energy requirements for growth of rainbow trout (Oncorhynchus mykiss)

Aquaculwe, 106 (1992) 161-169 Elsevier Science Publishers B.V.. Amsterdam

161

AQUA 50009

Contribution of digestible energy from carbohydrates and estimation of protein/energy requirements for growth of rainbow trout (Oncorhynchus mykiss)

J.D.

Kim’

and S.J. Kaushikb

aDepa~~menfo/dnimolScience. College ofAnimrrlAgricullure.e,Kangweon National University. Chuncheon. South Korea bLobomloire de Nutrition des Poisson, INRA. Saint Pt!esur Nivelle. France (Accepted6 January 1992)

ABSTRACT

Kim, J.D. and Kaushik, S.I.. 1992. Contribution of digestible energy from carbohydrates and ertimation ofprotein/energy requirements for growth of rainbow trot (Oncorhynchus mykiss). Aquacu/ture. 106: 161-169.

Four diets having different digestible protein (PP) to digest;b!r‘ energy (DE) ratios were formulated to study the protein-sparing effect of DE from carbohydrates and to estimate the DE requirements for growth of rainbow trout. A growth trial was conducted for 8 weeks. Digestibility measurements were made over 2 weeks. Trout (initial weights 37 and 100 g for growth and digestibility trials, respectively) were fed tn satiation twice a day at a constant water temperature of 7S”C. Apparent digestibility coefficients (ADC) for dry matter, starch and energy drcreased with an increase in dietary raw starch level. The metabolic fecal nitrogen lass was estimat’:d tn be 150 mg N/ 100 g of dry diet. Fish fed a high protein diet with 48% DP. 9% digestible fat [DL) and 20% digestible carbohydrates (DC) showed the best performance for weight gain, feed conversion ratio and daily growth index. However, the highest protein efficiency ratio (2.3) and proiein retention efficiency (41.4%) were obsetwd in tish fed a diet containing 38.9 ar.d 30% of DP. DL and DC, respectively. The whole body composition of the fish was not affected by dietary treatments. Liver glycogen and hepatosomatic index were positively related to dietary digestible carbohydrate levels. The digestible protein requirement per unit weight gain (g DP required per kg production) varied depending npnn the DP/DE ratios. On the other hand. DE requirement per unit weight increment was relatively constant (about 17.5 MJ for the production of of rainbow trout), irrespective of the dietaty treatment.

I

1kg

Correspondence 10: Dr. S.J. Kaushik, Laboratoire de Nutrition Pee SW Nivelle. France.

0044-8486/92/$05.00

des P&sons,

[NRA, 643 10 Saint

0 1992 El sevier Science Publishers B.V. All rights reserved.

162

J.D.KIMAN” s J. KA”SHlK

INTRODUCTION

Carbohydrates are generally a major source of energy in diets for terrestrial domestic animals such as poultry, swine and cattle. In most teleosts, however, the digestive and metabolic utilization ofcarbohydrates is limited (Singh and Nose, 1967; Palmer and Ryman, 1972) and depends upon the nature or complexity of the carbohydrate (Bergot, 1979a,b; Hilton and Atkinson, 1982; Spannhof and Plantikow, 1983). It has also been shown that there is potential for improvement of starch digestibility through technological treatments like gelatinization and extrusion (Bergot and Breque, 1983). Even though carnivorous fish such as trout are ill-adapted to digest complex carbohydrates, from a practical point of view, an incorporation of substantial levels of carbohydrate is inevitable in fish diets (Kim, I989 ) Therefore, use of highly digestible carbohydrate sources in diet formulation is advisable to increase energy availability to fish. Kaushik and Oliva-T&s ( 1985) reported that incorporation of 3b% gelatinized starch in the diet for rainbow trout improved protein utilization with a reduction of nitrogen excretion. Kaushik et al. ( 1989) have also shown that the inclusion of even higher levels of extruded cereals or extruded starch which increased dietary energy availability did not adversely affect growth of rainbow trout. The present study was undertaken to evaluate the protein-sparing effect of digestible energy from carbohydrates and to estimate the protein and energy requirement for growth of trout fed diets in which the digestible protein to digestible energy (DP: DE) ratios were modified by varying the levels of digestible carbohydrate. MATERIALS

