518
P. F. Surai and I. I. Kochish
These functions are considered to be responsible for the various health-promoting
properties of carotenoids. However, the physiological requirement for carotenoids in
avian species is not yet established and more work in this field is needed to understand
how carotenoids fulfil any essential nutritional function in poultry.
20.4 Carotenoid Absorption and Bioavailability
Carotenoid absorption and bioavailability have received considerable attention for
the last few years (Nagao 2011; Kotake-Nara and Nagao 2011; Reboul 2013; Perveen
et al. 2015; Cervantes-Paz et al. 2016). However, most of these publications were
mainly concerned with humans. Analyses of data associated with avian species are
presented below. Birds are considered to be good oxycarotenoid absorbers although
some birds, for example, the flamingo, preferentially absorb carotenes (Hudon 1994).
The efficiency of carotenoid assimilation from the feed depends on many factors
and absorption in the intestine is a major determinant of this process. In general,
carotenoid absorption can be divided into four stages: digestion of the food matrix,
formation of lipid-mixed micelles, uptake of carotenoids into the intestinal mucosal
cells and delivery to the plasma via the lymph system (Williams et al. 1998). Since
the lymphatic system of the bird is not developed, carotenoids are probably delivered
directly to the liver and other tissues by portomicrons, i.e. the lipid-rich lipoproteins
released from the intestinal cells into the portal vein. Carotenoid ester hydrolysis
by pancreatic esterases is an important step in their absorption. For example, it has
been shown that the dietary lutein diester was hydrolysed mainly to lutein, which
was absorbed through the intestinal wall into the blood stream and, in the serum,
about 96% of the total lutein occurred as the free alcohol and the remainder was in
the form of the monoester (Tyczkowski and Hamilton 1986a, b). As a result, hens
fed lutein diester accumulated lutein in their yolks (Philip et al. 1976). When hens
were fed zeaxanthin diester, the egg yolk contained only free zeaxanthin (Kuhn and
Brockman 1932). It is possible to improve egg yolk pigmentation by prior saponification of marigold meal xanthophyll (Coon and Couch 1976). Furthermore, in
broilers free lutein is absorbed almost two-fold faster compared to lutein diester
(Tyczkowski and Hamilton 1986a, b). It is interesting to note that, in the chicken,
the contents of the jejunum and large intestine contained a mixture of lutein diester,
lutein monoester and lutein, but in the serum lutein was found mainly (90%) in the
non-esterified form (Tyczkowski and Hamilton 1986a, b). Similarly, in the chicken
liver lutein monoester and diester comprise about 20 and 2% of total lutein, respectively (Hamilton 1992). In contrast, in the toe web about half of the total lutein
occurred as the diester and the remainder occurred as about equal amounts of free
lutein and lutein monoester (Tyczkowski and Hamilton 1986a, b). Using a chicken
model and β-apo-8
I -caroitenoic acid ethyl ester (Apo-EE) as a reference, it was
shown that the relative biological availability of xanthophyll from various sources
to be (%): Apo-EE 100, corn gluten meal 64.2 (47.7–89.1), dehydrated alfalfa 45.9
(34.6–65.4), marigold meal 29.1, marigold extracts 62.9 and coastal Bermugrass
P. F. Surai and I. I. Kochish
These functions are considered to be responsible for the various health-promoting
properties of carotenoids. However, the physiological requirement for carotenoids in
avian species is not yet established and more work in this field is needed to understand
how carotenoids fulfil any essential nutritional function in poultry.
20.4 Carotenoid Absorption and Bioavailability
Carotenoid absorption and bioavailability have received considerable attention for
the last few years (Nagao 2011; Kotake-Nara and Nagao 2011; Reboul 2013; Perveen
et al. 2015; Cervantes-Paz et al. 2016). However, most of these publications were
mainly concerned with humans. Analyses of data associated with avian species are
presented below. Birds are considered to be good oxycarotenoid absorbers although
some birds, for example, the flamingo, preferentially absorb carotenes (Hudon 1994).
The efficiency of carotenoid assimilation from the feed depends on many factors
and absorption in the intestine is a major determinant of this process. In general,
carotenoid absorption can be divided into four stages: digestion of the food matrix,
formation of lipid-mixed micelles, uptake of carotenoids into the intestinal mucosal
cells and delivery to the plasma via the lymph system (Williams et al. 1998). Since
the lymphatic system of the bird is not developed, carotenoids are probably delivered
directly to the liver and other tissues by portomicrons, i.e. the lipid-rich lipoproteins
released from the intestinal cells into the portal vein. Carotenoid ester hydrolysis
by pancreatic esterases is an important step in their absorption. For example, it has
been shown that the dietary lutein diester was hydrolysed mainly to lutein, which
was absorbed through the intestinal wall into the blood stream and, in the serum,
about 96% of the total lutein occurred as the free alcohol and the remainder was in
the form of the monoester (Tyczkowski and Hamilton 1986a, b). As a result, hens
fed lutein diester accumulated lutein in their yolks (Philip et al. 1976). When hens
were fed zeaxanthin diester, the egg yolk contained only free zeaxanthin (Kuhn and
Brockman 1932). It is possible to improve egg yolk pigmentation by prior saponification of marigold meal xanthophyll (Coon and Couch 1976). Furthermore, in
broilers free lutein is absorbed almost two-fold faster compared to lutein diester
(Tyczkowski and Hamilton 1986a, b). It is interesting to note that, in the chicken,
the contents of the jejunum and large intestine contained a mixture of lutein diester,
lutein monoester and lutein, but in the serum lutein was found mainly (90%) in the
non-esterified form (Tyczkowski and Hamilton 1986a, b). Similarly, in the chicken
liver lutein monoester and diester comprise about 20 and 2% of total lutein, respectively (Hamilton 1992). In contrast, in the toe web about half of the total lutein
occurred as the diester and the remainder occurred as about equal amounts of free
lutein and lutein monoester (Tyczkowski and Hamilton 1986a, b). Using a chicken
model and β-apo-8
I -caroitenoic acid ethyl ester (Apo-EE) as a reference, it was
shown that the relative biological availability of xanthophyll from various sources
to be (%): Apo-EE 100, corn gluten meal 64.2 (47.7–89.1), dehydrated alfalfa 45.9
(34.6–65.4), marigold meal 29.1, marigold extracts 62.9 and coastal Bermugrass