Animal Feed Science and Technology, 30 (1990) 313-319 Elsevier Science Publishers B.V., Amsterdam
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Effect of dietary oligosaccharides on the digestion of pea starch by growing chicks J. Trevifio l, C. Centeno 2, A. Brenes 2, P. Y u s t e 2 a n d
L. R u b i o 2
' Departamento de Producci6n Animal Facultad de Veterinaria, Ciudad Universitaria, 28040 Madrid (Spain.) 21nstituto de Alimentaci6n Animal del CSIC, Ciudad Universitaria, 28040 Madrid (Spain) (Received 30 May 1989; accepted for publication 7 December 1989 )
ABSTRACT Trevifio, J., Centeno, C., Brenes, A., Yuste, P. and Rubio, L., 1990. Effect of dietary oligosaccharides on the digestion of pea starch by growing chicks. Anita. Feed Sci. Technol., 30:313-319. Oligosaccharides from pea meal were extracted with 80% methanol; after filtration, the solid residue was dried and the methanolic extract concentrated under vacuum and lyophilized. Seven-day-old chicks were randomly divided into three groups of eight birds and placed in individual cages. The chicks received diets containing 65% oligosaccharide-free pea residue with or without supplemental oligosaccharide dried extract (56 and 28 g kg-1 diet). At 28 days old, the chicks were killed and their intestinal tracts removed; the digesta from the jejunum, ileum and caeca were analysed for starch. No significant differences in weight gain and feed utilization were found among chicks. However, there was a significant increase in the length of jejunum, ileum and caeca when the concentration of oligosaccharides in the diet was increased. The presence of oligosaccharides in the diet decreased slightly the percentage of starch digested at the ileum, but starch digestibility was very high and similar in all diets after passage through the small intestine and caeca. These results indicate that the oligosaccharide content did not measurably affect the nutritional qualities of peas for chicks.
INTRODUCTION
There is little information on the digestibility of legume starch by poultry. Guillaume ( 1978 ) found that the digestibility of bean starch by young chicks was lower than that of the starch in maize, and Longstaff and McNab ( 1987 ) observed that the starch in ground peas was less digested by adult cockerels than that in wheat meal. Pea seeds (Pisum sativum L. ), in common with other legumes, contain significant amounts of the oligosaccharides of the raffinose family (CerningBeroard and Filiatre, 1977; Quemener and Mercier, 1980). The raffinose 0377-8401/90/$03.50 © 1990 - - Elsevier Science Publishers B.V.
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family sugars, such as verbascose, stachyose and raffinose, escape digestion and accumulate in the lower intestinal tract where bacteria are able to metabolize them to form volatile fatty acids and large amounts of carbon dioxide, hydrogen and methane (Rackis, 1975; Anderson et al., 1979; Reddy et al., 1980; Wiggings, 1984; Cummings et al., 1986). Consequently, the presence of substantial amounts of these oligosaccharides may affect the digestibility of nutrients. The objective of this study was to investigate the effect of dietary oligosaccharide content on the degradation of pea starch within the various sections of the intestinal tract of broiler chicks. MATERIALS AND METHODS
Extraction of oligosaccharides Whole, dry seeds ofPisum sativum (cv. 'Frisson') were milled with an ultracentrifuge mill fitted with a 0.5 mm screen. The extraction of oligosaccharides was achieved by shaking 400 g of pea meal with 2 1 of 80% ( v / v ) methanol for 2 h, followed by filtration through cheesecloth. The residue was washed with a further 500 ml of 80% methanol, then placed in trays and dried in a forced-air oven at 45 °C. The methanolic extract and washings were combined, filtered and concentrated under vacuum, then lyophilized. The concentrations of raffinose, stachyose and verbascose in pea meal, the oligosaccharide-free pea residue and the oligosaccharide dried extract appear in Table 1.
