Effect of arachidonic acid on pre- and post-hatching in vitro bovine embryo development

CONTEXT

Arachidonic acid (AA) is the precursor of prostaglandins, which may play autocrine roles during early embryo development.

AIMS

To test the developmental effects of addition of AA to pre- and post-hatching culture media on in vitro-produced bovine embryos.

METHODS

Pre-hatching effects of AA were tested by culturing bovine zygotes in synthetic oviductal fluid (SOF) supplemented with 100 or 333μM AA. Post-hatching effects of AA were tested by culturing Day 7 blastocysts in N2B27 supplemented with 5, 10, 20 or 100μM AA up to Day 12.

KEY RESULTS

Pre-hatching development to blastocyst was completely abrogated at 333μM AA, whereas blastocyst rates and cell numbers were not altered at 100μM AA. Impaired post-hatching development was observed at 100μM AA, whereas no effect on survival rates was noted at 5, 10 and 20μM AA. However, a significant reduction in Day 12 embryo size was observed at 10 and 20μM AA. Hypoblast migration, epiblast survival and formation of embryonic-disc-like structures were unaffected at 5-10μM AA. AA exposure downregulated the genes PTGIS, PPARG, LDHA and SCD in Day 12 embryos.

CONCLUSIONS

Pre-hatching embryos are mostly irresponsive to AA, whereas AA was observed to have negative effects during early post-hatching development.

IMPLICATIONS

AA does not improve in vitro bovine embryo development and is not required up to early post-hatching stages.

Use of the flavonoid taxifolin for sperm cryopreservation from the threatened Bermeya goat breed

Taxifolin is a plant flavonoid effective as an antioxidant. This study aimed to assess the effect of adding taxifolin to the semen extender during the cooling period before freezing on the overall post-thawing sperm variables of Bermeya goats. In the first experiment, a dose-response experiment was performed with four experimental groups: Control, 10, 50, and 100 μg/ml of taxifolin using semen from 8 Bermeya males. In the second experiment, semen from 7 Bermeya bucks was collected and extended at 20 °C using a Tris-citric acid-glucose medium supplemented with different concentrations of taxifolin and glutathione (GSH): control, 5 μM taxifolin, 1 mM GSH, and both antioxidants. In both experiments, two straws per buck were thawed in a water bath (37 °C, 30 s), pooled, and incubated at 38 °C. Motility (CASA) was assessed at 0, 2, and 5 h, and sperm physiology was assessed at 0 and 5 h by flow cytometry (viability, intact acrosome membrane, mitochondria membrane potential, capacitation, intracellular reactive oxygen species -ROS-, mitochondrial superoxide, and chromatin status). In experiment 2, an artificial insemination trial (AI) was included with 29 goats for testing the taxifolin 5-μM treatment on fertility. Data were analyzed with the R statistical environment using linear mixed-effects models. In experiment 1 and compared to the control, T10 increased progressive motility (P < 0.001) but taxifolin decreased total and progressive motility at higher concentrations (P < 0.001), both post-thawing and after the incubation. Viability decreased post-thawing in the three concentrations (P < 0.001). Cytoplasmic ROS decreased at 0 and 5 h at T10 (P = 0.049), and all doses decreased mitochondrial superoxide post-thawing (P = 0.024). In experiment 2, 5 μM taxifolin or 1 mM GSH (alone or combined) increased total and progressive motility vs. the control (P < 0.01), and taxifolin increased kinematic parameters such as VCL, ALH, and DNC (P < 0.05). Viability was not affected by taxifolin in this experiment. Both antioxidants did not significantly affect other sperm physiology parameters. The incubation significantly affected all the parameters (P < 0.004), overall decreasing sperm quality. Fertility after artificial insemination with doses supplemented with 5 μM taxifolin was 76.9% (10/13), not significantly different from the control group (69.2%, 9/13). In conclusion, taxifolin showed a lack of toxicity in the low micromolar range and could benefit goat semen cryopreservation.

