Relationships of hormonal patterns and fertility to occurrence of two or three waves of ovarian follicles, before and after breeding, in beef cows and heifers

The fertility of dairy heifers and cows is not influenced by the follicular wave of the ovulatory follicle

Two studies were conducted to evaluate the effects of the follicular wave on ovarian function and fertility in dairy heifers and lactating cows. In study 1, the estrous cycle of the selected Holstein heifers was initially synchronized using two intra-muscular prostaglandin F2α (PGF2α) administrations 11 days apart. Heifers in group FFW (n = 14) received an intra-muscular 500 μg PGF2α administration on day 7 after detecting standing estrus, while Heifers in group SFW (n = 14) were administered PGF2α 13 days after detecting standing estrus. The pregnancy rates of FFW (n = 98) and SFW (n = 100) heifers were also determined 35-37 days after artificial insemination (AI). In Study 2, healthy Holstein lactating cows (n = 28) were randomly assigned to either the FFW (n = 14) or SFW (n = 14) groups. The estrous cycles of the cows were presynchronized using two intra-muscular administrations of PGF2α given 14 days apart. Then, the emergences of the follicular waves were induced using an Ovsynch protocol. The pregnancy rate of FFW (n = 99) versus SFW (n = 98) cows was also determined 35-37 days after AI. The ovulatory follicle and corpus luteum (CL) resulting from the ovulatory follicle of FFW were larger than those of the dominant follicle and the CL of SFW in dairy heifers and lactating cows. However, the pregnancy rate did not differ between the FFW and SFW groups in heifers and lactating cows 35-37 days after AI. In conclusion, although the characteristics of the ovulatory follicles in FFW versus SFW animals differed, the follicular wave in dairy heifers or lactating cows did not affect fertility.

Impact of a hypocaloric dietary intervention on antral follicle dynamics in eumenorrheic women with obesity

STUDY QUESTION

Do antral follicle dynamics change in women with obesity and regular ovulatory cycles after a 6-month hypocaloric dietary intervention?

SUMMARY ANSWER

After a 6-month hypocaloric dietary intervention, women with obesity and regular ovulatory cycles displayed evidence of improved antral follicle dynamics defined by the emergence of more dominant follicles, larger ovulatory follicle diameter at selection, and increased luteal progesterone concentrations compared to pre-intervention.

WHAT IS KNOWN ALREADY

Precise events in antral folliculogenesis must occur in order for natural and regular monthly ovulation. In healthy women of reproductive age, antral follicles are recruited for growth in a wave-like fashion, wherein a subset of follicles are selected for preferential growth, and typically, one dominant follicle culminates in ovulation. Women with obesity and regular ovulatory cycles display evidence of suppressed antral follicle development, as evidenced by fewer recruitment events, fewer selectable and dominant follicles, smaller diameter of the ovulatory follicle at selection, and a higher prevalence of luteal phase defects. While improvements in gonadotropin and ovarian steroid hormone concentrations after weight loss have been documented in eumenorrheic women with obesity, the precise impact of weight loss on antral follicle dynamics has not been evaluated.

STUDY DESIGN, SIZE, DURATION

A pre-post pilot study of 12 women who participated in a 6-month hypocaloric dietary intervention.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Twelve women with obesity (total body fat ≥35%) underwent transvaginal ultrasonography and venipuncture every-other-day for one inter-ovulatory interval (IOI) both before (baseline) and during the final month (Month 7) of a six-month hypocaloric dietary intervention. Participants were aged 24-34 years and had a self-reported history of regular menstrual cycles (25-35 days). Follicle number and diameter (≥2 mm) were quantified at each study visit, and individual growth profiles for all follicles ≥7 mm were determined. Blood samples were assayed for reproductive hormones. Follicle dynamics and reproductive hormone concentrations were compared pre- and post-intervention. Further, post-intervention follicle and endocrine dynamics (Month 7 IOI) were compared to an age-matched reference cohort of lean women with regular ovulatory cycles (total body fat <35%, N = 21).

MAIN RESULTS AND THE ROLE OF CHANCE

Participants lost an average of 11% of their original body weight with the hypocaloric dietary intervention. More dominant follicles were detected (≥10 mm) at Month 7 compared to baseline (0. 3 ± 0.4 versus 0.4 ± 0.5 follicles, P = 0.001), and ovulatory follicles were selected at larger diameters post-intervention (7.3 ± 2.0 versus 10.9 ± 2.6 mm, P = 0.007). Luteal progesterone concentrations were increased at Month 7 compared to baseline (5.3 ± 3.65 versus 6.3 ± 4.74 ng/ml, P < 0.0001). However, risk for luteal phase dysfunction as judged by the prevalence of a luteal phase length <10 days, integrated luteal progesterone levels <80 ng/ml or peak progesterone <10 ng/ml did not differ pre- versus post-intervention (all, P > 0.05). In Month 7, follicle dynamics and endocrine profiles were similar to the reference cohort across all measures.

LIMITATIONS, REASONS FOR CAUTION

This study does not inform on the earliest stages of ovarian follicle development and is limited to providing knowledge on the later stages of antral follicle development. This study cannot fully address causation between weight loss and sustained improvements in antral follicle dynamics. The data cannot be extrapolated to comment on potential improvements in fertility and fecundity with weight loss. The small group sizes limit statistical power.

WIDER IMPLICATIONS OF THE FINDINGS

The increasing prevalence of obesity necessitates an understanding of the mechanisms that underlie potential improvements in reproductive health outcomes with weight loss. Women with obesity and regular ovulatory cycles who undertook a 6-month hypocaloric dietary intervention demonstrated improvements consistent with benefits of lifestyle intervention on reproductive health even in those without overt signs of reproductive dysfunction. Potential improvements in the cellular makeup of follicles, which may underlie the restoration of normal follicle development and amelioration of subfertility, require further investigation.

STUDY FUNDING/COMPETING INTEREST(S)

Cornell University, President's Council of Cornell Women, United States Department of Agriculture (Grant No. 8106), and National Institutes of Health (R01-HD0937848). B.Y.J. and H.V.B. were supported by doctoral training awards from the National Institutes of Health (T32-DK007158) and Canadian Institutes of Health Research (Grant No. 146182), respectively. The authors have no competing interests.

