01999Applied Poultry %mc+ Inc
CHEMICAL
COMPOSITION,
DIGESTIBILITY,
AND METABOLIZABLE
ENERGY
CONTENT OF DIFFERENT
FAT
AND OILBY-PRODUCTS
MARIO E. ZUMBADO'
Centerf o r h i m a l Nutrition Research, School of Animal Science,
Universityof Costa Rica, San Josk, Costa Rica
Phone: (506)234-7220
F M : (506) 234-6I64
COR W. SCHEELE and CEES gWARERNAAK
Institute f o r h i m a l Science and Health, Resemh Branch Rundenveg 2, Postbus 65,
82OOAB Le@@ The Netherlands
Primary Audience: Nutritionists, Ingredient Buyers, Renderers, Oil
Processors
DESCRIPTION OF PROBLEM
In Costa R i a and other tropical countries
the industry that produces oil for human consumption is based on processing palm oil as
1
To whom correspondence should be addressed
the predominant local source of oil products,
d
y margarine, shortenin& a d o&j specifically for food frying (oleine). Imported soybeans are also processed to supply oil to the
market. During the process of oil extraction
264
and refining, several by-products and waste
products are obtained that can be further
processed for animal feeding purposes.
Other fat products in the local market also
require attention as potential ingredients.
There has not been sufficient study of tallow,
lard, and restaurant greases as potential feedstuffs, in contrast to the work of researchers in
other countries [l, 2, 31; swine and poultry
farmers already include those fats in the diets
without a clear knowledge of their real quality,
composition, and energy value.
The growing world poultry industry requires large amounts of fats as an energy
source in poultry diets to yield higher levels
of metabolizable energy mainly for broilers
at an economically justifiable price. Due to
dissimilarities in processes and descriptions,
by-productsobtained in different regions may
not be of the same chemical composition as
those reported in the literature. Thus the energy levels of the products for poultry available
in a given area may not be the same as those
reported by other researchers or included in
feed composition tables.
It is also important to consider that in
some parts of the world, including the U.S. and
the U.K.,feed fats are marketed with specific
names such as "hydrolyzed vegetable and
animal fat" or "white or yellow greases." Those
are the result of different combinations of
animal fats (tallow and lard), restaurant
greases, acidulated soapstocks, and other
residues of the oil refining industry. Some of
these products have specifications for feed
purposes as determined by their content of
moisture, impurities (insoluble residues), and
unsaponifiable matter (MIU), as well as free
fatty acids.
In many countries there is a need to know
more about the composition of those fat products that may be useful for the feed industry.
Such knowledge will allow a better understanding of how to produce blends with the
highest digestibility and metabolizable energy
levels. According to Renner and Hill [4] and
other published research data [5,6], the best
way to use some fats, especially more saturated
fats such as tallow and palm fats, is by blending
them with more unsaturated oils. Those researchers have usually found a synergism between fattyacids that improves the digestibility
of the fat and its metabolizable energy content,
particularly at high levels of dietary inclusion.
FAT BY-PRODUCTS
The present study sought first to describe
the different fat products available for animal
feedingin terms of their chemical composition
and to determine the digestibility and metabolizable content of those products and
blends. Through performing such analysis it
also sought to compare some of the results
obtained by two different laboratories using
the same products but with some differences
in procedures, equipment, and facilities.
MATERZALS
AND METHODS
Samples of different fat and oil products
from Costa Rica were collected and stabilized
with 200 ppm of the antioxidant ethoxyquin.
Half of each sample collected was shipped to
The Netherlands and the other half remained
in Costa Rica. Altogether nine different fat
products were used in the studies.
The products from the palm oil studied
were: crude palm oil (CPO), which is the main
product of that industry; palm free fatty acids
(PFFA) obtained after the distillation process
applied for the deodorization of CPO; and
full-fat palm kernel meal, a by-product with a
high oil content that has great potential as a
poultry feedstuff when its price is attractive for
feed manufacturing [q.Residual palm oil
(RPO) collected from oxidation lagoons,
which consists of a mixture of crude oil and
fatty acids, was also studied. This product is
usually drained of excess water at the collection point and dehydrated in a processing
plant to moisture content of less than 3%.