14 MORPHOLOGICAL AND FUNCTIONAL PARAMETERS OF ENDANGERED BERMEYA GOAT BREED SEMEN

The Bermeya goats are an endangered autochthonous breed distributed in the north of Spain. To ensure their genetic diversity and long-term survival, morphological and functional parameters of the semen must be known in order to preserve the current genetic stock in a germplasm bank. The aim of this work was to establish basic characteristics and post-thaw survival of Bermeya goat's semen obtained by electro-ejaculation, that is not well described in the literature. The semen was collected by electro-ejaculation from 7 bucks, 1 to 7 years old, twice per week, for 9 weeks (n = 83). Fresh semen was evaluated for volume (V), concentration (C), motility, morphology, functional integrity of the sperm (spz) membranes (hypoosmotic swelling test; HOST), and acrosome integrity rate (NAR). Individual and progressive sperm motility were analyzed by means of a computer-assisted sperm analysis system (CASA: SCA 2002�, Microptic, Barcelona, Spain) immediately after dilution with the extender at 37�C, and after cooling to 4�C; five fields per sample (diluted to 204 � 106 spz mL–1) were evaluated under a phase contrast microscope (100�). The NAR and morphological abnormalities of sperm head, midpiece, tail, and cytoplasmic droplets were determined by counting 100 spz under 1000�. For freezing, ejaculates with at least 80% motile spz were diluted at 32�C with Krebs-Ringer solution containing 20% egg yolk and 14% glycerol to a final concentration of 400 � 106 spz mL–1, cooled to 4�C for 90 min, aspirated into 0.25-mL plastic straws (IMV�, L'Aigle, France), frozen at 7 cm above liquid nitrogen (LN2) phase for 10 min, and then plunged into the LN2. Straws were thawed in a water bath at 39�C for 30 s for post-thaw survival analysis. Data were analyzed by the GLM and FREQ procedures (SAS; SAS Institute, Inc., Cary, NC, USA) and expressed as means � standard error. Fresh semen characteristics were: V = 1.7 � 0.1 mL; C = 2619 � 106 � 153 spz mL–1; total and progressive motility were 89.0 � 2.1% and 66.9 � 2.1%, respectively. Percentages of head abnormalities were 4.8 � 0.5; midpiece: 3.8 � 0.7; tail: 4.7 � 1.0; cytoplasmic droplets: 8.3 � 0.7; intact acrosome: 91.8 � 0.6; and membrane integrity: 49.2 � 2.1. At 4�C, the % of total motile spz was 62.6 � 1.6, and the post-thaw survival rate was 46.3 � 1.5. There were only individual differences (P < 0.001) between bucks on sperm concentration, head abnormalities, and cytoplasmic droplets. In conclusion, our results indicate that semen quality is related to each individual animal and that electro-ejaculation allows collection of semen of satisfactory quality to use as fresh and for cryopreservation. However, the validity of our results for possible future sperm banking of endangered Bermeya goats semen must be confirmed by field trials.

Experimental neosporosis in bulls: Parasite detection in semen and blood and specific antibody and interferon-gamma responses

AIM

To investigate the presence of Neospora caninum in semen and blood, and the development of specific antibody and interferon-gamma (IFN-gamma) responses in experimentally infected bulls.

METHODS

Eight bulls were intravenously infected with 10(8) live N. caninum tachyzoites of NC-1 isolate. The presence of N. caninum in semen and blood was assessed using a nested-PCR procedure. PCR-positive semen samples were bioassayed using a BALB/c nu/nu mouse model. Specific anti-N. caninum antibody and IFN-gamma responses were also examined. In parallel, eight seronegative bulls were studied as non-infected controls. All bulls were monitored for 26 weeks.

RESULTS

All eight experimentally infected bulls showed N. caninum DNA in their semen and/or blood samples at some time during the course of the study. Parasite load in semen ranged from 0.1 to 14.5 parasites/ml (mean 6.0). N. caninum could not be detected in BALB/c nu/nu mice inoculated with PCR-positive semen samples. A significant increase in mean serum specific IgM antibody response to N. caninum was detected between 10 and 28 days post-infection (p.i.). Serum specific IgG, IgG1, and IgG2 antibody levels in experimentally infected bulls were significantly different after 21, 10, and 14 days p.i. as compared to controls, respectively. Specific anti-N. caninum IgG were detected in seminal plasma from infected bulls and values obtained were different from controls after 25 days p.i. Mean specific IFN-gamma responses in experimentally infected bulls were significantly higher than controls 3 days p.i.

CONCLUSIONS

This is the first study to report the presence of N. caninum DNA in the semen and blood of experimentally infected bulls. Our observations indicate an intermittent presence of N. caninum in low numbers in semen and associated with chronic stage of the infection. This study is also the first to report the detection of anti-N. caninum IgG in seminal plasma of experimentally infected bulls.

