12 QUANTIFICATION OF REACTIVE OXYGEN SPECIES IN BOVINE SEMEN WITH DIFFERENT SEMINAL QUALITY AND WITH EXTENDER CONTAINING ANTIOXIDANT EVALUATED BY ARTIFICIAL INSEMINATION

The aim this study was to evaluate the effects on artificial insemination (AI) of minimizing oxidative stress by adding an antioxidant into the sperm microenvironment. For that purpose, semen of bulls with different seminal quality was evaluated in nature and after addition of extender with and without antioxidant, followed by freezing and thawing, with respect to thiobarbituric acid reactive substances (TBARS) concentration, total antioxidant capacity (TAC), and AI success. TBARS is an indicator of lipid peroxidation and TAC measures free radicals. Twelve ejaculates from 5 bulls were treated with Tris egg yolk extender (CE) and in half of each ejaculate the extender was supplemented with 200 μL of Trolox (AE). Three of these 5 bulls had high-quality semen (mean 11.9 ± 5.9 total defect, 7.7 ± 3.1 major defect, and 4.2 ± 3.9 minor defect) and 2 animals had poor-quality sperm (mean 31.9 ± 9.7 total defect, 26.3 ± 8.5 major defect, and 5.6 ± 5.0 minor defect) (P < 0.05). For AI, 300 Nelore heifers were divided in 10 groups and the females in each group were inseminated with semen of the same bull and extender treatment. To evaluate oxidative damage, TBARS concentration was measured to indirectly determine malondialdehyde (lipid-peroxidation metabolite) concentration, whereas TAC was measured using myoglobin, as a source of radicals, which interact with a chromogen 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), whose cation radical is spectroscopically detectable. The latency phase (lag) in the accumulation of ABTS cation is proportional to the antioxidant concentration. The pregnancy rates 60 days after AI were analyzed by chi-square test, and data of free radical production were evaluated by ANOVA, followed by the Tukey test with significance level of 5%. Reactive oxygen species (ROS) production in nature semen (0.351 nmol of TBARS in 50 × 108 spermatozoa) was lower (P < 0.05) when compared to diluted semen (0.367 nmol of TBARS in 50 × 108 spermatozoa). No difference (P > 0.05) between extenders was observed after thawing. The bulls with poor-quality semen presented total ROS production (0.967) superior (P < 0.05) to that of bulls with good-quality semen (0.753). Although the use of antioxidant in the extender did not decrease ROS and TAC production (P > 0.05), pregnancy rates after AI in bulls with poor quality semen with AE (60.0%) was superior (P < 0.06) to that in bulls with high-quality sperm with AE (56.6%). In conclusion, bulls with poor-quality semen present higher ROS and TAC production, and the use of antioxidant in the extender for cryopreservation with poor-quality bovine semen, in spite of not decreasing ROS and TAC production, improves pregnancy rates. Financial support: FAPESP.

Sexing of murine and bovine embryos by developmental arrest induced by high-titer H-Y antisera

Murine and bovine embryos at the late morula stage were cultured in medium containing high-titer rat H-Y antisera. After 12h of incubation, embryos blocked at the late morulae stage were classified as males and those at the blastocyst stage were classified as females. Sexing of murine embryos by PCR and cytogenetics revealed that 83% of the embryos classified as males and 82% of those classified as females had their sex correctly predicted (P < 0.05). Bovine embryos were transferred to recipient females. Pregnancy rates were 71.4% (10/14) for embryos classified as males and 68.8% (11/16) for embryos classified as females. The sex was correctly predicted for 80% (8/10) of the embryos classified as males and for 81.8% (9/11) of those classified as females (overall accuracy, 80.9%, P < 0.05). Therefore, the induction of developmental arrest by high-titer male-specific antisera was an efficient strategy for non-invasive embryo sexing. The procedure was straightforward and has considerable commercial potential for sexing bovine embryos.

