Dietary composition is a major factor influencing the intestinal microbial ecosystem of pigs. To alleviate
weaning-associated disorders, variations in dietary protein supply may beneficially affect microbial
composition in the gastrointestinal tract of piglets. A total of 48 piglets, fitted with simple ileal T-cannulas,
was used to examine the effect of protein supply of either highly digestible casein or less
digestible, fiber-rich soybean meal (SBM) on the composition of the intestinal microbiota. Gene copies of
7 bacteria groups were determined by real-time PCR in ileal digesta and feces. Ileal counts of total
eubacteria, the Bacteroides-Prevotella-Porphyromonas group, Enterobacteriaceae and Clostridium Cluster
XIVa were higher (P < 0.001) in the casein-based diets. Fecal counts of all analyzed bacterial groups were
higher for the SBM-based diets (P < 0.001), apart from Enterobacteriaceae (P < 0.05) which were higher
in the casein-based diets. Ileal counts of lactobacilli linearly increased as the crude protein level was
increased up to 335 g/kg (P < 0.01). The BacteroidesePrevotellaePorphyromonas group linearly decreased
in ileal samples (P < 0.01) and increased in fecal samples (P < 0.05) as the crude protein level in the SBMbased
diet was increased. Both, protein level and protein source may affect intestinal microbial balance.
Higher dietary protein levels in combination with diets low in fiber contents might stimulate proliferation
of protein fermenting bacteria in piglet’s large intestine. Further studies are warranted to clarify,
whether this would be associated with intestinal disturbances.