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Influence of Infrared (Micronization) Treatment on the Nutritional Value of Corn and Low- and High-Tannin Sorghum1,2
Influence of Infrared (Micaronization) Treatment on the Nutritional Value of Corn and Low- and High-Tannin Sorghum 1 - 2 J. H. DOUGLAS and T. W. SULLIVAN3 Department of Animal Science, University of Nebraska, Lincoln, Nebraska 68583-0908 R. ABDUL-KADIR and J. H. RUPNOW Department of Food Science and Technology, University of Nebraska, Lincoln, Nebraska 68583-0919 (Received for publication November 30, 1990)
1991 Poultry Science 70:1534-1539 INTRODUCTION
Grain sorghum and corn are fed to poultry primarily for their starch energy value. However, sorghum starch is reported to be less accessible to enzymatic degradation than cornstarch (Rooney and Pflugfelder, 1986). Starch digestibility is affected by the composition of starch, protein and starch interaction, and antinutritional factors such as enzymes inhibitors, phytates, lectins, and tannins (Thorne et al., 1983; Dreher et al, 1984). The starch granules of normal corn and sorghum are very similar in size, shape, and composition (Rooney and Pflugfelder, 1986). Sorghum has a high concentration of protein bodies in the peripheral endosperm area, making the starch unavailable for enzymatic degradation (Sullins and Rooney, 1975). Endosperm starch and protein appear to adhere
'Published as Paper 9426, Journal Series, Nebraska Agricultural Research Division, Lincoln, NE, 68583-0908. ^Research supported in part by the Nebraska Corn Development, Utilization, and Marketing Board. 3 To whom correspondence should be addressed.
more tightly in sorghum than in com. This is very important because intermolecular crosslinks (cross-linked kafirins) found in sorghum prolamines decrease digestibility of sorghum protein and the starch embedded in it (Rooney and Pflugfelder, 1986). Processing methods that produce a change in the organization of the sorghum grain kernel to release starch granules from the protein matrix offer promise of increasing carbohydrate utilization (McNeill et al, 1975). Micronization is a dry-heat process using infrared gas generators to heat the grain to about 149 C. Gelatinization of the starch is performed utilizing only the inherent moisture of the grain. The protein matrix of the kernel is disrupted and many of the starch granules are ruptured and adhere together, forming sheets (Harbers, 1975). Savage et al. (1980) reported that micronization increased in vitro starch availability of high-tannin sorghum (HTS) and improved apparent digestibility of dry matter and nitrogen retention by growing pigs. Starch of micronized sorghum was significantly more susceptible to enzymatic degradation by amyloglucosidase than starch of untreated
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ABSTRACT The effects of micronization (infrared treatment) of corn, low (LTS), and high tannin sorghum (HTS) was studied. Micronization decreased acid and neutral detergent fiber of the grains. Arginine was reduced in corn, LTS, and HTS and Lys was reduced in com. Tannin contents of untreated LTS, micronized, LTS, untreated HTS, and micronized HTS expressed as percentage catechin equivalents on a dry matter basis were .06, .05,5.6, and 4.1 %, respectively. The decrease in tannin content of HTS due to micronization was not enough to alleviate the depressing effects of tannin on weight gain (WG) and feed conversion (FC) of broilers. In vitro starch digestibility was improved for all grains. Broiler performance was evaluated in a feeding trial that involved a 2 x 3 factorial arrangement of grain processing and grain sources. No interactions among method of grain processing and grain sources for either WG or FC were observed. Micronization improved WG and FC for all grains. Birds fed com and LTS showed no differences in WG and FC. There were reductions in WG and FC of birds fed HTS as compared with those fed LTS. Micronization of grains improved the performance of broilers. (Key words: corn, sorghum, tannin, micronization, broilers)
MICRONIZATION OF CEREAL GRAINS
ground sorghum (McNeill et al, 1975). The objectives of the present research were 1) to determine the effect of micronization on chemical composition, tannin content, and feeding value of com, low-tannin sorghums (LTS), and HTS for broilers, and 2) to determine the effect of micronization on in vitro starch digestibility of corn, LTS, and HTS. MATERIALS AND METHODS
4 Pioneer 8333 from Pioneer Hi-Bred International, Inc..Lincoln, NE 68505. ^ e K a l b BR-64 from DeKalb-Pfizer Genetics, Lubbock, TX 79415. 6 Flakee Mills, Lincoln, NE 68524. 7 Parr Instrument Co., Moline, EL 61265. ^iazyme L-200, Mills Laboratories, Elkhart, IN 46515. 9 Technicon Instruments Corp., Tarrytown, NY 10591.
