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Sugars and Starch of Wheat Bran Mash and Steam-Pellets
SOY PHOSPHOLIPIDS AND GROWTH
REFERENCES Allan, J. E., 1961. The determination of zinc in agricultural materials by atomic-absorption spectrophotometry. Analyst, 86: S30-S34. A. O. A. C , 1960. Official Methods of Analysis Association of Official Agricultural Chemists, Washington, D.C.
Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Kratzer, F. H., P. Vohra, R. L. Atkinson, P. N. Davis, B. J. Marshall and J. B. Allred, 1959a. Fractionation of soybean oil for growth and antiperotic factors. 1. Non-phospholipid nature of the factor. Poultry Sci. 38: 1049-1055. Kratzer, F. H., J. B. Allred, P. N. Davis, B. J. Marshall and P. Vohra, 1959b. The effect of autoclaving soybean protein and the addition of ethylene-diaminetetraacetic acid on the biological availability of dietary zinc for turkey poults. J. Nutrition, 82 : 313-322. Perkin-Elmer, 1966. No. 990-9341, Supplement to Analytical Methods for Atomic Absorption spectrophotometry. Perkin-Elmer Corp., Norwalk, Conn. Vohra, P., J. B. Allred, I. S. Gupta and F. H. Kratzer, 1959. Fractionation of soybean oil meal for growth and antiperotic factors. 2. Studies with genistin and soysterols. Poultry Sci. 38: 1476-1477. Vohra, P., and F. H. Kratzer, 1964. Influence of various chelating agents on the availability of zinc. J. Nutrition, 82: 249-256.
Sugars and Starch of Wheat Bran Mash and Steam-Pellets R. M. SAUNDERS, H. G. WALKER, JR. AND G. O. KOHLER Western Regional Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Albany, California 94710 (Received for publication May 8, 1969)
P
ELLETING poultry rations has been known for almost 40 years. Reports from England (Molyneaux, 1930) and the U. S. (Patton et al., 1937) were among the first to show increased body weight in chicks after pellet feeding when compared to mash feeding. Since that time, considerable research has been carried out in this field, but no adequate reasons have been discovered to completely account for the phenomenon (Calet, 1965). The obvious advantages and disadvantages of feeding pellets or mash have been listed (Calet, 1965; Arscott, 1967), but it is difficult to cite the actual physical or chemical changes
that occur during the steam-pelleting process that account for the large differences found experimentally in metabolizable energy (M.E.) values (Cave et al., 1965). This laboratory is studying the factors which contribute to these differences in observed M.E. values. One factor which seems to be involved is the rupture of aleurone cells during processing (Saunders et al., 1968). This communication reports that the digestion rate of wheat bran starch by chick cs-amylase increases after steam-pelleting. Similar observations about pelleting have been recorded by Hastings and Miller (1961) using other enzymes. However, our
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
better on a zinc-deficient CG-diet than on a SB-diet. EDTA improved the growth on both the diets but SPL was significantly growth promoting only on the CG-diet. The improvement in growth due to SPL in CG-diets was not due to any variations in the dietary Zn, Mn, Cu or Fe contents. The data on the effect of various treatments on mineral contents of tibia and liver are given. EDTA improved the growth by improving the availability of dietary zinc from both the diets. This is ruled out for SPL because no growth improvement was observed when SB-diet was used.
1667
1668
R. M. SAUNDERS, H. G. WALKER, JR. AND G. 0.
KOHLER
findings indicate that this factor is probably not a very important one in explaining observed M.E. differences.
