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Reproduction | Cooled Semen

Cooled Semen

Artificial Insemination of cooled, transported semen

Breeding with cooled transported semen is a popular pastime, however it is fraught with difficulties and owners, mare managers and veterinarians all need to communicate extremely well to maximise the optimal fertility for mares bred this way.


Although the Arabs may have practised artificial insemination (AI) in both horses and humans BC (Bowen 1969), the first real record of investigation in this area was by Spalanzani in about 1776. In addition to his work with AI he found that by placing stallion semen in the snow he did not kill the "spermatic vermicules", but merely made them inactive and upon warming them their motility returned (Bowen 1969). It took centuries to exploit this finding and contrary to popular belief, it was the bovine industry that developed a commercial application for cooled transported semen prior to successful cryopreservation. Cooled transported semen is firmly entrenched and recognised throughout the world by various breed societies and is a technique that is becoming much more popular. 

Rapid cooling of spermatozoa causes irreversible damage, however cooling at an appropriate rate makes it possible to store spermatozoa for extended periods. A storage temperature of 50 C (refrigerator temperature) or 00 C (the temperature of iced water) are convenient temperatures to maintain and are less costly with the exception of ambient room temperature (usually 20-240 C). Metabolic rates increase as temperature increases unless chemicals are used to inhibit the reactions. Therefore reduced temperature has been the principal means of slowing chemical reactions thus extending the fertile life of spermatozoa. Obviously the longer semen can be stored and retain its fertility the more flexibility we have in collecting and transporting semen, selecting sires and synchronising breeding with ovulation.


1) Eliminates the cost and stress of mare and or foal transport.

2) The genetic pool is increased due to increased availability of stallions.

3) The use of genetically inferior stallions may be reduced.

4) Agistment costs for the mare are reduced and the owner has control over financial expenditure and other services such as veterinary examinations.

5) The likelihood of the mare being returned in poor condition, the foal contracting disease or other unfortunate circumstances such as injuries, are dramatically reduced and are directly under control of the owner.

6) The likelihood of disease transmission between farms is dramatically reduced.


1) Considerable technology and skill are required to appropriately collect, evaluate, extend and prepare semen for transport.

2) Costs for collection and transport are generally high.

3) Semen from some stallions will not be suitable for cooling and transport.

4) Owners in remote areas may not have the ability to determine the stages of the mares cycle or the veterinarian may not have experience to determine the appropriate time for breeding.

5) The amount of effort in communication between the veterinarian, mare owner and stallion manager is enormous and can be real headache in the middle of a busy breeding season.

6) There is considerable emotive involvement of clients. Cooled transported semen is unlikely to improve fertility and yet clients often become frustrated and upset if their mare fails to become pregnant in just one cycle.

Further information (in depth on breeding with cooled semen) can be obtained through this hyperlink. Beware the file will take about 30-40 seconds to load is complex. Only serious breeders that use cooled semen should bother reading it.

Another research article of ours on the types of containers and how the environmental temperature can effect their performance can also be accessed. This article highlights that transport temperatures could seriously harm the semen.