The RPO sample was obtained from a local
processor.
A fat product commercially labeled soybean free fatty acids (SBFFA) was also included in the study. SBFFA, a blend of three
by products: acidulated soapstock, gums, and
distilled free fatty acids, is obtained after
crude soybean oil is processed with hot water
and phosphoric acid [8].
'Ikro separate samples of yellow tallow
were includedin the study. These were directly
collected from two of the six rendering plants
in Costa Rica. International quality standards
and specifications are not usually used to
class@ this local tallow for feed purposes.
Almost 70% of it is used by the soap industry
and the rest for animal feeding.
The restaurant greases (RG) were collected from two different fast food restaurant
chains. For frying purposes these restaurants
Research Report
265
ZUMBADO et al.
was used to determine the digestibility and
apparent metabolizable energy (corrected to
nitrogen equilibrium) content of fat products
for broilers. One of the main modifications
was that excreta collection was performed at
25 days of age for 4 consecutive days (not
alternate days) and after a feed restriction
period of 6 hr.
Basal diets with no fat added were prepared and 10% of the different fat products,
either pure or in blends, were mixed with 90%
of the basal diet (Table 1).In the case of palm
kernel meal (47.1% fat), the ground product
was added at the rate of 21% in the experimental diet to reach about the same 10% added fat
as in the other diets. The composition of both
basal diets is shown in Table 2.
The procedures used at the University of
Costa Rica (UCR) and at the Institute for
Animal Science and Health (ID-DLO) in
The Netherlands were made as uniform as
possible, but the following differences existed.
At ID-DLO the birds were housed in climatecontrolled houses where temperature was
kept constant, and excreta was freeze-dried.
At UCR birds were housed in Petersime
batteries in conventional rooms and a forcedair oven was used to dry the excreta samples.
After thawing, the excreta samples were
homogenized and oven dried (UCR) or
freeze-dried (ID-DLO). The feed and excreta samples were ground to pass through a
%mesh sieve. Samples of ground materials
were allowed to come into equilibrium with
the air moisture, then stored in screw-top jars
while awaiting further analysis.
use oleine, a product of palm oil (RG1 and
RG2) or pure-refined soybean oil (RG3).
These RG were collected in plastic containers
and filtered through a 2-mm mesh screen to
eliminate food particles. This is the procedure
regularly used by restaurant grease processors
in Costa Rica.
A procedure to determine quality and
composition was established for the nine
experimental fat products within the study.
Levels of moisture, impurities, and unsaponifiable matter (MIU)were determined.
These are the main non-fat products that
will dilute the energy value of a fat [9]. Fat
content was determined [lo] for all fat products, although this is not an essential step when
assessing the quality of a fat product, because
fat content can be calculated as 100% minus
M U . Free fatty acid content [lo] was measured. This may indicate the degree of deterioration in quality of some fats due to hydrolysis
that could lead to oxidative rancidity. Fatty
acid composition of all fat samples was determined by gas chromatography [ll,121. This
is an important procedure, especially for fats
that are expected to present a variable composition due to their by-product nature. The fatty
acid profie of a fat indicates the ratio of unsaturated to saturated fatty acids, which is one
of the main factors affecting the metabolizable
energy content of a fat [3,4,5,6].
The last step in the evaluation of the fat
products was the determination of the metabolizable energy content for feed formulation.
