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Feed enzymes and betaine in antibiotic free poultry diets. |
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Author: Drs. Lucy Tucker, Craig Wyatt and Michael Bedford, Finnfeeds, Marlborough, Wiltshire, UK
The following article is a special collaboration from AFMA (Animal Feed Manufacturers
Association) www.afma.co.za
We thank their kind support.
The benefits of feeding antibiotic growth
promoters
AGPs have a long history of prophylactic use in animal feed, where they contributed
to improved animal performance and health status by targeting and destroying the
intestinal microflora. They can achieve this through several mechanisms: interfering
with the bacteria's ability to reproduce, damaging cell membranes or disrupting
essential cellular activities . Most AGPs target gram-positive organisms that
are commonly associated with poor health and reduced animal performance. The economic
benefit of feeding prophylactic AGPs can be hard to quantify in individual crops
of animals, but analysis of long-term effects has provided evidence of their value
in improvement of growth, health and uniformity. The size of response to AGPs
is dependent on farm management, exposure to pathogens, environmental stresses
and diet. The poorer the conditions the animals are grown under, the greater will
be their response to AGPs.
The benefits of feeding antibiotic growth promoters
AGPs have a long history of prophylactic use in animal feed, where they contributed
to improved animal performance and health status by targeting and destroying the
intestinal microflora. They can achieve this through several mechanisms: interfering
with the bacteria's ability to reproduce, damaging cell membranes or disrupting
essential cellular activities . Most AGPs target gram-positive organisms that
are commonly associated with poor health and reduced animal performance. The economic
benefit of feeding prophylactic AGPs can be hard to quantify in individual crops
of animals, but analysis of long-term effects has provided evidence of their value
in improvement of growth, health and uniformity. The size of response to AGPs
is dependent on farm management, exposure to pathogens, environmental stresses
and diet. The poorer the conditions the animals are grown under, the greater will
be their response to AGPs.
The effect of nutrient flow in the ileum on microbial populations
Like all organisms, microbes need a supply of nutrients and a suitable environment
to inhabit (e.g. the caeca). It has been known for many years that the diet fed
to the host animal influences microflora development and distribution. Feeding
high viscosity cereal grains to broilers, such as wheat and barley, has been shown
to result in larger microbial populations in the ileum compared with low viscous
corn-based diets (Hofshagen & Kaldhusdal, 1992; Wagner & Thomas, 1987).
Similar effects have been observed in broilers fed corn diets supplemented with
pectin (to artificially raise viscosity), where rate of digestion was reduced
in the pectin diets (Schutte & Langhout, 1999). This was especially pronounced
in the broilers with normal microflora populations. Viscous diets respond particularly
well to inclusion of AGPs and other feed additives such as enzymes (Elwinger &
Teglof, 1991; Vranjes & Wenk, 1997). A viscous environment slows down digestion
processes, and encapsulates nutrients, making them inaccessible to digestive enzymes.
Viscous gels are formed in the digesta by the non-starch polysaccharides (NSP)
arabinoxylan and betaglucan, which cannot be digested by the animals own enzymes,
and so have been a major target substrate in the development of feed enzymes.
Unlike the field of ruminant nutrition, monogastric nutrition often neglects the
impact of diet on intestinal microflora development and the consequential effect
on the host animal. VFAs from bacterial fermentation can be a source of energy
for the host. Efficiency of digestion is considered to be the key to microflora
development. When digestive conditions are optimised by feeding a good quality
diet with low stress (disease, heat) levels, the high rate of nutrient digestion
and absorption from the intestine limits the amount of nutrients passing to the
caecal microflora for fermentation. This restricts the growth and colonisation
of microbial populations in the intestine. When digestion is inefficient due to
poor raw material quality or gut wall damage, more starch and protein escape ileal
digestion, and flow to the lower intestine where they 'feed' the microflora, encouraging
proliferation. If there is a change in relative substrate levels (e.g. higher
starch and protein compared to fermentable fibre) certain bacterial populations
may be encouraged, changing species balance and dominance (Wagner & Thomas,
1987) that may initiate intestinal disorders (Deloyer et al, 1996). This occurs
especially in high viscosity, heat-damaged starch and protein diets (Vahjen et
al, 1998). Poor digestion can induce physiological adaptations in the animal,
in an attempt to improve nutrient uptake, e.g. increased pancreatic enzyme secretion,
gut length and surface area (Angkanaporn et al, 1994; Brenes et al, 1993).
