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Utilization of disaccharides by juvenile tilapia, Oreochromis niloticus X O. aureus
ELSEVIER
Aquaculture 133 (1995) 249-256
Utilization of disaccharides by juvenile tilapia, Oreochromis niloticus X 0. aureus Shi-Yen Shiau *, Jei-Cheng Chuang Department
ofMarine Food Science, National Taiwan Ocean University, Keelung, Taiwan 202. ROC Accepted 1 February 1995
Abstract Juvenile tilapia were fed isonitrogenous diets containing 44% maltose, sucrose, lactose, glucose or starch for 8 weeks. Average initial body weight of the fish was 0.80 f 0.05 g. Each diet was fed to 3 groups of 19 fish/aquarium in a recirculating, double-filtered rearing system. Results indicated that weight gain of fish fed the different carbohydrates were starch > maltose > sucrose > lactose > glucose. The differences between each group were significant (P < 0.05). Body lipid content was highest in fish fed the starch diet, followed by those fed the maltose and sucrose diets, then the lactose diet, and was lowest in fish fed the glucose diet. Intestinal disaccharidase activities in tilapia were not affected by the carbohydrates ingested. Plasma glucose concentrations were similar in fish fed the disaccharide and starch diets and were lower than those in fish fed the glucose diet. The data suggest that tilapia utilizes disaccharides better than glucose but more poorly than starch. Of the disaccharides, maltose was better utilized, followed by sucrose and lactose. Keywords: Oreochromis
spp.; Feeding and nutrition-fish;
Disaccharides;
Carbohydrates
1. Introduction Carbohydrates are the least expensive form of dietary energy for man and domestic animals, but their utilization by fish varies and remains somewhat obscure. Buhler and Halver ( 196 1) fed chinook salmon with different carbohydrates and found that growth rate decreased with increasing carbohydrate molecular weight. McCartney ( 1971) fed brook trout diets containing glucose, galactose or fructose and found glucose was the best utilized. Bergot (1979) fed 15 or 30% of glucose or starch to rainbow trout and found that 30% glucose was utilized best. * Corresponding
author. Tel. (886-2)
462-2192,
ext. 5106; Fax (886-2)
0044-8486/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIOO44-84860044-8486(95)00018-6
462-1684
250
S.-Y. Shiau, J.-C. Chuang/Aquaculture
133 (1995) 249-256
However, other studies have failed to demonstrate the same trend of carbohydrate utilization by fish. Furuichi and Yone (1982a) fed carp and red sea bream diets containing glucose, dextrin or starch and found that growth and feed efficiency were highest when they were fed starch, followed by dextrin and glucose. Red sea bream showed higher feed efficiency when fed the starch diet than when fed the dextrin and glucose diets. Furuichi et al. ( 1986) have shown that starch was better utilized than glucose by the yellowtail. There is a paucity of information on disaccharide utilization by fish, except for channel catfish (Wilson and Poe, 1987) and white sturgeon (Hung et al., 1989; Hung, 1991). Channel catfish were unable to utilize mono- and disaccharides efficiently, whereas white sturgeon utilized glucose and maltose more efficiently than fructose, sucrose, lactose, dextrin and starch. In our previous studies, we demonstrated that tilapia utilized starch better than glucose (Tung and Shiau, 1991; Shiau and Chen, 1993; Shiau and Lin, 1993; ). Adaptive responses of intestinal disaccharidase activities to dietary carbohydrate have been well documented in mammals (Blair et al., 1963; Deren et al., 1967; Kimura et al., 1978; Bustamante et al., 1981), but little is known of this response in fish. The purpose of this experiment was to study the utilization of disaccharides by tilapia, Oreochromis niloticus X 0. uureus and their effect on intestinal disaccharidase activities. Glucose and starch were also included in the study for comparison. 2. Materials and methods Diet preparation Five carbohydrate sources, D- ( + )-glucose, maltose, sucrose, lactose and raw cornstarch (Sigma Chemical, St Louis, MO) were used in the study. The composition and proximate analysis ( AOAC, 1984) of the experimental diets are given in Table 1. This formulation is Table 1 Composition
of the experimental
Ingredient
diets (% dry wt) Diet Glucose
Maltose
sucrose
Lactose
Starch
Common ingredients’ Glucose Maltose
56 44
56 _ 44
56
56 _
56
Surcose Lactose Starch
_ _
_
44
_
Analysis Moisture Ash Crude protein Crude fat
_ 44
_ 44
6.80 4.23 30.11 9.60
4.80 4.53 30.72 9.87
3.31 4.13 30.47 8.19
3.94 4.12 29.12 8.70
6.02 4.13 33.70 9.11
‘Common ingredients contained: fish meal (Norsemink, Norwegian Herring Oil and Meat Industries, Bergen, Norway), 40; corn oil, 8.5; carboxymethyl cellulose, 2; vitamin mix *, 1.5; mineral mix3, 4. ‘According to Tung and Shiau ( 199 1) ‘According to Shiau and Suen ( 1992).