The classical total excreta collection procedure [13], with some slight modifications,
FAT SOURCE
MOISIZTRE
I
FTA
MU
LIPIDS
%
PFFA
0.72
91.7
0.85
98.7
SBFFA
CPO
0.90
50.6
0.98
99.7
0.62
4.9
0.82
99.9
Tallow 1
1.08
7.9
1.29
97.8
Tallow 2
0.7
2.4
1.06
98.9
RG1
0.82
6.0
1.32
97.8
RG2
0.10
2.2
0.26
100.0
RG3
0.60
1.1
1.05
100.0
Palm kernel meal
8.00
-
-
47.1
JAPR
FAT BY-PRODUCTS
266
TABLE 2. ComDosition of the basal diets and the diet with full-fat Dalm kernel meal for AMEn determination
*Vitamin (UCR and ID-DLO) and mineral remixes (VCR) sovided r kg of diet: vitamin A, 11,OOO IU;
vitamin D3,2,200 IU; vitamin E, 15 I U vitamin 3 IU; thiamine, fmg; riboKvin, 45 mg;niacin, 30 m pantothenic
acid (Ca-antothenateklo mg; pyridoxine, 1 mg; d-biotin, 0.05 mg; folic acid, 050 m& vltamin Biz, O h mg; choline
chlonde &%, 400 m& n, 80 mg; Pe, 70 mg; Zn,80 m& Cu, 5 mg;I, 0.75 mg; and Se, 0.3 mg.
1&,
%inera1 remix ID-DLO xwided r
of diet: monocalcium phos hate, 267 g; CaCO3, 573 g; NaCI, 125 g;
CuS045&0,2 g; ZnS0.+7&0,3 g; &!3%.4H20,12
FeS0.+7H20,1%g; KI,50 mg; Se, 5 mg.
'Degussa AG, Feed Additives Division, Hanau, Germany.
Determination of crude fat in the fat
products, diets, and excreta was carried out
according to the Berntrop method (IS0 6492)
with a pre-extraction step (IS0 6498) [141.The
content of dried matter, nitrogen, and the heat
of combustion were analyzed according to the
AOAC [lo].
Tho methods were utilized to calculate
the AME, of the pure fats or fat blends. AME
values of the fat diets and the basal diet were
obtained by using the heat of combustion values of the diets and excreta. AME was also
calculated by using the digestibility coeffi-
I
cients multiplied by heat of combustion of the
fats. The digestibilitycoefficients of the added
fats in the diets were determined by comparing
fat digestibility values in fat or experimental
diets with fat digestibilityin the basal diet [14].
All calculations were determined on a dry
matter basis.
Weight gain, feed intake, and feed/gain
ratio of the broilers were determined for
the experimental period from 18 to 29 days
of age in the ID-DLO trial. A randomized
block design with three blocks of 18metabolic
cages was used. Within a block each diet was
Research Report
ZUMBADO et al.
267
randomly allocated to two cages. Results
achieved with the fat-containing diets were
analyzed with ANOVA (Genstat 5 or SAS)
[fi,161.
acids present in the final product are free; the
other half form triglycerides. Most of the other
fat products collected showed values below
10% FFA.
The fatty acid profiles of most of the fats
utilized in this experiment are summarized in
AND
Table 3. As expected, palm kernel fat is the
Table 1summarizesthe average composi- most saturated of the products analyzed.
PFFA contains an even higher amount of sattion of the different fat products studied and
urated fatty acids (SFA) than CPO. The preanalyzed at ID-DLOand UCR. Most of the
dominant fatty acids in these palm fats are
products showed a low moisture content,
palmitic and oleic acid; in the kernel fat the
which indicates that processing at the different
short-chain fatty acids lauric and myristic repplants is well controlled to avoid excess moisresent nearly 60% of the total fat content.
ture and further oxidation problems. The sum
Tallow
showed an SFA content similar to that
of moisture, impurities, and unsapodables in
of the oils from palm (around 50%), with steamost samples was close to 1%.Only tallow and
restaurant greases showed values above 1%, ric and palmitic as the main saturated fatty
acids.
but even these samples have MIU values
As expected, soybean fatty acids obtained
within the accepted range for feed fats [lq.
from crude soybean oil are very high in unsatThe main foreign materials found were bone
urated fatty acids (UFA), with a high level of
particles in tallow and unfiltered food residues
linoleic acid. Very little difference in fatty acid
in RG.
composition existed between the two soybean
Free fatty acid content was, as expected,
oils. The fatty acid composition of RG varied
very high in PFFA. This product is obtained by
dependmg on the original frying oil used. The
an efficient physical distillationprocess during
origin of RG1 and RG2 is oleine, a refined oil
refining of crude palm oil; only small amounts
produced from palm oil specially for food
of neutral oil and triglycerides are released
frying; consequently, these two RG are more
during this industrial procedure. SBFFA had a
lower free fatty acid content, as it is produced
saturated than RQ, which is produced from
by a less efficient chemical process. The oil is
soybean oil.