TRIAL REGISTRATION NUMBER

NCT01927432 and NCT01785719.

Obesity is associated with alterations in antral follicle dynamics in eumenorrheic women

STUDY QUESTION

Are ovarian antral follicle dynamics altered in women with obesity and regular ovulatory cycles?

SUMMARY ANSWER

Eumenorrheic women with obesity display evidence of suppressed antral follicle dynamics as judged by fewer recruitment events, selectable follicles, and anovulatory dominant follicles, as well as lower anti-Müllerian hormone (AMH) concentrations and an increased prevalence of luteal phase defects.

WHAT IS KNOWN ALREADY

Ovarian antral follicle development is a dynamic process involving distinct follicular and endocrine events that are critical for the occurrence of regular monthly ovulations. Follicle dynamics have not been prospectively evaluated in eumenorrheic women with obesity despite the known impact of obesity on gonadotropin production, ovarian steroid hormone concentrations, and fecundity.

STUDY DESIGN, SIZE, DURATION

This was a prospective, longitudinal study of 42 women conducted over one inter-ovulatory interval (IOI).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A group of 21 women with obesity (total percent body fat ≥35%) and a group of 21 women without obesity (total percent body fat <35%) underwent transvaginal ultrasonography and venipuncture every-other-day for one IOI at an academic clinical research unit. Participants were aged 19-38 years and had a history of self-reported regular menstrual cycles (21-35 days). Follicle number and diameter (≥2 mm) were quantified at each visit. Individual growth profiles for all follicles that grew to ≥7 mm were assessed. Blood samples were assayed for gonadotropins, AMH, estradiol, and progesterone.

MAIN RESULTS AND THE ROLE OF CHANCE

Women with obesity exhibited fewer recruitment events (mean ± SD, 1 ± 1 vs 2 ± 1 events; P = 0.010) and fewer selectable follicles (4 ± 3 vs 8 ± 6 follicles per participant; P = 0.022) during an IOI compared to women without obesity. AMH levels were lower in women with obesity (4.40 ± 3.01 vs 5.94 ± 2.49 ng/ml; P = 0.023), while gonadotropin profiles were similar between groups, across the IOI. Of the individual follicles tracked, fewer follicles progressed to >10 mm in the cohort with obesity (30 vs 40 follicles; P = 0.04) and fewer anovulatory follicles achieved dominance (9 vs 18 follicles; P = 0.041). Ovulatory follicles were selected at smaller diameters in women with compared to those without obesity (7.5 ± 1.6 vs 9.5 ± 1.9 mm; P = 0.001). Luteal phase defects were also more common in women with compared to those without obesity, as defined by either integrated (76 vs 29%, P = 0.002) or maximum (71 vs 24%, P = 0.002) luteal progesterone.

LIMITATIONS, REASONS FOR CAUTION

This study was limited to an assessment of antral follicle dynamics and cannot inform on earlier stages of folliculogenesis. This study was observational and cannot address causation between obesity and altered antral follicle dynamics. Lastly, the data cannot be extrapolated to account for reduced fecundity and fertility in obesity.

WIDER IMPLICATIONS OF THE FINDINGS

The increasing global prevalence of obesity necessitates an understanding of the mechanisms that underlie obesity-related adverse reproductive health outcomes. Eumenorrheic women with obesity demonstrate altered ovarian antral follicle and endocrine dynamics compared to their counterparts without obesity. The degree to which abnormal granulosa cell assembly and/or activity underlie the suboptimal luteinization and subfertility requires further investigation.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided by Cornell University, President's Council of Cornell Women, United States Department of Agriculture (grant no. 8106), and National Institutes of Health (R01-HD0937848). B.Y.J. and H.V.B. were supported by doctoral training awards from the National Institutes of Health (T32-DK007158) and Canadian Institutes of Health Research (grant no. 146182), respectively.

TRIAL REGISTRATION NUMBER

NCT01927432, NCT01785719.

Effect of ovarian follicular wave pattern and endocrine characteristics on pregnancy outcome in cows

The effect of two (2W) versus three (3W) wave patterns of follicular dynamics and concurrent endocrine milieu of follicle-stimulating hormone (FSH), luteinizing hormone (LH), oestradiol 17-β (E2) and progesterone (P4) were investigated during one interoestrous interval (IEI) before insemination, on ensuing pregnancy, in 70 lactating Jersey crossbred cows. The findings were evaluated for between [included all (overall) 2W-O and 3W-O cows] and within [after separating pregnant (P) and non-pregnant (NP) cows in 2W and 3W] wave patterns. The propensity of two (58.6%, n = 41) and three (41.4%, n = 29) wave patterns was similar (p = .15). The IEI, shorter by 2.6 days for 2W-O versus 3W-O (p < .0009), predicted wave pattern as 100% 2W-O cows had IEI of ≤21 days, present only in 27.6% 3W-O cows (p < .0001). The ovulatory follicle persisted for a significantly shorter duration for 3W-O versus 2W-O cows. The average FSH, LH, E2 and P4 concentrations during the IEI did not differ for between and within the wave patterns. Pregnancy rate (%) of 58.6 versus 41.4 (p = .15) for 2W-O versus 3W-O and 56.1-P versus 43.9-NP (p = .44) for within 2W was similar, but tended to differ for within the 3W pattern (69.0-P versus 31.0-NP, p = .06). The pregnancy outcome was influenced by the age of ovulatory follicle for between the wave patterns and by follicular count as well as FSH surge concentration for within the wave patterns. A shorter luteal phase reduced the pregnancy outcome, a novel finding of the present study.

