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Conference abstract2004

Achievable objectives and limitations of fresh and cryopreserved semen

Söderquist, Lennart


Artificial insemination (AI) is a process of collecting semen, extending it with appropriate fluids for either short- or long-term preservation, and then placing it into the reproductive tract of sexually receptive females. By avoiding direct contact between animals, the risk of spreading infectious diseases is reduced. Artificial insemination used in a proper way increases the breeding capacity of the males, permitting a higher degree of selection and an extended use of animals with a high breeding value and has, throughout the last half century, substantially contributed to the breeding progress seen in farm animals. A prerequisite for the use of AI has been the development of procedures for semen preservation. Today long-term preservation of spermatozoa allows the banking of genetic resources, the exchange of genetic material across national borders and to help in conserving threatened or endangered species However, to be able to utilise AI in conservation biology, we need to gain a deeper knowledge of the influence of different steps in the processing and handling of semen from different species. Cryopreservation of semen involves subjecting the spermatozoa to a series of closely related steps like dilution and sometimes reconcentration, temperature reduction, cellular dehydration, freezing and thawing. A great variation is seen between species and individuals in how their spermatozoa can endure these different steps in the cryopreservation process. The accumulated cellular injuries that are seen are mainly caused by harmful formation of ice crystals and solution effects, resulting in a shorter life span in frozen-thawed semen than in its liquid-preserved counterpart. But the advantage is that cryopreserved semen can be stored for a very long time in a frozen state in liquid nitrogen (-196°C). Use of liquid (fresh) semen implies a somewhat simpler handling procedure and also gives higher fertility results. Disadvantages are the high demands on a fast distribution system, due to the short survival (often only some hours) of the diluted semen, and therefore it is more difficult to inseminate liquid semen at an optimal time. The use of cryopreserved (frozen-thawed) semen makes the planning of AI easier since deep-frozen semen can be stored in liquid nitrogen until use. The semen can then be thawed and inseminated at an optimal insemination time. Drawbacks are the more time-consuming semen processing and handling procedure, the need for more expensive equipment and often poorer fertility results. The beginning of a new life is the final result of a series of subtle changes and events. Besides finding successful methods and techniques to collect the semen that is to be used, there are many factors that can influence the fertility results. One prerequisite is to find means to detect the heat and ovulation time (which varies considerably between species) to be able to inseminate the female at the optimal time. This might involve the need to develop new methods to be able to detect necessary hormones or metabolites in i.e. blood or faeces. The site of semen deposition as well as that the AI-dose contains an appropriate number of spermatozoa of good quality (sperm motility and morphology) also influences the fertility results, and demands that optimal protocols and handling procedures are established for the species in question. Reports have shown that better fertility results can be achieved the further into the female genital tract that the semen is deposited. The laparoscopic technique (deposition of semen into the uterine horn) is, however, rather complicated and prohibited to use in unanaesthetised animals according to Swedish animal welfare legislation. The inseminator’s technical and hygienic performance of the AI and the stress that the female is exposed to during the time of insemination also adds to the factors that can influence the final fertility results. In conclusion, a careful planning is a prerequisite to be able to perform a successful AI programme. If we can develop suitable techniques to collect and process semen along with well adapted protocols, techniques and routines, which lead to an acceptable sperm viability and fertility, AI might constitute an alternative to natural mating and cryopreserved long time stored semen might contribute in conserving threatened or endangered species

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Publisher: CRU


Reproduction Techniques in Conservation Biology