combined with caustic soda to neutralize the
The determined M E n levels of the fats
free fatty acids. A soapstock is formed which
and blends from both labs are summarized in
emulsifies approximately its own weight in
Table 4. Accordmg to these results, the lowest
neutral oil, so that only about half of the fatty
AME, values occurred in both fats from the
RESULTS
DISCUSSION
TABLE 3. Fatty acid composition of experimental fat products
*PFFA = Palm free fat acids; SBFFA = soybean free fatty acids +acidulated soa stock; CPO =Crude palm oil;
Tallow 1 and Tallow2 = k e f tallow samples provided by two different renderers;RG and RG2 = Restaurant greases
from oleine palm oil; and RG3 = Restaurant grease from soybean oil.
f
Iv a l u e s for full-fat palm kernel meal are for the fat portion (47.1%) of this product.
JAPR
FAT BY-PRODUCTS
268
TABLE 4. Nitrogencorrected metabolizable energy of experimental products calculated directly or by
metabolizable energy nitrogen corrected (direct determination using heat of combustion values of
rent metabolizable energy (calculated by digestibilitycoefficient).
oil palm, CPO and its main by-product PFFA,
and Tallow 1. This is in agreement with the
high saturated fatty acid composition and low
UFASFA ratio of these fats. PFFA showed the
lowest value among the saturated fats, which is
also explained by its high free fatty acid (FFA)
level. In fact, WEeman and Salvador [18] confirmed that the combination of high saturation
and high free fatty acid content reduces the
digestibility and AME content of fats. A high
FFA level, which indicates that the fat has a
high FFAglyceride ratio, reduces the formation of micelles. Reduced micelle formation
mainly affects absorption of SFA of longer
carbon chains, such as those predominant in
palm oil and tallow.
The energy levels for CPO and tallow are
very close to those values reported by the NRC
[2]. These figures are based on research
conducted in several parts of the world, particularly the work of Sibbald [6], Sibbald
and Kramer [q, and Huyghebaert et al. [3].
The values reported for refined palm fat
are 5300 and 5800 kcaVkg [3]. Wiseman and
Salvador [18] found AME, values ranging
from 6620 k&g for 2.5-wk-old broilers and
7720 kcal/kg (7.5-wk-old) for crude palm oil
with 5.75% FFA content to 3537 (2.5 wk) and
6573 kcaVkg (7 wk) for PFFA with 91.75%
FFA.
Tallow showed a digestibility and AME,
close to that of CPO and higher than those
values for PFFA (5980 and 6112 kcal/kg).
Huyghebaert et al. [3] reported an average of
6205 kcaVkg for refined tallow; Wiseman and
Salvador [19] found values from 6238 k&g
for tallow with 54.5% FFA to 7385 k&g for
a 13.8% FFA content.
On the other hand, SBFFA showed values
of 8349 to 8598 kcal/kg associated with its
high fat digestibility, which results from a
high UFASFA ratio. Values calculated from
digestibility coefficients were somehow lower
(8014 to 8252 kcal/kg). A product similar to
this with a content of 51.6% FFA was determined to have 8341 k&g [18]. On the other
hand, values of 6118 kcalflrg determined by
direct method and 6865 kcal/kgby digestibility
had been reported for acidulated soapstock
and 8806 and 8376 k&g for crude soybean
oil [3].
Research Report
269
ZUMBADO et al.
Restaurant grease obtained from restaurants using soybean oil (RG3) also had a
higher AME, value. In the case of RG1 the
AME, value is more than 1Mcal below the
value for RG3 because of the higher saturation
and higher FFA content of RG1 (Tables 1and
3). As was mentioned before, RG1 was obtained from restaurants that use oleine from
palm oil.
