Nov 17,2021
A healthy gut is essential for
efficient conversion of constituents for optimal absorption in animal nutrition
industry. Gut health is a complex process combining animal nutrition knowledge,
microbiology, immunology and physiology along with feed supplement knowledge.
When gut health is compromised in animal nutrition, digestion and nutrient
absorption are affected, which in turn has a detrimental effect on conversion
and production. This leads to economic losses and a greater susceptibility to
disease.
A characteristic feature of a
healthy gut is a large surface area covered with long healthy villi having deep
crypts. Deep crypts are indicative of rapid tissue turn over in order to permit
regeneration of damaged villi. Longer villi and deeper crypts provide a larger
surface area for the absorption allowing
efficient enzyme production and maturation of intestinal cells.
In commercial poultry and production, it is said that profit comes from
a healthy chicken. In animal nutrition industry healthy chicken comes from
healthy gut. Healthy intestinal villi leads to better absorption and animal
nutrition. Even if a high quality feed supplement is given to birds with damaged
or underdeveloped villi, desired performance cannot be achieved which is
important for profitability.
Under modern systems of
production using high quality feed supplement the poultry birds are inevitably
exposed to considerable stress during their productive lifetime. Post hatching
is a period of considerable stress. The gastrointestinal tracts of newly
hatched chicks are immature and sterile. The
GIT of the bird begin to develop
and function when the chicks start to ingest feed supplement alongwith feed. At
this stage, chicks are very susceptible to pathogenic microorganisms. Under
such circumstances, anti-microbial and the feed supplement such as antibiotics
are often used to suppress or eliminate harmful organisms in the intestine and
to improve growth and efficiency.
However, the use of antibiotics
as feed additives has been banned in the recent years in most countries due to
public health concerns over possible antibiotic residual effects and the
development of drug resistant bacteria. Several other countries are working to
reduce or ban the usage of antibiotics as growth promoters.
As a consequence, the development
of alternatives to antibiotics received considerable attention. Ideally,
alternatives to antibiotics should have the same advantageous properties in animal
nutrition. Isolated (amino acids, fatty acids, minerals, and vitamins), dietary
feed supplement (probiotics, prebiotics, symbiotic, organic acids,
antioxidants, and enzymes), and plant derivatives (polyphenols, herbs, and
spices) have been extensively studied in
search for alternatives.
As feed additive organic acids are appropriate
for in use to maintain gut health. These are natural products of the microbial
metabolism or fermentation of the carbohydrates in the intestines of animals.
Commonly known organic acids are acetic acid, propionic acid, butyric acid and
lactic acid. These are also known as volatile fatty acids (VFAS) or short chain
fatty acids (SCFAS).
Among these, butyric acid is an
organic acid with four carbons known for its ability to improve intestinal
health and can be consumed as feed supplement. It acts as a preferred biofuel
for epithelial cells lining the intestinal tract, which leads to increase in
the density and the length of villi thereby the enlargement of the absorptive
surface area of the intestine.
Butyrate, as a feed supplement, is
a preferred energy source for the
epithelial cells of the intestine. Different studies have proven that Butyric
acid as an improves performance, increases length of villi of intestinal mucosa
and digestive and absorptive capacity of the intestine in animal nutrition.
The crypt contains Ki67 cells,
which represent the proliferative stem cells of the intestinal epithelium. The
inclusion of Butyrate in animal nutrition increases the number of Ki67 cells
and has a beneficial effect on the villi absorptive surface and in the rate of
villi per plica.
During the process of
pathogenesis there is an interaction between bacteria and host cells where
Butyrate regulates the expression of invasion genes and decreases the virulence
of bacteria (Van Immerseel et al., 2004). It facilitates the creation and
maintenance of cellular tight junctions or zonula occludens (Peng et al., 2007)
which leads to better nutrient absorption and higher resistance in animal nutrition.
Researchers have also shown
Butyrate - a feed supplement to enhance disease resistance to Salmonella
enteritis and Salmonella typhimurium in chickens by inducing synthesis of
various HDPs (Sunkaraet., 2011).
In animal nutrition Volatile
Fatty Acids (VFAS) can inhibit the growth of bacteria under the group of
Enterobacteriaceae in (Salmonella,
Escherichia coli etc.). This is because the un-dissociated form of these acids
is strongly lipophilic, and able to diffuse across bacterial cell walls.
In an experiment, Galfi and
Neogardi (1995) found that the concentration of Butyrate required to reduce the
growth of E. coli by 50% is much lower than the concentration of the other
volatile fatty acids such as acetate and propionate.
The antibacterial activity of
Butyrate (when used as a feed additive) is selective as it kills pathogenic
bacteria and promotes the growth of beneficial bacteria. Butyrate lowers the pH
of the intestine, which favours the growth of lactic acid bacteria such as
Lactobacilli and Bifidobacterium Spp. as they require an acidic medium for
their growth.
