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Montgomery, J. Mahan, D. B. Wester and C. Melton
R. E. Schmidt, J. H. Fike, X. Zhang, J. Y. Ayad, C. P. Brown, M. F. Miller, J. L.
V. G. Allen, K. R. Pond, K. E. Saker, J. P. Fontenot, C. P. Bagley, R. L. Ivy, R. R. Evans,
review A−−Tasco: Influence of a brown seaweed on antioxidants in forages and livestock
2001, 79:E21-E31.J ANIM SCI
http://www.journalofanimalscience.org/content/79/E-Suppl/E21
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Tasco: Influence of a brown seaweed on antioxidants
in forages and livestock—A review1
V. G. Allen*†
2
, K. R. Pond†, K. E. Saker§, J. P. Fontenot¶, C. P. Bagley**, R. L. Ivy††,
R. R. Evans††, R. E. Schmidt#, J. H. Fike#, X. Zhang#, J. Y. Ayad*, C. P. Brown*,
M. F. Miller†, J. L. Montgomery†, J. Mahan‡‡, D. B. Wester‡, and C. Melton*
Departments of *Plant and Soil Science, †Animal Science and Food Technology, and ‡Range, Wildlife, and
Fisheries Management, Texas Tech University, Lubbock, 79409; §Department of Large Animal Clinical
Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State
University, Blacksburg 24061-0442; Departments of ¶Animal and Poultry Sciences and #Crop and Soil
Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061; Mississippi
State University, **Starkville 39762 and ††Prairie 39761; and ‡‡USDA-ARS, Lubbock, TX 79415
ABSTRACT: Tasco-Forage, an extract from the
brown seaweed Ascophyllum nodosum, has increased
antioxidant activity in both plants and animals. Turf
and forage grasses exhibited increased amounts of α-
tocopherol, ascorbic acid, β-carotene, and increased ac-
tivitiesofsuperoxidedismutase,glutathionereductase,
and ascorbate peroxidase in response to exogenous ap-
plicationofTasco.Endophyte (Neotyphodium coenophi-
alum [(Morgan-Jones and Gams) Glenn, Bacon, and
Hanlin]-infected tall fescue (Festuca arundinacea
Schreb.) can increase oxidative stress. Both high envi-
ronmental temperatures and increased body tempera-
tures increase respiratory rates, which increase free
radical production. Steers that grazed infected fescue
had diminished immune function and vitamin E, Cu,
and Se status, indicating less ability to deal with oxida-
tive stress. Two applications of Tasco-Forage (3.4 kg/ha
in water solution) to infected fescue during the growing
season improved steers’ immune function, and the ef-
fect lasted through cross-country transportation and a
160-d feedlot finishing period. Grazing infected fescue
reduced serum cholesterol, but the effect was reversed
Key Words: Health, Immunology, Seaweeds, Stress
2001 American Society of Animal Science. All rights reserved. J. Anim. Sci. 79(E. Suppl.):E21–E31
Introduction
Seaweedsarepredictablesourcesofplant growth reg-
ulators, especially cytokinin (Senn, 1987; Crouch and
1
Approved by the Dean of the College of Agriculture and Natural
Resources, Texas Tech Univ. Publ. No. T-4-491.
2
Correspondence: E-mail: felician@ttacs.ttu.edu.
Received July 28, 2000
Accepted March 23, 2001.
E21
by Tasco, indicating effects on lipid metabolism.
ApplyingTascotolow-endophytefescue seemed to have
an immune-dampening effect on steers, at least during
the grazing season. At slaughter, marbling was greater
in retail cuts of meat and meat had a longer shelf-life
ifsteers hadgrazedthe Tasco-treatedfescue,regardless
oftheendophyte.Directsupplementation to steers with
Tasco-EX (extract) during the final 14 d in the feedyard
also extended shelf-life of strip loins. Supplementation
of Tasco-EX or Tasco-14 (meal) to porcine reproductive
and respiratory syndrome-stressed pigs during the
nursery phase improved weight gain and feed intake
within 35 d. Supplementing Tasco-EX in drinking wa-
ter failed to reduce morbidity and mortality in trans-
ported heifers stressed by Pasturella haemolytica. The
mode of action of Tasco is not clear, but antioxidants
and specific vitamins may be involved. Supplementa-
tion with certain antioxidants can have beneficial ef-
fects, but inappropriate use can have detrimental ef-
fects. Although positive effects on stress tolerance and
carcass composition are apparent, further research is
needed to elucidate these relationships and to provide
predictable responses.
Van Staden, 1993; Jameson, 1993). R. E. Schmidt and
co-workers (Nabati, 1991; Yan, 1993; Sun, 1994) dem-
onstrated improved stress tolerance of several turf-
grasses in response to an extract from Ascophyllum
nodosum. They observed increased concentrations of
nutrient antioxidants including α-tocopherol and
ascorbic acid as well as the antioxidant enzyme super-
oxide dismutase (SOD; Zhang and Schmidt, 1999).
These observations led to experiments with livestock
grazing tall fescue infected or not with the endophyte
fungus Neotyphodium coenophialum ([Morgan-Jones
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Allen et al.E22
and Gams] Glenn, Bacon, and Hanlin; Glenn et al.,
1996). Although presence of the endophyte imparts
stresstolerancetotheplant(Hoveland,1993), it results
in several disorders in livestock commonly referred to
as fescue toxicity (Stuedemann and Hoveland, 1988).
