Enrichment of Milk with Conjugated Linoleic Acid by Supplementing Diets with Fish and Sunflower Oil
S.A.H. Abo El-Nor
Mostafa S.A. Khattab
There is an increase interesting in enrichment of milk with Conjugated Linoleic Acid (CLA) due to its anti-oxidative and anti-carcinogenic properties. The objective of this study was to investigate the effect of supplementing diets fed to lactating goats with sunflower, fish oil and its blend. Eight lactating Nubian goats were fed a base diet (T1), diet supplemented with 2% sunflower oil (on dry matter (DM) basis) (T2), diet supplemented with 2% fish oil (T3) and diet supplemented with 2% sunflower and fish oil (T4) for 84 day. Milk composition milk fat, protein (%) decreased in T2, T3 and T4 compared with control (T1) while there was no significant differences between treatments in milk lactose content. CLA content in milk fat was higher in response to fish oil or sunflower and fish oil blend compared with control (T1). The results indicated that supplementing diets fed to lactating goats with sunflower, fish oil increased CLA contents in the milk 2-4 times than control.
Received: September 03, 2012;
Accepted: December 10, 2012;
Published: January 23, 2013
Over the last years, Conjugated Linoleic Acids (CLA) have been intensively
studied for their activity and its benefits. As a reason of the beneficial effects,
the most two CLA isomers, 9, 11-cis, trans and 10, 12 -trans, cis CLA, have
been highly studied for its biological effects and activity. Conjugated Linoleic
Acid (CLA) is a mixture of seventeen positional and geometric isomers of linoleic
acid with conjugated double bonds located at positions 11, 13-, 10,12-, 9,11-,
8,10- or 7,9- on the carbon chain (Mir et al., 1999).
Butyrivibrio fibrisolvens bacteria are the producer of the CLA isomers
in the rumen (Mir et al., 2000) the CLA isomers
could be intermediary compound in the successive bio-hydrogenation of linoleic
acid to stearic acid. The cis, trans/trans, cis-8,10-, - 9,11-, -10, 12- and
-11, 13- isomers accounts for the major ones, however, the most abundant CLA
isomer is cis-9, trans-11-octadecadienoic acid.
CLA appears to have anti-oxidative and anti-carcinogenic properties (Mir
et al., 1999, 2000). In addition, CLA has
been shown to stimulate immune response and protect against arteriosclerosis
(Cook et al., 1993; Lee et
al., 1994). Many studies have been carried out to investigate the impact
of addition of different sources of oils such as fish oil, sunflower oil, olive
oil and soybean oil in lactating animals diets in a try to increase Conjugated
Linoleic Acid (CLA) concentration in milk.
The current study aimed to compare two sources of oil (fish, sunflower oil)
on the productive performance of lactating Nubian goat and its effect on the
CLA concentration in the milk.
MATERIALS AND METHODS
The present study was performed at the Agricultural Experimental Station and
Dairy Science Department, National Research Centre, Dokki, Giza, Egypt.
Experimental animals: Eight lactating Nubian goats aged 3 years were
used in the present study. Live body weight ranged between 35 and 40 kg. Animals
were assigned randomly into four groups (two animals each group) using 4x4 Latin
square design. The experimental period was extended for 84 days and consisted
of four periods (21 days each).
Experimental rations: The intended ratio of concentrate to roughage
was 62:38 on Dry Matter (DM) basis. The goats were individually fed according
to (NRC, 1985). All supplements were first calculated
on DM basis then mixed with the concentrate feed mixture (Table
1). Concentrates were offered twice daily during milking times at 7:00 a.m.
and 7:00 p.m. Egyptian clover was offered at 11:00 am and overnight. Fresh water
was available to the animals all time.
The experimental diets were as follow:
||Control diet was 62% concentrate feed mixture, 38% Egyptian
clover on DM basis [T1]
||Control diet+2% sunflower oil [T2]
||Control diet+0.5% fish oil [T3]
||Control diet+1.5% sunflower oil+0.5% fish oil [T4]
Milk sampling: Animals were milked handily twice daily at 7:00 a.m.
and 7:00 p.m. Milk yield was recorded, samples of milk were collected from each
animal at morning and evening during the last three days of each experimental
period. Composite milk samples (relative to the quantity of milk produced) were
taken from the two milking to determine the components of milk.
Feed and feces samples analysis: The dry matter contents of feed and faeces
were determined by oven-drying for 4 h at 105°C according to AOAC
(1984) method No. 930.15. Ash analysis was conducted at 550°C for 4
h based on the AOAC (1984 method No. 942.05. Nitrogen was measured using a mixed
catalyst Kjeldahl method (AOAC, 1984); method No. 988.05.
The crude protein content was calculated by multiplying nitrogen by 6.25. Ether
extract was determined by the Soxhlet method with petroleum ether as a solvent
following AOAC (1984) method No. 963.15. The Total Mixed
Ration (TMR) samples were also analyzed for Acid Detergent Fiber (ADF) (method
973.18c; AOAC (1984) and Natural Detergent Fiber (NDF) (Van
Soest et al., 1991) using α-amylase (A3306; Sigma Chemical Co.,
St. Louis, MO) and sodium sulfite corrected for ash concentration adapted for
an Ankom 200 fiber analyzer (Ankom Technology, Fairport, NY).
