Carbohydrates and Fibers
Ability of Juvenile White Sturgeon (Acipenser
transmontanas) to Utilize Different Carbohydrate
Sources1
SILAS S. O. HUNG, F. KOFI FYHH-AIKINS, PAUL B. LUTES ANDRÜPINGXÜ
Department of Animal Science, university of California, Davis, CA 95616
INDEXING KEY WORDS:
•juvenile white sturgeon •carbohydrates
•lipogenesis •hyperlipidemia
MATERIALS AND METHODS
Diet preparation. Formulations of the eight diets are
given in Table 1. The formulations were similar to a
The ability of fish to utilize different types and levels
of carbohydrate sources differs among species (1). The
maximum dietary level of dextrin which does not de
press growth is 10% for yellowtail, 20% for red sea
bream, 30% for common carp (2) and 48% for chinook
salmon (3). The growth rate of chinook salmon fed diets
containing 20% of either glucose, maltose, dextrin or
potato starch decreases with increasing molecular weight
of the carbohydrate source (3). Furthermore, growth rates
of chinook salmon fed sucrose were comparable to rates
0022-3166/89 $3.00 ©1989 American Institute of Nutrition.
'This work is a result of research sponsored in part by National
Océanographieand Atmospheric Administration, National Sea Grant
College Program, Department of Commerce, under grant number
NA85AA-D-SG140, project number R/A-67, through the California
Sea Grant College Program, and in part by the California State Re
sources Agency. The U.S. Government is authorized to reproduce
and distribute for government purposes.
Received 25 October 1988. Accepted 26 January 1989.
727
Downloaded from jn.nutrition.org by on February 18, 2008
observed with glucose feeding and higher than rates
with fructose feeding. Common carp fed diets contain
ing 42% starch grew better than those fed dextrin, which
in turn supported better growth than glucose (4). There
was no difference in growth of red sea bream fed diets
with 25% of either starch, dextrin or glucose (4). The
growth rate of channel catfish fed a diet with 33.1%
dextrin was better than that of catfish fed a diet with
33.1% corn starch (5). Growth rates of channel catfish
fed either glucose, maltose or sucrose were significantly
lower than those fed dextrin or corn starch, but no
differences were apparent in those fed cellulose. Chan
nel catfish fed fructose had the lowest growth. There
are no data on the ability of white sturgeon to utilize
different carbohydrate sources.
Feeding high levels of either sucrose or fructose has
been shown to induce hepatic lipogenesis and hyper
lipidemia in rats (6-8) and humans (9), but not in rats
and humans fed similar levels of either glucose or mal
tose (10). There is no information on the lipogenic and
hyperlipidemic effects of feeding different carbohydrate
sources to fish. The objectives of the present study were
to gain insight into the relationship between digestion,
metabolism and utilization of different carbohydrate
sources by juvenile white sturgeon and to determine
possible lipogenic and hyperlipidemic effects of feeding
sturgeon different carbohydrate sources.
ABSTRACT
Juvenile white sturgeon were fed isonitrogenous diets containing 27.2% glucose, fructose, maltose,
sucrose, lactose, dextrin, raw corn starch or cellulose for
8 wk. Growth, body composition, plasma chemistry (with
the exception of glucose), and liver glucose-6-phosphate
dehydrogenase (G6PDH, EC 1.1.1.49), malic enzyme (EC
1.1.1.40) and ¡sodtrate dehydrogenase (ICDH, 1.1.1.42)
activities of sturgeon were significantly (P < 0.05) affected
by the different dietary carbohydrate sources. Sturgeon fed
either the maltose or glucose diets had the highest percent
energy retained, followed by those fed either the dextrin,
raw corn starch or sucrose diets, whereas those fed either
the lactose, fructose or cellulose diets had the lowest. Stur
geon fed either the maltose or glucose diets were hyperlipidemic, having twice the amount of plasma total lipid,
triacylglycerol and total cholesterol as fish fed the other
carbohydrate sources. These two carbohydrate sources were
also more lipogenic: maltose- or glucose-fed sturgeon had
significantly higher body lipid and liver G6PDH, malic en
zyme, and ICDH activities. The poor ability of sturgeon to
utilize either sucrose or lactose appears to be due to low
intestinal sucrase (EC 3.2.1.48) and laclase (EC 3.2.1.108)
activities. Intestinal aminopeptidase (EC 3.4.11.11),
maltase (EC 3.2.1.20), sucrase and lactase activities of stur
geon were not affected by feeding different carbohydrate
sources for 8 wk. J. Nutr. 119: 727-733,
1989.