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133 (1995) 249-256
251
similar to that of Tung and Shiau (1993) in which 44% of carbohydrate was used in the diet for tilapia. The diets were prepared and handled as described by Shiau et al. ( 1988). Supply and maintenance
of tilapia
Hybrid male tilapia, Oreochromis niloticus X 0. aureus, were obtained from a commercial hatchery (Far East Hatchery Co. Cha-Yi, Taiwan) and acclimated to our laboratory conditions for 4 weeks in a plastic tank (74 W X 95 L X 45 H cm). During this period they were fed a commercial feed (Luck Star, Hung Kuo Industrial Co., Taipei, Taiwan). At the beginning of the experiment, 15 glass aquaria (30.5 W X 61 .O L X 55.5 H cm) were each stocked with 19 fish with an average weight of 0.80 + 0.05 g. Each experimental diet was fed to fish in 3 aquaria. Each aquarium was part of a closed-recirculated system with a common water reservoir maintained at 26 Ifr 1°C. The operation of the rearing system was similar to that of a previous study (Shiau and Suen, 1992). The fish were fed their respective diets at a rate of 5% of body weight per day with the feed divided into two feedings (08.00 and 17.00 h) . The fish were weighed every 2 weeks and the amount of diet fed was adjusted accordingly, The duration of the study was 8 weeks. Growth pelformance
Growth, as measured by the percent body weight increase, feed conversion ratio (FCR) and protein efficiency ratio (PER) were calculated as described previously (Shiau et al., 1990). Percent protein deposited was calculated as described previously (Shiau and Peng, 1993). Two fish were randomly sampled from each aquarium at the end of the experiment. They were pooled, ground and freeze-dried, and body crude protein, lipid, moisture and ash content determined according to AOAC methods ( 1984). Intestinal enzyme activities
Two days after the final weighing, 3 fish were sampled from each aquarium, killed as described by Tung and Shiau ( 199 1) , and the contents of the intestine removed by squeezing with a forcep. The intestines were then cut open and washed with a saline solution. The mucosa was scraped free with a microscope slide, transferred to small plastic vials, frozen in liquid nitrogen and stored at - 80°C. After thawing, the intestinal brush border membrane (BBM) vesicles were prepared using methods described by Buddington and Hilton ( 1988). Maltase (EC 3.2.1.20), sucrase (EC 3.2.1.48) and lactase (EC 3.2.1.108) activities were determined according to Conklin et al. ( 1975). Protein was determined by the method of Lowry et al. ( 195 1) Plasma glucose concentration
The remaining fish were starved for 24 h; then 2 fish were removed from each aquarium. Blood was sampled from the caudal vein and pooled to represent 0 h. Each test diet was then fed (half of the daily ration), thereafter to the fish in each aquarium and 2 fish were taken randomly at 1, 2, 3,4, 6 and 8 h after feeding for blood collection. The fish were not re-used after their blood had been sampled. Blood glucose determination of the fish was as described previously (Shiau and Suen, 1992).
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133 (1995) 249-256
Statistical analysis Data were subjected to one-way analysis of variance using the SAS/PC statistical software (SAS Institute, Cary, NC) to determine statistical significance. Multiple comparisons among means were made with Duncan’s new multiple range test with the same SAS/PC program. Statistical significance was determined by setting the aggregate type I error at 5% (P < 0.05) for each set of comparisons. Estimated areas under the plasma glucose curves in fish fed each carbohydrate diet were analyzed by Student’s t-test as performed in the previous study (Shiau and Suen, 1992).
3. Results Weight gain, feed conversion ratio (FCR) , protein efficiency ratio (PER) and protein deposition (PD) of tilapia fed the different carbohydrate diets are presented in Table 2. Highest weight gain was observed in fish fed the starch diet, followed by those fed the maltose, sucrose, lactose and glucose diets. The differences among the 5 groups were significant (P < 0.05). Feed conversion ratio, PER and PD of fish fed the test diets followed the same general pattern as weight gain. No mortality was observed in any of the groups during the study. Body lipid and moisture were significantly affected by the dietary treatment (Table 3). Body lipid was highest in fish fed the starch diet, followed by those fed the maltose and sucrose diets, then the lactose diet, and finally the glucose diet. Moisture content was highest for fish fed the glucose diet, followed by those fed the lactose diet, then the maltose and sucrose diets, and finally the starch diet. Protein and ash were unaffected by the different carbohydrate diets. Fish fed the 5 carbohydrate diets had similar (P > 0.05) intestinal maltase, sucrase and lactase activities (Table 4). Plasma glucose concentrations of tilapia fed diets containing the different carbohydrate sources are illustrated in Fig. 1. Plasma glucose concentrations were similar in fish fed diets Table 2 Growth performance
of tilapia fed different carbohydrate
diets for 8 weeks’
Carbohydrate
Weight gait? (%)
FCR3
PER4
PDS (%)
Glucose Maltose Sucrose Lactose Starch Pooled s.e.d.6
1oo.438 229.89’ 184.11” 161.52b 426.74e 11.20
4.11e 2.11b 2.61” 2.93d 1.49& 0.15
0.82” 1.54’ 1.27bf 1.15b 2.03’ 0.10
14.13a 24.04’ 21.79bc 20.46b 35.67d 1.36
‘Values are means from 3 groups of fish with 19 fish per group. Different superscripts indicate significant (P < 0.05 ) differences between fish fed carbohydrate diets. ‘Weight gain (%) = 100 X (SW,- BW,) /BW,, where BW, and BWr are average initial and final body weight (BW), respectively. The initial BW of these fish was 0.80 f 0.05 g (mean f s.d.). 3Feed conversion ratio (FCR) = FI/(BWr-BW,), where FI is the total feed intake. 4Protein efficiency ratio (PER) = (BWr-BW,)/PI, where. PI is the total protein intake. ‘Protein deposition (PD) (%) = 100 X (BWr X BCP, - BW, X BCP,)/(FI X CP,,),whereBCP,,BCP,andCP,areinitialbody protein, final body protein, and dietary protein, respectively. 6s.e.d. = standard error of the difference.