Hare, 1975). Norleucine was used as an internal standard. For analysis of sulfur amino acids, samples were oxidized before hydrolysis using the procedure described by Moore (1963). Methionine was oxidized to methionine sulfone and Cys to cysteic acid. These amino acids were then determined by the same procedure as unoxidized hydrolyzates. Starch in grain samples was determined as alpha-linked glucose polymers according to the procedure of Poore, 1989 (personal communication). This procedure, routinely used in the authors' laboratory, has been very consistent in quantitative recovery of starch from cornstarch, corn, and sorghum standards. Total starch in the grain was determined using a .2-g sample of cleaned, ground grain weighed into a 15-mL screw-cap test tube. The sample was suspended in 2 mL CaCl2 solution (25% wt/ vol, pH 2.0) for 1 h. The samples were autoclaved at 121 C for 1 h, and then allowed to cool to at least 60 C. When the test tubes had cooled sufficiently, 8 mL of an enzyme solution8 in .1 M acetate buffer (pH 4.2), was added and the samples were incubated for 16 h at 60 C. The samples were rinsed into 100 mL volumetric flasks and brought to volume with .2% (wt/vol) benzoic acid. An aliquot was centrifuged at 3,000 x g for 10 min. Analysis for glucose was conducted using an automated procedure.9 Starch content was calculated by multiplying the glucose concentration by .9. In determining the in vitro starch digestibility, the same procedure was used except that pregelatinization (autoclaving) was omitted, samples were incubated for 2, 4, 8, 12, and 16 h, and the reaction was terminated by the addition of 1.5 mL 10% H 2 S0 4 . The feeding trial involved 360 Vantress x Arbor Acres broilers. Chicks were randomly assigned to six dietary treatments in a 2 x 3 factorial arrangement of variables using a completely randomized design. Each treatment was replicated 10 times with six birds (three males and three females) per replicate pen. The main effects were method of grain processing and grain source. The two methods of grain processing were untreated and ground or micronized and ground. Grains were ground through a hammer mill that had a full circle screen with ,48-cm round holes. Micronized grains appeared to have more uniform particle size than unmicronized grain after grinding. Grain sources were corn, LTS, and HTS.
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Commercial LTS 4 and HTS 5 were produced at the University of Nebraska Agricultural Research and Development Center, Mead, NE in 1988. The yellow corn was obtained from the University of Nebraska Agronomy farm. Tap water was added to 450 kg of each grain in a horizontal mixer to reconstitute to about 18% moisture. Grains were tempered overnight in multiwall paper bags to allow the added moisture to equilibrate. Tempered grains were micronized (infrared heated) to 150 C for 3 min in a 704 C Infraionizer.6 Infrared heating was immediately followed by a thin flaking process. Grain samples were analyzed for protein, lipid (ether extract), ash, Ca, and P by the methods of the Association of Official Analytical Chemists (1984). Acid detergent fiber (ADF; Van Soest, 1963), and neutral detergent fiber (NDF; Van Soest and Marcus, 1964) were also determined. Tannin content was determined using the vanillin HC1 method (Burns, 1971). The gross energy (GE) content of the grains was measured using an adiabatic bomb calorimeter.7 Grain samples were hydrolyzed at 110 C in a N atmosphere for 20 h in preparation for amino acid analysis. Amino acids of hydrolyzates were then separated by HPLC using ion-exchange column and lithium buffers as eluants. Amino acids were detected and measured fluorometrically using o-phthaldehyde postcolumn derivatization (Benson and
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DOUGLAS ET AL.
