Ovarian follicle size or growth rate can both be determinants of ovulatory follicle selection in mice†.

The endocrinology regulating ovulation of the desired number of oocytes in the ovarian cycle is well described, particularly in mono-ovulatory species. Less is known about the characteristics that make one follicle suitable for ovulation while most other follicles die by atresia. Bromodeoxyuridine (BrdU) injection was used to characterize granulosa cell proliferation rates in developing ovarian follicles in the estrous cycle of mice. This methodology allowed identification of follicle diameters of secondary (80-130 µm), follicle-stimulating hormone (FSH)-sensitive (130-170 µm), FSH-dependent (170-350 µm), and preovulatory (>350 µm) follicles. Few preovulatory-sized follicles were present in the ovaries of mice at estrus, the beginning of the cycle. Progressive increases were seen at metestrus and diestrus, when full accumulation of the preovulatory cohort (~10 follicles) occurred. BrdU pulse-chase studies determined granulosa cell proliferation rates in the 24-48 h before the follicle reached the preovulatory stage. This showed that slow-growing follicles were not able to survive to the preovulatory stage. Mathematical modeling of follicle growth rates determined that the largest follicles at the beginning of the cycle had the greatest chance of becoming preovulatory. However, smaller follicles could enter the preovulatory follicle pool if low numbers of large antral follicles were present at the beginning of the cycle. In this instance, rapidly growing follicles had a clear selection advantage. The developing follicle pool displays heterogeneity in granulosa cell proliferation rates, even among follicles at the same stage of development. This parameter appears to influence whether a follicle can ovulate or become atretic.

Impact of the corpus luteum and follicular parameters on the levels of plasma progesterone and the prediction of pregnancy in Holstein dairy cows.

The objective of this study was to investigate the reliability of corpus luteum and dominant follicles, imaging parameters on the plasma progesterone, and prediction of pregnancy in cows. In total, 48 cows were used in this study and underwent Ovsynch program. Ultrasound imaging of the ovaries was done at the time of PG shots. Corpus luteum diameter (CL_d), area (CL_area), volume (CL_vol), and pixels (CL_PXL), as well as dominant follicle diameter (F_d) and area (F_area), were estimated using the ImageJ program. Blood samples were taken to assess progesterone (P4) concentrations. Pregnancy status was determined at 32 ± 3 days after insemination using an ultrasound "Sonoscape-5 V." Data were analysed using correlation analysis and ROC curves. Plasma P4 concentration showed positive correlation with CL_d (r = .68, p < .01), CL_area (r = .45, p < .01), CL_volume (r = .41, p < .01), and CL_pixels (r = .67, p < .01). The ROC curve indicated that P4 concentrations and CL parameters, especially the CL_pixels, were the best predictors of the pregnancy, among the others that were able to detect pregnancy at the time of PG with the best P4 and CL_pixels cut-off value (4.1 ng/mL and 43.18) and AUC was (0.95 and 0.89); resp. (p < .001). Regarding the other parameters, it was possible to set AUC 0.79, 0.79, and 0.68 for CL_d, area, and volume with a sensitivity of 66.7%, 70.8%, and 66.7% and a specificity of 88.2%, 82.4%, and 70.4% (p < .01), respectively. The AUC for both the follicular diameter and F_area was (0.56) with a sensitivity of 58.33% and 70.8% and a specificity of 62.5% and 50% (p > .05), respectively. In conclusion, CL measurements and progesterone concentrations had the greatest pregnancy prediction in Holstein dairy cows.

Quantitative analyses of insulin-like peptide 3 and sex steroid hormones in dominant follicles and corpora lutea during the estrus cycle and in follicular cysts in beef heifers.