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133 (1995) 249-256
253
Table 3 Body composition
(%) of tilapia fed different carbohydrate
diets for 8 weeks’
Carbohydrate
Moisture
Protein
Lipid
Ash
Glucose Maltose Sucrose Lactose Starch Pooled s.e.d.’
72.60’ 68.95b 69.48b 70.02’ 67.84a 1.01
15.34 15.53 15.63 15.97 15.54 0.32
5.28” 7.29” 7.33’ 6.31b 9.536 0.27
5.38 4.89 4.48 5.20 4.80 0.33
‘Values are means from 3 aquaria with a single determination of a sample pooled from 2 fish per aquarium for moisture, protein, lipid and ash. Different superscripts indicate significant (P< 0.05) differences between fish fed carbohydrate diets. ‘s.e.d. = standard error of the difference.
140
120 -
0
1
2
3
Time
4
0
Glucose
0
Maltose
5
6
7
6
(hr)
Fig. 1. Plasma glucose concentration of tilapia fed various diets. Each datum point represents 3 groups of 2 fish per aquarium (n = 3) Blood was collected from fish starved for 24 h and pooled to represent 0 h. Each test diet was fed to the fish in each aquarium and 2 fish were taken randomly at 1,2,3,4,6 and 8 h after feeding for blood collection. The average estimated area under the curves for the fish fed the glucose diet was significantly higher (P < 0.05) than the average estimated area under the curves for fish fed the other carbohydrate diets.
maltose, sucrose, lactose or starch and all these values were lower (P < 0.05) than in fish fed the glucose diet. In fish fed the glucose diet, plasma glucose concentration peaked at 2 h after feeding. In fish fed maltose, lactose and starch diets the plasma glucose concentration peaked at 3 h after feeding, and in those fed the sucrose diet the plasma glucose concentration peaked at 4 h after feeding. containing
254
S.-Y. Shiau, J.-C. Chuang/Aquaculture
Table 4 Specific and segmental diets for 8 weeks’** Carbohydrate
Glucose Maltose Sucrose Lactose Starch Pooled s.e.d.3
activities
133 (1995) 249-256
of intestinal maltase, sucrase and lactase in tilapia fed different carbohydrate
Mahase
Sucrase
Lactase
Specific
Segmental
Specific
Segmental
Specific
Segmental
29.77 39.84 38.27 32.74 38.12 10.11
31.75 26.24 31.97 25.52 25.39 9.48
5.78 5.19 5.66 5.69 4.22 1.36
6.17 5.41 4.73 4.35 4.01 1.21
1.69 1.36 1.02 1.25 1.50 0.27
1.40 0.92 0.93 0.98 0.89 0.24
‘Values represent the means of 3 replicate measurements. Each replicate represents a pooled sample of 3 fish. All three enzyme activities were not significantly (P> 0.05) affected by the dietary treatments. 2Maltase, sucrase, lactase activities are expressed as X 1000 units/mg protein or activity per cm of intestine. One unit equals to 1 pm01 of disaccharides hydrolyzed per min. %.e.d. = standard error of the difference.
