Mode of action of Bacillus subtilis and efficiency in piglet feeding

Trial No. Temperature before expansion after expansion Mean counts (Log 10 cfu/g) Trial 1 100°C 5.70 5.63 Trial 2 105°C 5.64 5.62 Therapeutic antimicrobials are regularly used in pig diets to prevent and treat disease and as a consequence improved daily gain and feed utilisation can be observed (Barton 2000). Despite their beneficial effects, the recent concern on drug residues in food and the potential transfer of antibiotic resistance to human pathogens open discussions towards alternative solutions such as probiotics. Probiotics are live cultures of harmless bacteria or yeast species that equilibrate intestinal micro flora to the benefit of the animal (Fuller 1989). Most known probiotics are not able to survive applied technology in feed production, e.g. heat administration. One way to overcome these problems is the use of spore forming probiotics, particularly Bacillus subtilis. The admission of B. subtilis to piglet feed has several pathways in which it may improve production parameters. B. subtilis consumes oxygen in the gut tract and additionally it produces certain enzymes like subtilisin and catalase. This results in a positive environment for beneficial bacteria such as Lactobacilli. Lactobacilli colonize the gut mucous membranes and block adhesion sites for pathogens, a mechanism known as competitive exclusion. Besides, Lactobacilli produce lactic acid, which reduces the amount of pathogens such as Salmonella, E. coli, Campylobacter and Clostridium (Hosoi et al. 2000). Numerous trial results are available on the reduction of these pathogens by B. subtilis (Maruta et al. 1996, Fritts et al. 2000, Ragione and Woodward 2003). An interesting observation is that not only a reduced number of infected animals were reported, also the amount of pathogenic bacteria in the faeces of the positive animals was reduced (Maruta et al. 1996). For practical use the compatibility with further feed supplements such as organic acids and antibiotics for therapeutic use as well as resistance for pelleting temperatures up to 90°C are important. B. subtilis as a spore forming bacteria is in an inactive, stable state and under optimal conditions able to sporulate and to multiply itself in a vegetative state (Hongh et al. 2004). Determination of effects of heat administration and pelleting on survivability of B. subtilis C-3102 were recently described (Nollet 2005). New own trials are confirming superior survivability under expansion conditions up to 105°C too (Table 1). Compatibility of B. subtilis C-3102 to 13 different relevant feed agents was measured in vivo and examined as good (Enthoven and van der Lee 2004). On the basis of the presented data on usability, in the following the effects of B. subtilis C-3102 on performance parameters in piglets will be discussed. Mode of action of Bacillus subtilis and efficiency in piglet feeding