Review: Use of Animal Fats in Aquaculture Feeds

Abstract

Formulated aquaculture feeds are among the most expensive animal feeds on the market. These feeds are often high in lipids, the bulk of which is generally provided by fish oil. Because of its high cost and potential long-term supply problems, it is now widely acknowledged that fish oil should be used more sparingly in aquafeeds. Rendered animal fats are economical lipid sources that have been used in fish feeds for decades but their use has been greatly limited for various reasons, such as poor digestibility and nutritive value, and more recently, fear of disease transmission. Recent studies have indicated that rendered animal fats can be valuable ingredients in fish feeds. Incorporation levels equal to 30-40% of total lipid of the diet do not impose any negative effects on growth performance, feed efficiency, and product quality of most fish species studied. However, the diet must contain sufficient levels of unsaturated fatty acids (mono and polyunsaturated) to allow for proper digestibility of saturated fatty acids, and, obviously, meet essential fatty acid requirements of the fish. The use of rendered animal fats at the expenses of fish oil in aquafeeds could immediately result in significant savings for feed manufacturers.

Full text

Bureau, D. P., Gibson, J., El-Mowafi, A., 2002. Review: Use of animal fats in aquaculture feeds. In: Cruz-Suárez, L. E., Ricque-Marie,
D., Tapia-Salazar, M., Gaxiola-Cortés, M. G., Simoes, N. (Eds.). Avances en Nutrición Acuícola VI. Memorias del VI Simposium
Internacional de Nutrición Acuícola. 3 al 6 de Septiembre del 2002. Cancún, Quintana Roo, México.
Review: Use of Animal Fats in Aquaculture Feeds
Dominique P. Bureau1*, Jennifer Gibson1 and Adel El-Mowafi2
1Fish Nutrition Research Laboratory, Department of Animal and Poultry Science
University of Guelph, Guelph, ON, N1G 2W1, CANADA
Tel: 1-519-824-4120 ext. 3668, Fax: 1-519-767-0573, email: dbureau@uoguelph.ca
2Maple Leaf AgResearch
150 Research Lane, Suite 200
Guelph, ON, N1G 4T2, Canada.
ABSTRACT
Formulated aquaculture feeds are among the most expensive animal feeds on the market.
These feeds are often high in lipids, the bulk of which is generally provided by fish oil.
Because of its high cost and potential long-term supply problems, it is now widely
acknowledged that fish oil should be used more sparingly in aquafeeds. Rendered animal
fats are economical lipid sources that have been used in fish feeds for decades but their use
has been greatly limited for various reasons, such as poor digestibility and nutritive value,
and more recently, fear of disease transmission. Recent studies have indicated that rendered
animal fats can be valuable ingredients in fish feeds. Incorporation levels equal to 30-40%
of total lipid of the diet do not impose any negative effects on growth performance, feed
efficiency, and product quality of most fish species studied. However, the diet must contain
sufficient levels of unsaturated fatty acids (mono and polyunsaturated) to allow for proper
digestibility of saturated fatty acids, and, obviously, meet essential fatty acid requirements
of the fish. The use of rendered animal fats at the expenses of fish oil in aquafeeds could
immediately result in significant savings for feed manufacturers.
INTRODUCTION
Formulated aquaculture feeds are among the most expensive animal feeds on the market.
The production of these feeds, particularly for carnivorous finfish species, has been
dependent on the use of significant amounts of fish oils. Fish oils are highly digestible,
while providing essential fatty acids (highly unsaturated omega-3 fatty acids),
phospholipids, cholesterol and fat soluble vitamins. Besides the ecological and ethical
concerns with the use of fish oils in aquafeeds (Naylor et al., 2000), there is also a growing
economical concern related to the cost and availability of fish oil (Coutteau et al., 2002). As
a result, steps need to be taken to reduce the dependence on the use of fish oil in aquafeeds.

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 488
Rendered animal fats, because of their low costs and wide availability, are interesting
alternatives to fish oil. Rendered fats are produced from recycled animal and poultry by-
products, such as slaughter by-products, trimmings, fat, bone, and hides. Some rendered
fats include recycled restaurant grease. Rendered fats, such as tallow, lard, and yellow
grease, have found wide use in feeds for livestock, poultry, and swine (Prokop, 1996).
However, the use of these products in aquafeeds has been limited or even avoided in the
past for various reasons, such as poor digestibility, quality variability, impacts on growth
and product quality, and more recently, fear of disease transmission. An increasing number
of studies are showing that these concerns have little relevance nowadays and that rendered
animal fats can be valuable ingredients in fish feed formulation. In this paper, we present a
brief overview of studies on the use of rendered fats in aquafeeds, with a special emphasis
on tallow, the most widely available rendered animal fat.
AVAILABILITY AND PRICE OF RENDERED ANIMAL FATS VS FISH OILS
Fish oil availability is increasingly problematic since the demand for aquafeeds has grown
considerably with the expansion of the aquaculture industry. Various projections suggest
that within a decade, the demand for fish oil may be above the available supply (Coutteau
et al., 2002). Along with an increase in demand, the price of fish oil has also risen
considerably in recent years (Hardy, Scott & Harrell, 1987). The market price for fish oil
has varied between USD $0.20 and $0.80/kg over the past decade (Coutteau et al., 2002).
Current (summer 2002) market price is around USD $0.60/kg, which is considerably more
than feed-grade rendered animal fats. Substantial savings could, therefore, be made
immediately by substituting some of the fish oil in feed formulae with these more
economical lipid sources.
In 2001, a US census reported that the production of rendered products in the USA was 8.3
billion kg, half of which was rendered fats, mainly tallow and grease (Rudbeck, 2002).
Rendered fats are a very diverse group of ingredients. A partial list of different types of
rendered fats and a brief description of their characteristics is presented in Table 1.