Effect of progesterone administration during growing phase of first dominant follicle on follicular wave pattern in buffalo heifers

In buffaloes, like other domestic mammals, antral follicles develop in a wave-like pattern. Factors predictive of a particular follicular wave pattern are yet to be identified. In this study, we examined the preponderance of 2- versus 3-wave patterns in 46 interovulatory intervals (IOIs) from 36 buffalo heifers, in which a subset of 10 heifers was scanned for 2 consecutive IOIs to record the repeatability of follicular wave pattern. Two-wave pattern was detected in 63.0% and 3-wave follicular pattern in 27.0% IOIs. The dominant follicles (DF) of both wave 1 as well as the ovulatory wave attained a smaller (P < 0.05) maximum diameter in 3-wave cycle as compared to 2-wave cycle. The mean duration of IOI was significantly shorter in 2-wave compared to three-wave cycles (20.5 ± 0.3 vs. 22.3 ± 0.2 days; P < 0.05). Out of 10 buffalo heifers, 7 displayed non-alternating patterns and 3 had alternating follicular wave patterns. We also tested the hypothesis that progesterone administration during early IOI results in increased preponderance of 3-wave pattern and heifers inseminated after ovulation of the third wave DF will have greater fertility. Sixteen heifers subjected to progesterone treatment from D0 (day of ovulation) in a decreasing dose until D5 were compared with control heifers (n = 10). Progesterone treatment significantly reduced the maximum diameter of DF of wave 1 (P < 0.001), whereas the mean duration of IOI remained unchanged (P > 0.05) between the two groups. Progesterone administration during early IOI significantly increased the proportion of 3-wave cycles as compared to control (P < 0.05). The hypothesis that progesterone administration during IOI results in increased preponderance of 3-wave pattern was supported. However, no change in fertility was recorded in progesterone-treated heifers (7 pregnant out of 16; 43.8%) as compared to untreated control heifers (4 out of 10 heifers; 40.0%). In summary, progesterone administration in buffalo heifers during the growing phase of wave 1 resulted in greater preponderance of 3-wave follicular patterns, with no significant effect on fertility.

Supplementation with long-acting progesterone in early diestrus in beef cattle: II. Relationships between follicle growth dynamics and luteolysis

The aims were to characterize follicular dynamics in response to supplemental progesterone (P4) and to investigate the relationships between follicular growth and onset of luteolysis in P4-treated cows, submitted or not to artificial insemination (AI). Nonsuckled beef cows detected in estrus were assigned to receive AI or to remain non-AI. Three days after ovulation (ie, D3), AI cows were injected with 150 mg of long-acting P4 (AI + injectable P4 formulation [iP4]; n = 22), and the non-AI cows were assigned to receive 150 mg iP4 (n = 19) or saline (control, n = 19). Between D3 and D21, growth dynamics of the dominant follicles (DFs) was monitored by ultrasonography. Plasma P4 concentrations were measured every other day from D9 to D19. Pregnancy status (ie, P: pregnant and NP: nonpregnant) was examined by ultrasound on D28 to D32. Injectable P4 formulation supplementation decreased average maximum diameter of first-wave DF (DF1). Neither day of emergence of DF2 or DF3 nor the proportion of two- or three-wave cycles were altered by supplemental P4. Daily mean diameter of DF2 and DF3 was also similar between control and iP4 groups. Consistently, daily mean diameter of DF1 in iP4-treated cows was smaller for cows that underwent luteolysis by D15 compared to a later onset. Progesterone concentrations between D9 and D19 decreased earliest in the iP4 group, latest in the control group and was intermediate for the NP-AI + iP4 group. In addition, three-wave cycles presented a delayed decrease on plasma P4 concentrations than two-wave cycles. Further analysis revealed that on two-wave cycles, P4 concentrations on D15 were lowest in the iP4 and NP-AI + iP4 animals compared to the control and P-AI + iP4 groups. Conversely, for three-wave cycles, on D15, P-AI + iP4, NP-AI + iP4, and controls had greater P4 concentrations than the iP4 group. In summary, our data indicate that impairment of first follicular growth was associated with P4-induced shortened luteal lifespan (D14-D15) and that three-wave cycles after AI can be more supportive for pregnancy maintenance in P4-treated cows. We speculate that such conditions play a critical role in the embryonic ability to inhibit iP4-induced early luteolysis reported in part I of this series.

Transcriptome analysis of granulosa cells after conventional vs long FSH-induced superstimulation in cattle

BACKGROUND

Prolongation of superstimulatory treatment appears to be associated with a greater superovulatory response and with greater oocyte maturation in cattle. A genome-wide bovine oligo-microarray was used to compare the gene expression of granulosa cells collected from ovarian follicles after differing durations of the growing phase induced by exogenous FSH treatment. Cows were given a conventional (4-day) or long (7-day) superstimulatory treatment (25 mg FSH im at 12-h intervals; n = 6 per group), followed by prostaglandin treatment with last FSH and LH treatment 24 h later. Granulosa cells were harvested 24 h after LH treatment.

RESULTS

The expression of 416 genes was down-regulated and 615 genes was up-regulated in the long FSH group compared to the conventional FSH group. Quantification by RT-PCR of 7 genes (NTS, PTGS2, PTX3, RGS2, INHBA, CCND2 and LRP8) supported the microarrays data. Multigene bioinformatic analysis indicates that markers of fertility and follicle maturity were up-regulated in the long FSH group.

CONCLUSION

Using the large gene expression dataset generated by the genomic analysis and our previous associated with the growth phase and gene expression changes post LH, we can conclude that a prolonged FSH-induced growing phase is associated with transcriptomic characteristics of greater follicular maturity and may therefore be more appropriate for optimizing the superovulatory response and developmental competence of oocytes in cattle.

Some effects of post-oestrous hormonal therapies on conception rates and resubmission rates in lactating dairy cows

