Assessment of the main pathogens associated with clinical and subclinical endometritis in cows by culture and MALDI-TOF mass spectrometry identification

Clinical endometritis (CE) and subclinical endometritis (SCE) are diseases that affect dairy cows during the puerperium, causing negative effects on the animals' milk production and fertility. The objective of this study was to assess the main bacteria related to cases of CE and SCE from uterine samples of dairy cows in Brazilian herds. Selective and differential media were used for isolation of aerobic and anaerobic bacteria and further MALDI-TOF mass spectrometry (MS) identification. A total of 279 lactating dairy cows with 28 to 33 d in milk from 6 commercial farms were evaluated. Initially, cows were classified in 3 groups: cytologic healthy cows (n = 161), cows with CE (n = 83), and cows with SCE (n = 35). Healthy animals presented 97 species, followed by the CE group with 53 identified species, and SCE cows presented only 21 bacterial species. We found a significantly higher isolation rate of Trueperella pyogenes in CE (26.5%) cows compared with healthy and SCE cows. Some anaerobic species were exclusively isolated from the CE group, even though they presented lower frequency. Interestingly, 18.1% of samples from CE cows and 40% of SCE cows were negative to bacterial isolation. Despite the use of culture-dependent methods instead of molecular methods, the present study enabled the identification of a complex community of 127 different species from 48 genera, composed of aerobic and anaerobic bacterial species among the 3 different animal groups. The method of sample collection, culture, and identification by MALDI-TOF MS were essential for the success of the analyses.

Unravelling the role of 17β-estradiol on advancing uterine luteolytic cascade in cattle

In cattle, 17β-estradiol (E2) stimulates prostaglandin F2α (PGF2α) synthesis, which causes luteolysis. Except for the well-established upregulation of oxytocin receptor gene (OXTR), molecular mechanisms of E2-induced PGF2α release in vivo remain unknown. We hypothesized that E2-induced PGF2α release requires de novo transcription of components of the PGF2α synthesis machinery. Beef cows (n = 52) were assigned to remain untreated (Control; n = 10), to receive 50% ethanol infusion intravenously (Placebo; n = 21), or 3 mg E2 in 50% ethanol infusion intravenously (Estradiol; n = 21) on day 15 (D15) after estrus. We collected a single endometrial biopsy per animal at the time of the treatment (0h; Control B0h group), 4 hours (4h; Placebo B4h group and Estradiol B4h group), or 7 hours (7h; Placebo B7h group and Estradiol B7h group) post-treatment. Compared to the Placebo group, the Estradiol group presented significantly greater 13,14-dihydro-15-keto-PGF2α concentrations between 4h and 7h and underwent earlier luteolysis. At 4h, the qPCR analysis showed a lower abundance of ESR1, ESR2 and aldo-keto reductase family 1 member B1 (AKR1B1) genes in the Estradiol B4h group, and a greater abundance of OXTR compared to the Placebo B4h group. Similarly, the E2 treatment significantly reduced the abundance of AKR1B1, and AKR1C4 in the Estradiol B7h group, compared to the placebo group. Overall, E2-induced PGF2α release and luteolysis involved an unexpected and transient downregulation of components of the PGF2α-synthesis cascade, except for OXTR, which was upregulated. Collectively, our data suggest that E2 connects newly-synthesized OXTR to pre-existing cellular machinery to synthesize PGF2α and cause luteal regression.

Effects of estradiol treatments on PGF2α release in beef heifers submitted to estrous resynchronization 14 days after timed-AI

The effects of 17β-estradiol (E2) or estradiol benzoate (EB) on PGF2α release were studied in bred-non-pregnant and pregnant Nelore beef heifers. The day of timed artificial insemination (TAI) was designated day 0 (D0), and a single treatment was given on D14. All heifers also received an intravaginal P4 device on D14, and were randomly assigned to three groups: Control (C, P4 device only, n = 12); E2 (1 mg E2 + 9 mg P4, n = 10); or EB (1 mg, n = 10). Blood samples were collected hourly for 8 hours after treatment (Hours 0-8) to measure plasma concentrations (pg/mL) of a PGF2α metabolite (PGFM). The P4 device was removed on D22 and pregnancy was diagnosed on D28. Pregnancy rate was not different among groups (C, n = 7/12; E2, n = 5/10; EB, n = 5/10). More (P < 0.05) heifers had a CV-identified prominent PGFM pulse (peak of > 100 pg/mL) in E2 group (6/10) than in EB (1/10) and C (0/12) groups. Hourly concentration of PGFM for Hours 0 to 8 showed significant effects of group and hour and an interaction of group by hour but did not show an interaction of group or hour with pregnancy status. In preliminary post-hoc analyses, PGFM concentrations during Hours 0 to 8 and pulse characteristics were analyzed within each pregnancy status. For the non-pregnant heifers, a group-by-hour interaction was detected tentatively indicating an increase (P < 0.005) in PGFM concentrations in E2 group from Hours 4 to 6 and in EB group at Hours 5 and 6. Maximum PGFM concentration during Hours 0 to 8 did not differ (P > 0.1) between E2 (124 ± 23) and EB (110 ± 30) groups, but was greater (P < 0.05) in each group than in C (32 ± 3). Furthermore, PGFM concentrations of pulses at the peak, amplitude, and area under pulse curve (pg/mL/h) were greater (P < 0.05) in E2 group than in C group whereas the EB group did not differ (P > 0.1) from the other groups. For pregnant heifers, no effects of group, hour, or their interaction were detected in PGFM concentrations during the hourly sessions, except that maximum PGFM concentration was greater (P < 0.05) in E2 than in EB and C groups. In addition, the number of prominent pulses was greater in E2 group than in Control or EB groups. In conclusion, PGFM increased earlier and in greater concentration combined for bred-non-pregnant and pregnant heifers treated 14 days after TAI with 1 mg E2 plus 9 mg P4 than with 1 mg EB. Tentatively, a positive effect for each of E2 and EB on PGFM concentrations was attenuated in pregnant heifers.

Type I interferon receptors and interferon-τ-stimulated genes in peripheral blood mononuclear cells and polymorphonuclear leucocytes during early pregnancy in beef heifers

This study characterised the expression of interferon (IFN)-τ-stimulated genes (ISGs) and Type I IFN receptors in circulating polymorphonuclear cells (PMNs) of beef heifers and compared it with expression in peripheral blood mononuclear cells (PBMCs) up to Day 20 of gestation. Nelore heifers (n=26) were subjected to fixed-time AI (FTAI) on Day 0. PMNs and PBMCs were isolated on Days 0, 10, 14, 16, 18 and 20 after FTAI. The abundance of target transcripts (ubiquitin-like protein (ISG15), 2'-5'-oligoadenylate synthetase 1 (OAS1), myxovirus resistance 1 (MX1), myxovirus resistance 2 (MX2), IFN receptor I (IFNAR1) and IFN receptor 2 (IFNAR2)) was determined using real-time quantitative polymerase chain reaction and compared between pregnant (n=8) and non-pregnant (n=9) females. In both PBMCs and PMNs, ISG15 and OAS1 expression was greater in pregnant than non-pregnant heifers on Days 18 and 20. There were no significant differences in the expression of ISGs between PBMCs and PMNs. A time effect on expression was found for IFNAR1 in PBMCs and IFNAR2 in PMNs, with decreased expression of both genes on Days 18 and 20. When the expression of these genes was compared between cell types only in pregnant heifers, IFNAR2 expression in PMNs had an earlier decrease when compared to its expression in PBMCs, starting from Day 18. In conclusion, PMNs do not respond earlier to the conceptus stimulus, and ISG15 and OAS1 expression in both PMNs and PBMCs can be used as a suitable marker for pregnancy diagnosis on Days 18 and 20. In addition, gestational status did not affect IFNAR1 and IFNAR2 expression, but IFNAR2 showed a distinct response between PMNs and PBMCs of pregnant heifers.

49 The dynamic changes in uterine morphology and function during the proestrus-diestrus transition in beef cattle

In cattle, early development of the non-attaching embryo depends exclusively on the biochemical properties of the intrauterine milieu. As the embryo transitions from the oviduct to the tip of the uterine horn around 4 days after oestrus, little is known about uterine functions that modulate the milieu composition and potentially determine pregnancy success. The objective was to characterise changes in uterine luminal fluid (ULF) accumulation and absorption, endometrial vascularity, and endometrial thickness in response to progesterone fluctuations during the peri-ovulatory period in beef heifers. Fourteen Bos indicus heifers that presented a prostaglandin F2α (PGF2α) responsive CL received 500µg of PGF2α analogue i.m. (PGF) and were examined daily by rectal B-mode and pulse-wave colour-Doppler ultrasonography until the fifth day after oestrus (oestrus=Day 0). Plasma progesterone (P4) concentrations were measured daily. Uterine luminal fluid score was given based on the accumulation of fluid throughout the entire organ (0, no fluid, to 4). Measurement of the main ovarian structures, endometrial thickness, uterine luminal fluid score, and luminal fluid area of the cranial portion of the uterine horn ipsilateral to the preovulatory follicle and subsequent CL were executed by B-mode ultrasonography and endometrial vascularity by colour Doppler. The fixed effect of day was analysed by ANOVA. There was an effect of day on endometrial vascularity, endometrial thickness, and uterine luminal fluid score (P≤0.01) as well as uterine luminal fluid area (P≤0.05). Endometrial vascularity and endometrial thickness increased after PGF injection to peak on Day −1, whereas uterine fluid score peaked on Day 0. Interestingly, cranial uterine luminal fluid area peaked twice, on Day −1 and Day 5. Vascularity, thickness, and fluid accumulation decreased gradually from Day 0 to Day 5. There was a negative correlation (r=−0.55) between the sum of daily P4 concentrations during proestrus (i.e. from PGF to oestrus) and the greatest ULF score measured (P=0.05). Length of proestrus was correlated negatively (r=−0.69) with the increase in uterine body thickness during proestrus (P=0.03). The sum of daily luminal fluid scores, from PGF injection to Day 5, was double for heifers grouped within the upper third for that variable compared with those grouped within the lower third. In conclusion, peri-ovulatory transformations in uterine morphology and function are dramatic and vary in duration and in intensity among animals. Temporal changes in intraluminal fluid accumulation and absorption at the site of embryo arrival may change its biochemical composition. Potential implications for embryo receptivity and reproductive outcomes deserve further investigation.