Immune function was impaired (Dawe et al., 1997; Sa-
ker et al., 1998) but this was reversed by pasture appli-
cations of Tasco-Forage, a proprietary product based
on A. nodosum (Allen et al., 2001; Saker et al., 2001).
Antioxidants are essential in mediating and protecting
the immune system (Dubeski, 1999) and to offset oxy-
gen free radicals produced during stress and disease
(Halliwell, 1996). Supplemental vitamin E is used to
extend shelf-life of meat during retail display by im-
proving color stability, reducing lipid oxidation, and
delaying metmyoglobin formation (Faustman et el.,
1989; Arnold et al., 1993; Smith et al., 1996). Treating
pastures with Tasco or directly supplementing steers
during the final 14 d on the feedlot also extended beef
color stability (Montgomery et al., 2001).
Tasco may have value in up-regulating antioxidant
responses in both plants and animals. Effects on im-
mune function and shelf-life of meat during retail dis-
playsuggestarelationshipwithantioxidantsas a mode
of action.
Oxidative Stress and Antioxidants
Oxygen, although essential to life, is a toxic sub-
stance. As atmospheric oxygen levels rose over geologic
time to present-day levels, respiring organisms evolved
elaborate defense mechanisms against oxygen toxicity
(Halliwell,1996). Gerschmanetal. (1954)proposedthat
formation of oxygen radicals was responsible for the
damaging effects of oxygen. Halliwell (1996) in his re-
view of Gerschman et al. (1954) suggests that “in its
simplest form, this theory states that oxygen toxicity
is due to excess formation of superoxide radical (O
2.−
)
and that the superoxide dismutase enzymes are im-
portant antioxidant defenses.” Antioxidants scavenge
or prevent formation of free radicals. Free radicals are
species capable of independent existence that contain
one or more unpaired electrons (Halliwell, 1996). Free
radicals result from several sources, including electro-
magnetic radiation from the environment, accidents of
chemistry, as deliberate defense mechanisms against
infection, or for use in physiological functions such as
regulation of blood pressure and intercellular signaling
(Fridovich, 1986; Babior and Woodman, 1990; Moncada
andHiggs, 1993).Eventhough thegeneral perception of
antioxidantshas been that they are essential to prevent
formationof free radicals or to interrupt chainreactions
that free radicals precipitate, indiscriminate use of an-
tioxidantsraises concerns.For instance,supplementing
β-caroteneto smokers apparentlyacceleratedthe devel-
opment of lung cancer (a-Tocopherol, β-Carotene Pre-
ventionStudy Group, 1994). Conversely,oxygenmetab-
olites are generated during normal immune cell re-
sponse (Dubeski, 1999). Phagocytic cells generate large
amounts of O
2.−
as part of the mechanism that kills
foreign organisms (Babior and Woodman, 1990).
An approximate balance is maintained between pro-
duction of oxygen species and antioxidant defenses, but
if the balance is shifted in favor of reactive oxygen spe-
cies, oxidative stress results (Halliwell, 1996; Sies,
1991). Mild oxidative stress often results in up-regula-
tion of the synthesis of antioxidant defense systems to
restore the balance (Iqbal et al., 1989); however, major
derangementsof cell metabolism resulting in cell injury
and death can occur with severe oxidative stress (Sies,
1991). Enzymes involved in antioxidant defenses in-
clude SOD, which acts by catalyzing the conversion of
O
2.−
tohydrogen peroxide (H
2
O
2
;McCord and Fridovich,
1969; Halliwell, 1996). Selenium-containing glutathi-
one peroxidase is likely the most important H
2
O
2
-re-
moving enzyme in animals (Chance et al., 1979).
Dietmay prevent ordiminishoxidative stress to some
extent. α-Tocopherol, the major component in vitamin
E, and ascorbic acid are important antioxidants. α-
Tocopherolinhibits lipidperoxidation,and ascorbicacid
may have multiple antioxidant properties. Current in-
formation suggests that an optimal dietary intake of
specific antioxidants may aid in protection against car-
diovascular disease, some forms of cancer, intracranial
hemorrhage, and other disorders in humans, but more
information is needed to define optimal levels and con-
ditions. Supplementation of livestock diets with vita-
minE subsequently has extended meatshelf-lifeduring
retail display and reduced drip loss (Mitsumoto et al.,
1998), and it may reduce morbidity and mortality fol-
lowing stress (McDowell et al., 1996). Effects of dietary
deficiencies of Se, Cu, Fe, Zn, and other nutrients in-
volved in antioxidant function have long been recog-
nized in human and livestock nutrition and health. The
beneficial effect of a diet high in fruits, vegetables,
grains,andnuts is perhaps due to the antioxidants they
contain (Larson, 1988; Halliwell, 1996). Larson (1988)
suggested that the evidence supports at least a partial
antioxidantrole in vivo for manyclassesofplant metab-
olites. Recent research with the brown seaweed Asco-
phyllum nodosum has demonstrated antioxidant-
altering properties in plants treated with an extract
from the seaweed and in animals fed the seaweed-
treated plants or fed seaweed in the diet.
