaluate the effect of the addition of PTEN inhibitor (bpV(HOpic)) (10 μM) and/or Kit Ligand (KL) (100 ng/mL) on the in vitro activation and survival of alpaca primordial follicles. Ovarian cortical fragments from 11 adult alpacas were cultured for 24 h in tissue culture medium (α-MEM+ ) supplemented with KL and bpV or the association of both. Subsequently, each sample was processed by classical histology and follicular counting and classification were performed. The results obtained show a reduction (p < 0.05) of primordial follicles in more than 50% in follicular tissue cultured in vitro in α-MEM+ or supplemented with bpV and/or KL versus the control (not cultured). Further, >25% increase in primary follicles in follicular tissue cultured in vitro in α-MEM+ or supplemented with KL and/or bpV versus control. However, the follicular survival rate showed a decrease of 20% in the cultured tissues, except for the α-MEM+ supplemented with KL and bpV. In conclusion, supplementation of bpV (HOpic) (10 μM) and KL (100 ng/mL) increased the activation in vitro of primordial follicles and survival after in vitro culture of alpaca ovarian tissue.

In vitro and in vivo embryo production efficiency in Flemish and Holstein donor females

The aim of this study was to compare embryo production efficiency in Flemish and Holstein donor females using ovum pick-up and in vitro fertilization (OPU-IVF) or in vivo production (superovulation; SOV) procedures. The study was conducted using a split-plot design, with eight Flemish and eight Holstein non-lactating cycling females. Females were subjected to ten weekly OPU/IVF sessions and/or two SOV/embryo collections sessions at a 63-day interval, for a total of 160 OPU-IVF and 32 SOV sessions. Mean numbers of follicles and corpora lutea, and cumulus-oocyte complex (COC) recovery rates were similar between breeds after the OPU and SOV sessions. However, Flemish donors yielded better quality grade II COCs (301, 41.9%) than Holstein females (609, and 202, 33.1%). Also, cleavage and blastocyst rates, and the total number and the mean number of viable embryos obtained after OPU-IVF were higher in Flemish (49.6% and 11.8%, and 63 and 11.8 per donor, respectively) than in Holstein (32.8% and 7.2%, and 34 and 7.2 per donor, respectively) females. Flemish females were also more efficient in yielding viable embryos after SOV (111, 7.3 per donor) than Holstein (48, 3.3 per donor) females. Overall, Flemish donor females had better responses to OPU-IVF or SOV procedures than Holstein counterparts. Irrespective of the breeds, SOV procedures were more efficient than OPU-IVF in yielding more viable embryos, under the conditions of this study. Both reproductive procedures were useful tools for the genetic conservation of the Flemish cattle breed in Southern Brazil.

Review: Environment of the ovulatory follicle: modifications and use of biotechnologies to enhance oocyte competence and increase fertility in cattle

The oocyte is the basis of life, supporting development from a fertilized cell to an independent multicellular organism. The oocyte's competence to drive the first cell cycles postfertilization are critical to embryonic survival and subsequent successful pregnancy. Coupled with the complex processes of follicle assembly, activation, differentiation, growth, and terminal maturation, oocyte developmental competence is gradually acquired during oocyte growth and meiotic maturation. Most reproduction management technologies and interventions are centered around these highly coordinated processes, targeting the ovarian follicle and the oocyte within. Thus, our objective was to highlight key aspects of oocyte and follicle development in cattle, and to discuss recent advances in oocyte and follicle-centered reproductive biotechnologies.

Spatial distribution of preantral follicles in ovarian parenchyma of bovine species

The goal of this study was to determine the distribution of preantral follicles in bovine ovaries. Follicular distribution in the ovaries (n = 12) was evaluated in the region of the greater curvature of the ovary (GCO) and the region close to the ovarian pedicle (OP) of Bos taurus indicus heifers of the Nelore breed. Two fragments were obtained from each region of the ovary (GCO and OP). The mean weight of the ovaries was 4.04 ± 0.32 g. The mean antral follicle count (AFC) was 54.58 ± 3.55 follicles (minimum and maximum variation of 30 and 71 follicles, respectively). In total, 1123 follicles were visualized in the region of the GCO; 949 (84.5%) of them were primordial follicles and 174 (15.5%) were developing follicles. The region close to the OP contained 1454 follicles, of which 1266 (87%) were primordial follicles and 44 (12.9%) were developing follicles. The OP region showed a higher proportion of intact follicles in the primordial (P < 0.0001) and primary (P = 0.042) stages compared with the GCO region. The proportion of secondary follicles was similar in the OP and GCO regions. The ovaries of two bovine females (16%; 2/12) contained multi-oocytes follicles, which were characterized as primary follicles. Therefore, the distribution of preantral follicles in the bovine ovary was heterogeneous, with the region close to the OP containing a greater number of preantral follicles compared with the GCO region (P < 0.05).

A refined culture system of oocytes from early antral follicles promotes oocyte maturation and embryo development in cattle

In brief

The proposed culture system improves the current state of in vitro culture of growing oocytes in the bovine species and allows access to the untapped gamete reserve, thus improving reproductive efficiency.

