FATTY ACID COMPOSITION OF RESIDUAL YOLK AND LIVER FROM
BROILER CHICKS HATCHING FROM OMEGA-3 ENRICHED EGGS
Koppenol Astrid12, Delezie Evelyne1, Wang Yufeng2, Willems Els2, Everaert Nadia2, Buyse
Johan2
1
Animal Sciences Unit, ILVO, Scheldeweg 68, 9090 Melle, Belgium
Department of Biosystems, Division of Livestock-Nutrition-Quality, KU Leuven, Kasteelpark
Arenberg 30 - box 2456, 3001 Leuven, Belgium
2
ABSTRACT
Fatty acids in the diets of broiler breeder hens, such as arachidonic acid (AA, 20:4 n-6),
eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3), can be built
into the yolk and therefore be available to the progeny for their development (Noble et al., 1990).
They are absorbed from the residual yolk and are built in the liver to serve as a reservoir for
eicosanoid production, neural development,… (Speake, 1998). From 6 weeks on 480 Ross-308
broiler breeder hens were fed 4 different diets (control, EPA=DHA, DHA>EPA or EPA>DHA) .
At 28 weeks of age, 60 fresh yolk were weight and 20 fresh yolks per treatment were pooled by 4
for FA analysis (n=5), the remaining eggs were incubated. After hatch, 12 livers per treatment
were sampled at day 1, 14 and 30. At 38 weeks, eggs were incubated and 25 residual yolks were
sampled per treatment, weighed and pooled by 5 for FA analysis (n=5). n-3 enriched eggs had a
significantly lower fresh yolk and residual yolk weight. Eggs from EPA enriched hens had
significantly more EPA in their fresh yolk and residual yolk, while the DHA content was
increased in fresh and residual yolk in the eggs of all n-3 enriched hens. At d1 post hatch both
the hepatic EPA and DHA concentration was significantly higher for offspring from enriched
hens. Hepatic DHA content decreased with post hatch age, highlighting the role of DHA early in
the development.
KEYWORDS: EPA, DHA, nutrition, broiler breeders
INTRODUCTION
Dietary fatty acids (=FA’s) provided to the hens can be built into the yolk and therefore
be available to the progeny early in their development. During the 21 days of incubation, over
80% of yolk lipids is absorbed by the developing chick embryo, serving as a source of energy and
essential FA’s (Noble et al., 1990). Moreover they contribute to embryonic structural
phospholipids through provision of long chain (>20C) poly unsaturated fatty acid’s (PUFA’s),
such as arachidonic acid (AA, 20:4 n-6), eicosapentaenoic acid (EPA, 20:5 n-3) and
docosahexaenoic acid (DHA, 22:6 n-3). Previous studies reported that upon incubation of a
fertile egg, the tissue fatty acid composition of the embryo and the hatched chick reflected the
egg yolk fatty acid profile (Cherian et al., 1991). Similarly, tissues (e.g. cardiac, hepatic, immune
and brain) of growing chicks hatched from n-3 fatty acid-rich eggs retained significantly higher
levels of these fatty acids (Cherian et al., 2007). In this study the fresh yolk, residual yolk and
liver FA composition is studied.
MATERIALS AND METHODS
From 6 weeks of age 480 Ross-308 broiler breeder hens were divided over 16 pens.
They received 4 different dietary treatments (n=120), a control diet rich in n-6 fatty acid or an n-3
enriched diet in which EPA=DHA, DHA>EPA or EPA>DHA. The EPA/DHA ratio’s were 0.8,
0.2 and 2.1 respectively. Eggs were fertilized from 21 weeks onwards and collected at 28 weeks
of age during 8 days for incubation. Hatched chicks were sexed and 720 male chicks were placed
in 24 pens of 30 chicks each, resulting in 6 replicates (n=180) per pre-hatch treatment. Offspring
was fed a commercial starter, grower and finisher diet and kept until slaughter age. At d1, d14
and d30, 2 chicks per pen were culled for liver sampling (n=12/treatment). Livers from 1 day old
chickens were pooled by 6, livers from 14 day old chickens by 2 for FA analysis by
gaschromatography. From another 60 eggs per treatment, the fresh yolk was weighed at 28
weeks of age. Twenty yolks per treatment were pooled by 5 and collected for FA analysis (n=4).
At 38 weeks of age additional eggs were incubated and from 25 chicks per treatment the residual
yolk was weighed and pooled by 5 (n=5) for FA composition analysis. Treatment effects were
analyzed by 2-way ANOVA, using Statistica, version 10 (StatSoft Inc., Tulsa, OK, USA).