Increased pregnancy rate in beef heifers resynchronized with estradiol at 14 days after TAI

We aimed to evaluate the treatment with estradiol benzoate (EB) or 17β-estradiol (E2) associated with progesterone (P4) for resynchronization of ovulation 14 days after timed artificial insemination (TAI). In Experiment 1 (Exp. 1), Nelore heifers were submitted to TAI (D0). On D14, the animals received an intravaginal P4 device and were randomly assigned to one of three groups: control (no treatment; n = 17); EB (1  mg EB; n = 17); and E2+P4 (1 mg E2 + 9 mg P4; n = 18). Ultrasonography evaluations were performed daily from D14 to D22 to map follicular and luteal dynamics. On D22, the P4 devices were removed and non-pregnant (NP) animals were determined using corpus luteum blood flow Doppler ultrasonography. In Exp. 2, 1295 beef heifers were resynchronized and randomly allocated to the same experimental groups as described in Exp. 1. On D22, the largest follicle (LF) was measured in NP and a second TAI was performed on D24. In a subset of heifers (n = 337), an estrus detection patch was used between D22 and D24 to monitor estrus expression and the LF was measured at D24. Confirmatory diagnosis of pregnancy was performed between D37-67 and D43-67 after first and second TAI, respectively. In Exp 1, the proportion of heifers with a synchronized follicular wave emergence (from 3 to 5 days after treatment) was greater (P < 0.05) in the EB group (93.8%) than in the control (62.5%) and E2+P4 (64.7%) groups. Structural luteolysis occurred earlier (P < 0.05) in the EB and E2+P4 groups than in the controls. The pregnancy rate after first TAI did not differ (P > 0.1) among the groups at D22 and at confirmatory diagnosis in both experiments. In Exp 2, the potential pregnancy loss between D22 and D37-67 was similar (P > 0.1) in the control (19% [36/185]), EB (15% [28/182]) and E2+P4 (15% [28/184]) groups. The LF diameter (mm) on D22 was greater (P < 0.05) in the control group (11.9 ± 0.1) than in EB (11.3 ± 0.1) and E2+P4 (11.5 ± 0.1). No difference (P > 0.1) was observed in the proportion of heifers detected in estrus, but LF growth rate (mm/day) between D22 and D24 was greater (P < 0.05) in EB group (0.9 ± 0.08) than in control (0.6 ± 0.07) and E2+P4 (0.7 ± 0.09) groups. The pregnancy rate for the second TAI was greater (P < 0.05) in the EB group (47% [94/200]) than in the control (37% [76/203]), but did not differ (P > 0.1) from the E2+P4 group (43% [93/214]). In conclusion, the treatment with 1 mg EB or 1 mg E2 + 9 mg P4 at 14 days post-TAI anticipates luteolysis in NP heifers but does not compromise pregnancy. The EB treatment induces a new synchronized follicle wave emergence and increases the pregnancy rate of resynchronized NP heifers.

170 Embryonic loss and pregnancy rate in response to resynchronisation using oestradiol benzoate or injectable progesterone at 14 days after timed AI in Bos taurus×Bos indicus beef heifers

The effect of the exposure of pregnant cattle to oestradiol benzoate (EB) or injectable long-acting progesterone (iP4), as well as their use for early resynchronisation of non-pregnant (NP) females within the second week after timed AI (TAI), is yet to be assessed. This study aimed to assess the pregnancy rate and embryonic loss of cross-bred Bos taurus×Bos indicus beef heifers in response to an EB- or iP4-based resynchronisation strategy implemented 14 days after the first TAI. A total of 677 cyclic heifers (Braford and Brangus; 24 months old) were subjected to an EB/P4 synchronisation protocol for the first TAI (Day 0=TAI). On Day 14, all heifers received a new P4 intravaginal device (1g, Sincrogest, Ourofino Saúde Animal) and were randomly assigned to two groups: EB (1mg intramuscularly, Sincrodiol; n=339) or iP4 (75 mg intramuscularly, Sincrogest Injetável; n=338). On Day 22, P4 devices were removed and heifers underwent colour Doppler ultrasonography evaluation. Non-pregnant females were identified by the assessment of structural regression of the corpus luteum, as previously reported by our group. On Day 22, NP heifers received 1mg of oestradiol cipionate (SincroCP), 250µg of sodium cloprostenol (Sincrocio), and 200IU of equine chorionic gonadotrophin (SincroeCG), and they were inseminated on Day 24. On Day 22, the diameter of the preovulatory follicle (POF) was also recorded. Pregnancy was diagnosed via B-mode ultrasonography on Days 35-40 and 54. Statistical analyses were performed using SAS software (ver. 9.2, SAS Institute Inc.). The MIXED procedure was used to evaluate the POF diameter, and the GLIMMIX procedure was used to develop a multivariate model including treatment, breed, age, farm (1-7), and possible interactions of treatment with farm, breed, and age to evaluate the binomial data (pregnancy rates and embryonic loss). In NP heifers, the diameter of the POF on Day 22 did not differ (P&gt;0.05) between the EB (9.77±0.25mm) and iP4 (9.92±0.22 mm) groups. Exposure to EB or iP4 on Day 14 post-TAI did not influence pregnancy rates as assessed on Day 22 (56.3% (191/339) vs. 60.1% (203/338)) and on Days 35-40 (49.6% (168/339) vs. 53.3% (180/338)). In addition, embryonic loss between Days 22 and 35-40 was not different between the EB (12%, 23/191) and iP4 (11.3%, 23/203) groups. On the other hand, pregnancy rates in heifers submitted to the second TAI were greater (P=0.01) in the EB group (45.95%, 68/148) than in the iP4 group (31.85%, 43/135). In conclusion, improved pregnancy rates can be achieved using 1mg of EB associated with a P4 intravaginal device on Day 14 of the resynchronisation protocol without affecting the first TAI pregnancy rates and embryonic loss. However, further investigation is warranted to assess the lower pregnancy rates obtained in response to the association of iP4 and P4 device. This research was supported by FAPESP (2015/10606-9; 2019/15514-6), Graduate Studies Support Program (PAPG-UNIPAMPA), and Ourofino Saúde Animal.

64 Prediction of pregnancy and early embryo loss through OAS-1 expression, concentrations of pregnancy-associated glycoproteins, and Doppler ultrasonography in beef cattle

We aimed to compare three methods to detect pregnancy based on interferon-tau stimulated gene expression in peripheral blood polymorphonuclear cells and Doppler ultrasonography (Doppler-US) 20 days after timed AI and the concentrations of pregnancy associated glycoproteins (PAGs) 25 days after timed AI. Our second objective was to compare interferon-tau stimulated genes and PAGs as early embryo loss (EEL) predictors. Nelore cows (n=144) and heifers (n=103) were submitted to timed AI (Day (D) 0). On D20, polymorphonuclear cells were isolated from blood samples by Ficoll gradient (GE Healthcare), and the RNA was extracted. Expression of the interferon-tau stimulated gene (OAS-1) was quantified by qPCR and normalized to reference genes (GAPDH and ACTB). On D25, blood was collected from the jugular vein and PAG concentrations were measured by an in-house enzyme-linked immunosorbent assay. Pregnancy diagnoses were performed on D20 by luteolysis detection with Doppler-US and on D30 by detection of an embryo by heartbeat. Animals were classified as pregnant (P; fetus on D30), non-P (NP; no active corpus luteum on D20), and EEL (active corpus luteum on D20 but NP on D30). Expression of OAS-1 and PAG concentrations were analysed by analysis of variance using PROC MIXED of SAS considering the effects of group, category, and their interaction. Receiver operating characteristic curves were created, and the area under the curve (AUC), accuracy, specificity, and sensitivity were calculated for pregnancy predictions on D20 (OAS-1 and Doppler-US) and D25 (PAGs) compared with the standard diagnosis method on D30. Expression of OAS-1 and PAG concentrations were greater (P&lt;0.01) in the P (2.4±0.2 and 4.8±0.2ngmL−1, respectively) compared with the NP (0.50±0.1 and 1.2±0.2ngmL−1, respectively) and EEL (0.8±0.2 and 1.0±0.2ngmL−1, respectively) groups. Receiver operating characteristic analysis indicated that OAS-1, Doppler, and PAGs were significant (P&lt;0.01) predictors of pregnancy in heifers (AUC=0.86, 0.92, and 0.94, respectively) and cows (AUC=0.82, 0.94, and 0.95, respectively). The PAGs and Doppler-US presented higher accuracy on diagnosing pregnancy (92 and 89% for heifers, 94 and 93% for cows, respectively) than OAS-1 (81% for heifers and 75% for cows). Doppler-US was 100% sensitive to detect nonpregnant females, which avoided false negative results, whereas PAG concentrations presented a higher specificity (86% for heifers and cows) when compared with Doppler-US and OAS-1 (76 and 65% for heifers, 85 and 75% for cows, respectively). On D25, PAGs were 90% accurate to detect heifers and cows that would experience EEL, whereas on D20, OAS-1 was 50% accurate. In conclusion, Doppler-US can be used as early as D20 with high accuracy and sensitivity. Likely, the use of PAG concentrations on D25 is highly accurate and is more effective at detecting EEL. Pregnancy diagnosis through OAS-1 expression is not as accurate as the other methods and could not efficiently predict EEL. This research was supported by FAPESP (2015/106069; 2017/134729).

91 Invivo- and invitro-produced bovine embryos have different microRNA profiles after invitro individual culture

Invivo- and invitro-produced bovine embryos have different metabolic characteristics, embryonic development, and gene transcription. Additionally, pregnancy rates at 30 days (on average 51% and 34% when using fixed-time AI and invitro production, respectively) are different in beef cattle. Between Days 8 and 17 of the oestrous cycle, concurrent with embryo-maternal recognition, is when 40% of embryonic losses occur. These losses may occur due to altered embryo-maternal cross-talk. MicroRNA (miRNA) can be involved in this communication; however, its potentially regulated pathways in invivo and invitro embryos on Day 9 are unknown. Our hypothesis is that bovine embryos produced invivo and invitro contain different miRNA profiles, even after invivo bovine embryo were invitro cultured. Cows had the follicular wave synchronized and were superovulated to produce invivo or invitro bovine embryos. For the invitro group, on Day −8 of the protocol, the dominant follicles were recovered by ovum pickup, and invitro embryo production was performed to obtain embryos. For the invivo group, on Day −8, the cows were inseminated 12 and 24h after GnRH analogue application and on Day 7 after expected oestrus, uterine flushing was performed to obtain the embryos. Embryos from both groups were individually cultured for 48h. Three pools (of 5 embryos each) per group were used for reverse transcription of miRNAs from total RNA using miScript II RT Kit (Qiagen). Relative levels of 383 bovine miRNAs were determined using the geometric mean of miR-99b, RNU43 snoRNA, and Hm/Ms/Rt U1 snRNA by RT-qPCR. Differences in relative levels of miRNAs were determined by Student's t-test. A total of 210 miRNAs were detected in invivo and invitro embryos, and 13 out of 210 were differently identified between the groups. In invivo embryos, 6 miRNAs were up-regulated, whereas 7 miRNAs were up-regulated in invitro embryos. TARGETSCAN software was used to identify genes predicted as modulated by each miRNA. The top 100 genes predicted were used to identify enriched pathways according to DAVID Bioinformatics Resources. The miRNAs (miR-129, miR-132, miR-155, miR-192, miR-215, and miR-377) up-regulated in invivo embryos modulated pathways that include signaling pathways regulating pluripotency of stem cells (16 genes), TGF-β (11), hippo (10), oestrogen (8), and cell cycle (7). Moreover, miR-23a, miR-338, miR-34a, miR-491, miR-92b, miR-940, and miR-1271, which were increased in invitro embryos, regulate PI3K-Akt (17 genes), signaling pathways regulating pluripotency of stem cells (10), oestrogen (9), toll-like receptor (9), Wnt (9), and HIF-1 (7). The results demonstrate that even after 48h of invitro culture, bovine embryos produced invivo and invitro have different miRNA profiles that modulate pathways associated with embryonic development on Day 9. Furthermore, these results suggest that bioactive molecules, such as miRNAs, can modify embryo-maternal cross-talk, depending on the environment where the embryos are produced. Funding was provided by FAPESP 2017/19681-9, 2014/22887-0, and 2018/13155-6.

