The most natural way to preserve biological objects and products of biological origin is cooling or even complete freezing, which leads to slowing chemical and biochemical reactions. Preservation and restoration of the viability of biological objects (cells, tissues or whole organisms) after exposure to low temperatures is achieved due to a reversible decrease or cessation of metabolism, which is known as low-temperature anabiosis (suspended animation). This physiological state is often referred to as ‘hypothermia’. The need to preserve the sperm of farm animals for a certain period is associated with the emergence and development of artificial insemination technologies, since, first, it allows postponing artificial insemination and thus flexibly planning reproductive procedures, and, second, makes it possible to transport the genetic material. The first is especially important in fish breeding, as it allows solving the problem of non-simultaneous maturation of gametes in males and females during spawning campaigns.
The documented history of scientific research on hypothermic storage of sperm begins with the experiments carried out at the end of the 18th century by the Italian abbot Lazzaro Spallanzani, who cooled stallion, bovine and human semen in snow [36]. Studying the nature and properties of animal and human sperm, Spallanzani performed numerous experiments, including effects of low temperature on sperm motility. In his famous “Tracts on the natural history of animals and vegetables” (English edition 1803), Spallanzani described an experiment with cooling stallion semen in the snow: “Observing that the vermiculi had become motionless, I took the glass from the snow, and left it exposed to the air at 81° (degrees Fahrenheit; equals to +27.2 о С – author’s note). An hour later, it astonished me to find all the vermiculi (spermatozoa – author’s note) reanimated in such a manner as if they had just come from the seminal vessels”. Spallanzani obtained a similar result by cooling the semen of a bull and a human for 5—10 min in the snow.