Physiology and biochemistry of ram sperm in relation to its preservation

Incubation of mammalian sperm in vitro at body or room temperature leads to a loss of motility and metabolic activity due to exhaustion of substrates and accumulation of inhibitory by—products, such as lactic acid or lipid peroxides (reviewed by Mann and Lutwak-Mann, 1981). It is therefore desirable to lower the temperature at which sperm are stored, in order to lower their metabolic rate and increase their longevity. The first demonstration that sperm could be successfully stored outside the body after cooling is attributed to Lazaro Spallanzani (1776) who noted that human, stallion and frog sperm were immobilised by cooling in snow, but regained their motility upon subsequent rewarming. The widespread use of frozen sperm for artificial insemination was foreseen by Mantegazza (1866), but this did not become a reality until the mid twentieth century, and the discovery that sperm could be protected from the effect of cold shock by egg yolk (Phillips, 1939), and from freezing damage by glycerol (Polge et al, 1949)