20 Carotenoids in Aviculture
521
with the membranes of intestinal epithelial cells and so the carotenoids within the
lipid micelles come in contact with the intestine epithelial cell membranes and their
transport to the plasma membrane and/or cytosol of the cell takes place in concert
with the transport of fatty acids, monoglycerides and other lipids (Erdman et al.
1993). It is known that the passage of lipids through the brush border membrane
is passive, and absorption rates depend on the fatty acid chain length and degree
of saturation (Krogdahl 1985). It is becoming increasingly evident that the micelles
formed from dietary lipids serve as a delivery system for carotenoids to reach the
absorptive surface of the gut. The micelles facilitate fat absorption by providing a
high concentration of lipids in the unstirred water layer adjacent to the mucosal cells
and disruption of the micelles is necessary before absorption takes place (Krogdahl
1985). The feed matrix is thought to be an important determinant for the absorption of
carotenoids and therefore carotenoid absorption varies substantially among different
foods and their bioavailabilities can be improved by disruption of the food matrix
(van het Hof et al. 1999). The amount and type of feed determine bile secretion,
while bile salts and fat determine micelle formation (van Vliet 1996). The pH in
the intestinal lumen may also affect absorption via an effect on the surface charges
of both the micellar particles and the luminal cell membrane, with less diffusion
resistance at lower pH values (Hollander 1981).
The efficiency of dispersion of carotenoids is known to be affected by the presence or absence of other components in the diet, as well as by the general nutritional status of the animal. It has been summarised that 9 major factors determine
carotenoid bioavailability: species of carotenoids, molecular linkage, amount of
carotenoids consumed in a meal, matrix in which the carotenoid is incorporated,
effectors of absorption and bioconversion, nutrient status of the host, genetic factors,
host-related factors and nutrient interactions (Castenmiller and West 1998). In the
chicken, absorption and accumulation of major carotenoids is comparatively low.
In broilers, 94% of astaxanthin and about 83% of zeaxanthin supplied by the diet
were excreted and only 0.4% of the astaxanthin and 1.7% of the zeaxanthin were
deposited in the skin (Hencken 1992). Cryptoxanthin in particular is very poorly
absorbed in birds (Quackenbush 1970; Tyczkowski and Hamilton 1986b). In laying
hens, carotenoid deposition in egg yolk is also comparatively low with canthaxanthin being deposited at 30–45% efficiency, zeaxanthin 25% and astaxanthin 14%
(Hencken 1992) and carotenoid excretion was about 70% for astaxanthin and zeaxanthin and 45–50% for canthaxanthin. Earlier it had been shown that 43% (Nakaue
et al. 1966) or 56% (Marusich and Bauernfeind 1981) of the ingested zeaxanthin
was deposited in egg yolks. In the same experiment, the levels of deposition of cryptoxanthin, lutein and violaxanthin were 21, 9 and 0%, respectively (Nakaue et al.
1966). Astaxanthin transfer from the yeast Phaffia rhodozyma, added to the diet of the
quail, to the egg yolk comprised only 4% of the ingested carotenoid; from marigold
extract carotenoid transfer to the egg yolk was even lower (3%) (Johnson et al. 1980).
About 16% of capsanthin was transferred from the diet (as a saponified oleoresin)
into the egg yolk (Hamilton et al. 1990) but when crystalline capsanthin was used
only 6.2% of this carotenoid was transferred to the egg yolk (Marusich et al. 1960).
In accordance with other observations the efficiency of the deposition of capsanthin
521
with the membranes of intestinal epithelial cells and so the carotenoids within the
lipid micelles come in contact with the intestine epithelial cell membranes and their
transport to the plasma membrane and/or cytosol of the cell takes place in concert
with the transport of fatty acids, monoglycerides and other lipids (Erdman et al.
1993). It is known that the passage of lipids through the brush border membrane
is passive, and absorption rates depend on the fatty acid chain length and degree
of saturation (Krogdahl 1985). It is becoming increasingly evident that the micelles
formed from dietary lipids serve as a delivery system for carotenoids to reach the
absorptive surface of the gut. The micelles facilitate fat absorption by providing a
high concentration of lipids in the unstirred water layer adjacent to the mucosal cells
and disruption of the micelles is necessary before absorption takes place (Krogdahl
1985). The feed matrix is thought to be an important determinant for the absorption of
carotenoids and therefore carotenoid absorption varies substantially among different
foods and their bioavailabilities can be improved by disruption of the food matrix
(van het Hof et al. 1999). The amount and type of feed determine bile secretion,
while bile salts and fat determine micelle formation (van Vliet 1996). The pH in
the intestinal lumen may also affect absorption via an effect on the surface charges
of both the micellar particles and the luminal cell membrane, with less diffusion
resistance at lower pH values (Hollander 1981).
The efficiency of dispersion of carotenoids is known to be affected by the presence or absence of other components in the diet, as well as by the general nutritional status of the animal. It has been summarised that 9 major factors determine
carotenoid bioavailability: species of carotenoids, molecular linkage, amount of
carotenoids consumed in a meal, matrix in which the carotenoid is incorporated,
effectors of absorption and bioconversion, nutrient status of the host, genetic factors,
host-related factors and nutrient interactions (Castenmiller and West 1998). In the
chicken, absorption and accumulation of major carotenoids is comparatively low.
In broilers, 94% of astaxanthin and about 83% of zeaxanthin supplied by the diet
were excreted and only 0.4% of the astaxanthin and 1.7% of the zeaxanthin were
deposited in the skin (Hencken 1992). Cryptoxanthin in particular is very poorly
absorbed in birds (Quackenbush 1970; Tyczkowski and Hamilton 1986b). In laying
hens, carotenoid deposition in egg yolk is also comparatively low with canthaxanthin being deposited at 30–45% efficiency, zeaxanthin 25% and astaxanthin 14%
(Hencken 1992) and carotenoid excretion was about 70% for astaxanthin and zeaxanthin and 45–50% for canthaxanthin. Earlier it had been shown that 43% (Nakaue
et al. 1966) or 56% (Marusich and Bauernfeind 1981) of the ingested zeaxanthin
was deposited in egg yolks. In the same experiment, the levels of deposition of cryptoxanthin, lutein and violaxanthin were 21, 9 and 0%, respectively (Nakaue et al.
1966). Astaxanthin transfer from the yeast Phaffia rhodozyma, added to the diet of the
quail, to the egg yolk comprised only 4% of the ingested carotenoid; from marigold
extract carotenoid transfer to the egg yolk was even lower (3%) (Johnson et al. 1980).
About 16% of capsanthin was transferred from the diet (as a saponified oleoresin)
into the egg yolk (Hamilton et al. 1990) but when crystalline capsanthin was used
only 6.2% of this carotenoid was transferred to the egg yolk (Marusich et al. 1960).
In accordance with other observations the efficiency of the deposition of capsanthin