728
HUNG ET AL.
TABLE 1
Formulations of the experimental diets
Ingredient
Amount
Vitamin-free casein
Wheat gluten
Spray-dried egg white
Carbohydrates'
Cellulose
Oil mixture2
Mineral prernix3
Vitamin premix4
'Carbohydrates:
wt%
31.0
15.0
4.0
27.2
3.8
12.0
3.0
4.0
either glucose, maltose, fructose, sucrose, lactose,
sturgeon purified diet used previously [SPD-C, Hung et
al. (11)] except that these diets contained 12.0% of an
oil mixture (cod liver oilicorn oil:lard, 1:1:1) and 0.6%
choline chloride, which has been shown to be adequate
for good growth of juvenile white sturgeon (12). The
eight carbohydrate sources were glucose, fructose, mal
tose, sucrose, lactose, raw corn starch, dextrin and cel
lulose (U.S. Biochemical, Cleveland, OH). Dextrin was
included as a positive control and cellulose as a nega
tive control. Diet mixing, pelleting and storage were
performed as described previously (13). The proximate
compositions of the eight diets as determined by AOAC
methods (14) were similar (data not shown).
There was no observed difference in the palatability
of diets: the time required for sturgeon to complete a
5-g meal of any of the eight diets was within 2 min and
did not differ among different carbohydrate sources.
There should have been no difference in leaching of
water soluble nutrients between diets, because leach
ing from a similar diet was minimal after 2 min in water
(15).
Supply and maintenance of sturgeon. White stur
geon (Acipensei transmontanus]
fingerlings (~ 1400;
body wt, 25 g) were donated by a local producer (The
Fishery, Gait, CA). The fingerlings were transferred to
our facility, gradually weaned from a commercial salmonid diet (Biodiet, Bioproducts, Warrenton, OR) to
our standard purified diet over 2 wk, and fed this pur
ified diet for another month (13). Six hundred fingerlings were randomly transferred to a system of 24 cir
cular fiberglass tanks (three rows with eight tanks per
row) (13) with 25 fish per tank. The fingerlings were
acclimated to the experimental conditions for an ad
throughout the entire trial. The general maintenance
of fish was similar to that described previously (13).
Growth performance. Growth, as measured by the
percent body weight increase, and percent feed effi
ciency were calculated as described previously (16). Four
fish were randomly sampled from each tank at the end
of the experiment. They were pooled, passed through
a meat grinder, freeze-dried for 64 h, and body crude
protein, lipid and ash content were determined (14).
Three groups of four fish each were also sampled from
the stock at the beginning of the study for the initial
body composition estimates. Percent protein deposited
and percent energy retained were calculated as de
scribed previously (16).
Plasma chemistry. Plasma samples were obtained 2
h after the completion of the last feeding cycle and
before the last weighing at 8 wk. Plasma chemistry
values in this study, therefore, should represent values
of fed sturgeon because blood samplings and plasma
preparations (12) were completed 2-6 h after the last
feeding. To minimize a possible time effect on plasma
chemistry, blood was sampled and plasma prepared si
multaneously by three teams. Each team sampled fish
from a single row of eight tanks. A fish was sampled
from each tank in order in each row, with the entire
process being repeated four times.
Plasma glucose, triacylglycerol, and total cholesterol
of individual fish were determined colorimetrically with
an Ektachem DT 60 Analyzer (Eastman Kodak, Roch
ester, NY). Plasma (200 jil) pooled from three of the
four fish was used to determine the nonesterified fatty
acid (NEFA) levels (17). All remaining plasma from the
four fish was pooled and total lipids determined gravimetrically after lipid extraction (18).
Liver lipogenic enzyme activities. One day after the
final weighing, two fish per tank were killed (13) and
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dextrin, raw corn starch or cellulose.
2Oil mixture, consisted of cod liver oilicorn oil:lard (1:1:1).
'Mineral premix BT-m (11).
