What, No Piglets?

Michaela Giles investigates the huge topic of infertility in pigs, and provides a practical overview of the problem and its many and varied causes

- Michaela Giles

There are two types of infertility that can affect pigs, infectious and non-infectious, These are sometimes described as acute reproductive problems and chronic reproductive problems respectively, although there is some overlap. While the outcomes of either may be similar, the root causes are quite different, and will usually have different diagnoses and responses.

Farmers are often keen to blame a chronic condition with an infectious cause, as there’s a clear management pathway for known infectious causes. However, this is rarely the case. Chronic causes may be also harder to isolate and, possibly, will have a few varied origins leading to a cumulative infertility response.

Infectious causes

Broadly speaking, acute reproductive problems are usually described as the sudden onset of problems associated with abortions, stillborn pigs or premature litters. These all usually have an infectious cause (viral, bacterial or parasitic), as illustrated in Table 1.

Infectious organisms can bring about abortion in three ways.

By invading the placenta, causing inflammation and possibly necrosis (tissue death), effectively eliminating the nutrient and oxygen supply to the foetuses.

By invading the foetuses and killing them.

By multiplying elsewhere in the body, causing fever and, on occasions, toxaemia (toxins in the blood).

Additionally, there’s a second group of bacteria which can be described as ‘opportunist invaders’, which have the ability to cause embryo mortality or abortion in individual sows and, sporadically, in small groups of sows – they do not spread through the herd and are often mixed infections (i.e. several different species involved).