TABLE 1. Composition and calculated nutrient levels of diets fed from 1 to 21 days o\
Ingredients and calculated composition 1
Percentage 53.0 37.5 4.5 2 1.9 1.3 .4 1.2 100.0 3,041 22.6 .93 1.31 1.0 .5
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Corn, low-, or high-tannin sorghum in either ground or micronized then ground form. 2 Premix furnished the following per kilogram of diet vitamin A, 11,000 IU; vitamin D 3 , 4,400 IU; menadione sodium bisulfite, 3.3 mg; vitamin E, 11 IU; riboflavin, 6.6 mg; calcium pantothenate, 11.9 mg; niacin, 77 mg; dbiotin, .11 mg; folacin, .66 mg; B12, .011 mg; choline chloride, 880 mg; copper, 10 mg; iron, 100 mg; manganese, 100 mg; zinc, 100 mg; iodine, 3.0 mg; cobalt, 1.0 mg; calcium, 92 mg; and selenium, 2 mg.
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I Composition of diets are presented in Table 1. Sorghums replaced corn on an equal weight basis. Protein and metabolizable energy of the diets varied in accordance with the grain and method of processing. Birds were maintained in electrically heated, Petersime10 starting batteries with raised wire floors from 1 to 21 days. Feed and water were provided for ad libitum consumption. Starch digestibility was calculated as (solubilized starch •*• total grain starch) x 100. In vitro starch digestibility was determined by calculating multiple linear regression equations with the PROC REG procedure of SAS® (SAS Institute, 1985), with digestibility (Y) as the dependent variable and time (X) as the independent variable. Feeding trial data were analyzed as a 2 x 3 factorial arrangement using the General Linear Models procedure (SAS Institute, 1985). Treatment means were sepa-
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Grain Soybean meal (47.5% CP) Animal fat DL-methionine (99%) Dicalcium phosphate Ground limestone Sodium chloride Premix2 Total Calculated composition ME, kcal/kg CP Methionine and cystine Lysine Calcium Available phosphorus
-H-H-H-H-H-H-H-H-H-H
MICRONIZATION OF CEREAL GRAINS
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TABLE 3. Effect of micronization on amino acid profile of corn, low-, and high-tannin sorghum1
CP, %
Untreated
10.0 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.35 .15 .05 .06 .04 .03 .01 .09 .06 .09 .19 .02 .04 .04 .03 .38
5.9 2.6 4.2 2.7 35 12.5 2.1 2.0 3.4 4.6 2.7 3.3 4.2 5.9 18.0 6.1
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.05 .09 .01 .07 .01 .05 .02 .05 .13 .05 .05 .03 .09 .10 .25 .01
Micronized
Untreated
Untreated
9.9
9.6
9.8
4.8 2.8 4.1 2.0 32 10.5 2.3 2.0 2.2 4.2 2.3 3.2 4.0 6.1 16.5 7.0
on a DM b 3.1 ± .07 3.1 ± .02 3.6 ± .04 2.2 ± .01 3.7 ± .04 11.6 ± .13 2.3 ± .06 2.2 ± .07 2.9 ± .06 4.6 ± .22 2.5 ± .11 2.9 ± .07 4.5 ± .03 6.0 ± .06 17.4 ± .35 8.4 ± .06