A range of hormonal therapies has been evaluated to potentially improve the reproductive performance of lactating dairy cows. Early lactation treatments with gonadotrophin releasing hormone (GnRH) or prostaglandin F2∝(PGF) may reduce the interval to first insemination or increase the conception rate to first insemination, but mainly in cows which have had a difficult pueperium or which are in herds with low conception rates. These two hormones, as well as progesterone and oestradiol benzoate (ODB) are commonly used either singly, or in combination (GnRH + PGF; progesterone + ODB + PGF) to synchronise the oestrus preceding first inseminations. None of these synchrony treatments is associated with increased conception rates. Extensive series of trials have been completed to identify post-oestrous or post-insemination hormonal therapies which could increase conception rates to the preceding insemination. The wide variation in results has precluded any being commonly regarded as sufficiently reliable for routine use. Nonetheless, meta-analyses have shown that GnRH treatment at insemination or in late dioestrus (11 to 13 day post-first insemination) can significantly increase “the risk of pregnancy”. Insemination treatments have been most effective with repeat breeders (+22.5%), whereas late dioestrous treatments (10%) may be dose and analogue specific (10 μg buserelin). Although metoestrous supplementation with progesterone can stimulate early embryonic development, the associated reduction in oestrous cycle length also reduces conception rates in heifers. Late dioestrous use of GnRH can prevent both of these negative effects. Early dioestrous supplementation with progesterone may enhance production of interferon tau, but this potentially beneficial effect has not been able to be reliably translated into increased conception rates. Many of these hormonal therapies are associated with altered patterns of ovarian follicle development which are similar to those in some synchrony treatments preceding first insemination. Recent studies have indicated that OBD and progesterone can be used to synchronise returns to service and increase the submission rate for second inseminations made about 3 weeks after first inseminations. This can make the non-return rate a more accurate measure of the response to a hormonal treatment and potentially overcome confusing impressions created when oestrous detection rates may be around 50%. Even if effective hormonal therapies are successfully developed, the results may be compromised by environmental factors such as heat stress, energy balance or energy partitioning for lactation. These factors may reduce oocyte quality, fertilization rates or normal uterine secretion patterns. Reduced conception rates associated with high daily milk yields in early lactation may not be able to be remedied simply with hormonal supplementation or by altering patterns of ovarian follicle development. Under these circumstances, controlling the inter-service interval could reduce the impact of the lowered conception rates.

miRNA-mRNA network involved in folliculogenesis interactome: systems biology approach

At later phases of folliculogenesis, the mammalian ovarian follicle contains layers of granulosa cells surrounding an antral cavity. To better understand the molecular basis of follicular growth and granulosa cell maturation, we study transcriptome profiling of granulosa cells from small (<5 mm) and large (>10 mm) bovine follicles using simultaneous method of Affymetrix microarrays (24,128 probe sets) and RNA-Seq data sets. This study proposes a computational method to discover the functional miRNA-mRNA regulatory modules, that is, groups of miRNAs and their target mRNAs that are believed to take part cooperatively in post-transcriptional gene regulation under specific conditions. The reconstructed network was named Integrated miRNA-mRNA Bipartite Network. 277 genes and 6 key modules were disclosed through clustering for mRNA master list. The 66 genes are among the genes that belong to at least two modules. All these genes, being involved in at least one of the phenomena, namely cell survival, proliferation, metastasis and apoptosis, have an overexpression pattern (P < 0.01). For miRNA master list, a total of 172 sequences were differentially expressed (P < 0.01) between dominant (large) and each of subordinate (small) follicles. Within the follicle, these miRNAs were predominantly expressed in mural granulosa cells. Finally, predicted and validated targets of these miRNAs enriched in dominant (large) follicles were identified, which are mapped to signaling pathways involved in follicular cell proliferation, steroidogenesis, PI3K/AKT/mTOR and Ras/Raf/MEK/ERK. The identification of miRNAs and their target mRNAs and the construction of their regulatory networks may give new insights into biological procedures.

Observation of the dynamics of follicular development in the ovary

The number of ovulated oocytes is different among mammals but does not vary much within the same species. In order to sustain periodic ovulation, follicular development must be coordinated at the tissue level. Elucidating the regulatory mechanisms of follicular development is difficult because the ovary has a complicated structure and it takes a long time for primordial follicles to develop into Graafian follicles. Therefore, it is not possible to observe follicular development by conventional experiments. The authors previously developed a new ovarian tissue culture method that enabled the observation of follicular development from the early follicle stage. These findings indicated that follicular interactions are important in regulating follicular development and ovulation. This review describes the current methods of observing follicular development in the ovary and the regulatory mechanisms of follicular development.

Effect of follicular aging on ATP content and mitochondria distribution in bovine oocytes

Hereford heifers were assigned randomly to three superstimulation groups and given FSH for 4 days in the short FSH group (n = 5) and FSH starvation group, (n = 5) or for 7 days in the long FSH group (n = 4). In vivo oocyte maturation was induced with LH given 12 hours after the last FSH treatment in short and long FSH groups and 84 hours after the last FSH treatment in the FSH starvation group. The ovaries were removed by colpotomy 18 to 20 hours after LH treatment to aspirate cumulus-oocyte complexes (COCs) from follicles 8 mm or greater. Cumulus-oocyte complexes were graded morphologically, and oocytes were processed for either mitochondrial staining or for ATP assay. Collection efficiency was similar among treatment groups, but a greater proportion of COCs were expanded (P < 0.01) and oocyte ATP content of the expanded COC tended to be greater (P < 0.09) in the long FSH group than other two groups. Oocytes in the FSH starvation group had a greater proportion (P = 0.01) of mitochondrial clusters (i.e., fewer scattered individual mitochondria). Individual mitochondria and mitochondrial clusters in oocytes from the long FSH and FSH starvation groups had twice the relative staining intensity (P < 0.01) compared to oocytes from the short FSH group. In summary, the long FSH superstimulation protocol yielded a greater proportion of expanded COCs that had oocytes with a scattered mitochondrial population and a greater ATP content than other two protocols. FSH starvation of 84 hours yielded a high proportion of grade 4 COCs characterized by a greater proportion of mitochondrial clusters within the oocyte.

Ovarian follicular dynamics and endocrine profiles in Polwarth ewes with high and low body condition