Insulin-like peptide 3 (INSL3) and sex steroids were measured in bovine dominant follicles and corpora lutea during the estrus cycle and in follicular cysts. Paired ovaries from beef heifers (n = 47) were classified, by their morphological features, either into four stages of the estrus cycle (Day 1 = day of ovulation, Day 20 = day of estrus) as Stage I (Days 1-4; n = 8), Stage II (Days 5-10; n = 10), Stage III (Days 11-17; n = 8), and Stage IV (Days 18-20; n = 11) or follicular cystic (n = 10). Cysts (n = 15) were subdivided into estrogen-active (n = 7) and estrogen-inactive (n = 8) cysts. INSL3, testosterone, and estradiol-17ß concentrations in the dominant follicular fluid of Stage IV were higher than those in Stages II and III (P < 0.05). INSL3 concentrations in the cystic fluid were similar to those in dominant follicles at Stage IV, whereas testosterone and estradiol-17ß concentrations were lower in cysts (P < 0.05). INSL3 content per estrogen-inactive cyst was higher than that of Stage IV (P < 0.05). INSL3 and progesterone concentrations in luteal tissue and contents per corpus luteum were higher in Stages II and III (P < 0.05). In conclusion, INSL3 secretion in bovine dominant follicles increased with maturation. Follicular cysts may retain the production of INSL3 during their formation but tend to lose the capacity for testosterone secretion. Estrogen-inactive cysts subjected to advanced atresia may accumulate more INSL3. INSL3 production in bovine corpora lutea is enhanced during maturation.

Effect of elevating luteinizing hormone action using low doses of human chorionic gonadotropin on double ovulation, follicle dynamics, and circulating follicle-stimulating hormone in lactating dairy cows.

Double ovulation and twin pregnancy are undesirable traits in dairy cattle. Based on previous physiological observations, we tested the hypothesis that increased LH action [low-dose human chorionic gonadotropin (hCG)] before the expected time of diameter deviation would change circulating FSH concentrations, maximum size of the second largest (F2) and third largest (F3) follicles, and frequency of multiple ovulations in lactating dairy cows with minimal progesterone (P4) concentrations. In replicate 1, multiparous, nonbred lactating Holstein dairy cows (n = 18) had ovulation synchronized. On d 5 after ovulation, all cows had their corpus luteum regressed and were submitted to follicle (≥3 mm) aspiration 24 h later to induce emergence of a new follicular wave. Cows were then randomized to NoP4 (untreated) and NoP4+hCG (100 IU of hCG every 24 h for 4 d after follicle aspiration). Ultrasound evaluations and blood sample collections were performed every 12 h for 7 d after follicle aspiration. All cows were then treated with 200 µg of GnRH to induce ovulation. In replicate 2, cows (n = 16) were resubmitted to similar procedures (i.e., corpus luteum regression, follicle aspiration, randomization, ultrasound evaluations every 12 h, GnRH 7 d after aspiration). However, cows in replicate 2 received an intravaginal P4 device that had been previously used (∼18 d). Only cows with single (n = 15) and double (n = 16) ovulations were used in the analysis. No significant differences were detected for frequency of double ovulation, follicle sizes, and FSH concentrations across replicates (NoP4 vs. LowP4 and NoP4+hCG vs. LowP4+hCG), so data were combined. Double ovulation was 40% for control cows with no hCG (CONT) and 62.5% with hCG (hCG). Double ovulation increased as the maximum size of F2 increased: <9.5 mm and 9.5-11.5 mm (7.7%) and ≥11.5 mm (94.1%). The hCG group had more cows with F2 > 11.5 (69%) than with 9.5 ≥ F2 ≤ 11.5 (25%) and F2 < 9.5 (6%). In agreement, F2 and F3 maximum size were larger in the hCG group, but FSH concentrations were lower after F1 > 8.5 mm compared with CONT. In contrast, FSH concentrations were greater before deviation (F1 closest value to 8.5 mm) in cows with double ovulations than in those with single ovulations, regardless of hCG treatment. In addition, time from aspiration to deviation was shorter in cows with double rather than single ovulation and in cows treated with hCG as a result of faster F1, F2, and F3 growth rates before diameter deviation. In conclusion, greater FSH and follicle growth before deviation seems to be a primary driver of greater frequency of double ovulation in lactating cows with low circulating P4. Moreover, the increase in follicle growth before deviation and in the maximum size of F2 during hCG treatment suggests that increased LH may also have a role in stimulating double ovulation.

Follicular dynamics during the pre-ovulatory and subsequent first follicular wave stages affect the pregnancy outcome in Japanese Black cows.