12 Assessment of oocyte and embryo production in senescent beef cows

Fertility associated with age has been poorly documented in cattle. There is evidence that more than 50% of cows became infertile (failure to bear a calf for two successive years) at the age of 15. The causes of infertility in cows have been attributed to poor oocyte quality and/or follicle depletion. The present study aimed to compare the rates of oocyte and invitro embryo production of fertile cows older than 15 years. Sixteen Nellore cows (Bos taurus indicus) 200.3±4.9 months old were submitted to two ovum pickup series (OPU1 and OPU2) at a 2-year (2017 and 2019) interval. Before the OPU1 of each series, the cows were prepared with an IM injection of 2mg estradiol benzoate and 0.15mg prostaglandin F2α analogue and a progesterone-releasing intravaginal device (1g). After five days, the progesterone-releasing intravaginal device was withdrawn and the OPU1 was performed. The second OPU (OPU2) was performed 5 days later to aspirate only the growing follicles. The number and morphologic quality of recovered cumulus-oocyte complexes were registered. After IVM (tissue culture medium 199) and fertilization (Tyrode's solution) of cumulus-oocyte complexes, the presumptive zygotes were cultured in synthetic oviductal fluid with amino acids to assess developmental rates to blastocyst. Data were analysed by chi-squared and Wilcoxon test. The number of oocytes recovered at OPU1 was higher in 2107 than in 2019 (27.8±6.6 vs. 10.8±4.2; P&lt;0.01), whereas in OPU2 the production of oocytes was not different (14.7±3.3 vs. 10.9±3.1). In OPU1, eight cows in 2017 and four in 2019 produced more than 20 oocytes, compared with only one cow in OPU2 of both years (P=0.02). Although there was no significant difference in the proportion of viable oocytes in OPU1 (83.6% and 87.2%) and OPU2 (85.5 and 68.0%), more viable oocytes were produced at OPU1 of 2017 (23.2±5.8) compared with OPU1 of 2019 (9.4±4.1), OPU2 of 2017 (12.6±2.7) and OPU2 of 2019 (7.4±2.4), respectively (P&lt;0.05). There was no significant difference in the proportion of cleaved oocytes in OPU1 (74.2 and 75.1%) and OPU2 (68.9 and 79.8%). Two cows in 2017 (12.5%) and five in 2019 (31.2%) did not produce embryos in both OPUs. Cows produced more embryos (blastocysts) in OPU1 at 2017 (7.3±1.6) than 2019 (2.8±0.6; P&lt;0.05), whereas in OPU2 there was no difference (4.1±0.8 and 3.1±0.8). In conclusion, senescent fertile cows decreases the number of oocytes and embryos as they approach 20 years of age; however, the quality of oocytes does not appear to be compromised. Financial support was provided by FAPESP (proc. 2018/07450-5).

Supplemental progesterone induces temporal changes in luteal development and endometrial transcription in beef cattle

Long-acting injectable progesterone (iP4) supplementation during early diestrus is a strategy to increase conception rates in cow-calf beef operations. However, iP4 treatment causes early functional and structural regression of the corpus luteum (CL) in a proportion of iP4-treated animals, resulting in pregnancy loss. The hypothesis evaluated was that iP4 accelerates downregulation of sex-steroid receptors (PGR, ESR1, ESR2) during early to mid-diestrus and the upregulation of genes controlling PGF₂α secretion (OXTR, PTGS2, AKR1B1) during late diestrus in the endometrium. Ovulations of cyclic, multiparous Nelore (Bos indicus) cows were synchronized, and cows were divided to receive placebo or 300 mg iP4 3 d postovulation (D3). Growth and vascularization of luteal tissue were evaluated by ultrasonography. Blood samples were collected from 3 d postovulation to 3 d after luteolysis, and P4 plasma concentrations were measured by radioimmunoassay. On days 3, 5, 7, 9, 11, 13, and 16 luminal endometrial samples were taken using a cytologic brush. Transcript abundance was measured by qPCR. Structural luteolysis occurred 3 d earlier in cows receiving iP4 compared to the control group. Analyzing only cows that received iP4, those that presented early luteolysis (ie, ≤ D16) showed a decrease in CL area and P4 concentration after D5, compared to the control group. Cows that presented early luteolysis showed a reduced abundance of transcripts on D5 for the ESR2 gene and a greater abundance of transcripts for OXTR and ESR1 on D16, compared to cows that did not present early luteolysis. The iP4-induced early luteolysis can be explained by two nonexclusive possibilities: the activation of uterine mechanisms that trigger early secretion of endometrial PGF pulses and the formation of a subfunctional CL that is prone to early regression.

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.

Supplementation with long-acting progesterone in early diestrus in beef cattle: I. effect of artificial insemination on onset of luteolysis

Progesterone (P4) supplementation in early diestrus advances changes in the endometrial transcriptome, stimulating embryonic development. However, it also induces early onset of luteolysis. Occurrence of luteolysis before D16 postmating can be detrimental to fertility. A potential counteracting role of the elongating conceptus on early luteolysis is understood poorly. The aim of the study was to evaluate the effect of artificial insemination (AI; ie, pregnancy) on the temporal dynamics of luteolysis of cows supplemented with P4. Nonsuckled beef cows were inseminated at 12 h after estrus (D0: ovulation) or were not inseminated (no-AI). On D3, the AI cows were assigned to receive a single dose of 150 mg of injectable long-acting P4 via intramuscular injection (AI + iP4; n = 23), and the no-AI cows were assigned to receive iP4 (iP4; n = 21) or saline (control, n = 22). Corpus luteum (CL) development and regression were determined by ultrasonography (US) between D3 and D21. Plasma P4 concentrations were measured on D3 and every other day from D9 to D21. Pregnancy status was determined by US (D28‒D32). iP4 supplementation reduced luteal development (D5-D10) compared to the control group and increased incidence of luteolysis between D14 and D15. On D15, the proportion of cows that underwent luteolysis and plasma P4 concentrations differed between the iP4 group (47.6; 2.10 ± 0.47) and the control group (13.6; 4.40 ± 0.46) and was intermediate in the AI + iP4 group, respectively (26.1%; 3.70 ± 0.45 ng/mL; P < 0.05). The AI effects were due to the pregnant cows (n = 7). Considering nonpregnant cows only, the proportion of early luteolysis in the AI + iP4 group (37.5%) was similar to the iP4 group. Pregnancy was not established in cows having a shortened luteal lifespan. Indeed, interval to luteolysis in the AI + iP4 group (15.50 ± 0.66 d) was similar to the iP4 group (16.38 ± 0.46 d), but less than the control group (17.38 ± 0.40 d; P = 0.05). In conclusion, the effect of AI on extending luteal lifespan occurred exclusively in cows that maintained pregnancy.

Supplementation with sunflower seeds in beef cattle did not impact on oocyte and in vitro embryo production

Supplementation with compounds rich in linoleic acid, including sunflower seed supplementation, promotes increase in conception rates in cows. We aimed to evaluate whether the sunflower seed (linoleic acid source) supplementation in beef donor females alters the plasma concentrations of cholesterol, triglycerides, HDL and LDL, increases the number and quality of oocytes, increases the cleavage rates and determines an improvement in number and quality of in vitro produced blastocysts. Thus, Nelore females were divided into two groups of 15 animals to receive supplementation with or without sunflower seed for 57 days. Females underwent follicular aspiration and the oocytes were subjected to in vitro embryo production. There was no difference (p > .1) between control group and group supplemented with sunflower seed on the number of displayed follicles; number of aspired oocytes; recovery rate; cleavage rate; number of embryos; number of blastocysts; embryos number of grades I and II; plasma concentrations of total cholesterol, triglycerides; HDL and LDL. Therefore, sunflower seed supplementation in oocyte donors did not increase the number and quality of oocytes, cleavage rates and the number and quality of blastocysts produced in vitro.

Impact of estradiol cypionate prior to TAI and progesterone supplementation at initial diestrus on ovarian and fertility responses in beef cows

In cattle, early diestrus progesterone (P4) supplementation modulates endometrial function to exert pro- and anti-pregnancy establishment effects; specifically, P4 stimulates conceptus growth, but also induces early onset of luteolysis. This paradoxical effect is frequently related to the inconsistent fertility outcomes that result from P4 supplementation experiments. Aim was to investigate the impact of exogenous estradiol (E2) treatment at the end of timed fixed AI (TAI) on frequency of early luteolysis and pregnancy of beef cows supplemented with P4. Ovulations (D0 of study) of suckled multiparous (n = 643) and primiparous (n = 193) Nelore cows (Bos indicus) were synchronized with an E2/P4-based protocol for TAI and assigned to receive 1.0 mg of estradiol cypionate (CP) or nothing (NoCP) on D-2 and 150 mg of injectable long-acting P4 (iP4) or Placebo (NoiP4) on D4 on a 2 × 2 factorial arrangement. On D15, the iP4 supplementation increased (P < 0.05) the frequency of early luteolysis (NoCP + iP4: 26.0%; [13/50] vs. NoCP: 8.0% [4/50]), but CP prevented this effect (CP + iP4: 8.3% [4/48] and CP: 6.4% [3/47]). The CP improved pregnancy/AI (P/AI) of multiparous (CP: 51.6% [165/320] and NoCP: 35.0% [113/323]; P < 0.001) and primiparous cows (CP: 40.4% [40/99] and NoCP: 24.5% [23/94], P < 0.05), regardless of iP4 treatment. The iP4 supplementation affected P/AI of CP and NoCP treated cows according to follicle size at TAI. For the CP treated cows, the iP4 supplementation improved P/AI of sub-populations of cows with follicles <12.35 mm (42.0% [34/81] vs. 53.1% [34/64]), while for NoCP treated cows, the improvements occurred in subpopulations of cows with follicles ≥12.35 mm (46.1% [35/76] vs. 58.7% [37/63]). In conclusion, strategies associating E2 and P4 supplementation decrease the incidence of early onset of luteolysis and improve P/AI of suckled beef cows with smaller follicles.

Cytobrush: A tool for sequential evaluation of gene expression in bovine endometrium

Aims were to (i) compare specific transcript abundance between endometrial samples collected by transcervical biopsy and cytobrush and (ii) measure the abundance of endometrial transcripts involved in PGF2α synthesis in samples collected by cytobrush. In Experiment 1, endometrial samples were taken transcervically by cytobrush and biopsy 10 days after ovulation. Compared to biopsy samples, abundance of transcripts for MSTN, AKR1C4 and PGR was similar, VIM, FLT1 and PTGES was lower (p < .05) and KRT18 and CD3D was greater in cytobrush samples (p < .05). Thus, there was an enrichment of epithelial and immune cells in the cytobrush samples. In Experiment 2, endometrial samples were collected by cytobrush on days 10, 13, 16 and 19 after ovulation. Abundance of PGR2 mRNA was maximum on day 10 then decreased (p < .05). Abundance of ESR1 decreased gradually from day 10 to day 16 then increased again on day 19. The greatest abundance of OXTR was noted on day 19. The sequential alterations in abundance of these transcripts are consistent with the release of PGF2α associated with luteolysis. In summary, cytobrush sampling provides representative, physiologically relevant samples of the luminal epithelium in cattle.