Review: Use of animal fats in aquaculture feeds
489
Table 1. Types and characteristics of rendered fats.
Type of Rendered Fat Characteristics
Feed-Grade Animal Fat Derived from by-products of many species, primarily beef
and pork
Unsaturates to saturated (U to S) ratio between 1:1 and 1.6:1
depending on material used
Purchased by a minimum or maximum titre or on a
guaranteed U/S FA range.
Poultry Fat Fat from poultry by-products.
U to S ratio about 2:1
A large amount of the product is sold for use in companion
animal rations.
Choice White Grease Derived mainly from the rendering of pork tissue.
U to S ratio about 1:1
Certain blends of beef, pork and poultry fat are sold as
choice white grease, as they meet the specifications.
Tallow Derived from rendered beef tissue, but may contain other
animal fats.
U to S ratio 0.9 to 1.6:1
Yellow Grease Mainly restaurant grease but can contain dead stock fat
and/or dark color, high FFA and high MIU fat from any type
of rendering operation.
Many times dark color and high FFA tallow is sold as yellow
grease.
Blended Animal and
Vegetable Fat
Includes blends of all types of animal fat, vegetable oil,
acidulated vegetable oil, soapstock and /or restaurant grease.
Source: Adapted from Bisplinghoff (1997)
Contrary to fish oil prices, the price of inedible tallow and greases has decreased in the last
5 years by 40-50% to a current price of about USD $0.30/kg for choice white grease and
tallow. Other rendered fats, such as yellow grease and animal vegetable blends are trading
for even lower price. Price for rendered fats are unlikely to move dramatically over the next
few years.
Based on their economical price and wide availability, rendered animal fats should be given
due consideration as substitutes for part of the fish oil component of current fish feed
formulae. Based on the current market prices, the cost of aquafeed could be reduced by
about USD $3/tonne for every percentage point (1%) of fish oil replaced by rendered fats.
By using 8% tallow, at the expense of 8% fish oil, in a salmonid fish feed (lipid level = 20-
30%), about USD $24/tonne fish feed could be saved in ingredient costs. This type of
saving is very significant, and there are very few other modifications (e.g. fish meal
replacement) to current salmonid feed formulae that could results in such substantial
savings.

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 490
EFFECT ON FEED QUALITY
Feeds containing high levels of fish oils also contain high levels of polyunsaturated fatty
acids which can make them more susceptible to oxidation during feed manufacturing and
storage (Greene & Selivonchick, 1990). Feed containing some rendered animal fats, such as
lard and tallow, may have a lower susceptibility to oxidation (Watanabe 2002; Dosanjh et
al., 1984).
DIGESTIBILITY
The ability of fish to use rendered animal fats as an energy source is dependent mainly
upon the digestibility of the ingredient. Studies have suggested differences in the
digestibility and nutritive value of lipid sources with different fatty acid profiles at different
water temperatures. Cho & Kaushik (1990) presented the results from an experiment
indicating that the apparent digestibility coefficients (ADC) of fish oil and plant oils
(rapeseed, soybean and linseed) remained high (ADC = 80-95%) over a wide range of
water temperatures (5 to 15oC). However, ADC of lard and tallow (lipid sources high in
saturated fatty acids) were affected by the water temperature and lower than that of oils.
This suggests strong interactions between the melting point of the lipid employed and water
temperature on apparent digestibility of lipids (Table 2).
Table 2. Apparent digestibility coefficients (ADC, %) of oils and fats fed at different water temperatures to
rainbow trout.
Water Temperatures
Oils and Fats Low/high melting point oC 5oC 10oC 15oC
Fish Oil 80 81 81
Rapeseed Oil 0/-12 85 89 90
Soybean Oil -7/-8 92 93 91
Linseed Oil -18/-27 92 95 95
Lard 28/48 70 76 78
Tallow 45/48 58 64 66
Source: Cho and Kaushik (1990)
The ADC of lard and tallow were clearly poorer at lower water temperatures, in contrast
with the lack of effect of water temperatures on the lower melting point oils. Other
evidences are provided by Schwarz et al. (1988) who found that the digestibility of lipids
depended on the fatty acid composition. Fish feeds that contained fish or vegetable oils, and
had significantly higher levels of omega-3 and omega-6 fatty acids, were digested about 6%
better than feed with rendered animal fats, and with a significantly higher saturated fatty
acids content. There are a number of other evidences in the literature that the ADC of
saturated fatty acids are less than ADC of unsaturated fatty acids.

