Report of a trial in Bulgaria testing the effects of a mixture of probiotics, yeast and organic on the growth and gut health of broilers. The experimental mixture resulted in a shift in the microbial balance in the gastrointestinal tract in favour of Gram-positive bacteria. There were also significant emprovements in both final weight and feed conversion
It is known that the disorder in the compostion of normal gastrointestinal microflora in animals can lead to excessive proliferation of E. coli and coliform baceria, followed by various pathoglogies. A diet of skim milk powder, soybean meal or fishmeal has high acid binding or buffer capacity. This attribute, together with high intestinal pH, allows pathogenic Gram-negative bacteria such as E.coli and coliform bacteria to colonise the digestive tract causing inflammation and digestive disorders, so the gut absorbs fewer nutrients.
Balancing the gut microflora
In stressed birds, the number of E.coli in the gastrointestinal tract increases together with intestinal pH, thus decreasing Gram-positive microflora and producing dysbacteriosis of Gram-negative pathogenic bacteria that colonise intestines, cause inflammation of intestinal mucosa, decreasing the absorption of nutrients and stunting the growth of birds.
In some instance, the continuous administration of high doses of antibiotics or the use of sub-therapeutics or the use of sub-therapeutic doses of antibiotics was followed by dysbacteriosis and infection with Proteus, Pseudomonas and Aspergillus spp. As well as Candida albicans and other pathogens. A level of E.coli of more than 300.000/m3 air causes microbial stress and may lead to an outbreak of colibacillosis in chickens.
In recent years, numerous studies have been carried out, with the aims of normalising the intestinal microflora composition and preventing the animal’s gastrointestinal tract from being colonised by pathogenic organisms. The activities of Lactobacillus bugaricus and Streptococcus thermophilus were found to inhibit enteropathogenic E.coli in vitro. It is sometimes recommended to supplement poultry feeds with lactic acid, bacteria and yeast at times of stress. Some data has demonstrated that an acid environment (pH 3.5-4.0) favours the development of lactobacilli and inbibits the replication of E.coli, salmonella and other Gram-negavite bacteria known to cause gastrointestinal diseases. Acidic additives are especially useful for young animals because they reduce the Gram-negative bacteria and increase the Gram-positive organisms, leading to improvements in the health and weight gain of the animal. A combination of organic acids and probiotics has had synergistic influences on these two parameters in broiler chickens.
Previous work in Bulgaria
We have found out that lactic acid bacteria (L. bulgaricus) and Str. Thermophilus inhibited E.coli, S. enteritidis, St. aureus and Listeria monocytogenes. The inhibitory effect was measured by the diameter of the sterile zone around the well containing the probiotic. The suspension experiment revealed that this probiotic inhibited the count of the aforementioned pathogens by up to 99% in combined vultivation. All this is important for the colonisation of the gut with pathogenic micro-organisms and their adherence to intestinal mucosa epithelium.
The results of our studies showed 4% citric acid and 4% tartaric acid inhibited the growth of several Gram-negative bacteria such as E.coli, Proteus spp, Pseudomonas spp, S, entiridis and some Gram-positive organisms like L. monocytogenes and St. aureus. These organic acids reduce considerably the contamination of litter with such organisms and simultaneously, neutralise ammonia production. At the same time, the balance between Gram-positive and Gram-negative micro-organisms is optimised and the risks of re-infection and microflora imbalance are diminished.
The data from our experiments showed a huge inhibiroty effect over the 90% on the E. coli count in the feed. The highest effect recorded was more than 99% in the probe with the probiotic mixture, which was though to be due to a synergism between the active componenst. There was a correlation between this effect and a lo pH.
The latest study
The trial, with a total of 60 birds, showed that Gram-positive bacteria accounted for only 10% of the microbial microflora, while Gram-negative organisms made up 90% of the microflora in the control group of broilers. In the experimental group, treated with probiotic (3% lactic bacteria plus 1% bakers yeast) plus organic acid (0.7% citric acid) in the feed troughout the growing period, Gram-positive bacteria predominated (77-80%). The control birds had between 3 and 5 times more E. coli per gram of colon that the experimental birds at 20 and 42 days of age. They also had a coliform count at 20 days that was more than six times that of the treated birds and a yeast count of between 12 and 250 times higher than the birds receiving the combined probiotic mixture.