Milk samples analysis: Milk samples were analyzed for Total Solids (TS),
Solids Not Fat (SNF), Total Protein (TP), fat and lactose using infrared spectroscopy
(Bentley 150, Infrared Milk Analyzer, Bentley Instruments, USA).
|| Chemical composition of concentrate experimental ration
Milk Fatty Acids Methyl Esters (FAME) were prepared by base-catalyzed methanolysis
of the glycerides (KOH in methanol) according to International Standard (ISO-IDF,
2002). FAME were separated using a Cp-Sil 88 fused-silica capillary column
(100x0.25 mm i.d.x0.2 μm film thickness, Chrompack, Middelburg, Netherlands)
on a Perkin-Elmer chromatograph (model 8420, Beaconsfield) equipped with a flame
ionization detector. The column was held at 100°C for 1 min after injection,
temperature-programmed at 7°C min-1 to 170°C, held there
for 55 min, then temperature-programmed at 10°C min-1 to 230°C
and held there for 33 min. Helium was the carrier gas with a column inlet pressure
set at 30 psig and a split ratio of 1:20. The injection volume was 0.2 μL.
Total run time was of 105 min.
Statistical analysis: Data were statistically analyzed using the GLM
procedures of SAS (2004) according to procedures outlined
by Snedecor and Cochran (1982) significant level was 0.05.
RESULTS AND DISCUSSION
Milk yield and composition: The effects of supplementation of ration
with oils on milk yield and milk composition are shown in Table
2. The differences between T2, T3, T4 in either milk yield or 4% fat corrected
milk were not significant; while were significantly differ with control (T1);
the highest value of daily milk yield (1386 g day-1) was obtained
in goats fed on control diet while the lowest value was recorded for T3 (1113
g day-1). Milk fat percentage was decreased for T2, T3 and T4 compared
to T1; differences between groups were significant (p<0.05). The values of
milk fat % were 4.8, 4.5, 4.2 and 3.6 for T1, T2 and T4, respectively.
The results of the present study are in agreement with those reported by Dhiman
et al. (1995), Donovan et al. (2000)
and Abu-Ghazaleh et al. (2003). The addition
of polyunsaturated oils in free form tends to depress milk fat percentage (Selner
and Schultz, 1980).
|| Effect of experimental ration on milk yield and milk composition
|Different superscripts in the same row mean significant difference
at p≤0.05 level
||Effect of dietary supplementation with sunflower oil, fish
oil and their blend on the conjugated linoleic acid (CLA) content in milk
|MCF: Medium chain fatty acids, LCF: Long chain fatty acids,
Different superscripts in the same row mean significant difference at p≤0.05
These results may be due to the effect of supplementing rations with oils which
may reduce the digestibility coefficients of nutrients and the increase of intakes
passage from the rumen.
From the current results it could be noted that total solids, fat, protein
contents were decreased in groups that fed diets supplemented with oil (T2,
T3 and T4) compared with control diet (T1).
Milk fatty acids and CLA contents: Effect of dietary supplementation
with sunflower oil, fish oil and their blend on the Conjugated Linoleic Acid
(CLA) content in milk are shown in Table 3. The contents of
myristic (C14:0) and palmitic (C16:0) acids were significantly
(p<0.05) decreased by supplementation with sunflower oil, fish oil and their
blend. While, C15:0 were significantly higher in T3 compared with
other treatments. Milk from goats fed the T2, T3 and T4 diets had lower (p<0.05)
concentration of medium-chain fatty acids (C14:0-C16:0) and a greater (p<0.05)
concentration of long-chain fatty acids compared with the T1 diet (Table
3). Feeding polyunsaturated fat is typically associated with a decrease
in the de novo synthesis of short and medium-chain fatty acids (Casper
et al., 1988; Abu-Ghazaleh et al., 2002),
with the greatest decrease when a high linoleic acid source was fed (Casper
et al., 1988; Kelly et al., 1998;
Abu-Ghazaleh et al., 2003). The decrease in medium-chain
fatty acids may represent an improvement in the profile of milk fat fatty acids
as these fatty acids have been reported to constitute the hypercholesterolemic
portion of milk fat (Ney, 1991). Stearic acid (C18:0)
was higher when supplemented with sunflower oil, difference between experimental
groups are significant at p≤0.05. Oleic acid (C18:1) was significantly
(p≤0.05) decreased and was lower for T2, T3 and T4 diets. Goats fed diet
supplemented with oil (T2, T3 and T4) produced milk fat CLA 2-4 times higher
than that in control; differences among groups are significant at p≤0.05.
The two source of oils used in the study were chosen due to their richness with
polyunsaturated fatty acids specially in Linoleic acid C18:2 (sunflower
oil) and Oleic acid C18:1 (fish oil), (Griinari
et al., 2000; Piperova et al., 2002).
The linoleic acid C18:2 content in fish oil was 589.9 mg g-1
of fat which is lower than that in sunflower oil (751.9 mg g-1).
But CLA content in milk fat was higher in response to fish oil or sunflower
and fish oil blend supplement compared with control (T1) (Table
3). this result may be due to an interaction between the high content of
oleic acid C18:1 in fish oil and richness of sunflower oil with linoleic
acid. Milk fat contains vary in levels of CLA in milk among herds (Kelly
and Bauman, 1996). The substantial variation in content of CLA in milk fat
between herds suggests that diet has a major influence. Previous study has suggested
that the bio-hydrogenation sequence of linoleic acid can lead to an increase
in CLA levels in milk fat (McGuire et al., 1996).
The results of the present study indicate that other fatty acids might contribute
to CLA production.
Results of the current study showed that feeding lactating goats sunflower
oil, fish oil or blend of them decreased milk production and increased the content
of milk cis-9, trans-11 CLA. The high increase in milk cis-9, trans-11 CLA occurred
within fish oil and blend of fish oil plus sunflower oil supplements to the
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