Bioshuttle program helps control E. tenella outbreaks in pullets

Administration of an in-feed anticoccidial after coccidiosis
vaccination has helped alleviate outbreaks of Eimeria tenella in broiler breeder replacement stock, Erin Riley,
DVM, of Sanderson Farms, told Poultry
Health Today.

For years, Sanderson has vaccinated its broiler breeder
replacements against coccidiosis, which it “tempered” with 2 days of amprolium
treatment, Riley said. In the past 2 years, however, there have been sporadic
yet frequent breaks of E. tenella in
the replacement birds, which was affecting livability as well as uniformity.

Broiler breeders are the company’s most expensive birds, and
problems with uniformity can have a large economic impact, he noted.

Early coccidial
cycling

The reason for the outbreaks, which tended to occur in late
winter and early spring, wasn’t always obvious. Sometimes there was a glaring
management issue, but other times, it wasn’t possible to pinpoint the problem.
Studies, however, indicated high coccidial cycling from 10 to 14 days of age.
“And I personally believe it’s a little too much cycling on that young of a
bird,” Riley continued.

To try and remedy the problem, Sanderson decided to follow
vaccination with an anticoccidial — a so-called bioshuttle program — which it
has found useful in its broilers. For the pullets, it used the non-ionophore anticoccidial
zoalene.

“We start small before we go big,” Riley said, so the company
conducted paired house trials on two Mississippi farms to compare the vaccination/amprolium
program with the bioshuttle program. The results were “a bit better” with the
new program. Next, Sanderson tried the bioshuttle program in North Carolina, and
“we had good success.”

Timing is important

Timing is important, he said. The in-feed anticoccidial has
to be administered 4 to 5 days before clinical outbreaks of coccidiosis;
otherwise it’s too late. The outbreaks at Sanderson occurred at 12 days of age
— very early — so the zoalene program had to start at 8 or 9 days of age.

Although it is not an ionophore, Riley said, zoalene allows
some leakage [when used at the lower end of its approved dose range] and in
that way behaves similarly to an ionophore.

The goal is to make sure the bird gets the right amount of
exposure to the disease.

“So, if we were to shut down oocyst cycling, it would reduce
the bird’s exposure and very well would likely not allow the bird to get
adequate immunity,” Riley explained. 

“And when they go to the breeder house, they very well could
be exposed and succumb to E. tenella
or other Eimeria species if they’re
not adequately immunized.

“So, it’s a balancing act between getting enough oocysts
present for immunity but not over-exposure.”