Separation of motile spermatozoa from frozen-thawed buffalo semen: swim-up vs filtration procedures

New insights into semen separation techniques in buffaloes

Male infertility is frequently caused by idiopathic or unexplained reasons, resulting in an increase in demand for assisted reproductive technologies. In buffaloes, more than in other animals due to reproductive hardiness, successful fertilization needs spermatozoa to effectively transit the female reproductive system to reach the oocyte. This mechanism naturally picks high-quality sperm cells for conception, but when artificial reproductive technologies such as in vitro fertilization, intracytoplasmic sperm injection, or intrauterine insemination are utilized, alternative techniques of sperm selection are necessary. Currently, technology allows for sperm sorting based on motility, maturity, the lack of apoptotic components, proper morphology, and even sex. This study provides current knowledge on all known techniques of sperm cell sorting in buffaloes, evaluates their efficiency, and discusses the benefits and drawbacks of each approach.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

Nano-purification of raw semen minimises oxidative stress with improvement in post-thaw quality of buffalo spermatozoa

The study consisted of application of anti-ubiquitin antibodies (Abs)-coated iron oxide-nanoparticles (IONPs) for minimisation of oxidative stress to contemporary live spermatozoa from the raw semen. Round-shaped IONPs (12.09 ± 0.91 nm) after two-stage functionalisation (silanisation and pegylation) were conjugated with Abs. Four aliquots from each of the 24 ejaculates (4 buffalo bulls) formed Control (Group I) and treatment (II, III and IV) groups; each containing 150 ± 25 million dead/damaged spermatozoa. IONPs-Abs complex were added at ratio of 1:1 (0.5 µg/ml), 1:2 (1.0 µg/ml) and 1:4 (2.0 µg/ml), respectively, in Groups II, III and IV. The semen quality parameters showed improvement at lag-stage (post-nano-purification before processing for cryopreservation). The mean post-thaw motility (%) in Group IV was found to be greater (p < .05) than Group I. Moreover, the overall DNA integrity (%) at post-thaw stage was improved in the nano-purified semen samples. The value of malondialdehyde was greater (p < .001) in Group I than Groups II, III and IV. The mean total antioxidant capacity and superoxide dismutase (U/mg protein) activity values in Group IV was greater (p < .05) than Group I. The study results show that IONPs conjugated with anti-ubiquitin Abs at 2.0 µg/ml can be an effective dose for depletion of dead/damaged spermatozoa from buffalo ejaculates to minimise oxidative stress.

Sperm preparation through Sephadex™ filtration improves in vitro fertilization rate of buffalo oocytes

Routinely, swim-up method is used to separate high-quality sperm; however, long processing time and close cell-to-cell contact during the centrifugation step are inevitable elements of oxidative stress to sperm. The objective was to evaluate Sephadex^™ and glass wool filtration to separate motile, intact and viable sperm for in vitro fertilization in buffalo. The cumulus-oocyte complexes (COCs) were collected from ovaries of slaughtered buffaloes by aspiration and matured for 24 hr in CO₂ incubator at 38.5°C and 5% CO₂ . Matured COCs were rinsed twice in fertilization TALP and placed in the pre-warmed fertilization medium without sperm. Cryopreserved buffalo semen was thawed at 37°C for 30 s and processed through Sephadex^™ , glass wool filtration and swim-up (control). Total and motile sperm recovery rates were assessed, resuspended in fertilization TALP and incubated for 15-20 min in CO₂ incubator. Samples prepared by each method were divided into two aliquots: one aliquot was studied for sperm quality (progressive motility, membrane integrity, viability, liveability), while the other was subjected to co-incubation with sets of 10-15 in vitro matured oocytes. Data on sperm quality were analysed by ANOVA, while in vitro fertilizing rates were compared by chi-squared test using SPSS-20. Least significant difference (LSD) test was used to compare treatment means. Glass wool filtration yielded higher total and motile sperm recovery rate, while Sephadex^™ filtration improved (p < .05) sperm quality (progressive motility, membrane integrity, viability, liveability). Sperm preparation through Sephadex filtration yielded higher in vitro fertilization rate in terms of cleavage rate compared to glass wool filtration and swim-up (control). In conclusion, cryopreserved Nili-Ravi buffalo sperm selected through Sephadex filtration showed improved quality and yielded better fertilization rates (cleavage rate) of in vitro matured/fertilized oocytes. Sephadex filtration could be a promising technique for use in in vitro fertilization in buffalo.

