Profitable and healthy piglet rearing starts with the proper development of intestinal flora and prebiotics to stimulate the growth of desired micro-organisms and reduce the presence of pathogenic bacteria in the intestinal tract. However, as intensive livestock husbandry is marked by an early weaning, the development of the gastro intestinal tract is already severely challenged in the first weeks of the young piglets’ life.
Piglet intestinal health issues
Piglets experience a sudden separation from the sow and subsequently suffer social stress by regrouping. In addition, a piglet’s digestive system is challenged by the change from milk to a solid diet. A piglet’s secretion of hydrochloric acid is not yet fully developed, while enzyme activity in the pancreas is strongly limited as a result of the stress experienced. The formation of villous atrophy in the small intestine is a further consequence.
A trial conducted by Hampson and Smith (1986) shows the villous length development of weaned and unweaned piglets (as shown in Figure 1 ). While supplementary feed has hardly any effect on the development of the villous length, unweaned piglets clearly show more pronounced villi. The underdeveloped villi as well as the limited activity of the digestive enzymes of early weaned piglets lead to an accumulation of undigested feed in the lower intestinal segments and supply an additional food source for micro-organisms.
Particularly the aggregation of undigested proteins increases the microbial ammonium production in the large intestine which causes a raise of the pH value. This leads to a rapid advance of the intestinal bacteria population and subsequently an increase of potential pathogenic germs.
As a result, the balance of the intestinal flora becomes extremely disturbed. During this phase of piglet production, the number of bacteria induced diarrhea cases is especially high. An increasing colonization of the digestive system by clostrida, E.Coli and other pathogenic germs causes diarrhea, diminished absorption of nutrients, bad growth and increases piglet mortality.
After, Stokstad et al. (1949) first observed that the supplementation of animal feed with Tetracyclin leads to an increased performance of broilers, the application of pharmaceutical growth promoters became a standard measure in the then modern agriculture. The sub-therapeutic dosages of antibiotics effectively suppressed the growth of undesirable pathogens in the intestine, leading to a significant reduction of illness in the young stock.
However, there is a decisive disadvantage of these antibiotic performance enhancers. They are believed to promote the origin of resistant strains of bacteria and stand in immediate conflict with practical human medicine and can, for example, lead to complications with the medication of patients.
As of January 1, 2006, antibiotics as animal feed additives have been forbidden in the European Union and the application is limited exclusively to therapeutic purposes (Biagi et al., in 2006).
A number of alternatives to antibiotic performance enhancers are available in piglet rearing and the application of prebiotic substances to prevent diarrhea is gaining in importance in young stock rearing. A prebiotic is a non-digestible food component that positively influences the host by stimulating the growth of one or several positive bacterial types in the large intestine and improves the host’s health (Roberfroid 1993).
Prebiotics are additives for which the animals have no own reduction enzymes and which hence survive the digestive processes in the gastro intestinal tract and moreover are not absorbed the small intestine. Instead of supplying living micro-organisms (probiotics), the supply with prebiotics specifically supports the beneficial bacteria already present in the digestive tract.
As a rule, prebiotics are carbohydrates (e.g. fructo- and galacto-oligosaccharides) which are used as an energy source by bifidobacteria and lactobacilli (Monsan and Paul, 1995). The colonization of the digestive tract by these micro-organisms is vital for the positive development of the micro flora and for an undisturbed growth of the animals.
Prebiotics also play an important role in nature. Breast milk, for example, contains about 130 different, indigestible oligosaccharides which serve as an energy source for the growth of lactic acid bacteria. These lactic acid bacteria prevent the attaching of pathogenic bacteria to the mucous membranes and can therefore play a crucial role in disease prevention (Rivero-Urgell and Santamaria-Orleans, 2001).
In the German market, products on the basis of fructo-oligosaccharides play a particularly important role in animal nutrition. Fructo-oligosaccharides are fermentable fibers which are available as direct energy source to specific colon bacteria (lactic acid and bifidobacteria) only in the large intestine.
The growth of lactic acid and bifidobacteria in the mucosa has additional interesting qualities. Some of the metabolic products, for example, have qualities similar to those of antibiotics and produce organic acids. These lower the pH value in the intestine and make the environment more difficult for pathogens (Wolter, in 1994). Fructo-oligosaccharides are an interesting possibility to build up a protective barrier in the intestinal tract of weaned piglets.
A new approach in this field is the application of specific acidifiers that not only have a preserving effect on feed, but also have a prebiotic effect in the piglets. The strategy is to make substrates available to specific micro-organisms to generate conversion products essential for the growth of the digestive system.
Gluconic acid, for example, is not or hardly absorbed in the small intestine of mono-gastric animals and therefore available for lactobacilli and bifidobacteria as a food source (Asano et.al., 1994). Due to the microbial fermentation of gluconic acid, lactates and acetates originate as byproducts. These are then converted to butyric acid by acid-utilising bacteria such as M. Elsdenii. Butyric acid is absorbed very quickly by the mucosa of the large intestine and acts as directly available energy source for epithelium cells and promotes their growth (Tsukahara et al., 2002).
In 2006 Biagi et al. were able to prove that the application of gluconic acid has advantageous effects on the growth performance of weaned piglets. The positive influence of gluconic acid on the health parameters of weaned piglets could also be confirmed in an additional testing.
In a trial with two piglet sets of 20 animals each, one group received, a specific, prebiotic acid and salt mixture on the basis of gluconic acid (product: PreAcid FL, Dr. Eckel GmbH) as a supplement to the normal feed ration.
Figure 2 shows the results of the trial. In comparison with the negative group, the supplementation with the prebiotic product led to a higher daily growth (DWG) of 4.2 percent. Additionally, the energy involved per kg of weight increase was reduced by 5.4 percent and the feed conversion (FC) was improved by 2.9 percent.
The results show that gluconic acid as prebiotic feed acid is an effective instrument to prepare young animals for the big challenges of weaning in piglet rearing.