Antibiotic
growth promoters (AGPs) have routinely been used in intensive poultry
production for improving birds’ performance. However, in recent years, reducing
the use of antibiotics in animal production has become a top priority, due
to concerns about the development of antibiotic-resistant bacteria and mounting
consumer pressure. Multiple countries have introduced bans or severe
restrictions on the non-therapeutic use of antibiotics, including in the US,
where the Food and Drug Administration has implemented measures to curb the use
of antibiotics since 2017.
However, the
removal of AGPs poses challenges for poultry performance, including reduced
feed efficiency, decreased daily weight gain, as well as higher mortality.
Moreover, the withdrawal of AGPs in feed is widely recognized as one of the
predisposing factors for necrotic enteritis (NE). NE is one of the most common
and economically important poultry diseases, with an estimated global impact of
US$ 5 to 6 billion per year. As a result of withdrawing AGPs, the usage of
therapeutic antibiotics to treat NE has increased. To break out of this vicious
cycle and to secure the efficiency of poultry production, alternatives are
needed that combat NE where it starts: in the gut.
Necrotic enteritis: a complex disease
NE is caused by
pathogenic strains of Clostridium
perfringens (CP): ubiquitous, gram-positive, spore-forming anaerobic
bacteria. The spores of CP can be found in poultry litter, feces, soil, dust,
and contaminated feed. Low levels of different CP strains are naturally present
in the intestines of healthy birds, kept in check by a balanced microbiome.
However, when gut health is compromised, pathogenic strains can proliferate at the expense of unproblematic
strains, resulting in clinical or sub-clinical NE.
Animals
suffering from the clinical form show symptoms such as general depression,
reluctance to move, and diarrhea, with mortality rates of up to 50%. Infected
birds suffer from degenerated mucosa lesions in the small intestines. Even in
its “mild”, subclinical form, which often goes unnoticed, the damage to the
animals’ intestinal mucosa can result in permanently reduced performance and
consequent economic losses for the producer.
Certain
predisposing factors have been found to enable the proliferation of
pathogenic strains in the gastrointestinal tract. Diet is a key example: the
composition of the gut flora is directly linked to feed composition. High
inclusion rates of cereals (barley, rye, oats, and wheat) that contain high
levels of non-starch polysaccharides (NSPs), high levels of indigestible
protein, and inclusion of proteins of animal origin (e.g. fishmeal) have been
shown to predispose birds to NE.
A range of
diseases (e.g. chicken infectious anemia, Gumboro, and Marek’s disease), but
also other factors that have immunosuppressive effects, such as heat or cold
stress, mycotoxins, feed changes, or high stocking density, render birds more
susceptible to intestinal infections. The single most prominent predisposing
factor for the occurrence of NE is the mucosal damage caused by coccidiosis.
Gut health is key to combating necrotic enteritis
To control NE, a
holistic approach to optimizing the intestinal health of poultry is needed. It should
take into account not only parameters such as diet, hygiene, and stress, but
should also make use of innovative tools.
Phytomolecules,
also known as secondary plant compounds, are essentially plants’ defense
mechanisms against pathogens such as moulds, yeasts, and bacteria. Studies have
demonstrated the antimicrobial effects of certain phytomolecules,
including against antibiotic-resistant pathogens. Phytomolecules have also been
found to boost the production of digestive enzymes, to suppress pro-inflammatory
prostaglandins and have antioxidant properties. These features make them a
potent tool for optimizing gut health, potentially to the point of replacing
AGPs.
Can phytomolecules mitigate the impact of necrotic
enteritis?
To study the
impact of phytomolecules on the performance of broilers challenged with a
NE-causing CP strain, a trial was conducted at a US-based research facility. In
this 42-day study, 1050 male day-old Cobb 500 broiler chicks were divided into
3 groups, with 7 replicates of 50 chicks each.
On the first
day, all animals were vaccinated against coccidiosis through a live oocyst
spray vaccination. The experimental diets met or exceeded the National Research
Council requirements, and were fed as crumbles/pellets. On days 19, 20, and 21,
all pens, except the negative control group, were challenged with a broth
culture of C. perfringens. A field isolate of CP known
to cause NE (originating from a commercial broiler operation) was utilized as
the challenge organism. On day 21, three birds from each pen were selected,
sacrificed, group weighed, and examined for the degree of present NE lesions.
The positive
control group received no supplements. The trial group received a synergistic
combination of two phytogenic products containing standardized amounts of
selected, microencapsulated phytomolecules: an in-feed phytogenic premix (Activo®, EW Nutrition GmbH) and a liquid complementary
feed supplied via the drinking water (Activo® Liquid, EW Nutrition GmbH). The
products were given at inclusion rates corresponding to the manufacturer’s
baseline antibiotic reduction program recommendations (Figure 1):
Figure 1: Trial design
The trial
results indicate that the addition of phytomolecules helps to mitigate the
impact of NE on broilers’ performance. The group receiving Activo® and Activo®
Liquid showed a better feed conversion (Figure 2) compared to the positive
control group (NE challenge, no supplement). Also, better lesion scores were
noted for animals receiving phytomolecules (0.7 and 1) than for the positive
control group (1.6).
The most
significant effect was observed concerning mortality: the group receiving
Activo® and Activo® Liquid showed a 50% lower mortality rate than the positive
control group (Figure 3). These results clearly indicate that phytomolecules
can play an important role in mitigating losses due to NE.
Figure
1: Adjusted FCR
Figure
2: Lesion scores and mortality
Tackling necrotic
enteritis in a sustainable way
In an age of
AGP-free poultry production, a concerted focus on fostering animals’ gut health
is key to achieving optimal performance. This study strongly demonstrates that,
thanks to their antimicrobial, digestive, anti-inflammatory and antioxidant
properties, phytomolecules effectively support birds’ intestinal health when
challenged with NE. The inclusion of Activo® and Activo® Liquid, two phytogenic
products designed to synergistically support birds during critical periods,
resulted in improved feed conversion, better lesion scores, and 50% lower
mortality.
In combination
with good dietary, hygiene, and management practices, phytomolecules are
therefore a potent tool for reducing the use of antibiotics: including Activo®
and Activo® Liquid in their animals’ diets allows poultry producers to reduce
the incidence of NE, to mitigate its economic impact in case of outbreaks, and
therefore to control NE in a sustainable way.
By A.
Bhoyar, T. van Gerwe and S. Regragui Mazili
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