SEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-060 Oct. 1982
Project Summary
Evaluation of Waste Citrus
Activated Sludge in
Poultry Feeds
Bobby L. Damron, Douglas M. Janky, Robert H. Harms, and
Mark F. Hall
Experiments were conducted on
chick broilers and hens to determine
the metabolizable energy of citrus
sludge. A determination of metaboliz-
able energy values showed that the
values decreased as the level of citrus
sludge in the diet increased. A series of
protein levels were fed to day-old
chicks for a three-week period in an
attempt to assay the protein quality of
citrus sludge. As the level of sludge in the
diet increased, its utilization decreased,
with an almost toxic effect being
observed at higher concentrations.
Vitamin Da and sludge were fed to
day-old chicks to determine if the
minerals contained in the sludge could
be causing the destruction of Vitamin
D3 in the feed. Results revealed that
the addition of Vitamin D3 did not
offset the depressing effect of sludge
feeding upon body weights. The
conclusion reached was that citrus
sludge was not related to Vitamin D3
destruction.
Experiments were conducted on
day-old chicks to evaluate the biological
availability of the phosphorus contained
in citrus sludge. All sludge treatments
produced body weights significantly
below those of a modified corn-soy
basal diet containing monosodium
phosphate.
Citrus sludge was also examined as
a source of pigmentation in egg yolks.
Hens were fed a white corn basal,
xanthophyll-free diet to deplete egg
yolk pigmentation. It was observed
that citrus sludge produced eggs with
the same hue as yellow corn containing
comparable amounts of xanthophyll.
The xanthophylls of yellow corn
appeared to be more biologically
available than those in citrus sludge.
Broilers were used to determine the
effectiveness of citrus sludge as a
pigmenting agent. White corn diets
mixed with sludge were compared with
yellow corn diets. Feeding sludge
resulted in both the shanks and skin
imparting the same hue and darkness
as feeding yellow corn at equivalent
xanthophyll levels.
This Project Summary was de vel oped
by EPA's Industrial Environmental
Research Laboratory, Cincinnati, OH,
to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Waste citrus activated sludge is the
product resulting from the treatment of
citrus processing plant wash water in a
facility similar to a municipal treatment
plant. One of the major problems
associated with this process is the
production of excess activated sludge.
The handling and disposal of sludge
amounts to one of the larger operating
costs of the system. A typical analysis of
the sludge is presented in Tables 1 and
2.
From previous studies with chicks
(broilers) and hens (Jones et al., 1975),
the recovery of activated sludge for the
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Table 1. Proximate Analysis of Citrus
Sludge
Nutrient
Moisture
Crude Protein
Fat
Fiber
Ash
NFE
Calcium
Phosphorus
Xanthophyll
Carotene
Percent
11.10
22.35
7.40
11.45
12.20
35.50
1.60
0.45
28. 60 mg/ kg
11.00mg/kg
Table 2. Trace Mineral Analysis of
Citrus Sludge
Element
Aluminum
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Selenium
Sodium
Zinc
Content
(ppm)*
2,500
1
100
3
260
4,600
120
2,100
51
0.5
120
7,300
<1
5,300
430
* Dry weight basis (ppm - mg/kg).
use of animal feed material was known
to be technically feasible and economi-
cally attractive. Experiments were de-
signed to further define this product as a
feed ingredient and to explore the cause
of depressed performance at higher
levels of supplementation.
Such experiments were designed to
evaluate the biological availability of
phosphorus, pigmenting value, and
protein quality of citrus sludge in poultry
feeds. The interaction between Vitamin
D3 and sludge was also examined as a
possible explanation for the depressed
performance seen at higher levels of
supplementation. It has been theorized
that the high mineral content in sludge
catalyzed the destruction of Vitamin D3.
These experiments were developed to
demonstrate the use of citrus sludge as
a feed ingredient to at least partially
offset both dewatering and disposal
costs. The addition of citrus sludge to
the diet of broilers did not affect the
palatability or texture of the meat. A
significant improvement in egg yolk
color was also observed when citrus
sludge was fed to hens. The flavors of
both the yolk and albumen were not
affected.
Highlights of Project
Findings
Metabolizable Energy of
Citrus Sludge
Day-old chicks were fed several diets
of citrus sludge substituted for an equal
amount of sucrose. During the third and
fourth week, representative samples of
excreta were collected for analysis.
Moisture (percent dry matter), gross
energy (expressed as Kcal/g), and
nitrogen and chromic oxide contents of
the various diets and excreta were
obtained to calculate the metabolizable
energy of citrus sludge.
The metabolizable energy of sludge
decreased numerically as the sludge
substitution level in the diet was
increased (Table 3). Excessive supple-
ments of sludge (16 percent and above)
were found to have a laxative effect on
the birds. This may account for some of
the decrease in utilization of sludge.
Citrus Sludge Protein Assay
A graded series of protein levels were
fed to day-old chicks for a three-week
period in an attempt to assay the protein
quality of citrus sludge. The negative
effect of sludge was reflected in its feed
intake efficiency. In the corn-soy diets,
as the protein level increased, feed
intake improved significantly. Conversely,
as the percentage of sludge was
increased, its utilization decreased or
became masked, and a depressing
effect occurred at the highest level of
supplementation (Table 4).
Citrus Sludge-Vitamin Da
Interaction
In two experiments, a graded series of
Vitamin Da and citrus sludge levels were
added to a corn-soy basal diet and fedto
day-old chicks for a three-week period.
Tibia ash, phosphorus, and calcium
values were obtained. There was no
significant difference between the
levels of sludge for values of calcium in
the first experiment, nor for phosphorus
or ash in both experiments. However,
there was an unexplainable increase in
calcium at the five percent sludge level
in the second experiment. As the level of
Vitamin Da was increased, ash values
increased numerically.