Abstract

The present study aimed to improve the in vitro culture of bovine oocytes collected from early antral follicles (EAFs) to support the progressive acquisition of meiotic and developmental competence. The rationale that drove the development of such a culture system was to maintain as much as possible the physiological conditions that support the oocyte growth and differentiation in vivo. To this extent, oocytes were cultured for 5 days, which parallels the transition from early to medium antral follicles (MAFs) in the bovine, and supports promoting a 3D-like structure were provided. Additionally, the main hormones (follicle-stimulating hormone, estradiol, progesterone, and testosterone) were added in concentrations similar to the ones previously observed in bovine EAFs. The meiotic arrest was imposed using cilostamide. The cultured cumulus-oocyte complexes (COCs) reached a mean diameter of 113.4 ± 0.75 µm and showed a progressive condensation of the chromatin enclosed in the germinal vesicle (GV), together with a gradual decrease in the global transcriptional activity, measured by 5-ethynyl uridine incorporation. The described morpho-functional changes were accompanied by an increased ability to mature and develop to the blastocyst stage in vitro, although not matching the rates obtained by MAF-retrieved oocytes. The described system improves the current state of in vitro culture of growing oocytes in the bovine species, and it can be used to increase the number of gametes usable for in vitro embryo production in animals of high genetic merit or with specific desirable traits.

Factors affecting the in vitro embryo production in buffalo (Bubalus bubalis): A review

Under natural and well-managed conditions, the buffalo has good reproductive and productive indices. However, in vitro embryo production (IVEP) has been used commercially to maximise the number of elite animals. In this species, several factors (donor management, in vitro culture medium, semen, in vitro conditions, embryo transfer) still affect the IVEP results. In addition, the cost of this technique is very high for this purpose. Therefore, more studies, as well as adequate plans, are needed to achieve this objective efficiently. In this review, we discussed the current commercial status, influencing factors (in vivo and in vitro), and the progress and future challenges of IVEP in buffalo. A total of 81 references were used from 1979 to 2022. The relevant data or literature were searched using the following databases: Google, ResearchGate, Science Alert, Science Direct and PubMed, using the following keywords: buffalo oocytes/COCs, buffalo embryos, pregnancy and calving or live birth rate after embryo transfer. The best maturation, cleavage and blastocyst rates in the in vitro production of buffalo embryos were 95.8, 75.2 and 33.4%, respectively. The pregnancy and live birth rates ranged from 22.2% to 43.5% and from 15.3% to 36.5%, respectively, after the transfer of fresh embryos produced in vitro to the recipients. This review will help to contextualise IVEP in buffaloes, as well as create an adequate plan for implementing IVEP in buffaloes.

Fertility preservation: improved neovascularization and follicle viability in cryopreserved bovine ovarian cortex transplants by remaining medulla tissue

OBJECTIVE

To investigate the advantages of cryopreserved medulla-containing ovarian cortex grafts with those of commonly used sole cortex grafts for fertility preservation by analyzing tissue quality, neovascularization processes, and the number of vital follicles.

DESIGN

Experimental setting of cryopreserved bovine ovarian cortex tissue grafts with or without medulla tissue.

SETTING

Laboratory animal research at Ulm University, Ulm, Germany.

ANIMALS

Bovine ovaries and fertilized chicken eggs.

INTERVENTION(S)

Experimental setting of bovine ovarian tissue samples grafted on the chicken chorioallantoic membrane (CAM) after cryopreservation and thawing to examine histologic tissue integrity, apoptosis and proliferation immunohistochemically, blood vessel counts and determine the presence of neutral red-stained vital follicles.

MAIN OUTCOME MEASURE(S)

We used hematoxylin and eosin staining to visualize tissue structures, immunohistochemistry with anti-caspase 3 to detect apoptosis, anti-Ki67 to examine proliferation, blood vessel count on the chicken CAM to investigate neovascularization processes, and neutral red staining to evaluate vital follicles.

RESULT(S)

We demonstrated that in all analyzed tissue samples, after cryopreservation, thawing, and grafting on the chicken CAM, there was excellent tissue integrity and quality, as shown by extremely rare apoptosis processes analyzed using immunohistochemical caspase 3 staining (sole cortex, 0.54%; thin medulla-containing cortex, 0.43%; thick medulla-containing cortex, 0.13%; and sole medulla, 2.82%). Moreover, we detected increased neovascularization in the vicinity of medulla and medulla-containing grafts (small blood vessels: cortex 8.7, thin medulla-containing cortex 9.9, thick medulla-containing cortex 9.7, and medulla 9.8; very small blood vessels: cortex 7.0, thin medulla-containing cortex 13.0, thick medulla-containing cortex 12.0, and medulla 15.0), with higher Ki67-detected proliferation (cortex, 17.58%; thin medulla-containing cortex, 20.28%; thick medulla-containing cortex, 20.56%; and medulla, 29.9%). Additionally, we identified an increased number of vital follicles in medulla-containing cortex grafts compared with the number of vital follicles in sole cortex tissue (cortex, 256.1; thin medulla-containing cortex, 338.2; thick medulla-containing cortex, 346.6; and medulla, 8.1).