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
ously shaken for 30 minutes with 150 ml. of 0.075M sodium chloride solution. The mixture was sieved through nylon mesh; the residue was reshaken for 5 minutes MATERIALS AND METHODS* with 75 ml. of water and again sieved. The A Canadian hard red spring wheat bran combined filtrates were centrifuged. The in both mash and steam-pelleted form was residual precipitate consisting of starch obtained from Dr. J. D. Summers of the granules and other grain debris was washed University of Guelph, Ontario, Canada. once with water and dried. Pellets manufactured in the laboratory Chick pancreas a-amylase was prepared were prepared in a commercial pellet mill as follows. Pancreas from 4-week old Corfrom mash that was conditioned at 180 to nish White Rock type cross-bred chicks 200°F. for 4 to 5 seconds before extrusion was removed and frozen at —30° until through a -fV m c h die, \\ inch thick. ready for use. The frozen tissue was hoThe sugars were isolated as follows: 25 mogenized in a Waring Blendor at 0° with g. of bran in 400 ml. of 70% aqueous etha- 10 volumes of acetone and centrifuged. The nol was heated under reflux for 1 hour. precipitate was washed twice with cold aceThe mixture was centrifuged and the resi- tone then dried in a desiccator over potasdue again treated under the same condi- sium hydroxide at 0°. The white powdery tions. The two supernatants were combined precipitate was sieved through a 60-mesh and concentrated to about 100 ml. The screen then stored at 0° in a desiccator. aqueous solution was twice extracted with The acetone powder was used in this form 200 ml. of chloroform then concentrated to in all digestions; the a-amylase activity did 20 ml. Sugars in the extract were separated not noticeably decrease over a 6-month peby paper chromatography on Whatman 3 riod under these storage conditions. The MM paper in the descending fashion in sol- amylase activity was 130 units where 1 vent n-butanol-pyridine-water (6:4:3,v/v), unit is expressed as mg. maltose produced and were detected with alkaline silver ni- by digestion of starch by 1 mg. of amylase trate. After separation, the spots or strips in 10 minutes (Laws and Moore, 1963). were eluted with water and the aqueous soStarch digestions with chick pancreas lution analyzed. Sugars were measured by a-amylase were carried out as follows: 60 the phenol-sulfuric acid procedure (Dubois mg. of the crude starch extract from the etal, 1956). bran sample in 5 ml. of 0.15M sodium Measurement of birefringence displayed chloride solution and 5 ml. of 0.04M soby intact starch granules, and staining with dium barbiturate solution, pH 7.0, was Congo Red of gelatinized starch granules treated with 12 mg. (unless otherwise specwere employed to determine the physical ified) of chick pancreas a-amylase preparanature of the starch (Badenhuizen, 1965). tion, 0.2 ml. of toluene was added. For autoNon-water-soluble intact starch granules claved samples the starch extract was auwere crudely isolated from the bran sam- toclaved for 20 minutes at 15 p.s.i.g., ples as follows: 10 g. of bran was vigor- cooled, then diluted with the same amounts of buffer mixture and amylase. The mixture * Reference to a company or product name does not imply approval or recommendation of the was incubated at 70° F. with continuous product by the U.S. Department of Agriculture to agitation. Starch digestion was followed by the exclusion of others that may be suitable. assaying increase in reducing sugar. A 1
1669
SUGARS AND STARCH IN BRAN
RESULTS AND DISCUSSION When aliquots of the sugars in mash and pellets were paper chromatographed and assayed, the distribution pattern shown in Figure 1 was obtained. Details on identification of the individual components have been reported previously (Saunders and Walker, 1969). Total sugars on a dry weight basis found in mash and steam-pellets were 6.48 and 6.20% respectively. With the exception of slightly more tetrasaccharide, xylose and glycerol in mash, the total sugars and their distribution are approximately the same in mash and steam-pellets. Xylose is a component of wheat bran hemicellulose (Adams, 1955) and possibly arises in mash from residual hemicellulase activity during storage. In a similar manner glycerol may arise by
E o
§
FRUCTOSANS FRUCTOSYlRAFFINOSE SIACHYOSE
PAPER CHROMATOGRAPHY INCREASING R, »
FIG. 1. Comparative sugar content of wheat bran mash and steam-pellets. Shaded area, mash; unshaded area, pellets.