There was significant interaction
between sludge and Vitamin Da. As the
level of Vitamin D3 was increased, feed
Table3. Metabolizable Energy Per
Kilogram of Citrus Sludge
Dietary Sludge Metabolizable Energy
Level {percent) (Kcal/kg)
2
3
4
6
8
16
3.368
2.411
1.813
1,360
1,404
836
intake increased. Sludge had no impact
on feed intake. In summary, the depressing
effect that citrus sludge had on body
weight did not appear to improve with
the addition of Vitamin Da to the diet of
chicks. Therefore, the cause of the
depression of body weight by citrus
sludge was probably not due to the
destruction of Vitamin Da by the level of
iron in the sludge, as has been previously
suspected. This lack of interaction was
also expressed in ash values
Phosphorus Assay of Citrus
Sludge
Duplicate experiments were conducted
to evaluate the biological availability of
phosphorus contained in citrus sludge.
A modified corn-soy basal diet was
employed with variable amounts of
citrus sludge in which monosodium
phosphate, calcium carbonate, sucrose,
and filler were added. Day-old chicks
received each dietary treatment for a 3-
week period. The addition of supple-
mental phosphorus had no significant
influence in terms of body weight.
However, increasing calcium levels
supported some numerical improve-
ments in body weights. All sludge
treatments had weights significantly
less than the modified corn-soy diet
which had been supplemented with
phosphorus (from monosodium phos-
phate). Calcium levels did not affect tibia
ash values from sludge treatments. The
failure of sludge treatment to produce
better results may have been due to the
reduced feed intake associated with
those treatments. This reduction was
felt to be due to the large amounts of
sludge required to add phosphorus to
the test.
Evaluation of Citrus Sludge
as an Effective Egg Yolk
Pigmenting Ingredient
The purpose of this experiment was to
evaluate the egg yolk pigmenting
efficiency of waste citrus activated
sludge. Commercial hens were fed a
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Table 4. Protein Assay Chick Performance* (3 Weeks)
% Crude Protein
Body Weight (g)
Corn-Soy
16
18
20
22
16
16
16
Sludge
0
0
0
0
2
4
6
Exp. 1
364e
508b
549*
538*
479C
41 C?
302'
Exp. 2
404"
485*
536a
545a
45Sbc
430ca
289e
Feed Intake]
to)
33.6°
36.4ab
36. 8*"
35.2tic
37.3ab
38. 1a
30.5"
Feed Efficiency f
(g feed/g body wt)
1.80C
1.53s
1.421
1.361
1.70"
1.91h
2.24a
* Means without common letters are significantly different according to Duncan's mufti
pie range test (<0.05).
t Values are a combination of two experiments.
white corn, basal, xanthophyll-free diet
for 15 days to deplete the yolk of all
pigment. The yellow corn diets were
formulated to contain the same amount
of xanthophyll as each of the citrus
sludge diets. After 21 days on the
experimental diet, the eggs were
collected for analysis.
The data indicated that egg yolks
produced by hens fed citrus sludge were
the same color as those produced by
hens fed yellow corn at equivalent
xanthophyll levels. However, the egg
yolks produced by hens fed citrus sludge
did not have as much pigment as those
produced by hens fed yellow corn. This
was probably a result of xanthophylls in
yellow corn being more biologically
available. Citrus sludge would be a
suitable pigmenting agent for eggs
produced for home consumption. It
would not be as suitable as yellow corn
in eggs produced for commercial
processes (e.g., mayonnaise, noodles),
since there is less pigment in the yolks;
this pigment would be diluted, resulting
in processed egg products with less
than the desirable color.
Evaluation of Citrus Sludge
as an Effective Broiler Skin
Pigmenting Ingredient
This experiment was designed to
examine the influence of citrus sludge
on broiler pigmentation. Day-old chicks
were fed a white corn, xanthophyll-free
diet for a period of four weeks. Beginning
the fifth week, they were fed one of nine
experimental diets for three weeks.
Pigmentation values of both shank
and skin samples from broilers fed
yellow corn were significantly higher
than those fed the corresponding citrus
sludge diet. The feeding of citrus sludge
resulted in the same hue and darkness
of both the shank and skin samples as
did the feeding of yellow corn at
comparable xanthophyll levels. Pig-
mentation values indicated that the
xanthophyll in yellow corn was slightly
more available than that in citrus
sludge.
Conclusions and
Recommendations
Satisfactory conclusions could not be
reached. The chemical and physical
nature of waste citrus activated sludge
made it a very difficult product to
evaluate in the feeding trials. Several
experiments did show that: high mineral
content in citrus sludge was not an
inhibitor of Vitamin D3 efficiency, and
citrus sludge possessed pigmentation
values approximately equal to yellow
corn in broiler skin and shanks and egg
yolks.
It is doubtful that a citrus sludge
similar to the one employed in these
experiments would be feasible in the
commercial poultry industry because of
poor nutrient content and as-yet-
unidentified depressive agents. The
identification of the agents that are
reducing bird performance is necessary.
Further work is also needed to improve
the methods of concentrating, drying,
and handling the product to improve its
nutrient content.
U 8 GOVERNMENT PRINTING OFFICE- 1M2 - 559 -017 /084Z
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Bobby L Damron. Douglas M. Janky, Robert H. Harms, andMarkF. Hall are with
the University of Florida, Gainesville, FL 32611.
Kenneth A. Dostal and Harold W. Thompson are the EPA Project Officers
(see below).
The complete report, entitled "Evaluation of Waste Citrus Activated Sludge in
Poultry Feeds," (Order No. PB 82-259 904; Cost: $7.50, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officers can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
Environmental
Protection
Agency
EPA 335
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Penalty for Private Use $300
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