Endometrial transcriptional profiling of a bovine fertility model by Next-Generation Sequencing

Studying the multitude of molecular networks and pathways that are potentially involved in a complex trait such as fertility requires an equally complex and broad strategy. Here, we used Next-Generation Sequencing for the characterization of the transcriptional signature of the bovine endometrial tissue. Periovulatory endocrine environments were manipulated to generate two distinctly different fertility phenotypes. Cycling, non-lactating, multiparous Nelore cows were manipulated to ovulate larger (> 13 mm; LF group; high fertility phenotype) or smaller (< 12 mm; SF group) follicles. As a result, greater proestrus estrogen concentrations, corpora lutea and early diestrus progesterone concentrations were also observed in LF group in comparison to SF group. Endometrial cell proliferation was estimated by the protein marker MKI67 on tissues collected 4 (D4) and 7 (D7) days after induction of ovulation. Total RNA extracts from D7 were sequenced and compared according to the transcriptional profile of each experimental group (LF versus SF). Functional enrichment analysis revealed that LF and SF endometria were asynchronous in regards to their phenotype manifestation. Major findings indicated an LF endometrium that was switching phenotypes earlier than the SF one. More specifically, a proliferating SF endometrium was observed on D7, whereas the LF tissue, which expressed a proliferative phenotype earlier at D4, seemed to have already shifted towards a biosynthetically and metabolically active endometrium on D7. Data on MKI67 support the transcriptomic results. RNA-Seq-derived transcriptional profile of the endometrial tissue indicated a temporal effect of the periovulatory endocrine environment, suggesting that the moment of the endometrial exposure to the ovarian steroids, E2 and P4, regulates the timing of phenotype manifestation. Gene expression profiling revealed molecules that may be targeted to elucidate ovarian steroid-dependent mechanisms that regulate endometrial tissue receptivity. Data was deposited in the SRA database from NCBI (SRA Experiment SRP051330) and are associated with the Bio-Project (PRJNA270391). An overview of the gene expression data has been deposited in NCBI's Gene Expression Omnibus (GEO) and is accessible through GEO Series accession number GSE65450. Further assessment of the data in combination with other data sets exploring the transcriptional profile of the endometrial tissue during early diestrus may potentially identify novel molecular mechanisms and/or markers of the uterine receptivity.

Improved fertility in suckled beef cows ovulating large follicles or supplemented with long-acting progesterone after timed-AI

We aimed to evaluate the effects and the interaction of size of the preovulatory follicle (POF) and long-acting progesterone (P4) supplementation after timed-AI on CL function and pregnancy success in beef cows. In experiment 1, ovulations of beef cows were synchronized starting on Day -10, and cows were split to receive sodium cloprostenol (large follicle group; LF; n = 31) or nothing (small follicle group; SF; n = 35). Ovulations were induced on Day 0, and cows were inseminated. Ovulated cows were assigned to receive placebo (LF/control group, n = 14; and SF/control group, n = 9) or 150 mg of long-acting P4 on Day 4.5 (LF/P4 group, n = 13; and SF/P4 group, n = 12). Diameter of POF, blood flow in POF wall, ovulation rate, and size and vascularization of CL were greater (P < 0.05) in LF group. In experiments 2 (unknown cyclic status) and 4 (noncycling), ovulations were synchronized, and beef cows received placebo or 150 mg of long-acting P4 on Day 4 after timed-artificial insemination. In experiment 2, pregnancy/AI (P/AI) did not differ (P > 0.1) between P4-treated (53.2%; 209/393) and control cows (56.2%; 219/390), but P/AI was greater in cows with a CL < 0.9 cm(2) on Day 4 that were P4-treated (57.9%, 22/38) versus placebo-treated (40.4%, 21/52; P < 0.05). In Experiment 4, P/AI was greater (P < 0.05) in P4-treated cows (55.6%, 105/189 vs. 46.0%, 86/187). In Experiment 3, cyclic-suckled beef cows were treated as described in Experiment 1 to generate animals with small (SF; n = 111) or large POF (LF; n = 109), and subdivided to receive placebo or P4 on Day 4. POF size, ovulation rate, CL area, and P/AI were greater (P < 0.007) in the LF group. Pregnancy/AI in ovulated cows were lower (P = 0.05) in the SF/control group (41.5%, 17/41) compared to LF/control group (62%, 31/50) and were similar for the SF/P4 group (55.6%, 25/45) and LF/P4 group (57%, 28/49) compared to others. In summary, smaller and less vascularized POF results in less functional CL and reduces ovulatory rate and P/AI in cyclic beef cows; the long-acting P4 injection on Day 4 after timed-artificial insemination may attenuate the negative effects of small POF/CL; and postovulatory P4 supplementation improved fertility in anestrous beef cattle.

The Receptive Endometrial Transcriptomic Signature Indicates an Earlier Shift from Proliferation to Metabolism at Early Diestrus in the Cow

This study aimed to characterize the endometrial transcriptome and functional pathways overrepresented in the endometrium of cows treated to ovulate larger (≥13 mm) versus smaller (≤12 mm) follicles. Nelore cows were presynchronized prior to receiving cloprostenol (large follicle [LF] group) or not (small follicle [SF] group), along with a progesterone (P4) device on Day (D) -10. Devices were withdrawn and cloprostenol administered 42-60 h (LF) or 30-36 h (SF) before GnRH agonist treatment (D0). Tissues were collected on D4 (experiment [Exp.] 1; n = 24) or D7 (Exp. 2; n = 60). Endometrial transcriptome was obtained by RNA-Seq, whereas proliferation and apoptosis were assessed by immunohistochemistry. Overall, LF cows developed larger follicles and corpora lutea, and produced greater amounts of estradiol (D-1, Exp. 1, SF: 0.7 ± 0.2; LF: 2.4 ± 0.2 pg/ml; D-1, Exp. 2, SF: 0.5 ± 0.1; LF: 2.3 ± 0.6 pg/ml) and P4 (D4, Exp. 1, SF: 0.8 ± 0.1; LF: 1.4 ± 0.2 ng/ml; D7, Exp. 2, SF: 2.5 ± 0.4; LF: 3.7 ± 0.4 ng/ml). Functional enrichment indicated that biosynthetic and metabolic processes were enriched in LF endometrium, whereas SF endometrium transcriptome was biased toward cell proliferation. Data also suggested reorganization of the extracellular matrix toward a proliferation-permissive phenotype in SF endometrium. LF endometrium showed an earlier onset of proliferative activity, whereas SF endometrium expressed a delayed increase in glandular epithelium proliferation. In conclusion, the periovulatory endocrine milieu regulates bovine endometrial transcriptome and seems to determine the transition from a proliferation-permissive to a biosynthetic and metabolically active endometrial phenotype, which may be associated with the preparation of an optimally receptive uterine environment.

98 UTERINE INVOLUTION AND VASCULAR PERFUSION DURING EARLY POSTPARTUM IN MARES

In horses, a rapid involution of the uterus occurs right after parturition, allowing the reestablishment of a favourable uterine environment for embryo development. However, limited evidence is found regarding the vascular events during puerperal period in mares. We aimed to evaluate the morphological (size of uterus and uterine fluid content) and haemodynamic (endometrial and mesometrial vascular perfusion) characteristics of the uterine involution process. Mares (n = 10) were evaluated by transrectal ultrasonography from the first day postpartum (d1) to the sixteenth day after first ovulation (D0 = ovulation). For ultrasound exams, a duplex B-mode and Doppler ultrasound instrument (M5 VET; Mindray Medical International Limited, China) equipped with a transrectal transducer was used. The previously pregnant (PH) and nonpregnant (NPH) horns were individually evaluated. Data were analysed for the main effects of horns (PH and NPH), day, and their interaction, using the PROC MIXED procedure of SAS software (9.3 version; SAS Institute Inc., Cary, NC, USA). Discrete variables were analysed by ANOVA. A reduction (P < 0.05) in the uterine diameter was observed during the first 7 days postpartum, but the rate of uterine involution (decrease in uterine size) decreased thereafter. The involution was complete around the d21 for the NPH and around d24 for the PH. Presence of uterine luminal fluid (mm) was increased between d1 (no fluid) and d2 (31.41 ± 2.88) postpartum, followed by a decrease between d4 (30.43 ± 4.52) and d7 (10.20 ± 1.76). No fluid was observed after d16 postpartum or after the third day postovulation (D3). For endometrial and mesometrial vascular perfusion, only a day effect (P < 0.05) was observed. An increase in the endometrial and mesometrial vascularization was detected, respectively, between d1 and d4, and between d1 and d2. Vascular perfusion did not differ after d4 for endometrial tissue, whereas it was reduced (P < 0.05) between d2 and d10 for mesometrium. For the vascular perfusion after ovulation, an increase (P < 0.05) from D0 to D5, followed by a decrease (P < 0.05) between D5 and D11 and an increase (P < 0.05) between D11 and D14 was observed in the endometrial and mesometrial tissues. The profile of the vascular perfusion in endometrium and mesometrium after first ovulation postpartum is similar to that observed during oestrous cycles and early pregnancy, indicating a return of the uterus to the pre-pregnant uterine characteristics in mares.Research was supported by FAPESP process no. 2010/10692-9 and CNPq process no. 135954/2011-8.

175 FOLLICULAR DEVELOPMENT AND OVARIAN BLOOD FLOW IN MARES WITH EARLY OR LATE OVULATION POSTPARTUM

The postpartum period is characterised by the rapid uterine involution process and return of ovarian activity (foal heat), resulting in a fertile oestrus in most of the mares. However, the follicular development and selection processes during this period are not completely known in horses. We aimed to study the characteristics of follicular growth and vascular perfusion in the ovary during the early postpartum period in mares that demonstrated oestrous behaviour and had early (<10 days) or late (≥10 days) ovulation. Ten mares were scanned daily from the first day postpartum (Day 1) until the day of the first postpartum ovulation (Day 0). The animals were split in the early (n = 3) and late (n = 7) ovulation groups (averaged interval between parturition and ovulation: 8.0 ± 0.0 and 14.7 ± 1.2 days, respectively). For ultrasound exams a Duplex B-mode and colour Doppler instrument (M5VET®, Mindray, Shenzhen, China) was used with a multifrequency linear probe. Data were analysed for the main effects of group, day, and their interaction using the PROC MIXED procedure of SAS software (version 9.3, SAS Institute Inc., Cary, NC, USA). For the follicular growth, no difference (P > 0.05) was detected between the groups when the data were analysed for the days relative to ovulation (from Day 7 to Day 1). However, the dominant follicle was larger (P < 0.05) in the early-ovulated group (37.2 ± 1.6 v. 21.9 ± 1.1) in all days during early postpartum (Day 1 to Day 7). The number of follicles with >25 mm diameter was also greater (P < 0.05) in the early-ovulated group (1.1 ± 0.1 v. 0.1 ± 0.1) during the first 3 days postpartum. In addition, the late-ovulated mares showed greater number of follicles with 20–25 mm during Day 4 to Day 7 (2.0 ± 0.2 v. 0.7 ± 0.1). For the blood flow characteristics, no difference (P > 0.05) was detected in the coloured signals of blood flows in the follicular wall of the dominant follicle or in the ovarian pedicle ipsilateral to the largest follicle. Therefore, the characteristics of the follicle growth on the preceding days of ovulation were similar between the early- and late-ovulated mares and consistent with the follicular dynamics expected in non-pregnant and non-lactating mares. However, when the data were analysed for the days relative to parturition, a greater follicle development was present in mares that ovulate earlier during the postpartum period (<10 days). In conclusion, the results suggest that important events may occur previous to the parturition, resulting in an early follicle development, mainly in those mares that show heat signs and ovulate within 10 days postpartum. Research was supported by FAPESP process number 2010/10692-9 and CNPq process number 135954/2011-8.

