Animal Science Floida Agricultural
Mimeograph Report No. AN67-7 JUL 6 197 Experiment Station
March, 1967 Gainesville, Florida
COMPARATIVE NUTRITIONAL VALUE OF PELLETED AND REGULAR DRIED1/
CITRUS PULP WHEN FED AT DIFFERENT LEVELS TO FINISHING STEERS-
C. B. Ammerman, F. C. Neal, A. Z. Palmer,
J. E. Moore and L. R. Arrington-
Dried citrus pulp has been shown to be a valuable feedstuff for
dairy (Keener, et al., 1957; and Becker and Arnold, 1951) and beef
cattle (Peacock and Kirk, 1959 and Ammerman et al., 1963). It is an
important by-product feedstuff, particularly in the southeastern states.
With the increased production of citrus fruit, the pulp is becoming
increasingly important in other areas of the United States and in
foreign markets as well. An economic limitation on the transportation
of pulp is its relative bulkiness. By pelleting, its density is in-
creased greatly and this could result in a substantial reduction in
cost of transportation and in cost of storage. In the present study,
the comparative feeding value of pelleted and regular dried citrus
pulp was determined when fed at different levels to finishing steers.
In addition the durability of the citrus pulp pellets was determined.
Forty Hereford yearling steers were used in this experiment. The
steers were ear tagged, vaccinated for blackleg and malignant edema
and implanted with two, 12 mg. pellets of diethylstilbesterol ten days
before experimental feeding was started. An examination of fecal samples
from several steers indicated that the animals were essentially free
of internal parasites. During the pre-trial period, Bermudagrass hay
was fed ad libitum and approximately three pounds of a ration containing
SThis study was supported in part by funds from the Florida Citrus
Processors Association in cooperation with the Florida Citrus Com-
mission. Acknowledgment is made to American Cyanamid Company,
Princeton, New Jersey, for supplying Aurofac-lO and to Dawes Labora-
tories, Inc., Chicago, Illinois, for supplying vitamins A and D.
Ammerman, Associate Animal Nutritionist; Neal, Associate Veterinarian;
Palmer, Meat Scientist; Moore and Arrington, Associate Animal Nutri-
tionists. The assistance of G. M. Means and Barbara King is acknow-
ledged. The authors are particularly grateful to Mr. Ted Shields,
Security Mills, Tampa, Florida, for pelleting the citrus pulp.
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40% ground snapped corn, 40% dried citrus pulp, 18% cottonseed meal, 1%
trace mineralized salt and 1% defluorinated phosphate were fed per steer
The steers averaged 734 pounds initially and were divided into
eight groups of five steers each on the basis of body weight. The groups
were randomly assigned to lots to receive the eight concentrates shown
in table I.
TABLE 1. COMPOSITION OF CONCENTRATE MIXTURES
% citrus pulp
Dried Citrus Pulp 2/
Corn Meal-Cob and Shuck-
Soybean Meal (50% protein)
Alfalfa Meal (17% protein)
Urea (262% protein equivalent)
Defluorinated Phosphate 3
Salt (trace mineralized)-
Vitamins A and D-
+ + + +
Four concentrate mixtures were
made with regular pulp and four with
' Mixture of 80% corn meal and 20% ground corn cobs and shucks.
- Smith-Douglass Company, Norfolk, Virginia.
- Carey Salt Company, Hutchinson, Kansas, listed minimum analysis in
percent: Fe, 0.27; Mn, 0.25; Cu, 0.033; Co, 0.01; Zn, 0.005; I,
0.007; and NaCI, 95.9.
- Initially, 0.1 pound of Aurofac-10 per 100 pounds or 10 mgs aureomycin
per pound of concentrate. At 21 days reduced to 3.5 mgs per pound
- 1000 I.U. vitamin A palmitate and 200 I.U. vitamin D2 added per
pound of concentrate.
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The dried citrus pulp was of good quality and the corn-cob shuck mixture
was made by blending 80% corn meal with 20% ground cobs and shucks.
Dried citrus pulp, either regular or pelleted, was substituted for the
corn-cob and shuck mixture in amounts which represented 0, 22, 44 and
66% of the total concentrate. All citrus pulp came from the same pro-
duction run and the pelleted pulp fed during the first 56 days of the
trial was ground through a three-eights inch screen in a hammer mill
and made into pellets three-eights inch in diameter. That fed during
the latter forty days of the trial was pelleted without grinding. The
relative durability of the pellets was tested with equipment designed
by Stroup (1962).