residual lipase action since bran is rich in esterases (Engel, 1947). These enzymic activities are largely destroyed during steampelleting and hence lower amounts of xylose and glycerol are observed in pellets. The larger amount of tetrasaccharide in mash cannot be explained at this time. The minor differences found in kinds and amounts of sugars in mash and pellets are so small that they could not have any appreciable effect on the overall M.E. values. About 96% of the starch granules in the mash showed birefringence and were negative to Congo Red staining (i.e. intact granules). In steam-pelleted material only about 30% of the starch granules were intact. After autoclaving, the number of the intact granules decreased markedly but a few showing birefringence always remained. Typical values are given in Table 1 for isolation of intact starch from mash and pellets. The weight of the intact fracTABLE 1.—Starch granules isolated from autoclaved and non-autoclaved bran samples Bran sample Mash Pellet Autoclaved mash Autoclaved pellet
Starch (g.) isolated as intact granules from 10 g. bran 0.68 0.42 0.21 0.08
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
ml. aliquot was removed and diluted with 2 ml. each of water and dinitrosalicylate reagent, then heated for 10 minutes at 100°C. The solution was cooled, diluted to 25 ml. with distilled water and O.D. measured at 530 mil,. (Bernfeld, 1955). Pure wheat starch was used as a digestion standard. Wheat bran used in chick feeding experiments was obtained from the Midwest. Four- to eight-weeks-old Arbor-Acre White Rock chicks in groups of three previously maintained on a commercial diet were starved for 20 hours then fed ad libitum the following wheat bran ration: (a) mash; (b) mash preautoclaved at 15 p.s.i.g. for 20 minutes, and (c) steam-pellets manufactured in this laboratory. After 24 hours the chicks were killed. Microscopic examination of the lower small intestinal content and fecal droppings was carried out to determine the fate of the bran starch. Care was taken to avoid contamination of the fecal droppings by feed scatterings, beak scraping, etc.
1670
R. M. SAUNDERS, H. G. WALKER, JR. AND G. 0.
o
O.D. at
530
E
f
1 4
1
1
8
12
// "
1 24
DIGESTION TIME (hours)
tion decreases sharply as the severity of the process treatment increases. Even though the method of starch granule isolation was not strictly quantitative, it was good enough to indicate the approximate distribution of intact granules. Isolated granular starch from each bran sample was digested with chick pancreas a-amylase before and after autoclaving. The results are shown in Figure 2. In all cases the intact starch granules were completely digested but at a slower rate than starch gelatinized by autoclaving. More important, however, intact granules from the pelleted material were digested enzymatically at a faster rate than those from the mash, indicating starch modification during steam pelleting. Because, however, the intact granules from the pellets still showed birefringence, we suggest that swelling or
mechanical damaging occurred during processing without actual gelatinization taking place. No difference in chemical composition between pelleted and non-pelleted feed has been reported in a previous study (Bolton, 1960). Proximate analysis of the samples in this study show only small differences as indicated in Table 2. Even though figures for protein, carbohydrate and fat remain essentially the same, it is quite possible that the availability (or digestibility) of these components can change during processing. This phenomenon has already been shown to occur in the case of protein (Saunders et al., 1968). Such is apparently the case with starch in steam-pelleting, since much of it is either gelatinized or altered. Overall starch digestion rate in mash was slower than in pellets, but final total digestion values were equal. This is not surprising since it has been previously reported that a-amylases are 165 to 7000 times more active on boiled starch than on raw starch (Reed and Thorn, 1964). The effect of rate of starch digestion on total starch utilization by a chick is not clear. Feeding experiments performed to clarify this point show that with all feeds, a few intact starch granules do pass through the digestive tract unaffected by amylase action. Table 3 lists the relative amounts of starch noted from microscopic examination of the intestinal and fecal contents of birds fed different bran feeds. Starch was present in all cases but in amounts too small to determine quantitatively. The relative
TABLE 2.—Proximate analysis of wheat bran mash and steam-pellets sample Mash Pellets
Starch
14.3 15.5
C
^°™ 23.70 24.18
% BUO 8.60 8.59
^
^
% fat
15.90 16.00
4.00 4.65
%
fiber
8.36 9.20
% ash
% suga
5.94 7.08
5.92 5.67
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
FIG. 2. Digestion with chick pancreas a-amylase of starch granules from mash and pellets, ....mash; —pellets; autoclaved starch granules from either mash or pellets.
