Evaluation of intestinal bacterial flora of conventional and organic broilers using culture-based methods

The major bacteria colonizing the intestinal tract (ileum and caecum) of organic (O) and conventional (C) chickens were counted, isolated and identified by conventional methods. Chickens were obtained from 7 conventional and 7 organic chicken farms (n=203). Intestinal sampling was performed at different ages, every 10 days, starting at 20 days until 40 and from 20 days to 80 days of age, respectively, for conventional and organic birds. Statistical analysis was performed on two separate data sets (40 days of age and all ages).The comparison of C vs O systems was analyzed with univariate and multivariate procedures. There were large differences in bacterial counts in relation to the portion of intestine, the rearing system and the farms. In the ileum of conventional birds Enterobacteria were higher than in organic birds (7.03 vs 6.09 CFUxlog/g; P<0.05), whereas the contrary was observed for Lactobacilli (6.75 vs 7.07 CFUxlog/g; P<0.05). With respect to the other microflora, the effect of farm probably masked possible differences. The effect of rearing system was more visible in the caecum than in the ileum: Enterobacteria levels were higher in C than in O chickens (7.42 vs 7.05 CFUxlog/g; P<0.01), whereas Enterococci (7.65 vs 6.55 CFUxlog/g; P<0.05), Lactobacilli (7.85 vs 7.31 CFUxlog/g; P<0.05) and total aerobia (8.12 vs 7.66 CFUxlog/g; P<0.01) counts were higher in organic chickens. Multivariate analysis of caecum microflora showed the possibility of discriminating the rearing system. In the ileum of conventional birds Enterobacteria and total aerobia increased with age, while Lactobacilli decreased. In the O system, Enterobacteria, Lactobacilli and total anaerobia showed a similar trend, whereas total aerobia and Enterococci showed the opposite trend. A similar situation was observed in the caecum. Further investigations are necessary to better assess the role and effect of the enteric flora on the productive performance and on the health status of reared chickens.