Finnfeeds enzymes have been tailor-made for different species (e.g. broilers,
pigs) and main dietary components (e.g. corn-soy diets) and are specially formulated
to increase nutrient digestibility in the ileum. They reduce digesta viscosity
and water holding capacity through breakdown of NSPs (arabinoxylan and betaglucan),
starch and protein. Surveys on the most commonly used raw materials in feeds have
revealed that variability in broiler performance is of a similar magnitude between
wheat, barley and corn, with 0.043, 0.039 and 0.042 standard deviation in FCR
respectively (Finnfeeds own data; Leeson et al, 1993). This demonstrated that
corn-soy diets are not always delivering best animal performance, and have the
same scope for improvement as viscous cereal diets. Feed enzymes can improve overall
diet digestibility with greater effects on lower versus higher digestible diets,
giving corresponding improvements in uniformity of animal performance. As well
as improving digestion and absorption in the ileum limiting the nutrients available
for microfloral utilisation, fermentation of NSP subunits (liberated by feed enzymes)
produces the VFA butyrate, which increases villi growth in pigs thereby improving
absorptive surface area (Mosenthin, 1999). There is also increasing evidence that
short-chained xylose-oligomers generated through feed enzyme activity may be a
specific substrate for certain useful fermentative bacteria (Apajalahti &
Bedford, 1998). In corn-soy diets the digestibility of starch and protein has
been shown to be highly variable, and an enzyme product (Avizyme 1500) has been
specifically developed for corn-soy diets as a result. Excessive drying or heat
processing of feeds damages the ileal digestibility of starch and protein, providing
more nutrients for hindgut bacterial proliferation. In the USA, Finnfeed's corn-soy
enzyme has been shown to improve ileal starch digestion by 13.5% and ME by 6%,
decreasing the amount of starch digested in the caecum by 5%, and improving ME
by nearly 1% (Coon et al. 1998).
Figure 1. Effect of feed enzyme on FCR
in four trials (relative to 100% FCR in control diets) in diets with and without
AGPs (Elwinger & Teglof, 1991; Hock et al, 1997; Moran & McGinnis, 1968;
Vranjes & Wenk, 1996)
Recent trials comparing broilers with and without microflora showed that negative
effects of poor diet digestibility are only evident when gut bacteria are present
(Schutte & Langhout, 1999; Smits & Annison, 1996), so increasing bacterial
populations through AGP-removal will reduce growth. In the absence of dietary
prophylactic AGPs reliable improvements in animal performance through supplementation
with proven enzymes will become more important. In four published trials, use
of enzyme alone led to an average 5.9% improvement in FCR while growth promoters
gave a 3.3% advantage (figure 1). The combination of the two gave the greatest
(7.9%) response, demonstrating that the mode of action of the two products is
quite different. As most producers in the EU have been using AGPs and enzymes
for many years, the loss of the 3% performance on AGP withdrawal will enhance
the economic significance of the 5.9% improvement by enzyme alone.
Betaine - its role in poultry diets
Betaine is used in animal feeds as a source of essential methyl groups for metabolic
reactions and as an osmoregulant. Its osmotic function is useful in maintaining
gut wall integrity, which has been observed as increased gut strength and reduced
dehydration of cells under stressful conditions. When cells dehydrate they cease
to function efficiently and become more susceptible to attack from pathogens.
This highlights the requirement for preserving the integrity and functioning of
the gut wall through increased cell hydration which can be achieved by feeding
betaine. In Europe, poultry production is under increasing threat from the disease
necrotic enteritis, caused by Clostridium perfringens. Challenging birds with
the coccidiosis pathogen E. maxima has been shown to cause the spontaneous development
of necrotic enteritis, as the gut wall damage by coccidiosis facilitates invasion
by clostridia (Waldenstedt et al, 1998). Removal of AGPs could lead to an increase
in necrotic enteritis due to reduced control of Clostridium perfringens, making
pathogenic invasion more likely, following even low levels of coccidiosis damage.
Figure 2 shows how betaine consistently improves the hydration and integrity of
the gut wall, manifested as reduced coccidiosis lesion scores and reduced water
loss (calculated as water retention = water intake-(urinary loss + evaporation)).
Figure 2. The effect of coccidiostat and
Betafin on water retention and gut wall damage in broilers challenged with coccidiosis
(ref. Finnfeeds Research Report no. B.CC.PC.92.1)
Water Retention
Poor protein digestion results in high caecal nitrogen levels which are currently
considered to encourage growth of Clostridium perfringens. Under normal gastric
conditions, nitrogen is well digested, little enters the caeca and necrotic enteritis
is uncommon. However, when viscous diets are fed or coccidiosis damage reduces
small intestinal absorptive function, less nitrogen is taken up by the animal,
and more enters the caeca resulting in a more frequent occurrence of necrotic
enteritis. The removal of AGPs from monogastric diets is anticipated to lead to
far greater incidence of necrotic enteritis (Broussard et al, 1986; Bywater, 1998;
Elwinger et al, 1998). By reducing the impact of coccidiosis infection on gut
cells by assisting in cell hydration and function this threat can be lessened.
Overall Conclusions
The ban on AGPs in Europe will cause difficulties for commercial pig and poultry
producers through poorer growing efficiency and increased stress and disease levels
in their animals. While feed enzymes and betaine cannot replace AGPs, they can
promote optimum digestion conditions in the intestine. This creates an environment
where nutrients are taken up and used by the host animal, rather than by the resident
bacteria. Removal of dietary AGPs are likely to increase variability in broiler
performance. Animals fed poorer quality diets are at risk of developing larger
intestinal microbial populations particularly in stressful environments. Increased
bacterial numbers will then compete for nutrients and could proliferate to pathogenic
levels. Finnfeeds enzymes improve diet digestibility, limiting proliferation of
hind gut bacteria by restricting the nutrients available to them, while betaine
helps to maintain intestinal cell function by osmoprotection, particularly in
the presence of a coccidiostat or under heat stress conditions.
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Author: Drs. Lucy Tucker, Craig Wyatt and Michael Bedford, Finnfeeds, Marlborough, Wiltshire, UK
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| 02/13/2005 |
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This is an area of interest. Such work is beneficial to the third world's countries. | Answer Checked by Engormix.com  |
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