Freezability of equine semen after glass beads column separation

REASONS FOR PERFORMING STUDY

The success rate of artificial insemination following the freezing of stallion semen is limited; therefore, improving the stallion semen quality after the freezing and thawing process is a necessary objective.

OBJECTIVES

To investigate the influence of glass bead column separation on the freezability of stallion semen.

HYPOTHESIS

Glass beads in a column separator remove damaged and dead spermatozoa in the ejaculate during centrifugation.

METHODS

In total, 50 ejaculates from 6 Lipizzaner stallions were studied. Each ejaculate was divided into 2 parts, one half processed following standard procedure and the second half used for the column separation procedure. After freezing, semen quality was evaluated using standard tests for motility, morphology and viability of semen.

RESULTS

Motility and progressive motility of the column-separated (CS) semen were significantly higher (P < 0.001) before freezing and immediately, 24 and 48 h after thawing. A significant increase (P < 0.001) in the percentage of hypoosmotic positive spermatozoa was observed in CS samples. The percentage of total morphological changes in the separated samples before and after freezing was significantly lower (P < 0.001) compared with samples prepared using the standard procedure. A substantial decrease (P < 0.001) was found in the percentage of spermatozoa with damaged acrosomes. However, the percentage of spermatozoa with coiled tails was increased in the separated samples (P < 0.001).

CONCLUSIONS

Column separation before freezing has a positive effect on the quality of thawed equine semen.

POTENTIAL RELEVANCE

The quality of CS frozen/thawed samples indicates their potential use for increasing insemination success in mares.

Sephadex and sephadex ion-exchange filtration improves the quality and freezability of low-grade buffalo semen ejaculates

The effect of sephadex and sephadex ion-exchange filtration on the improvement in quality and freezability of low-grade buffalo semen ejaculates was assessed. Two types of filtration columns were used: one containing only sephadex G-10 (FS) and the other sephadex G-10 along with ion-exchangers (diethyl amino ethane-52 (DEAE-52) cellulose and carboxy methyl-52 (CM-52) cellulose; FS+IE). Unfiltered samples served as controls. Semen ejaculates extended in Tris-citric acid (1:4) (n=16; initial motility 40-50%) were filtered at the rate of 1.5 ml/min under negative pressure at room temperature (28-30 degrees C). The mean recovery rate (%) of motile spermatozoa in the FS (85.9+/-1.51) and FS+IE (77.10+/-2.28) filtrates did not differ significantly. Percentages of sperm motility, normal acrosomes, and intact plasma membranes were highest (P<0.05) in FS+IE, intermediate (P<0.05) in FS and lowest (P<0.05) in controls at the three stages of cryopreservation (postfiltration final dilution, after equilibration, and after freezing). Mean sperm abnormalities were lowest (P<0.05) in the filtrates of FS+IE, moderate (P<0.05) in FS and highest in controls at all stages of freezing. Compared to dilution and equilibration, freezing greatly reduced (P<0.05) the overall percent motility, normal acrosomes and intact plasma membranes. The spermatozoa eluted through FS+IE columns proved more resistant (P<0.05) in bearing dilution, equilibration, freezing and thawing stresses than the spermatozoa from FS and control samples. It is concluded that filtration systems containing an FS+IE column can effectively enhance the quality and freezability of extended, low quality buffalo semen.