Review: Use of animal fats in aquaculture feeds
491
Other observations suggest, however, that the ADC of tallow is high for rainbow trout
provided the diet contains a certain amount of fish oil (and/or other lipid sources rich in
mono and polyunsaturated fatty acids). Bureau, Harris & Cho (1997) found that there was
no difference in the apparent digestibility coefficient (ADC) of lipid (94%) of a feed with
16% fish oil and that of a feed with 8% fish oil and 8% tallow at a low water temperature
(7.5oC). At 15oC, the ADC of lipid of the diet comprised of 8% fish oil and 8% tallow was
only slightly lower than that of the feed comprised of 16% fish oil (95 vs. 98%) (Table 3).
Table 3. Lipid digestibility and growth performance of rainbow trout (initial weight = 7 g/fish) fed practical
diets containing fish oil or fish oil and tallow combination reared at 7.5 or 15ºC for 12 weeks.
Water Temperature
7.5ºC 15ºC
Diet 1 Diet 2 Diet 1 Diet 2
Ingredients
Fish meal, herring, 68% CP 50 50 50 50
Corn gluten meal, 60% CP 20 20 20 20
Fish oil, herring 16 8 16 8
Beef tallow, fancy, bleachable - 8 - 8
Composition
Digestible Protein (DP), % 44.0 43.5 44.9 44.4
Digestible Energy (DE), MJ/kg 19.5 19.9 20.9 20.8
DP/DE, g/MJ 22.6 21.9 21.5 21.3
Performance
Lipid digestibility, % 93 94 98 95*
Weight gain, g/fish 13.7 13.1 38.1 39.2
Feed efficiency, gain:feed (as is) 1.32 1.27 1.22 1.15
Retained energy, % digestible intake 47 47 50 48
*Significantly different from control diet (Diet 1).
Source: Bureau et al. (1997)
The difference in estimates of digestibility of diets containing rendered animal fats between
studies is likely due to the synergetic effect of polyunsaturated fatty acids on the
digestibility of saturated fatty acids, a well-described phenomenon in poultry (Sibbald,
Slinger & Ashton, 1962; Sibbald, 1978). The low digestibility values reported, in early
studies, for highly saturated lipid sources may therefore be an artifact of the methodology
used. For example, the study presented by Cho & Kaushik (1990) used a reference diet
with very low levels of lipids (3 –5%). This reference diet was then supplemented with
significant amounts of the lipid sources tested (fish oil, soya oil, lard, tallow), to produce
test diets in which a very significant proportion of the lipids was provided by the lipid
tested. It has been demonstrated, more than 40 years ago, that highly saturated lipids, when
used alone in the diet, are poorly digested by poultry (Table 4). However, supplementation
of tallow-rich diets with small amounts of a lipid sources rich in polyunsaturated fatty acids

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 492
(e.g. soya oil), resulted in a significant improvement of the digestibility of saturated fatty
acids and, consequently, total lipids of the diet (Sibbald et al., 1962; Sibbald, 1978).
Table 4. The metabolizable energy values of tallow, crude soybean oil, and a 50/50 mixture of the two fats fed
to poultry.
Type of Fat Metabolizable Energy
kJ/g
Tallow 25
Crude Soybean Oil 36
50% crude soybean oil + 50% tallow 34
Adapted from Sibbald et al. (1962)
Available results suggest that aquafeeds containing rendered animal fats, should be
formulated to contain sufficient amounts of monounsaturated and polyunsaturated fatty
acids to allow proper digestibility of saturated fatty acids. A simple analysis of the results
of Bureau et al. (1997) suggest that when saturated fatty acids levels of the diet should not
exceed 35-40% of total fatty acids of the diet of rainbow trout. In excess of that level, the
ADC of lipids of the diet can decrease quite significantly (Figure 1). This simple analysis
also suggest that it might be wise to assume a slightly lower ADC for lipid and energy for
rendered animal fats, compared to fish oil, especially when formulating diets rich in
saturated fatty acids. These are only preliminary recommendations. There is a need for a
more comprehensive assessment of the effect of dietary fatty acids composition and lipid
levels, and water temperature on ADC of lipids.
Figure 1. Apparent digestibility coefficient (ADC) of lipid of diets (ca. 18% crude lipid) containing increasing
levels of saturated lipids fed to rainbow trout at 7.5 and 15˚C. Data from Bureau et al. (1997)
y = -0.004x2 - 0.1099x + 102.13
R2 = 0.8719
y = -0.042x2 + 2.2206x + 63.915
R2 = 0.4421
75
80
85
90
95
100
0 10203040
Saturates (% of total fatty acids)
ADC Lipid (%)
7.5 C
15 C

Review: Use of animal fats in aquaculture feeds
493
EFFECT ON PERFORMANCE
Table 5 summarizes the results of about two dozen studies on the use of rendered fats as an
alternative fat source in the diet of various fish species. A number of these studies
suggested that diets containing rendered fats, such as tallow and lard, may not be able to
support optimal growth performance. Results from several other studies indicate that diets
containing significant amounts of rendered fats are, indeed, able to support optimal growth
performance of various fish species. While some differences in the results of some studies
are difficult to explain, it is apparent that when rendered animal fats incorporation level
represent more than half of the crude lipid of the diet, a significant reduction of
performance of the fish is generally observed. Lower incorporation levels of rendered
animal fats in the diet had no effect on performance of the fish (compared to fish oil-based
control diets) in almost all reported studies (Table 5). It is also noteworthy that rendered
animal fats, such as tallow, had no negative effect on reproductive parameters (Hertrampf
& Piedad-Pascual 2000; Pustowka et al., 2000; Watanabe et al., 1984).
As results suggest, rendered animal fats are well utilized by most fish species provided that
the essential fatty acid requirements are met and that the diet contains sufficient mono or
polyunsaturated fatty acids must be met to ensure proper digestibility of saturated fatty
acids.
Table 5. Summary of studies on use of rendered fat in the diet of various fish species.
Species Diet Composition Effect on Performance Reference
Rainbow
trout
Oncorhynchus
mykiss
10% beef tallow
Crude Lipid
=10%
Significantly lower weight gain and feed
conversion ratio (FCR) than with pollock
liver oil
Takeuchi et al., 1978
6% beef tallow+
4% pollock liver oil
Crude Lipid
=10%
No effect on weight gain, FCR or survival
Small reduction in digestible energy
Takeuchi et al., 1978
4% hydrogenated
beef tallow+ 4%
pollock liver oil
Crude Lipid
=10%
No effect on weight gain, FCR or survival
Small reduction in digestible energy
Takeuchi et al., 1978
4.8% lard + 7.2%
beef tallow
Crude Lipid
=18%
Reduced weight gain Watson, 1981