AND METHODS

Feedformulation Four experimental diets were formulated in which the level of inclusion of fat (9% of dry matter) and the gross energy content (20.5 kJ/g DM) were maintained constant. In order to vary the DP:DE ratios, three diets with a constant crude protein (CP) level of 41% with varying proportions of raw and gelatinized corn starch were formulated and designated as GS, MS and RS. A fourth diet with a higher protein level (CP 5 I%), was also formulated and designated as HP (Table 1). After pelleting, using a laboratory pellet mill (Simon-Heesen, Oslo) without steam conditioning, an aliquot of each diet was randomly sampled for analyses (Table 1). Chromic oxide was added to 1% level to a portion of each mixed diet as an inert tracer for measurement of nutrient digestibility. A protein-free (PF) dret was also formulated to measure the metabolic fecal nitrogen loss.

Dl0EsTlBl.E

TABLE

ENERGY NEEDS FOR PROD”crlON

163

OF TROUT

I

Composition

and apparent

digestibility

Ingredient

coefficients

(ADC)

ofthe experimental

diets

Diet RS

GS

HP

PF

(%) Herring meal Fish oil Coin starch wlatinized

52.0 1.8

52.0 1.8

52.0 1.8

66.0

38.2 4.0 2.0 1.0 1.0

21.0 21.2 2.0 I.0 1.0

4.0 38.2 2.0 1.0 1.0

10.0 20.0 2.0 1.0 I.0

39.0 39.0 2.0 2.0 2.0 1.0

DM basis) 41.0 42.1 9.9 9.9 38.5 38.9 7.3 7.3 20 12.0 2043.0

41.9 9.9 38.2 7.4 2034.0

50.6 9.5 28.8 8.8 2063.0

1.7

raw

Vitamin mix’ Mineral mix’ Binder (a-starch) Cr:O, Chemical composition Crude protein Crude fat Starch Ash Gross energy

(gork.IilOO&

ADC values (%) D,y matter Protein Fat Starch Energy DP/DE

15.0

ratio

78.7 93.0 (95.4)’ 96.3 79.7 85.1

77.0 94.2 (96.5) 96.1 70.3 83.7

73.5 94.1 (96.4) 96.7 61.1 80.9

82.7 94. I (95.9) 96.3 78.5 89.1

22.2

23.2

24.0

25.9

ND’ ND’ ND’ 22.3 57.0

(m&J) ‘EIFAC, 1971. ‘Luquet. 1971. ‘No1 determined. ‘True digestibility

coeilicicnl

of dietary

protein.

Feeding trial

An I-week feeding trial was conducted at the INRA Experimental Fish Farm (Donzacq, Landes) at a constant water temperature of 17.5”C. Eight groups of 100 rainbow trout (Oncorhynchus mykiss) were randomly alloted to individual concrete compartments (holding capacity 800 L;flow rate 160 l/min). The fish (mean initial wt. 37 g) were collecti-iely weighed and counted every 4 weeks in order to follow the overall growtlr. Mortality was checked daily and the number and weight of dead fish were recorded for further calculation of total weight gain and feed consumption based on total fish days. Fish were

