Preliminary study of the microbial spectrum of the digestive tract in broilers fed diets with and without antibiotic supplementation

The predominant bacteria in the small intestine of broilers were Lactobacillus spp., Escherichia coli and Streptococcus spp. Compared with the antibiotic-supplemented group, experimental groups receiving mannan oligosaccharide, lactic acid bacteria, and organic acids contained more Enterococcus spp., Escherichia coli, Streptococcus spp. in the intestinal content. The predominant bacteria in the caecum were Escherichia coli, Lactobacillus spp. and Enterococcus spp. Unlike the other groups, no Clostridium spp. bacteria were found in the caecum of birds receiving antibiotic supplements. There was no effect of the type of acid (fumaric vs formic) in feed on the composition of intestinal microflora of chickens.


INTRODUCTION
The composition of intestinal microflora is influenced by the presence of bacteria, moulds, and yeast in feed and by the feed's particle size and physical form (Engberg et al., 2002;Knarrenborg et al., 2002). The planned ban on the therapeutic use of antibiotics in poultry nutrition has led researchers to look for substances that protect the digestive tract of birds against pathogenic bacteria (Verstegen and Williams, 2002).
The objective of this study was to determine the effects of mannan oligosaccharide, lactic acid bacteria, fumaric acid and formic acid given in feed on the microflora composition of the small intestine and caecum of broiler chickens.

MATERIAL AND METHODS
The composition of intestinal microflora was compared in 5-week-old ROSS broiler chickens fed diets with (ANT) and without (CON) antibiotic supplementation, and with supplemental mannan oligosaccharide (MO), lactic acid bacteria (LAB) and feed acidifiers in the form of fumaric acid (FUM) or formic acid (FOR). The broilers were fed a maize, wheat and soyabean meal diet supplemented with 0.5% premixes (BASF Kutno, Poland). The antibiotic feed contained flavofosfolipol (5 mg/kg), while the experimental feed contained mannan oligosaccharide (1 g/kg), lactic acid bacteria and fumaric acid (9.7 g/kg) or formic acid (11.8 g/kg). The bacteria originated from the Institute of Agricultue and Biotechnology in Warsaw. These were Lactobacillus paracasei KKP 824, Lactobacillus rhamnosus KKP 825, and Lactobacillus rhamnosus KKP 826 with an activity of 6.7 × 10 8 c.f.u./g, mixed at a 1:2:2 ratio, 3 million bacterial cells/ bird/day. Intestinal microflora was studied in 5 birds randomly selected from 160 birds of each group. Samples from the small intestine and caecum were taken for analysis under anaerobic conditions into sterile tubes and immediately brought to a laboratory. Analyses were performed at the Department of Clinical Microbiology of the Jagiellonian University Collegium Medicum Children's Hospital, following internal procedures.

RESULTS
The predominant bacteria in the small intestine were Lactobacillus spp. in all groups of birds (Table 1). Escherichia coli and Streptococcus spp. were 10 times less common. Traces of bacteria (Clostridium spp., Staphylococcus spp., Enterococcus spp. and Bacillus spp.) were found in the small intestine. The experimental groups contained more Enterococcus spp., Escherichia coli, Streptococcus spp. in the intestinal content. In chickens of both experimental groups, there were traces of Staphylococcus aureus, Proteus mirabilis and Klebsiella pneumonia. The dominant bacteria in the caecum were Escherichia coli, Lactobacillus spp. and Enterococcus spp. (Table 2). The concentration of Escherichia coli in the caecum was 100-fold higher on average than in the small intestine, and that of Lactobacillus spp. 10 times lower than in the small intestine. In the caecum, Enterococcus spp. bacteria were 10 times more numerous than in the small intestine. In all groups of birds, traces of Bacillus spp. were found in the intestines. The dietary antibiotic supplement eliminated Clostridium spp., including Clostridium perfringens, from the caecum. Acid type (fumaric vs formic) had no effect on the microflora composition of the chickens. to 1000 cfu +++ more than 1000 cfu 1/5-5/5 present in this number of birds/total number of birds tested The present results indicate that Lactobacillus spp. bacteria are predominant in the small intestine of broilers aged 5 weeks, while the type of supplement (including antibiotic) or its absence does not influence the presence of these bacteria. Withdrawal of the antibiotic from chicken diets increases the count of Streptococcus spp., Staphylococcus spp., and Proteus mirabilis in the small intestine. The content of Lactobacillus spp. in the caecum is the same regardless of the type of supplement (including the type of organic acid) used as a feed acidifier. Clostridium spp., including Cl. perfringens bacteria were found in the caecum of chickens receiving mannan oligosaccharide, lactic acid bacteria and organic acids, unlike in chickens receiving the feed antibiotic.

CONCLUSIONS
The replacement of an antibiotic with mannan oligosaccharide and lactic acid bacteria, and acidification of feed with fumaric or formic acid does not reduce Lactobacillus spp. and Escherichia coli in the digestive tract of broiler chickens. Intestinal microflora of the chickens is not differentiated by fumaric and formic acid used to acidify feeds in the presence of mannan oligosaccharide and lactic acid bacteria.