4Vitamin premix included the following (mg/kg diet): thiamin HC1,
2,000; riboflavin, 200; nicotinic acid, 1,000; D-Ca-pantothenate, 1,200;
pyridoxine HC1, 120; cobalamin (3 mg/g), 40; folie acid, 80; d-biotin
(1%), 2,000; choline chloride, 6000; Hnositol, 4,000; L-ascorbic acid,
1,000; p-aminobenzoic acid, 1,200; retinyl acetate (500,000 lu/g], 80;
cholecalciferol (1%), 280; DL-a-tocopheryl acetate (250 lu/g), 3,000;
menadione, 100; ethoxyquin, 120; BHA, 40.
ditional 2 wk. After acclimation, the fish were weighed
individually and 20 fish retained per tank for the growth
study. Several fish were distributed among different
tanks until the total biomass of fish was similar among
tanks. The average initial weight of fish in the 24 tanks
was 49.8 ±0.5 g (mean ±SEM,n - 24) with the initial
body weight of individual fish ranging from 28.1 to
67.5 g.
The eight diets were randomly assigned within the
24-tank system with each dietary treatment occurring
once per row. Fish were fed 2.0% of their body wt per
day with automatic feeders (13) that dispensed a small
amount of diet over a 24-h period. Fish were weighed
once every 2 wk and the daily ration adjusted accord
ingly. To minimize stress after weighing, feeding was
discontinued for 24 h, except for the final weighing
when feeding was discontinued for only 6 h. The fin
gerlings were also given a static bath containing 10 mg
of active nitrofurazone per liter of water for 1 h after
each weighing to prevent possible bacterial infestations
caused by handling. The growth trial was conducted in
8 wk, and daily water temperature was 19.6 ±0.1 °C
CARBOHYDRATE
UTILIZATION
weighed, and the liver dissected, weighed, freeze-clamped
with liquid nitrogen and stored in an ultralow temper
ature ( - 80°C)freezer. Sturgeon used in these samplings
had been fed for 18 h, and values obtained from these
liver samples should also represent fed sturgeon. Ap
proximately 0.5 g of frozen liver was homogenized us
ing a serrated-tip teflon pestle tissue grinder (30 ml,
Thomas Scientific, Swedesboro, NJ) in 4.5 ml of icecold buffer containing 0.02 M Tris, 5 HIM EDTA, 5mM
MgCl2 0.15 M KC1 and 5 mM mercaptoethanol
(19).
Homogenates were centrifuged at 4°Cand 30,000 x g
frozen in liquid nitrogen
and stored at -80°C. After
thawing, the small and large intestinal brush border
membrane (BBM) vesicles were prepared using methods
described by Buddington and Hilton (24), and aminopeptidase (EC 3.4.11.11) (25), maltase (EC 3.2.1.20), sucrase (EC 3.2.1.48) and lactase (EC 3.2.1.108) activity
determined (26).
Statistical analysis. Data were analyzed with an
MSTAT3 microcomputer software package (27) using
a one-way analysis of variance. Comparisons among
treatments, when appropriate, were made by the Dun
can's multiple range test using the same package. Sta
tistical significance was accepted at P < 0.05.
RESULTS
The percent body wt increase, feed efficiency, protein
deposited and energy retained of sturgeon fed diets with
different carbohydrate sources are given in Table 2. For
mulas used to calculate the above four parameters are
given in the footnotes of Table 2. All four parameters
were significantly affected (P < 0.05) by the dietary car
bohydrate sources. Body moisture, crude protein, crude
fat and ash contents of sturgeon were also significantly
affected by dietary carbohydrate source (data not shown).
The differences in body composition, however, were
small (as seen for moisture and protein) or showed no
definite trends (as seen for ash), except that the body
lipid content of fish fed either maltose (7.3%), glucose
(7.0%) or dextrin (6.3%) were significantly higher than
fish fed the other carbohydrate sources (4.5-5.4%).
There was no significant difference in plasma glucose
regardless of dietary treatment (Table 3), and the plasma
glucose levels in this study were slightly higher than
those of similar size sturgeon after a 48-h fast (72 ±12
Downloaded from jn.nutrition.org by on February 18, 2008
for 30 min. Protein and enzyme activities were meas
ured in the resulting clear supernate. Glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) was as
sayed as described by Clock and McLean (20) and
modified by Kawaga, Kawaga and Shimazoro (21 ).Malic
enzyme (EC 1.1.1.40) was assayed by the method of
Wise and Ball (22). NADP-dependent
isocitrate dehy
drogenase (ICDH, EC 1.1.1.42) was assayed according
to the method of Bernt and Bergmeyer (23). Protein in
the supernate was measured by the Lowry method us
ing a Sigma kit (kit no. P 5656, Sigma Chemical, St.