164

J.D. KIM AND s 1. KAUSHlK

fed to satiety twice a day at 09.00 and 15.00 h except for the day before weighing. Digestibility trial Four homogeneous groups of 15 fish (mean body wt. 100 g) were atloted to four cylindroconical tanks (holding capacity 60 1; flow rate 4 l/min). The photoperiod was regulated to 12 h light and 12 h dark. Following an adaptation period of 2 weeks, during which the fish were fed each experimental diet containing I% of chromic oxide, the tish were fed to satiety twice a day at 09.00 and 15.00 h and feces were collected over a 5-day period using a continuous automatic feces collector (Choubert et al., 1982). After this trial, each group was fed the protein-free diet and feces were collected following a lweek adaptation period. Feces collected on a refrigerated plate were immediately frozen and kept at -20°C until analyzed. The water temperature remained constant at I8 rt 1 “C for this trial. The apparent digestibility of the dietary nutrients as well as the true digestibility of the dietary protein were calculated using the formula of Maynard and Loosli ( 1969) and Kim ( 1974), respectively. Analytical methods Random samples of 20 fish (initial) and 15 fish from each group at the end of the trial were withdrawn, anaesthetized by immersion in a bath ( 1: 2500) of ethylene glycol mono-phenyl ether (Merck Clevenot, SA, 94 Nogent sur Marne, France) and weighed individually. Livers and digestive tracts removed from 10 fish of the initial and each final group were rinsed in physiological saline solution, individually weighed and immediately frozen in liquid nitrogen. The other 10 initial fish and 5 final fish of each group were used for analysis of whole body composition. All prepared samples were analyzed following the usual procedures: dry matter ( 110°C for 24 h), protein (Kjeldahl, N x 6.25 ) after acid diaestion, liuid after chloroform/methanol ( 2/ 1 v/v) extraction,gross energy ;sing a.Gallenkamp adibatic calorimeter,.starch using glucoamylase and glucose oxidase (Thivend et al., I972), ash (550-C for I2 h), glycogen in liver using a Beckman glucose analyzer (Murat and Serfaty, 1974), and chromic oxide using a block digester after perchloric acid digestion (Bolin et al., 1952). Statist&al analyseswere performed according tothe analysis of variance and multiple range test (PcO.05) of Duncan (1955) usingthe SAS package (SAS Inst. Inc., NC, USA). RESULTSAND DISCUSSION Digestibility of nutrients and energy The dietary crude starch levels as chemically analyzed did not vary among the diets RS, MS and GS (Table I ). However. the digestibility of starch was

different between the diets. The ADC of starch decreased with an increase in dietary raw starch level. This in turn led to a reduction of dry matter and energy digestibiiities. ADCs of protein or frs were not affected by the level of raw starch in the diets. The DP/DE ratios of the four diets could thus be varied from 22 to 26 mg DP/kJ DE (Table 1). Starch digestibility ranged from 60 to 80%. These values are only slightly different from those of Bergot and Breque ( 1983). They found that the digestibility of raw or native starch ranged from 38 to 54% depending on level of dietary feed intake. At low feed intake, starch digestibility was found to be higher. The metabolic fecal nitrogen loss (I 50 mg N/ 100 g dry diet) was similar to that previously reported for rainbow trout weighing 10 to 15 g (Nose, 1967) and carp weighing 130 to 220 g (Ogino et al., 1973). True protein digestibility values were only slightly higher than the ADC of protein. Growth and nutrient intake

The overall growth performance and nutrient intake levels of trout fed the experimental diets for 8 weeks are reported in Table 2. Fish fed diet HP showed the highest final weight, feed:gain ratio, daily growth index and the lowest mortality (PcO.05 ). However, protein ef?iency ratio was significantly higher in fish fed the diet (GS) containing the highest level (38%) of gelatinized TABLE 2 Growth ~rformance

and nmnent intake of trout fed the extwimental

Parameter

Diet

Initial wt. (g/fish) Final wt. (g/fish) FGR2 DGI’ PER4 Mortalities’ Intake (gDM orkJ/kgBW Feed Digestible protein Digestible fat Dtgestible starch Digestible energy

diets for 8 weeks’

GS

MS

Rs

HP

37.3 IIO.3b I.lb 2.6b 2.3” 2.8

37.1 106.0’ I.I’b 2s Z.lb 4.1a

36.9 IO7.D~ 1.T 2.5” 2.Ob 3.c

37.3 119.5’ 1.0’ 2.8’ 2.Ob

17.7 6.7= .7k 5.4* 302.2

18.3 7.3k 1.Sab 5.v 313.4

18.9 7.5b .8’ 4.48 311.5

17.7 8.4’ 1.6’ 4.r 324.4

I.Ob

day-‘)

