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This study evaluated the effect of increasing centrifugal force and reducing centrifugation time and volume in Percoll protocols on ram sperm parameters. Commercial semen of Santa Inês rams were used and five treatments were performed: traditional Percoll and mini-Percoll (MP) techniques (I- 5000 x g, 5min; II- 2500 x g, 5min; III- 1250 x g, 5min; IV- 700 x g, 10min). At post-thawing (PT) and post-selection protocols (0h), samples were assessed for spermatozoa recovery rate, motility, plasma membrane (PM) integrity, sperm capacitation and morphology and incubated at 37 C for 1, 2 and 3h. The sperm recovery rate averaged 9.1±1.4%, and most motility parameters were similar (P> 0.05) among protocols. VCL (µm/s) was higher (P< 0.05) after MP-II, III and IV (66.1±4.5) than traditional Percoll (46.3±4.9). Capacitation status and PM integrity were similar (P> 0.05) among treatments. For the first time, we have demonstrated the reduction of the gradient volume and centrifugation time associated with an increase on centrifugation force at Percoll can be successfully used for frozen-thawed ram sperm selection. MP may be used instead of traditional Percoll, decreasing costs and semen handling time.

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In vitro embryo production (IVP) is an important tool for cattle breeding. Brazilian dairy systems are based on Gyr × Holstein crossbreds, which integrates adaptability to tropical conditions and milk production. Quality determines the oocyte proportion that will develop to blastocyst stage, and although the lipid content is important in oocyte development, a high concentration in embryos is associated with cryotolerance reduction, making this a relevant issue for IVP systems. The in vitro maturation system (IVM) simulated physiological oocyte maturation (SPOM) mimics the physiological maturation events by using cyclic adenosine monophosphate (cAMP) modulators, which promote the increase of oocyte competence. Among the modulators, Forskolin has lipolytic properties. The aim of this study was to evaluate the effect of the SPOM system (Albuz 2010 Hum. Reprod. 25, 12) on bovine embryos (Gyr × Holstein) regarding their total number of cells (TNC) and lipid content. Oocytes were obtained by ovum pick-up from Gyr cows in 5 replications. After selection, they were randomly divided into 2 groups: SPOM (S) and control (C). The IVM lasted 24 h for group C (TCM 199 medium without FBS) in culture oven at 38.5°C, 5% CO2 in atmospheric air and high humidity. In the SPOM system, oocytes were in pre-IVM [TCM 199 medium + 100 µM Forskolin + 500 µM 3-isobutyl-1-methylxanthine (IBMX)] for 2 h and followed for extended IVM (TCM 199 medium + 20 µM cilostamide) for 28 h under the same conditions as control group. After IVM, oocytes were fertilised with semen from a single Holstein bull that was prepared by Percoll gradient method in Fert-TALP medium (Bioklone® Animal Reproduction, São Paulo, Brazil) for 22 h and transfered to culture droplets, where they remained for 7 days (n = 10–13 per group). The lipid content analysis was performed by staining with Oil red and the stained area fraction of each embryo was measured using software ImageJ (NIH, Bethesda, MD, USA). The TNC was measured after being stained with Hoechst 33342 and results were analysed by Student's t-test in Instat GraphPad program, with a 5% significance level. There was no significant difference (P > 0.05) between embryos from both groups on TNC (group S: 88.9 ± 28.0A; group C: 101.6 ± 29.1a) and lipid content (group S: 0.93 ± 12:18A; group C: ±0.15 to 0.96) analysis. Some studies have shown there is a beneficial effect on embryo quality when using this system; however, our results demonstrated that there was no effect on total number of cells using our conditions. Some authors have also demonstrated a reduction in embryo lipid content using Forskolin during in vitro culture. Our results suggest that the time of Forskolin exposure was not enough to ensure lipolytic action on the structures produced from oocytes (Gyr) treated in pre-IVM. It was concluded that the SPOM system had no effect on TNC and lipid content of Gyr/Holstein embryos. Financial support from FAPERJ and CAPES is acknowledged.