Seaweeds and Tasco (Ascophyllum nodosum)
Seaweeds have been used in animal feeds, as soil
conditioners, and as a source of minerals for plants
and animals since antiquity, but reported benefits have
largely been based on producers’ experience and unrep-
licated studies. Some claims seem unfounded and have
frequently been discounted. Ascophyllum nodosum is
themostwidelyresearched seaweed species for agricul-
tural purposes. Evidence of plant growth hormones in
seaweed was reported as early as the 1950s (Senn,
1987).Seaweed now is recognizedasanexcellent source
of natural plant growth regulators with demonstrated
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Tasco: A review E23
activity (Crouch, 1990; Crouch and Van Staden, 1993;
Jameson, 1993), which include cytokinins (Blunden,
1977), auxins (Sanderson et al., 1987), and gibberellins
(Wildgoose et al., 1978). Seaweeds contain substituted
phenols and polyphenols, a class of compounds that
have antioxidant activity (Le Tutour, 1990). Vitamins
and vitamin precursors contained in seaweeds include
a-tocopherol (Jensen, 1969), β-carotene, niacin, thia-
min, and ascorbic acid (Jensen, 1972).
Ascophyllum nodosum isfoundgrowing in the littoral
zone(coastlinebetweenhigh and low tides) of the North
Atlantic Ocean extending from Nova Scotia to Norway.
Tasco is a proprietary product from A. nodosum har-
vested off the coast of Nova Scotia (Acadian Seaplants
Ltd., Dartmouth, Nova Scotia, Canada). Tasco-EX and
Tasco-Forage are water-soluble extracts from A. nodo-
sum derived with an alkaline hydrolysis procedure.
Tasco-EX is used for livestock feeding, and Tasco-For-
age is applied in water solution to plants (see Fike et
al., 2001 for approximate chemical composition). Tasco-
14is a meal derived from solar-dried, intact A. nodosum
(Table 1). Research with both plants and livestock dur-
ing the past 10 yr has suggested that application of
Tasco to plants or direct ingestion by livestock upregu-
lates antioxidant function in both the plant and the
animal (Ayad, 1998; Fike et al., 2001; Montgomery et
al., 2001).
Plant Effects
Plant growth regulators differ from fertilizers. Plant
growth regulators alter cell division, root and shoot
elongation, initiation of flowering, and other metabolic
functions, whereas fertilizers simply supply minerals
neededfor the nutritionandnormal growth oftheplant.
Cytokinin is regarded as the most important plant
growth regulator in seaweed (Senn, 1987). However,
trace minerals present in seaweed extract may play
a role in plant nutrition and physiology, probably as
enzyme activators. This is the case for Mo, a metal ion
essential for the activity of xanthin dehydrogenase, an
enzyme tightly related to antioxidant activity in
stressed plants (Sagi et al., 1998).
In general, plants under stress have shown a reduc-
tion in cytokinin levels (Hare and Van Staden, 1997),
apparently in response to increased internal ethylene
production, among other possible compounds. Ethylene
reduces cytokinins and auxins, leading to alterations
in tissue differentiation (Sanyal and Bangerth, 1998).
Research with plants treated with exogenous cytokinin
has demonstrated improved drought tolerance (Yan,
1993), greater salt tolerance (Nabati et al., 1994), in-
creased root and shoot growth (Goatley and Schmidt,
1990), and increased total nonstructural carbohydrates
(Kane and Smiley, 1983). Seaweed extract from Asco-
phyllum nodosum has also been shown to elicit these
responses in grasses (Schmidt and Zhang, 1997; Yan,
1993; Nabati et al., 1994). Plant responses to seaweed
extract generally have been greater than when purified
Table 1. Approximate composition
a
of Tasco-14, an
Ascophyllum nodosum seaweed meal
used in livestock feeds
Item Value
Crude fiber, % 6.0
Carbohydrates,% 52.0
Ash, % 22.0
Moisture, % 12.0
Crude protein, % 6.0
Minerals
Aluminum, ppm 20–100
Arsenic, ppm <3
Calcium, % 1.0–3.0
Copper, ppm 4–15
Iodine, ppm <1,000
Magnesium, % 0.5–1.0
Manganese, ppm 10–50
Phosphorus, % 0.1–0.2
Potassium, % 2–3
Selenium, ppm <1
Sodium, % 2.4–4.0
Sulphur, % 2.0–2.3
Zinc, ppm 35–100
Amino acids, g of amino acid/100 g of protein
Alanine 5.3
Arginine 8.0
Aspartic acid 6.9
Cystine trace
Glutamic acid 10.0
Glycine 5.0
Histidine 1.3
Isoleucine 2.8
Leucine 4.6
Lysine 4.9
Methionine 0.7
Phenylalanine 2.3
Proline 2.6
Serine 3.0
Threonine 2.8
Tyrosine 0.9
Valine 3.7
a
Acadian Seaplants Limited, Dartmouth, Nova Scotia.
cytokinin was applied alone (Goatley and Schmidt,
1991), and the magnitude of response may relate to the
balance of plant growth-regulating substances in
seaweed.
Plant growth and stress tolerance are regulated
largely by hormonal balance that determines accelera-
tion or restraint of growth. Rapid growth is usually
coupled to transport of cytokinins from roots to shoots,
and slow growth results from a drop in cytokinin trans-
port and an enhanced mobilization of abscisic acid
through xylem sap (Peuke et al., 1994). Cytokinin has
a dual effect regarding the production of oxygen free
radicals under stress conditions (McKersie and Les-
hem,1994).Thefirst is prevention of free radical forma-
tion through inhibition of xanthine oxidation by the
enzyme xanthine oxidase. Cytokinin has a structural
resemblance to xanthine and acts as a competitive in-
hibitor of xanthine oxidase and xanthine dehydroge-
nase, thus reducing the amount of free radicals formed
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Allen et al.E24
inthecells.Thesecondmechanism is by direct scaveng-
ingof free radicals.Salinity,drought, andotherstresses
induce the generation of these activated oxygen species
(Kayupova and Klyshev, 1987; Elstner et al., 1988).