4. Discussion Our study clearly demonstrated that utilization of disaccharides by tilapia was higher than glucose but lower than starch. Maltose was better utilized among the 3 disaccharides followed by sucrose and it was least by lactose. The efficient utilization of disaccharides in tilapia may possibly be attributed to the different intestinal disaccharidase activities (Table 4). Greater growth of tilapia in the starch-fed group than in the glucose-fed group are in accordance with previous findings (Tung and Shiau, 1991; Shiau and Lin, 1993; Shiau and Chen, 1993). The reason for poor glucose utilization by fish is still not clear. It has been hypothesized that glucose is rapidly absorbed in the gut (Pieper and Pfeffer, 1980). The rapid absorption of glucose would mean that considerable amounts of glucose enter the body before sufficient elevation of the activities of carbohydrate metabolic enzymes. This in turn could possibly restrict the use of the absorbed glucose (Furuichi and Yone, 1982b). Intestinal disaccharidase activity is often expressed as micromoles of substrate hydrolyzed per minute per gram of tissue protein (specific activity). Because specific activity is a ratio of total enzyme activity to tissue protein content, changes in specific activity can result from changes in the numerator and/or the denominator. Changes in mucosal protein content may in fact have no relation to changes in disaccharidase activity (Koldovsky et al., 1982). Therefore, it may be more appropriate to express the disaccharidase activities in the segments as segmental activity, i.e. activity per unit length of the intestine. This removes the possibility of any artifact when disaccharidase activity is related to tissue protein content and more accurately reflects true functional activity. In the present study, when segmental activity of disaccharidases of each dietary group calculated, values of 25.39-3 1.75 (maltase) ,4.016.17 (sucrase) and 0.89-l .40 (lactase) mol of hydrolyzed disaccharide X 103/cm intestine were obtained. There was no difference (P > 0.05) in each enzyme activity due to the different carbohydrates ingested. There are several unclear points that remain to be investigated. Hung et al. ( 1989) reported that intestinal maltase, sucrase, and lactase activities of sturgeon were not affected
S.-Y. Shim, J.-C. Chuang/Aquaculture
133 (1995) 249-256
255
by feeding different carbohydrate sources. However, the results obtained from sturgeon were quite different from our data with tilapia. In sturgeon, glucose and maltose were best utilized. Maltose, sucrose and lactose were observed in the plasma of sturgeon when they were fed diets containing maltose, sucrose and lactose, respectively (Hung, 1991). It was suggested by the author that disaccharides may diffuse passively through the cells or through the cell-to-cell junctions in the sturgeon gastrointestinal mucosa. Higher body fat in fish fed the starch diet than those fed the glucose diet in the present study is in agreement with previous studies (Shiau and Lin, 1993; Shiau and Chen, 1993). Fish fed the disaccharide-containing diets had intermediate levels of body fat. The lack of a lipogenic effect in sturgeon fed diets containing lactose or sucrose has been attributed to low intestinal lactase and sucrase activities (Hung et al., 1989). Similarly, relatively low intestinal lactase activity was observed in this study with tilapia. Body fat in the fish fed the maltose and sucrose diets was similar (Table 3). The storage of body fat is an indication of carbohydrate utilization. The lipogenic enzymes were not measured in the present study. Studies are necessary to elucidate the lipogenic pathways in fish fed disaccharides.
Acknowledgements This work was supported by a grant from the National Science Council of the Republic of China, grant number NSC 84-232 1-B-019-001.
References AOAC (Association of Official Analytical Chemists), 1984. W. Horwitz (Editor), Official Methods of Analysis, 14th edn. Washington, DC, 1018 pp. Bergot, F., 1979. Carbohydrate in rainbow trout diets: effect of the level and source of carbohydrate and number of meals on growth and body composition. Aquaculture, 18: 157-167. Blair, D.G.R., Yakimets, W. and Tuba, J., 1963. Rat intestinal sucrase. Il. The effects of rat age sex and of diet on sucrase activity. Can. J. Biochem. Physiol., 41: 917-929. Buddington, R.K. and Hilton, J.W., 1988. Intestinal adaptations ofrainbow trout to changes in dietary carbohydrate. Am. J. Physiol., 253: G489-G496. Buhler, D.R. and Halver, J.E., 1961. Nutrition of salmonoid fish. IX. Carbohydrate requirements of chinook salmon. J. Nutr., 74: 307-318. Bustamante, S., Gasparo, M., Kendall, K., Coates, P., Brown, S., Somawane, B. and Koldovsky, 0.. 198 1. Increased activity of rat intestinal lactase due to increased intake of cr-saccharides (starch, sucrose) in isocaloric diets. J. Nutr., 111: 943-953. Conklin, K.A., Yamashiro, K.M. and Gray, G.M., 1975. Human intestinal sucrase-isomaltase. J. Biol. Chem., 250: 5735-5741. Deren, J.J., Broitman, S.A. and Zamcheck, N., 1967. Effect ofdiet upon intestinal disaccharidase and disaccharide absorption J. Clin. Invest., 46: 186-195. Furuichi, M. and Yone, Y., 1982a. Availability of carbohydrate in nutrition of carp and red sea bream. Bull. Jpn. Sot. Sci. Fish., 48: 945-948. Furuichi, M. and Yone, Y., 1982b. Change in activities of hepatic enzymes related to carbohydrate metabolism of fishes in glucose and insulin-glucose tolerance tests. Bull. Jpn. Sot. Sci. Fish., 48: 463-466. Furuichi, M., Taira, H. and Yone, Y., 1986. Availability of carbohydrate in nutrition of yellowtail. Bull. Jpn. Sot. Sci. Fish.. 52: 99-102.