In animal nutrition industry Butyrate
stimulates the production of VFAs and lactic acid in entire intestinal tract
which leads to acidification of digesta in the tract. This acidification
increases the calcium absorption from the intestine, in turn inhibiting phytic
acid from formation of calcium-phytate complex (Boling et al., 2000; Rafacaz
Livingston et al., 2005). Some authors have documented increased serum
phosphorus and magnesium levels in broilers and supplementation of Butyrate
(Adil et al;2010; Kamal and Ragaa, 2014).
The use of Butyrate as animal feed
supplement has been generally accepted as a tool to stimulate feed intake.
Butyrate stimulates insulin secretion, which in turn stimulates the entry of
glucose from blood into the cell. When the blood glucose level decreases, the
brain stimulates an increase in feed intake. Butyrate also promotes a more
efficient digestive process by enhancing the absorption of the various feed
additives through healthy villi. The increased absorption and utilization rate
of feed additive leads to a lower feed conversion Ratio. This has encouraged
the use of Butyrates as an feed additive.
Katoch and Tusdo (1984, 1985)
observed that the injection of Sodium Butyrate as a feed supplement in pigs
resulted in greater stimulation of pancreatic fluid secretions and increased
secretion of digestive enzymes like amylase and lipase.
Also, Katoch et al. (1989)
demonstrated that intravenous injection of Sodium Butyrate as a feed supplement
in calves resulted in higher secretion of pancreatic juice and greater release
of amylase than acetate and propionate. A positive effect on rumen papillae in
small ruminants was also observed during the consumption of this feed
supplement.
To overcome the corrosiveness and
rancid smell, salts of Butyric acid as a feed supplement, primarily sodium and
calcium butyrate, came into common use in animal nutrition. These salts are in
solid form and odourless, making them easier to handle. The main advantage of these type of Butyrates
in feed supplements is that they contain high levels of Butyric acid. However,
the problem with pure Butyrate salts in animal nutrition industry is that they are absorbed in the upper parts
of the GIT. This implies that the Butyrate activity is mainly in the upper part
of the digestive tract, with a very small impact in the intestine. This can be
overcome by coating the Butyrates to ensure its release in the intestinal area.
1. Coated Butyrates
2. Butyrins
3. Buffer Protected Butyrate
Coated products are typically
composed of beads containing Butyrate embedded in a protective matrix of
vegetable fat as a feed supplement. The rationale behind this protection is
that a significant part of Butyrate content will be released the moment lipase
is secreted in the duodenum, breaking down the lipid matrix in animal nutrition.
This implies Lipase requires an
activity time to break down the coating. This means that in order for the
Butyrate to be absorbed, there needs to be enough Lipase and enough time for
the Lipase to break down the coating. If these conditions are not met, the
coated Butyrate will pass further down the GIT and bel released in the hindgut
and eventually in the faeces.
Another common problem with
coated Butyrates is that the ability of the fat coating to withstand pelleting
temperatures is questionable, as generally feed supplement is pelleted at temperatures
higher than the melting point of fat.
Monobutyrins, dibutyrins and
tributyrins are composed of a glycerol backbone to which one, two or three
Butyrate units are bound, respectively.
As the availability of lipase in
chicks is limited, the Butyrate release from Butyrins is incomplete.
Butyrins, most advanced form -
Triglyceride, contains relatively high amount of butyric acid which is produced
by esterifying three molecules of butyric acid to a glycerol, resulting in
'tributyrin'. Thereby, for its release lipase has to cleave three ester bonds
for butyric acid in the intestine but the pancreatic lipase has been described
to preferentially cleave the ester bond of first and third butyrate, leaving
the second position intact (Brocherhoff, 2012).
Butyrins reliance on the presence
of Lipase and the lack of data on its heat stability makes it an uncompetitive
choice when choosing a Butyrate as feed supplement.
It is the most advanced
technology of enteric Butyrate at present.
In this form, the Butyrate salt
is protected by a physical chemical structure of buffering salts, where each
salt has a different pKa value. These salts prevent it from dissolving in the
initial part of the enteric system thereby ensuring that it reaches the
intestine.
This Buffer matrix protects
butyrate from solubilizing and dissociating in the initial part of the GIT.
Buffer protected forms also contain a higher level of Butyrate salt.
Buffer protected Butyrates have
been proven stable at pelleting temperatures.
In animal nutrition Butyric acid
is well known for its role as a feed supplement in gut health and as a major
energy source for epithelial cells of the villi. It helps regulate critical
functions of the intestine, maintaining integrity of the epithelial lining of
the intestine and enteric wall, promoting growth of villi and microvilli and
Improving the digestion and absorption of. Butyric acid protects intestinal
cells against pathogens, improves local immunity and promotes balanced growth
of beneficial microflora.
In Butyric Acids commercially
available forms, buffer protected Butyrate is found to be the most suitable option
for poultry feed supplement. The release of buffer protected Butyrate is not
dependant on Lipase, therefore enabling butyrate release in the intestine
through all stages of the life cycle. Buffer protected Butyrates remain stable
under pelleting and extrusion processes, making them appropriate for poultry
industry usage.