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Threats to Avian Intestinal Integrity

28 November 2012

Bird health is a main concern for poultry producers across the globe. It does not matter how experienced a producer may be or where the farm is located in the world: bird health is always a big concern for a poultry producer, writes Nuria Martínez Herráez, editor of ThePoultrySite.

An outlook on broiler intestinal integrity was offered by Dr Luis Canseco, Poultry veterinary advisor for Elanco in the UK and Ireland, at the Poultry Meat Conference 2012, which was held in Warwickshire, UK, in September 2012.

Dr Luis Canseco

First, it is necessary to define what is intestinal integrity is.

According to Dr Canseco: "Intestinal integrity is the gut health of the broilers, which allows producers to reach the maximum performance with the minimum costs. The main threat to it is the combination of two of the most important broiler diseases affecting broiler production globally: coccidiosis and bacterial enteritis (also known as dysbacteriosis)."

Coccidiosis is 'a usually acute invasion and destruction of intestinal mucosa by protozoa. Infection is characterised by diarrhoea, fever, lack of appetite, weight loss, emaciation and, sometimes, death', according to the Merck Veterinary Manual.

The protozoa in question are parasites known as coccidia of the genus, Eimeria. Since they are parasites, they need a host in order to survive. When multiplying in the bird's intestine, the coccidia cause tissue damage resulting in poor nutrient absorption, which in turn results in reduced weight gain and reduced feed efficiency.

Coccidiosis' prevalence is worldwide, i.e, it will appear anywhere chickens are reared.

On the other hand, bacterial enteritis or dysbacteriosis is a disease caused by changes in the gut microflora which results in excessive intestinal mucus production and watery contents, which results in wet litter.

Excessive intestinal mucus production and watery contents

Why is Intestinal Integrity Important?

There is no doubt about the importance of preserving the intestinal integrity in commercial chickens. Coccidia are is present in every region of the globe as coccidial oocysts, is highly resistant in the environment and is easily transmitted among birds through oocyst ingestion from the litter.

Dr Canseco explained: "In the UK alone, it is estimated that coccidiosis and dysbacteriosis cost the poultry industry in excess of £90 million annually, this means 10p per bird (US$0.16)."

IN the UK, there are three coccidia affecting broilers: Eimeria acervulina, E.maxima and E.tenella.

Coccidiosis is species-specific, which means that the coccidia affecting chickens are different from the ones affecting other poultry species like turkeys or ducks.

Moreover, the damage to the intestine will vary, depending on the species infecting the birds. For example, E.acervulina affects the duodenum while E.maxima affects the jejunum and E.tenella - probably the best known among producers due to the blood presence in litters - affects the caeca.

But, is there any way for farmers to diagnose coccidiosis at farm level? E.acervulina and E.maxima are not visible in the birds unless lesion scoring is performed. Only E.tenella can produce blood contents in the droppings which are easily seen on the litter.

All of them can result in thinner or weaker chickens. However, these symptoms are not specific enough indicators to diagnose coccidiosis since these are the clinical signs for many poultry diseases.

In other words, once coccidiosis causes damage to the gut, it is too late to remedy the problem on the farm.

Coccidiosis Control

According to Dr Canseco, the best way to fight coccidiosis is by prevention and controlling the challenge.

He explained to the audience at the conference that disease control is accomplished by the combined use of all available tools in the poultry house: the environment, the immune system and anticoccidials. In fact, the three of them are necessary and, according to him, "if only one of them fails, it is likely that producers will face coccidiosis in their flocks."

So, how can poultry producers improve their use of the aforementioned tools and successfully face the challenge of improving intestinal integrity in their flocks?

Dr Canseco explained: "The best way to improve the intestinal integrity on a broiler farm is through continuous use of effective ionophore anticcocidials administered in the feed."

These anticoccidials are the way to maintain coccidiosis control within the poultry industry in Europe. The European Commission classifies them as zootechnical feed additives, among the different categories for veterinary products.

The ionophores form one class of anticoccidials that has remained effective in the control of coccidiosis after more than 40 years of continuous use by the broiler industry.

At the same time, the immune system and the management on the farm are the other two critical factors that need to be managed in order to maintain coccidiosis under control. For instance, these tools can be improved with good Infectious Bronchitis and Gumboro disease vaccination programmes (for improving the immune system), through good ventilation practices as well as good feeder and drinker management (for improving the environment on the farm).

Signs of E.maxima infection

Signs of E.acervulina infection

When Does Coccidiosis Affect Broilers?

Depending on the coccidia type, the peak challenge of coccidiosis takes place at different times in chickens' lives.

The peak challenge for E.acervulina generally occurs when the birds are 21 to 24 days old. For E.maxima and E.tenella, the peak is around 28 to 30 days.

Regarding dysbacteriosis, the data provided by Dr Canseco showed it is a challenge for birds from 28 days of age through to harvesting age for the processing plant.

This underlines how important it is to maximise gut health control during the final phase of production, which is a critical period of the production process. If the farmer were to remove the protection against coccidiosis in the last days of the production cycle, it could turn into a significant economic loss.

As he explained: "Nowadays, it is possible to protect the broilers up until the time of slaughter due to the use of anticoccidials with a zero withdrawal period approved by the regulatory authorities."

Finally, Dr Canseco explained that the incidence of coccidiosis is higher during summer months than during the winter. The opposite view on coccidiosis incidence is the one most popularly believed. However, the reason why this happens is still unknown.

"One of the theories," he explained, "could be that the rotation in the anticoccidial programme might change the dynamics in the coccidia population on the farm and provoke higher lesions."

This is based on Elanco's experience within the broiler industry in the United Kingdom but the science behind this is still being investigated.

"That's why stability in the anticoccidial programme is critical for a good control of coccidiosis," he added.

Dr Canseco concluded: "As long as birds are exposed to coccidial oocysts in the litter, there will be no eradication of coccidiosis."

ThePoultrySite would like to thank Dr Canseco for his help in the preparation of this article.

Further Reading

Find out more information on coccidiosis by clicking here.

November 2012

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