KOHLER
SUGARS AND STARCH IN BRAN TABLE 3.—The relative amounts of starch visible after iodine staining in intestinal and fecal contents after feeding different brans to chicks Relative amount of starch Feed Mash Autoclaved mash Pellet
Intestinal
Fecal
++ + +
+++ + +
REFERENCES Adams, G. A., 1955. Constitution of hemicellulose from wheat bran. Can. J. Chem. 3 3 : 56-67. Arscott, G. H., 1967. Pelleting poultry rations. Animal Nutr. Health, 22(5) : 6, 8, 10. Badenhuizen, N. P., 1965. In Starch: Chemistry and Technology (edit, by R. L. Whistler and E. F. Paschall) vol. I. Academic Press: New York. pp. 80, 86. Bernfeld, P., 1955. In Methods in Enzymology
(edit, by S. P. Colowick and N. O. Kaplan) vol. I. Academic Press, New York. p. 149. Bolton, W., 1960. The digestibility of mash and pellets by chicks. J. Agr. Sci. 55: 141-142. Calet, G, 1965. The relative value of pellets versus mash and grain in poultry nutrition. World's Poultry Sci. J. 2 1 : 23-52. Cave, N. A. G., S. J. Slinger, J. D. Summers and G. C. Ashton, 1965. The nutritional value of wheat milling by-products for the growing chick. I. Availability of energy. Cereal Chem. 42: 523-532. Dubois, M., K. A. Gilles, J. K. Hamilton, P. A. Rebers and F. Smith, 1956. Colorimetric method for determination of sugars and related substances. Anal. Chem. 28: 350-356. Engel, C , 1947. The distribution of the enzymes in resting cereals. III. The distribution of esterase in wheat, rye, and barley. Biochim. Biophys. Acta, 1: 278-279. Hastings, W. H., and G. D. Miller, 1961. The effect of processing on biochemical changes in grains. Cereal Sci. Today, 6: 6-8. Laws, B. M., and J. H. Moore, 1963. Some observations on the pancreatic amylase and intestinal maltase of the chick. Can. J. Biochem. Phys'ol. 41: 2107-2121. Molyneux, H. M., 1930. National Institute of Poultry Husbandry, Harper Adams Agricultural College (England) Leaflet 16. Patton, J. W., H. H. Buskirk and L. A. Rauls, 1937. A study of the relative merits of pellets and mash poultry feeds. Vet. Med. 32: 423427. Reed, G., and J. A. Thorn, 1964. In Wheat: Chemistry and Technology (edit, by I. Hlynka) American Association of Cereal Chemists, Inc. St. Paul Minn. p. 410. Saunders, R. M., H. G. Walker and G. O. Kohler, 1968. The digestibility of steam-pelleted wheat bran. Poultry Sci. 47: 1636-1637. Saunders, R. M., and H. G. Walker, 1969. The sugars of wheat bran. Cereal Chem. 46: 85-92.
NEWS AND NOTES (Continued from page 1651) Other members of the U.S. Committee are: S. The Corresponding Secretaries are: B. Hitchner, Cornell University; J. McGinnis, Canada—Dr. J. F. Frank, Animal Diseases ReWashington State University; and W. Mellen, search Institute, Canada Department of AgriculUniversity of Massachusetts. ture, Hull, Quebec. Other Countries. In most countries nominations Australia—L. Hart, 260 Attonga Road, Yowie are invited early in the year. Bay, New South Wales 2228, Australia. (Continued on page 1694)
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amounts can only be compared within column headings; intestinal amounts cannot be compared with fecal amounts. More undigested starch was observed after feeding mash than after feeding pellets; pellets and autoclaved mash gave about the same amounts. But judging from these observations, the amount of undigested starch is very small in every case, so that overall starch utilization seems very good for all feeds. Thus, although steam-pelleting contributes to the efficiency of starch digestion by increasing its susceptibility to anxiolytic action, the effect is probably minimal insofar as being a factor in increasing the M.E. values when feeding pelleted rations to chicks.