I

I

‘Values that do not share a common superscript letter in the same row are significantly different (PCO.05). ‘Feed gain ratio=feed intake, DM/weight gain. ‘Daily gmwh index= [ (final wt.)“3-(initial wt.) “‘]/Number of daysxIO0 (Iwama and Taut& 1981). ‘Protein efftciency ratiozweight gain/crude protein intake. ‘% based on the total fish-days of 5700.

starch. Total dry matter and digestible energy intake levels were not different (E-0.05) among treatments. At similar feed intake levels, digestible protein intake (g/kg BW day-‘) was significantly higher (8.4 g) in fish fed diet HP than in those fed diet GS (6.7 g). Bergot (1979a) found that at a given protein intake leve!, inclusisn of 30% glucose ied to better growth performance than inclusion of 30% native starch. She suggested that trout could tolerate a daily dietary glucose intake of 5.5 g/kg BW. Under the current experimental conditions, the group of fish fed diet GS had the highest digestible starch intake (5.4 g/kg BW day-‘) and did not show any signs of intolerance. Composition of whole body and liver Whole body proximate composition (moisture, protein, fat and ash) of fish at the end of the experiment was not affected by the dietary treatments (P~0.05). However, significant differences (P~0.05) were observed between initial and final composition: moisture content decreased from 77 to 7 1%;crude protein increased from 14.4 to around 16.6%;crude fat increased from 6.4 to about 10% and ash levels in the whole body increased from 0.8 to 2.5%. The viscerosomatic index was not affected by dietary treatment and did not change with body size (range 8.4 to 9.6%). With regard to the composition of the liver, certain dietary effects were apparent (Table 3). Liver glycogen increased with the increase in dietary gelatinized starch level, reaching a level of 12% in trout fed diet GS. Such an increase in hepatic glycogen levels, with the consequent enlargement of the liver, has been noted by several other authors (Phillips et al., 1948; Lee and Putnam, 1973; Bergot, 1979a) and corresponds to the abnormal changes in HSI (Table 3). Liver protein contents were more or less inversely correlated to that of hepatic glycogen levels. Nutrient retention Nutrient retention efficiencies are presented in Table 4. Protein and energy retention was high in all groups. There were no significant differences in lipid TABLE 3 Liver composition of trout after an I-week feeding (g/LOOg. wet wt. basis)’ Diet

Moisture

Crude pmtein

GlyCO!&?n

HSI*

Initial GS

19.6 72.2b 74.1” 76.1a 74.3”

14.9 12.6b 15.2” 17.1. 14.4.b

0.67 12.1a 0.P 2.1’ 5.7”

1.2 2.1’ 1.P 1.2c l.6b

MS

RS HP

Walues that do not share a common superscript letter in the same column are significantly different (P-zO.05); values are the mentu of two ~IOUDS with three determinations from 10 fish of each LOUD _ and 10 initial fish. ‘Hepatosomatic index=wet liverwt./wet body w.x 100.

DtGEsrtsLE

ENERGY NEEDS FOR PRODUcTtON

167

OF TROUT

TABLE 4 Nutrient

retention

efticiencv

INRE)

of trout fed

the experimental

diets for 8 weeks’

NRE (%)

GS

MS

RS

HP

Protein

41.4’ (44.5) 120.3 (124.8) 40.8 (47.9)

37.8b (40.2)b III.3 (115.1) 38.0 (45.5)

37.lb (39.37 103.7 (107.3) 36.5 (45.1)

36.6’ (38.9)b 124.8 (129.6) 42.4 (47.6)

Lipid Ener%y

‘NRE (%) = 100x ((final w~.x%nuuient of tinal whole body)-(initial wI.x% nutnentof initial whole body) )/crude nutrient intake, DM NRE based on digestible nutrient intake is shown in parentheses: values that do not share a cmmnon superscript letter in the same row are significant different (P-CO.05).