Blends of fats, mainly those with
SBFFA, produced interesting results related
to synergism of fats. The blends of PFFA,
tallow, or RG with SBFFA showed AME,
values higher than expected based on the
arithmetic mean calculated from the individual AM& values of the two components of
the blends. This higher AME, occurs because
the presence of UFA during micelle formation
increases the digestibility of the SFA [5, 61.
The blend of SBFFA with Tallow or PFFA
improved the AME, by 383 and 1051kcal/kg,
respectively, from the expected value. A
synergistic effect was also noticed for the
CPO +PFFA blend ( + 319 kcalkg), even
thou both are saturated fats. These results
are in agreement with previous preliminary
findings from our laboratories [19,20]. Differences in digestibility and AME, between
the values determined at UCR and ID-DLO
exist for PFFA, PFFA + SBFFA, and
SBFFA + Tallow. These differences may be
explained in part by the composition of the
basal diets (Table 2). The ID-DLO diet contained about 9% less corn than the UCR basal
diet and 10% cornstarch, an ingredient not
included in the UCR diet. The UCR diet thus
contains more corn oil and, in turn, more
unsaturated fatty acids than the ID-DLO
diet, which may have improved the absorption
of the more saturated fats such as PFFA and
Tallow. These effects of the basal diets have
been previously reported [13].
The results also show that AME values
of saturated fats calculated from digestibility values are generally higher than values
of fats as determined by the direct method.
This may occur because saturated fatty
acids react with calcium in the digestive tract,
forming soaps that are less solvable in extraction solvents than soaps from unsaturated
fatty acids. The solvents used for extraction
and analysis of excreta fats thus tended to
extract more unsaturated than saturated fats,
even though a special method was used to
determine fat content [I 41. This method
stimulates hydrolysis of soaps before the
process of extraction. However, some saturated fatty acids may not be extracted, which
can yield high AME values for saturated
fats, a result that occurs with most methods of
extraction.
Table 5 shows the chemical composition
of full-fat palm kernel meal on a dry matter
basis. This product contains a large amount
of fat (47.1%) and 8.7% crude protein. In
this sample, the level of crude fiber is rather
low compared to values above 10% reported
in the literature [7, 21, 22). This is probably
due to a lower content of hull residues in the
final meal.
The oil in full-fat palm kernel meal
showed a digestibility of 83.3% and an AME
value of 4230 kcal/kg. This AME value is in
close agreement with previous reports by
Zumbado and Jackson [21], who found a
content of 4420 k&g TME, for kernel with
no hull contamination, and a decrease of
21.45 kcal/kg for every 1% hulls present in
the kernel as foreign material.The high digestibility of kernel oil is attributed to its high
content of short-chain fatly acids despite its
high saturation.This is an0 ther example of the
effect of the fatty acid composition of a fat
upon its utilization by poultry [23,24].
Broiler performance jiom 18 to 29 days
(Table 6) shows highly significant differences
between treatments (P e .05), especially for
feed conversion. Birds fed 1he SBFFA diet had
the best feed conversion ratio (FCR), as was
expected considering its high digestibility and
AME, content. On the other hand, broilers
that received the PFFA diet showed the lowest
weight gain and worst FCR among all treatments; these results are at1ributable to its low
digestibility (Table 4). An intermediate re-
COMPONENT
Dly matter
Crude protein
Crude fat
%
93.6
8.7
47.1
Ash
1.9
Crude fiber
8.8
AM%, kcavkg DM
AM&, kcalkg As Is
4230
3960
JAPR
FAT BY-PRODUCTS
270
Broilers fed full-fat palm kernel meal did
not perform as well as its AMEnlevel led us to
expect. This may be explained by the lower
AM& content of the diet compared to most
of the other experimental diets except for the
diet with PFFA (Table 4). The palm kernel
meal diet may have had more problems related
to the amino acid content and balance and to
having a higher crude fiber content than the
diets with pure fats. These aspects require
further study as little information is available
on total and digestible amino acid content of
full-fat palm kernel meal.
sponse occurred with RG1, CPO, and tallow.
When tallow, and especially PFFA, were
mixed with SBFFA, bird performance was
greatly improved even beyond the expected
values. This response is probably due to the
fatty acid synergism mentioned before [23,24].
