Effect of Cryopreservation on Sperm Quality and Fertility

By A. Lemma. 2011

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Geographical barriers to breeding animals have long been reduced because of possibilities of semen transportation. In modern cattle breeding, where artificial insemination (AI) is the most widely applied tool facilitating extensive utilization of frozen semen from genetically superior sires, cryopreservation has been an invaluable technique. In order to extend the time span of the viability of spermatozoa, their metabolic rate has to be slowed down thereby reducing the rate at which substrates are used and toxins are produced. As a general rule cooling of spermatozoa is the simplest method that can successfully depress spermatozoal metabolic rate and therefore, prolong sperm survival. The use of carbon dioxide and other metabolic inhibitors like proteinase inhibitors are also known to produce a similar but less successful effect (Colenbrander et al, 2003; Cremades et al, 2005; Curry et al, 2000). Semen stored after cooling to 5-8°C will survive for 24-48 h without a significant decline in motility and even up to 96 h without a significant drop in fertilization rates. Though chilling semen provides an efficient and successful means of short-term storage, it has yet some adverse effects on the spermatozoa manifested as a depression in viability rate, structural integrity, depressed motility and conception rates (Batellier et al, 2001; Medeiros et al, 2002; Watson, 2000). Preferably, the spermatozoa of many species can now be stored indefinitely at -196°C in liquid nitrogen for future use, while still retaining acceptable fertilization rates postthaw. The techniques for successful cryopreservation of spermatozoa have also slowly progressed over the past several decades (Hammerstedt et al, 1990) and are now fairly standardized. However, cryopreservation is also known to be detrimental to sperm function and fertility even with the most up to date techniques. Generally, sperm viability is decreased by 50%, whereas fertilizing capacity is affected by a factor of sevenfold after cryopreservation (Lessard et al, 2000). The effects of cryopreservation on sperm function and fertility have been widely studied, particularly in bovine. Various sperm organelles have been known to be affected due to the detrimental effects of cryopreservation. Induction of premature acrosomal reaction, altered mitochondrial function, reduction of motility and failure of chromatin decondensation, all of which influence the viability and fertility of the sperm cells have been reported by different authors (Chaveiro et al. 2006; Cooter et al, 2005; Watson, 2000; Wongtawan et al, 2006). Cooling is a major stressor, as a result of which membrane bound phospholipids reorient themselves into a different configuration that disrupt membrane function and permeability

Subfields: Physiology, Public Health, Environmental and Occupational Health, Reproductive Medicine

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