RESULTS AND DISCUSSION
60
Figure 1: Egg weight (EW) (n=60), absolute fresh yolk weight
(YW) (n=60) and residual yolk weight (RYW) (n=25) for 4
different treatments (control group, n-3 enriched group with
EPA=DHA, DHA rich group, EPA rich group). a and b refer
to significant differences (p<0.05).
EW
YW
RYW
50
a
b
ab
ab
40
Weight (g)
Egg weight was lower for all n-3 enriched
30
groups, resulting in significantly lower absolute yolk
weight and absolute residual yolk weight for DHA and
20
EPA enriched eggs (fig 1), while no differences were
found for proportional yolk (as a percentage of total
a
b
b
b
egg weight) and proportional residual yolk weight
10
(data not shown). Cherian et al. (2008) also found a
a
a
b
b
significant decrease in egg weight for high n-3 eggs,
0
CON
EPA=DHA
DHA
EPA
when compared with low n-3 eggs. Yolk and residual
yolk of eggs from hens who received a control diet,
rich in AA, contained significantly more AA, compared to the yolk coming from DHA and EPA
enriched hens (Fig. 2). Since all progeny was fed a commercial diet, rich in AA, no differences
were found for AA concentration in the liver of the offspring at d1 and d14 from n-3 enriched
hens compared to control hens. However at d30 chicks coming from DHA enriched hens
accumulated more AA in their liver. Eggs laid by hens receiving EPA in their diet (both the
EPA=DHA, and the EPA enriched hens) had an increased EPA concentration in the yolk and
residual yolk. At day 1 posthatch, the liver from all n-3 enriched chicks had an increased EPA
concentration compared to the liver of control offspring. At day 14, offspring from DHA
enriched hens, had significantly more EPA in their liver than offspring from EPA enriched hens.
Fresh yolk, residual yolk and liver at d1 from all n-3 enriched groups contained more DHA
compared to the control group. At day 14, no differences were found, while on day 30 posthatch
the DHA content in the
12
CON
EPA=DHA
DHA
EPA
concentration AA (%)
10
a
8
ab
b
6
4
b
Figure 2: Arachidonic acid concentration (AA),
eicosapentaenoic
acid
(EPA)
and
docosahexaenoic acid (DHA), of fresh yolk (n=5),
residual yolk (RY) (n=5) and liver (L) at day 1
(n=2), 14 (n=6) and 30 (n=12) posthatch for eggs
incubated for 4 maternal dietary treatment. a
and b refer to significant differences (p<0.05).
a
ab b b
a
ab
liver was significantly higher for chicks coming
0
from DHA enriched hens compared to control
Yolk
RY
L d1
L d14
L d30
chicks. These results fit the findings of Pappas et
al. (2006), who found higher concentrations of n-3
1,0
a
CON
FA and lower concentrations of n-6 FA in the lipid
ab
EPA=DHA
ab
DHA
a
0,8
content of the liver of chicks from breeders fed fish
EPA
a
b
a
oil compared with those from hens fed soya oil.
0,6
This difference was maintained for up to 14 d
posthatch. The FA concentration in the liver at
a
0,4
hatch was several times higher than that measured
b
a
a
in the hatching egg yolk, even for the control group.
0,2
b
b
This suggests a biomagnification of specific FA’s
c
by the yolk sac membrane (Speake et al., 1998).
b
c
0,0
Yolk
RY
L d1
L d14
L d30
Only EPA enriched hens produced eggs with a
higher concentration of EPA in both the fresh yolk
7
a a
and residual yolk, while the DHA concentration in
CON
EPA=DHA
6
the fresh and residual yolk increased for all n-3
DHA
EPA
a
enriched hens. This can be explained by the fact
5
that DHA is formed out of EPA, so part of the EPA
a
ab
4
a
from the diet of the hens will be transformed by
3
elongation and desaturation enzymes into DHA.
Moreover, hepatic DHA content decreased with
a
b
2
a a a
b ab ab
posthatch age, highlighting its role in the early
b
1
development and thus the importance of maternal
b
0
transition. The effects of maternal nutrition on FA
Yolk
RY
L d1
L d14
L d30
composition of the liver in the growing chick in this
study persisted for at least up to 14 d posthatch. Previous studies have indicated similar
persistent effects of maternal nutrition on the progeny (Pappas et al., 2006).
b b
concentration DHA (%)
concentration EPA (%)
2
CONCLUSION
Dietary enrichement of n-3 FA’s affects egg, fresh yolk and residual yolk weight. Only
EPA enriched hens produced eggs with a higher concentration of EPA in both the fresh yolk and
residual yolk, while the DHA concentration in the fresh and residual yolk increased for all n-3
enriched hens. Moreover hepatic DHA content decreases with posthatch age, highlighting its role
in the early development. Supplementation of the maternal diet with PUFA’s could increase the
concentration of EPA and DHA in the tissues of the chick during the first crucial days posthatch.
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