Initially the steers were fed three pounds of the concentrate
mixture per head daily and this amount was increased one pound per steer
daily until feed was refused. The concentrate was fed twice daily in
equal feedings and during the first two weeks, long Bermudagrass hay
was fed ad libitum. The hay was then reduced to approximately four
pounds per steer daily during the third week and at the end of three
weeks, the hay for all steers was reduced to two pounds per head daily
for the remainder of the 96-day feeding trial. No minerals were fed
except those mixed in the concentrate. The nutrient composition of
the concentrates is shown in table 2.
TABLE 2. NUTRIENT COMPOSITION AND DENSITY OF
CONCENTRATE MIXTURES AND CITRUS PULP-1
% citrus pulp Citrus
0 22 44 66 pulp
Protein 12.7 12.2 12.4 12.3 ----
Calcium 0.44 0.69 0.94 1.18 ----
Phosphorus 0.43 0.40 0.38 0.35 ---
Ca:P ratio 1.02 1.72 2.47 3.37 ----
Density, Ib./cu. ft.
Regular 31.8 28.5 24.6 21.9 13.02/
Pelleted ---- 36.6 41.8 46.0 41.6-
SAll composition values expressed in percent on a 90% dry matter
/ Pellets produced from ground citrus pulp averaged 44.1 and those
produced from unground citrus pulp averaged 39.0 pounds per cubic
Individual steer weights were taken on two successive days at the
beginning and end of the experiment and single weights were taken at
2-week intervals during the progress of the experiment. All weights
were taken at approximately 10:00 a.m. with the steers having had access
to feed and water. The final weights were shrunk three percent in cal-
culating total gains, average daily gains and dressing percent. At the
time of slaughter, the rumen of each steer was emptied and a visual
examination of the epithelial lining was made. Carcass grade and marbling
scores were determined by a federal beef grader and fat thickness over
the ribeye and the ribeye area were measured at the 12th rib.
Calcium was determined by atomic absorption spectrophotometry
(Perkin-Elmer, 1964) and phosphorus and protein determinations for the
feed samples were made according to the methods of A.O.A.C. (1965).
The data were analyzed statistically by analysis of variance as described
by Snedecor (1956).
Results and Discussion
The two control lots of steers receiving no citrus pulp gained an
average of 2.52 and 3.17 pounds per steer daily, respectively, and the
difference in gain was significant (P<0.01). The animals in the lot
gaining 2.52 pounds per steer daily included one wild steer which gained
only 1.60 pounds per day and which may have influenced the performance
of all steers in that lot. The performance of the steers in the other
lot which gained an average of 3.17 pounds per steer daily was considered
more representative of that expected from this ration.
When the gains for the steers receiving the regular or pelleted
citrus pulp were combined, those steers fed 22, 44, or 66% pulp gained
3.08, 2.90, and 2.82 pounds per head daily, respectively. When the gains
for steers receiving the three levels of pulp were averaged, those steers
fed regular pulp gained 2.89 and those fed pelleted pulp gained 2.98
pounds per day. Steers fed 66% regular pulp gained 2.61 pounds per day
and those fed 66% pelleted pulp gained 3.04 pounds per day. This
suggested difference in gain may have been accounted for in part by a
difference in feed intake. As shown in table 3, steers fed 66% regular
pulp consumed an average of 22.13 and those fed 66% pelleted pulp, 22.80
pounds of concentrate per steer daily during the entire 96-day feeding
period. While this represented approximately 0.7 pound more feed per
steer daily for those fed pelleted pulp for the entire period, the
difference in intake became greater as the trial progressed. During the
last fourteen days, the steers fed pelleted pulp consumed 1.9 pounds
more concentrate per animal daily than did those fed regular pulp. The
difference in feed consumption may have been due in part to the difference
in ration density. The concentrate containing 66% pelleted pulp had a
density over twice that of the concentrate containing 66% regular pulp
(46.0 vs 21.9 lb. per cu. ft., table 2).
TABLE 3. EFFECT OF PELLETING CITRUS PULP AND CONCENTRATE COMPOSITION ON
AVERAGE WEIGHT GAIN, FEED CONSUMPTION AND FEED REQUIRED
PER POUND OF GAIN OF FINISHING STEERS
Total period. 96 days
Initial weight, lb.
Final weight, lb.-
Total gain, lb.
Daily gain, lb.
Daily feed consumption, lb.
Feed/cwt. gain, lb.
% citrus pulp
0 22 44 66
742 728 733 732
1046 1022 1005 1024
304 294 272 292
3.17 3.06 2.83 3.04
SFull weight off experiment shrunk 3 percent.