4.4 2.8 4.2 2.1 3.4 10.7 2.1 1.9 1.9 42 2.3 3.2 42 6.0 17.1 7.3
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
CP .04 .06 .11 .02 .03 .28 .02 .18 .07 .10 .02 .10 .08 .17 .62 .30
Micronized 9.7
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.20 .03 .02 .04 .06 .15 .02 .07 .08 .08 .07 .01 .16 .04 .30 .12
3.0 2.9 3.5 2.1 3.8 11.5 2.1 2.5 2.8 4.6 2.3 2.9 4.5 5.9 17.5 8.0
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.07 .11 .09 .05 .04 .12 .08 .29 .01 .04 .14 .14 .04 .08 .01 .52
Values are the x ± SD of two determinations per sample
rated using single degree of freedom preplanned nonorthogonal contrasts (Steel and Torrie, 1980). RESULTS AND DISCUSSION
The results of the chemical composition analyses are presented in Table 2. Micronization decreased the ADF and NDF content regardless of the grain source. Micronization slightly decreased the lipid content and GE value of com. Tannin contents (expressed as
percentage catechin equivalents on a dry matter basis) of untreated LTS, micronized LTS, untreated HTS, and micronized HTS, were .06, .05, 5.6, and 4.1%, respectively. Amino acid profiles of untreated and micronized com, LTS, and HTS, expressed as percentage of protein on a DM basis, are presented in Table 3. Proline was not reported because it does not react with o-phthaldehyde unless it is oxidized first. Com, LTS, and HTS had minor differences in their protein and amino acid composition. Micronization caused
TABLE 4. In vitro starch digestibility with glucoamylase1,2 Corn
Low-tannin sorghum
Hours
Untreated3
Micronized4
2 4 8 12 16
50.3 59.2 67.2 77.8 80.5
88.6 94.4 95.2 98.1 97.1
± .99 ± 4.01 ± 1.13 ± .01 ± 1.46
± ± ± ± ±
.83 .34 .20 .11 .64
High-tannin sorghum
Untreated5
Micronized6
Untreated7
Micronized8
44.7 60.0 64.1 78.3 81.7
70.4 82.1 82.9 93.2 93.2
50.3 62.7 68.1 78.5 80.4
76.4 85.2 85.7 94.1 93.5
± .02 ± 1.54 ± 2.33 ± 1.77 ± .62
± 22 ± 1.26 ± .88 ± 1.04 ± .32
± 1.88 ± 1.55 ± .67 ± .74 ± 1.29
± .66 ± 155 ± 1.69 ± .30 ± .86
'Values are the x ± SD of two determinations per sample. Percentage starch was calculated as (solubilized starch + total grain starch) x 100. 3 Regression equation Y = 43.15 + 4.09XJ - .073X2 (r2 = .96), where Y is starch digestibility and X is time in minutes. ''Regression equation Y = 86.73 + 1.82X! - .074X2 (r2 = .77), where Y is starch digestibility and X is time in minutes. ^Regression equation Y = 38.74 + 4.63Xj - .12X2 (r2 = .94), where Y is starch digestibility and X is time in minutes. degression equation Y = 6650 + 3.33Xj - .10X2 (r2 = .89), where Y is starch digestibility and X is time in minutes. 'Regression equation Y = 43.85 + 4.38Xj - .13X2 (r2 = .95), where Y is starch digestibility and X is time in minutes. degression equation Y = 72.97 + 2.60XX - .08X2 (r 2 = .88), where Y is starch digestibility and X is time in minutes.