The mechanism of increased stress tolerance in
plants due to seaweed extract may be through an effect
ofcytokinin on oxygenfreeradicals, but increasedactiv-
ity of several other antioxidants in seaweed-treated
grasses also has been documented. Superoxide dismu-
tase, glutathione reductase, and ascorbate peroxidase
each were increased (P<0.05) in ‘KY-31’ tall fescue
(Festuca arundinacea Schreb.) in response to applica-
tion of Tasco-Forage (Figure 1; Ayad, 1998). Increased
α-tocopherol, β-carotene, ascorbic acid, and SOD activi-
ties in seaweed-treated turfgrasses have been mea-
sured (Schmidt and Zhang, 1997; Zhang, 1997; Zhang
and Schmidt, 1999; Figures 2 and 3). The ability of
Tasco to influence plant endogenous antioxidant activ-
ity has been demonstrated by both foliar application
(Zhang and Schmidt, 1999; Fike et al., 2001) and soil
application (Ayad, 1998).
Tasco-Forage applied to infected and uninfected tall
fescue pastures in Virginia increased SOD activity, and
the effect lasted throughout the grazing season (Allen
et al., 1997; Fike et al., 2001; Figure 4). Tasco-Forage
(3.4 kg/ha) was applied in water solution in April and
July, and the effect was measurable into November.
Theseresults were repeatedover3 yr andinMississippi
as well as Virginia (Fike et al., 2001). Presence of the
Figure 1. Superoxide dismutase (SOD), glutathione re-
ductase (GRX), and ascorbate peroxidase (APX) in ‘KY-
31’ tall fescue treated (T+) or not (T−) with 3.4 kg of Tasco-
Forage/ha in a 2-yr field experiment. Data are averaged
over endophyte level (infected and non-infected) and
year. *, ***Effect of treatment (P<0.05 and 0.001, respec-
tively). Adapted from Ayad (1998).
Figure 2.α-Tocopherol of Kentucky bluegrass treated
(T+) or not (T−) with 326 g of Ascophyllum nodosum ex-
tract/ha at two soil moisture levels. α-Tocopherol dif-
fered due to A. nodosum (P<0.01) but did not interact with
soil moisture. Adapted from Zhang and Schmidt (1999).
Figure 3. Ascorbic acid of Kentucky bluegrass treated
(T+) or not (T−) with 326 g of Ascophyllum nodosum ex-
tract/ha at two soil moisture levels. Ascorbic acid differed
due to A. nodosum (P<0.01) and soil moisture (P<0.05)
but no interaction was present. Adapted from Zhang and
Schmidt (1999).
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Tasco: A review E25
Figure 4. Superoxide dismutase activity in endophyte-
infected (E+) and -free (E−) tall fescue treated (T+)ornot
(T−) with 3.4 kg of Tasco-Forage/ha in April and July in
a pasture experiment and sampled at 28-d intervals dur-
ing the growing season.
a
Effect of Tasco (P<0.05);
b
Effect
of Tasco (P<0.10). Adapted from Allen et al. (1997).
endophyte also may influence SOD. Fike et al.(2001)
found that the endophyte had no effect on SOD in Vir-
ginia but increased activity in fescue grown in Missis-
sippi. Ayad (1998) reported that the endophyte in-
creased SOD activity by about 23% in genetically simi-
lar infected and uninfected ‘KY 31’ tall fescue grown in
the southern High Plains of Texas. Climatic stress may
interact with the endophyte to alter effects on SOD.
Animal Effects
Antioxidant responses have been measurable in live-
stock that either grazed Tasco-treated forage or were
directly supplemented with Tasco-EX (extract) or
Tasco-14 (meal). Lambs that grazed for 22 d on tall
fescue (70 to100% infected) treated with 0, 1.7, or 3.4
kg Tasco/ha exhibited a linear increase (P<0.05) in
daily gains, and serum vitamin A (P<0.13) and whole-
blood Se (P<0.10) tended to increase (Fike et al., 2001).
Beef steers that grazed Tasco-treated infected or unin-
fected tall fescue in Virginia during 1995 also exhibited
a strong trend (P<0.10) for increased whole-blood Se
by the end of the grazing season in September (Fike et
al., 2001). Later work confirmed this effect in both se-
rum and whole-blood Se (W. Cradduck, V. Allen, and
P. Brown, unpublished data).
There seems to be a relationship among the endo-
phyte, Tasco, and vitamin E status in grazing beef
steers. The evidence suggests an interaction when in-
fected fescue is treated with Tasco compared with ef-
fectswhen Tasco is applied to uninfected fescue. Effects
ofbothendophyte and Tasco seem long-lasting. Season-
long pasture experiments in Virginia and Mississippi
demonstratedlower serum vitamin E in steers that had
grazed infected, compared with uninfected tall fescue
(Fike et al., 2001). Effects of Tasco on serum vitamin
E were inconclusive during the pasture phase. Follow-
ing the pasture phase, all steers were transported to
Texas for feedlot finishing. The lower serum vitamin E
due to endophyte was measurable on arrival in Texas,
but the effect of endophyte on vitamin E was at least
partially offset if the pasture had been treated with
Tasco (Allen et al., 2001).