/ This lot contained.one wild steer which gained only 1.60 pounds per day and which may have influenced performance
of all steers in the lot.
3/s, 2 pounds of hay fed per steer daily.
- After 21 days, 2 pounds of hay fed per steer daily.
Carcass Characteristics Carcass characteristics were not significantly
different according to experimental treatment and are summarized in
table 4. The overall dressing percent was 58.8 and the average carcass
grade according to treatment varied from high good to low choice. The
average degree of marbling of the lean ranged from "small minus" to
"small plus" for the different dietary treatments. The estimated percent
yield of the carcass averaged 50.2 for all treatments and the amount
of fat over the ribeye and the estimated kidney knob did not vary signif-
icantly with treatment.
The results obtained in this study may be compared with those re-
ported by Peacock and Kirk (1959) and Ammerman et al. (1963). Data
obtained by Peacock and Kirk (1959) showed no significant differences
in daily gain, slaughter grade or dressing percent between steers in
drylot when fed a concentrate mixture containing either 70% dried citrus
pulp or ground snapped corn adequately supplemented with protein and
other essential nutrients. When regular pulp was fed as 0, 22, 44,
and 66% of the concentrate for finishing steers, Ammerman et al. (1963)
reported average daily gains of 2.92, 2.98, 3.26 and 2.90, respectively.
Although not significantly different, the trend toward a lower rate of
gain with the highest level of pulp is similar to that observed in the
Ruminal epithelium Observations made on the ruminal epithelium are
shown in table 5. The color of the papillae varied from the usual
flesh color to dark gray with the darker colors occurring with the
ration higher in the corn-cob and shuck mixture. Fourteen of the
eighteen rumens examined from those steers consuming the two higher
levels of pulp showed slight to extensive coating of the rumen papillae
with a gummy, brown to black covering. On gross inspection, this coating,
or keratinization, appeared as a cap over the free extremity extending
over approximately one-fourth the length of the papillae. In two steers
fed the higher levels of pulp, either slight or severe clumping of the
papillae was evident. In this condition groups of papillae were bunched
together and appeared "clogged" with very fine feed particles. Both
of the above conditions have been described in detail by Nockels et al.
(1965) and by Jensen et al. (1954a, 1954b) and are generally referred
to as rumen parakeratosis. Ammerman et al. (1963) reported that ex-
tensive parakeratosis occurred in finishing steers when as much as 44
or 66% regular citrus pulp was fed in the concentrate mixture. In the
present study no difference between regular or pelleted citrus pulp in
causing parakeratosis was evident. Also, average daily gains, on an
individual animal basis, did not appear to be influenced by the degree
of rumen parakeratosis (table 5). Such an effect might have become
evident had the trial been extended beyond 96 days.
Citrus Pulp Pellet Durability Citrus pulp pellets must be durable if
pulp is to be handled satisfactorily in this form. The durability of
the pellets fed in this study is shown by the data presented in table 6.
TABLE 4. EFFECT OF PELLETING CITRUS PULP AND CONCENTRATE COMPOSITION
ON CARCASS CHARACTERISTICS OF FINISHING STEERS
Concentrate mixture, % citrus
Number of Steersi
Federal carcass grade-
Estimated % yield-
Chilled carcass wt., lb.
Fat over ribeye, in.
Est. % kidney knob
Ribeye area, sq. in.
- Based on full weight off experiment
shrunk 3 percent and the 48 hr.,
chilled carcass weight.
2/Based on conformation, finish and quality. Low, average and high good grades represented by 13, 14
and 15, respectively.
3/Small minus, average small and small plus degrees of marbling represented by 10, 11, and 12, respec-
-Estimated percent boneless, closely trimmed lean from round, rump, loin, rib and chuck.
- -- ----
- -- --
TABLE 5. AVERAGE DAILY GAINS AND RUMEN PAPILLAE CHARACTERISTICS OF INDIVIDUAL STEERS
Regular Citrus Pulp
Pelleted Citrus Pulp
% citrus pulp
Color Coating- Clumping-
Color Coating- Clumping-
light gray 0 0
brown 0 0
flesh 0 0
flesh 0 0
dark gray 0 0
- Refers to percent papillae
SRefers to papillae adhered
/ Some eroded areas.
showing some encrustation on their surface.
together in clumps.