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6.4 3.1 4.2 2.8 3.3 11.0 2.8 2.1 3.4 4.5 3.0 3.4 4.3 6.3 16.9 6.1
Arg Gly Ser His lie Leu Lys Met Cys Phe Tyr Thr Val Asp Glu Ala
Micronized
10.3
High-tannin. sorghum
Low-tannin sorghum
Com Amino acid
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DOUGLAS ET AL. TABLE 5. Effect of micronization and grain source on weight gain, feed conversion, and feed intake of broilers, 1 to 21 days of age Grain source
Measurement Weight gain,1 g Untreated Micronized X
Feed conversion,2 g:g Untreated Micronized X
X
High-tannin sorghum
541 584 562
556 584 570
510 552 530
1.57 1.49 1.53 848 870 855
1.54 1.51 1.52 854 882 868
1.58 1.55 1.56 805 855 830
X
CV
536 573
6.3
1.56 1.52
836 869
3.9
5.6
Grain treatment by grain source interaction (P>.80); micronized versus untreated (P-c.0006); corn versus low-tannin (LTS) sorghum (P>.55); LTS sorghum versus high-tannin (HTS) sorghum (P<003). Grain treatment by grain source interaction (P>.39); micronized versus untreated (P<005); com versus LTS sorghum (P>.80); LTS sorghum versus HTS sorghum (P<08). 3 Grain treatment by grain source interaction (P>.76); micronized versus untreated (P<.02); corn versus LTS sorghum (P>.46); LTS sorghum versus HTS sorghum (P<03).
minor alterations in the amino acid profiles of the grains. The Arg in corn, LTS, and HTS and Lys in corn were decreased by this treatment. In contrast, the Cys level in micronized LTS and HTS was higher than in untreated LTS and HTS. The result of Diazyme L-200 (glucoamylase) hydrolysis is a quantitative conversion of starch polymers to glucose. Starch that has been gelatinized or disrupted is more rapidly degraded by the enzyme than untreated starch (McNeill et al, 1975). Results of in vitro digestibility with glucoamylase are presented in Table 4. Micronization improved in vitro starch digestibility regardless of grain source. Starch of micronized corn was more susceptible to glucoamylase during the first 8 h of incubation than starch of micronized LTS and HTS. In vitro starch digestibility of untreated corn, LTS, and HTS was not different. This was not expected because sorghum tannins reportedly cause inhibition of a-amylase in vitro (Miller and Kneen, 1947; Strumeyer and Malin, 1969; Maxon et al, 1973; Daiber, 1975; Reichert et al, 1980; Mitaru and Blair, 1984). However, Daiber (1975) suggested that the enzymatic inhibition by tannins might be dependent on their quantity as well as quality and nature. Furthermore, they reported that the tannins assayed by the vanillin HCl procedure
(used in the present study) are of the anthocyanogens type and are not enzyme inhibiting. Weight gain, FC, and feed intake data are presented in Table 5. Because there were no interactions among grain sources and method of grain processing for WG (P>.80), FC (P>.39), and feed intake (P>.76) only the main effects will be considered. Birds fed corn and LTS showed no differences in WG (P>.55) and FC (P>.80). There were reductions in WG (P<003) and FC (P<08) of birds fed HTS compared with those fed LTS. The poor performance of broilers fed HTS is in agreement with the reports of Armstrong et al. (1973), Featherston and Rogler (1975), Nelson et al. (1975), Elkin et al. (1978a,b), Rogler and Sell (1984), and Rogler et al. (1985). Regardless of the grain source, micronization improved WG (P<0006), FC (P<005), and feed intake (P<.02). The improvement in WG and FC could be related to the increase in feed intake and to the rapid availability of starch during the early hours of digestion. Also, in vitro starch digestibility of untreated grain after 16 h was still lower than micronized grain (Table 4). Savage and Clark (1988) reported that micronization of HTS significantly improved apparent digestible energy but remained lower than LTS. Micronization did
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Feed intake, g Untreated Micronized
Corn
Low-tannin sorghum
MICRONIZATION OF CEREAL GRAINS