Louis, MO).
Intestinal brush border enzyme activities. White
sturgeon intestine was separated into the proximal and
distal regions. The proximal region is referred to as the
small intestine, and the distal region with larger di
ameter and spiral valve is referred to as the large in
testine in this report. Two days after the final weighing,
three fish were sampled randomly from each tank, killed
with an overdose of tricaine methanesulfonate
(Argent,
Redmond, WA), and the contents of the small and large
intestine removed by squeezing with a forceps. The
intestines were then cut open and washed with a saline
solution. The mucosa was scraped free with a micro
scope slide, transferred into small plastic vials, quickly
729
BY STURGEON
TABLE 2
Percent body weight increase, feed efficiency, protein deposited and energy retained of sturgeon fed different carbohydrates'
Carbohydrates
Body wt increase2
Feed efficiency'
Protein deposited4
Energy retained5
123.0-11
MaltoseGlucoseStarchDextrinSucroseLactoseFructoseCelluloseSD6208.5"199.3ab180.61*178.7^178.6*159.6"1145.1d94.4'13.4%
8.6-»106.9bc110.3abc110.3abc994ed97.4"185.
7d8.238.0*37.6»36.6"38.0-35.9'33.1-"33.0'b31.0b2.641.3-39.3»30.3"34.4"29.8"23.9C24.6C24.1C2.7
'Values are means of triplicate groups of fish. Means in each column with different superscripts are significantly different (P < 0.05|.
2Percent body wt increase = 100 x (BW, - BWJ/BW,, where BW, and BW, were the average initial and final body wt, respectively.
3Percent feed efficiency = 100 x (BW, - BWJ/TF, where TF = the total amount of diet fed to the fish in a tank/number of fish per tank.
"Percent protein deposited = 100 x [|BW, x BCPJ - (BW, x BCP,)|/(TF x CP), where BCP, and BCP, were initial and final body crude
protein, respectively, and CP was the percent of crude protein in the diet.
5Percent energy retained = 100 x (BEt —BEJ/jTF x dietary energy), where BE, and BE, were the initial and final body energy of sturgeon.
Diet and whole body energy contents were calculated using the following values (kcal/g]: protein, 5.65; fat, 9.40 (33); glucose, fructose and
maltose, 3.75; starch, 4.11; dextrin, 4.23; sucrose, 3.96 |3); lactose, 3.76 (34); and cellulose, 4.17, the value used to calibrate a bomb calorimeter.
6Standard deviation of the dependent variable calculated as the square root of the mean square error term from the analysis of variance.
730
HUNG ET AL.
TABLE 3
Plasma glucose, total lipid, triacylglycerol, total cholesterol and nonesterified
fatty acid ¡NEFA)of sturgeon fed different carbohydrates' -2
CarbohydratesMaltoseGlucoseStarchDextrinSucroseLactoseFructoseCelluloseSD3Glucose10096961009376848114Total
lipid2108"2120"1149b1282"1347b1140b1403"1253b140Triacylglycerol99.445454mg/dlT6"O1'6b8h0>'8"4b5Tota
cholesterol98-10»53<d641»70b49167"50-7NEFAll.l'b11.3
mg/dl, n = 9). Sturgeon fed either maltose or glucose
showed a hyperlipidemia, and their plasma total lipid,
triacylglycerol and total cholesterol were almost twice
that of sturgeon fed the other carbohydrate sources (Table
3). Plasma NEFA levels of sturgeon fed different car
bohydrate sources were also significantly affected by
the dietary carbohydrate, but overlapped among dietary
treatments.
Liver G6PDH, malic enzyme, and ICDH activities of
sturgeon were significantly affected by the dietary car
bohydrate sources (Table 4). Sturgeon fed either mal
tose or glucose had significantly higher G6DPH and
ICDH activities than fish fed the other carbohydrate
sources. The malic enzyme activity of sturgeon fed either
maltose, glucose or dextrin was not significantly dif-
TABLE 4
Glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme,
and NADP-isocitrate dehydrogenase (ICDH} activities of sturgeon
fed different carbohydrates'
Carbohydrates
G6PDH
Malic enzyme
ferent, but was higher than that of sturgeon fed the
other carbohydrate sources.
