Biomedical Engineering Reference
In-Depth Information
Table 3
Antioxidants present in body tissues
Enzymatic
Nutrients involved
Nonenzymatic
Nutrients involved
Superoxide dismutase (cytosol)
Copper and zinc
Ascorbic acid
Vitamin C
Superoxide dismutase (mitochondria)
Manganese
Beta carotene (membranes)
Beta carotene
Catalase (cytosol)
Iron
Ceruloplasmin
Copper
Glutathione peroxidase
Selenium
Uric acid
Glutathione reductase
Bilirubin
Melatonin
Iso fl avone
Methionine
a -Tocopherol
Vitamin E
Source: Markesbery et al. (
2001
) , Weiss (
2009
)
Table 4
Suggested feeding levels of vitamin E and some
minerals in total diet
Vitamin E
1,000 IU/day for dry cows
1,500 IU for dry buffaloes
500 IU/day for lactating cows
Selenium 0.3 ppm
Copper 20 ppm
Zinc 60-80 ppm
Source: Modified from Scaletti et al. (
1999
)
period may correct the infertility due to heat
stress through decreased cortisol secretion and
oxidative stress, resulting in enhanced pregnancy
rates. Moreover, strong positive correlations
between several antioxidant enzymes (e.g. gluta-
thione peroxidase) and vascular adhesion mole-
cules suggest a protective response of antioxidants
to an enhanced proinflammatory state in transi-
tion dairy cows (Aitken et al.
2009
) . Antioxidants
then could contribute to enhance mechanisms
against oxidative stress with various immunity,
reproduction and health benefits. Heat stress is
associated with reduced activity by antioxidants
in the blood plasma. Vitamin E (a -tocopherol), a
strong reducing agent that can give electrons to
lipids undergoing peroxidation, is a major anti-
oxidant present in plasma membranes (Wang
and Quinn
2000
) .
The treatment of cows with antioxidants to
improve fertility in summer has given inconsis-
tent results. Effects of antioxidants on reproduc-
tive function may be more pronounced during
heat stress because of the increased metabolic
rates associated with cellular hyperthermia. High
temperature increases liver peroxidation (Ando
et al.
1997
), and activity of enzymes involved in
free radical production such as xanthine oxidase
is also increased. Exposure of dairy cows to heat
stress decreased total antioxidant activity in
blood. Like most cells, preimplantation embryos
can produce free radicals (Yang et al.
1998
) .
TrxR1 also can facilitate the gene expression of
other cytoprotective antioxidant enzyme factors,
such as heme oxygenase in bovine endothelial
free radicals (Bernabucci et al.
2002
) and there-
fore require a greater supplementation of anti-
oxidants. Table
4
shows the suggested feeding
levels of vitamin E and minerals for cows.
As has been indicated earlier, free radicals are
formed as a normal end product of cellular
metabolism arising from either the mitochondrial
electron transport chain or from stimulation of
NADPH (Valko et al.
2007
) . The presence of free
radicals leading to oxidative reactions in the
organism is physiological, and oxidative stress
occurs when there is increased production of free
radicals and reactive oxygen species, and/or a
decrease in antioxidant defence system. Oxidative
stress results in damage of biological macromo-
lecules and disruption of normal metabolism and
physiology (Trevisan et al.
2001
) . Heat stress
generally increases the production of free radi-
cals that lead to oxidative stress. Under normal
physiological conditions, antioxidant defence
systems within the body can effectively neutralise
the ROS that are produced and eliminate them.
Supplementation of antioxidants to the cows
before heat stress starts and also during the stress