The diameters of the pre-ovulatory follicles (PF) and the largest follicle during the subsequent first follicular wave (W1LF), and plasma estradiol-17ß (E2) concentrations were monitored on Days 0, 1, 3, 5, and 7 (ovulation = Day 1). Pregnancy was diagnosed on Day 30. Cows were classified into two groups according to the location of the dominant follicle ipsilateral (IG) or contralateral (CG) to the corpus luteum on Day 7. From Days 3 to 7, some follicles that had been determined as the subordinate in the previous examination exceeded the W1LF located in the opposite ovary in terms of the diameter. These were defined as switching (SW), whereas others were defined as non-switching (NSW). The diameter of PF was significantly smaller in pregnant (P) animals than in non-pregnant (NP) animals. The plasma E2 concentration on Day 0 was significantly higher in P animals than in NP animals and tended to be higher in NSW than in SW. In addition, plasma E2 concentrations around Days 3 to 7 tended to be higher in P animals of NSW than in NP animals of SW. The conception rates did not differ between IG and CG but were significantly higher in NSW than in SW. In the IG group, the conception rate tended to be higher in NSW than in SW.

Influence of ipsilateral coexistence of the first wave dominant follicle and corpus luteum on ovarian dynamics and plasma sex steroid hormone concentrations in lactating dairy cows treated with human chorionic gonadotropin.

We examined the effect of human chorionic gonadotropin (hCG) treatment 5 days after estrus on ovarian dynamics and plasma progesterone (P4) and estradiol (E2) concentrations when the first-wave dominant follicle (DF) was ipsilateral or contralateral to the corpus luteum (CL) in lactating dairy cows. Seventy cows were divided into two groups: (1) ipsilateral group (IG; n = 37), in which the first-wave DF was ipsilateral to the CL, and (2) contralateral group (CG; n = 33), in which the first-wave DF was contralateral to the CL. IG and CG were further subdivided into two groups: non-treatment group (IG, n = 18; CG, n = 19), and hCG treatment group: administrated 1500 IU of hCG 5 days after estrus (IG, n = 19; CG, n = 14). Blood sampling and ovarian examination were performed at 3, 5, 7, 9, 11, and 13 days after estrus. Mean diameter of the first-wave DF on Day 9 tended (P = 0.067) to be larger in IG than in CG in the non-treatment group. Mean diameter of CL and plasma P4 and E2 concentrations did not differ between IG and CG in the non-treatment and hCG treatment groups. Accessory CL development did not differ between IG and CG in the hCG treatment group. Our findings indicate that CL development and plasma P4 and E2 concentrations were not affected by the existence of the first-wave DF; however, first-wave DF development was affected by the existence of a CL in the same ovary.

Physiological characteristics and effects on fertility of the first follicular wave dominant follicle in cattle.

The first follicular wave emerges soon after ovulation, and its dominant follicle (DF) develops during the first 8-10 days of the estrous cycle in cattle. And, the first-wave DF is a non-ovulatory follicle, because it develops during the first half of the estrous cycle simultaneously with the corpus luteum (CL), which produces and secretes progesterone. Regarding the characteristics of development and the mechanisms of deviation in the DF during the follicular wave, the first-wave DF has been well studied. However, the characteristics of the first-wave DF, such as growth, blood flow in the follicular wall, concentration of sex steroid hormones in the peripheral blood and follicular fluid, amounts of mRNA in granulosa cells, as well as the characteristics of the CL formed after the first-wave DF and the influence of the first-wave DF on fertility (conception rate), have not been well studied. Additionally, the first-wave DF synthesizes and secretes 17ß-estradiol (E2), and plasma E2 concentration increases during the early stage of the estrous cycle. Consequently, there is a possibility that the first-wave DF might affect the fertility in cattle. In this review, to provide the new perspective on reproductive physiology in cattle, characteristics of the first-wave DF were examined in detail and its characteristics were compared with that of the second-wave DF. In addition, the locational effects of the first-wave DF and CL on conception rate are discussed.

Effects of human chorionic gonadotropin treatment after artificial inseminations on conception rate with the first follicular wave dominant follicle in the ovary ipsilateral to the corpus luteum in lactating dairy cows.