CONCLUSION(S)

In this experimental setting, bovine medulla-containing cortex tissue had excellent tissue structure and quality after cryopreservation and thawing and increased neovascularization and an augmented vital follicle count after grafting than the commonly used sole cortex tissue. Therefore, we suggest reconsidering the current cryopreservation and grafting processes in humans for fertility preservation by favoring retain medulla tissue at the ovarian cortex.

Characterization of preantral follicle clustering and neighborhood patterns in the equine ovary

Understanding the transition from quiescent primordial follicles to activated primary follicles is vital for characterizing ovarian folliculogenesis and improving assisted reproductive techniques. To date, no study has investigated preantral follicle crowding in the ovaries of livestock or characterized these crowds according to follicular morphology and ovarian location (portions and regions) in any species. Therefore, the present study aimed to assess the crowding (clustering and neighborhood) patterns of preantral follicles in the equine ovary according to mare age, follicular morphology and developmental stage, and spatial location in the ovary. Ovaries from mares (n = 8) were collected at an abattoir and processed histologically for evaluation of follicular clustering using the Morisita Index and follicular neighborhoods in ovarian sections. Young mares were found to have a large number of preantral follicles with neighbors (n = 2,626), while old mares had a small number (n = 305). Moreover, young mares had a higher number of neighbors per follicle (2.6 ± 0.0) than old mares (1.2 ± 0.1). Follicle clustering was shown to be present in all areas of the ovary, with young mares having more clustering overall than old mares and a tendency for higher clustering in the ventral region when ages were combined. Furthermore, follicles with neighbors were more likely to be morphologically normal (76.5 ± 6.5%) than abnormal (23.5 ± 6.5%). Additionally, morphologically normal activated follicles had increased odds of having neighbors than normal resting follicles, and these normal activated follicles had more neighbors (2.6 ± 0.1) than normal resting follicles (2.3 ± 0.1 neighbors). In the present study, it was demonstrated that preantral follicles do crowd in the mare ovary and that clustering/neighborhood patterns are dynamic and differ depending on mare age, follicular morphology, and follicular developmental stage.

Anti-Müllerian hormone as an endocrine biomarker of reproductive longevity and assessment of Single Nucleotide Polymorphisms in AMH gene of Bos indicus breeds of cattle

Anti-Müllerian hormone (AMH) is a member of the TGF-β superfamily produced by follicular granulosa cells (GCs) in women and cattle and is considered an endocrine biomarker of ovarian follicular reserve. The study examined how age and parity influence serum AMH concentration and investigated the presence of Single Nucleotide Polymorphisms in AMH gene in Bos indicus breeds viz Malnad Gidda Amritmahal and Hallikar. All five exons of AMH gene amplified by Polymerase Chain Reaction (PCR) were subjected to Sanger sequencing and identified important SNP and its effects. We observed a highly significant relationship between parity and AMH concentration in Amritmahal cattle, whereas Malnad Gidda and Hallikar breeds did not show a significant difference. We identified one SNP located in exon 5 (rs21402788) with base change A>G, a non-synonymous mutation resulting in a change in amino acid Q>R and the protein product. It is concluded that AMH level could be considered as an indicator of the ovarian reserve and productive herd life (longevity) irrespective of age/parity, especially in Bos indicus breeds of cattle.

Impact of the antioxidant quercetin on morphological integrity and follicular development in the in vitro culture of Bos indicus female ovarian fragments

We evaluated the effect of quercetin on the in vitro culture of bovine ovarian fragments in relation to morphology, development, and oxidative stress. Ovaries (n = 12) from Nelore heifers (n = 6) were used. Each pair of ovaries was divided into nine fragments, and one fragment from each animal was fixed in Bouin solution for 24 h (histology control) or frozen (- 80°C; control for oxidative stress). Other ovarian fragments (n = 8) were distributed into concentrations of 0, 10, 25, and 50 μg/mL of quercetin added to the culture medium for 5 or 10 d. Data were analyzed by chi-square test or ANOVA followed by Tukey's test (P < 0.05). Treatment with 25 μg/mL quercetin resulted in the highest proportion of total intact follicles for 5 (67.3%) and 10 d (57.1%); the concentration of 25 μg/mL also presented the best proportion of developing follicles for 5 d (68.7%) and 10 d (62.8%). Treatment with 25 μg/mL quercetin resulted in significant ferric reduction for 10 d of culture, but not for 5 d. No difference (P > 0.1) was observed in the production of reactive oxygen species or in the oxidative degradation of lipids between treatments and non-cultivated controls. Treatment with 25 μg/mL quercetin preserved the morphological integrity of the developing follicles for 5 and 10 d of culture, in addition to promoting the best antioxidant potential after 10 d of culture in bovine ovarian fragments.