1671
REFERENCES Allan, J. E., 1961. The determination of zinc in agricultural materials by atomic-absorption spectrophotometry. Analyst, 86: S30-S34. A. O. A. C , 1960. Official Methods of Analysis Association of Official Agricultural Chemists, Washington, D.C.
Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 11: 1-42. Kratzer, F. H., P. Vohra, R. L. Atkinson, P. N. Davis, B. J. Marshall and J. B. Allred, 1959a. Fractionation of soybean oil for growth and antiperotic factors. 1. Non-phospholipid nature of the factor. Poultry Sci. 38: 1049-1055. Kratzer, F. H., J. B. Allred, P. N. Davis, B. J. Marshall and P. Vohra, 1959b. The effect of autoclaving soybean protein and the addition of ethylene-diaminetetraacetic acid on the biological availability of dietary zinc for turkey poults. J. Nutrition, 82 : 313-322. Perkin-Elmer, 1966. No. 990-9341, Supplement to Analytical Methods for Atomic Absorption spectrophotometry. Perkin-Elmer Corp., Norwalk, Conn. Vohra, P., J. B. Allred, I. S. Gupta and F. H. Kratzer, 1959. Fractionation of soybean oil meal for growth and antiperotic factors. 2. Studies with genistin and soysterols. Poultry Sci. 38: 1476-1477. Vohra, P., and F. H. Kratzer, 1964. Influence of various chelating agents on the availability of zinc. J. Nutrition, 82: 249-256.
Sugars and Starch of Wheat Bran Mash and Steam-Pellets R. M. SAUNDERS, H. G. WALKER, JR. AND G. O. KOHLER Western Regional Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Albany, California 94710 (Received for publication May 8, 1969)
P
ELLETING poultry rations has been known for almost 40 years. Reports from England (Molyneaux, 1930) and the U. S. (Patton et al., 1937) were among the first to show increased body weight in chicks after pellet feeding when compared to mash feeding. Since that time, considerable research has been carried out in this field, but no adequate reasons have been discovered to completely account for the phenomenon (Calet, 1965). The obvious advantages and disadvantages of feeding pellets or mash have been listed (Calet, 1965; Arscott, 1967), but it is difficult to cite the actual physical or chemical changes
that occur during the steam-pelleting process that account for the large differences found experimentally in metabolizable energy (M.E.) values (Cave et al., 1965). This laboratory is studying the factors which contribute to these differences in observed M.E. values. One factor which seems to be involved is the rupture of aleurone cells during processing (Saunders et al., 1968). This communication reports that the digestion rate of wheat bran starch by chick cs-amylase increases after steam-pelleting. Similar observations about pelleting have been recorded by Hastings and Miller (1961) using other enzymes. However, our
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
better on a zinc-deficient CG-diet than on a SB-diet. EDTA improved the growth on both the diets but SPL was significantly growth promoting only on the CG-diet. The improvement in growth due to SPL in CG-diets was not due to any variations in the dietary Zn, Mn, Cu or Fe contents. The data on the effect of various treatments on mineral contents of tibia and liver are given. EDTA improved the growth by improving the availability of dietary zinc from both the diets. This is ruled out for SPL because no growth improvement was observed when SB-diet was used.
1667
1668
R. M. SAUNDERS, H. G. WALKER, JR. AND G. 0.
KOHLER
findings indicate that this factor is probably not a very important one in explaining observed M.E. differences.