Aminopeptidase, maltase, sucrase and lactase activ
ities in the small and large intestinal BBM vesicles of
sturgeon fed different carbohydrate sources is given in
Table 5. No statistical analyses were performed on the
small intestine BBM vesicle enzyme activities because
of an accidental loss of the first eight replicate samples.
Activity of the different enzymes in small intestinal
BBM vesicles did not seem to be affected by dietary
treatment. Aminopeptidase, maltase, sucrase and lac
tase activity in the large intestinal BBM vesicles was
also not affected by dietary treatments. The lack of
significant differences among dietary treatments may
have partially resulted from the large variation within
treatments.
There were only six mortalities in the entire growth
trial, and none seemed to be related to the dietary treat
ments. Four mortalities occurred in one replicate group
of sturgeon fed cellulose, and one occurred in each rep
licate group of sturgeon fed either starch or lactose.
ICDH
DISCUSSION
protein321'b337a138e234b120e104«=43'53e51379»416"191b209b190b176b149b143"58
MaltoseGlucoseStarchDextrinSucroseLactoseFructoseCelluloseSD2148»176«69"76"55"45"49b37b33mu/mg
'Values are means from triplicate groups which represent the means
of two fish per replicate, and mu is defined as nmol of NADPH
produced per min. Means in each column with different superscripts
are significantly different (P < 0.05).
2See footnote 6, Table 2.
It is uncertain whether the varying ability of different
species of fish to utilize different carbohydrate sources
results from the methodology or from species differ
ences in the present and previous studies (1-5). The
methodology differences include different dietary for
mulations, water temperatures and feeding strategies.
The species differences include differences in digestion,
absorption, hormonal response, metabolic efficiency,
and gastrointestinal
anatomy and physiology of fish.
Further studies are needed to investigate the cause(s)
of these differences in carbohydrate utilization in dif
ferent species of fish.
Downloaded from jn.nutrition.org by on February 18, 2008
'Values are means of triplicate groups of fish. Means in each column with different superscripts are significantly different (P < 0.05].
2Plasma glucose, triacylglycerol and total cholesterol were determined individually and mean values from four fish were used to represent
a replicate. The NEFA levels were determined from the pooled sample of plasma (200 JJL!|from three fish in each replicate. Plasma total lipid
was determined from the pooled samples of remaining plasma per replicate.
3See footnote 6, Table 2.
CARBOHYDRATE
UTILIZATION
BY STURGEON
731
TABLE 5
Aminopeptidase, maltase, sucrase and ¡actasein the small and ¡argeintestinal brush border
membrane (BBM) vesicle preparations of sturgeon fed different carbohydrates1
Small intestinal BBM vesicles
Large intestinal BBM vesicles
peptidaseMaltaseSucraseLactasemu/mgMaltoseGlucoseStarchDextrinSucroseLactoseFructoseCelluloseSD2938170139120147121110—223190166304214272228198—1614
CarbohydratesAmino
peptidaseMaltaseSucraseLactaseAmino
Among the four growth parameters, percent energy
retained appeared to be the most sensitive index of the
ability of sturgeon to utilize different carbohydrate
sources (Table 2). The greater sensitivity of percent en
ergy retained over the other three parameters resulted
primarily from the greater differences in body lipid in
sturgeon fed different carbohydrate sources. Similar re
sults have been observed in a previous study that com
pared the same growth parameters of sturgeon fed dif
ferent protein sources (16).
The lack of differences in sturgeon plasma glucose
(Table 3) suggests that sturgeon have a well-controlled
glucose homeostasis when fed different carbohydrate
sources under our experimental conditions. This in
dicates that the sturgeon fed cellulose had higher gluconeogenesis and/or lower glycolysis than fish fed the
other carbohydrate sources. Sturgeon fed fructose may
not be able to derive enough glucose from the diet, since
low fructose absorption and conversion to glucose has
been reported for channel catfish (5). Sturgeon fed either
sucrose or lactose may be able to obtain enough glucose
to maintain plasma glucose levels from the digestion
and absorption of these two carbohydrate sources even
though sturgeon have very low sucrase and lactase ac
tivity in the intestinal brush border (Table 5). Alter
natively, sturgeon fed either sucrose, lactose or fructose
may be able to obtain enough glucose from gluconeogenesis, similar to sturgeon fed cellulose, if digestion,
absorption and/or conversion from fructose are low.
