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Objectives: The EU decision to ban the use of antibiotic feed additives accelerated probiotic application in animal nutrition. Nevertheless, a sound scientific basis for the evaluation of conditions under which probiotics might be beneficial is largely missing. Therefore, we conducted a broad interdisciplinary approach (covering animal performance, microbiology, immunology, mucosal histology and transport kinetics) to investigate the modes of action of probiotics in pigs as well as factors influencing their effect and their contribution to animal health. Here we report the impact of four application variants on intestinal distribution and concentration of the probiotic, on the composition of the gut microbiota, on diarrhea incidence and on piglet performance.
Methods: Two probiotics of different ecological origin, Enterococcus faecium NCIMB 10415 and Bacillus cereus var. toyoi, were chosen as model organisms. Feed for sows during gestation/lactation and for piglets pre-/postweaning was supplemented with either of these probiotics. Furthermore, the probiotic was administered to piglets from birth on or just postweaning to evaluate in litters of untreated sows the effect of different starting points of E. faecium NCIMB 10415 initiations. To assess piglet performance body weight and feed intake were measured. Fecal consistency of weaned piglets was recorded daily. Luminal and tissue samples from stomach, jejunum, ileum and colon, respectively, were taken from nursed and weaned piglets of each group at the age of 14, 28, 35 and 56 days. Probiotic concentration in digesta and feces were monitored using colony hybridization with a strain specific probe. Total nucleic acids were extracted from digesta and feces of piglets as well as from sow feces followed by eubacterial PCR-DGGE and subsequent analysis of various criteria of microbial ecological. Additional, precaecal amino acid digestibility analysis was performed.
Results: If fed to sows and piglets, both probiotic strains were detected immediately after the start of the supplementation in feces of sows and piglets. Vertical transfer of both probiotic strains with sow feces to piglets could be demonstrated before suckling piglets had access to supplemented diets. Both probiotics were recovered from all intestinal segments of piglets. The concentration of the B. cereus probiotic increased by one order of magnitude after weaning, whereas the concentration of the E. faecium probiotic was not considerably increased after intake of supplemented feed by piglets. The dominant autochthonous microbiota of young piglets as revealed by denaturing gradient gel electrophoresis was more similar within than between treatment groups (control vs. probiotic). Both probiotics reduced the incidence of postweaning diarrhea (p < 0.05). For the E. faecium probiotic the relative magnitude of this effect was largely independent of dietary probiotic concentration or starting time of supplementation. Significant overall influence on piglet performance was observed only with the B. cereus probiotic, although preliminary results found an increased precaecal amino acid disappearance in piglets receiving E. faecium NCIMB 10415.
Conclusions: The results indicate that probiotics may be a contribution to healthy piglet rearing. Nevertheless, the magnitude of the effect seems to be strain dependent and influenced by so far undetermined animal-specific characteristics as well as exogenous farm- and time-specific factors.