LAUSR

Intracytoplasmic sperm injection (ICSI) is a feasible technique for in vitro embryo production and optimization of stallion sperm utilization. The efficient use of frozen-thawed sperm can be improved by refreezing [1], which is an option for stallion sperm when availability is limited [2] and a method that has been successful in other species, including human and bovine [3,4]. Stallion sperm can be cryopreserved using extenders that contain skim milk, egg yolk, and glycerol as cryoprotectants [5]. Most freezing extenders include glycerol, although it causes injury to cells during the freezing process [6]. The use of amides as cryoprotectants, such as methylformamide and dimethylformamide, improve frozen sperm quality and fertility [6]. Sperm sorting methods used for ICSI are primarily based on motility, which is often decreased after reprocessing [6]. Visual selection of a single sperm for ICSI is a viable option, although the presence of particles from extenders can limit the ability to observe sperm that have not been through a sorting procedure and make sperm manipulation more difficult during ICSI. The aim of this study was to evaluate if filtering extenders prior to refreezing results in similar sperm quality parameters, while reducing particulate matter and allowing better imaging of sperm prior to selection for ICSI.