Culture of preantral ovarian follicles of Bos taurus indicus with alpha-lipoic acid

The aim of this study was to evaluate follicular development, morphological integrity, and antioxidant potential of preantral ovarian follicles from Bos taurus indicus females grown in vitro with alpha-lipoic acid. Ovaries (n = 24) of Bos taurus indicus (n = 12) females were collected during slaughter and fragmented. A randomly obtained fragment from each pair of ovaries was fixed in Bouin (non-cultivated control; D0). These fragments were intended for classical histology (morphology and evaluation of follicular growth), and a fragment from each pair of ovaries was frozen at -80°C (non-cultivated control; D0), and assigned for analysis of oxidative stress [thiobarbituric acid reactive substances (TBARS), nitroblue tetrazolium (NBT), and ferric reducing antioxidant power (FRAP)]. The remaining fragments were cultured in vitro for 6 (D6) or 12 (D12) days, containing only minimum essential medium (MEM) or MEM supplemented with alpha-lipoic acid (50, 100, or 250 ng/ml), on an extracellular matrix of agarose gel, in an oven at 38.5ºC. Every 2 days, 100% of the culture medium was replaced. Supplementation with 100 ng/ml was effective for maintaining follicular integrity after 6 days of culture (primordial: 51.28%; development: 36.88%; P < 0.0001). There was no difference (P > 0.05) between treatments compared with the non-cultivated control treatment (D0), using the NBT and TBARS assays. Therefore, supplementation of the in vitro culture medium of bovine preantral ovarian follicles with a concentration of 100 ng/ml of alpha-lipoic acid at 6 days of culture was effective for maintaining follicular integrity and, after 6 days, maintaining stable levels of reactive oxygen species.

Comparison of Ovarian Morphology and Follicular Disturbances between Two Inbred Strains of Cotton Rats (Sigmodon hispidus)

Simple Summary

Multi-oocyte follicles have been reported in several mammals, especially in rabbits and hamsters, although their significance remains unclear. The present study compared ovarian histology, focusing on folliculogenesis, between two inbred cotton rat strains maintained at Hokkaido Institute of Public Health and the University of Miyazaki. Abundant multi-oocyte follicles and double-nucleated oocytes were observed in the Hokkaido strain, whereas Miyazaki had fewer multi-oocyte follicles and lacked double-nucleated oocytes. These findings indicate that early folliculogenesis events such as oocyte nest breakdown and oocyte vitality, rather than proliferation and cell death in each oocyte, affect the unique ovarian phenotypes found in cotton rats, including multi-oocyte follicles or double-nucleated oocytes, and their differences between strains. Therefore, these results can clarify mammalian folliculogenesis and its abnormal processes.

Abstract

Most mammalian ovarian follicles contain only a single oocyte having a single nucleus. However, two or more oocytes and nuclei are observed within one follicle and one oocyte, respectively, in several species, including cotton rat (CR, Sigmodon hispidus). The present study compared ovarian histology, focusing on folliculogenesis, between two inbred CR strains, HIS/Hiph and HIS/Mz. At 4 weeks of age, ovarian sections from both the strains were analyzed histologically. Multi-oocyte follicles (MOFs) and double-nucleated oocytes (DNOs) were observed in all stages of developing follicles in HIS/Hiph, whereas HIS/Mz had MOFs up to secondary stages and lacked DNOs. The estimated total follicles in HIS/Mz were almost half that of HIS/Hiph, but interstitial cells were well developed in HIS/Mz. Furthermore, immunostaining revealed no clear strain differences in the appearance of oocytes positive for Ki67, PCNA, and p63 in MOF or DNOs; no cell death was observed in these oocytes. Ultrastructural analysis revealed more abundant mitochondrial clouds in oocytes of HIS/Hiph than HIS/Mz. Thus, we clarified the strain differences in the CR ovary. These findings indicate that early events during folliculogenesis affect the unique ovarian phenotypes found in CRs, including MOFs or DNOs, and their strain differences.

Recreating the Follicular Environment: A Customized Approach for In Vitro Culture of Bovine Oocytes Based on the Origin and Differentiation State

The mammalian ovary is a large source of oocytes organized into follicles at various stages of folliculogenesis. However, only a limited number of them can be used for in vitro embryo production (IVEP), while most have yet to complete growth and development to attain full meiotic and embryonic developmental competence. While the in vitro growth of primordial follicles in the ovarian cortex has the potential to produce mature oocytes, it is still at an experimental stage. The population of early antral follicles (EAFs), instead, may represent a reserve of oocytes close to completing the growth phase, which might be more easily exploited in vitro and could increase the number of female gametes dedicated to IVEP.Here we present in vitro culture strategies that have been developed utilizing physiological parameters to support the specific needs of oocytes at distinct stages of differentiation, in order to expand the source of female gametes for IVEP by maximizing the attainment of fertilizable oocytes. Furthermore, these culture systems provide powerful tools to dissect the molecular processes that direct the final differentiation of the mammalian oocyte.

