Fertility using cooled semen
The components needed for fertility of cooled semen include:
- normal metabolism
- motility
- normal morphology
- ability to undergo capacitation and the acrosome reaction
- appropriate membrane lipids and membrane structure
- appropriate membrane proteins
- active enzymes
If any one of the above components are suboptimal, the semen will have reduced fertility. This is why it is important to pay attention to details when cooling and transporting semen for artificial insemination.
Many factors can effect the fertility of the cooled semen. The temperature and length of sperm storage have a large effect on the fertility of semen. In the next table, semen stored for 24 hr at 5°C has the same fertility as semen which has not been cooled or stored. Semen stored at 20°C for 24 hr has lower fertility. Fertility is estimated as the % of mares with embryo recovery from their uteri. In the mare, only fertilized and developing embryos are transported out of the oviducts into the uterus. Dead embryos or unfertilized oocytes remain in the oviduct and are eventually reabsorbed. The % mares with embryo's recovered is thus a measure of those mares in which fertilization successfully occurred.
Effect of Storage Temperature
| Storage (hr) | Temperature (°C) |
# mares | Embryo recovery (%)* |
0 |
37 |
68 |
59 |
24 |
20 |
68 |
38 |
24 |
5 |
68 |
60 |
| *embryos recovered at 7 days |
In the next table, fertility of cooled semen held 24 hr is similar to fresh unstored semen. When cooled semen is stored 48 hr, there is reduced fertility. Cooled shipped semen should then be used on the day it arrives from the semen supplier. A portion may be saved for the second day in case the mare has not yet ovulated. An alternative approach is based upon the observation that sperm which reach the oviduct and interact with oviduct cells can remain viable for up to 72 hrs. Thus some veterinarians suggest that all semen shipped should be inseminated on the day of arrival.
Effect of Storage Time
| Storage (hr) | Temperature (°C) |
# mares | Embryo recovery (%)* |
0 |
37 |
191 |
65 |
24 |
5 |
34 |
59 |
48 |
5 |
34 |
32 |
