Weaning is a complex step involving dietary, environmental, social and psychological stresses which interfere deeply with feed intake, gastro intestinal tract development and adaptation to the weaning diet. The first organ suffering from nutrient shortage immediately after the weaning is the gastro intestinal tract and this has dramatic consequences on its anatomy and functions, including barrier function against harmful antigens and pathogens. Therefore, addition of organic acids to the drinking water appears as critical for solving post weaning disorders.
The morphology of the piglet's gastrointestinal epithelia drastically changes at weaning. Villous height decreases and crypt depth increases; these changes appear to be induced by weaning and not by the creep feed offered at weaning. In the same time, there is a transient decrease in intestinal Lactobacilli and increase in coliforms.
A lot of just weaned piglets usually show a malabsorption syndrome known as non-infectious diarrhoea, which is characterised by increased excretion of fatty acids and carbohydrates in the faeces, watery stools and degenerative changes in the villi of the small intestine. In the majority of these cases, opportunistic pathogens take advantage of the presence of non-infectious diarrhoea and cause the post-weaning diarrhea syndrome (PWDS). The most important pathogens are:
1) TGE (Transmissible Gastroenteritis):
a) Caused by virus that belongs to a group called coronaviruses, and destroys digestive cells (villi) in pig’s intestines, thus no digestion/absorption, which can lead to diarrhoea.
b) The most deadly, and the most feared by producers.
2) Rotaviral diarrohea:
a) Caused by groups of rotavirus (groups A, B and C), and destroys the lining of the small intestine.
b) Rotaviruses are resistant to lipid solvents & many disinfectants, and they can survive for a long time.
3) Colibacillosis (E. coli):
a) Caused by certain E. coli strains that are classified as enteropathogenic, which can propagate rapidly, and produce toxins (enterotoxin).
b) Toxins can cause massive fluid and electrolytes losses from the body, and the result being a large amount of pale yellow, watery feces.
c) Its effects might be a secondary to the damage caused by TGE or rotavirus.
This major cause of these post-weaning disorders is that the weaned piglet lacks sufficient capacity to acidify its own stomach content by hydrochloric acid. Thus, the pH value in the stomach may stay at 4-5 for at least two hours after feeding, leading to suboptimal protein digestion and insufficient killing of microbes by low pH value. During this period, more than half of the dry matter already has been transferred from the gastric lumen to the duodenum; the resulting poor digestion and high bacterial count can easily lead to weaning diarrhoea.
Organic acids can simply be added to the drinking water with a dosing pump (see figure 3). The addition of organic acids to the drinking water increases the speed at which stomach contents reaches the optimal pH value of around 3, where the proteolytic enzyme pepsin has its optimum efficacy. Acidification also leads to lower gastric emptying which further contributes to an optimal digestion process. These mechanisms support the piglets in the stressful post weaning period and reduce the risk of having the post weaning diarrhoea syndrome.