Occurrence, morphology, and morphometry of follicles containing multiple oocytes in FecGE mutant Santa Inês ewes

This study was conducted to characterize the morphology and morphometry of follicles containing multiple oocytes (MOFs) and determine the association with the FecG^E mutation in Santa Inês ewes. Based on the genotypes, 65 ewes were characterized as being homozygous wild-type (n = 25; FecG^+/+), heterozygous mutant (n = 27, FecG^+/E), and homozygous mutant (n = 13, FecG^E/E). The variables evaluated were follicle developmental stage, number of oocytes per follicle, morphology, and morphometry of MOFs. The FecG^E mutation did not affect the frequency of MOFs (P > 0.05) (3.0 % in FecG^+/+; 3.3 % in FecG^+/E; and 3.5 % in FecG^E/E). The greater viability (P < 0.05) of MOFs was identified in transitory stage of the FecG^E/E (95.0 %) and FecG^+/E (90.9 %) when compared to the FecG^+/+ genotype (73.3 %). Furthermore, the morphology of transitory follicles with two oocytes was the variable and when evaluated was the most reliable determinant for predicting which ewes had an FecG^E mutation. In conclusion, the FecG^E mutation did not affect the frequency of MOFs. The ewes with FecG^E mutation had a greater frequency of morphologically normal MOFs in the transitory stage. Furthermore, the ewes with the FecG^E mutation had a greater likelihood of having MOFs containing two morphologically normal oocytes.

Unique morphological characteristics in the ovary of cotton rat (Sigmodon hispidus)

Cotton rats (Sigmodon hispidus, CRs) are commonly used as animal models in biomedical research. However, the reproductive characteristics and ovarian development in the CRs has not been widely investigated. We have previously shown that female CRs, in particular, show several unique phenotypes associated with the urogenital system, such as chronic kidney disease and pyometra. Our investigation revealed unique morphologies in CR ovaries, particularly in oocytes. Cotton rat ovaries at 6-8 weeks of age were obtained from the Hokkaido Institute of Public Health, and their sections analyzed by light microscopy and transmission electron microscopy. Although the general histology and folliculogenesis of CR ovaries were similar to those of other experimental rodents, multi-oocyte follicles (MOFs) and double nucleated oocytes (DNOs) were also observed. Although MOFs were found at all stages of follicular development, a greater frequency of MOFs was observed in the primary and secondary stages. However, DNOs tended to be frequently observed in primordial follicles. Almost all MOF oocytes and a few DNOs possessed a clear zona pellucida, expressed DEAD (Asp-Glu-Ala-Asp) box polypeptide 4 and Forkhead box protein 2, a representative marker of oocytes and follicular epithelial cells. Thus, our investigations revealed the unique phenotypes of the CR ovary. As MOFs and DNOs are occasionally observed in human patients with infertility, the CR would be a useful animal model to study for gaining a better understanding of folliculogenesis and oocytogenesis, as well as their abnormalities in humans and other animals.

Supportive techniques to investigate in vitro culture and cryopreservation efficiencies of equine ovarian tissue: A review

During the reproductive lifespan of a female, only a limited quantity of oocytes are naturally ovulated; therefore, the mammalian ovary possesses a substantial population of preantral follicles available to be handled and explored in vitro. Hence, the manipulation of preantral follicles enclosed in ovarian tissue aims to recover a considerable population of oocytes of high-value animals for potential application in profitable assisted reproductive technologies (ARTs). For this purpose, the technique of preantral follicle in vitro culture (IVC) has been the most common research tool, achieving extraordinary results with offspring production in the mouse model. Although promising outcomes have been generated in livestock animals after IVC of preantral follicles, the quantity and quality of embryo production with those oocytes are still poor. In recent years, the mare has become an additional model for IVC studies due to remarkable similarities with women and livestock animals regarding in vivo and in vitro ovarian folliculogenesis. For a successful IVC system, several factors should be carefully considered to provide an optimum culture environment able to support the viability and growth of preantral follicles enclosed in ovarian tissue. The cryopreservation of the ovarian tissue is another important in vitro manipulation technique that has been used to preserve the reproductive potential in humans and, in the future, may be used in highly valuable domestic animals or endangered species. Several improvements in cryopreservation protocols are necessary to support the utilization of ovarian tissue of different species in follow-up ARTs (e.g., ovarian fragment transplantation). This review aims to provide an update on the most current advances regarding supportive in vitro techniques used in equids to evaluate and manipulate preantral follicles and ovarian tissue, as well as methodological approaches used during IVC and cryopreservation techniques.