Oocyte cryopreservation is a strategic tool for in vitro embryo production, but low rates of cryosurvival are reported for bovine oocytes. Simulated physiological oocyte maturation system (Albuz et al. 2010 Hum. Reprod. 25, 12) uses cAMP modulators to increase oocyte competence by the extension of meiosis block and gap junctional communications activity. The aim of this study was to investigate the effect of simulated physiological oocyte maturation system on gap junctional activity of vitrified bovine oocytes. Oocytes from slaughterhouse ovaries were divided into 4 groups: C (control: fresh immature oocytes); V (vitrified immature oocytes); PM-V (vitrified oocytes after a 2-h pre-in vitro maturation phase – in the presence of AMPc modulators, 100 μM Forskolin, and 500 μM IBMX); and PM (fresh immature oocytes subjected to pre-in vitro maturation). Viable oocytes (n = 404 obtained from 4 replicates) were stained with Calcein-AM using the protocol of Thomas et al. (2004 Biol. Reprod. 71(4), 1142–1149) in order to measure gap junctions activity. Images were captured in fluorescence microscope, and fluorescence intensity was analysed with ImageJ software. Mean fluorescence intensity of each group was normalized to control group to obtain relative intensity value. Means were compared by Kruskal-Wallis test and Dunn post-test. A second analysis was performed considering the percentage of each staining pattern (low, middle, and high intensity) for each group. Results were analysed using Fisher exact test. All statistical analysis were performed in GraphPad Instat program with 5% significance level. Results demonstrated that all treatments induced an increase (P < 0.05) in fluorescence intensity (V: 1.76 ± 1.13; PM-V: 1.58 ± 0.98; PM: 1.38 ± 0.94) compared with control (C: 1.00 ± 0.48). Regarding the staining patterns analyses, immature vitrified oocytes (V group) differed from control group in middle and low patterns (G1, calibrator – high: 11.2%ab, middle: 43.8%a, low: 44.9%a; G2 – high: 8.2%ab, middle: 63.9%b, low: 27.9%b; G3 – high: 16.3%a, middle: 42.3%a, low: 41.3%a; G4 – high: 6.7%b, middle: 53.9%ab, low: 39.3a). In conclusion, unexpectedly, vitrification also increased gap junctional activity, as was found for pre-in vitro maturation group. However, staining pattern analysis results showed only vitrified group was different from control, suggesting vitrified and pre-in vitro maturation groups could have gap activity affected by different ways. This research was supported by FAPERJ (E26/111.61/2013) and CAPES.

In vitro embryo production (IVP) is an important tool for cattle breeding. Brazilian dairy systems are based on Gyr/Holstein crossbreds, which integrates adaptability to tropical conditions and milk production. Oocyte quality is crucial for IVP, and lipid accumulation is a detrimental factor. The aim of this study was to assess the effect of SPOM maturation system (Albuz et al. 2010 Hum. Reprod. 25) on lipid accumulation in bovine oocytes. Oocytes obtained by ovum pick-up (OPU) from heifers without ovarian stimulation were transferred to control media (TCM 199 + sodium pyruvate, ITS, penicillin-streptomycin, BSA, FSH, oestrogen, and hCG) or SPOM (2 h pre-IVM: TCM 199 hepes + sodium pyruvate, ITS, penicillin-streptomycin, BSA, IBMX, and forskolin; followed by 28 h IVM: control media + cilostamide) in 5% CO2 atmosphere at 38°C. Oocytes were collected after 20, 24, and 28 h (groups: C20, C24, C28; S20, S24, S28) and evaluated for nuclear maturation using HOECHST (experiment 1, n = 301, 35–62 per group) and lipid content using Oil Red (experiment 2, n = 163, 14–42 per group). Oocytes from 4 replicates were fixed with PFA and stored at 4°C. For Oil Red, all structures were stained and evaluated at the same day. After being washed in 50% ethanol, oocytes were incubated in 0.2% Oil Red O solution for 10 min. Stained area fraction in each oocyte cytoplasm was measured using ImageJ (NIH). Nuclear maturation analysis was performed by Chi-squared test and Lipid analysis by Kruskal-Wallis and Dunn's post-test (P = 0.05). Distinct superscript letters indicate statistical difference between groups. In experiment 1, we detected a reduction in the percentage of matured (MII) oocytes only in S20 group (C20 = 64.28%a, C24 = 74.28%a, C28 = 60.46%a, S20 = 25.8%b, S24 = 59, 01%a, S28 = 74.13%a). In experiment 2, we detected an increase in lipid content in both control and SPOM groups from 20 to 28 h of IVM (S20 = 5.72a ± 4.41, S24 = 15.95bd ± 7.41, S28 = 37.46c ± 8.68, C20 = 8.65a ± 2.58, C24 = 12.14ad ± 8.08, C28 = 18.50b ± 8.09). For SPOM groups, the lipid content increased 2.78-fold from S20 to S24, and 6.54-fold from S20 to S28. In the control group, only in C28 wasa lipid increase detected, 2.13-fold higher than C20 content. Comparing control and SPOM groups at each time point, S28 displayed a 2.02-fold increase in lipid content compared to C28. We concluded that despite SPOM system being effective in maintaining meiotic arrest until 20 h of IVM and forskolin being present during pre-IVM in SPOM groups, Gyr/Holstein crossbreed oocytes obtained by OPU presented a significant increase in lipid content when matured in SPOM system, even higher than observed for the control group. During the last 8 h of IVM we observed a huge lipid accumulation in both systems, suggesting this might be a crucial period.