Safegaurding Your Pets Against Air Pollution Vol XII , Issue No 12 , Dec 2019 | Page 42

Pet Nutrition
carriers in petfood, the average
amounts per kg dry matter are
as follows: 0.7 g ß-carotene in
carrots (1-3), 2.0 g lycopene in
tomatoes (4-8), 11.5 g lutein in
marigold fl owers (9, 10), 20.0 g
astaxanthin in the microalaga
Haematococcus pluvialis (11)
and 0.1 g in krill meal (12).
At an inclusion level of 1%, the
plant carriers could bring 7 to 115
mg carotenoid per kg dry petfood.
By comparison, 50% corn as base
ingredient delivers on average 5 mg
lutein and 3 mg zeaxanthin per kg dry
food (13-15).
METABOLIC FRAMEWORK
Single, oral doses of pure ß-carotene,
astaxanthin or lycopene dose-
dependently raised the corresponding
plasma carotenoid levels in dogs and
cats, with peaking times of about 6
or more than 12 hours (16-20). After
daily intake for more than a week,
the carotenoids in plasma, including
lutein (21), approached a dose-
dependent, steady state concentration
(16-19,
22-28).
Simultaneously,
increased carotenoid levels in blood
cells and tissues were observed (16-19,
25, 26).
Enterocytes likely absorb the lipophilic
carotenoids by passive diffusion,
as mixed-micelle components, or
by a carrier-mediated process, both
routes leading to secretion with
chylomicrons. After hepatic uptake
of chylomicrons, their carotenoids
may re-enter the circulation with
very-low density lipoproteins for
delivery in extrahepatic tissues. The
body can dispose of carotenoids by
mitochondrial degradation, urinary
and biliary excretion (29-32), thereby
enabling a new steady state after
changed intake.
CAROTENOIDS AND IMMUNITY
In dogs and cats fed purifi ed
carotenoids,
immune
status
was
assessed
by
measuring
immunoglobulin G (IgG) concentration
in blood plasma and mitogen-
induced proliferation in isolated
lymphocytes. Carotenoid dosing was
equivalent to levels of 0, 10 and up to
300 mg/kg dry food. On the whole,
the carotenoids had no convincing,
immunostimulatory
effect.
The
immune indicators were unaffected,
not enhanced by the lowest dose, or
displayed a dose-unrelated response.
Oral administration of ß-carotene
did not infl uence plasma IgG in
cats (33) and produced an arch-
shaped dose-response in dogs (22).
ß-Carotene did not affect group-
mean lymphocyte proliferation (22)
or had an inconsistent dose
response in dogs (34), whereas
the dose dependency was arch-
like in cats (33). Research data
on immune effects of dietary
lycopene in dogs and cats are
unavailable.
Lutein
enhanced
canine
lymphocyte proliferation in a
dose-dependent fashion (27), but
(extremely) high intake was effectless
in another dog study (35). In cats,
the feeding of diets with increasing
lutein concentrations stimulated
lymphocyte proliferation, but the
dose-effect relationship was erratic
(21). In dogs and cats, ingestion
of purifi ed astaxanthin increased
both plasma IgG and lymphocyte
proliferation, but with atypical dose
responses (23, 24).
ASTAXANTHIN AS ANTIOXIDANT
With regard to the antioxidative
potential of carotenoids in petfood,
there only are published data on
astaxanthin effects in dogs. Plasma
concentration
of
8-hydroxy-2’-
deoxyguanosine,
the
oxidized
derivative of the purine nucleoside,
was determined as biomarker of
oxidative DNA damage. Supplying dry
food with 50 mg astaxanthin/kg dry
food lowered the group-mean level
of the indicator in one study (28), but
raised it in another one (24).
* List of references is available on request
from the author ([e-mail])