Ileitis, a nagging gut health problem in pigs, is caused by the bacterium Lawsonia intracellularis. Vaccination is available as a solution, but it also pays off to understand when and why the bacteria can thrive. That helps to define pig diets in order to give L. intracellularis less chance, writes pig nutrition expert Dr Francesc Molist of Schothorst Feed Research.
Porcine proliferative enteropathy (PPE), often known as ileitis, is an important production intestinal disease with a huge economic impact. The prevalence of PPE is high (90%) and is caused by the Gram-negative intracellular bacterium Lawsonia intracellularis.
The bacterium invades immature intestinal epithelial cells, mainly in ileal crypts, leading to thickening and progressive proliferation of crypt cells.
The acute form, also known as proliferative haemorrhagic enteropathy (PHE), is most common in young adult pigs between 4 and 12 months of age and is characterised by bloody diarrhoea and sudden death.
The chronic form, also known as porcine intestinal adenomatosis (PIA) with symptoms such as anorexia, reduced growth performance and diarrhoea, is the most common form of PPE and occurs in growing pigs between 6 and 20 weeks of age. PIA infections, on the other hand, are often subclinical, with pigs showing no symptoms.
The exact mechanisms of spread are not known. Studies suggest that infected faeces are the major vehicle for movement of the organism around the farm.
Studies suggest that the organism can survive outside the pig for 2-3 weeks. To prevent this, disease management practices play an important role: good biosecurity and all in, all out procedures; wash out and disinfect pens between batches; avoid over stocking; reduce environmental stress and mixing of pigs. Vaccination might also be a possible solution but will also bring some costs associated.
In practice it is well accepted that during summer, especially on days that there is a big difference in temperature between day and night, outbreaks of ileitis in heavy pigs can occur. The mechanism underlying this phenomenon is not totally clear, but it can be speculated that it is linked to overeating. When pigs are exposed to high temperatures, they will reduce feed intake, when temperature drops at night or the next day, they will overeat to compensate.
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When pigs overeat the retention time of the digesta in the stomach is shortened, resulting in more substrate arriving at the end of the ileum and entering the large intestine. This excess of substrate might be used for L. intracellularis to over proliferate and cause an outbreak.
Therefore, it could be hypothesised that the proliferation of L. intracellularis could be prevented by limiting the amount of substrate arriving at the end of the ileum and entering the large intestine. Taking this into consideration the following feeding strategies could be advised:
In conclusion, in summer time when differences in temperature between day and night are bigger, pigs may tend to overeat. Overeating will increase the substrate arriving at the end of the ileum that can be used for L. intracellularis to proliferate. To avoid this, nutritionists should focus on formulating diets that will enhance stomach retention time and will reduce the substrate arriving at the end of the ileum.