Biomimetic Techniques for Improving Sperm Quality in Animal Breeding: A Review

Sperm quality in insemination doses is known to affect pregnancy rates following artificial insemination (AI) in a number of animal species. Furthermore, biotechnologies such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) require the spermatozoa to be removed from seminal plasma, which contains inhibitory substances, cellular debris and even pathogens. Several methods have been advocated to separate sperm cells from the rest of the ejaculate, and even to select the subpopulation of better quality spermatozoa by providing a physical barrier to the passage of abnormal, dead or dying spermatozoa. In this article, these methods are critically reviewed in the light of their suitability for use in the animal breeding industry, where requirements for efficiency, practicality and, above all, economy of the selection method are paramount. Colloid centrifugation, particularly the new "Single Layer Centrifugation" (SLC) technique, appears to be the most effective method both for separating spermatozoa from seminal plasma and for selecting the most robust spermatozoa. Furthermore, SLC can be scaled-up to enable large ejaculates to be processed easily.