Sturgeon fed glucose did not show a higher plasma
glucose level than fish fed either dextrin or starch. This
may have been the result of the continuous nature of
our feeding strategy, which at any given time allowed
only small amounts of glucose to be absorbed. This may
also have resulted from the higher liver glycogen dep
osition (S. Hung, unpublished data) in fish fed glucose.
The hyperlipidemia of sturgeon fed either maltose or
glucose (Table 3) was partially due to higher lipogenesis
as indicated by higher liver lipogenic enzyme activities
(Table 4). It is not clear why either maltose or glucose
feeding would have lipogenic and hyperlipidemic ef
fects in sturgeon, whereas fructose or sucrose feeding
has been shown to be lipogenic and hyperlipidemic in
mammals (6-10).
The lack of lipogenic and hyperlipidemic effects from
lactose, sucrose or fructose feeding may have been the
result of low intestinal lactase and sucrase activity (Table
5) or low uptake of fructose in sturgeon, similar to that
reported in channel catfish (5). The lack of hyperlipi
demic effects of either dextrin or starch feeding may
have resulted from low a-amylase activity similar to
that of rainbow trout (28).
The poor growth response of sturgeon fed either su
crose or lactose is attributable to the lower activity of
sucrase and of lactase in the small intestine. The slightly
better utilization of sucrose when compared to lactose
(Table 2) was attributable to the higher sucrase than
lactase activity. It is uncertain what the importance is
of the greater sucrase activity in the large intestine in
white sturgeon, because the hydrolyzed products of su
crose are absorbed primarily by the small intestine in
most other animals as well as in white sturgeon (29).
Unlike other animals (30), the maltase, sucrase and
lactase activities in sturgeon did not seem to be affected
by the dietary carbohydrate sources (Tables 5), indi
cating that these fish may not be able to adapt to dif
ferent dietary carbohydrate sources.
Growth responses of sturgeon fed either glucose, mal
tose, dextrin or starch were similar to those reported
for chinook salmon (3), except that salmon utilize su-
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'Values for the small intestinal BBM vesicles represent the means of two replicates. Values for the large intestinal BBM vesicles represent
the means of three replicate measurements. Each replicate represents a pooled sample of three fish. No statistical analysis was performed with
the small intestinal BBM vesicle enzyme activity values, and the large intestinal BBM vesicle enzyme activities were not significantly (P >
0.05) affected by the dietary treatments.
2See footnote 6, Table 2.
732
HUNG ET AL.
ACKNOWLEDGMENTS
We wish to thank C. C. Calvert for the valuable sug
gestions during the preparation of this publication. We
also wish to thank The Fishery, Galt, CA, for the do
nation of sturgeon fingerlings, and the Aquaculture and
Fisheries Program, University of California, Davis for
the use of facilities at the Aquatic Center.
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erose better than sturgeon can. The better growth in
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the higher sucrase than maltase activity in these fish,
like rainbow trout (24), whereas the opposite is true in
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Better growth was observed in sturgeon fed either
maltose or glucose than in fish fed dextrin or starch.
Others have reported that common carp (4) and channel
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than fish fed glucose, whereas red sea bream fed these
carbohydrate sources displayed no growth differences
(4). This may reflect inherent species differences or the
different feeding strategies used in these studies. The
continuous nature of our feeding strategy would help
to alleviate the potential problem of hyperglycemia
(Table 3), whereas meal feeding usually resulted in hy
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that rainbow trout can effectively utilize 30% glucose
in a 45% protein diet, but that 30% glucose in a 30%
protein diet had a negative effect on growth and feed
efficiency. Wilson and Poe (5) used a 33.1% carbohy
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produced a diet with an optimum protein:energy ratio.
There is, however, no information on the optimum
levels of different carbohydrate sources, their metabolizable energy values or the optimum protein:energy
ratio in white sturgeon diets. Therefore, the 27.2% car
bohydrate sources, the amount of energy and the pro
tein in our experimental diets may not have been op
timal.
CARBOHYDRATE
UTILIZATION
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