Birds and experimental procedure One-day-old male broiler chicks (Hubbard) were fed on a proprietary starter diet until the beginning of the experiment. On Day 7, 24 chicks were randomly divided into three groups of eight birds each with a mean group weight of 2602 g and a maximum difference in weight of 16 g between groups. The eight birds within each group constituting eight replicates were individually housed in metabolism cages. Feed and water were supplied ad libitum. The chicks were fed on experimental diets for 21 days. Individual body weights and feed intakes were recorded weekly. Three isocaloric and isonitrogenous semi-synthetic diets based on pea extracted meal (650 g kg- 1) were prepared; the pea extracted meal supplied all the starch contained in the diets. Oligosaccharide dried extract was included in the diets at levels (g kg -1 ) of 0 (Diet A), 28 (Diet B) and 56 (Diet C) in place of glucose; the concentration of oligosaccharides in the experimental diets was therefore approximately equivalent to that of diets containing 0,
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TABLE 1 Concentrations of raffinose, stachyose and verbascose in pea seeds, oligosaccharide free pea residue and oligosaccharide dried extract (g kg- t DM ) Material
Oligosaccharides Raffinose
Pea seeds Oligosaccharide free pea residue Oligosaccharide dried extract ~
Stachyose
Verbascose
6.7
22.5
28.5
0.9
1.8
2.7
66.7
234.4
286.8
tProximate analysis (g kg-1 DM ): crude protein, 28.0; crude fibre, 6.0; total soluble sugars, 902.5; starch, 36.3.
TABLE 2 Composition of experimental diets (g kg-~ ) Ingredients
Diets A
B
C
Oligosaccharide-free pea residue t Isolated soya bean protein 2 Glucose Sunflower oil Oligosaccharide dried extract Calcium carbonate Dicalcium phosphate Sodium chloride oL-methionine Vitamins and minerals3 Chromic oxide
655.0 51.6 145.3 100.0 0 13.0 19.0 4.3 3.8 5.0 3.0
655.0 51.6 117.3 100.0 28.0 13.0 19.0 4.3 3.8 5.0 3.0
655.0 51.6 89.3 100.0 56.0 13.0 19.0 4.3 3.8 5.0 3.0
Calculated composition Crude protein (g kg- ~) Metabolizable energy (MJ kg- t ) Lysine (g kg -1 ) Methionine plus cystine (g kg- t )
229.7 13.4 13.2 8.3
229.7 13.3 13.2 8.3
229.7 13.2 13.2 8.3
Iproximate analysis (g kg-~ DM): crude protein, 272.9; ether extract, 20.0; crude fibre, 76.8; starch, 428.5; ash, 43.1. 2Purina Protein, S.A. Barcelona, Spain. 3Supplied the following in mg kg- ~diet: retinol, 3; cholecalcipherol, 55; thiamine, 5; riboflavin, 12.5; pyridoxine, 7.5; biotin, 0.2; pantothenic acid, 25; choline chloride, 2250; menadione sodium bisulphite, 2.5; niacin, 75; cyanocobalamin, 0.04; tocopherylacetate, 25; pteroylmonoglutamic acid, 3.5; Mn, 175; Zn, 100; Fe, 75; Cu, 7.5; I, 1.2; Co, 5; Mo, 0.2; Se, 0.15.
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250 and 500 g kg- 1 of pea meal. The composition of the experimental diets is given in Table 2. When the chicks were 28 days old, they were killed by cervical dislocation and their intestinal tracts were quickly removed. The length of the following intestinal sections was determined: jejunum (from the distal part of the duodenum to the yolk stalk diverticulum ), ileum (from the yolk stalk diverticulum to the ileo-caecal junction) and caeca. The contents of these sections were collected, lyophilized and ground to a fine powder.
Analytical methods The concentrations of raffinose, stachyose and verbascose in the pea meal, oligosaccharide-free pea residue and oligosaccharide dried extract were determined by high-pressure liquid chromatography following the method described by Quemener and Mercier (1980). Quantification was achieved by area comparison with external standards of raffinose, stachyose (Sigma Co., U.S.A. ) and verbascose (a gift from E. Cristofaro; Nestl6 Ltd., Switzerland). Starch was determined by an enzymatic method after the extraction of interfering glucosidic oligosaccharides with 75% propan-2-ol (Karkalas, 1985). Chromic oxide was determined colorimetrically using the procedure described by Brisson ( 1956 ).