Dietary vitamin E consists primarily of α- and γ-
tocopherol and is absorbed in a manner similar to fat
(Sokol, 1996). Vitamin E is absorbed into the intestinal
mucosal cell and, once inside the enterocyte, is incorpo-
rated into chylomicrons. Sokol (1996) suggested that
any pathologic process that impairs digestion and ab-
sorption of dietary fat can lead to poor absorption of
vitaminE. Thereisa strongcorrelation between plasma
tocopherol concentrations and total plasma lipid con-
centration due to the high lipid solubility of vitamin E
and its transport in lipoproteins (Horwitt et al., 1972).
Thus, it has been suggested that serum vitamin E
should be normalized to the total plasma lipid concen-
tration to evaluate tocopherol status (Horwitt et al.,
1972).
The relationship of vitamin E to lipid metabolism
is of particular interest in interpreting effects of the
endophyte and Tasco. Stuedemann et al. (1985) found
a relationship of the endophyte with lowered plasma
cholesterol, total lipids, and lipid metabolism in both
cows and steers during the grazing season. Allen et al.
(2001) confirmed this effect of infected fescue in steers
transported from Virginia and Mississippi to Texas.
Furthermore, the effect on cholesterol was reversed if
infected fescue had been treated with Tasco. However,
when serum vitamin E was normalized with serum
cholesterol, effects of endophyte were still apparent but
no effect of Tasco on the ratio was observed. Because
vitaminEistransported in the blood by plasma lipopro-
teinsand erythrocytes,theratio isparticularlyvaluable
in pathological states in which altered lipoprotein con-
centrations and vitamin E deficiency may be expected
(Traber et al., 1993). When plasma lipids and lipopro-
tein concentrations are reduced, such as is observed
with effects of endophyte on cholesterol, vitamin E defi-
ciency would be overestimated.
At slaughter, concentrations of vitamin E in liver
were greater if steers had grazed Tasco-treated pas-
tures prior to finishing in drylot, regardless of the endo-
phyte (Montgomery et al., 2001). Unfortunately, no
data were available on vitamin E concentrations in
muscle. It is not clear why liver vitamin E would reflect
treatments applied to pasture grazed 160 d prior to
the feedlot period. Vitamin E, initially transported in
chylomicrons, is released to tissues or transferred to
lipoproteins but eventually much of the vitamin E re-
turns to the liver in chylomicron remnants (Sokol,
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Allen et al.E26
1996). Turnover of vitamin E is estimated to be 5 to 20
d in liver (Burton and Ingold, 1993) and large amounts
never accumulate because of the function of tocopherol
in transfer protein (Sokol, 1996).
There are several interesting parallels between
known effects of vitamin E and effects obtained with
Tasco.VitaminE fed to beef cattle during feedlot finish-
ing has extended shelf-life by improving color stability,
reducing lipid oxidation, and delaying metmyoglobin
formation(Faustman etal.,1989a,b; Smithetal., 1996).
Montgomery et al. (2001) found that color stability dur-
ing retail display was prolonged in steaks from steers
thathad grazedTasco-treatedtall fescue priorto feedlot
finishing. It is not known whether this was due to vita-
min E, other antioxidants, or unidentified factors. Di-
rect feeding of Tasco-EX to steers during the final 14
d in the feedlot also resulted in improved color stability
(Figure 5; D. Messer, K. Pond, and V. Allen, unpub-
lished data).
Mitsumoto et al. (1998) found that dietary supple-
mentation with vitamin E for 1 wk prior to slaughter
delayed lipid oxidation in beef steaks and reduced drip
loss, compared with controls. In another experiment
Mitsumoto et al. (1995) found that dietary vitamin E
reduced drip loss but longissimus steaks had greater
cooking loss. Similarly, Montgomery et al. (2001) re-
ported greater cooking loss in beef longissimus steaks
Figure 5. Visual color values of beef longissimus steaks
during retail display following removal of vacuum pack-
ing from feedlot-finished steers fed 0, 1, or 2% Tasco-Ex
as a percentage of the diet dry matter during the final 14
d in the feedlot. Means are averaged over four periods;
meat was removed from vacuum packaging and steaks
were cut on postmortem d 7, 14, 21, and 28. (D. Messer,
K. Pond, and V. Allen, unpublished data).
a
Control differs
from the mean of the treated (P<0.01).
Figure 6. Cooler shrink in swine fed Tasco-Ex and
Tasco-14 during the first 10 d (S) or Tasco-14 during the
entire 5 wk (L) of the nursery phase after weaning. Tasco
was fed at 1% of the daily DM intake during the treatment
period. Treatment groups were fed a similar diet without
Tasco during the growing and finishing phases. Tasco-
Ex-S tended to differ from the control (P<0.10) and Tasco-
14-L differed from the control (P<0.03). K. Pond, V.
Allen, and J. Montgomery, unpublished data.
from steers that grazed Tasco-treated fescue followed
by finishing in drylot, and the effect was unrelated to
endophyte status in the fescue. Drip loss was not mea-
sured in that experiment.