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Hung, S.S.O., 1991. Carbohydrate utilization by white sturgeon as assessed by oral administration tests. J. Nutr., 121: 1600-1605. Hung, S.S.O., Fynn-A&ins, K.F., Lutes, P.B. and Xu, R.P., 1989. Ability of juvenile white sturgeon (Acipenser transmontanus) to utilize different carbohydrate sources. J. Nutr., 119: 727-733. Kimura, T., Seto, A. and Yoshida, A., 1978. Effect of diets on intestinal disaccharidase and leucine aminopeptidase activities in refed rats. J. Nutr., 108: 1087-1097. Koldovsky, 0.. Bustamante, S. and Yamada, K., 1982. Adaptability of lactase and sucrase activity in jejunoileum of adult rats to changes in intake of starch, sucrose, lactose, glucose, fructose and galactose. In: J.W.L. Robinson, R.H. Dowling and E.O. Riecken (Editors), Mechanism of Intestinal Adaptation. MTP Press Ltd., Lancaster, pp. 153-168. Lowry, O.H., Rosebrough, NJ., Farr, A.L. and Randall, R.J., 1951. Protein measurement with the Folin phenol reagent. J. Biol. Chem., 193: 365-375. McCartney, T.H., 1971. The comparative utilization of glucose, fructose, and galactose by fingerling brook trout. State NY Conserv. Dept. Fish. Res. Bull., 39: 43-52. Pieper, A. and Pfeffer, E., 1980. Studies on the comparative efficiency of utilization of gross energy from some carbohydrates, protein and fats by rainbow trout (Salmo gairdneri R. ) Aquaculture, 20: 323-332. Shiau, S.Y. and Chen, M.J., 1993. Carbohydrate utilization by tilapia (Oreochromis niloticus X 0. aureus) as influenced by different chromium sources. J. Nutr., 123: 1747-1753. Shiau, S.Y. and Lin, SF., 1993. Effect of supplemental dietary chromium and vanadium on the utilization of different carbohydrates in tilapia, Oreochromis niloticus X 0. aureus. Aquaculture, 110: 321-330. Shiau, S.Y. and Peng, C.Y., 1993. Protein-sparingeffectby carbohydratesindiets fortilapia, Oreochromisniloticus X 0. aureus. Aquaculture, 117: 327-334. Shiau, S.Y. and Suen, G.S., 1992. Estimation of the niacin requirements for tilapia fed diets containing glucose or dextrin. J. Nutr., 122: 2030-2036. Shiau, S.Y., Yu, S.L., Hwa, S., Chen, S.Y. and Hsu, S.I., 1988. The influence of carboxymethylcellulose on growth, digestion, gastric emptying time and body composition of tilapia. Aquaculture, 70: 345-354. Shiau, S.Y., Lin, S.F., Yu, S.L., Lin, A.L. and Kwok, C.C., 1990. Defatted and full-fat soybean meal as partial replacements for fishmeal in tilapia (Oreochromis niloticus X 0. uureus) diets at low protein level. Aquaculture, 86: 401-407. Tung, P.H. and Shiau, S.Y., 1991. Effects of meal frequency on growth performance of hybrid tilapia, Oreochromis niloticus X 0. aureus, fed different carbohydrate diets. Aquaculture, 92: 343-350. Tung, P.H. and Shiau, S.Y., 1993. Carbohydrate utilization versus body size in tilapia, Oreochromis niloticus X 0. aureus. Comp. Biochem. Physiol., 104A: 585-588. Wilson, R.P. and Poe, W.E., 1987. Apparent inability of channel catfish to utilize dietary mono- and disaccharides as energy source. J. Nutr., 117: 280-285.
Aquaculture 133 (1995) 249-256
Utilization of disaccharides by juvenile tilapia, Oreochromis niloticus X 0. aureus Shi-Yen Shiau *, Jei-Cheng Chuang Department
ofMarine Food Science, National Taiwan Ocean University, Keelung, Taiwan 202. ROC Accepted 1 February 1995
Abstract Juvenile tilapia were fed isonitrogenous diets containing 44% maltose, sucrose, lactose, glucose or starch for 8 weeks. Average initial body weight of the fish was 0.80 f 0.05 g. Each diet was fed to 3 groups of 19 fish/aquarium in a recirculating, double-filtered rearing system. Results indicated that weight gain of fish fed the different carbohydrates were starch > maltose > sucrose > lactose > glucose. The differences between each group were significant (P < 0.05). Body lipid content was highest in fish fed the starch diet, followed by those fed the maltose and sucrose diets, then the lactose diet, and was lowest in fish fed the glucose diet. Intestinal disaccharidase activities in tilapia were not affected by the carbohydrates ingested. Plasma glucose concentrations were similar in fish fed the disaccharide and starch diets and were lower than those in fish fed the glucose diet. The data suggest that tilapia utilizes disaccharides better than glucose but more poorly than starch. Of the disaccharides, maltose was better utilized, followed by sucrose and lactose. Keywords: Oreochromis
spp.; Feeding and nutrition-fish;
Disaccharides;
Carbohydrates
1. Introduction Carbohydrates are the least expensive form of dietary energy for man and domestic animals, but their utilization by fish varies and remains somewhat obscure. Buhler and Halver ( 196 1) fed chinook salmon with different carbohydrates and found that growth rate decreased with increasing carbohydrate molecular weight. McCartney ( 1971) fed brook trout diets containing glucose, galactose or fructose and found glucose was the best utilized. Bergot (1979) fed 15 or 30% of glucose or starch to rainbow trout and found that 30% glucose was utilized best. * Corresponding
author. Tel. (886-2)
462-2192,
ext. 5106; Fax (886-2)
0044-8486/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIOO44-84860044-8486(95)00018-6
462-1684
250
S.-Y. Shiau, J.-C. Chuang/Aquaculture
133 (1995) 249-256