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
ously shaken for 30 minutes with 150 ml. of 0.075M sodium chloride solution. The mixture was sieved through nylon mesh; the residue was reshaken for 5 minutes MATERIALS AND METHODS* with 75 ml. of water and again sieved. The A Canadian hard red spring wheat bran combined filtrates were centrifuged. The in both mash and steam-pelleted form was residual precipitate consisting of starch obtained from Dr. J. D. Summers of the granules and other grain debris was washed University of Guelph, Ontario, Canada. once with water and dried. Pellets manufactured in the laboratory Chick pancreas a-amylase was prepared were prepared in a commercial pellet mill as follows. Pancreas from 4-week old Corfrom mash that was conditioned at 180 to nish White Rock type cross-bred chicks 200°F. for 4 to 5 seconds before extrusion was removed and frozen at —30° until through a -fV m c h die, \\ inch thick. ready for use. The frozen tissue was hoThe sugars were isolated as follows: 25 mogenized in a Waring Blendor at 0° with g. of bran in 400 ml. of 70% aqueous etha- 10 volumes of acetone and centrifuged. The nol was heated under reflux for 1 hour. precipitate was washed twice with cold aceThe mixture was centrifuged and the resi- tone then dried in a desiccator over potasdue again treated under the same condi- sium hydroxide at 0°. The white powdery tions. The two supernatants were combined precipitate was sieved through a 60-mesh and concentrated to about 100 ml. The screen then stored at 0° in a desiccator. aqueous solution was twice extracted with The acetone powder was used in this form 200 ml. of chloroform then concentrated to in all digestions; the a-amylase activity did 20 ml. Sugars in the extract were separated not noticeably decrease over a 6-month peby paper chromatography on Whatman 3 riod under these storage conditions. The MM paper in the descending fashion in sol- amylase activity was 130 units where 1 vent n-butanol-pyridine-water (6:4:3,v/v), unit is expressed as mg. maltose produced and were detected with alkaline silver ni- by digestion of starch by 1 mg. of amylase trate. After separation, the spots or strips in 10 minutes (Laws and Moore, 1963). were eluted with water and the aqueous soStarch digestions with chick pancreas lution analyzed. Sugars were measured by a-amylase were carried out as follows: 60 the phenol-sulfuric acid procedure (Dubois mg. of the crude starch extract from the etal, 1956). bran sample in 5 ml. of 0.15M sodium Measurement of birefringence displayed chloride solution and 5 ml. of 0.04M soby intact starch granules, and staining with dium barbiturate solution, pH 7.0, was Congo Red of gelatinized starch granules treated with 12 mg. (unless otherwise specwere employed to determine the physical ified) of chick pancreas a-amylase preparanature of the starch (Badenhuizen, 1965). tion, 0.2 ml. of toluene was added. For autoNon-water-soluble intact starch granules claved samples the starch extract was auwere crudely isolated from the bran sam- toclaved for 20 minutes at 15 p.s.i.g., ples as follows: 10 g. of bran was vigor- cooled, then diluted with the same amounts of buffer mixture and amylase. The mixture * Reference to a company or product name does not imply approval or recommendation of the was incubated at 70° F. with continuous product by the U.S. Department of Agriculture to agitation. Starch digestion was followed by the exclusion of others that may be suitable. assaying increase in reducing sugar. A 1
1669
SUGARS AND STARCH IN BRAN
RESULTS AND DISCUSSION When aliquots of the sugars in mash and pellets were paper chromatographed and assayed, the distribution pattern shown in Figure 1 was obtained. Details on identification of the individual components have been reported previously (Saunders and Walker, 1969). Total sugars on a dry weight basis found in mash and steam-pellets were 6.48 and 6.20% respectively. With the exception of slightly more tetrasaccharide, xylose and glycerol in mash, the total sugars and their distribution are approximately the same in mash and steam-pellets. Xylose is a component of wheat bran hemicellulose (Adams, 1955) and possibly arises in mash from residual hemicellulase activity during storage. In a similar manner glycerol may arise by
E o
§
FRUCTOSANS FRUCTOSYlRAFFINOSE SIACHYOSE
PAPER CHROMATOGRAPHY INCREASING R, »
FIG. 1. Comparative sugar content of wheat bran mash and steam-pellets. Shaded area, mash; unshaded area, pellets.