Less drip loss from thawed pork chops obtained from
vitaminE-supplementedswinewasreported by Asghar
et al. (1991). Direct supplementation of Tasco-EX and
Tasco-14 to pigs during the nursery phase resulted in
less cooler shrink (Figure 6; K. R. Pond, V. G. Allen,
and J. Montgomery, unpublished data). Pigs were sup-
plemented with either Tasco-EX or Tasco-14 for the
first 10 d or with Tasco-14 during the entire 5 wk of
thenursery period at 1% of the daily DM intake. Effects
of a 10-d supplementation period with the extract
seemedtohave effects similar to those of a 5-wk supple-
mentation period with the meal. A 10-d supplementa-
tion period with the meal did not produce results differ-
ent from controls. All treatment groups received the
same diet during the growing and finishing phases and
no further supplementation was imposed after the
nursery phase. Inclusion of either Tasco-EX for 10 d or
Tasco-14 for 35 d in the diets at the nursery phase
altered the percentage of free, bound, and immobilized
water in muscle after slaughter (Figure 7); this may
help to explain differences in cooler shrink. Feeding
Tasco-14 for 10 d did not seem to elicit responses differ-
ent from controls.
The mechanism of effect on drip loss, cooler shrink,
and altered partitioning of water form in these experi-
ments is not known but may be related to vitamin E
and other antioxidants and effects on lipid metabolism.
Vitamin E is known for its role as a scavenger of free
radicals,thus protecting cell membranesfromoxidative
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Tasco: A review E27
damage (Sokol, 1996). Mitsumoto et al. (1995) sug-
gested that dietary vitamin E stabilized cell integrity
and enhanced the ability of beef muscle to retain sarco-
plasmic components that resulted in less drip.
Steers that grazed fescue pastures treated with
Tasco-Forage had higher marbling scores, regardless
of the endophyte (Allen et al., 2001). The greater degree
of marbling may provide further evidence of altered
lipid metabolism due to Tasco. Direct feeding of Tasco
to steers during the finishing period has had variable
effects on marbling at slaughter. The amount of Tasco
supplemented as well as the time at which it is intro-
duced into the diet may affect results. Steers fed Tasco-
EX at 2% of the diet during the first 10 d on the feedlot
had higher (P<0.05) marbling scores at slaughter than
unsupplemented steers (J.W. Johnson, K. Pond, and V.
Allen, unpublished data). However, feeding 0, 1, and
2% Tasco-EX during the final 14 d of the feedlot finish-
ing period did not influence marbling in steers, al-
though color stability was improved (D. Messer, K.
Pond, and V. Allen, unpublished data).
Immune Function
Interrelationships among Tasco, the endophyte in
tall fescue, and immune function have been demon-
strated. Presence of the endophyte was related to lower
phagocytic activity, oxidative burst, and major histo-
compatibility complex class II expression in steers (Sa-
ker et al., 1998, 2001; Allen et al., 2001). Steers that
Figure 7. Percentage of free, bound, and immobilized
water in muscle from postslaughter swine that had been
fed Tasco-Ex and Tasco-14 during the first 10 d (S) or
Tasco-14 during the entire 5 wk (L) of the nursery phase
after weaning. Tasco was fed at 1% of the daily DM intake
during the nursery phase and treatment groups were fed
a common diet without Tasco during the growing and
finishing phases. The control differed from the mean of
the treatments (P<0.05) for each water fraction. ( J. Mont-
gomery, K. Pond, and V. Allen, unpublished data).
Figure 8. Monocyte phagocytic activity in steers that
grazed endophyte-infected (E+) or endophyte-free (E−)
tall fescue in Virginia and Mississippi during 1996 and
1997 that was either treated (T+) or not (T−) with Tasco-
Forage, a brown seaweed extract. Steers were finished on
the feedlot in Texas following the pasture phase (adapted
from Saker et al., 2001 and Allen et al., 2001).
a
Endophyte
×Tasco interaction (P<0.05);
b
effect of Tasco (P<0.02).
grazed infected tall fescue treated with Tasco-Forage
responded with increased phagocytic activity (Figure
8)and major histocompatibility complex class II expres-
sion (Allen et al., 2001; Saker et al., 2001). This in-
creased immune response continued while steers were
on pasture, throughout cross-country transportation,
and during a 160-d feedlot finishing period (Allen et
al., 2001). The enhanced immunity seems to be related
to an increase in antioxidant activity in both plants and
animals (Allen et al, 1997; Fike et al., 1997; Schmidt
and Zhang, 1997). Vitamin E is closely related to im-
mune function (Sokol, 1996; Dubeski, 1999). Vitamin
E deficiency in cattle reduces the ability of phagocytes
to engulf and kill invading pathogens (Dubeski, 1999),
and feeding vitamin E at levels greater than normal
requirementsstimulatesimmunity (Bendich, 1993; Ho-
gan et al., 1993). In steers grazing infected tall fescue,
lowered phagocytic activity was paralleled by lowered
serum vitamin E (Fike et al., 2001; Saker et al., 2001).
Treating the infected fescue with Tasco increased both
phagocytic activity and serum vitamin E. Although not
measuredin theseexperiments,the previouslyreported
effects of Tasco on a-tocopherol in grasses suggests that
itmayhaveplayedaroleineffectsonthegrazingsteers
(Zhang and Schmidt, 1999). Superoxide dismutase was
increased in the fescue in response to Tasco (Fike et
al., 2001) and also may have been related to enhanced
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Allen et al.E28
immune function. Copper in plant SOD may help to up-
regulate SOD activity in cattle, but Cu has been shown
to be lower in infected fescue (Dennis et al., 1998) and
steers (Saker et al., 1998) that grazed infected fescue.