However, other studies have failed to demonstrate the same trend of carbohydrate utilization by fish. Furuichi and Yone (1982a) fed carp and red sea bream diets containing glucose, dextrin or starch and found that growth and feed efficiency were highest when they were fed starch, followed by dextrin and glucose. Red sea bream showed higher feed efficiency when fed the starch diet than when fed the dextrin and glucose diets. Furuichi et al. ( 1986) have shown that starch was better utilized than glucose by the yellowtail. There is a paucity of information on disaccharide utilization by fish, except for channel catfish (Wilson and Poe, 1987) and white sturgeon (Hung et al., 1989; Hung, 1991). Channel catfish were unable to utilize mono- and disaccharides efficiently, whereas white sturgeon utilized glucose and maltose more efficiently than fructose, sucrose, lactose, dextrin and starch. In our previous studies, we demonstrated that tilapia utilized starch better than glucose (Tung and Shiau, 1991; Shiau and Chen, 1993; Shiau and Lin, 1993; ). Adaptive responses of intestinal disaccharidase activities to dietary carbohydrate have been well documented in mammals (Blair et al., 1963; Deren et al., 1967; Kimura et al., 1978; Bustamante et al., 1981), but little is known of this response in fish. The purpose of this experiment was to study the utilization of disaccharides by tilapia, Oreochromis niloticus X 0. uureus and their effect on intestinal disaccharidase activities. Glucose and starch were also included in the study for comparison. 2. Materials and methods Diet preparation Five carbohydrate sources, D- ( + )-glucose, maltose, sucrose, lactose and raw cornstarch (Sigma Chemical, St Louis, MO) were used in the study. The composition and proximate analysis ( AOAC, 1984) of the experimental diets are given in Table 1. This formulation is Table 1 Composition
of the experimental
Ingredient
diets (% dry wt) Diet Glucose
Maltose
sucrose
Lactose
Starch
Common ingredients’ Glucose Maltose
56 44
56 _ 44
56
56 _
56
Surcose Lactose Starch
_ _
_
44
_
Analysis Moisture Ash Crude protein Crude fat
_ 44
_ 44
6.80 4.23 30.11 9.60
4.80 4.53 30.72 9.87
3.31 4.13 30.47 8.19
3.94 4.12 29.12 8.70
6.02 4.13 33.70 9.11
‘Common ingredients contained: fish meal (Norsemink, Norwegian Herring Oil and Meat Industries, Bergen, Norway), 40; corn oil, 8.5; carboxymethyl cellulose, 2; vitamin mix *, 1.5; mineral mix3, 4. ‘According to Tung and Shiau ( 199 1) ‘According to Shiau and Suen ( 1992).
S.-Y. Shiau, J.-C. Chuang/Aquaculture
133 (1995) 249-256
251
similar to that of Tung and Shiau (1993) in which 44% of carbohydrate was used in the diet for tilapia. The diets were prepared and handled as described by Shiau et al. ( 1988). Supply and maintenance
of tilapia
Hybrid male tilapia, Oreochromis niloticus X 0. aureus, were obtained from a commercial hatchery (Far East Hatchery Co. Cha-Yi, Taiwan) and acclimated to our laboratory conditions for 4 weeks in a plastic tank (74 W X 95 L X 45 H cm). During this period they were fed a commercial feed (Luck Star, Hung Kuo Industrial Co., Taipei, Taiwan). At the beginning of the experiment, 15 glass aquaria (30.5 W X 61 .O L X 55.5 H cm) were each stocked with 19 fish with an average weight of 0.80 + 0.05 g. Each experimental diet was fed to fish in 3 aquaria. Each aquarium was part of a closed-recirculated system with a common water reservoir maintained at 26 Ifr 1°C. The operation of the rearing system was similar to that of a previous study (Shiau and Suen, 1992). The fish were fed their respective diets at a rate of 5% of body weight per day with the feed divided into two feedings (08.00 and 17.00 h) . The fish were weighed every 2 weeks and the amount of diet fed was adjusted accordingly, The duration of the study was 8 weeks. Growth pelformance
Growth, as measured by the percent body weight increase, feed conversion ratio (FCR) and protein efficiency ratio (PER) were calculated as described previously (Shiau et al., 1990). Percent protein deposited was calculated as described previously (Shiau and Peng, 1993). Two fish were randomly sampled from each aquarium at the end of the experiment. They were pooled, ground and freeze-dried, and body crude protein, lipid, moisture and ash content determined according to AOAC methods ( 1984). Intestinal enzyme activities
Two days after the final weighing, 3 fish were sampled from each aquarium, killed as described by Tung and Shiau ( 199 1) , and the contents of the intestine removed by squeezing with a forcep. The intestines were then cut open and washed with a saline solution. The mucosa was scraped free with a microscope slide, transferred to small plastic vials, frozen in liquid nitrogen and stored at - 80°C. After thawing, the intestinal brush border membrane (BBM) vesicles were prepared using methods described by Buddington and Hilton ( 1988). Maltase (EC 3.2.1.20), sucrase (EC 3.2.1.48) and lactase (EC 3.2.1.108) activities were determined according to Conklin et al. ( 1975). Protein was determined by the method of Lowry et al. ( 195 1) Plasma glucose concentration
The remaining fish were starved for 24 h; then 2 fish were removed from each aquarium. Blood was sampled from the caudal vein and pooled to represent 0 h. Each test diet was then fed (half of the daily ration), thereafter to the fish in each aquarium and 2 fish were taken randomly at 1, 2, 3,4, 6 and 8 h after feeding for blood collection. The fish were not re-used after their blood had been sampled. Blood glucose determination of the fish was as described previously (Shiau and Suen, 1992).