residual lipase action since bran is rich in esterases (Engel, 1947). These enzymic activities are largely destroyed during steampelleting and hence lower amounts of xylose and glycerol are observed in pellets. The larger amount of tetrasaccharide in mash cannot be explained at this time. The minor differences found in kinds and amounts of sugars in mash and pellets are so small that they could not have any appreciable effect on the overall M.E. values. About 96% of the starch granules in the mash showed birefringence and were negative to Congo Red staining (i.e. intact granules). In steam-pelleted material only about 30% of the starch granules were intact. After autoclaving, the number of the intact granules decreased markedly but a few showing birefringence always remained. Typical values are given in Table 1 for isolation of intact starch from mash and pellets. The weight of the intact fracTABLE 1.—Starch granules isolated from autoclaved and non-autoclaved bran samples Bran sample Mash Pellet Autoclaved mash Autoclaved pellet
Starch (g.) isolated as intact granules from 10 g. bran 0.68 0.42 0.21 0.08
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
ml. aliquot was removed and diluted with 2 ml. each of water and dinitrosalicylate reagent, then heated for 10 minutes at 100°C. The solution was cooled, diluted to 25 ml. with distilled water and O.D. measured at 530 mil,. (Bernfeld, 1955). Pure wheat starch was used as a digestion standard. Wheat bran used in chick feeding experiments was obtained from the Midwest. Four- to eight-weeks-old Arbor-Acre White Rock chicks in groups of three previously maintained on a commercial diet were starved for 20 hours then fed ad libitum the following wheat bran ration: (a) mash; (b) mash preautoclaved at 15 p.s.i.g. for 20 minutes, and (c) steam-pellets manufactured in this laboratory. After 24 hours the chicks were killed. Microscopic examination of the lower small intestinal content and fecal droppings was carried out to determine the fate of the bran starch. Care was taken to avoid contamination of the fecal droppings by feed scatterings, beak scraping, etc.
1670
R. M. SAUNDERS, H. G. WALKER, JR. AND G. 0.
o
O.D. at
530
E
f
1 4
1
1
8
12
// "
1 24
DIGESTION TIME (hours)
tion decreases sharply as the severity of the process treatment increases. Even though the method of starch granule isolation was not strictly quantitative, it was good enough to indicate the approximate distribution of intact granules. Isolated granular starch from each bran sample was digested with chick pancreas a-amylase before and after autoclaving. The results are shown in Figure 2. In all cases the intact starch granules were completely digested but at a slower rate than starch gelatinized by autoclaving. More important, however, intact granules from the pelleted material were digested enzymatically at a faster rate than those from the mash, indicating starch modification during steam pelleting. Because, however, the intact granules from the pellets still showed birefringence, we suggest that swelling or
mechanical damaging occurred during processing without actual gelatinization taking place. No difference in chemical composition between pelleted and non-pelleted feed has been reported in a previous study (Bolton, 1960). Proximate analysis of the samples in this study show only small differences as indicated in Table 2. Even though figures for protein, carbohydrate and fat remain essentially the same, it is quite possible that the availability (or digestibility) of these components can change during processing. This phenomenon has already been shown to occur in the case of protein (Saunders et al., 1968). Such is apparently the case with starch in steam-pelleting, since much of it is either gelatinized or altered. Overall starch digestion rate in mash was slower than in pellets, but final total digestion values were equal. This is not surprising since it has been previously reported that a-amylases are 165 to 7000 times more active on boiled starch than on raw starch (Reed and Thorn, 1964). The effect of rate of starch digestion on total starch utilization by a chick is not clear. Feeding experiments performed to clarify this point show that with all feeds, a few intact starch granules do pass through the digestive tract unaffected by amylase action. Table 3 lists the relative amounts of starch noted from microscopic examination of the intestinal and fecal contents of birds fed different bran feeds. Starch was present in all cases but in amounts too small to determine quantitatively. The relative
TABLE 2.—Proximate analysis of wheat bran mash and steam-pellets sample Mash Pellets
Starch
14.3 15.5
C
^°™ 23.70 24.18
% BUO 8.60 8.59
^
^
% fat
15.90 16.00
4.00 4.65
%
fiber
8.36 9.20
% ash
% suga
5.94 7.08
5.92 5.67
Downloaded from http://ps.oxfordjournals.org/ by guest on April 18, 2015
FIG. 2. Digestion with chick pancreas a-amylase of starch granules from mash and pellets, ....mash; —pellets; autoclaved starch granules from either mash or pellets.