In this investigation we tested the hypothesis that static body condition (BC) of the ewe affects oestradiol and FSH with implications for subsequent follicular growth and turn-over. Sixteen Polwarth ewes were selected from a flock according to their BC score (scale: 1 emaciated; 5 obese). High BC (HBC) ewes (no. = 8) had a BC score of 4·1 (s.e. 0·1) and low BC (LBC) ewes (no. = 8) had a BC score of 1·9 (s.e. 0·1). Daily ultrasound examinations were performed and blood samples for progesterone, oestradiol and follicle-stimulating hormone (FSH) determination were collected. All HBC ewes (8/8) exhibited three waves of follicular development, while four LBC ewes (4/8) had two waves and the other four (4/8) had three waves of follicular development (P ≤ 0·05) during the interovulatory period. Overall, the emergences of 33 out of 44 follicular waves were preceded by significant increases in FSH concentrations. Maximum FSH concentrations were detected 0·9 ± 0·2 days before wave emergence. Oestradiol concentrations increased significantly during the growing phase in 38 out of 44 large follicles. A negative correlation between oestradiol and FSH was observed in HBC ewes. A similar inhibitory effect of oestradiol on FSH was observed in LBC ewes, irrespective of whether they developed two or three follicular waves. However, a longer period with high FSH was needed to promote the emergence of the second follicular wave in two-wave LBC ewes. Four HBC ewes had twin ovulations but no LBC ewes did (P ≤ 0·05). In HBC ewes, the follicular phase was characterized by lower oestradiol (6·5 (s.e. 1·0) pmol/l) but higher mean FSH concentrations (2·4 (s.e.0·4) μg/l) than in LBC ewes (8·9 (s.e. 1·2) pmol/l and 2·0 (s.e. 0·3) μg/l, respectively; P ≤ 0·05). The present results suggest that BC influences the pattern of follicular dynamics through changes in the endocrine milieu. Higher FSH concentrations during the follicular phase in HBC ewes, which allowed an extended period of follicular recruitment from a significantly larger pool of small antral follicles could explain the higher ovulation rate observed in this group.

Glutamine synthetase and alanine transaminase expression are decreased in livers of aged vs. young beef cows and GS can be upregulated by 17β-estradiol implants

Aged beef cows (≥ 8 yr of age) produce calves with lower birth and weaning weights. In mammals, aging is associated with reduced hepatic expression of glutamine synthetase (GS) and alanine transaminase (ALT), thus impaired hepatic Gln-Glu cycle function. To determine if the relative protein content of GS, ALT, aspartate transaminase (AST), glutamate transporters (EAAC1, GLT-1), and their regulating protein (GTRAP3-18) differed in biopsied liver tissue of (a) aged vs. young (3 to 4 yr old) nonlactating, nongestating Angus cows (Exp. 1 and 2) and (b) aged mixed-breed cows with and without COMPUDOSE (17β-estradiol) ear implants (Exp. 3), Western blot analyses were performed. In Exp. 1, 12 young (3.62 ± 0.01 yr) and 13 aged (10.08 ± 0.42 yr) cows grazed the same mixed forage for 42 d (August-October). In Exp. 2, 12 young (3.36 ± 0.01 yr) and 12 aged (10.38 ± 0.47 yr) cows were individually fed (1.03% of BW) a corn-silage-based diet to maintain BW for 20 d. For both Exp. 1 and 2, the effect of cow age was assessed by ANOVA using the MIXED procedure of SAS. Cow BW did not change ( ≥ 0.17). Hepatic ALT (78% and 61%) and GS (52% and 71%) protein content (Exp. 1 and 2, respectively) was decreased ( ≤ 0.01), whereas GTRAP3-18 (an inhibitor of EAAC1 activity) increased ( ≤ 0.01; 170% and 136%) and AST, GLT-1, and EAAC1 contents did not differ ( ≥ 0.17) in aged vs. young cows. In Exp. 2, free concentrations (nmol/g) of Glu, Ala, Gln, Arg, and Orn in liver homogenates were determined. Aged cows tended to have less ( = 0.10) free Gln (15.0%) than young cows, whereas other AA concentrations did not differ ( 0.26). In Exp. 3, 14 aged (> 10 yr) cows were randomly allotted ( = 7) to sham or COMPUDOSE (25.7 mg of 17β-estradiol) implant treatment (TRT), and had ad libitum access to alfalfa hay for 28 d. Blood and liver biopsies were collected 14 and 28 d after implant treatment. Treatment, time after implant (DAY), and TRT × DAY effects were assessed by ANOVA using the MIXED procedure of SAS. Cow BW was not affected ( ≥ 0.96). Implant increased ( ≤ 0.02) total plasma estradiol by 220% (5.07 vs. 1.58 pg/mL) and GS protein by 300%, whereas the relative content of other proteins was not altered ( ≥ 0.16). We conclude that hepatic expression of ALT and GS are reduced in aged vs. young cows, and administration of 17β-estradiol to aged cows increases plasma estradiol and hepatic GS, but not that of other proteins that support hepatic Glu metabolism.

Fertility after two doses of PGF2α concurrently or at 6-hour interval on the day of CIDR removal in 5-day CO-Synch progesterone-based synchronization protocols in beef heifers

Timed artificial insemination protocols in beef cattle are designed to synchronize ovulation in a greater proportion of females while simultaneously achieving acceptable pregnancy rates and a concise calving season. Protocols achieving such goals reduce time and labor associated with estrus detection and make advanced reproductive technologies implementable for beef producers. The objective of the study was to determine the effect of three different PGF2α (PGF) dosage schemes on artificial insemination (AI) pregnancy rates in beef heifers. We hypothesized that two doses of PGF administered concurrently at the time of controlled internal drug release (CIDR) removal would attain similar pregnancy rates compared with two doses given 6-hours apart-one at CIDR removal and the next 6 hours later in the 5-day CO-Synch progesterone-based synchronization protocol. Angus heifers (n = 875) at six locations in Washington, Idaho, and Oregon states were included in this study. Heifers within locations were assigned a body condition score (BCS). All heifers received a CIDR (1.38 g of progesterone) and 100 μg IM of GnRH on Day 0. The CIDRs were removed on Day 5, heifers were randomly allocated to one of three protocol groups: 1PGF (n = 291), received 25 mg IM of dinoprost (PGF); 2CO-PGF (n = 291), received 50 mg IM of dinoprost at CIDR removal, 2PGF (n = 293), received 25 mg IM of dinoprost at CIDR removal, and an additional 25 mg IM of dinoprost 6 hours later. Each heifer was given GnRH (100 μg, IM) and artificially inseminated at 56 hours after CIDR removal. Heifers were examined for pregnancy status between 50 and 70 days after AI to determine time of conception. A mixed-model procedure (PROC GLIMMIX of SAS) was used to evaluate the effect of treatments (1PGF, 2CO-PGF, and 2PGF) on AI pregnancy rates. Models included were treatments, BCS categories (≤5 and >5), and treatment by BCS category interaction. Location (state), handling facilities, handlers, inseminators, and AI sires were included as a random effect in the model. The 2PGF group had greater AI pregnancy rate of 63.6% (185/291), compared with the 2CO-PGF group at 51.9% (151/291) and 1PGF group at 54.9% (161/293; P < 0.001). An AI pregnancy rate of 50% (104/208) was observed for heifers with BCS less than or equal to 5 versus 58.9% (393/667) for heifers with BCS greater than 5 (P < 0.05). Location did not influence the AI pregnancy rate (P > 0.1). In conclusion, beef heifers received two 25-mg doses of PGF at 6-hour interval on Day 5 at CIDR insert removal in a 5-day CO-Synch + CIDR synchronization protocols achieved greater pregnancy compared with heifers received 50 mg of PGF concurrently at CIDR removal.