201 USING THE TRANSCRIPTOME SIGNATURE TO PREDICT PREGNANCY SUCCESS IN BEEF COWS AT 6 DAYS AFTER ARTIFICIAL INSEMINATION

Pregnancy success is critical to the profitability of cattle operations. Attempts to reduce high rates of early embryonic loss mainly focus on the critical phase of embryo recognition by maternal tissue. However, the molecular events driving the uterine tissue toward a favourable stage, facilitating the maternal receptivity, are poorly understood. This study aimed to characterise the endometrial transcriptome profiles of pregnant versus nonpregnant beef cows during early pregnancy and attempted to define a potential set of marker genes that can be valuable for predicting pregnancy outcome. Therefore, pluriparous, cyclic Nellore (Bos indicus) cows were synchronized (n = 51) and artificially inseminated (n = 36) at detected oestrus using semen from a single high-fertility bull. Six days after AI (Day 6), jugular blood samples and an endometrial biopsy from the uterine horn contralateral to the ovary containing the CL were collected. Pregnancy diagnosis was performed by ultrasonography on Days 22 and 30. Based on pregnancy outcome, samples were retrospectively allocated to the following groups: pregnant (P; n = 6) and nonpregnant (NP; n = 5). Both groups had similar plasma progesterone concentrations on Day 6 (less than 1 ng mL–1 between lowest and greatest concentrations). Endometrial biopsies were submitted to RNA-Seq analysis in an Illumina single flow cell line (Illumina Inc., San Diego, CA). The 272 685 768 million filtered reads were mapped to the Bos taurus UMD3.1 reference genome and 14 654 genes were effectively analysed for differential expression between groups. Transcriptome data showed that 216 genes are differently expressed when comparing P v. NP endometrial tissue (adjusted P < 0.1). More specifically, 36 genes showed a significantly up-regulated expression for pregnant cows and 180 are up-regulated for non-pregant cows. Functional enrichment and pathway analyses revealed enriched expression of genes associated with extracellular matrix remodelling in NP cows and nucleotide binding, microsome, and vesicular fraction in P cows. From the 40 top-ranked genes, six that were down- and three that were up-regulated in pregnant cows were further analysed by qRT–PCR in an additional 26 cows. Subsequent quantitative expression data were evaluated using multivariate statistics. Both principal component analysis (PCA; R2 = 0.82 and Q2 = 0.40) and orthogonal projections to latent structures analysis (OPLS), using pregnancy as the dependent variable (R2Y = 0.95 and Q2 = 0.86), efficiently separated P from NP animals. In conclusion, this study characterizes a unique set of genes, expressed in the endometrium as early as 6 days after AI, that indicate a receptive state leading to pregnancy success. Furthermore, expression of such genes can be used as potential markers to efficiently predict pregnancy success.

101 SUPPLEMENTATION WITH SUNFLOWER SEED ALTERS THE ENDOMETRIAL LIPID COMPOSITION IN BEEF COWS

Embryo death between 15 and 19 days of pregnancy is caused by the increase in the release of endometrial prostaglandin F2α (PGF2α) involved in the luteolysis process in cattle. Compounds rich in linoleic acid, such as sunflower seeds, provide lipid changes in the endometrium, and may be involved in the ability of PGF2α biosynthesis. Previous studies observed that the conception rate increased in Nelore cows supplemented with sunflower seed for 22 days from the timed AI (66.7% v. 46.3%; Peres et al. 2008, Acta Sci. Vet. 36, 639) and in crossbred heifers submitted to timed embryo transfer (55.66% v. 36.94%; Membrive et al. 2013 Acta Sci. Vet. 36, 603). We aimed to test the hypothesis that supplementation with sunflower seed promotes endometrial changes in lipid composition. Thus, we compared the composition of fatty acids in endometrial tissue in cows supplemented or not with sunflower seed. Nelore (n = 30) cows received an intravaginal device containing progesterone (1 g; DIB, Syntex Biochemistry & Pharmaceutical Industries SA, Buenos Aires, Argentina) associated with an im injection of oestradiol benzoate (2 mg; Benzoate HC, Hertape Calier Animal Health SA, Juatuba, MG, Brazil). The devices were removed after 8 days, when cows were treated im with cloprostenol sodium (2 mg; Sincrocio®, Ourofino Animal Health Ltd., Cravinhos, SP, Brazil), oestradiol cypionate (0.5 mg; ECP®, Zoetis Ltda., São Paulo, Brazil) and eCG (300 IU; Folligon®, Intervet Veterinary Ltda., Cotia, Brazil). Two days after removal of the device, females were assigned into 6 groups to receive 1.7 kg/animal/day of 40% soybean meal, 44% crude protein (CP) + 60% sunflower seed for 6 (n = 4), 14 (n = 5) and 22 days (n = 6), or 53% soybean meal, 44% CP + 47% corn for 6 (n = 4), 14 (n = 5) and 22 days (n = 6). Both diets were formulated with 72% total digestible nutrients and 24% CP. Females were slaughtered 24 h after the end of supplementation and endometrial tissue was isolated and stored at –196°C. The fatty acids in endometrial tissue were assessed by gas chromatography. Data were analysed by SAS Proc GLIMMIX (SAS Institute Inc., Cary, NC, USA). The fatty acid profile (54 compounds) was analysed and 43 fatty acids were present in the endometrial tissue. The lacking fatty acids in endometrial tissue were C4:0, C11:0, C12:1, C: 13:0, C13:0 iso, C13:0 anteiso, C14:0 iso, C15:1, C18:1 trans-16, C18:2 cis-12, trans-10, and C21:0. The fatty acids that showed a higher percentage compared with the Control group were C18:1 trans-10-trans-11-trans-12 and C10:1. The fatty acids that showed low percentage compared with the Control group were C15:0 iso, C20:5, C20:3n-3, C23:0, C24:0, and C22:5. In conclusion, supplementation with sunflower seed promotes changes in the endometrial lipid profile that may reduce the pregnancy loss in beef cows. Research supported by FAPESP, FUNDUNESP, and Santa Encarnação Farm.

11 FERTILITY RESPONSE IN SUCKLED BEEF COWS SUPPLEMENTED WITH LONG-ACTING PROGESTERONE AFTER TIMED ARTIFICIAL INSEMINATION

Corpus luteum (CL) and progesterone (P4) secretion are affected by preovulatory follicle (POF) size. Increased circulating P4 during early diestrus has a positive effect on embryo development in beef cattle. However, the combined effects of the POF size and P4 supplementation during early diestrus on fertility of beef cows are not known. The objective was to evaluate the effects of POF size and supplementation of long-acting P4 after timed-AI on pregnancy rates (P/AI). Suckled Nelore cows (n = 596) were evaluated twice by transrectal Doppler ultrasonography (US) 10 days apart to detect the cyclic status. In Study 1, anestrous cows (absence of CL on both exams) received an intravaginal P4 device and an oestradiol benzoate (EB) injection on Day –10 (day of the second US). Devices were removed and sodium cloprostenol [prostaglandin F2α (PGF2α)], oestradiol cypionate, and eCG were given on Day –2. Cows were timed-AI on Day 0 and assigned to receive placebo (control group, n = 187) or 150 mg of long-acting P4 on Day 4 (P4 group, n = 189). In Study 2, cyclic cows (presence of CL) received a PGF2α injection on Day –20 (first US). Cows with a new CL on Day –10 received an intravaginal P4 device and an injection of EB and were split to receive an injection of PGF2α [large follicle (LF); n = 109] or not [small follicle (SF); n = 111]. Devices were removed and PGF2α was injected on Day –2. Ovulation was induced with buserelin acetate, and cows were timed-AI on Day 0 and split to receive placebo (LF/control group, n = 55, and SF/control group, n = 55) or 150 mg of long-acting P4 on Day 4 (LF/P4 group, n = 56, and SF/P4 group, n = 54). Ultrasonographic scanning was done on Days 0, 4, and between 35 and 40 to detect the POF and CL sizes and P/AI, respectively. Data were analysed using PROC GLIMMIX (SAS Institute Inc., Cary, NC). In anestrous cows, P/AI was reduced in POF with <11 mm. The P/AI was greater in the P4-treated group than in the control group for all cows (55.6% v. 46.0%; P = 0.05) and for ovulated cows (59%, 105/178 v. 49%, 86/173; P = 0.08). For cyclic cows, POF size (mm) on Day 0 (13.5 ± 0.3 v. 11.2 ± 0.2), ovulation rate (90% v. 77%), and CL area (cm2) on Day 4 (1.46 ± 0.05 v. 1.25 ± 0.05) were greater (P < 0.007) in the LF group than in the SF group. There was a main effect of follicle group on P/AI (54%, LF group v. 38%, SF group; P < 0.01). Moreover, P/AI were greater (P < 0.05) in the LF/control (56%) and LF/P4 (52%) groups than in the SF/control group (31%), whereas no difference was detected between the SF/P4 group (45%) and the other groups. Among cows that ovulated, P/AI was lower (P = 0.05) in the SF/control group (41%, 17/41) compared with the LF/control group (62%, 31/50) and were similar for the SF/P4 group (56%, 25/45) and LF/P4 group (57%, 28/49) compared with others. We suggest that P4-stimulated embryotrophic effects improved fertility in anestrous beef cows supplemented with long-acting P4 on Day 4 after timed-AI. Also, the presence of a functional CL during follicle growth results in smaller POF and CL and reduces the ovulatory and P/AI rates in cyclic cows. Post-AI P4 supplementation may attenuate the negative effects of small POF/CL. Research was supported by CNPq, FAPESP, Ouro Fino Agronegócio, and Innovare.

106 THE RECEPTIVE BEEF COW ENDOMETRIUM: POTENTIAL KEY FEATURES FAVOURING THE COMMUNICATION BETWEEN EMBRYONIC AND MATERNAL TISSUES

A receptive state of the endometrium is crucial for proper communication with the pre-implantation embryo and, thereby, a perquisite for a successful pregnancy. Both reduction of transmembrane mucin and initiation of apoptotic events have been proposed as key features prompting embryo/endometrial cell interaction and facilitating maternal receptivity of the murine and human embryo. In beef cows, however, the signature for receptivity needs to be elucidated. Therefore, we aimed to characterise “receptive” versus “refractory” endometrial tissues with the focus on (1) transcription profiles related to mucin, apoptosis and proliferative pathways, and 2) phenotypic features; that is, epithelial transmembrane mucin and apoptotic cell rates (ACR). Using a bovine model, preovulatory follicle growth was manipulated to produce 2 groups: cows with larger preovulatory follicle, longer proestrus, and higher receptivity (LF-LCL) versus cows with smaller preovulatory follicle, shorter proestrus, and lower receptivity (SF-SCL). Seven days post-induced ovulation, endometrium was collected. Transcriptome profiles of endometrial tissue (n = 3/group) were determined using Illumina RNA sequencing analyses. In addition, paraffin embedded endometrial samples (n = 6/group) were stained with Alcian Blue for semiquantitative analyses of mucin staining intensity and treated with antibodies against activated Casp3 to determine ACR. RNA-seq data showed that cell surface MUC1 gene expression was drastically reduced (fold-change –3.33) in LF-LCL tissue (P < 0.05). In contrast, the LF-LCL endometrial tissue displayed an up-regulated expression of genes involved in apoptosis pathways, such as Casp9, CRADD, DAPL1 (fold-change 1.80, 2.10, and 3.60, respectively; P < 0.05). Moreover, the expression of genes related to proliferation, such as MYC and NOV, was significantly down-regulated in LF-LCL endometrial tissue (fold-change –2.2 and –6.3, respectively; P < 0.01). Histology of endometrial samples revealed that the signal for transmembrane, anti-adhesive, mucin at the LF-LCL epithelium was consistently low, whereas the SF-SCL tissue group displayed variable amounts of transmembrane mucin at the apical epithelial boarder. Immunohistochemistry showed that gland cells from LF-LCL endometrial tissue displayed a significantly higher ACR compared with gland cells of the SF-SCL tissue (29.6 ± 1.52% v. 11.9 ± 1.26%; P < 0.05). In the surface epithelium and the stromal tissue, Casp3 positive cells were rare and ACR was similar between groups. In conclusion, a down-regulated expression of the transmembrane mucin might indicate a receptive condition of the endometrium. Furthermore, the prominent apoptotic characteristics in the LF-LCL tissue suggest that the receptive endometrium must surpass the proliferative status in order to differentiate to more specialised functions, such as embryotrophy.