_ __ __
- -- ---
TABLE 6. DURABILITY OF CITRUS PULP PELLETS
Fines from Fines after + tumbling,
1/ 2/ 3/
Treatment of Pulp bag, %- tumbling, 7. ____ /%
Ground, then pelleted 1.58 5.35 6.85
Unground, pelleted 6.48 7.05 13.07
Two, 50-pound bags of each type pellet screened over a one-quarter
inch mesh steel wire cloth.
/ Four, 500 gram samples of each type pellet, free of fines, were
tumbled for 10 minutes in a tumbler as described by Stroup (1962)
and then screened over a one-quarter inch mesh steel wire cloth.
/ Calculated total fines that would have occurred if initial samples,
with fines included, had been tumbled.
The citrus pulp which was ground prior to pelleting produced a more
durable pellet. When the pelleted pulp was screened directly from the
bags as received, only 1.58% of the pulp passed through a one-quarter
inch mesh wire screen when the pulp was ground before pelleting. A
similar value for pellets produced from unground pulp was 6.48%. Tumbling
the two types of pellets after initial screening resulted in 5.35%
fines from the pulp previously ground and 7.05% from the unground pulp.
A 96-day feeding trial was conducted with 40 steers to determine
the comparative value of pelleted and regular dried citrus pulp when
fed at different levels to finishing steers. Dried citrus pulp, either
pelleted or regular, was substituted for an 80% corn meal-20% cob and
shuck mixture in amounts which represented 0, 22, 44 and 66% of the
total concentrate to provide eight dietary treatments. Approximately
two pounds of long Bermudagrass hay were fed per steer daily during
the major portion of the feeding trial in addition to a full feed of
concentrates. Results of the experiment may be summarized as follows:
1. Average daily gain for all steers was 2.89 pounds. Steers
fed 66% regular pulp gained 2.61 pounds per day and those
fed 66% pelleted pulp gained 3.04 pounds. This suggested
difference in gain may have resulted from greater feed
consumption by the steers fed pelleted pulp.
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2. Average carcass grade, according to treatment, was high
good to low choice and carcass characteristics including
grade, dressing percent, degree of marbling and estimated
percent of yield were not significantly influenced by level
or form of citrus pulp.
3. Steers fed either 44 or 66% citrus pulp had rather extensive
rumen parakeratosis. This condition did not appear to
affect weight gains and was not influenced by form of pulp.
4. Citrus pulp pellets produced from ground pulp were more
durable than those produced from unground pulp.
1. Ammerman, C. B., P. A. van Walleghem, A. Z. Palmer, J. W. Carpenter,
J. F. Hentges and L. R. Arrington. 1963. Comparative feeding
value of dried citrus pulp and ground corn and cob meal for fat-
tening steers. Animal Science Mimeograph Report No. AN64-8..
2. A.O.A.C. 1960. Official Methods of Analysis. 9th Ed. Association
of Official Agricultural Chemists, Washington, D. C.
3. Becker, R. B. and P. T. Dix Arnold. 1951. Citrus pulp in dairy
rations. Fla. Agr. Exp. Sta. Cir. S-40.
4. Jensen, Rue, W. E. Connell and A. W. Deem.
its relation to rate of change of ration
of concentrate in the ration of cattle.
1954a. Rumenitis and
and the proportion
Am. J. Vet. Res. 15:425.
5. Jensen, Rue, H. M. Deane, L. J. Cooper, V. A. Miller and W. R. Graham.
1954b. The rumenitis-liver abecess complex in beef cattle, Am.
J. Vet. Res. 15:202.
6. Keener, H. A., N. F. Colovos and R. B. Eckberg.
value of dried citrus pulp for dairy cattle.
Exp. Sta. Bul. 438.
7. Nockels, C. F., L. D. Kintner and W. H. Pfander.
of ration on morphology, histology, and trace
sheep rumen papillae. J. Dairy Sci. 49:1068.
1957. The nutritive
New Hampshire Agr.
mineral content of
8. Peacock, F. M. and W. G. Kirk. 1959. Comparative feeding value of
citrus pulp, corn feed meal and ground snapped corn for fattening
steers in drylot. Fla. Agr. Exp. Sta. Bul. 616.
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1964. Analytical Methods of Atom Absorption Spectrc-
The Perkin-Elmer Corporation, Norwalk, Connecticut.
10. Snedecor, G. W. 1956. Statistical Methods. 5th Ed. The Iowa
State College Press, Ames, Iowa.
11. Stroup, R. L. 1962. Proposed standard method of testing pellet
quality. Proc. Feed Production School, Midwest Feed Manufacturing
Association. Kansas City, Missouri, p. 37.