Development of antibiotic resistance and options to replace antimicrobialsin animal diets

As there is a risk of developing antibiotic resistance, a number of commonl y-used antimicrobial growth promoters have been banned in the EU member sta tes. This decision has put new emphasis on using the diet to control enteri c bacterial infections of pigs. Dietary carbohydrates constitute a major pr oportion of diets for pigs, and the carbohydrate fraction has a diverse com position, with different properties in the gastrointestinal tract, some of which are of importance to gut health. Findings from different studies indi cate that dietary carbohydrate composition influences the expression of swi ne dysentery and infection with nematode worms after experimental challenge with Brachyspira hyodesenteriae and Oesophagostumum dentatum respectively. In both cases the type, amount and physico-chemical properties of the carb ohydrates entering the large intestine played an important role in the infe ction, and emerging data suggest a synergism between different porcine path ogens. There is also increasing evidence that the feed structure, which rel ates to the type of plant material in the diet and the way it is processed, can be used to reduce Salmonella prevalence at the herd level. However, it should be stressed that using the diet to manage gut health is not straigh tforward, since the expression of a pathogen in many cases requires the pre sence of other components of the commensal biota.