KOHLER
SUGARS AND STARCH IN BRAN TABLE 3.—The relative amounts of starch visible after iodine staining in intestinal and fecal contents after feeding different brans to chicks Relative amount of starch Feed Mash Autoclaved mash Pellet
Intestinal
Fecal
++ + +
+++ + +
REFERENCES Adams, G. A., 1955. Constitution of hemicellulose from wheat bran. Can. J. Chem. 3 3 : 56-67. Arscott, G. H., 1967. Pelleting poultry rations. Animal Nutr. Health, 22(5) : 6, 8, 10. Badenhuizen, N. P., 1965. In Starch: Chemistry and Technology (edit, by R. L. Whistler and E. F. Paschall) vol. I. Academic Press: New York. pp. 80, 86. Bernfeld, P., 1955. In Methods in Enzymology
(edit, by S. P. Colowick and N. O. Kaplan) vol. I. Academic Press, New York. p. 149. Bolton, W., 1960. The digestibility of mash and pellets by chicks. J. Agr. Sci. 55: 141-142. Calet, G, 1965. The relative value of pellets versus mash and grain in poultry nutrition. World's Poultry Sci. J. 2 1 : 23-52. Cave, N. A. G., S. J. Slinger, J. D. Summers and G. C. Ashton, 1965. The nutritional value of wheat milling by-products for the growing chick. I. Availability of energy. Cereal Chem. 42: 523-532. Dubois, M., K. A. Gilles, J. K. Hamilton, P. A. Rebers and F. Smith, 1956. Colorimetric method for determination of sugars and related substances. Anal. Chem. 28: 350-356. Engel, C , 1947. The distribution of the enzymes in resting cereals. III. The distribution of esterase in wheat, rye, and barley. Biochim. Biophys. Acta, 1: 278-279. Hastings, W. H., and G. D. Miller, 1961. The effect of processing on biochemical changes in grains. Cereal Sci. Today, 6: 6-8. Laws, B. M., and J. H. Moore, 1963. Some observations on the pancreatic amylase and intestinal maltase of the chick. Can. J. Biochem. Phys'ol. 41: 2107-2121. Molyneux, H. M., 1930. National Institute of Poultry Husbandry, Harper Adams Agricultural College (England) Leaflet 16. Patton, J. W., H. H. Buskirk and L. A. Rauls, 1937. A study of the relative merits of pellets and mash poultry feeds. Vet. Med. 32: 423427. Reed, G., and J. A. Thorn, 1964. In Wheat: Chemistry and Technology (edit, by I. Hlynka) American Association of Cereal Chemists, Inc. St. Paul Minn. p. 410. Saunders, R. M., H. G. Walker and G. O. Kohler, 1968. The digestibility of steam-pelleted wheat bran. Poultry Sci. 47: 1636-1637. Saunders, R. M., and H. G. Walker, 1969. The sugars of wheat bran. Cereal Chem. 46: 85-92.
NEWS AND NOTES (Continued from page 1651) Other members of the U.S. Committee are: S. The Corresponding Secretaries are: B. Hitchner, Cornell University; J. McGinnis, Canada—Dr. J. F. Frank, Animal Diseases ReWashington State University; and W. Mellen, search Institute, Canada Department of AgriculUniversity of Massachusetts. ture, Hull, Quebec. Other Countries. In most countries nominations Australia—L. Hart, 260 Attonga Road, Yowie are invited early in the year. Bay, New South Wales 2228, Australia. (Continued on page 1694)
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amounts can only be compared within column headings; intestinal amounts cannot be compared with fecal amounts. More undigested starch was observed after feeding mash than after feeding pellets; pellets and autoclaved mash gave about the same amounts. But judging from these observations, the amount of undigested starch is very small in every case, so that overall starch utilization seems very good for all feeds. Thus, although steam-pelleting contributes to the efficiency of starch digestion by increasing its susceptibility to anxiolytic action, the effect is probably minimal insofar as being a factor in increasing the M.E. values when feeding pelleted rations to chicks.
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