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 494
Species Diet Composition Effect on Performance Reference
7% beef tallow +
7% feed oil
Crude Lipid
=19%
Slow growth for first month (15% gain)
No adverse effects on reproduction
Watanabe et al., 1984
6% chicken fat,
pork lard, or beef
tallow
Crude Lipid
=13%
No effect on weight gain or FCR
No effect on carcass composition
Absence of physical deformities across all
groups
Greene &
Selivonchick, 1990
8% beef tallow +
8% fish oil
Crude Lipid
=21%
No effect on weight gain and FCR
No effect on carcass proximate composition
Bureau, 1997
8% herring oil and
8% beef tallow
Total Lipid =18%
No effect on weight gain, FCR, retained
nitrogen, and recovered energy
Bureau et al., 1997
12% tallow
Crude Lipid = ?
High cholesterol levels in spermatozoa
Produced higher percentage of eyed embryos
Pustowka et al., 2000
Coho salmon
Oncorhynchus
kisutch
4% beef tallow +
12% salmon oil
Crude Lipid
=16%
No effect on weight gain
No effect on body protein, moisture and ash
Yu & Sinnhuber,
1981
8% beef tallow +
8% salmon oil
Crude Lipid
=16%
No effect on weight gain
No effect on body protein, moisture and ash
Slight increase in fish body lipid saturation
Yu & Sinnhuber,
1981
12% beef tallow +
4% salmon oil
Crude Lipid
=16%
Significantly lower weight gain
No effect on body protein, moisture and ash
Yu & Sinnhuber,
1981
8.6% lard
Crude Lipid
=12%
No effect on weight gain, FCR, and energy
utilization
No effect on body composition
No effect on fish health or survival
Dosanjh et al., 1984
4.3% lard + 4.3%
herring oil
Crude Lipid
=12%
No effect on weight gain, FCR, and energy
utilization
No effect on body composition
No effect on fish health or survival
Dosanjh et al, 1984
4.3% lard + 4.3%
canola oil
Crude Lipid
No effect on weight gain, FCR, and energy
utilization
No effect on body composition
Dosanjh et a.,. 1984

Review: Use of animal fats in aquaculture feeds
495
Species Diet Composition Effect on Performance Reference
=12%
No effect on fish health or survival
Chinook
salmon
Oncorhynchus
tshawytscha
5% beef suet + 3%
linseed oil
Crude Lipid
=15%
No effect on weight gain or FCR
No effect on moisture, protein and lipid
content of carcass
Mugrditchian et al.,
1981
6.5% beef suet +
1.5% linseed oil
No effect on weight gain or FCR
No effect on moisture, protein and lipid
content of carcass
Mugrditchian et al.,
1981
3.0% beef suet +
1.5% linseed oil +
3.5% salmon oil
No effect on weight gain or FCR
No effect on moisture, protein and lipid
content of carcass
Mugrditchian et al.,
1981
8.2% lard
Crude Lipid
=16%
No effect on weight gain and FCR
High protein conversion
No effect on whole body proximate
constituents
Dosanjh et al., 1988
4.1% lard + 4.1%
canola oil
Crude Lipid
=16%
No effect on weight gain and FCR
High protein conversion
No effect on whole body proximate
constituents
Dosanjh et al., 1988
4.1% lard + 4.1%
herring oil
Crude Lipid
=17%
No effect on weight gain and FCR
Highest protein conversion
No effect on whole body proximate
constituents
Dosanjh et al., 1988
Atlantic
salmon
Salmo salar
1.9% herring oil
and 5% beef tallow
Crude Lipid
=20%
No effect on weight gain, FCR or proximate
composition of the fillets
Lower level of carotenoid pigments
Hardy et al., 1987
4.5% lard+ 3.5%
corn oil+ 1%
canning oil
Crude Lipid =?
No effect on weight gain as compared to
control diet
Bell et al., 1989
Channel
catfish
Ictalurus
punctatus
10% beef tallow
Crude Lipid
= 10%
Higher weight gain than with safflower oil
Lower FCR than safflower oil
Lowest carcass lipid content
Stickney & Andrews,
1971
7% beef tallow
Crude Lipid =7%
Lower weight gain at high temperatures
No effect on weight gain at low temperature
High survival rates
Fracalossi & Lovell,
1994b
2.3% beef tallow +
2.3% corn oil +
2.3% menhaden oil
Crude Lipid =7%
High survival rates
Significantly higher weight gain at high
temperatures
No effect on weight gain at low temperature
Fracalossi & Lovell,
1994b

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 496
Species Diet Composition Effect on Performance Reference
7% beef tallow
Crude Lipid =7%
Lowest leukotriene B (LTB) production
Lowest weight gain
Fracalossi et al., 1994
2.3% beef tallow +
2.3% corn oil +
2.3% menhaden oil
Crude Lipid =7%
Lowest LTB production
Lowest weight gain
Fracalossi et al., 1994
2% beef tallow
Crude Lipid =?
No effect on growth, FCR, and survival Li et al., 1994
7% beef tallow
Crude Lipid =7%
Low weight gain at high temperature
No weight gain at low temperature
Fracalossi & Lovell,
1995
2.3% beef tallow +
2.3% corn oil +
2.3% menhaden oil
Crude Lipid =7%
High weight gain at high and low
temperature
Fracalossi & Lovell,
1995
2% beef tallow +
2.7% fish oil
Crude Lipid =ca.
8%
No effect on survival, live weight at harvest,
yield, and dressing percentage
No effect on muscle lipid levels
No effect on liver and muscle moisture
content
Reigh & Ellis, 2000
4% beef tallow +
2.7% fish oil
Crude Lipid = ca.
8%
No effect on survival, live weight at harvest,
yield, and dressing percentage
No effect on muscle lipid levels
No effect on liver and muscle moisture
content
Reigh & Ellis, 2000
Common
Carp
Cyprinus
carpio L.
4.5 beef tallow
+5% feed oil
Crude Lipid
=10%
Depressed weight gain
No effect on FE
No effect on feed intake
No effect on lipid content
No effect on energy utilization
Murai et al., 1985
9.5% beef tallow +
5% feed oil
Crude Lipid
=15%
Depressed weight gain
No effect on FE
Decreased feed intake
Increased carcass lipid content
No effect on energy utilization
Murai et al., 1985
12% beef tallow +
1.4% linseed oil
Crude Lipid = 16
%
No effect on growth
Lowest carcass fat content (11.3%)
No effect on protein/ash content
Lowest dry matter content
Schwarz et al., 1988
African
Sharptooth
Catfish
10% tallow
Crude Lipid
=10%
Chemical composition of muscle strongly
influenced by diet
Lower growth than fish fed sunflower oil
Hoffman & Prinsloo,
1995