Genetic analysis of in-vitro embryo production traits in Dairy Gir cattle

The potential of dams as oocyte donors can be a selection criterion for animal breeding programs, but also an involuntary driver of the process. In both cases, it is important to determine genetic components influencing the outcome of in vitro embryo production (IVEP). The objective of the present study was to perform a detailed genetic analysis for in vitro embryo production traits in Dairy Gir cows. A dataset containing 11,450 records of ovum pick-up (OPU) and in vitro fertilization (IVF) procedures from 2684 Dairy Gir donors was evaluated. Analyzed traits were number (N_OV) and percentage (P_OV) of viable oocytes; number (N_GI) and percentage (P_GI) of grade I oocytes; number (N_EMB) and percentage (P_EMB) of viable embryos. All analyzes were performed using animal models by a Bayesian framework. Heritability estimates varied from 0.16 to 0.32 for count traits and from 0.01 to 0.06 for percentage traits. The proportion of the total variation represented by the additive genetic effect of sire (semen used in IVF) for N_EMB and P_EMB was 7% and 5% respectively. Associations between estimated breeding values from progeny tested bulls for IVEP traits, milk production, age at first calving and conformation traits were mainly low or close to zero. Results indicate that selection for IVEP traits is possible in Dairy Gir cattle and would not impair genetic progress for traits already considered as selection criteria. The N_OV seems to be a promising target trait. However, a selection index could help to avoid the use of sires with negative genetic merit for percentage traits, minimizing possible deterioration in the long term.

Gonadotropin priming before OPU: What are the benefits in cows and calves?

Oocyte pick up (OPU) coupled with IVP produce over 1 million cattle embryos per year and has been most successful in Bos indicus derived breeds that contain large numbers of antral follicles on their ovaries. More recently, this technology has been applied on a large scale to Bos taurus cattle, where hormone manipulation is generally employed to improve the developmental competence of the COCs. Hormone manipulation, and specifically the use of FSH priming before OPU, has been strategically used in the intensively managed dairy cow, where genomic evaluation and juvenile IVP can produce additional significant genetic gains.

Brangus cows have ovarian reserve parameters more like Brahman than Angus cows

Bos indicus females have more surface antral follicles than Bos taurus females; however, histological studies demonstrated no difference in total number of primordial follicles between these two biological types of cattle. Primordial follicle density in the ovary was less in Nelore ovaries compared to Angus ovaries, but no studies have examined the primordial follicle density in Bos indicus cross-bred females. It, therefore, was hypothesized that primordial follicle density in the ovary would decrease as percentage Bos indicus increased. Ovaries were collected from cross-bred Angus (n = 32, no Bos indicus influence), Brangus (n = 15), or Brahman (n = 9) cows and prepared for histological evaluation. There was no difference in total number of primordial follicles per ovary between breeds (P > 0.10). When numbers of primordial follicles were expressed on a per gram of ovarian tissue basis, there were fewer primordial follicles per gram of ovarian tissue in Brangus and Brahman cows than in Angus cows (P < 0.05). Brangus cows did not differ from Brahman cows in primordial follicle density (P > 0.10). Differences in primordial follicle density could indicate differences in capacity of ovarian stroma to produce factors necessary for oogonial proliferation and primordial follicle formation among breeds. Identifying these factors could improve the aprroach for culturing pre-antral follicles of cattle. Furthermore, these results explain why ultrasonographic antral follicle counts may need to be adjusted to a greater threshold to predict size of the ovarian reserve and determine ovarian reserve related reproductive traits in Bos indicus females.

Higher antral follicular count is associated with body weight in peri-pubertal Murrah buffalo heifers

AMH had no correlation with AFC and BW, but AFC was correlated with BW in high antral follicular group heifers. Furthermore, this study shows that AMH exhibited a trend with AFC in peri-pubertal buffalo heifers.

Spatial distribution of preantral follicles in the equine ovary

Comprehensive studies on spatial distribution of preantral follicles in the ovary are scarce. Considering that preantral follicles represent the main ovarian reserve, harvesting of these follicles is crucial for the development/use of assisted reproductive techniques. Therefore, knowledge on follicle spatial distribution can be helpful for targeting areas with richer number of preantral follicles through biopsy procedures. The aim of this study was to assess the distribution and localization of equine preantral follicles according to: (i) age, (ii) ovarian portion (lateral and intermediary) and region (dorsal and ventral), (iii) distance from the geometric center, and (iv) follicular class. Ovaries from young and old mares (n = 8) were harvested in a slaughterhouse and submitted to histological processing for further evaluation. For data analyses, a novel methodology was developed according to the geometric center of each histological section for a precise determination of preantral follicle distribution. Results indicated that (i) equine preantral follicles are clustered and located near to the ovarian geometric center, and that aging induced their dispersion through the ovarian cortex; (ii) the distance from the geometric center was shorter for developing follicles than primordial; and (iii) secondary follicles were more distant from the geometric center but closer to the ovulation fossa. In conclusion, the spatial distribution of preantral follicles was successfully determined in the equine ovary and was affected by age, region, and portion.