The expression pattern of microRNAs in granulosa cells of subordinate and dominant follicles during the early luteal phase of the bovine estrous cycle

This study aimed to investigate the miRNA expression patterns in granulosa cells of subordinate (SF) and dominant follicle (DF) during the early luteal phase of the bovine estrous cycle. For this, miRNA enriched total RNA isolated from granulosa cells of SF and DF obtained from heifers slaughtered at day 3 and day 7 of the estrous cycle was used for miRNAs deep sequencing. The results revealed that including 17 candidate novel miRNAs, several known miRNAs (n = 291-318) were detected in SF and DF at days 3 and 7 of the estrous cycle of which 244 miRNAs were common to all follicle groups. The let-7 families, bta-miR-10b, bta-miR-26a, bta-miR-99b and bta-miR-27b were among abundantly expressed miRNAs in both SF and DF at both days of the estrous cycle. Further analysis revealed that the expression patterns of 16 miRNAs including bta-miR-449a, bta-miR-449c and bta-miR-222 were differentially expressed between the granulosa cells of SF and DF at day 3 of the estrous cycle. However, at day 7 of the estrous cycle, 108 miRNAs including bta-miR-409a, bta-miR-383 and bta-miR-184 were differentially expressed between the two groups of granulosa cell revealing the presence of distinct miRNA expression profile changes between the two follicular stages at day 7 than day 3 of the estrous cycle. In addition, unlike the SF, marked temporal miRNA expression dynamics was observed in DF groups between day 3 and 7 of the estrous cycle. Target gene prediction and pathway analysis revealed that major signaling associated with follicular development including Wnt signaling, TGF-beta signaling, oocyte meiosis and GnRH signaling were affected by differentially expressed miRNAs. Thus, this study highlights the miRNA expression patterns of granulosa cells in subordinate and dominant follicles that could be associated with follicular recruitment, selection and dominance during the early luteal phase of the bovine estrous cycle.

Behavioural, follicular and hormonal characteristics of the oestrous cycle of Mexican Criollo cattle

The objective of the present study was to describe the behavioural, ovarian and hormonal characteristics of the oestrous cycle of Criollo cattle. Twenty-two cycling cows subjected to oestrus synchronisation were used to take blood samples every 4 h, to determine luteinising hormone (LH) until ovulation was detected by ultrasound and then every 24 h until the subsequent naturally occurring ovulation to determine progesterone concentrations. At the onset of synchronised oestrus, ovaries were examined by ultrasound every 8 h to determine dominant follicles until ovulation was detected, and daily afterwards to observe ovarian dynamics until the onset of the subsequent spontaneous behavioural oestrus. Time from oestrus to ovulation was higher in synchronised than in spontaneous oestrus (P < 0.01). Time from LH surge to ovulation was 40.5 h. When two- and three-wave cycles were compared, inter-ovulatory intervals were similar, growth rate of the preovulatory follicle was lower in two-wave cycles, time from onset of ovulatory wave to ovulation was higher in cycles with two waves and time from oestrus to ovulation was higher in three-wave cycles (P < 0.01). Corpus luteum volume averaged 1.3 cm3 and progesterone concentration peaked at an average 6.5 ng/mL. LH peak averaged 33.5 ng/mL during oestrus in all cows. Ovulatory follicle diameter ranged from 8 to 12 mm in either two- or three-wave cycles. Results suggested that overall times from oestrus and LH peak to ovulation are longer in Criollo cows than those in other breeds. This, along with information about growth rate, size and age of ovulatory follicles, may have implications for reviewing the optimum time for artificial insemination and how reproductive technologies are applied to Criollo cattle.

A review of factors that impact on the capacity of beef cattle females to conceive, maintain a pregnancy and wean a calf-Implications for reproductive efficiency in northern Australia

A review of factors that may impact on the capacity of beef cattle females, grazing semi-extensive to extensive pastures in northern Australia, to conceive, maintain a pregnancy and wean a calf was conducted. Pregnancy and weaning rates have generally been used to measure the reproductive performance of herds. However, this review recognises that reproductive efficiency and the general measures associated with it more effectively describe the economic performance of beef cattle enterprises. More specifically, reproductive efficiency is influenced by (1) pregnancy rate which is influenced by (i) age at puberty; (ii) duration of post-partum anoestrus; (iii) fertilisation failure and (iv) embryo survival; while (2) weight by number of calves per breeding female retained for mating is influenced by (i) cow survival; (ii) foetal survival; and (iii) calf survival; and (3) overall lifetime calf weight weaned per mating. These measures of reproductive efficiency are discussed in depth. Further, a range of infectious and non-infectious factors, namely, environmental, physiological, breed and genetic factors and their impact on these stages of the reproductive cycle are investigated and implications for the northern Australian beef industry are discussed. Finally, conclusions and recommendations to minimise reproductive inefficiencies based on current knowledge are presented.