Review: Use of animal fats in aquaculture feeds
497
Species Diet Composition Effect on Performance Reference
Clarias
gariepinus
diet
Hybrid tilapia
Oreochromis
niloticus x O.
aureus
5% lard
Crude Lipid =5%
Significantly lower weight gain, protein
efficiency ratio (PER) and higher FCR
Significantly lower protein deposition
No effect on survival
Chou & Shiau, 1999
2.5% lard + 2.5%
corn oil
Crude Lipid =5%
Significantly lower weight gain, PER and
higher FCR
Significantly lower protein deposition
No effect on survival
Chou & Shiau, 1999
2.5% lard + 2.5%
cod liver oil
Crude Lipid =5%
Significantly lower weight gain, PER and
higher FCR
Significantly lower protein deposition
No effect on survival
Chou & Shiau, 1999
1.7% lard + 1.7%
corn oil + 1.7% cod
liver oil
Crude Lipid =5%
Significantly higher weight gain, and PER.
Higher FCR
Greater protein deposition
No effect on survival
Chou & Shiau, 1999
Blue tilapia
Tilapia aurea
2-14% beef tallow
Crude Lipid =2-
14%
No effect on weight gain
No effect on FCR
Stickney &
McGeachin, 1984
IMMUNE RESPONSE
The effect of fatty acid profile of the diet on health and immune function of fish has been
examined in a few studies. It is clear from results of studies that a deficiency in any
essential fatty acids may lead to biochemical abnormalities that may affect health of fish
(Lall, 2001).
It has been suggested that the balance of n-3 and n-6 fatty acids may have an effect on
immune competence of fish (Lall, 2001). The nature and magnitude of the response may be
different between fish species. In general, diets high in n-6 PUFAs should enhance the
immune responsiveness, since these fatty acids, through conversion to arachidonic acid
(ARA), lead to the production of very potent proinflammatory eicosanoids. Diets high in n-
3 PUFAs should result in lower immune responsiveness due to the fact that these fatty
acids, through conversion to EPA, lead to the production of eicosanoids which are less
potent than ARA-derived one (Lall 2001). This predicted effect is, however, rarely clear, as
suggested by differences in results between studies (Laal, 2001; Sheldon & Blazer, 1991;
Fracalossi & Lovell, 1994b).
Fracalossi & Lovell (1994b) found that channel catfish fed 7% menhaden oil (rich in 18:3n-
3) had a higher mortality rate when exposed to E. ictaluri than fish fed a similar diet
containing beef tallow. As a result, these authors suggested that a mixture of n-3 PUFA and

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 498
18:2n-6 (provided by menhaden oil, beef tallow and corn oil) might be desirable in feeds to
optimize immuno-competence of channel catfish. A study conducted at the University of
Guelph suggest no significant effects of animal fats incorporation (as well as wide variation
in the fatty acid composition) in the diet on different non-specific immunity parameters of
rainbow trout (Bureau et al., 1997) (Table 6). More detailed studies on this topic are being
conducted by other research groups in Canada. So far, there is no other published evidence
indicating that use of animal fats has any effect on health and immune competence of fish,
provided the diet meet the essential nutrient requirements of the fish.
Table 6. Non-specific immunity of rainbow trout fed the experimental diet for 12 weeks.
Packed cell
volume
Lysozyme
NBT
no SOD
NBT
+SOD
Difference
SOD
Diet
%
U/mg soluble
protein
U/106 cells
U/106 cells
U/106 cells
7.5oC
16% fish oil
35.2
65.8
0.369
0.199
0.170
8% fish oil
+8% tallow
34.4
70.3
0.416
0.248
0.168
15oC
16% fish oil
33.1
101.6
0.364
0.269
0.096
8% fish oil
+8% tallow
34.1
85.1
0.241
0.127
0.114
Temp
NS
*
*
NS
***
Diet
NS
NS
NS
NS
NS
Temp*Diet
NS
NS
NS
NS
NS
Data from Bureau et al. (1997)
PRODUCT QUALITY
The fatty acid profile of rendered fats differs greatly from fish oils. Differences can be seen
in that the ratio of saturated fatty acids to unsaturated fatty acids or in the proportion of
different unsaturated fatty acids (mono vs. polyunsaturated). It is well-recognized that
differences in the fatty acid profile of feeds are largely reflected in the composition of the

