Stillbirths
Stillbirths are usually recorded when they are found dead behind the
sow. However, this can be an erroneous assumption because there are three
possible causes:
i. Death before farrowing
ii. Death during farrowing
iii. Death after farrowing
If the pig dies before farrowing then depending on how long before, it
will show varying degrees of post-mortem changes including discoloration of the
skin and loss of fluids. If death occurs in early pregnancy a fully-formed
mummified pig will be seen. A pig that dies during the process of farrowing or
immediately afterwards will be fresh and normal. The vast majority of
stillbirths (80%) occur during the course of farrowing.
A good target level for stillbirths is 3 to 5% of total pigs born. At
this level there is no point in carrying out investigations because it is
unlikely that external inputs can alter the situation. However, once the level
exceeds 7% it is worthwhile carrying out an investigation by records and
post-mortem examinations. The following factors need to be considered as causal
or contributory to the problem:
- Stillbirths increase with the increasing age of the sow and beyond 5th parity may reach 20%.
- Individual sows can be identified by the sow litter card. The farrowing process should then be monitored.
- Stillbirths occur more often in larger litters.
- They are more common in pure breeds.
- Sows that have prolonged farrowings will have a higher number of stillbirths.
- Farrowing house temperatures above 24°C (75°F) increase the risk of stillbirths due to the difficulties of the sow panting and resting during delivery.
- Sows with uterine inertia and particularly if it is associated with calcium deficiency produce high numbers of stillbirths. One sow can make the average look bad.
- High carbon monoxide levels in the air associated with faulty gas heaters can raise stillbirth rates significantly.
- Pigs found dead behind the sow can sometimes be related to specific farrowing crates in certain rooms associated with draughts behind the sow, the pig dying shortly after birth due to hypothermia.
- An examination of records both by parity and total numbers born per individual litter, will clarify whether the problem is one of individual sows or there is an infectious or common environmental component.
- Stillbirths increase where there is a long gestation period and in such cases prostaglandin injections can be used. Use of prostaglandins has had various degrees of success.
- Lack of exercise may have an effect on the stillbirth rates.
Diseases of the sow such as fever, mastitis, acute stress can also
contribute to stillbirths.