We examined the effect of human chorionic gonadotropin (hCG) treatment 5 days after artificial insemination (AI) on conception rate when the first-wave dominant follicle (DF) in the ovaries was either ipsilateral or contralateral to the corpus luteum (CL) in lactating dairy cows. 577 cows from 4 dairy farms were divided into the following two groups 5 days after AI using transrectal ultrasonography: (1) the ipsilateral group (IG; n = 348), in which the DF was ipsilateral to the CL, and (2) the contralateral group (CG; n = 229), in which the DF was contralateral to the CL. IG and CG were further subdivided into two groups: non-treatment groups, which received no treatment (IG, n = 220; CG, n = 128), and hCG treatment group, that was administrated 1500 IU hCG 5 days after AI (IG, n = 143; CG, n = 86). Pregnancy was diagnosed by rectal palpation or transrectal ultrasonography from 53 to 67 days after AI. Conception rate was significantly (P < 0.01) higher in the hCG treatment group of IG (40.6%) than in the non-treatment group of IG (21.4%); however, there was no difference in the non-treatment (51.7%) and hCG treatment (43.0%) groups of CG. Parity, farm, days in milk at AI, interaction between the farm and hCG treatment and interaction between the farm and location of the first-wave DF and CL did not affect conception rate. Our results suggest that conception rate can be improved by administrating hCG only to cows with the first wave DF ipsilateral to the CL.

Puncture and drainage of the subordinate follicles at timed artificial insemination prevents the risk of twin pregnancy in dairy cows.

The objective of this study was to determine whether fluid drainage from the subordinate follicles by ovum pickup procedures prevents the risk of twin pregnancy without reducing the fertility of the cow. Lactating dairy cows with at least two follicles over 12 mm diameter located one on each ovary and selected from synchronized groups for fixed-time insemination were assigned to a Control (n = 49) or Drainage (n = 49) group. The largest follicle was considered as the dominant follicle. Draining of all subordinate follicles (≥10 mm) was performed in the Drainage group. All drained follicles developed as a corpus luteum 7 days later. In the Control cows, the presence of two corpora lutea (55.1%) was lower (p = .003) than those in the Drainage cows (87.8%), whereas the incidence of twin pregnancies was 50% and 0% for the Control and Drainage groups, respectively (p < .001). Draining did not affect the pregnancy rate. These results indicate that puncture and drainage of the subordinate follicles at insemination may eliminate the risk of twin pregnancies and reduce the risk of subsequent pregnancy loss by increasing the incidence of additional corpora lutea.

Effects of dietary tryptophan levels on performance and biochemical variables of plasma and intestinal mucosa in yellow-feathered broiler breeders.

The effects of dietary tryptophan (Trp) levels on performance and biochemical variables of plasma and intestinal mucosa in broiler breeder hens were investigated in this study. A total of 780 Lingnan yellow-feathered broiler breeder hens were randomly assigned in one of five dietary treatments with six replicates per treatment (26 birds per replicate). The breeder hens were fed either the basal diet (0.11% Trp) or the basal diet supplemented to 0.15%, 0.19%, 0.23% and 0.27% Trp, from 197 to 259 days of age. Graded levels of Trp from 0.11% to 0.27% in the diet produced quadratic (p < .05) responses in laying rate, average daily egg production, and feed conversion ratio, and quadratic (p < .01) responses in total large follicle weight and average large follicle weight. An increase in fertilization rate of total eggs was observed in breeders fed 0.27% Trp, and hatchability was higher in breeders fed 0.23% and 0.27% Trp than with 0.19% Trp (p < .05). The content of uric acid N decreased with 0.15% and 0.23% dietary Trp (p < .05). The content of GSH and the GSH-to-GSSG ratio in plasma were reduced by 0.15%, 0.19% and 0.27% Trp diets (p < .05). A higher activity of GST in plasma was observed with 0.15% Trp in relation to 0.23% and 0.27% Trp (p < .05). The activity of Na+ -K+ -ATPase of plasma in birds fed 0.27% Trp was lower than in those fed 0.15% Trp and the control birds (p < .05). There were significant influences of dietary Trp levels on S6K1, B0 AT1, Nrf2, TLR4, TNF-α and IL-6 transcripts of ileal mucosa (p < .05). The optimal dietary Trp level was 0.203% or 254 mg per hen per day, for Chinese yellow-feathered broiler breeder hens aged from 197 to 259 days.

Salivary miR-16, miR-191 and miR-223: intuitive indicators of dominant ovarian follicles in buffaloes.