Statistical analysis The results obtained were subjected to analysis of variance according to Snedecor (1967) and to Duncan's multiple range test ( 1955 ). RESULTS The responses of the chicks are summarized in Table 3. There were no significant differences among chick groups in weight gain, feed intake and feed utilization. However, the chicks receiving oligosaccharide dried extract had a larger relative length of jejunum, ileum and caeca than those fed on the control diet ( P < 0.05 ). In general, an increase in oligosaccharide content in the diet corresponded to an increase in the length of the different intestinal sections. The effects of the amount of dietary oligosaccharides on starch digestion are shown in Table 4. The starch content of digesta from the jejunum was quite similar for the three diets; in the ileum and caeca, however, a lower content was found in the chicks fed on the control diet and Diet C respectively. The percentage of starch digested through the various intestinal sections differed very little between birds given the different diets. Starch digestibility for the diet based on oligosaccharide-free pea residue (Diet A) varied from 74.1% at the jejunum to 96.8% at the caeca. For both groups of birds given
EFFECT OF OLIGOSACCHAR1DESON DIGESTION OF PEA STARCH
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TABLE 3 Performance and relative length of intestinal sections of chicks fed from 14 to 28 days on pea diets with three levels of oligosaccharide dried extract Oligosaccharide dried extract (g kg- ~ diet) 0 Weight (kg) Feed intake (kg per chick ) Feed to gain ratio
28
SE ~
56
0.586 1.042
0.575 1.042
0.564 1.026
0.0094 0.0114
1.778
1.812
1.819
0.0165
Length of intestinal sections (cm kg-1 body weight) Jejunum 49.5 a'2 55.5 b Ileum 51.8 a 60.0 b Caeca 13.1 a 13.7 ~b
59.9 c 62.3 b 14.5 b
1.02 1.04 0.16
Standard error. 2Means within a row showing different superscripts are significantly different ( P < 0.05 ).
TABLE 4 Content of starch in digesta (% of DM ) and starch digestibility (%) in intestinal sections of chicks fed from 14 to 28 days on pea diets with three levels of oligosaccharide dried extract Oligosaccharide dried extract (g kg -1 diet)
SEI
0
28
56
Starch content Jejunum Ileum Caeca
21.4 9.3 a,2 6.9
23.2 7.0
22.5 11.2 b 6.6
0.85 0.62 0.21
Starch digestibility Jejunum Ileum Caeca
75.3 93.8 96.8
73.8 92.4 96.1
74.0 91.8 97.6
0.52 0.73 0.51
10.9 b
Standard error. 2Mean values with different superscripts differ significantly ( P < 0.05 ).
oligosaccharide-supplemented diets (B and C ) a slightly lower digestibility of starch was noted at the ileum, but the values were high and quite similar to that of the unsupplemented diet when measured at the caeca (97.6-96.1%).
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DISCUSSION
It has been suggested that the high content of oligosaccharides of the raffinose family in many legume seeds might have a depressing effect on broiler growth, possibly by altering the gut microflora (Harry and Chubb, 1964; Hewitt et al., 1973; Guillaume, 1977 ). Hypothetically, the reduction in raffinose, stachyose and verbascose content of pea seeds should improve their nutritional quality. In general, however, the results from this experiment did not support that hypothesis. The addition of an oligosaccharide dried extract from peas to a diet based on oligosaccharide-free pea residue (28 and 56 g kg -~ diet) had little influence on the performance of chicks; growth rate and feed utilization were slightly, though not significantly, better in the chicks fed on the control diet than in those fed on the diets with supplemental oligosaccharides. In contrast, there was a significant increase in the length of the various intestinal sections as the concentration of oligosaccharides in the diet increased. This effect of oligosaccharides on the intestine of birds might be a consequence of the distension of the gastrointestinal tract by the high gas volume resulting from bacterial fermentation of the unavailable sugars raffinose, stachyose and verbascose (Cristofaro et al., 1974; Wagner et al., 1976; Reddy et al., 1980). According to Wiggins (1984), the presence in the small intestine of unabsorbable, water-soluble sugars of low molecular weight, such as raffinose and stachyose, may result in an osmotic effect, leading to fluid retention and an increased rate of passage of digesta that could affect the absorption of nutrients. In the present investigation, addition to the control diet of an oligosaccharide dried extract might have been expected to produce a poorer digestion of pea starch, but this did not occur. The digestion of pea starch by young chicks was scarcely affected by the concentration of raffinose, stachyose and verbascose in the diet. For the control group and both groups given oligosaccharide-supplemented diets the starch digestibility values ranged from 93.8 to 91.8% after passage through the small intestine, and at the caeca more than 96% of the starch was digested. Consequently, it seems unlikely that starch digestion in peas may be limited by ot-galactoside content. These results together with the performance data suggest that the presence of oligosaccharide of the raffinose family of sugars has little influence on the nutritional qualities of peas for chicks. REFERENCES Anderson, R.L., Rackis, J.J. and Tallent, W.H., 1979. Biologically active substances in soy products. In: H.L. Wilcke, D.T. Hopkins and D.H. Waggle (Editors), Soy Protein and Human Nutrition. Academic Press, New York, pp. 209-228. Brisson, G.L., 1956. On the routine determination of chromic oxide in feces. Can. J. Agric. Sci., 36: 210-212.