and energy retention efficiencies among the treatments. Energy retention ranged from 36 to 42% of gross energy intake (45 to 48% of DE intake). In terms of efficiency of protein retention per unit (crude or digestible) protein intake, results obtained here show that the incorporation of digestible carbohydrate leads to significant protein sparing. This is in agreement with our earlier observations (Kaushik and Oliva-Teles, 1985). Fish fed the diet containing 41% CP and 38% gelatinized starch (diet GS) showed a significantly higher protein retention efliciency ( > 4 I %) than those fed the high protein diet (37#). Bergot ( 1979a) did not find any effect of dietary starch availability on protein retention whereas energy retention was significantly improved by glucose incorporation in comparison to crude starch. The lack of a significant effect in her studies can partially be attributed to the high dietary protein (CP 45 to 55%) levels used and to relatively poorer growth rates of rainbow trout in her study. Protein and energy requirements

It has been suggested that data on the protein requirement for growth be expressed in absolute terms, for example, per unit body weight per day or per unit body weight increment ( Luquet and Kaushik, 1980, Bowen, 1987). Several earlier works have demonstrated that an increase in the proportion of dietary non-protein energy leads to better protein utilization (Kaushik and Oliva-Teles, 1985; Cho and Kaushik, 1990). As fish are known to meet agreat part of their energy requirement from dietary protein, the dietary DP/DE ratios exert considerable influence on protein and energy utilization efficiencies. A DE level of between 14 and I7 MJ/kg feed and a DP/DE ratio of 22 to 25 g/MJ has been recommended for production diets of salmonids (Cho and Kaushik, 1990). The present results she\:, that, even when expressed as per unit weight gain, protein requirements (either crude or digestible protein) can vary considerably depending on dietary DP/DE ratios, even within

MJ

0 GE

s/ill hlh 450

400

350

i

i 22

23 24 DP/DE ratio

300

25

22

23 DP/DE ratio

Fig. 1. Quantityof gross (GE) or digestible (DE) energy (W) and crude (CP) OTdigestible(DP) protein(g) neededfor the productionof I kg of rainbowtroutfed diets with differentDP/DE ratios.

the range of 22 to 26 g/MJ (Fig. I ). While at the same dietary protein level, an increase in dietary digestible energy level (diets RS, MS and GS) leads to lower protein need per unit body weight gain, an increase in dietary protein level (diet HP) leads to considerable protein loss. Under the present experimental conditions, about 390 g and 460 g of digestible protein were needed for 1 kg of trout production with diets GS (DP 38%) and HP (DP 48%), respectively. Depending on the diet, gross energy required for unit production is also variable. Considerable homogeneity, however, appears when one considers the digestible energy requirement. The DE requirement per unit weight gain of trout grown at 18°C with the same diets GS and HP was not greatly different, being 17.4 MJ and 17.6 MJ, respectively. Such a relative constancy in terms of DE requirement per unit body weight gaiu has practical significance, in as much as this can form the basis for preparing feeding charts for farmed fish fed diets varying in DE density. ACKNOWLEDGEMENTS

This work was supported by financial assistance from INRA (Institut National de la Recherche Agronomique, France) to the first author. Thanks are also due to MS Cescosse, Hontang and Sandres for care during feeding trials at the fish farm.

REFERENCFS Bewt, F., 1979a. Carbohydrates in rainbow trout diets: effects of the level and scwce of carbohydraies and the number of meals on gmwth and body composition. Aquaculture, 18: 157-167.

