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.