Review: Use of animal fats in aquaculture feeds
499
fish (Hardy et al., 1987). This phenomenon of changing muscle composition with feed
composition is common to most fish species (Chou & Shiau, 1999). Hoffman & Prinsloo
(1995) found that African sharptooth catfish fed 10% tallow had the highest saturated fatty
acid concentration and the lowest polyunsaturated fatty acid content in the muscle. These
results were confirmed by Greene & Selivonchick (1990) in which trout fed diets
containing poultry fat, pork lard and beef tallow all exhibited the highest levels of saturated
fat in the muscle.
This does not mean, however, that fish absolutely deposit into the muscle the same level of
fatty acids present in the diet (Figure 2). Rather, dietary fatty acids may be deposited
according to a more narrowly defined physiological level. This is particularly the case with
phospholipids, whose fatty acid composition is more narrowly controlled than that of
triglycerides (Mugrditchian et al., 1981; Hardy et al., 1987; Dosanjh et al., 1988; Greene &
Selivonchick, 1990). Bureau et al. (1997) observed that phospholipids represented
approximatively 10-15% of the total lipid of the body of rainbow trout of 40- 100 g. These
authors also observed that the concentration of various fatty acids in the phospholipids were
much less responsive to the changes in the dietary concentration of the same fatty acids
than triglycerides did. The concentration of DHA (22:6n-6) in the phospholipid fraction of
the carcass of rainbow trout was very high (ca. 35% of total fatty acids of phospholipids),
and remained unaffected by dramatric changes in the DHA content of the diet (Bureau et
al., 1997).
It is expected that the incorporation of small amount of rendered animal fats in the diet may
have only marginal effect on flesh composition. This is probably especially true in the case
of lean fish, where phospholipids represent a larger proportion of total lipids. Evidence of
this can be found in Yu & Sinnhuber (1981) and Bureau et al. (1998) who found that body
lipid saturation of coho salmon and young rainbow trout (Figure 2) increased only slightly
as the concentration of saturated fatty acid in the diet increased.

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 500
Figure 2. Relationship between saturated fatty acid concentration of the lipid of the diet and saturated fatty
acid composition of the fillet of rainbow trout reared at two water temperatures. Data from Bureau et al.
(1997).
The frequently voiced concern that feeding rendered animal fats may “change” the fatty
acid profile of the flesh of fish, and result in a “different product” is often overplayed.
While it is true that there are very significant differences in the fatty acid compositions of
fish oils and rendered animal fats (Table 7), there are also great differences in fatty acid
composition of different fish oils (type of fish oil, origin of fish processed, season, etc.).
These differences will also result in variable fatty acid composition of fish fed diets
manufactured with fish oils as the sole lipid source. Not only can the fatty acid composition
of the fish be changed by replacing some fish oil with animal fats, but it may also be
intentionally or unintentionally manipulated by switching the type of fish oil being used in
the diet (Hoffman & Prinsloo, 1995). Moreover, most aquaculture products are sold as
“generic” products (as opposed to “branded” products) and producers have no
“economical” or “marketing” incentives to maintain a certain fatty acid profile or
composition for their products.
The concern that the use of animal fats will change the taste of the fish is also another
frequently voiced concern in the industry. The effect of lipid sources on the sensory
attributes of fish fed different lipid sources has been the topic of a small number of studies,
some of which are not yet published. The results from these studies suggest that lipid
source has a slight impact on sensory attributes of the flesh and that, overall, the flavor,
color and texture of fillets do not appear to be negatively affected by rendered animal fats
incorporation in the diet (e.g. Hardy et al., 1987). Tallow incorporation at a level
equivalent to 30-40% of total fat of the diet appeared to decrease the formation of rancidity
products (as assessed by TBARS) in the flesh in a number of cases (Bureau et al., 1997).
Consequently, flesh of fish fed tallow may have an improved shelf life, especially
compared to fish fed highly unsaturated fish oils.
0
10
20
30
40
0.0 10.0 20.0 30.0 40.0
Diet Saturates (weight%)
Flesh Saturates (weight%)
7.5 C
15 C

Review: Use of animal fats in aquaculture feeds
501
The balance of evidence suggest that there is, consequently, little rational behind the
concern/fear that using of rendered animal fats in aquaculture feeds will negatively affect
marketability of the product because of changes in the fatty acid composition and taste of
the fish produced.
Rendered animal fats are used in all other livestock species feeds in several countries
around the world. Since many aquaculture products (trout, salmon, catfish, tilapia) are sold
in supermarkets at prices that are very competitive to poultry, swine and beef products, it
seems logical that feed for aquaculture species be also based on the same economical
ingredients used for production of other livestock feeds.
BOVINE SPONGIFORM ENCEPHALOPATHY (BSE)
The results from many studies indicate that rendered animal ingredients available on the
market can be very useful ingredients for fish feed formulation, with relatively limited
quality problems. Therefore, the fear of BSE is now the main factor hindering the use of
rendered ingredients in aquafeeds. Europe has imposed upon herself very severe restrictions
on the use of rendered products to deal with serious animal health and consumer’s
perception issues. These measures will probably insure eradication of BSE in one or two
decades. Based on a number of cases of BSE observed, potential contamination of raw
material with BSE-causing agents appears to be mostly a problem for European rendered
ingredients. Evidence further suggests that the USA and Canada are probably free of BSE,
and highly resistant to introduction of the disease. A recent analysis suggests that the
policies, with particular reference to the FDA feed rule, should be effective in preventing
either transmission or amplification of the BSE infectious agent. Scrapies, another other
transmissible spongiform encephalopathies (TSE), is present in the USA and Canada but
evidence strongly suggest that 1) this group of diseases are different from BSE, and 2) that
scrapies is apparently not transmissible through ingestion of contaminated materials, like
BSE is.
It is also important to note that rendered animal ingredients of swine or poultry origins, as
well as lipid ingredients, such as tallow, have never been identified as being involved in the
transmission of BSE or other TSE. These materials, therefore, represent extremely low risk
materials from that point of view. Finally, to the knowledge of the authors, no TSE have
ever been reported for fish.

