Comparison of sperm selection techniques in donkeys: motile subpopulations from a practical point of view

The aim of this study was to compare the postthaw distribution of motile sperm subpopulations, following simple or colloid centrifugation. A new analysis was used to evaluate the available number of sperm from each subpopulation after each centrifugation protocol. Frozen/thawed semen samples were divided into the following after-thawing treatments: uncentrifuged control (UDC), sperm washing (SW) and two colloid centrifugation procedures (Equipure, SLCE, and Androcoll, SLC-A). Percentage of total and progressive motility (TM and PM), as well as sperm motility kinematics, distribution of motile sperm subpopulations, and recovery rates, were statistically compared among treatments. The SLC treatments showed higher (P < 0.001) TM and PM than UDC and SW. Following each SLC procedure, different percentages of the subpopulation with the most vigorous and progressive sperm (sP4) were obtained. SLC-A recovered a larger number of sperm belonging to sP4 than SLC-E, but not significantly higher than SW. From a practical point of view, sperm washing, the standard centrifugation procedure for equine semen processing, recovered the same amount of fast and progressive sperm as colloid centrifugation, apparently the best treatment according to traditional analysis. In conclusion, samples processed by SLC have higher motility percentages than SW and UDC but, after combining the available number of sperm, SLC and SW techniques are equally efficient in recovering sperm from the most vigorous, fast and progressive motile subpopulation (sP4).

Comparison of sperm selection techniques in donkeys: motile subpopulations from a practical point of view

The aim of this study was to compare the postthaw distribution of motile sperm subpopulations, following simple or colloid centrifugation. A new analysis was used to evaluate the available number of sperm from each subpopulation after each centrifugation protocol. Frozen/thawed semen samples were divided into the following after-thawing treatments: uncentrifuged control (UDC), sperm washing (SW) and two colloid centrifugation procedures (Equipure, SLCE, and Androcoll, SLC-A). Percentage of total and progressive motility (TM and PM), as well as sperm motility kinematics, distribution of motile sperm subpopulations, and recovery rates, were statistically compared among treatments. The SLC treatments showed higher (P < 0.001) TM and PM than UDC and SW. Following each SLC procedure, different percentages of the subpopulation with the most vigorous and progressive sperm (sP4) were obtained. SLC-A recovered a larger number of sperm belonging to sP4 than SLC-E, but not significantly higher than SW. From a practical point of view, sperm washing, the standard centrifugation procedure for equine semen processing, recovered the same amount of fast and progressive sperm as colloid centrifugation, apparently the best treatment according to traditional analysis. In conclusion, samples processed by SLC have higher motility percentages than SW and UDC but, after combining the available number of sperm, SLC and SW techniques are equally efficient in recovering sperm from the most vigorous, fast and progressive motile subpopulation (sP4).(AU)

Practical implications of sperm selection techniques for improving reproduction

Sperm selection techniques are needed to separate spermatozoa from seminal plasma and extender for in vitro fertilization (IVF) and to improve sperm quality for a range of assisted reproduction techniques. Apart from sperm washing, which removes some but not all of the seminal plasma, the selection techniques that are currently used are mainly swim-up and colloid centrifugation; filtration through Sephadex columns or glass wool is seldom used in the field. Although swim-up can be used to prepare sperm samples for IVF, the low recovery rate and lack of selection for sperm qualityother than motility make this technique ineffective for routine use. Colloid centrifugation is used to prepare semen for all types of assisted reproduction. The method has been scaled-up for voluminous ejaculates e.g. from stallion and boar, and scaled-down to accommodate small volumes of thawed semen (e.g. from bull). Sperm quality and fertility are improved, as shown in laboratory assays and in various fertility trials. Some normal spermatozoa are lost during the selection process but overall the advantages of improved longevity and fertility in the selected spermatozoa outweigh the disadvantages. Since spermatozoa are separated from bacteria in the ejaculate, it may be possible to reduce antibiotic usage in semen extenders. New applications of colloid centrifugation include extracting camelid spermatozoa from viscous seminal plasma, selecting spermatozoa with condensed chromatin (i.e. with fewer free thiols), and using the number of spermatozoa passing through the colloid as a diagnostic tool to indicate male fertility.

Practical implications of sperm selection techniques for improving reproduction

Sperm selection techniques are needed to separate spermatozoa from seminal plasma and extender for in vitro fertilization (IVF) and to improve sperm quality for a range of assisted reproduction techniques. Apart from sperm washing, which removes some but not all of the seminal plasma, the selection techniques that are currently used are mainly swim-up and colloid centrifugation; filtration through Sephadex columns or glass wool is seldom used in the field. Although swim-up can be used to prepare sperm samples for IVF, the low recovery rate and lack of selection for sperm qualityother than motility make this technique ineffective for routine use. Colloid centrifugation is used to prepare semen for all types of assisted reproduction. The method has been scaled-up for voluminous ejaculates e.g. from stallion and boar, and scaled-down to accommodate small volumes of thawed semen (e.g. from bull). Sperm quality and fertility are improved, as shown in laboratory assays and in various fertility trials. Some normal spermatozoa are lost during the selection process but overall the advantages of improved longevity and fertility in the selected spermatozoa outweigh the disadvantages. Since spermatozoa are separated from bacteria in the ejaculate, it may be possible to reduce antibiotic usage in semen extenders. New applications of colloid centrifugation include extracting camelid spermatozoa from viscous seminal plasma, selecting spermatozoa with condensed chromatin (i.e. with fewer free thiols), and using the number of spermatozoa passing through the colloid as a diagnostic tool to indicate male fertility.(AU)