Microfluidic sperm selection improves sperm quality, fertilization, and cleavage normality, and blastocyst development in bovine IVF using semen with low or high sperm DNA fragmentation.

Sperm selection by density-gradient centrifugation (DGC) is widely used prior to bovine in vitro fertilization (IVF) but may affect sperm DNA integrity. Microfluidic sperm selection (MFSS) is a less invasive alternative; however, whether its effects depend on the initial level of sperm DNA fragmentation remains unclear. This study examined the effects of MFSS on sperm quality, fertilization status, first cleavage pattern, blastocyst development, ploidy, and bioenergetics using cryopreserved semen from Simmental bulls with low or high DNA fragmentation index (%DFI). Semen from 11 bulls was classified as low %DFI (<3.5%; n = 6) or high %DFI (>7.0%; n = 5). Sperm motility, viability, and %DFI were assessed before and after selection by DGC or MFSS. Selected sperm were used for IVF, and subsequent fertilization, embryo development, ploidy, oxygen consumption rate (OCR), and extracellular acidification rate (ECAR) were assessed. MFSS increased progressive motility and viability and reduced %DFI compared with DGC in both %DFI groups. MFSS increased normal fertilization and normal first cleavage while decreasing direct cleavage. Blastocyst development was higher with MFSS in both %DFI groups. Overall euploidy rates were comparable between DGC- and MFSS-derived blastocysts. MFSS-derived blastocysts showed higher OCR and ECAR than DGC-derived blastocysts. These results indicate that MFSS improves sperm quality, fertilization normality, first cleavage pattern, and blastocyst development in bovine IVF using semen with either low or high sperm DNA fragmentation. MFSS did not alter overall blastocyst ploidy but enhanced blastocyst bioenergetics.