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 502
Table 7. Fatty acid composition of different oils and fats
Fatty
Acid
Menhade
n Oil
Cod Liver
Oil
Salmon
Oil
Herring
Oil
Soybean
Oil
Poultry
Fat
Yellow
Grease
Choice
White
Grease
Lard Tallow
14:0 10.2 2.5 4.3 5.0 0.1 0.8 1.1 1.9 1.5 3.5
16:0 23.5 9.6 15.4 11.0 12.6 23.2 17.3 21.5 25.2 27.9
18:0 4.3 2.3 2.7 2.0 4.8 5.2 11.2 14.9 14.6 20.0
18:1 n-9 15.0 14.2 24.7 20.0 24.9 43.0 56.2 41.1 40.1 42.6
18:2 n-6 1.3 2.9 2.1 2.5 48.6 17.0 9.9 11.6 13.9 2.6
18:3 n-3 1.0 4.8 1.3 0.5 7.2 1.0 2.1 0.4 1.0 -
20:4 n-6 1.1 0.5 0.6 - - - - - - -
20:5 n-3 17.3 18.1 10.4 8.0 - - - - - -
22:6 n-3 8.8 14.8 9.4 7.0 - - - - - -
Data from various sources.
CONCLUSION
The results from an increasing number of studies clearly indicate that rendered animal fats
can be very valuable ingredients for fish feed formulation. In order for animal fats to be
properly utilized by the fish, the diet must contain a significant level of n-3 and/or n-6
polyunsaturated fatty acids to meet the essential fatty acid requirements of the fish and to
allow for proper digestibility of the diet. The balance of evidence shows that rendered
animal fats incorporated at levels corresponding to 30-40% of total lipids, have no adverse
effects on growth performance, feed efficiency and product quality of most fish species
studied. Overall, the use of these low-cost alternatives to fish oil could result in immediate
and very significant savings. The only remaining hurdle in the wider use of animal fats in
aquaculture feeds is the fear of BSE and other TSE, a fear that is largely unfounded.
ACKNOWLEDGEMENTS
The financial support of the Ontario Ministry of Natural Resources (OMNR), the Ontario
Ministry of Agriculture, Food and Rural Affairs (OMAFRA), and Rothsay Inc. (Dundas,
ON, Canada) is acknowledged.
REFERENCES
Bell, J. G., Youngson, A., Mitchell, A. I., Cowey, C. B., 1989. The effect of enhanced intake of linoleic acid
on the fatty acid composition of tissue polar lipids of post-smolt atlantic salmon (Salmo salar).
Lipids 24, 240-242.
Bisplinghoff, F., 1997. Quality standard for animal and plant fats. In: National Dairy Database, University of
Maryland.
Bureau, D.P., 1997. Nutritive value of Megalac, seal oil and beef tallow for rainbow trout (Oncorhynchus
mykiss). Report submitted to Church and Dwight Co., Princeton, NJ, USA.
Bureau, D.P., Harris, A. M., Cho, C. Y., 1997. The effect of dietary lipid and long-chain n-3 PUFA levels on
growth, energy utilization, carcass quality and immune function of rainbow trout (Oncorhynchus
mykiss). Final Report of OMAFRA/University of Guelph Project Number 14250 / 95-42-12, May
1997, University of Guelph, Ontario, Canada.