REFERENCES Armstrong, W. D., W. R. Featherston, and J. C. Rogler, 1973. Influence of methionine and other dietary additions on the performance of chicks fed bird resistant sorghum grain diet. Poultry Sci. 52: 1592-1599. Association of Official Analytical Chemists, 1984. Pages 153-336 in: Methods of Analysis. 14th ed. Association of Official Analytical Chemists, Washington, DC. Benson, J. R., and P. E. Hare, 1975. 0-Phthaldehyde fluorogenic detection of primary amines in the picomole range: comparison with fluorescamine and ninhydrin. Proc. Natl. Acad. Sci. 72:619-622. Burns, R. E., 1971. Method for estimation of tannin in sorghum grain. Agron. J. 63:511-512. Daiber, K. H., 1975. Enzyme inhibition by polyphenols of sorghum grain and malt J. Sci. Food Agric. 26: 1399-1411. Dreher, M L., C. J. Dreher, and J. W. Berry, 1984. Starch digestibility of foods: A nutritional perspective. CRC Crit. Rev. Food Sci. Nutr. 20:47-71. Elkin, R. G., W. R. Featherston, and J. C. Rogler, 1978a. Investigations of leg abnormalities in chicks consuming high tannin sorghum grain diets. Poultry Sci. 57: 757-762. Elkin, R. G., J. C. Rogler, and W. R. Featherston, 1978b. Influence of sorghum grain tannins on methionine utilization in chicks. Poultry Sci. 57:704-710. Featherston, W. R., and J. C. Rogler, 1975. Influence of tannins on the utilization of sorghum grain by rats and chicks. Nutr. Rep. Int 11:491-497. Harbers, L. H., 1975. Starch granule structural changes and amylolytic patterns in processed sorghum grain. J. Anim. Sci. 41:1496-1501. Maxon, E. D., L. W. Rooney, R. W. Lewis, L. E. Clark, and J. W. Johnson, 1973. The relationship between tannin content, enzyme inhibition, the rat performance and characteristics of sorghum grain. Nutr. Rep.
Int 8:145-152. McNeill, J. W., G. D. Potter, J. K. Riggs, and L. W. Rooney, 1975. Chemical and physical properties of processed sorghum grain carbohydrates. J. Anim. Sci. 40:335-341. Miller, B. S., and E. Kneen, 1947. The amylase inhibitor of leoti sorghum. Arch. Biochem. Biophys. 15: 251-264. Mitaru, B. N., and R. Blair, 1984. Comparative effects of cooking and high moisture storage of sorghums on protein digestibility in rats. Nutr. Rep. Int. 30: 397-^105. Moore, S., 1963. On the determination of Cystine as cystic acid. J. Biol. Chem. 238:235-237. Nelson, T. S., E. L. Stephenson, A. Burgos, J. Floyd, and J. O. York, 1975. Effect of tannin content and dry matter digestion on energy utilization and average amino acid availability of hybrid sorghum grains. Poultry Sci. 54:1620-1623. Reichert, R. D., S. E. Fleming, and D. J. Schwab, 1980. Tannin deactivation and nutritional improvement of sorghum by anaerobic storage of H2O-, HC1-, or NaOH-treated grains. X. Agric. Food Chem. 28: 824-829. Rogler, J. C , HJIJR. Ganduglia, and R. G. Elkin, 1985. Effects of nitrogen source and level on the performance of chicks and rats fed low and high tannin sorghum. Nutr. Res. 5:1143-1151. Rogler, J. C , and D. R. Sell, 1984. Effects of stage of maturity on the tannin content and nutritional quality of low and high tannin sorghum. Nutr. Rep. Int. 29: 1281-1287. Rooney, L. W., and R. L. Pflugfelder, 1986. Factors affecting starch digestibility with special emphasis on sorghum and com. J. Anim. Sci. 63:1607-1623. SAS Institute, 1985. SAS® User's Guide: Statistics. SAS Institute, Inc., Cary, NC. Savage, G. P., and A. Clark, 1988. The effect of micronization on the nutritional value of yellow and brown sorghum. Nutr. Rep. Int 37:829-837. Savage, G. P., W. C. Smith, and P. A. Briggs, 1980. A note on the influence of micronization and polyethylene glycol on the nutritional value of brown sorghum for growing pigs. Anim. Prod. 30:157-160. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics: A Biometrical Approach. 