Estrus or sexual receptivity determination is utmost important for efficient breeding programs for female buffaloes. Prominent estrus behavioral symptoms are the result of several molecular and neuroendocrine events involving the ovary and the brain. Expression of estrus behavior is poor in buffaloes during the summer season. Hence, the discovery of biomarkers specific to the estrus stage or its related ovarian events, like the presence of dominant ovarian follicle, is helpful for developing an easy estrus determination method. MicroRNA are small non-coding RNA with a potential to be biomarkers. Therefore, the present study targeted to investigate the potential of estrogen responsive miRNAs (miR-24, miR-200c, miR-16, miR-191, miR-223 and miR-203) as estrus biomarkers in buffalo saliva, a non-invasive fluid representing animals' pathophysiology. There was a significant (P < 0.05) increase in the salivary presence of the miR-16, miR-191 and miR-223 at 6th and 18th-19th days than the 0 day (estrus), 10th day and the following consecutive estrus day. These observations may indicate an association between the representative lower presence of these miRNA in saliva and the presence of dominant ovarian follicles. To test this association, pathway analysis, target gene identification, functional annotation and protein-protein interaction networks (PPI) were performed for miR-16, miR-191 and miR-223 by different bioinformatics tools. Interestingly, the top pathways (fatty acid biosynthesis and oocyte meiosis), target genes (FGF, BDNF and IGF1) and PPI hub genes (KRAS, BCL2 and IGF1) of these miRNAs were found essential for ovarian follicular dominance. In conclusion, the miR-16, miR-191 and miR-223 may not be the perfect estrus stage-specific biomarkers. However, their lower presence in saliva at estrus and 9th-10th day of estrous cycles, when the ovary usually has a dominant follicle in buffaloes, may intuitively indicate the follicular dominance. Further studies are needed to prove this association in a large population.

Limited ability of circulating anti-Müllerian hormone to predict dominant follicular recruitment in PCOS women treated with clomiphene citrate: a comparison of two different assays.

The present retrospective cohort study was conducted to investigate whether serum anti-Müllerian hormone (AMH) levels, determined by either the Immunotech (IOT) or the second generation (Gen II) assay, can predict follicular recruitment in women with polycystic ovary syndrome (PCOS) undergoing ovulation induction with clomiphene citrate (CC). Patients received 50 mg CC daily for ovulation induction followed by natural intercourse or intrauterine insemination. Overall, 84 women had their serum AMH levels tested before treatment [42 patients with Immunotech (IOT), and 42 patients with the Gen II assay]. The primary outcome was to determine dominant follicle (>10 mm) recruitment in relation to AMH levels. Thirty-three (79%) patients in the IOT and 34 (81%) patients in the Gen II assay group developed a dominant follicle within 15 days after initiation of CC. Circulating AMH levels did not differ between women with or without dominant follicular recruitment in the both groups. By using either the AMH IOT or the Gen II assay, serum AMH levels were not predictive of the development of a dominant follicle. In conclusion, serum AMH levels measured by IOT or Gen II assay, has limited value to predict PCOS patients who will develop a dominant follicle following ovulation induction with CC.

Short communication: Development of the first follicular wave dominant follicle on the ovary ipsilateral to the corpus luteum is associated with decreased conception rate in dairy cattle.

In this study, we examined the effect of the locations of the first-wave dominant follicle (DF) and corpus luteum (CL) on fertility. In total, 350 artificial insemination (AI) procedures were conducted (lactating dairy cows: n=238, dairy heifers: n=112). Ovulation was confirmed 24 h after AI. The locations of the first-wave DF and CL were examined 5 to 9d after AI using rectal palpation or transrectal ultrasonography. Lactating dairy cows and dairy heifers were divided into 2 groups: (1) the ipsilateral group (IG), in which the DF was ipsilateral to the CL; and (2) the contralateral group (CG), in which the DF was contralateral to the CL. Pregnancy was diagnosed using transrectal ultrasonography 40d after AI. Conception rates were 54.0% in all cattle: 48.9% in lactating dairy cows, and 58.9% in dairy heifers. The incidence of the first-wave DF location did not differ between IG and CG (all cattle: 184 vs. 166; lactating cows: 129 vs. 109; heifers: 55 vs. 57 for IG vs. CG). Conception rates were lower in IG than in CG (all cattle: 40.2 vs. 69.3%; lactating dairy cows: 38.0 vs. 67.0%; dairy heifers: 45.5 vs. 73.7%, for IG vs. CG). Conception rate was not affected by season or live weight in heifers and lactating cows. In addition, days in milk at AI, milk production, body condition score, and parity did not affect conception in lactating cows. In summary, development of the first-wave DF in the ovary ipsilateral to the CL was associated with reduced conception rates in both lactating cows and heifers.