102 SUPPLEMENTATION WITH ESTRADIOL CYPIONATE AT THE ONSET OF A SYNCHRONIZED PROESTRUS ALTERS THE UTERINE GENE EXPRESSION OF SUCKLED ANESTROUS BEEF COWS

The present study evaluated the effect of oestradiol cypionate (ECP) supplementation at the onset of a proestrus [i.e. at progesterone (P4) device removal of the synchronization of ovulation protocol] on the global endometrial gene expression of suckled anestrous beef cows. A total of 12 suckled cows presenting absence of corpus luteum detected by ultrasound received 2 mg of oestradiol benzoate IM and an intravaginal P4 device. Eight days later, P4 devices were removed, and the cows received 500 mg of sodium cloprostenol IM. Cows were blocked according to body condition score and diameter of largest follicle (LF) at P4 device removal and were randomly assigned to receive an IM treatment with 1 mg of ECP (ECP, n = 6) or not (CON, n = 6) at the P4 device removal. All cows received 10 μg of buserelin acetate 48 h after P4 device removal and were timed AI immediately after. Cows presenting a new corpus luteum formed 6 days after the gonadotropin-releasing hormone treatment had an endometrial fragment collected by transcervical biopsy. RNA-Seq analysis was performed and the transcriptome profile was obtained. The significance of differential gene expression was assessed with the package DESEqn 2 v.1.2.10 and the differential expression estimation was based on the GLM followed by the Wald test. The significance threshold was established as an FDR- Benjamini-Hochberg-adjusted P-value of <0.1. The integrated analysis was performed using DAVID database. In total, 135 transcripts were differentially expressed between ECP and CON groups, of which 73 genes were up-regulated by ECP supplementation and 62 genes were up-regulated in the CON cows. Two pathways were overrepresented by the ECP-induced transcripts: pathways in cancer (n = 5 genes) and small cell lung cancer (n = 3 genes). On the other hand, ECP-inhibited transcripts indicated the enrichment of 3 pathways: Parkinson's disease (n = 3 genes), oxidative phosphorylation (n = 3 genes), and Alzheimer's disease (n = 3 genes). More specifically, ECP-induced transcripts associated with pathways in cancer [gene symbol (fold change); respectively] were LAMC3 (1.55), PTCH1 (1.51), PTCH2 (1.52), PIK3R3 (1.22), and PIAS1 (1.18), whereas ECP-inhibited transcripts associated with oxidative phosphorylation were ATP5F1 (1.18), ATP5J (1.24), and NDUFB3 (1.37). Therefore, ECP supplementation at onset of the synchronized proestrous slightly alters the uterine transcriptome. The enriched pathways affected by the ECP supplementation described in this work need to be studied more but these results show candidate pathways that can be associated with uterine environment and receptivity and with possible regulation by oestradiol supplementation given at the onset of the proestrous.

Modulation of periovulatory endocrine profiles in beef cows: consequences for endometrial glucose transporters and uterine fluid glucose levels

In beef cattle, proestrus estradiol and subsequent progesterone (P4) concentrations can regulate the endometrial characteristics and thereby determine maternal receptivity toward the embryo. However, the underlying mechanisms linking periovulatory endocrine profiles to receptivity, which is crucial to obtain pregnancy, need to be elucidated. We hypothesized that the size of the preovulatory follicle (POF) and subsequent circulating P4 concentrations, during early diestrus, modulate endometrial levels of glucose transporter transcripts and proteins, and subsequently affect the luminal glucose availability in the uterus. Therefore, follicle growth of Nelore cows was manipulated, and cows were assigned to 2 experimental groups: (1) large follicle and large corpus luteum (LF-LCL) group with a large POF and corpus luteum (CL); and (2) small follicle and small corpus luteum (SF-SCL) group with a small POF and CL. At day 7 post gonadotropin-releasing hormone induced ovulation (gonadotropin-releasing hormone treatment = day 0), animals were slaughtered (n = 18 per group), and uterine tissues and washings were collected for characterization of glucose transporters and glucose levels, respectively. The diameter of POF was larger (P < 0.05) in the LF-LCL cows compared with their SF-SCL counterparts (12.8 ± 0.4 vs 11.1 ± 0.4 mm). Furthermore, CL size (17.49 ± 0.88 vs 14.48 ± 0.52 mm) and circulating P4 concentrations at day 7 (4.5 ± 1.0 vs 3.3 ± 1.1 ng/mL, P < 0.05) were significantly higher in the LF-LCL cows compared with the SF-SCL cows. No differences (P > 0.05) were detected in gene expression patterns of SLC2A1, SLC2A3, SLC2A4, SLC2A5, SLC5A1, ATP1A2, ATP1B2, and SLC37A4. However, the protein abundance of endometrial SLC2A1was increased in the LF-LCL group compared with the SF-SCL group (P < 0.05). SLC2A1 and SLC2A4 protein products were mainly identified at the endometrial luminal and glandular epithelium membranes as well as in the endometrial stroma. Glucose concentrations in uterine washings were similar between groups. In conclusion, we provided information on the potential link between endocrine profiles and glucose transport pathways in the bovine endometrium. More specifically, our data reveal that the size of the POF, and subsequent P4 concentrations, do not functionally affect the main endometrial glucose transporter pathways or uterine fluid glucose concentrations during diestrus.

Use of cholesterol-loaded cyclodextrin in donkey semen cryopreservation improves sperm viability but results in low fertility in mares

The use of cholesterol-loaded cyclodextrin (CLC) on semen cryopreservation has been related with better sperm viability in several species; however, the effect on fertility is not known in donkey semen. Ejaculates (n = 25) from five donkeys were diluted in S-MEDIUM with 0, 1, 2 or 3 mg of CLC/120 × 10(6) spermatozoa. Semen was frozen, and thawed samples were evaluated by computer-assisted sperm analyser system (CASA), supravital test, hyposmotic swelling test and fluorescent dyes to assess the integrity of sperm membranes. Mares (n = 60) were inseminated with frozen-thawed semen treated with the doses of 0 or 1 mg CLC. Percentages of sperm with progressive motility and with functional plasma membrane were greater (p < 0.05) in the CLC-treated groups than in the control. Percentages of intact plasma membrane and intact plasma membrane and acrosome detected by fluorescent dyes were also greater (p < 0.05) in CLC-treated groups. Although no difference (p > 0.05) in conception rates was detected between groups (control, 3/30, 10%; CLC-treated, 1/30, 3.3%), fertility was low for artificial insemination programs in mares. Therefore, we firstly demonstrated that frozen semen treated with CLC in S-MEDIA extender before freezing improves the in vitro sperm viability, but semen treated or not with CLC in S-MEDIUM extender results in a very low conception rate in mares inseminated with thawed donkey semen.

Impact of probing the reproductive tract during early pregnancy on fertility of beef cows

This short communication reports the impact of endometrial biopsies, uterine flushings and follicular fluid aspiration procedures at day 6 post artificial insemination (AI) on pregnancy rates. In Experiment 1, cows were timed AI (TAI) and assigned to the following treatment groups: control (n = 37), uterine flushing (n = 35) and endometrial biopsy (n = 38). On day 30 post AI, pregnancy rates were 40.5%, 33% and 28.5%, respectively (p > 0.1). Pregnancy rate on day 60 was lower (p < 0.004) in flushed cows than in the controls. In Experiment 2, oestrus was detected and cows were assigned to flushing (n = 32) or biopsy (n = 33) treatments 6 days after AI, which resulted in pregnancy rates of 31% and 36%, respectively (p > 0.1). In Experiment 3, cows were, 6 days after TAI, randomly assigned to the following treatments: control (n = 84) or aspiration of the largest follicle (n = 73). Pregnancy rates on day 30 post AI were 63.5% for the control group and 53% for the aspirated group (p > 0.1). In conclusion, uterine flushing and endometrial biopsy negatively affect pregnancy rates, but neither procedure can be considered to be incompatible with pregnancy maintenance. Follicular aspiration during pregnancy does not interact with pregnancy success. The amount and quality of samples obtained are compatible with the use of cellular and molecular analysis of uterine variables from cows that failed or succeeded on maintaining pregnancy.

11 STRATEGIES TO MODULATE THE PERI-OVULATORY ENDOCRINE MILIEU BY CONTROLLING PROGESTERONE CONCENTRATIONS PRE- AND POST-INSEMINATION IN BEEF COWS

Recent evidence indicates that progesterone (P4) secretion from corpus luteum (CL) is affected by preovulatory follicle (POF) size and that increased circulating P4 during early diestrus has a positive effect on embryo development and pregnancy rates in cattle. Despite the embryotrophic effects, early administration of P4 may impair CL growth and anticipates luteolysis. Owing to develop favourable peri-ovulatory endocrine milieus to pregnancy success, we evaluated in beef cows (1) the effect of CL presence during dominant follicle growth on follicular vascularization, size and ovulation rate and (2) the effects of POF size and supplementation of long-acting P4 post-AI on CL development and regression. Sixty-six Nelore cows received an intravaginal P4 device and an injection of oestradiol benzoate on Day 10 (5–10 days post-oestrus), and were split to receive sodium cloprostenol [prostaglandin F2α (PGF2); large follicle (LF); n = 31) or not [small follicle (SF); n = 35]. Devices were removed and PGF2 was injected on Day 1.75. Ovulation was induced with a gonadotropin-releasing hormone (GnRH; buserelin acetate) on Day 0. Cows were inseminated twice on Days 0.5 and 1. Cows that ovulated were assigned to receive placebo (LF/control group, n = 14; and SF/control group, n = 9) or 150 mg of long-acting P4 on D4.5 (LF/P4 group, n = 13; and SF/P4 group, n = 12). Colour-Doppler ultrasound scanning was done on Days 10, 6, 2, 0.5, 1, 1.5, 4.5, 7.5, and 15.5. Structural luteolysis was detected by 25% decrease in CL area and 50% in luteal blood flow of subsequent scanning. Data were analysed for the main effects of POF size and supplementation and their interaction using the PROC MIXED procedure of SAS (SAS Institue Inc., Cary, NC, USA). Follicle diameter (mm) on Day 2 (11.4 ± 0.4 v. 8.4 ± 0.3) and POF (14.1 ± 0.3 v. 12.5 ± 0.3) were greater (P < 0.05) in LF group. Percentage of luteal blood flow in follicle wall was greater (P < 0.05) on Day 0.5 (33.9 ± 3.4 v. 22.8 ± 3.6) and 1 (48.9 ± 4.8 v. 28.3 ± 4.3) in the LF group. Ovulation rate was lower (P < 0.05) in the SF group (60%, 21/35) than in the LF group (90%, 28/31), suggesting that a functional CL during dominant follicle growth is less favourable to pregnancy success due to 30% reduction in fertilizing potential of non-ovulated follicles. For luteal area (cm2), an effect (P < 0.05) of POF size was detected on Day 4.5 (1.7 ± 0.1 v. 1.3 ± 0.1), 7.5 (2.8 ± 0.2 v. 2.2 ± 0.1), and 15.5 (2.5 ± 0.1 v. 2.2 ± 0.2) in the LF and SF groups, respectively. Luteal blood flow was greater (P < 0.05) in the LF groups (40.4 ± 1.7 and 47.6 ± 3.4) than in the SF groups (35.7 ± 1.5 and 37.9 ± 4.1) on Day 4.5 and 15.5, respectively. This indicates that larger and more vascularized POF may be associated with greater CL vascularization in addition to greater CL size. The frequency of cows with early luteolysis did not differ (P > 0.1) between P4-treated (5/25) and placebo-treated (1/23) cows. We suggest that the P4 supplementation did not severely induce early luteolysis in inseminated cows and that the P4-embryotrophic effects may down-regulate the mechanisms involved in the earlier luteolytic process caused by greater exposure of uterus to P4. Support for this study was provided by the São Paulo Research Foundation (FAPESP, Sao Paulo, Brazil) and Ourofino (Cravinhos, SP, Brazil).