Role of follicular estradiol-17beta in timing of luteolysis in heifers

The hypothesis was tested that estradiol (E2) from the ovarian follicles controls time of luteolysis. Time of luteolysis was evaluated by multiple measures of corpus luteum (CL) structure (area, volume) and function (progesterone [P4], luteal blood flow). The hypothesis for experiment 1 was that repeated ablation of follicles would reduce circulating E2 and delay luteolysis. Heifers were randomly assigned on Day 9 (Day 0 = ovulation) to three groups. All follicles >or=4 mm were ablated on Day 9 (group FA9; n = 6); Days 9-15 (group FA15; n = 6); or Days 9-21 (group FA21; n = 7). As expected, follicular ablation delayed (P < 0.001) the rise in circulating E2 and peak E2 concentrations (FA9, Day 17.6 +/- 0.7; FA15, Day 20.3 +/- 0.3; FA21, Day 24.9 +/- 0.3). Luteolysis (based on each measure) was delayed (P < 0.005) by repeated ablation of follicles, with earlier luteolysis (based on P4 decrease) in FA9 (Day 15.2 +/- 0.8) than FA15 (Day 16.5 +/- 0.4), and a further delay in FA21 (Day 18.3 +/- 0.5). The hypothesis of experiment 2 was that exogenous treatment with E2 would stimulate prostaglandin F(2alpha) (PGF) secretion and prevent the delay in luteolysis associated with follicular ablations. Follicles >or=4 mm were ablated from Day 9 to Day 17 (n = 15). Heifers were treated on Days 13 and 15 with 1.0 mg of estradiol benzoate (FAE2; n = 7) or vehicle (FAV; n = 8). Treatment with E2 induced PGF secretion (detected by PGF metabolite) and induced earlier (P < 0.02) luteolysis in FAE2 than in FAV, whether determined by circulating P4 or by area, volume, or blood flow of CL. In summary, ablation of follicles (>or=4 mm) delayed and treatment with E2 hastened luteolysis in heifers with ablated follicles. Thus, these results are consistent with an essential role for follicle E2 in timing of luteolysis.

Characterization of biological types of cattle (Cycle VII): Influence of postpartum interval and estrous cycle length on fertility12

Genetic improvement in reproductive efficiency through selection is difficult because many reproductive traits are binomial and have low heritabilities. Before genetic markers can be generated for fertility in cows, greater characterization of reproductive phenotypes is needed to understand the components of the trait. The current study tested the hypotheses that: 1) breeds vary in postpartum interval to estrus (PPIE) and estrous cycle length, 2) a longer estrous cycle immediately before breeding increased pregnancy rates, and 3) a greater number of cycles before breeding increased conception rates. The postpartum interval to estrus, estrous cycle length, and number of cycles before breeding were examined in F1 cows (n = 519) obtained from mating Hereford, Angus, and MARC III cows to Hereford, Angus, Simmental, Limousin, Charolais, Gelbvieh, and Red Angus sires. Cows were classified as having 0, 1, 2, or 3 observed estrous cycles before breeding. All traits analyzed were adjusted to constant BCS. Sire breed of the cow influenced length of the PPIE and number of cycles before the start of breeding (P <0.001). Simmental-sired cows had the shortest PPIE and greatest number of cycles before breeding, whereas Limousin-sired cows had the longest PPIE and least number of cycles before breeding. Cows with a greater number of cycles before breeding did not have greater conception rates than cows that had not exhibited standing estrus before breeding (P = 0.87). In cows that cycled before breeding, the length of the estrous cycle immediately before breeding was influenced by dam breed and BCS (P <0.01). Cows out of Hereford dams had shorter estrous cycles than cows out of MARC III or Angus dams, and estrous cycle length increased as BCS increased. Conception rate decreased as length of the estrous cycle immediately before breeding increased (P = 0.05, -2.2% per d of cycle length). Therefore, previously anestrous cows were just as likely to conceive as cows that had cycled before breeding, and an increased number of observed estrous cycles before breeding did not increase conception rates. There may be an influence of the length of estrous cycle immediately before breeding on conception rates, possibly because a longer estrous cycle results in a persistent follicle with greater potential for a lower quality oocyte. Breed differences in PPIE and estrous cycle length suggest that there are genetic components to these traits.

Association of Fertility with Numbers of Antral Follicles within a Follicular Wave During the Oestrous Cycle in Beef Cattle

The association between conception rate at first service and numbers of follicles developed during a follicular wave was examined in 102 suckled beef cows and 14 heifers. Follicular development was monitored using ultrasonography for either two (trial 1) or three (trial 2) consecutive oestrous cycles (pre-breeding, breeding and post-breeding equivalent). Animals were examined on alternate days from day 6 after first oestrus (day 0) until ovulation and from day 6 after insemination until next ovulation or day 24 of pregnancy and were observed for oestrus twice daily and inseminated artificially at either the second (trial 1) or third oestrus (trial 2). Cows were classified as having two or three waves of follicular development for each oestrous cycle. Numbers of follicles >or=4 mm per wave were determined, and based on the maximum diameter they attained, were classified as small (4-6 mm), medium (7-10 mm) or large (>or=11 mm) follicles. Total numbers of follicles, and primarily numbers of small and medium follicles, were affected by trial and within trial by cow, oestrous cycle and follicular wave. Heifers had more small and total numbers of follicles, but fewer large follicles than cows in trial 1 (p < 0.05). The average number of antral follicles per wave in the breeding cycle or post-breeding period did not affect conception rates, which averaged 84%. Repeatability of the total numbers of antral follicles between and among oestrous cycles and follicular waves ranged from 0.01 to 0.97. In conclusion, fertility was not affected by the numbers of antral follicles >or=4 mm in diameter in a single follicular wave.

Preovulatory, postovulatory, and postmaternal recognition effects of concentrations of progesterone on embryonic survival in the cow

Although fertilization rate usually is very high when male fertility is normal, pregnancy rates are below expectations when defined by the birth of live offspring in response to first service. Factors that affect establishment and retention of pregnancy include 1) preovulatory influences on the follicle and oocyte, 2) early postovulatory uterine and luteal function, 3) concentrations of hormones associated with trophoblastic and endometrial function during maternal recognition of pregnancy, and 4) less-well understood factors during the peri-attachment period. For example, decreased progesterone during preovulatory follicular development leads to a persistent follicle, premature resumption of meiosis, and a high incidence of embryonic death between the 2- and 16-cell stages. Elevated PGF(2alpha) during d 4 to 9 of the estrous cycle not only caused luteolysis but also had a direct embryotoxic effect during the morula-to-blastocyst transition. Ideal conditions during placentation and attachment are not clearly defined. Late embryonic mortality might be increased after ovulation of persistent or immature follicles. Nominal increases in secretion of PGF(2alpha) between d 30 and 35 might be important for attachment and placentation. Lower survival of embryos from wk 5 to wk 7 to 9 of gestation in the cow was associated with lower circulating concentrations of progesterone on wk 5. To maximize embryonic survival in the cow, management must provide high progesterone before estrus, quality detection of estrus, and timely insemination. Luteolytic influences of estradiol-17beta or PGF(2alpha) must be minimized early after mating and during maternal recognition of pregnancy, and high progesterone is needed during the late embryonic/early fetal period.