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Statistical analysis Data were subjected to one-way analysis of variance using the SAS/PC statistical software (SAS Institute, Cary, NC) to determine statistical significance. Multiple comparisons among means were made with Duncan’s new multiple range test with the same SAS/PC program. Statistical significance was determined by setting the aggregate type I error at 5% (P < 0.05) for each set of comparisons. Estimated areas under the plasma glucose curves in fish fed each carbohydrate diet were analyzed by Student’s t-test as performed in the previous study (Shiau and Suen, 1992).
3. Results Weight gain, feed conversion ratio (FCR) , protein efficiency ratio (PER) and protein deposition (PD) of tilapia fed the different carbohydrate diets are presented in Table 2. Highest weight gain was observed in fish fed the starch diet, followed by those fed the maltose, sucrose, lactose and glucose diets. The differences among the 5 groups were significant (P < 0.05). Feed conversion ratio, PER and PD of fish fed the test diets followed the same general pattern as weight gain. No mortality was observed in any of the groups during the study. Body lipid and moisture were significantly affected by the dietary treatment (Table 3). Body lipid was highest in fish fed the starch diet, followed by those fed the maltose and sucrose diets, then the lactose diet, and finally the glucose diet. Moisture content was highest for fish fed the glucose diet, followed by those fed the lactose diet, then the maltose and sucrose diets, and finally the starch diet. Protein and ash were unaffected by the different carbohydrate diets. Fish fed the 5 carbohydrate diets had similar (P > 0.05) intestinal maltase, sucrase and lactase activities (Table 4). Plasma glucose concentrations of tilapia fed diets containing the different carbohydrate sources are illustrated in Fig. 1. Plasma glucose concentrations were similar in fish fed diets Table 2 Growth performance
of tilapia fed different carbohydrate
diets for 8 weeks’
Carbohydrate
Weight gait? (%)
FCR3
PER4
PDS (%)
Glucose Maltose Sucrose Lactose Starch Pooled s.e.d.6
1oo.438 229.89’ 184.11” 161.52b 426.74e 11.20
4.11e 2.11b 2.61” 2.93d 1.49& 0.15
0.82” 1.54’ 1.27bf 1.15b 2.03’ 0.10
14.13a 24.04’ 21.79bc 20.46b 35.67d 1.36
‘Values are means from 3 groups of fish with 19 fish per group. Different superscripts indicate significant (P < 0.05 ) differences between fish fed carbohydrate diets. ‘Weight gain (%) = 100 X (SW,- BW,) /BW,, where BW, and BWr are average initial and final body weight (BW), respectively. The initial BW of these fish was 0.80 f 0.05 g (mean f s.d.). 3Feed conversion ratio (FCR) = FI/(BWr-BW,), where FI is the total feed intake. 4Protein efficiency ratio (PER) = (BWr-BW,)/PI, where. PI is the total protein intake. ‘Protein deposition (PD) (%) = 100 X (BWr X BCP, - BW, X BCP,)/(FI X CP,,),whereBCP,,BCP,andCP,areinitialbody protein, final body protein, and dietary protein, respectively. 6s.e.d. = standard error of the difference.
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Table 3 Body composition
(%) of tilapia fed different carbohydrate
diets for 8 weeks’
Carbohydrate
Moisture
Protein
Lipid
Ash
Glucose Maltose Sucrose Lactose Starch Pooled s.e.d.’
72.60’ 68.95b 69.48b 70.02’ 67.84a 1.01
15.34 15.53 15.63 15.97 15.54 0.32
5.28” 7.29” 7.33’ 6.31b 9.536 0.27
5.38 4.89 4.48 5.20 4.80 0.33
‘Values are means from 3 aquaria with a single determination of a sample pooled from 2 fish per aquarium for moisture, protein, lipid and ash. Different superscripts indicate significant (P< 0.05) differences between fish fed carbohydrate diets. ‘s.e.d. = standard error of the difference.