Betgot, F., 1979b. Effects of dietary carbohydrates and their mode of distribution on glycaemia in rainbow trout (Salmogairdneri R.). Comp. B&hem. Physiol., 64A: 543-547. Bergot, F. and Greque, J., 1983. Digestibility of starch by rainbow trout: effects of the physical state of starch and of the intake level. Aquaculture, 34: 203-212. Boiin, D.W., King. R.P. and Klostennan, W.W., 1952. A simplified method for the determination ofchromic oxide (Cr,O,) when used as an inert substance. Science,16:634-635. Bowen. S.H., 1987. Dietary protein requirements of fishes-a reassessment. Can. J. Fish. Aquat. Sci., 44: 1995-2001. Cho, C.Y. and Kaushik, S.J., 1990. Nutritional energetics in fish: energy and protein utilization in rainbow trout (Salmogairdneri). World Rev. Nutr. Diet., 61: 132-172. Choubert, G., De la Noue, 1. and Luquet. P., 1982. Digestibility ir. fish: improved device for the automatic collection of feces. Aquaculture, 29: 185-l 89. Duncan, D.B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. EIFAC, I97 1. Salmon and Tmut Feeds and Feeding. EIFAC Tech. Pap., 12.29 pp. Hilton, J.W. and Atkinson, J.L., 1982. Response of rainbow trout (S&m gairdneri) to increased levels of available carbohydrate in practical trout diets. Br. J. Nutr., 47: 597-607. Iwama, G.K. and Tautz, A.F., 198 1. A simple growth model for salmonids in hatcheries. Can. J. Fish. Aquat. Sci., 38: 649-656. Kaushik, S.J. and Oliva-T&s, A., 1985. Effect of digestible energy on nitrogen and energy balance in rainbow trout. Aquaculture, 50: 89-101. Kaushik, S.J., M&dale, F., Fauconneau, B. and Blanc, D., 1989. Effect of digestible carbohydrates on protein/energy utilization and on glucose metabolism in rainbow trout (Salmo gairdneri R.). Aquaculture, 79: 63-74. Kim, J.D., 1989. Comparaison des valeurs nutritionnelles des nutriments 6nerg6tiques chez la truite arc-en-ciel (Oncorhync/zus mykiss). Th&.e de l’Universit6 Paris VI, 130 pp. Kim, Y.K., 1974. Determination oftrue digestibility of dietary proteins in carp with chromic oxide-containing diet. Bull. Jpn. Sot. Sci. Fish., 40: 651-653. Lee, D.J. and Putnam, G.B., 1973. The response of rainbow trout to varying protein/energy ratios in a test diet. 1. Nutr., 103: 916-922. Luouet. P.. 1971. Efflcacitt des orotCines en relation awe leur taux d’incomoration dans l’alimeniation de la truite arc-enhel. Ann. Hydrobiol., 2: 175-186. _ Luquet, P. and Kaushik, S.J., 1980. Besoin en proteines et en acidesamin6s. In: Nutrition des Poissons. CNRS, Paris, pp. 171-183. Maynard, L.A. and Loosli. J.K., 1969. Animal Nutrition, 6th edn. McGraw-Hill, New York, NY,613pp. Murat, J.C. and Serfaty, A., 1974. Simple enzymatic determination of polysaccharide (glycopen) content ofanimal tissues. Clin. Chem., 20~1576-1577. Nose, T., 1967. On the metabolic fecal nitrogen in young rainbow trout. Bull. Freshwater Fish. Res. Lab., 17: 97-105. Ogino. C., Kakino, J. and Chen, M.S., 1973. Protein nutrition in fish. II. Determination of metabolic fecal nitrogen and endogenous nitrogen excretions of carp. Bull. Jpn. Sot. Sci. Fish., 39: 519-523. Palmer. T.N. and Ryman, B.E., 1972. Studies on oral glucose intolerance in fish. J. Fish Biol., 4: 311-319. Phillips, A.M., Tunison, A.V. and Brockway, D., 1948. Utilization of carbohydrates by trout. N.Y. Fish. Res. Bull., 1 I: l-44. Singh, R.P. and Nose, T., 1967. Digestibility of carbohydrates in young rainbow trout. Bull. Freshwater Fish. Res. Lab., 17: 21-25. Spannhof, L. and Plantikow, H., 1983. Studies on carbohydrate digestion in rainbow trout. Aquaculture, 30: 95-LOS. Thivend, P.. MBrcier. C. and Guilbot, A., 1972. Determination of starch with glucoamylase. IO: R.L. Whistler and J.N. Bemiller (Editors), Methods in Carbohydrate Chemistry, Vol. VI. Academic Press, New York, NY, pp. 100-105.