Prostaglandins and reproduction in female farm animals

Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, pyometra, and chronic endometritis. Improved therapeutic uses for prostaglandins will be developed when we understand better their involvement in implantation, maintenance of luteal function, and establishment and maintenance of pregnancy.

In vivo progestin treatments inhibit nitric oxide and endothelin-1-induced bovine endometrial prostaglandin (PG) E (PGE) secretion in vitro

Synchronization of estrus with progestins in cows has been reported to inhibit nitric oxide (NO) and endothelin-1 (ET-1)-stimulated bovine luteal PGE secretion without affecting prostaglandin F2alpha (PGF2alpha) secretion in vitro [Weems YS, Randel RD, Tatman S, Lewis A, Neuendorff DA, Weems CW. Does estrous synchronization affect corpus luteum (CL) function? Prostaglandins Other Lipid Mediat 2004;74:45-59]. Two experiments were conducted to determine the effects of NO donors, endothelin-1 (ET-1), and NO synthase (NOS) inhibitors on bovine caruncular endometrial secretion of PGE and PGF2alpha in vitro. In Experiment 1, estrus was synchronized in Brahman cows with Synchromate-B ear implants, which contained the synthetic progestin norgestamet. Days 14-15 caruncular endometrial slices were weighed, diced, and incubated in vitro with treatments. Treatments (100 ng/ml) were: Vehicle (control), l-NAME (NOS inhibitor), l-NMMA (NOS inhibitor), DETA (control), DETA-NONOate (NO donor), sodium nitroprusside (NO donor), or ET-1. In Experiment 2, estrus was synchronized in Brahman cows with either Lutalyse (PGF2alpha) or a controlled intravaginal drug releasing device (CIDR-containing progesterone) or estrus was not synchronized. Days 14-15 caruncular endometrial slices were weighed, diced, and incubated in vitro with treatments. Treatments (100 ng/ml) were: vehicle, l-NAME, l-NMMA, DETA, DETA-NONOate, sodium nitroprusside, SNAP (NO donor) or ET-1. Tissues were incubated in M-199 for 1h without treatments and with treatments for 4 and 8h in both experiments. Media were analyzed for concentrations of PGE and PGF2alpha by radioimmunoassay (RIA). Hormone data in Experiments 1 and 2 were analyzed by 2x7 and 3x2x8 factorial design for ANOVA, respectively. Concentrations of PGE and PGF2alpha in media increased (P< or =0.05) from 4 to 8 h regardless of treatment group in Experiment 1, but did not differ (P> or =0.05) among treatments. In Experiment 2, concentrations of PGE and PGF2alpha increased (P< or =0.05) with time in all treatment groups of all three synchronization regimens. DETA-NONOate, SNAP, and sodium nitroprusside (NO donors) and ET-1 increased caruncular endometrial (P< or =0.05) secretion of PGE2 in unsynchronized and Lutalyse synchronized cows, but not when estrus was synchronized with a CIDR (P> or =0.05). No treatment increased (P> or =0.05) PGF2alpha in any synchronization regimen. It is concluded that norgestamet in Synchromate-B ear implants or progesterone in a CIDR alters NO or ET-1-induced secretion of PGE by bovine caruncular endometrium and could interfere with implantation by altering the PGE:PGF2alpha ratio resulting in increased embryonic losses during early pregnancy.

Number of follicular waves and their effect on pregnancy rate in the cow

In the study, the relationship of follicular growth waves, oestradiol and pregnancy rates were investigated during oestrus cycle in cows. A total of 22, Brown Swiss cows (3-5 years old) were used for the study. The ovaries of animals were examined from sixth day of cycle to next oestrus by ultrasound. The follicles that were present in the ovarium were recorded. Follicular growth was observed every day by means of ultrasound examination. The blood samples were taken for analysis of oestradiol simultaneously with ultrasound examinations. The oestrus animals were inseminated. Each animal that inseminated was examined by ultrasound on day 28 after insemination for pregnancy diagnosis. Two follicular growth waves were observed in nine of 22 (40.9%), three waves in 13 of 22 (59.1%) animals. The oestradiol was found in the same concentration but in different release patterns between two and three waves animals. Pregnancy rate in cows with three and two follicular waves did not differ. In conclusion, emergence of three waves of follicular growth was higher in Brown Swiss cows, the analysis of oestradiol could be used for determination of the wave numbers and the animals with different waves may have had the same pregnancy rates.

Form and function of the corpus luteum during the human menstrual cycle

OBJECTIVE

To characterize the growth and regression of the corpus luteum (CL) during an interovulatory interval (IOI) using serial transvaginal ultrasonography.

METHODS

Fifty healthy women of reproductive age with a history of regular menstrual cycles underwent daily transvaginal ultrasonography for one IOI. Measurements of luteal area and luteal numerical pixel value (NPV) were recorded each day after ovulation until the CL could no longer be detected. Blood was drawn every third day during the IOI to measure serum concentrations of progesterone and estradiol-17beta.

RESULTS

Corpora lutea were of two morphological types: those with a central fluid-filled cavity (CFFC) (78%) and those without (22%). Eighty-eight percent of women exhibited a CL containing a CFFC 2 days after ovulation, followed by 34% 13 days after ovulation and 2% 27 days after ovulation. Luteal area, progesterone concentration and estradiol concentration increased for approximately the first 6 days following ovulation followed by a subsequent decline. Luteal NPV decreased from days 1 to 11 and increased during days 11-16. Changes in luteal area, NPV, progesterone and estradiol concentrations did not differ in women with two versus three waves of follicular development.

CONCLUSIONS

Peak luteal function, as determined by maximum luteal area, progesterone concentration and estradiol concentration, is observed 6 days following ovulation. Luteal NPV is reflective of morphological and endocrinological changes in the CL. The development of a CFFC during luteinization is a normal physiological phenomenon. The CL can be detected, but is not functional, during the follicular phase of the menstrual cycle.