Asurge of interest in antibiotic-free broiler production throughout Canada’s poultry industry, coupled with the eventual availability of an effective vaccine to prevent necrotic enteritis, could become an important catalyst for change in the world poultry industry.

This trend is clearly evident in Canada, where producers see commercial potential for antibiotic-free (ABF) production but need a way to thwart losses from necrotic enteritis (NE) that stymied ABF production in the past, reported Dr. Linnea Newman, a consulting veterinarian with Intervet/Schering Plough Animal Health.

Newman described the results of two, on-farm trials with Netvax, a novel Clostridium perfringens type A toxoid vaccine for NE that is conditionally licensed in the US and under restricted licensing in Canada while awaiting full approval. The vaccine is administered to hens, which pass on immunity against NE to broiler progeny. The trials were conducted in two separate regions of Canada, each with conditions associated with NE.

The Ontario trial was conducted in a region with high pH soils and a history of NE outbreaks even on farms using in-feed anticoccidials with full-level antibiotic growth promoters. High pH soil appears to be a major risk factor for NE, she said.

Seventeen flocks from hens vaccinated with Netvax were fed ionophores without antibiotic growth promoters (AGPs). Performance was compared to flocks using traditional in-feed medication, including AGPs placed at the same time and processed at the same age.

Mortality followed normal patterns, and the average daily gains for the Netvax progeny grown without AGPs actually exceeded those of the flocks using a full in-feed medication program.

‘COMPELLING’ OUTCOME

Because the trial was small, the results could be interpreted only as trends and were not statistically significant, but the outcome was compelling, nonetheless, she said.

A separate trial in western Canada was carried out on a farm that had previously tried to introduce a coccidiosis-control program using Coccivac-B live vaccine. Despite the use of in-feed, growth-promoting antibiotics, the farm experienced heavy losses due to NE in six successive flocks.

NE is a major challenge for producers in this region, Newman noted, largely because of wheat-based diets. However, after wheat was removed, NE breaks still occurred and hit each flock twice. “It was almost as though nothing we did on this farm could prevent NE,” she added.

The trial used imported progeny of birds vaccinated with the C. perfringens type A toxoid, but this time, the birds were vaccinated with the live coccidiosis vaccine Coccivac-B. Initially, in-feed antibiotics were also used, resulting in two flocks that were successfully raised without NE. The producers then took it a step further and removed the in-feed antibiotic. The result: Two more flocks were raised on a full ABF program with no NE breaks.

Newman said the producer has now introduced a small, ongoing ABF program, using progeny from local breeders vaccinated with Netvax and feeding them an all-vegetable ration.

In an interview with Intestinal Health, Newman said that several Canadian producers tried to introduce ABF programs 5 to 10 years ago but had disastrous results due to NE. Now, interest in ABF production has renewed, judging in part by requests that Newman has received to speak in Canada on the topic.

The keen interest in ABF production is being driven by intense competition in the Canadian poultry industry, she said.

VACCINATION JUST ONE TOOL

Newman cautioned that although Netvax represents an important tool for controlling NE, it’s not the only one that producers will need.

“Growers must have all the other good management factors lined up,” she said. “Birds must get onto their feed straight away. That means good access, good lighting, good temperature control and supplemental feed.

“If they’re using an all-vegetable ration,” she continued, “this must be done right if they are to avoid too much wet litter — which only encourages C. perfringens and NE. Getting it right can mean some difficult juggling with ingredients and cost. Too much soy and you start getting too much indigestible feed. Use more synthetic amino acids, and you start getting cost issues.”

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