Single Layer Centrifugation with 20% or 30% Porcicoll separates the majority of spermatozoa from a sample without adversely affecting sperm quality

Centrifugation of boar semen through one layer of 40% colloid (Porcicoll) was previously shown to separate spermatozoa from bacteria without having a detrimental effect on sperm quality. However, some spermatozoa were lost. The purpose of the present study was to determine whether 20% or 30% Porcicoll could be used to recover most of the spermatozoa without impacting on sperm quality. Insemination doses (n = 10) from a commercial boar station were sent to the laboratory at the Swedish University of Agricultural Sciences and processed by Single Layer Centrifugation with 20% and 30% Porcicoll approximately 7 hr after semen collection. The resulting sperm samples and controls were evaluated for sperm quality immediately and again after storage at 16-18 degrees C for 4 and 7 days. Sperm recovery was 94 +/- 18% and 87 +/- 15% for 20% and 30% Porcicoll, respectively (p > .05). Sperm mitochondrial membrane potential and chromatin integrity were unaffected (p > .05). The proportion of live spermatozoa producing superoxide (9 +/- 8%, 7 +/- 6% and 3 +/- 1%;p < .05), and the proportion of spermatozoa with high stainability DNA (0.68 +/- 19%, 0.61 +/- 0.22% and 0.96 +/- 0.23%;p < .05- <0.01), were marginally increased whereas membrane integrity, although high, was lower in the centrifuged samples than in the controls (82 +/- 8%, 83 +/- 5% versus 92 +/- 4%;p < .05). In conclusion, centrifugation through 20% or 30% Porcicoll enables most spermatozoa to be recovered, without having a major effect on sperm quality. These results are encouraging for further studies involving microbiological investigation of the processed samples, and scaling-up to process larger volumes of boar ejaculates.