Review: Use of animal fats in aquaculture feeds
503
Cho, C. Y., Kaushik, S. J., 1990. Nutritional energetics in fish: energy and protein utilization in rainbow trout
(Salmo gairdneri). World Review of Nutrition and Dietetics 61, 132-172.
Chou, B. S., Shiau, S. Y., 1999. Both n-6 and n-3 fatty acids are required for maximal growth of juvenile
hybrid tilapia. North American Journal of Aquaculture. 61, 13-20.
Coutteau, P., Ceulamans, S., VanHalteren, A., Robles, R., 2002. Fish meal and fish oil in aquafeeds-how
narrow is the bottleneck for marine fish? X International Symposium of Nutrition and Feed in Fish.
1-7 June 2002, Rhodes, Greece. Poster 38.
Dosanjh, B. S., Higgs, D. A., Plotnikoff, M. D., Markert, J.R., Buckley, J.T., 1988. Preliminary evaluation of
canola oil, pork lard and marine lipid singly and in combination as supplemental dietary lipid sources
for juvenile fall chinook salmon (Oncorhynchus tshawytscha). Aquaculture 68, 325-343.
Dosanjh, B. S., Higgs, D. A., Plotnikoff, D., McBride, J. R., Markert, J. R., Buckley, J. T., 1984. Efficacy of
canola oil, pork lard and marine oil singly and in combination as supplemental dietary lipid sources
for juvenile coho salmon (Oncorhynchus kisutch). Aquaculture 36, 333-345.
Fracalossi, D. M., Craig-Schmidt, M. C., Lovell, R. T., 1994. Effect of dietary lipid sources on production of
leukotriene B by head kidney of channel catfish held at different water temperatures. Journal of
Aquatic Animal Health 6, 242-250.
Fracalossi, D. M., Lovell, R. T., 1995. Growth and liver polar fatty acid composition of year-1 channel catfish
fed various lipid sources at two water temperatures. The Progressive Fish-Culturist 57, 107-113.
Fracalossi, D. M., Lovell, R. T., 1994b. Dietary lipid sources influence responses of channel catfish (Ictalurus
punctatus) to challenge with the pathogen Edwardsiella ictaluri. Aquaculture 119, 287-298.
Greene, D. H. S., Selivonchick, D. P., 1990. Effects of dietary vegetable, animal and marine lipids on muscle
lipid and hematology of rainbow trout (Oncorhynchus mykiss). Aquaculture 89, 165-182.
Hardy, R. W., Scott, T. M., Harrell, L. W., 1987. Replacement of herring oil with menhaden oil, soybean oil,
or tallow in the diets of atlantic salmon raised in marine net-pens. Aquaculture 65, 267-277.
Hertrampf, J. W., Piedad-Pascual, F., 2000. Animal fats In: Handbook on ingredients for aquaculture feeds.
London: Kluwer Academic Publishers Pp. 43-57.
Hoffman, L. C., Prinsloo, J. F., 1995. The influence of different dietary lipids in the growth and body
composition of the African sharptooth catfish, Clarias gariepinus (Burchell). South African Journal
of Science 91, 315-320.
Lall, S. P., 2001. Dietary lipids, immune function and pathogenesis of disease in fish. Proceedings of the 37th
Eastern Nutrition Conference. 15 & 16 May 2001, Halifax, Nova Scotia Pp. 150-158.
Li, M. H., Wise, D. J., Johnson, M. R., Robinson, E. H., 1994. Dietary menhaden oil reduced resistance of
channel catfish (Ictalurus punctatus) to Edwardsiella ictaluri. Aquaculture 128, 335-344.
Mugrditchian, D. S., Hardy, R. W., Iwaoka, W. T., 1981. Linseed oil and animal fat as alternative lipid
sources in dry diets for chinook salmon (Oncorhynchus tshawytscha). Aquaculture 25, 161-172.
Murai, T., Akiyama, T., Takeuchi, T., Watanabe, T., Nose, T., 1985. Effects of dietary protein and lipid levels
on performance and carcass composition of fingerling carp. Bulletin of the Japanese Society of the
Scientific Fisheries 51, 605-608.
Naylor, R. L., Goldburg, R. J., Primavera, J. H., Kautsky, N., Beveridge, M. C. M., Clay, J., Folke, C.
Lubchenco, J., Mooney, H., Troell, M., 2000. Effect of aquaculture on world fish supplies. Nature
405, 1017-1024.
Prokop, W. H., 1996. The rendering industry-a commitment to public service. In: The Original Recyclers (ed.
by D.A. Franco and W. Swanson), pp. 17-21. The animal Protein Producers Industry, The Fats &
Proteins Research Foundation, The National Renderers Association, USA.
Pustowska, C., McNiven, M. A., Richardson, G. F., Lall, S. P., 2000. Source of dietary lipid affects sperm
plasma membrane integrity and fertility in rainbow trout Oncorhynchus mykiss (Walbaum) after
cryopreservation. Aquaculture Research 31, 297-305.
Reigh, R. C., Ellis, S. C., 2000. Effects of dietary catfish oil, menhaden oil, and tallow on production
characteristics of pond-raised channel catfish Ictalurus punctatus. Journal of Applied Aquaculture
10, 53-63.
Rudbeck, J., 2002. Market Report 2001: 2001 was a struggle; will 2002 fare better? Render: The National
Magazine of Rendering 31, 10-15, 63.

Dominique P. Bureau, Jennifer Gibson and Adel El-Mowafi 504
Schwarz, F.J., Kirchgessner, M., Steinhart, H., Runge, G., 1988. Influence of different fats with varying
additions of alpha-tocopherol acetate on growth and body composition of carp (Cyprinus carpio L.).
Aquaculture 69, 57-67.
Sheldon, W. M. Jr., Blazer, V. S., 1991. Influence of dietary lipid and temperature on bactericidal activity of
channel catfish macrophages. Journal of Aquatic Animal Health 3, 87-93.
Sibbald, I. R., Slinger, S. J., Ashton, G. C., 1962. Factors affecting the metabolizable energy content of
poultry feeds. 2. Variability in the M.E. values attributed to samples of tallow and undegummed
soybean oil. Poultry Science 40, 303-308.
Sibbald, I. R., 1978. The true metabolizable energy values of mixtures of tallow with either soybean oil or
lard. Poultry Science 57, 473-477.
Stickney, R. R., Andrews, J. W., 1971. Combined effects of dietary lipids and environmental temperature on
growth, metabolism and body composition of channel catfish (Ictalurus punctatus). Nutrition 101,
1703-1710.
Stickney, R. R., McGeachin, R. B., 1984. Growth, food conversion and survival of fingerling Tilapia aurea
fed differing levels of dietary beef tallow. Progressive Fish-Culturist 46, 102-105.
Takeuchi, T., Watanabe, T., Ogino, C., 1978. Use of hydrogenated fish oil and beef tallow as a dietary energy
source for carp and rainbow trout. Bulletin of the Japanese Society of Scientific Fisheries 44, 875-
881.
Watanabe, T., 2002. Strategies for further development of aquatic feeds. Fisheries Science. 68: 242-252.
Watanabe, T., Takeuchi, T., Saito, M., Nishimura, K., 1984. Effect of low protein-high calory or essential
fatty acid deficiency diet on reproduction of rainbow trout. Bulletin of the Japanese Society of
Scientific Fisheries 50, 1207-1215.
Watson, F. S., 1981. Comparison of salmon fish oil, animal fat and canola oil as dietary fat sources for
rainbow trout (Salmo gairdneri Richardson). M.Sc. Thesis, University of Guelph, Guelph, Ontario,
Canada.
Yu, T. C., Sinnhuber, R. O., 1981. Use of beef tallow as an energy source in coho salmon (Oncorhynchus
kisutch) rations. Canadian Journal of Fisheries and Aquatic Sciences 38, 367-370.