Corpus luteum development and function after supplementation of long-acting progesterone during the early luteal phase in beef cattle

Strategic supplementation of P4 may be used to increase conception rates in cattle, but timing of supplementation in relation to ovulation, mass of supplementary P4 and formulation of the P4-containing supplement has not been determined for beef cattle. Effects of supplementation of long-acting progesterone (P4) on Days 2 or 3 post-ovulation on development, function and regression of corpus luteum (CL) were studied in beef cattle. Cows were synchronized with an oestradiol/P4-based protocol and treated with 150 or 300 mg of long-acting P4 on Day 2 or 3 post-ovulation (6-7 cows/group). Colour-doppler ultrasound scanning and blood sample collection were performed from Day 2-21.5. Plasma P4 concentrations were greater (p < 0.05) from Day 2.5-5.5 in the Day 2-treated groups and from Day 3.5-5.5 in the Day 3-treated cows than in the control group. CL area and blood flow during Day 2-8.5 did not differ (p > 0.05) among groups, suggesting no effect of P4 treatment on luteal development. The frequency of cows that began luteolysis before Day 15 was greater (p < 0.04) in cows treated with 300 mg than in the controls, but there were no differences between non-treated and 150 mg-treated cows. The interval from pre-treatment ovulation to functional and structural luteolysis was shorter (p < 0.01) in the combined P4-treated groups than in the control cows. In conclusion, was showed for the first time that long-acting P4 supplementation on Day 2 or 3 post-ovulation increases P4 concentrations for ≥3 day, has no effect on luteal development, but anticipates the beginning of luteolysis in beef cattle.

173 USE OF CORPUS LUTEUM AREA AS A PREDICTOR OF ONGOING FUNCTIONAL LUTEOLYSIS IN DAIRY HEIFERS

The beginning of functional luteolysis in cattle ranges from Days 16–19 (Day 0 = ovulation). During functional luteolysis, luteal size and blood flow decrease in heifers. The wide range of beginning of luteolysis and the low sensitivity of quick progesterone (P4) assays preclude targeting an individual for a specific period of luteolysis. The present study aimed to evaluate the changes in area and blood flow of corpus luteum (CL) during spontaneous luteolysis and test the hypothesis that a decrease in CL area (cm2) is more efficient in targeting the luteolytic period than using a specific day postovulation. Blood sampling and ultrasound scanning of CL were done every 12 h from Days 13–22 in dairy heifers (Holstein) and was used for a retrospective study (Experiment 1; n = 6 heifers). The P4 concentrations, maximum CL area, and the percentage of CL area with coloured signals of blood flow were centralized to 12-h sample when the end of luteolysis (P4 < 1 ng mL–1) was detected. The percentage decrease in CL area and blood flow between Day 13 and the 12-h sample before the end of luteolysis were calculated. In Experiment 2, a blood sampling and transrectal ultrasonography of CL were performed every 8 h starting on Day 14 to determine the beginning and end of functional luteolysis (n = 20 heifers). The hour of detection of luteolysis was defined as the scan at 8-h intervals when maximum CL area decreased by 25 or 12.5% on Day 14. Based on P4 concentrations, the preluteolytic, luteolytic, and postluteolytic periods in each heifer were identified. The area and blood flow were measured by a duplex B-mode and pulse-wave colour Doppler ultrasound instrument. In Experiment 1, the retrospective study indicated a 25% decrease in CL area and 65% decrease in blood flow 12 h before the end of functional luteolysis. In Experiment 2, the 25% and 12.5% CL area decrease from Day 14 occurred, respectively, on Days 18.1 ± 0.6 and 17.2 ± 0.5 postovulation. The hypothesis that a decrease in CL area is more efficient in targeting ongoing luteolysis than using a specific day postovulation was supported. This was indicated by the greater (P < 0.05) frequency of heifers detected in luteolytic period (12 of 20 heifers) using the criteria of a 12.5% decrease in CL area than using a specific day (Table 1). Using a day postovulation for obtaining heifers in the luteolytic phase was only 0 to 30% effective for targeting luteolysis. In conclusion, the technique of using an ultrasonic 12.5% reduction in CL area is a good tool to detect ongoing luteolysis and may be useful as an experimental design to study factors related to the luteolytic period in cattle. Table 1.Percentage values of heifers in preluteolytic, luteolytic, or postluteolytic periods according to a decrease in CL area criteria or a day postovulation Supported by grants from FAPESP (2012/04004-8 to GP).

177 EFFECTS OF MANIPULATION OF DOMINANT FOLLICLE GROWTH ON SIZE AND FUNCTION OF CORPUS LUTEUM IN BEEF CATTLE

Recent evidence indicates that the progesterone (P4) secretion by corpus luteum (CL) during early diestrus is affected by the size of ovulatory follicle and has a significant impact on embryo development and conception rates. Therefore, strategies to promote the growth of the dominant follicle and/or to stimulate the early development of the CL to increase P4 secretion become an alternative to improve conception rates in the beef cattle industry. Our aim was to study the effect of manipulations of the follicle growth on the diameter of the preovulatory follicle (POF) and subsequent size and function of the CL. Cyclic and non-lactating Nelore cows, pre-synchronized by 2 injections of prostaglandin F2α (PGF) 14 d apart, were manipulated to ovulate large or small follicles according to 3 experiments. In Experiment 1 (Exp. 1; n = 23), animals received a second-use intravaginal P4-releasing device along with an injection of oestradiol benzoate on Day –10 (Day 0 = GnRH injection). Cows were split to receive (large follicle group; LF) or not (small follicle group; SF) a PGF injection on Day –10. Progesterone devices were removed on Day –2.5 in the LF group and on Day –1.5 in the SF group. The PGF was injected at the removal of the P4 device. In Experiment 2 (Exp. 2; n = 38), cows in the LF group had the P4 device removed on Day –2.25 or Day –2, whereas in Experiment 3 (Exp. 3; n = 23), the device (first-use) was removed on Day –1.75 in the LF group and on Day –1.25 in the SF group; the other manipulations were similar to Exp. 1. Data analyses were done only on cows that had a functional CL on Day –10 (P4 > 1 ng mL–1) and that ovulated within 24 and 48 h post-GnRH (Exp. 1, n = 14; Exp. 2, n = 14; Exp. 3, n = 12). The three experiments were successful in inducing POF with different sizes, as indicated by the greater diameter of the POF in the LF group compared with SF in Exp. 1 (12.9 ± 0.5 mm v. 10.7 ± 0.6 mm; P < 0.03), Exp. 2 (14.1 ± 0.6 mm v. 11.7 ± 0.4 mm; P < 0.006), and Exp. 3 (13.8 ± 0.6 mm v. 11.7 ± 0.8 mm; P < 0.06). To evaluate the effect of POF size on size and function of the CL, a factorial analysis was performed by SAS software to test the effect of group, day, and their interaction. For CL volume, an effect of group was detected in Exp. 1 (P < 0.02) and in Exp. 3 (P < 0.06), but not in Exp. 2. The group effect represented greater average CL volume from Day 3 to Day 7 in LF (2.42 ± 0.27 and 2.5 ± 0.39 cm3) than in the SF group (1.39 ± 0.18 and 1.2 ± 0.15 cm3) for Exp. 1 and 3, respectively. For P4 concentrations, a group effect was detected only in Exp. 3 (P < 0.007), as indicated by greater average P4 concentrations from Day 3 to Day 7 in LF (2.31 ± 0.31 ng mL–1) than in the SF group (1.37 ± 0.19 ng mL–1). A day effect was detected in all experiments (P < 0.0001), as indicated by a progressive increase of CL volume and P4 concentrations from Day 3 to Day 7. Manipulation of follicle growth performed in Exp. 3 was the most efficient to modify the function and size of the CL. In conclusion, control of POF size by manipulation of P4 concentrations during growth of the dominant follicle alters the size and function of CL postovulation. CNPq, FAPESP, Ourofino, and PUSP-P.

112 INFLUENCE OF LOW-VOLUME UTERINE FLUSHING ON UTERINE VASCULAR PERFUSION AND ENDOMETRIAL THICKNESS DURING EARLY DIOESTRUS IN BEEF CATTLE

The relevance of the uterine secretions during early embryonic development is due to its role as the only source of nutrients for embryo prior to implantation. Probing of the uterine secretions during early pregnancy without compromising gestation would be an important tool for the identification of fertility markers. Manipulations of the uterus could lead to a local increase in blood flow, which could result from the physical stimulation or tissue damage and inflammation. This study aimed to evaluate the effects of low-volume flushing of the uterine horn contralateral to the ovulation on uterine vascular perfusion and endometrial thickness 6 days after artificial insemination (AI). Transrectal B-mode and color Doppler ultrasonography (MyLab30 Vet Gold; Esaote Healthcare) were used to compare changes on endometrial thickness and uterine vascular perfusion, respectively. Examinations were carried out on 15 Nelore cows just prior to the flushing procedure (0 h), 6 and 24 h later. Cows were inseminated after oestrus detection and uterine flushings were performed 6 d after AI. The uterine horn, contralateral to the corpus luteum, was flushed with 20 mL of PBS using a Foley catheter. After massage of the uterine horn, flushing was collected in a syringe by suction. Vascular perfusion was estimated by scoring the extent of colored areas within the endometrium and mesometrium. Vascular perfusion scores indicated nil (1), minimal (2), intermediate (3), and maximal (4) vascular perfusion. Endometrial thickness was measured by taking the maximum diameter and its perpendicular diameter; these values were summed and then divided by four. Data that were not normally distributed were transformed to natural logarithms or ranks. For each variable, the main effect of side (flushed and nonflushed horns), hour, and their interaction were analyzed using the PROC MIXED procedure from the SAS software. The least significant difference method was used for the comparison of means among hours. An hour effect was detected for endometrial and mesometrial scores of vascular perfusion (Table 1), representing an increased vascular perfusion about 6 h after the flushing procedure and a return to basal perfusion at 24 h. Results indicate that the unilateral flushing procedure increases vascular perfusion on both uterine horns. For endometrial thickness, no effect of side, hour, or their interaction was detected. In conclusion, unilateral low-volume uterine flushing results in a transitory increase in uterine blood flow about 6 h post-flushing. Further studies are needed to evaluate other inflammatory characteristics and the potential effect on pregnancy rate in response to the uterine flushing procedure performed during early pregnancy. Table 1.Scores of endometrial and mesometrial vascular perfusion and endometrial thickness of both uterine horns at the time of uterine flushing (0 h), 6 and 24 h post-flushing (mean ± standard error of the mean)

Inhibition of prostaglandin biosynthesis during postluteolysis and effects on CL regression, prolactin, and ovulation in heifers

The beginning of postluteolysis (progesterone, <1 ng mL(-1)) in heifers was targeted by using 8 h after ultrasonic detection of a 25% decrease in CL area (cm2) and was designated Hour 0. Flunixin meglumine (FM; n=10) to inhibit PGF2α secretion or vehicle (n=9) were given intramuscularly at Hours 0, 4, 8, 16, 24, 32, and 40. The dose of FM was 2.5 mg/kg at each treatment. Blood sampling and measurement of the CL and dominant follicle were done every 8 h beginning 14 days postovulation in each group. Blood samples for detection of pulses of PRL and pulses of a metabolite of PGF2α (PGFM) were obtained every hour for 24 h beginning at Hour 0. Pulse concentrations of both PGFM and PRL were lower in the FM group than in the vehicle group. Concentration of PRL was greatest at the peak of a PGFM pulse. Neither CL area (cm2) nor progesterone concentration differed between groups during Hours 0 to 48 (postluteolysis). Ovulation occurred in nine of nine heifers in the vehicle group and in three of 10 heifers in the FM group. The anovulatory follicles in the FM group grew to 36.2±2.9 mm, and the wall became thickened from apparent luteinization. The hypothesis that PGF2α was involved in the continued P4 decrease and structural CL regression during postluteolysis was not supported. However, the hypotheses that pulses of PGFM and PRL were temporally related and that systemic FM treatment induced an anovulatory follicle were supported.