Blending PFFA with CPO showed only a sllght
beneficial effect compared to the results obtained with the two fats fed separately. This
means that synergism between these two fats,
as in acid palm oil [q,
does not occur as
efficiently as in blends where one component
is clearly more unsaturated.
%bird
%bird
SBFFA
CPO
Tallow 1
I
I
106Sa
1130"
I
I
1132'
636'
634'
1
dg
I
I
1.68a
1.7P
629'
1.80'
RG1
1112"
62T
I.?
+
PFFA +SBFPA
1121"
S d
1.88=
PFFA CPO
I
1088ab
I
622'
SBFFA +Tallow 1
1102"
637
Palm kernel meal
1121"
594b
Effect of diet (P-value)
LSD (P <
0.012
33
<0.001
22
I
1.7SbC
1.73b
1.89e
< 0.001
0.042
CONCLUSIONS
AND APPLICATIONS
1. The oil and fat products that are available in a region or country must be properly analyzed
by chemical and biological means to obtain the best use of them and produce the right
blends for animal feeding purposes.
2. The fat blends with the w e s t AMEn level are those that include unsaturated fat products,
such as acidulated soybean soapstock, soybean distilled fatty acid, and/or restaurant
greases. When these are mixed with palm free fatty acids, tallow, or crude palm oil a
synergistic effect occurs, yielding a higher AMEn level in the blend. Restaurant greases
from soybean oil showed up to 20% more AMEn than restaurant greases from palm oleine.
3. Nutritionists may choose for feed formulation the higher AMEn values f o b d in this
research, as the level of the fats in the experimental diets (10%) was much higher than the
levels regularly used in practical diets. The large differences in AMEn values for PFFA
obtained by the two laboratories indicate the need for more research on this substance.
I
I
I
Research Report
271
ZUMBADO et al.
REFERENCESAND
Noms
1. Dale, N.M., 1988. Defming the value of fats in
ultry diets. Pages 26-33 in: Proc. ArkansasNutr. Conf.,
Kyettcville, AR.
2. National Research Council, 1994. Nutrient Re-
uirements of Poult . 9th Rev. Edition. Natl. Acad.
$res, Washington, D Z
3.Huyghebaert, G., G. De Munter, and G. De G m ( e ,
1988.The metabolizable energy of fats for broilers in
relation to their chemical composition. Anim. Feed Sci.
Tech. m45-58.
4.Renner, R And F.W. Hill, 1960.The utilization of
corn oil,lard, and tallow by chicks of variousages. Poultry
Sci. 39849-854.
5. Sibbald, LR and J.K. Knuner, lW7. The true
metabolizable energy value of fats and fat mixtures.
Poultry Sci. 562079-2086.
6.Sibbald, 1.R ,1978.The true metabolizable energy
value of mixtures of tallowwith either soybean oil or lard.
Poultry Sci. 57473477.
7.Zumbado, M.,1990,Utilizaci6n de productos de la
alma africana en la alimentaci6n avlar. Avicultura
rofesional7:137-146.
f : ’
8.The gums from crude saybean oil are hyd,X”d by
using steam and chemical solutions (NaCl and 6 0 4 ) .
Dehydration and centrifugation then render hydrolyzed
soybean oil. On the other hand, the soa stock obtained
from the deodorization of crude oil by &OH and water
is treated with sulfuric acid and steam, then centrifuged
and dehydrated. The final product is the acidulated
soapstock, mainly free fattyacids,which is combined with
the other two products to obtain SBFFA or hydrolyzed
soybean oil.
9. Moisture in fat arises from slight emulsification
during processing or storing. High moisture levels will
cause the fat to be more easily oxidized. Impurities are
mainly meat, bone particles, metals, or food residues that
remain after processing or are picked u during stora e
of the fat. Unsaponifiables are any solubfe material in k t
that will not convert into soap when mixed with an alkali.
10. Association of Omcia1 Analytical Chemists,
1982. Official Methods of Analysis. Assn. Offic. Anal.
Chemists, Washington, DC.
