The physiological changes that occur around weaning occur whatever the weaning age although to some extent are reduced in the older the pig. In the ‘natural’ situation where the pigs wean themselves at eight to 10 weeks, these changes can be mild but in all other situations the risks are high.

This NADIS workshop in ‘Smaller Pig Producers Course 4’ looks at the problems encountered in the two weeks following weaning.

Why is Weaning a Problem?

Figure 1. Loss of condition and dehydration accompany post weaning scour

Figure 2. Condition loss can be severe and death will follow

Figure 3. Swollen eyes typical of bowel oedema

Figure 4. Fluid accumulation around the gut gives bowel oedema its name

Figure 5. Post-weaning scour can cause and be caused by poor hygiene

The gut of the piglet becomes colonised with a range of bacteria from birth and in the healthy piglet the established flora is maintained in balance by acquired immunity (from colostrum), ongoing protective milk based antibodies and the mixture of organisms competing for resources. The normal motion of the gut and voiding of faeces allows flushing of excessive bacteria and toxic by-products.

At weaning, many changes occur, which include:

1. Removal of protective milk antibodies
2. Change from highly digestible milk protein and sugars to solid feed often containing more complex nutrients requiring breakdown
3. Shrinkage of finger-like projections in the gut (villi) reducing digestive and absorptive surface area allowing nutrients to pass further down the gut into the large intestine where most bacteria reside
4. ‘Stress’ as a result of competition and change leading to reduced feed intake and gut stasis
5. Challenge of a new environment often with increased or altered microbial exposure

What are the Consequences?

All of these changes have a tendency to allow hindgut proliferation of E.coli – bacteria present as part of the gut flora – sometimes exacerbated by challenge of additional bacteria such as Salmonella. These E.coli release several types of toxins that disturb the natural fluid balance in the gut leading to fluid outpouring and ultimately scour, typically five to seven days post-weaning. The result is:

• diarrhoea (Scour)
• dehydration
• depression and inappetence
• weight loss
• death

In addition, other toxins produced by specific strains of E.coli bacteria are absorbed into the body causing toxaemia and rapid death.

Confounding Factors

In addition to the inevitable changes occurring at weaning, a number of management factors can exacerbate the problem:

1. Chilling – Low or variable temperatures and especially draughts tend to force the pig to redirect its blood supply away from the gut towards vital structures (heart, brain, etc.) leading to gut stasis which further allows microbial proliferation and toxin production
   
   
2. Feeding practice – The more digestible the diet the less nutrients pass into the lower gut on which bacteria thrive. Anything that affects digestibility adversely will precipitate scour. This includes:
   1. use of indigestible ingredients – raw cereals and complex vegetable protein
   2. stale and oxidised diets due to prolonged exposure to warm environments
   3. gorging – The provision of feed ad lib post weaning will encourage some pigs to gorge – compared to the more controlled milk supply from the sow. Small amounts provided little and often will reduce the risk

Oedema Disease (Bowel Oedema)

This is a very specific E.coli toxaemia occurring five to 10 days after weaning as a result of post weaning proliferation in the gut of strains of E.coli producing the oedema toxin.

Oedema is fluid accumulation in extra-cellular spaces. In this case, the oedema occurs in the abdomen and brain. Typically, the disease occurs in the best pigs at weaning, which may be found dead up to 10 days post-weaning. Individuals found alive are depressed, rarely scoured, have swollen eyelids and produce a high-pitched characteristic and unmistakable squeal.

Figures 3 and 4 shows typical post mortem signs. The triggers for oedema disease are exactly the same as these for post weaning scour but occur where specific E.coli stains exist and typically with later weaned piglets (five to six weeks). High feed intake and gorging are major triggers, hence the tendency for it to occur in the best pigs.

Action list for preventing post weaning scour

• introduce feed before weaning (creep feed)
• keep feed clean and fresh
• maintain high hygiene standards
• provide warm, dry and constant environment
• avoid draughts
• feed little and often, and
• only use highly digestible diets post weaning

Therapeutics

A wide range of pharmaceutical and nutraceutical products are available for use in weaned piglets aimed at reducing gut proliferation and reducing diarrhoea. They include:

1. organic acid incorporated in diets
2. enzyme use in diets to aid digestibility
3. probiotic incorporation – unpredictable results but can be of value in some situations
4. zinc oxide inclusion in diet – This can only be done under veterinary prescription and should only be incorporated in starter diets for two weeks post weaning at a level to give 2500ppm zinc. Note than zinc oxide can suppress appetite.
5. antibiotics

A note on antibiotic usage

The whole farming industry is coming under pressure to reduce the use of antibiotics and to use them responsibly. Clearly when pigs are scoured, rapid treatment is essential under veterinary direction ensuring the correct dose is delivered for the prescribed length of time. The choice of treatment should be determined with the help of bacterial sensitivity tests in the laboratory and by experience on the farm or holding. Unfortunately, some effective treatments have been lost over the years and two of the most effective currently available have huge implications for medical use. Fluoroquinolones (e.g. Baytril, Marbocyl) are only available for individual administration whilst colisitin is water-based oral treatment that is an important medicine for treatment of antibiotic-resistant bacterial disease in people.

Where scour is a predictable and repeating problem post-weaning, it may be appropriate to use targeted antibiotics in feed or water at weaning for a short period but this should only be done after attending to the environmental and management factors detailed and even then only with laboratory diagnostic support.

Vaccines

Despite attempts over many years to produce vaccines that will provide post-weaning protection, none is available. E.coli vaccines given to sows are highly effective at preventing neonatal scour but have no effect on the older piglet.

Conclusion

Post-weaning scour (and occasionally sudden death associated with oedema disease) is a common problem in the young recently weaned piglet.

By attending to the nutritional and environmental needs of the pig, many of the risks can be mitigated but where therapy is necessary this should be carefully selected, applied responsibly and not used to mask inadequate stockmanship.

Further Reading Find out more information on post-weaning scour by clicking here.