Part of the book: Artificial Insemination in Farm Animals
Colloids have been used for several decades to prepare spermatozoa for assisted reproduction, initially for in vitro fertilization but, with the development of scaled‐up techniques, increasingly for artificial insemination and cryopreservation as well. The colloids usually consist of coated silica particles. Using colloid centrifugation, it is possible to select sperm subpopulations consisting of motile spermatozoa with intact membranes, stable DNA and normal morphology and to separate them from the rest of the ejaculate. This review explains why different protocols for colloid centrifugation are needed for different species, as well as species‐specific colloid formulations, to match the physical characteristics of the semen. The advantages and disadvantages of sperm preparation by this technique will be outlined. An emerging area of interest is the ability to separate spermatozoa from the bacteria that contaminate semen during collection. Thus, colloid centrifugation represents an alternative to using antibiotics in semen extenders. Since there is a worldwide movement to restrict the use of antibiotics, the possibility of physically removing the bacteria is of considerable interest. Moreover, it may be possible to use colloids to reduce viruses in semen. Transmission of viruses through semen is an emerging problem as more and more viruses are being identified that can potentially be spread in this manner.
Part of the book: Advances in Colloid Science