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See chapter 5 for additional information.

(213) The factors associated with abortion are complex, varied and often interrelated.
Fig.6-7shows the factors that contribute to abortions of either infectious or management factors.

Infectious agents can bring about abortion in three ways.

  1. They can invade the placenta, cause inflammation (placentitis) and perhaps necrosis, (tissue death)cutting off the nutrient and oxygen supply to the foetus.
  2. They can invade the foetus and kill it.
  3. They can multiply elsewhere in the body causing fever and sometimes toxaemia (toxins in the blood).
Toxins from mouldy feed can cause abortions. Strictly speaking they are not infections or bacteria but for completeness are mentioned here. The fungus can be at a low level in one of the feed constituents and barely detectable by visual examination and yet produce powerful toxins. These when ingested have toxic effects which may cause abortion. This form of fungal poisoning is called mycotoxicosis. The fungus may also be readily seen growing as a mould in feed lines, bags of feed or wet feed systems and their distributing vessels and pipes.

To prevent mycotoxicosis:

  • Always check your feed bins. Are they water tight?
  • When were they last inspected internally?
  • Do they contain bridged mouldy feed?
  • Are the bins filled with warm feed?
  • Do you regularly treat the bins to prevent mould growth.
  • Are the bags of feed kept in a dry cool or wet warm place?
  • If you practice home mixing and wet feeding are the tanks and pipes mould free?
  • Are you ever tempted to give feed to sows that has been slightly mouldy.
If you wet feed:
  • Do you check the roofs of your mixing tanks to see whether feed splashed on to them has gone mouldy.
  • Do you check the pipes?
  • Do you check the source materials?
  • Do you let liquid components of the mix sit around in hot weather in storage tanks?
The major infectious bacterial diseases which spread through herds and cause abortion are brucellosis and leptospirosis. (Fig.6-8). These infectious agents affect increasing numbers of sows in the herd with typical clinical signs of the disease. There is, however, a second group of bacteria which can be described as opportunist invaders which cause embryo mortality or abortion in individual sows and sporadically in small groups of sows. They do not spread through the herd like brucella or leptospira. They are often mixed infections (i.e. several different species involved).

If, however these opportunist bacterial infections occur in sufficient numbers of sows they can become a herd problem. They are often normal inhabitants of the vagina or the boars prepuce and their identification following pathological examinations needs careful interpretation. An emerging syndrome in this category occurs when high numbers of bacteria are deposited into the anterior vagina, particularly towards the end of the heat period, by the boar. Such bacteria include klebsiella, streptococci, staphylococci and possibly leptospira. In such cases careful clinical examination of sows between 14 and 21 days post mating will sometimes reveal a tacky discharge on the vulva, which may not necessarily be very obvious. Such sows should be identified, and if they are returning out of cycle, it is likely that embryo loss is taking place.

Low grade or chronic infections such as cystitis (infection of the bladder) and nephritis (infection of the kidneys) occasionally cause abortion. Lameness and pain, particularly from abscesses in the feet or leg weakness (osteochondrosis) can also cause the corpus luteum to regress due to stress. Bullying and fighting are often forgotten as predisposing factors in individual sows. Clinical observations and examination of records are important tools for investigation and the stockperson's opinions and observations are often invaluable.

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