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However, they’re also likely to view research results with skepticism, because we all know that what appears to be a promising new finding often fails when tested in the field.

It is, therefore, gratifying for us to share in this issue an example of research that’s proving true in the real world. I’m talking about work conducted by Dr. Robert Teeter of Oklahoma State University. Teeter has spent vast amounts of time testing and studying the impact of coccidiosis on broilers and its economic impact; we’ve been reporting on his results all along.

He has found that when subclinical coccidiosis occurs late into the production cycle, broilers use more energy and need more feed. There is increased malabsorption, reduced effective caloric value and an elevated maintenance cost.

Subclinical coccidiosis late into the production cycle is seen when anticoccidials are the method of coccidiosis control; oocyst shedding, or leakage, occurs because coccidia have developed a reduction in sensitivity to anticoccidials.

Teeter has also found that birds near market age with even minor coccidial lesion scores, typical of subclinical coccidiosis, have an average daily gain of about zero. In short, a late coccidiosis challenge significantly hurts flock profitability.

In contrast, a coccidiosis challenge that occurs early in the production cycle has a minor negative effect, Teeter has found. An early challenge occurs when coccidiosis vaccination is administered at 1 day of age, enabling broilers to develop lifelong immunity against coccidiosis at a young age.

Now we are pleased to report on a field trial conducted at a broiler farm, which demonstrates that Teeter’s laborious laboratory research is on the mark.

The results of the trial, presented at a meeting by consultant veterinarian Linnea Newman, show that broilers on in-feed anticoccidials had extremely high coccidialoocyst counts during the later part of the production cycle — and their weight gain was zero. The producer switched to using the live-oocyst coccidiosis vaccine Coccivac-B for a few cycles, which seeded poultry houses with oocysts that are still highly sensitive to anticoccidials.

By the third cycle of vaccination, oocyst cycling was earlier, oocyst counts were lower and weight had improved 240 grams, compared to the first flock on anticoccidials.

When the producer returned to using anticoccidials — after the three cycles of coccidiosis vaccination — the results were amazing: Weight gain improved over 450 grams.

Rick Phillips, DVM
US Poultry Director
Intervet/Schering-Plough Animal Health
Email: [email protected]

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