Regional distribution and integrity of equine ovarian pre-antral follicles

The goal of this study was to determine the distribution of pre-antral follicles in the ovarian parenchyma of mares. For Experiment 1, each ovary was cut longitudinally at the greater curvature, performing two hemiovaries. After that, six fragments from each hemiovary were obtained, resulting in 12 fragments, which were divided into the innermost region of the parenchyma, the middle region and the outermost region. All the three obtained sections were cut transversally to obtain two fragments from each one. For Experiment 2, each ovary also submitted to a longitudinal cut on the greater curvature, forming two hemiovaries. Each hemiovary was sectioned into four symmetrical fragments, resulting in eight fragments per ovary. The fragments were related as being near to or far from the ovulatory fossa. The fragments of both experiments were immediately fixed in Carnoy for 12 hr and kept in 70% ethanol for 24 hr. Follicles were classified according to the stages of development and for morphological integrity according to oocyte morphology and granulosa cells. After the histological assessment, a total of 1,130 follicles were visualized from Experiment 1, being 1,054 (93.3%) primordial follicles and 76 (4.7%) follicles in development. The innermost region had the highest percentage of pre-antral follicles compared to the other regions (p < .05). The middle and outermost regions showed higher percentages of intact primordial and developing follicles than the innermost region (p < .05). Considering Experiment 2, 938 follicles were found, being 894 (95.3%) primordial and 44 (4.7%) follicles in development. The region near the ovulatory fossa presented higher (58.7%; 551 of 938) follicular concentration compared to the region far from the ovulatory fossa (41.3%; 387 of 938; p < .05). As a conclusion, distribution of pre-antral follicles in the equine ovary has a specific pattern through the parenchyma. Also, the follicular integrity differed in the studied ovarian areas.

Ovarian features in white-tailed deer (Odocoileus virginianus) fawns and does

The knowledge about ovarian reserve is essential to determine the reproductive potential and to improve the methods of fertility control for overpopulated species, such as white-tailed deer (Odocoileus virginianus). The goal of this study was to evaluate the effect of age on the female reproductive tract of white-tailed deer, focusing on ovarian features. Genital tracts from 8 prepubertal and 10 pubertal females were used to characterize the preantral follicle population and density, morphology, distribution of follicular classes; stromal cell density; and apoptosis in the ovary. In addition, uterus and ovary weights and dimensions were recorded; and the number and the size of antral follicles and corpus luteum in the ovary were quantified. Overall, fawns had a greater (P < 0.05) preantral follicle population, percentage of normal follicles, and preantral follicle density than does. The mean stromal cell density in ovaries of fawns and does differed among animals but not between age groups. The apoptotic signaling did not differ (P > 0.05) between the ovaries of fawns and does. However, apoptotic ovarian cells negatively (P < 0.001) affected the preantral follicle morphology and density, and conversely, a positive correlation was observed with stromal cell density. As expected, the uteri and ovaries were larger (P < 0.002) and heavier (P < 0.001) in does than in fawns. In conclusion, this study has shown, for the first time, the preantral follicle population and distribution of classes, rate of morphologically normal follicles, and density of preantral follicles and stromal cells in white- tailed deer. Therefore, the findings herein described lead to a better understanding of the white-tailed deer ovarian biology, facilitating the development of new methods of fertility control.

Do female dingo–dog hybrids breed like dingoes or dogs?

Hybridisation between animals that breed once (e.g. dingoes) and twice (e.g. domestic dogs) annually may produce offspring that breed either way. This question was investigated by determining the breeding seasonality of female dingo–dog hybrids in south-east Queensland, Australia, through evaluating macroscopic and histological features of 71 female reproductive tracts. All animals were sourced from urban areas where levels of hybridisation are generally high. Most animals trapped in summer were pups less than 6 months of age. A peak of uterus diameter and weight coincided with a peak of corpus luteum in winter. The follicular phase was characterised by growing follicles, ~1–3 mm wide, in late summer and autumn. Only two of the animals (1.4%) showed out-of-season reproductive cycles: one was found with corpus luteum in summer and another in autumn. Our data clearly show that hybrids have a single annual breeding season in winter, exhibiting the same breeding seasonality as dingoes. Our findings are similar to those found in the New Guinea singing dog. Future studies should be conducted to understand and exploit the mechanism and drivers of the breeding seasonality of dingo–dog hybrids to develop more effective management of their populations.

Systemic and local anti-Mullerian hormone reflects differences in the reproduction potential of Zebu and European type cattle

This study was conducted to evaluate plasma anti-Mullerian hormone (Pl AMH), follicular fluid AMH (FF AMH) and granulosa cell AMH transcript (GC AMH) levels and their relationships with reproductive parameters in two cattle subspecies, Bos taurus indicus (Zebu), and Bos taurus taurus (European type cattle). Two-dimensional ultrasound examination and serum collection were performed on Zebu, European type and crossbreed cows to determine antral follicle count (AFC), ovary diameter (OD) and Pl AMH concentration. Slaughterhouse ovaries for Zebu and European type cattle were collected to determine FF AMH concentrations, GC AMH RNA levels, AFC, oocyte number, cleavage and blastocyst rate. Additionally GC AMH receptor 2 (AMHR2) RNA level was measured for European type cattle. Relationship between AMH and reproductive parameters was found to be significantly greater in Zebu compared to European cattle. Average Pl AMH mean ± SE for Zebu and European cattle was 0.77 ± 0.09 and 0.33 ± 0.24 ng/ml respectively (p = 0.01), whereas average antral FF AMH mean ± SE for Zebu and European cattle was 4934.3 ± 568.5 and 2977.9 ± 214.1 ng/ml respectively (p < 0.05). This is the first published report of FF and GC AMH in Zebu cattle. Levels of GC AMHR2 RNA in European cattle were correlated to oocyte number (p = 0.01). Crossbred animals were found more similar to their maternal Zebu counterparts with respect to their Pl AMH to AFC and OD relationships. These results demonstrate that AMH reflects differences between reproduction potential of the two cattle subspecies therefore can potentially be used as a reproductive marker. Furthermore these results reinforce the importance of separately considering the genetic backgrounds of animals when collecting or interpreting bovine AMH data for reproductive performance.