Efficacy of linear and convex transducers for ultrasound-guided transvaginal follicle aspiration

A new device was developed to hold linear transducers for transvaginal follicle aspiration. Efficacy of follicle aspiration was compared using a linear 6 MHz and a convex 5 MHz transducer. Fifty-five cows were submitted to follicle aspiration at random days of the estrous cycle. Aspirations were conducted with linear (n=28) and convex (n=38) transducers with 18 G needles at a negative pressure corresponding to 13 ml H(2)O/min. A greater number of follicles were aspirated using convex than to linear probe (12.4 versus 7.8, respectively, P<0.05). Mean number of oocytes and recovery rates were similar for convex (5.4 and 48.6%) and linear (4.6 and 59.3%) transducers. Limited space between the linear transducer and needle guide restricted access to some portions of the ovary, reducing the number of follicles aspirated using a linear transducer. The newly developed adaptor allowed greater stability, holding the ovaries firmly against the linear transducer. This diminished mobility permitted a similar number of oocytes to be recovered with both transducers. In conclusion, this new adaptor provided a low cost alternative for routine follicle aspiration and oocyte recovery in cattle.

Relationship between follicle size and ultrasound-guided transvaginal oocyte recovery

We evaluated the relationship between follicle size and oocyte recovery (OR) using ultrasound-guided follicle aspiration. Thirty Holstein cows were subjected to OR without gonadotrophic therapy. Oocytes were recovered two to four times from each cow in a total of 67 aspiration sessions. Ovarian follicles with diameters < or =4 mm and >4 mm were aspirated in separated groups. Recovered oocytes from each group were kept separate and submitted to in vitro maturation, fertilization, and culture to the blastocyst stage. A total of 430 follicles were aspirated, of which 154 (35.8%) were from follicles >4 mm and 276 (64.2%) were from follicles < or =4 mm. Seventy-seven oocytes (50%) were recovered from follicles >4 mm and 200 (72.2%) were from follicles < or =4 mm. Nineteen blastocysts were obtained from follicles >4 mm, whereas 45 blastocysts were obtained from follicles < or =4 mm. Recovery rate was greater (P<0.01) in follicles < or =4 mm. Oocyte quality, cleavage rate and blastocyst development did not differ between different follicle sizes. Routine aspiration of small follicles (< or =4 mm) could increase the number of oocytes available for in vitro development.

Plasma concentrations of progesterone, 17β-estradiol and androstenedione and superovulatory response of Nelore cows () treated with FSH

Progesterone (P(4)), 17beta- estradiol (E(2)) and androstenedione (A(4)) plasma concentrations were correlated with palpated corpora lutea (CL), recovered embryos and viable embryos in 13 Nelore cows induced to superovulate with FSH, starting on Day 10 of the estrous cycle. Administration of FSH increased the number of ovulations and recovered embryos. Plasma P(4), E(2) and A(4) levels on Day 0 and of P(4) on Days 10 and 11 of the cycle were not correlated with the superovulatory response. Determination of CL by palpation per rectum was used to estimate the number of recovered embryos. Plasma P(4) levels higher than 1 ng/ml on the induced estrus day (Day 14) had an adverse effect on the embryo viability rate. Plasma E(2) concentrations on Day 14 were positively correlated with the number of viable embryos collected, a correlation that has not been previously reported. The present data indicate that plasma P(4) and E(2) concentrations in FSH-PGF2alpha-treated Nelore cows are useful for the identification of 2 different populations of Nelore donors and are correlated with superovulatory response and, particularly, with the number of viable embryos.

Relationship between plasma 17-beta estradiol on the day of estrus and number of viable embryos in Bos indicus (Nellore) cows superovulated with FSH

Thirteen cows, Bos indicus, of the Nellore breed were superovulated with 22 mg of follicle stimulating hormone (FSH) administered by intramuscular route during four consecutive days (D10, D11, D12 and D13), starting on the 10th day of the estrous cycle (day 0 = estrus). Prostaglandin (PGF2 alpha, 1.0 mg, im) was administered on D12, 48 h after the first FSH injection, for the induction of estrus on D14, when artificial insemination was performed. Seven days later (D21 of the cycle), embryos were collected, and evaluated, and the ovarian response was estimated on the basis of number of corpora lutea determined by rectal palpation. Blood samples were obtained for the determination of plasma 17-beta estradiol on D10, D11, D12, D13, D14 and D21 and plasma progesterone on D14 by RIA. The donors were divided into two groups according to progesterone levels on D14, the day of the induced estrus (GI: P4 < or = 1.00 ng/ml, N = 5 and GII: P4 > 1.00 ng/ml, N = 8). A linear positive correlation was observed between plasma 17-beta estradiol concentration on the day of estrus and viable embryo number. We conclude that plasma 17-beta estradiol and progesterone concentrations on the day of estrus can be used to predict the viability of embryos recovered from Nellore cows superovulated with FSH.