Nutritionist: Aim for lowest coccidiosis-lesion score
“Some producers would view a lesion
score of 2 as being nominal, but in our
studies, we saw the average daily gain in
birds with this lesion score drop to zero,”
Teeter said. “Growers really need to pay
attention to their coccidiosis program and
get it as close to lesion-free as possible,”
he said in an interview after his
presentation.
Teeter and colleagues evaluated the
metabolic impact of coccidiosis at
different points on the broiler growth
curve. Teeter has presented results from
the studies before, but since then he has
more closely examined the data and
influence of coccidiosis on the energy
costs in broilers.
Further analysis confirms that low-level
coccidiosis produces a measurable cost
at any age, but the cost is much less if it
occurs early in the bird’s life, when there
is less overall impact on energy utilization,
he said.
In his presentation, Teeter explained how
he and his colleagues used metabolic
chambers in studies designed to mimic
coccidiosis challenge in a commercial
production environment. Over 1,000
Cobb X Cobb broilers were evaluated five
times over a 48-day period.
Teeter’s team challenged birds with an
orally administered mixture of E. maxima,
E. acervulina and E. tenella — three
common pathogenic species of the
protozoan parasite that causes coccidiosis
— at days 14, 21, 28, 35 and 42. Control
birds received only a sterile saline solution.
After each challenge, investigators placed
birds in metabolic chambers, where they
were evaluated for a variety of parameters
such as live weight, body composition,
heat production, retained energy and
excretion. After 6 days in the chamber,
they necropsied the birds and scored the
coccidial lesions.
Lesions, poor performance
correlated
As expected, control birds had no
coccidial lesions, but the challenged birds
did. Compared to controls, birds with
lesions had lower live weight and weight
gain, and poorer feed efficiency. They also
had less energy consumption, and their
ability to retain energy worsened with
age (see Table 1), Teeter said.
Table 1. Coccidiosis-mediated gross-lesion-score effects on production and energetic criteria at
standardized weights.
1
1 Values created using predictive models (R2>.95) and standardized initial weights.
2Mixed lesion scores were utilized for all variables except gain/feed, where homogenous arrays of 0, 1, 2, 3 and
4 were applied.
The metabolic chambers, Teeter noted in
the interview, are “very conservative and
the costs determined in this study would
be less than in the field.”
For instance, at 20 days of age, energy
retained by birds with a gross-lesion score
of 2 was 100 Kcal/day, at a time when
they were eating 300 Kcal/day. By 48
days, energy retained daily by the same
birds fell to 0 Kcal, even though the birds
were consuming 482 Kcal/day, he said.
Even in birds with a gross lesion score of
only 0.5, the results demonstrated the
impact of a coccidiosis challenge. At 20
days of age, retained energy was 170 Kcal, compared to 188 for controls. By 40 days
of age, it was 191 Kcal, compared to 305
for controls.
Higher maintenance energy cost
Lesions in challenged birds correlated
with maintenance energy cost. In other
words, the cost for birds challenged
with Eimeria increased with the lesion
score and became higher later into the
broiler-growth curve, he said.
Lesion scores were also positively
correlated with excreta energy loss, Teeter
said. “With a coccidiosis challenge, you
can see an additional 75 to 125 Kcals of
energy lost in excreta. Now that’s a pretty
big proportion of the bird’s daily appetite,”
he observed. “In addition, we saw the
maintenance requirements go up and an
additional number of K-calories lost as
heat and carbon dioxide, which goes into
the atmosphere.”
He pointed out that the consequences of
coccidiosis challenge were directionally
similar for birds with low and high lesion
scores. Feed-efficiency responses paralleled
energy responses, with the consequences
of coccidiosis challenge becoming more
profound late in the growth curve.
"Some producers would view
a lesion score of 2 as being
nominal, but in our studies...
average daily gain in birds
with this lesion score
[dropped] to zero."
“The consequence of coccidiosis challenge
is much more severe when you get up in
the second half of the growth curve, when
the bird is consuming most of the feed
it will eat during its lifetime,” and at a
time when feed costs are soaring, Teeter
said. “You absolutely don’t want that
bird developing immunity during that
time period, because it will be extremely
costly and result in a tremendous loss
for producers.”
It’s true that birds can bounce back and
make up the performance loss that occurs
after a coccidiosis challenge. But when
that challenge occurs in the second half of
the growth curve, there’s not enough time
to close the gap. “Once a calorie is lost in
excreta, it’s gone. Those calories would
just be a direct write-off to the bottom
line in terms of profitability,” he said.
The same findings probably apply to
any kind of immunity, not just immunity
against coccidiosis, Teeter supposes. “A
bird that has developed immunity early
appears to handle energy more efficiently
later on,” he added.
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