Induction of PGFM pulses and luteolysis by sequential estradiol-17β treatments in heifers

The effects of sequential induction of PGFM pulses by estradiol-17β (E2) on prominence of PGFM pulses and progesterone (P4) concentration were studied in heifers. Three treatments of vehicle (n = 12) or E2 (n = 12) at doses of 0.05 or 0.1 mg were given at 12-h intervals beginning on Day 15 postovulation. Blood samples were collected every 12 h from Days 13-24 and hourly for 12 h after the first and third treatments. On Day 15, all heifers were in preluteolysis and on Day 16 were in preluteolysis in the vehicle-treated heifers (n = 11) and either preluteolysis (n = 4) or luteolysis (n = 8) in the E2-treated heifers. Peak concentration of induced PGFM pulses during preluteolysis on Day 15 was greater (P < 0.04) than for pulses during preluteolysis on Day 16. The interval from ovulation to the beginning of luteolysis was shorter (P < 0.04) in the E2-treated heifers than in the vehicle-treated heifers. An E2-induced PGFM pulse was less prominent (P < 0.008) in heifers in temporal association with a transient resurgence in P4 than in heifers with a progressive P4 decrease. The hypothesis that repeated E2 exposure stimulates increasing prominence of PGFM pulses was not supported. Instead, repeated exposure reduced the prominence of PGFM pulses, in contrast to the stimulation from the first E2 treatment. Reduced prominence of a PGF(2α) pulse during luteolysis can lead to a transient resurgence in P4 concentration.

Effect of dose of estradiol-17β on prominence of an induced 13,14-dihydro-15-keto-PGF(2α) (PGFM) pulse and relationship of prominence to progesterone, LH, and luteal blood flow in heifers

Various doses of estradiol-17β (E(2)) were used in heifers to induce a pulse of 13,14-dihydro-15-keto-prostaglandin F(2α) (PGFM). The effect of E(2) concentration on the prominence of PGFM pulses and the relationship between prominence and intrapulse concentration of progesterone (P(4)), LH, and luteal blood flow were studied. A single dose of 0 (vehicle), 0.01, 0.05, or 0.1 mg of E(2) was given (n = six/group) 14 d after ovulation. Blood samples were collected, and luteal blood flow was evaluated hourly for 10 h after the treatment. The 0.05-mg dose increased and the 0.1-mg dose further increased the prominence of the induced PGFM pulse, compared with the 0.0-mg dose and the 0.01-mg dose. The PGFM pulses were subdivided into three different prominence categories (<50, 50 to 150, and >150 pg/mL at the peak). In the 50 to 150 category, P(4) concentration increased (P < 0.05) between -2 h and 0 h (0 h = peak of PGFM pulse). In the >150 category, P(4) decreased (P < 0.05) between -1 h and 0 h, LH increased (P < 0.05) at 1 h, and luteal blood flow apparently decreased (P < 0.05) at 2 h of the PGFM pulse. The novel results supported the following hypotheses: (1) an increase in E(2) concentration increases the prominence of a PGFM pulse, and (2) greater prominence of a PGFM pulse is associated with a greater transient intrapulse depression of P(4) at the peak of the PGFM pulse. In addition, the extent of the effect of prostaglandin F(2α) on the increase in LH and changes in blood flow within the hours of a PGFM pulse was related positively to the prominence of the PGFM pulse.

Effect of luteinizing hormone oscillations on progesterone concentrations based on treatment with a gonadotropin-releasing hormone antagonist in heifers

Close temporality has been reported between the episodic secretion of luteinizing hormone (LH) and progesterone (P4) during the midluteal phase and preceding the beginning of luteolysis in cattle. In the present studies, the relationship between LH and P4 was examined by blocking LH oscillations with the gonadotropin-releasing hormone (GnRH) antagonist, acyline. In a titration study, the minimal single acyline dose for blocking LH oscillations in heifers was 3 μg/kg. The main experiment compared LH and P4 concentrations and oscillations between a group treated with acyline on day 15 after ovulation (n = 8) and a control group (n = 4). Concentrations of P4 in blood samples collected every 8 h on days 13 to 18 indicated that acyline treatment did not alter the time that luteolysis began or the length of the luteolytic process. In blood samples collected every hour for 24 h beginning at the hour of treatment, acyline reduced the LH concentrations and blocked LH oscillations. The hourly LH means were 0.06 to 0.08 ng/mL, comparable to the mean concentration at the nadirs of LH oscillations in controls (0.07 ng/mL). During the hourly sampling, the GnRH antagonist produced the following P4 responses: (1) lower P4 concentrations, (2) fewer and reduced prominence of P4 oscillations, and (3) increased length and variability in the interval between the peaks of P4 oscillations. Results indicated that LH oscillations affect both the prominence and the rhythmicity of P4 oscillations during preluteolysis but not the onset and length of luteolysis.

11 FERTILITY EVALUATION OF THE GOAT SEMEN DILUTED IN CITRATE-EGG YOLK EXTENDER WITH HIGH OR LOW EGG YOLK CONCENTRATION, COOLED AND STORED AT 5°C FOR 24 HOURS

This experiment was designed to evaluate, in vitro and in vivo, the cooling resistance of the goat semen diluted in citrate-egg yolk extender with high (20%) or low (2.5%) concentration of egg yolk. The experiment was conducted at Dairy Goat Station of the Animal Science Department (Federal University of Viçosa, MG, Brazil), during the natural breeding season (March to June). Four bucks of the Alpine (n = 2) and Saanen (n = 2) breeds were used as semen donors. The bucks did not have apparent abnormalities of the reproductive tract and the fertility was proved based on andrologic examination and the records from the previous breeding season. The semen was collected by the artificial vagina method and a fresh sample was analyzed for the sperm cell motility and concentration. Therefore, the semen was diluted in citrate-egg yolk extender with high (T1 = 20%) or low (T2 = 2.5%) concentration of egg yolk, cooled and stored at 5°C for 24 h, before being used either for quality analysis or for AI. Reproductive-age female Saanen and Alpina goats (n = 68) were inseminated via cervix with cooled semen from T1 (n = 32) or from T2 (n = 36). The parametric data from cooled semen quality (sperm cell motility, vigor, hyposmotic swelling test, morphology, and supravital staining) were analyzed by ANOVA, for the main effect of the treatment, using the SAEG 9.0 program (UFV, 2005). The differences between means were accessed by the Student-Newman-Keuls test. The qualitative data from pregnancy rate were tested by chi-square (Ayres et al. BioEstat 2.0, 2000). The mean ± SEM for each quality test of the cooled semen, as well the P-value for comparisons between treatments were as follows: motility, 68.6 ± 15.5 and 78.0 ± 5.6% (P < 0.05); vigor, 2.5 ± 0.6 and 3.2 ± 0.3 (P < 0.05); supravital staining, 59.4 ± 17.3 and 71.2 ± 10.6% (P < 0.05); and hyposmotic test, 42.3 ± 15.8 and 56.3 ± 11.6% (P < 0.05), respectively, for T1 and T2. The pregnancy rate was higher (P < 0.05) in goats inseminated with cooled semen from T2 (66.7%) than in those inseminated with T1 (31.25%). The number of the offspring did not differ (P > 0.05) between treatments (1.3 ± 0.5 and 1.4 ± 0.5 kids, forT1 andT2, respectively). The interpretation was that the goat semen diluted, cooled, and stored in citrate-egg yolk extender prepared with a low (2.5%) concentration of egg yolk produced higher pregnancy rate and the tests of semen quality were sensitive to assess this difference. Financial support was provided by CnPQ (Brazil).

37 USE OF THERMO-RESISTANCE TEST (TRT) TO EVALUATE EQUINE COOLED SEMEN STORED AT 5°C

Evaluation of seminal characteristics is an important step to predict the reproductive potential of equine semen in natural or AI programs. Thermo-resistance test (TRT) has wide acceptance among tests in the bovine species, mainly because of its high correlation with fertility field. However, the TRT for stallion semen has not been widely studied. The objective of this study was to evaluate the effective use of TRT for equine cooled semen diluted with different extenders. Three stallions of Mangalarga Marchador breed aged between 8 and 14 years were used. Five semen samples per stallion were obtained, collected 3 times a week, with the aid of an artificial vagina (adapted Hannover model) using mares in natural estrus as dummy. The semen was diluted in 2 extenders: skim dried milk-glucose (E1) and glycine-egg yolk (E2), packaged in samples containing 12 mL of diluted semen to reach a final concentration of 30 million viable spermatozoa mL-1 and then stored at 5°C in an Equitainer® for 24 h. The cooled semen was warmed at 37°C in a water-bath. Spermatozoal progressive motility and vigor of semen were evaluated at 0 (TRT0), 30 (TRT30), 60 (TRT60), and 90 (TRT90) min after the start of warming. Treatment differences for sperm parameters were determined using ANOVA. The average values of sperm motility during TRT0, TRT30, TRT60, and TRT90 in E1 and E2 were, respectively, (E1) 37.0, 31.3, 23.7, and 19.7 and (E2) 30.3, 23.7, 18.3, and 15.7. The average values of vigor during TRT0, TRT30, TRT60, and TRT90 in E1 and E2 were, respectively, (E1) 2.4, 2.03, 1.53, and 1.43 and (E2) 1.97, 1.53, 1.33, and 1.17. During the test, the progressive motility obtained with E1 was higher (P < 0.05) than that with E2, and is within the patterns of motility considered acceptable only at 0 and 30 min of TRT. The E2 extender gave the worst result of the test, which was below the standards recommended for cooled semen. The seminal characteristics decreased in a very short time of TRT (30 min). This test is for use in insemination program. Thus, this demonstrates that changes in interpretation of the test need to be made in equine semen evaluation. A marked reduction of progressive motility at 30 min of test can be caused by loss of intracellular components or lesions in sperm movement structures. Possibly, availability of cyclic nucleotides involved in oxidative phosphorylation and motility are insufficient, although the mitochondria have the ability to produce energy. The TTR time of 90 min is long for equine cooled semen, and a duration for TTR of 30 min may be more appropriate in this species. Supported by grants from CNPq and CAPES.