Theriogenologists typically recommend low centrifugation speeds for separating equine semen from seminal plasma in ejaculate, as it was unknown whether higher speeds would damage the cells. However, higher forces did not damage sperm in a new study.

"There are some stallions that have low sperm concentration in their ejaculates and need to be centrifuged to concentrate the cells in a pellet and remove seminal plasma to achieve the desire dilution rate and/or concentration after adding the semen extender," said Jose A. Len, MVZ, MS, Dipl. ACT, clinical instructor of theriogenology at the Louisiana State University School of Veterinary Medicine.

Researchers collected semen from six stallions, and then measured its volume and sperm motility before diluting the sperm in a warmed extender. After extension, some samples were not centrifuged; others were centrifuged at three different speeds, re-suspended, and reassessed. All samples were cooled for 24 hours. After cooling, they checked the samples again.

They found that the higher speeds (up to 900xg) effectively separated the semen and increased recovery rate of the sperm. Processing semen might also aid preserving sperm cells for a short time (about 24 hours). However, Len added that not every ejaculate needs to be centrifuged–the noncentrifuged samples yielded the highest number of motile and viable sperm