Dietary Omega-3 Oil Supplementation To Increase Omega-3 Polyunsaturated Fatty Acids In The Red Tilapia(Oreochromis Hybrid) And Catfish (Clarias Gariepinus)
A study was carried out to determine the essential polyunsaturated fatty acid (PUFA) profiles of the red tilapia (Oreochromis hybrid) and catfish (Clarias gariepinus) and an attempt was made to increase the omega-3 polyunsaturated fatty acids by dietary omega -3 oil supplementation. The fatty aci...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2007
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| Online Access: | http://psasir.upm.edu.my/id/eprint/6407/1/ABSTRACT__FPV_2007_6.pdf http://psasir.upm.edu.my/id/eprint/6407/ |
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| Summary: | A study was carried out to determine the essential polyunsaturated fatty acid (PUFA)
profiles of the red tilapia (Oreochromis hybrid) and catfish (Clarias gariepinus) and
an attempt was made to increase the omega-3 polyunsaturated fatty acids by dietary
omega -3 oil supplementation. The fatty acid profiles of commercially farmed adult
fish were determined using standard extraction, fatty acid methylation and gas liquid
chromatographic procedures and the fatty acid concentration of dried fish tissues was
expressed in absolute amounts (mg/g) as a measure of the actual fatty acid content in
the fish tissues. The levels of total fatty acids, SFA, UFA, monoenes, total n-6, total
n-3, 18:2n-6 and 18:3n-3 were higher in the catfish compared to the red tilapia. The
higher (17-20% of the total fatty acids) n-6 PUFA found in both fish compared to n-3
PUFA (1.0 – 9.5 %) was characteristic for freshwater fish.
The absolute amounts of total n-6 and n-3 PUFA increased as the age of the fish
increased for both species of fish when measured from 10 to 75 days of age although
they decreased when expressed as a percentage of total fatty acids. The absolute amounts of total n-6 PUFA in the red tilapia increased from 10.0 ± 0.6 mg/g at 10
days to 26.6 ± 2.4 mg/g at 75 days of age. The absolute amounts of total n-3 PUFA
in the red tilapia increased from 3.6 ± 0.2 mg/g at 10 days to 9.4 ± 0.3 mg/g at 75
days of age. Similarly, the absolute amounts of total n-6 PUFA in the catfish
increased from 15.1 ±1.0 mg/g at 10 days to 36.5 ± 2.5 mg/g at 75 days of age whilst
the absolute amounts of total n-3 PUFA increased from 8.1 ± 0.2 mg/g at 10 days to
21.8 ± 1.5 mg/g at 75 days of age. The results were suggestive of a combined effect
of accumulation, desaturation and elongation and oxidation of the PUFA in the fish
tissues.
The Δ6 desaturase enzyme activity in the liver microsomes was measured in six of
each species of fish employing radiolabelled linoleic acid [1-14C] and argentation
thin layer chromatography. Desaturase activities were detected in both species but
the activity in the red tilapia (3.55 + 0.2%; 1.19 + 0.1 pmol/min/mg protein) was
higher, although not significant (p>0.05), than the catfish (3.07 ± 0.2%; 1.02 + 0.1
pmol/min/mg protein).
The antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase
(GSH-Px) and the lipid peroxidation value of malonaldehyde (MDA) were measured
in ten of each species of fish. The antioxidant activity was higher in the catfish whilst
the lipid peroxidation value was higher in the red tilapia. The activity of SOD (1.54 ±
0.1 U/g) and GSH-Px (0.37 ± 0.1 U/g) in the red tilapia was lower than the activity
of SOD (2.48 ± 0.1 U/g) and GSH-Px (1.18 ± 0.1 U/g) in the catfish. The MDA
values were 21.39 ± 0.5 nmol/g for the red tilapia compared to 19.15 ± 0.2 nmol/g
for the catfish. The dietary omega-3 oil supplementation trial was carried out for eight weeks where
the fish was reared in glass aquariums in under three dietary treatments, in triplicate.
The treatment diets were the control diet CON (with no oil added), or diets
containing added 10% or 20% flaxseed oil (10% FLAX or 20% FLAX) or added
10% or 20% cod-liver oil (10% COD, 20% COD). The desirable n-3 PUFA were not
increased by the 10% FLAX or 10% COD diets where the total n-3 PUFA
concentrations in the red tilapia were 3.2 + 0.1 mg/g (CON), 2.6 ± 0.2 mg/g (10%
FLAX) and 3.4 ± 0.2 mg/g (10% COD). The n-3 PUFA concentrations in the catfish
were 7.1 ± 0.4 mg/g (CON), 6.4 ± 0.1 mg/g (10% FLAX) and 6.4 ± 0.4 mg/g
(10%COD). However, the n-3 PUFA concentrations were significantly increased
(p<0.05) when fed the 20% FLAX and 20% COD diets. In the red tilapia the n-3
PUFA concentrations were 3.4 ± 0.1 mg/g (CON), 4.7 ± 0.1 mg/g (20% FLAX) and
3.8 ± 0.2 mg/g (20% COD). The n-3 PUFA concentrations in the catfish were 6.5 ±
0.3 mg/g (CON), 8.5 ± 0.6 mg/g (20% FLAX) and 9.0 ± 0.6 mg/g (20% COD).
However high mortality rates up to 60% were encountered when the 20% FLAX and
20% COD diets were used suggesting that the levels of the oils used in these diets
were toxic to the fish. Histological examinations carried out at post-mortem
confirmed the toxicological condition by the occurrence of several histopathological
lesions in the liver, kidney and small intestine.
In conclusion, the essential PUFA profiles of the red tilapia which has a herbivorous
mode of nutrition and the catfish which is more omnivorous, with different
desaturase and oxidative enzyme activities are somewhat different, where the former
represents a better source of desirable essential PUFA to the human consumer. The
concentrations of the desirable essential PUFA in both fishes can be increased by modifying their diets to contain added oils such as flaxseed or cod-liver oil but the
percentage of the added oils have to be between 10-20% of the diet to avoid toxicity
and high mortalities. |
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