Transcriptome profiling of granulosa and theca cells during dominant follicle development in the horse.

Several aspects of equine ovarian physiology are unique among domestic species. Moreover, follicular growth patterns are very similar between horses and humans. This study aimed to characterize, for the first time, global gene expression profiles associated with growth and preovulatory (PO) maturation of equine dominant follicles. Granulosa cells (GCs) and theca interna cells (TCs) were harvested from follicles (n = 5) at different stages of an ovulatory wave in mares corresponding to early dominance (ED; diameter ≥22 mm), late dominance (LD; ≥33 mm) and PO stage (34 h after administration of crude equine gonadotropins at LD stage), and separately analyzed on a horse gene expression microarray, followed by validation using quantitative PCR and immunoblotting/immunohistochemistry. Numbers of differentially expressed transcripts (DETs; ≥2-fold; P < 0.05) during the ED-LD and LD-PO transitions were 546 and 2419 in GCs and 5 and 582 in TCs. The most prominent change in GCs was the down-regulation of transcripts associated with cell division during both ED-LD and LD-PO. In addition, DET sets during LD-PO in GCs were enriched for genes involved in cell communication/adhesion, antioxidation/detoxification, immunity/inflammation, and cholesterol biosynthesis. In contrast, the largest change in TCs during the LD-PO transition was an up-regulation of genes involved in immune activation, with other DET sets mapping to GPCR/cAMP signaling, lipid/amino acid metabolism, and cell proliferation/survival and differentiation. In conclusion, distinct expression profiles were identified between growing and PO follicles and, particularly, between GCs and TCs within each stage. Several DETs were identified that have not been associated with follicle development in other species.

Impact of 17ß-estradiol administration at the moment of timed-AI in Nelore cows with small dominant follicle or not showing estrus.

We aimed to evaluate the effects of administering estradiol (E-17ß) at the moment of timed-AI (TAI) on uterine gene expression, estrous expression rate (EER), and pregnancy rate (P/TAI) in Nelore cows with a small dominant follicle (DF) or not showing estrus at TAI. In Experiments 1 and 2 (Exp1, Exp2) cows were submitted to a P4/E-17ß-based protocol (day 0) for synchronization of ovulation. On day 7, devices were removed, cows received 1 mg E-17ß cypionate and 12.5 mg dinoprost. On day 9, cows with DF < 11.5 mm in diameter were split into different groups. In Exp1 (n = 16/group): Control (no treatment), E-2 (2 mg E-17ß) and E-4 (4 mg E-17ß). In Exp2: Control (n = 12); E-2 (n = 14); GnRH (0.1 mg gonadorelin acetate, n = 13); and E-2+GnRH (association of GnRH and E-17ß, n = 13). Between days 9 and 11, endometrial thickness (ET), time of ovulation detection, and EER were recorded. In Exp1, a uterine cytological sample was collected 4 h after treatment to evaluate the transcript expression of receptors for E-17ß (ESR1 and ESR2), oxytocin (OXTR), and P4 (PGR). In Experiment 3 (Exp3), 3829 suckled cows were submitted to a P4/E-17ß-based protocol for TAI. On day 9, devices were removed and cows received 1 mg E-17ß cypionate and 0.4 mg sodium cloprostenol. On day 11, TAI was performed and cows that did not demonstrate estrus received 0.1 mg gonadorelin acetate, and were allocated into two groups: GnRH (n = 368) and E-2+GnRH (2 mg E-17ß; n = 363). In Exp1, plasma E-17ß concentrations increased at 4 h after treatment in a dose-dependent manner but reduced at 12 h. The E-17ß-treated cows had greater transcript abundance for OXTR and lesser for ESR1 and ESR2, and the ET was reduced 12 h after treatment (P < 0.05). No significant difference (P > 0.1) was observed between the E-17ß doses in estrus or ovulation rate. In Exp2, the interval from treatment to ovulation was longer (P < 0.05) in the E-17ß group. GnRH-treated cows showed higher ovulation rates (89 vs. 35 %) compared to cows not treated with GnRH, as E-17ß-treated cows (P < 0.01) had a lower ovulation rate compared to those not receiving E-17ß (44 vs. 78 %). In Exp3, P/TAI was 55 % for cows in estrus. For those not showing estrus, no difference (P > 0.1) in P/TAI was observed between GnRH (34 %) and E-2+GnRH (31 %) groups. Cows with a DF ≥ 11 mm (n = 192) had a greater (P < 0.05) P/TAI (49 %) than those with DF < 11 mm (n = 377; 29 %). In conclusion, E-17ß administration in the moment of TAI modulates the mRNA expression of uterine receptors in cows with a small DF but does not impact the P/TAI compared with GnRH treatment in suckled Nelore not showing estrus previous to TAI.

Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing.

No studies have evaluated the peripartum follicular dynamics resulting in foal heat under tropical environments. We aimed to assess retrospectively the peripartum follicular dynamics in Colombian Paso Fino mares that were inseminated at the foal heat, becoming pregnant or not. Records including follicular dynamics of pregnant mares prepartum and from foaling until foal heat ovulation were assessed in Colombian Paso Fino mares (CPF, n = 24) bred under permanent grazing in a tropical herd in Colombia. The number of ovarian follicles >10 mm before foaling and the largest follicle (F1) growth rate (mm/day) from foaling until the F1 reached the largest diameter (pre-ovulatory size) at the foal heat were assessed. Mares were inseminated at foal heat with 20 mL of semen (at least 500 million live spermatozoa) with >75% motility and 80% viability from a stallion of proven fertility. Ovulation was confirmed the day after follicles had reached the largest diameter. Quantitative data from follicular growth, the day at ovulation, from mares that became pregnant (PM) or not (NPM) at 16 days post-insemination were compared by one-way ANOVA, repeated measures ANOVA (follicle growth rate data) or Chi-square test (edema and cytology scores data). Epidemiological data, gestation length, and the number of follicles on third prepartum days did not significantly differ between PM and NPM (p > 0.05). Seventy-one percent of mares (17/24) got pregnant. Ovulatory follicles grew faster in the NPM group (n = 7), which ovulated between the seventh and ninth postpartum days, compared to PM (n = 17), which ovulated between the 11th and 13th postpartum days. Pre-ovulatory follicle diameter in PM (48.57 ± 0.8 mm) was significantly larger than in NPM (42.99 ± 1.0 mm) (p < 0.05). In addition, the PM edema score (2.93 ± 0.32 mm) on ovulation day was significantly lower (p < 0.05) than NPM (4.47 ± 0.05 mm). First postpartum ovulation occurred at 12.6 ± 0.3 and 8.5 ± 0.4 days (p < 0.05) in PM and NPM, respectively. Colombian Paso Fino mares bred under permanent grazing under tropical rainforest conditions with no foaling or postpartum complications showed a 71% gestation rate when inseminated at foal heat when ovulation occurs between the second and third postpartum week.

Follicle Selection in Mares as a Model for Illustrating the Many Hormonal and Biochemical Interactions That Drive a Single Physiological Mechanism.

The mechanism for selection of the future dominant or ovulatory follicle in mares involves a relatively abrupt separation in growth rates between the future dominant follicle and several subordinate follicles and is termed diameter deviation. The event is used to illustrate that a coordinated complex of many follicular, hormonal, and biochemical factors interact and interbalance during a single physiological mechanism. For example, a positive effect of follicle stimulating hormone (FSH) on development of all follicles during the growing phase can later involve a positive effect of luteinizing hormone (LH) but apparently only on the future dominant follicle. In turn, the developing and future dominant follicle produces estradiol which at appropriate times and degrees reduces FSH concentrations to accommodate follicle functions at certain levels of FSH. Meanwhile, the estradiol prevents LH from increasing from a useful to an adverse concentration. These interactions enmesh with the production and roles of other factors (e.g., inhibin, insulin-like growth factor) during follicle selection. The wide array of morphological, hormonal, and biochemical activities occur in harmony even when in the same tissue and often at the same time.

Oocyte developmental capacity is influenced by intrinsic ovarian factors in a bovine model for individual embryo production.