140
120 -
0
1
2
3
Time
4
0
Glucose
0
Maltose
5
6
7
6
(hr)
Fig. 1. Plasma glucose concentration of tilapia fed various diets. Each datum point represents 3 groups of 2 fish per aquarium (n = 3) Blood was collected from fish starved for 24 h and pooled to represent 0 h. Each test diet was fed to the fish in each aquarium and 2 fish were taken randomly at 1,2,3,4,6 and 8 h after feeding for blood collection. The average estimated area under the curves for the fish fed the glucose diet was significantly higher (P < 0.05) than the average estimated area under the curves for fish fed the other carbohydrate diets.
maltose, sucrose, lactose or starch and all these values were lower (P < 0.05) than in fish fed the glucose diet. In fish fed the glucose diet, plasma glucose concentration peaked at 2 h after feeding. In fish fed maltose, lactose and starch diets the plasma glucose concentration peaked at 3 h after feeding, and in those fed the sucrose diet the plasma glucose concentration peaked at 4 h after feeding. containing
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Table 4 Specific and segmental diets for 8 weeks’** Carbohydrate
Glucose Maltose Sucrose Lactose Starch Pooled s.e.d.3
activities
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of intestinal maltase, sucrase and lactase in tilapia fed different carbohydrate
Mahase
Sucrase
Lactase
Specific
Segmental
Specific
Segmental
Specific
Segmental
29.77 39.84 38.27 32.74 38.12 10.11
31.75 26.24 31.97 25.52 25.39 9.48
5.78 5.19 5.66 5.69 4.22 1.36
6.17 5.41 4.73 4.35 4.01 1.21
1.69 1.36 1.02 1.25 1.50 0.27
1.40 0.92 0.93 0.98 0.89 0.24
‘Values represent the means of 3 replicate measurements. Each replicate represents a pooled sample of 3 fish. All three enzyme activities were not significantly (P> 0.05) affected by the dietary treatments. 2Maltase, sucrase, lactase activities are expressed as X 1000 units/mg protein or activity per cm of intestine. One unit equals to 1 pm01 of disaccharides hydrolyzed per min. %.e.d. = standard error of the difference.
4. Discussion Our study clearly demonstrated that utilization of disaccharides by tilapia was higher than glucose but lower than starch. Maltose was better utilized among the 3 disaccharides followed by sucrose and it was least by lactose. The efficient utilization of disaccharides in tilapia may possibly be attributed to the different intestinal disaccharidase activities (Table 4). Greater growth of tilapia in the starch-fed group than in the glucose-fed group are in accordance with previous findings (Tung and Shiau, 1991; Shiau and Lin, 1993; Shiau and Chen, 1993). The reason for poor glucose utilization by fish is still not clear. It has been hypothesized that glucose is rapidly absorbed in the gut (Pieper and Pfeffer, 1980). The rapid absorption of glucose would mean that considerable amounts of glucose enter the body before sufficient elevation of the activities of carbohydrate metabolic enzymes. This in turn could possibly restrict the use of the absorbed glucose (Furuichi and Yone, 1982b). Intestinal disaccharidase activity is often expressed as micromoles of substrate hydrolyzed per minute per gram of tissue protein (specific activity). Because specific activity is a ratio of total enzyme activity to tissue protein content, changes in specific activity can result from changes in the numerator and/or the denominator. Changes in mucosal protein content may in fact have no relation to changes in disaccharidase activity (Koldovsky et al., 1982). Therefore, it may be more appropriate to express the disaccharidase activities in the segments as segmental activity, i.e. activity per unit length of the intestine. This removes the possibility of any artifact when disaccharidase activity is related to tissue protein content and more accurately reflects true functional activity. In the present study, when segmental activity of disaccharidases of each dietary group calculated, values of 25.39-3 1.75 (maltase) ,4.016.17 (sucrase) and 0.89-l .40 (lactase) mol of hydrolyzed disaccharide X 103/cm intestine were obtained. There was no difference (P > 0.05) in each enzyme activity due to the different carbohydrates ingested. There are several unclear points that remain to be investigated. Hung et al. ( 1989) reported that intestinal maltase, sucrase, and lactase activities of sturgeon were not affected
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by feeding different carbohydrate sources. However, the results obtained from sturgeon were quite different from our data with tilapia. In sturgeon, glucose and maltose were best utilized. Maltose, sucrose and lactose were observed in the plasma of sturgeon when they were fed diets containing maltose, sucrose and lactose, respectively (Hung, 1991). It was suggested by the author that disaccharides may diffuse passively through the cells or through the cell-to-cell junctions in the sturgeon gastrointestinal mucosa. Higher body fat in fish fed the starch diet than those fed the glucose diet in the present study is in agreement with previous studies (Shiau and Lin, 1993; Shiau and Chen, 1993). Fish fed the disaccharide-containing diets had intermediate levels of body fat. The lack of a lipogenic effect in sturgeon fed diets containing lactose or sucrose has been attributed to low intestinal lactase and sucrase activities (Hung et al., 1989). Similarly, relatively low intestinal lactase activity was observed in this study with tilapia. Body fat in the fish fed the maltose and sucrose diets was similar (Table 3). The storage of body fat is an indication of carbohydrate utilization. The lipogenic enzymes were not measured in the present study. Studies are necessary to elucidate the lipogenic pathways in fish fed disaccharides.
Acknowledgements This work was supported by a grant from the National Science Council of the Republic of China, grant number NSC 84-232 1-B-019-001.
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