11. A f t e r addition of an internal standard
(heptadecanoicacid),theboundand freefattyacids in the
fat samplesweremethylated by a two-stepprocedure.The
fatty aad methyl esters were analyzed by gas chromato
raphy on a Carlo Erba Mega GC with automatic c o g
on-column injector, flame ionization detector, and capilData acqulsilary column (ChromapackCP-wax 52 a).
tion and processing was performed with a Hewlett
Packard Labdata System. The fat in the palm kernel was
isolated by the solvent extraction method, but with the
other products this step was omitted.
12.Badings, H.T.and C. De Jong, 1983.Glass capillaly
gas chromatography of fatty acids methyl esters. A
study of condihons for the quantitativeanalysis of shortand long-chain fatty acids in lipids. J. Chromatography
279:49>506.
13.Sibbald,I.R, 1982.Measurement of bioavailable
energ: in poultIy feedingstuffs: A review. Can. J. Anim.
Sci. 983-1048.
14.Berntrop IS0 6498,Official Journal of the European Communities, 1984.No L 15. pp. 29-30.
15.Genstal 5 Committee, 1587.Genstat 5 Reference
Manual. Release 3.1.Rothamsttd Experimental Station.
Clarendon Press, Oxford, England.
16. SAS Inslitule, Inc, 1988. SAS/STAT User’s
Guide. SAS Institute, Inc., Cary NC.
17.National Renderers Asstciation, 1993/94.Pocket
Information Manual. A Buyer‘s Guide to Rendered
Products. AsbuIy Publication LId., U.K.
18.WLscman, J. and F. Salvridor, 1991.The influence
of free fatty acid content and degree of saturation on
the apparent metabolizable energy value of fats fed to
broilers. Poultry Sci. 70573-582.
19. Kwakernaak, C., C.W. Scheele, A.C.J.M.
Smulders, and M. Zumbado, 1595.Synergistic effect of a
blend with soybean free fatty acids and palm free fatty
acids on the rformance of brlilers. Pages 242-243 in:
PrOC.XIXwgeSA Meeting, Antalya, Turkey.
20. Smolders, A.C.J.M., C. Kwakernaak, R.P.
Kwakkel, and M. Zumbado, 1996. Energy values of
ergistic effects of blends
different vegetable fats and
in broiler diets. Page 3 in: X x . XX WPSA Meeting,
New Delhi, India.
21. Zumbado, M. and F. Jackson, 1996.Efecto de la
presencia de endocarpo en el palmiste integral
)sobre su valor nutritilro. I. Nivel de endocarpo,
caractenzacidnde la fibra cruds y contenido de energ’a
metabolizable. Agronomia Costamcense 20:141-144.
(w
22. Jackson, F. and M. Zmibado, 1996. Efecto de la
presencia de endocarpo en el palmiste integral
sobre su valor nutritivo. 11. Rendimientos
de pollos de en orde en iiiiciacibn. Agronomia
Costarricense 201h-149.
(w
23. Ketels, E and G. De Grtmte, 1989.Effect of ratio
of saturated fatty acids of the dietary li id fraction on
utilization and metabolizable mer ofadded fats in
young chicks. Poultry Sci. 68:lSM-l&.
24. Scheele, C.W. and H.AJ Verskegb, 1987.Synergistic effects of different supplementaryoils and fats on
the energy of animal fat in broiler diets. Pages 22-24 in:
6th European Symp. on Poultrr. Nutr., World’s PoultIy
Sci. Assn., Konigslutter, Germany.
25. Acid Im oil marketed in Central America is a
commercial Eend of about 55% crude palm oil with a
content of 5% FFA and 45% PFFA (90% FFA). The
result is a product with around r13% FFA.
ACKNOWLEDGEMENTS
This research was supported by the International
ScientificCooperation Programme of the Commission of
the European Communities (Contract CIl*-(JT0319).
The authorswishto thank Pilxua Poultry Corporation
S.A., Numar S.A. @alm oil company), and Industrias
Cerdas S.A. (oil by-products company) of Costa Rica
for their help in providing experimental materials and
technical support.