The ovary and its hormones may have major effects on the in vitro developmental capacity of the oocytes it contains. We related intrinsic ovarian factors namely the presence of corpus luteum (CL) and/or dominant follicle (>8 mm) and the follicular count to cumulus expansion (CE), embryo development, and blastocyst quality in a bovine model. Cumulus-oocyte-complexes (COCs) were aspirated from follicles between 4 and 8 mm in diameter. In vitro embryo production was performed in a fully individual production system. The follicular fluid from which COCs were collected was pooled (per ovary) to evaluate the estrogen, progesterone, and insulin-like growth factor-1 (IGF-1) concentrations. Cumulus oocyte complexes collected from ovaries without a CL presented a greater CE than COCs derived from ovaries bearing CL. The absence of ovarian structures increased the blastocyst rate when compared to oocytes derived from ovaries with a CL, a dominant follicle, or both. Blastocysts derived from ovaries without a dominant follicle presented higher total cell numbers and a lower proportion of apoptosis than blastocysts derived from ovaries containing a dominant follicle. Cumulus oocyte complexes collected from ovaries with high follicular count resulted in higher cleavage than from ovaries with low follicular count, but the blastocyst rate was similar between groups. Ovaries bearing a CL had greater progesterone and IGF-1 follicular fluid concentrations in neighboring follicles than ovaries without a CL. Selection for bovine ovaries without CL or dominant follicle can have positive effects on CE, embryo development, and blastocyst quality in an individual embryo production system set-up.

The relationship between dominant follicle development and clinical outcomes of hormone replacement therapy-frozen embryo transfer: a retrospective clinical study.

Research question: Hormone replacement therapy (HRT) is one of the most used endometrial preparation protocols for frozen embryo transfer (FET) due to the convenience of its administration and stability of pregnancy outcomes. There are several HRT cycles accompanied by the development of dominant follicles. However, the relationship between dominant follicle development and clinical outcomes in HRT-FET cycles remains unclear. Design: We carried out a retrospective cohort study of 13251 cycles at our reproductive medicine center from 2012 to 2019. Total cycles were divided into two groups according to whether there was dominant follicular development. In addition, we conducted a secondary analysis that used propensity-score matching to reduce confounding variables. A univariate and multivariable logistic regression model was further employed to analyze the effect of dominant follicle development in HRT cycles on clinical pregnancy outcomes. Results: There was no significant correlation between dominant follicle development in HRT-FET cycles and the clinical pregnancy rate (adjusted OR = 1.162, 95% CI: 0.737-1.832, P = 0.52). In addition, there was a positive correlation between the basic follicle-stimulating hormone (FSH) level and the development of dominant follicles, while there was a negative correlation between antral follicle count (AFC), menstrual cycle length and the development of dominant follicles in HRT cycles. Conclusions: The development of dominant follicles in HRT-FET cycles does not affect the clinical pregnancy rate, early miscarriage rate and live birth rate. Therefore, it is not necessary to immediately cancel the FET cycle immediately when dominant follicle development is monitored in the HRT-FET cycle.

Probability of Pregnancy With Mono vs Multiple Folliculogenesis in Women With Unexplained Infertility.

Context: Ovarian stimulation (OS) increases pregnancy rates but can cause multiple folliculogenesis and multiple pregnancy. Objective: To determine whether the probability of pregnancy differs in OS cycles with mono- vs multifolliculogenesis in women with unexplained infertility (UI). Design: Secondary analysis of a multicenter, randomized controlled trial: Assessment of Multiple Intrauterine Gestations from Ovarian Stimulation with 3 treatment arms: gonadotropins, clomiphene, or letrozole, combined with intrauterine insemination. Women were categorized as having either 1 or ≥ 2 mature follicles (≥ 16 mm). Relative risk (RR) and 95% CIs for clinical pregnancy and live birth by number of follicles were estimated using generalized linear models adjusted for age, body mass index, years of infertility, and history of prior live birth. Setting: 12 US-based clinical sites. Participants: Normally cycling women aged 18 to 40 years with a normal uterine cavity and at least 1 patent fallopian tube. Male partners with ≥ 5 million total motile sperm. Interventions: Gonadotropins, clomiphene, or letrozole with insemination. Main Outcome Measures: Clinical pregnancy rates (CPR) and live birth rates (LBR). Results: A single mature follicle > 16 mm resulted in lower CPR (RR, 0.70; 95% CI, 0.54-0.90) and LBR (RR, 0.67; 95% CI, 0.51-0.89) compared with ≥ 2 mature follicles. When stratified by treatment modality, no association of follicle number with CPR or LBR was observed for letrozole or clomiphene, but women using gonadotropins had lower CPR and LBR with monofolliculogenesis. Conclusion: In couples undergoing gonadotropin treatment for UI, monofolliculogenesis following OS is related to a lower rate of live birth.