Copper in plant SOD may directly improve phagocytic
cell function, because this is altered by dietary Cu
changes. Changes in blood Cu levels of steers that
grazed Tasco-treated fescue were not detected (Fike et
al., 2001), but blood Cu may be too insensitive as a Cu
status marker. Microbicidal activity is contingent on a
free-radical process, and it is suspected that increased
immunityisperhaps one manifestation of a generalized
increase in SOD activity. Other antioxidants also may
havebeen involved, and both enzyme andnutrientanti-
oxidants are known to increase in grasses following
Tasco application (Ayad, 1998; Zhang and Schmidt,
1999). Although not measured, dietary intake of α-to-
copherol, ascorbic acid, and β-carotene was likely
higher in steers that grazed the Tasco-treated forage
than in those that grazed the untreated fescue. Im-
portantantioxidants that canbeaffected by dietinclude
vitamin E, glutathione peroxidase, SOD, and catalase,
and these depend on sufficient vitamin E, Se, Cu, Zn,
Mn, and Fe in the diet (Dubeski, 1999). Although cattle
synthesize ascorbic acid, amounts may not meet re-
quirements under stress, and supplementation with di-
etary sources could be beneficial if protected from rumi-
nal degradation (Dubeski, 1999).
Although treating infected fescue with Tasco-Forage
seemed beneficial in reversing the depression in im-
mune function, applying Tasco-Forage to uninfected
fescue seemed to have an immune-dampening effect,
at least during the grazing season (Saker et al., 2001).
Dubeski (1999) suggested that a small excess intake of
certain nutrients, including β-carotene, vitamin E, Zn,
and Se seems to enhance immune response, but when
they are supplied above a certain threshold, immunity
can be depressed. This may have played a role in the
observed result with uninfected tall fescue. Superoxide
dismutasewasincreasedinuninfected fescue and other
antioxidants were likely increased (Ayad, 1998; Fike et
al., 2001; Zhang and Schmidt, 1999). Immunosuppres-
sive effects of antioxidants in the absence of oxidative
stress have been observed in vitro (Gougerot-Pocidalo
and Revillard, 1993).
Research in Japan with edible seaweeds has sug-
gested possible immunomodulating activities in hot-
water-soluble extracts. Hijikia fusiforme (hijiki)
showed an enhancing activity for proliferative response
of spleen cells in endotoxin-nonresponder C3H/HeJ
mice, and a possible immunopotentiating activity
against carcinogensis was suggested (Okai et al., 1998).
An extract from Laminaria japonica (makonbu) was
shown to enhance DNA synthesis of spleen cells from
mice (Okai et al., 1996). Their results suggest immuno-
modulating activity.
Effects of Tasco on immune function do not seem to
be restricted to effects on forage. Steers in the feedlot
fed Tasco-14 at 1.5 and 3% of dry matter intake exhib-
ited greater immune response to intradermal injection
with phytohemagglutinin than steers fed no Tasco, but
performanceof steers was reducedbyTasco supplemen-
tation (V. Allen, K. Pond, and K. Saker, unpublished
data).
Enhancedimmune response suggests Tasco mayhelp
to reduce morbidity and mortality during times of
stress. However, initial studies with calves fed Tasco-
EX or Tasco-14 following transportation, vaccination,
and sale barn stresses have indicated a trend for in-
creased morbidity due to Tasco treatment. Crossbred
beefheiferspurchasedthrough local sales barns in Ten-
nessee were given Tasco-Ex in the drinking water on
arrival at the farm (V. G. Allen and D. Thompson, un-
published data). Calves readily consumed the supple-
mented water but Tasco did not reduce incidence or
mortalityfrom chronic severe bronchopneumonia. Both
Pasturella haemolytica and P. multocida were isolated
from lung tissue. The timing of introducing Tasco into
the diet and the length of the supplementation period
may be crucial.
Supplementing vitamin E to receiving calves has fre-
quently but not consistently reduced morbidity and
mortality (McDowell et al., 1996). The response may be
influenced by previous nutrition, degree of stress, or
other factors (Dubeski, 1999). Furthermore, dietary
supplementation seems more effective than injecting
vitamin E, which may increase morbidity and reduce
weight gain (Dubeski, 1999).
Other research with Tasco has been more promising.
Lactating mares fed 1% Tasco-EX in the concentrate
for 14 d prior to weaning foals exhibited little change in
neutrophil:lymphocyte ratio during a 56-d period after
weaning. The neutrophil:lymphocyte ratio increased (P
<0.05) in control mares 14 d after weaning, indicating
a greater level of stress (H. Brady, J. Morrow-Tesch,
K. Pond, and V. Allen, unpublished data).
Porcine reproductive and respiratory syndrome
(PRRS) was an unrecognized viral disease of swine
until it was described in the United States in 1987
(Albina, 1997). Within herds, the disease spreads rap-
idly, and up to 95% of pigs can be affected within 2
to 3 mo. This disease affects pigs of any age but is
characterized by abortion, premature farrowing, still-
born and mummified pigs, and respiratory disease and
chronic poor performance of nursing and weaned pigs.
Of major economic importance, PRRS is thought to af-
fect more than two-thirds of the herds in the United
States (Bautista et al., 1993).
Pigs that had been exposed to PRRS and were symp-
tomatic were supplemented with 0, 0.5, or 1% Tasco-
EX or with 3% Tasco-14 during a 5-wk nursery phase.
