9/23/2020: 

Robert Jan Molenaar DVM, published by Avined

For a number of years now, subclinical necrotic enteritis (SNE) has been found in layers. This intestinal disease results in production losses, due to poor digestion and reduced absorption of nutrients. The disease is not always easily identified in the field, as there are no clear symptoms. Many cases therefore probably go undiagnosed, making it difficult to gain insight into the actual damage caused. That is why Royal GD was commissioned by the poultry sector to examine the impact of this disease in layers.

Subclinical necrotic enteritis (SNE) is the clinically milder, but often economically more harmful version of classic necrotic enteritis (NE). Unlike SNE, NE is regularly found in broilers and turkeys. Both variants are caused by the Clostridium perfringens bacteria. In layers, SNE often presents itself in clearly defined grey to black necrotic foci at the proximal part of the duodenum. These may sometimes merge to colour part of the intestine dark grey.

Study of six layer farms diagnosed with SNE

For the study, the losses at six layer farms diagnosed with SNE were established. The study also examined the impact of SNE on production, and a further analysis was carried out on the Clostridium perfringens strains found. Below are the most notable research results:

• There were increased losses in most flocks during the period around the diagnosis, but on average, egg production and egg weight remained stable.
• The biggest (financial) impact of SNE at the six farms was the number of missed eggs as a result of the increase in mortality. Over a period of up to 70 weeks, this runs up to nine eggs per hen on average.
• The isolated Clostridium perfringens strains were able to produce toxins in all flocks, though the toxins were not the ones expected. The effect of these toxins in practice is unclear. However, the disease does seem to deviate from earlier studies.

Conclusion: complex with individual outbreaks and considerable damage

The study showed that there is a lot of variation between flocks in how the disease presents itself, which means that there may be individual outbreaks of SNE causing considerable damage. Looking exclusively at averages of all the flocks most likely results in a picture that is too optimistic. In short, SNE is a complex disease that requires regular pathological assessment of a flock of layers to be able to diagnose it at an early stage and intervene in time.

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