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Cerning-Beroard, J. and Filiatre, A., 1977. Characterization and distribution of soluble and insoluble carbohydrates in legume seeds: horse beans, peas, lupines. In: Commission of the European Communities, Protein Quality from Leguminous Crops. ECSC-EEC-EAEC, Brussels-Luxembourg, pp. 243-250. Cristofaro, E., Mottu, F. and Wuhrmann, J.J., 1974. Involvement of raffinose family of oligosaccharides in flatulence. In: H. Sipple and K. McNutt (Editors), Sugars in Nutrition. Academic Press, New York, pp. 313-336. Cummings, J.H., Englyst, H.N. and Wiggins, H.S., 1986. The role of carbohydrates in lower gut function. Nutr. Rev., 44: 50-54. Duncan, D.B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Guillaume, J., 1977. Use of field beans ( Ficiafaba L. ) and peas (Pisum sativum L. ) in laying hen and growing chicken diets. In: Commission of the European Communities, Protein Quality from Leguminous Crops. ECSC-EEC-EAEC, Brussels-Luxembourg, pp. 217-234. Guillaume, J., 1978. Digestibilitd des proteines, de l'almidon et des lipides de deux types de f6verole ( Viciafaba L. ) crue ou autoclav6e chez le poussin. Arch. GefliJgelk., 42: 179-182. Harry, E.G. and Chubb, L.G., 1964. Relationships between certain biochemical characteristics and pathological activity in avian strains ofE. coli. J. Comp. Pathol. Ther., 74:180-188. Hewitt, D., Coates, M.E., Kakade, M.L. and Liener, I.E., 1973. A comparison of fractions prepared from navy (haricot) beans (Phaseolus vulgaris L. ) in diets for germ-free and conventional chicks. Br. J. Nutr., 29: 423-435. Karkalas, J., 1985. An improved enzymic method for the determination of native and modified starch. J. Sci. Food Agric., 36: 1019-1027. Longstaff, M. and McNab, J.M., 1987. Digestion of starch and fibre carbohydrates in peas by adult cockerels. Br. Poult. Sci., 28: 261-285. Quemener, B. and Mercier, C., 1980. Dosage rapide des glucides ethanolo-solubles des graines de Idgumineuses par chomatographie liquide sous haute pression. Lebensm.-Wiss. Technol., 13: 7-12. Rackis, J.J., 1975. Oligosaccharides of food legumes: Alpha-galactosidase activity and the flatus problem. In: A. Jeanes and J. Hodge (Editors), Physiological Effects of Food Carbohydrates. The American Chemistry Society, Washington, pp. 207-221. Reddy, N.R., Salankhe, D.K. and Sharma, R.P., 1980. Flatulence in rats following ingestion of cooked and germinated black gram and fermented product of black gram and rice blend. J. Food Sci., 45:1161-1164. Snedecor, G.W. and Cochran, W.G., 1967. Statistical Methods, 6th edn. Iowa State University Press, Ames. Wagner, J.R., Becker, R., Gumbmann, M.R. and Olson, A.C., 1976. Hydrogen production in the rat following ingestion of raffinose, stachyose and oligosaccharide-free bean residue. J. Nutr., 106: 466-470. Wiggins, H.S., 1984. Nutritional value of sugars and related compounds undigested in the small intestine. Proc. Nutr. Soc., 43: 69-75.