Pigs supplemented with either form or rate of Tasco
gained more (P<0.05) body weight during the 5-wk
period than did controls (Figure 9; K. Pond, V. Allen,
and C. Melton, unpublished data). Improved (P<0.05)
feed intake and feed conversion also were recorded in
the Tasco-supplemented groups, compared with con-
trols. By the end of the feeding period, supplemented
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Tasco: A review E29
Figure 9. Body weight of postweaned pigs that were
supplemented with either 0.5 or 1% Tasco-Ex or 3% Tasco-
14 as a percentage of the daily dry matter intake during
35-d nursery phase.
a
The control differed from the mean
of the treated (P<0.01). K. Pond, V. Allen, and C. Melton,
unpublished data.
pigs tended to have slightly higher rectal temperatures
thancontrols. Altered rectaltemperature(either higher
or lower) in relation to Tasco has been a nearly consis-
tent finding in studies with cattle, but the cause is as
yet unknown (Allen et al., 2001; Saker et al., 2001; V.
G. Allen and K. R. Pond, unpublished data).
Vacca and Walsh (1954) reported an antibacterial
activity from an extract of Ascophyllum nodosum. Anti-
bacterial activity was found against 10 of 11 organisms
tested in vitro. Activity against both Gram-positive and
Gram-negativetypes was observed and included Esche-
richia coli. Vacca and Walsh (1954) investigated two
speciesof seaweed, A. nodosum andEnteromorpha com-
pressa, but only A. nodosum gave promising results.
These results are interesting in light of recent research
at Texas Tech University (Behrends et al., 2000). Pre-
liminary studies suggest that supplementing Tasco-EX
to steers during the final 14 d in the feedyard reduced
numbers of both E. coli and, specifically, O157:H7 pres-
entin feces andonthehide, but moreresearchisneeded
to verify these findings.
The immune system is complex and its interaction
with the neuroendocrine system is regulated by cytok-
ines secreted by white blood cells. Cytokines induce
fever, depress appetite and feed intake, and influence
metabolic adaptations to infection as they regulate the
immune response (Still et al., 1997). It is possible that
at least some of the effects of Tasco on livestock are
due to effects of cytokines. These effects include altered
rectal temperatures, reduced feed intake, and either no
effect on performance or a slight decrease in gain that
have been observed in some experiments.
There seem to be several parallels between effects of
vitamin E and effects of Tasco on animal responses,
but other factors are likely involved. The increased se-
rum Se in both lambs and steers that grazed Tasco-
treated tall fescue could indicate an increase in Se-
dependent glutathione peroxidase (Fike et al., 2001; W.
Cradduck, V. Allen, and P. Brown, unpublished data).
Glutathione reductase was increased in tall fescue
within1d of application of Tasco in a greenhouse exper-
iment (Ayad, 1998). Copper is known to be lower in
infected tall fescue (Dennis et al., 1998), and this was
reflectedin a decreaseinserumand plasma Cuinsteers
by the end of the grazing season (Saker et al., 1998).
Even though Tasco did not seem to alter Cu in either
the plant or the animal, Cu plays an integral roll in
SOD and ceruloplasmin, both antioxidants, and free
Cu is a powerful pro-oxidant (Halliwell, 1996). Other
nutrient and enzyme antioxidants may well be in-
volved.
Insummary, nutrition, immune function, and antiox-
idant activity are closely interrelated. During times of
stress, livestock are more susceptible to infectious dis-
ease because of stress-induced immunosuppression. In-
creasedoxidative stressdueto disease andthe resulting
up-regulation of an immune response increases the
needs for both enzymatic and nutrient antioxidants.
Tasco-Forage applied to grasses has increased concen-
trations of both enzyme and nutrient antioxidants in
theforage,includingseveralthatcanbe effectively sup-
plemented in the diet. Steers that grazed treated pas-
tures responded with improved immune function, car-
cass characteristics, and shelf-life of meat, particularly
if steers were stressed by the endophyte in tall fescue.
Treating uninfected tall fescue may result in immuno-
suppression, at least during the grazing season, but
seemed beneficial when grazing was followed by stress
oftransportationfollowedbyfeedlot finishing. Whether
or not a higher dietary intake of antioxidants is related
to the observed effects needs further investigation. Di-
rectsupplementationof livestock with Tasco also seems
promising to extend shelf-life and enhance immune re-
sponse, but more information is needed on its mode of
action and method of administration. Although some
responses of livestock seem strikingly similar to those
observed following vitamin E supplementation, it is
likely that vitamin E is not the only factor involved.
Implications
Antibiotics revolutionized human and animal health
during the last century, but increasing concerns with
antibiotic resistance, food safety, and animal welfare
have called many practices into question and increased
interest in nutraceuticals. Intricate interrelationships
exist among nutrition, immune and endocrine function,
antioxidant systems, health, and production. Tasco, an
extract or meal from the brown seaweed Ascophyllum
nodosum, has demonstrated plant growth-regulating
activity and up-regulates several enzyme and nutritive
antioxidants when applied to plants. At least some of
the antioxidant response is imparted to livestock that
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Allen et al.E30
graze treated forage or are fed these products directly.
If treatment of forage or direct feeding of Tasco can
predictably trigger desirable responses, then improved
animal health, reduced plant and animal stress, pro-
longed shelf-life, and increased safety and quality of
plant and animal products seem possible. The economic
benefits would be huge.
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