Ultrastructural changes in oocytes during folliculogenesis in domestic mammals

The ultrastructural analysis of oocytes and ovarian follicles has been used to evaluate the effects of assisted reproductive techniques, such as cryopreservation or in vitro oocyte maturation. It also benefits the understanding of such complex mechanisms that occur during folliculogenesis. From the beginning of primordial follicles growth until oocyte maturation in preovulatory follicles oocyte cytoplasmic organelles undergo dynamic alterations that reflect physiological changes and development. This review aims to make a retrospective survey of the relevant features of follicles and oocytes ultrastructure, highlighting the differences between mammalian species, specially the domestic ones.

Plasma anti-mullerian hormone: an endocrine marker for in vitro embryo production from Bos taurus and Bos indicus donors

The aim of this study was to evaluate the association between plasma anti-mullerian hormone (AMH) concentration and in vitro embryo production (IVP) from Bos taurus (Holstein) and Bos indicus (Nelore) donors. A total of 59 Holstein (15 prepubertal heifers aged 8-10 mo, 15 cyclic heifers aged 12-14 mo, 14 lactating cows, and 15 nonlactating cows) and 34 Nelore (12 prepubertal heifers aged 10-11 mo, 10 prepubertal heifers aged 21-23 mo, and 12 cyclic heifers aged 24-26 mo) females were enrolled. All females underwent an ovum pick-up (OPU), without previous synchronization of the follicular wave, and IVP procedure. Immediately before the OPU procedure, blood samples were collected for subsequent AMH determination. A positive correlation was observed between the plasma AMH and number of in vitro embryos produced from Holstein (r = 0.36, P < 0.001) and Nelore (r = 0.50, P = 0.003) donors. For additional analyses, donors within each genotype were classified into 1 of 2 AMH categories (low or high) according to the average AMH concentration for each genotype. The results revealed that females classified as having high AMH presented a greater number of visible aspirated follicles (Holstein: 20.9 ± 1.5 vs 13.6 ± 0.9, P < 0.0001; Nelore: 54.3 ± 6.1 vs 18.6 ± 2.1, P < 0.0001) and a greater number of recovered cumulus-oocyte complexes (Holstein: 17.3 ± 1.5 vs 9.0 ± 0.9, P < 0.0001; Nelore: 45.3 ± 6.4 vs 13.4 ± 1.7, P < 0.0001). However, there was no difference in the blastocyst production rate (Holstein: 20.6% ± 4.0% vs 19.8% ± 4.2%, P = 0.60; Nelore: 33.7% ± 6.5% vs 27.4% ± 5.5%, P = 0.41, high and low AMH, respectively). Moreover, donors classified as having high AMH yielded a greater number of embryos produced per OPU (Holstein: 3.0 ± 0.7; Nelore: 7.0 ± 1.7) compared with those classified as having low AMH (Holstein: 1.2 ± 0.3, P = 0.04; Nelore: 2.2 ± 0.5, P = 0.007). In conclusion, although the plasma AMH concentration did not alter the ability of the cumulus-oocyte complex to reach the blastocyst stage, the AMH concentration in plasma can be an accurate endocrine marker for the in vitro embryo yield from either B. taurus (Holstein) or B. indicus (Nelore) donors. Therefore, AMH is a promising tool to enhance the overall efficiency of OPU-IVP programs in the field as a selective criterion for high embryo producing donors.

Incorporation of genetic technologies associated with applied reproductive technologies to enhance world food production

Animal breeding and reproductive physiology have been closely related throughout the history of animal production science. Artificial insemination provides the best method of increasing the influence of sires with superior genetics to improve production traits. Multiple ovulation embryo transfer (MOET) provides some ability to increase the genetic influence of the maternal line as well. The addition of genetic technologies to this paradigm allows for improved methods of selecting sires and dams carrying the best genes for production and yield of edible products and resistance to diseases and parasites. However, decreasing the number of influential parents within a population also increases the risk of propagating a recessive gene that could negatively impact the species (Reprod Domest Anim 44:792-796, 2009; BMC Genomics 11:337, 2010). Furthermore, antagonistic genotypic relationships between production traits and fertility (Anim Prod Sci 49:399-412, 2009; Anim Genet 43:442-446, 2012) suggest that care must be taken to ensure that increasing the frequency of genes with a positive influence on production does not negatively impact the fertility of the replacement females entering the herd.