Synchronized coccidiosis control, management yield better broiler results
"Synchronized coccidiosis control, management yield better broiler results"
Newman
Performance in broiler flocks can be
improved by coordinating the coccidiosiscontrol
program with management
practices, Dr. Linnea Newman said.
Broilers perform better if they develop
immunity against coccidiosis early rather
than late into the production cycle.
However, exactly when immunity develops
varies with different anticoccidial
programs and management practices,
she said.
“For instance, flocks that are on reused
litter in houses with higher bird density
develop immunity earlier than flocks
started on clean litter in a full house,” said
Newman, of Intervet/Schering-Plough
Animal Health technical services.
“Coccidiosis control in broilers depends
upon immunity — regardless of whether
in-feed medication or vaccination is used,”
she said.
Early immunity against coccidiosis is
preferable because the adverse effects of
subclinical coccidiosis on performance
worsen with age, she said.
Newman cited work at Oklahoma State
University (see article, page 39), which
demonstrated that the later in life broilers
develop immunity to coccidiosis, the
greater the negative impact on performance
and the greater the cost.
This work is important, she explained,
because “many coccidiosis-control programs,
especially ionophores, shift the
immunity-building process to the last 2
weeks of a broiler’s life — when the most
significant weight is to be gained, the
greatest amount of feed will be consumed
and there is the greatest potential for a
loss in performance.”
Oocyst counting and weight analysis on
commercial broiler farms further confirm
the link between late development of
immunity and worsening performance —
as well as the role of the anticoccidial
and management programs used,
Newman said.
Clean litter can delay immunity
“Surprisingly, cleaning out houses works
against the immunity-building process,
especially with in-feed anticoccidial programs, causing an even greater impact
late in the life of a broiler,” Newman said.
On anticoccidial programs, coccidial
populations may explode after 28 days,
with higher peaks and a greater potential
for an adverse impact on broiler weight
gain. In contrast, used litter exposes birds
early in life to coccidia, which initiate the
gradual development of immunity.
Actual oocyst counts from clean litter
obtained in British Columbia and Ontario
demonstrate the pattern of Eimeria spp.-
oocyst shedding in full-house brooders
where birds receiving various in-feed
anticoccidials were started on clean litter
with a mandatory 2-week (or greater)
down time.
When the farm in Ontario collected
oocysts and determined daily weight
for one of its broiler flocks, the impact
of a late subclinical coccidial challenge
was evident, with weight diverging from
the Ross 308 published breed standard
(see Figure 1). “This is a real-world
example of the model developed by the
Oklahoma State University researchers,”
Newman added.
Figure 1.
Oocyst counts from clean litter versus the
actual growth curve show divergence from
the Ross 308 male 2007 breed standard.
These birds received narasin.
Half-house brooding on reused litter
produced different patterns. Higher bird
density (<0.80 ft2/bird) and heavily reused
litter from a farm located in the Delmarva
Peninsula of the US produced an early
oocyst peak at 19 days, regardless of
whether the program was Nicarb-narasin
or salinomycin, she said.
In contrast, birds that received salinomycin
and were in houses with low bird
density (1.0 ft2/bird), half-house brooding
and reused litter produced a later pattern
after two flocks; the pattern was similar
to that found in clean houses.
Birds that are vaccinated against coccidiosis
demonstrate some variability in the
development of immunity, but the pattern
is usually earlier than natural immunity
programs utilizing anticoccidials,
Newman said.
Vaccinated flocks started with half-house
brooding on reused litter peaked at 19
days (see Figure 2). In contrast, vaccinated
birds started in a full house on clean litter
had a delayed peak at 25 days.
Figure 2.
The oocyst peak in flocks vaccinated against
coccidiosis with Coccivac-B and started in
half-house brooding on reused litter was an
early 19 days. Density was 0.80 ft
2/bird.
Coccidiosis control with in-feed anticoccidials,
Newman said, no longer provides
complete “control” as it did 25 years
ago when many of the products were
introduced. “Most coccidiosis control in
broilers today depends on immunity —
either natural immunity moderated by
anticoccidial drugs, or immunity developed
through vaccination,” she added.
The successful development of immunity
is moderated by management style: clean
vs. reused litter, stocking density and
house management, which all impact
when and how immunity develops, she
continued.
The development of immunity to
coccidiosis requires exposure to multiple
life cycles of Eimeria spp. This necessary
exposure has an adverse impact on weight
gain and feed conversion, but the impact
will be a different magnitude depending
upon where it occurs on the growth curve,
Newman explained.
“If you want to maximize the geneticperformance
potential of your broilers,”
she said, “analyze your coccidiosis-control
program to determine when immunity is
completed on the growth curve and the
consistency of that timing over the full
production year.
“Coordinate your broiler-house
management and coccidiosis-control
programs to induce earlier immunity,”
Newman concluded.
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