20 SPERM CHARACTERIZATION OF ASTURCON PONIES AFTER COLLECTION AND EQUILIBRATION/REFRIGERATION BEFORE FREEZING

The need to conserve farm animal biodiversity is accepted by many countries through the ratification of the convention of biological diversity, and sperm quality is known to be an important criterion in the evaluation of breeding soundness. The aim of this work was to characterize the semen of a local breed of ponies 'Asturcon' (maintained free over the mountains all year around) before its incorporation into a germplasm bank. Semen was obtained from six stallions (6–17 years of age) using an artificial vagina, 3 days/week, during 12 weeks. Immediately after collection, gel-free semen was evaluated for volume, sperm concentration, and motility. Semen motility was again evaluated after equilibration/refrigeration. For evaluation of individual (IM) and progressive motility (PM) rates, semen was diluted (20 � 106 spermatozoa/mL) and analyzed with a CASA System (SCA; Microptic S.L., Barcelona, Spain). Five fields per sample were evaluated (minimum 500 spermatozoa/sample) under a phase contrast microscope (100�). Semen samples were subjected to a hypo-osmotic swelling test (HOS) test to detect the presence of swollen tails in a 100 mM citrate–fructose solution. Percentages of altered acrosomes and morphological abnormalities were determined by counting 100 spermatozoa (1000�). Then, semen was diluted and centrifuged for 10 min at 600g. After the supernatant was discarded, the pellet was re-suspended in freezing medium (skim milk extender containing 2% egg yolk and 2.5% glycerol) to a final concentration of 100 � 106 spermatozoa/mL, and equilibrated/cooled (60 min) to 4�C. Statistical analysis was carried out by means of the GLM and CORR procedures and Duncan test for means (SAS Institute, Inc., Cary, NC, USA). A significant effect between males (P &lt; 0.05) on semen quality, such as volume of the ejaculate, sperm concentration, and morphological abnormalities, were detected among stallions. On the other hand, positive and significant correlations were found between the sperm motility immediately after collection and after equilbration/refrigeration (r = 0.73; P &lt; 0.05); moreover, sperm motilities (both fresh and refrigerated) correlated with the results of the HOS test (r = 0.56; P &lt; 0.001, and r = 0.27, P &lt; 0.05, respectively). These preliminary results confirm that the sperm of the Asturcon ponies breed can be collected and will survive the equilibration/refrigeration procedures. Conservation and development of local breeds is important because they represent a unique source of genes for improving health and performance traits of industrial breeds. However, complementary studies on the ability of the stallion sperm to survive freezing/thawing procedures in rates higher than 30% are needed to ensure that genetic banks are correctly created. This work was performed in collaboration with ACPRA and Dep�sito de Sementales de Santander (Spain), and supported by RZ2004-00031-C02-01.

111 ESTIMATION OF SPERM QUALITY IN FRESH AND FROZEN - THAWED SEMEN FROM ASTURIANA DE LOS VALLES BULLS

Artificial insemination and semen cryopreservation have significantly improved the breeding potential of male animals. However, current freezing techniques commonly result in reduced semen quality (Januskauskas et al. 1999 Theriogenology 52, 641-658), and surviving cells are affected post-thaw either structurally or functionally (Nagy et al. 2004 Anim. Reprod. Sci. 80, 225-235). In this work we analyze the impact of cryopreservation on Asturiana de los Valles bull sperm. Ejaculates (n = 373) from seven adult bulls were weekly collected by means of artificial vagina. Immediately after collection, routine parameters including volume (V), mass motility (MM), and concentration (C) of sperm cells were evaluated. Then the semen was extended with a commercial extender, loaded into 0.25-mL plastic straws at a concentration of 23 � 106 per straw, frozen and stored for further analysis. Four straws per ejaculate were thawed, pooled and analyzed for motion characteristics by means of a CASA system (Sperm Class Analyzer, SCA 2002� Microptic S. L., Barcelona, Spain) added to an optical phase-contrast microscope with heatable (37�C) stage. Immediately after thawing, we analyzed the % of motile spermatozoa (MS) and the % of progressively motile spermatozoa (PMS); then samples were incubated for 3 h at 37�C and MS and PMS were measured again (MS3 and PMS3, respectively). Functional integrity of the plasmallema was evaluated by the hypoosmotic swelling test (HOST) together with the % of typical tail coiling/swelling (percentage of HOST-positive spermatozoa, HOST-PS). The % of viable spermatozoa (VS) [membrane integrity was evaluated by fluorescence microscopy with a dual staining system (propidium iodide (PI) and 6-carboxyfluorescein diacetate (CFDA)]. Sperm showing partial or complete red fluorescence (PI staining) were considered nonviable, whereas sperm showing complete green fluorescence were considered viable. Altered acrosomes (AA) and morphological abnormalities were also determined. The % of morphological abnormalities was classified according to their location in head (HA), midpiece (MA), and tail (TA). Proximal and distal cytoplasmic droplets were counted as separate abnormalities (CD). Data were analyzed by the MEANS procedure of SAS (SAS Institute, Inc., Cary, NC, USA). A significant (P < 0.05) decrease in the sperm motility was observed after freezing/thawing (MS: 80.20 � 0.75 vs. 47.36 � 1.04, and PMS: 68.73 � 0.73 vs. 42.14 � 0.96 for fresh and frozen-thawed semen, respectively). Also, the frozen-thawed sperm showed increased % of HA, MA, AA, HOST-PS, and VS (P < 0.05). These morphological abnormalities could contribute to decreasing sperm motility. The new computer and video technologies provide useful information about sperm quality and can be used in the daily routine of processing semen. This work was performed in collaboration with ASEAVA.