The Effects of Dietary Whey Lactose and Lactobacillus Agilis Bacteria on the Growth Performance, Physicochemical Conditions of the Digestive Tract and the Caecal Microbial Ecology of Broiler Chickens

The principal goal of this study was to assess the responses of broiler chickens raised on floor litter to the 2% dietary level of lactose (LAC) originating from dried whey fed in combination with live culture of Lactobacillus agilis bacteria (90 million cells/kg diet) in terms of the performance and basic postslaughter parameters, the lumen pH in some alimentary tract segments, concentration of volatile fatty acids (VFA ) in the total (T) and undissociated (UD) forms and count of selected microbial populations in the caeca determined by fluorescent in-situ hybridisation (FISH). A parallel aim was to evaluate the outcomes from the combined supplementation in comparison with feeding of LAC and the L. agilis bacteria as separate dietary supplements. Six hundred and forty Ross 308 chickens were placed in 16 floor pens (40 birds per pen having equal sex ratio) and were provided with free access to the feed (a mash maize-wheat-soybean meal-based diet) and water. Dietary treatments provided from day 8 to 42 of age were: LAC-free basal diet (CON), LAC-containing diet (CON + LAC), LAC-free diet with the addition of L. agilis (CON + BAC) and LAC-containing diet with addition of L. agilis (CON + LAC + BAC). The LAC supplementation caused significant decreases in the luminal pH of the crop, ileum and caeca, and the addition of the L. agilis bacteria reduced the pH in the crop and caeca. The overall concentration of total (T) volatile fatty acids was higher in the caeca of broilers receiving the LAC-containing diets. Both the LAC and the BAC supplements, independently from one another, resulted in significantly greater caecal levels of UD acetate, propionate and butyrate. The FISH analysis revealed that counts of Bacteroides sp./Prevotella sp. group were higher after the inclusion of LAC in the feed. All three dietary supplementations significantly reduced the total counts of the family Enterobacteriaceae and decreased the number of naturally occurring C. perfringens bacteria compared with the basal control diet (CON). Neither LAC inclusion nor BAC addition to the diet affected the counts of the Clostridium coccoides/Eubacterium rectale group. The synergistic effects of the simultaneous supplementation of LAC and L. agilis were found on the T butyrate concentration and on C. perfringens and the Enterobacteriaceae counts. No improvements in the body weight gains and post-slaughter traits were observed due to uncombined and combined supplementation with 2% LAC and L. agilis, indicating that the shifts in composition of the caecal microbiota toward a healthier composition by using these additives were not large enough to create the positive growth rate and processing yields responses in broilers maintained in a litter-floor environment.