2nd. ed. McGraw Hill Book Co., New York, NY. Strumeyer, D. H., and M. J. Malin, 1969. Identification of the amylase inhibitor from seeds of leoti sorghum. Biochim. Biophys. Acta 184:643-645. Sullins, R. D., and L. W. Rooney, 1975. Light and scanning electron microscopic studies of waxy and nonwaxy endosperm sorghum varieties. Cereal Chem. 52:361-366. Thome, M. J., L. TJ. Thompson, and D J A . Jenkins, 1983. Factors affecting starch digestibility and the glycemic response with special reference to legumes. Am. J. Clin. Nutr. 34:481-488. Van Soest, P. J., 1963. Use of detergents in the analysis of fibrous feeds. II. A rapid method for the determination of fiber and lignin. J. Assoc. Off. Agric. Chem. 46:829-835. Van Soest P- J-, and W. C. Marcus, 1964. Methods for the determination of cell wall constituents in forages using detergents and the relationship between this fraction and voluntary intake and digestibility. J. Dairy Sci. 47:704.
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not decrease the assayable tannin (Table 2), which may be why feeding micronized HTS resulted in poorer WG and FC (Table 5) in the present research as well as in the results reported by Savage and Clark (1988). The present results indicate that LTS is equal to corn in nutritive value when fed to broilers. Micronization does not seem to alter the chemical composition and amino acid profile of the grain. Regardless of the grain source, micronization did increase the in vitro starch digestibility. Micronization did not decrease the assayable tannins. Improvement in grains due to micronization are consistent based on results of the current study and previous research. These improvements may or may not be economically justifiable in the future. Various cost factors involved and the manner in which grains and grain products are used will determine future trends in processing.
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1991 Poultry Science 70:1534-1539 INTRODUCTION
Grain sorghum and corn are fed to poultry primarily for their starch energy value. However, sorghum starch is reported to be less accessible to enzymatic degradation than cornstarch (Rooney and Pflugfelder, 1986). Starch digestibility is affected by the composition of starch, protein and starch interaction, and antinutritional factors such as enzymes inhibitors, phytates, lectins, and tannins (Thorne et al., 1983; Dreher et al, 1984). The starch granules of normal corn and sorghum are very similar in size, shape, and composition (Rooney and Pflugfelder, 1986). Sorghum has a high concentration of protein bodies in the peripheral endosperm area, making the starch unavailable for enzymatic degradation (Sullins and Rooney, 1975). Endosperm starch and protein appear to adhere
'Published as Paper 9426, Journal Series, Nebraska Agricultural Research Division, Lincoln, NE, 68583-0908. ^Research supported in part by the Nebraska Corn Development, Utilization, and Marketing Board. 3 To whom correspondence should be addressed.
more tightly in sorghum than in com. This is very important because intermolecular crosslinks (cross-linked kafirins) found in sorghum prolamines decrease digestibility of sorghum protein and the starch embedded in it (Rooney and Pflugfelder, 1986). Processing methods that produce a change in the organization of the sorghum grain kernel to release starch granules from the protein matrix offer promise of increasing carbohydrate utilization (McNeill et al, 1975). Micronization is a dry-heat process using infrared gas generators to heat the grain to about 149 C. Gelatinization of the starch is performed utilizing only the inherent moisture of the grain. The protein matrix of the kernel is disrupted and many of the starch granules are ruptured and adhere together, forming sheets (Harbers, 1975). Savage et al. (1980) reported that micronization increased in vitro starch availability of high-tannin sorghum (HTS) and improved apparent digestibility of dry matter and nitrogen retention by growing pigs. Starch of micronized sorghum was significantly more susceptible to enzymatic degradation by amyloglucosidase than starch of untreated
1534
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ABSTRACT The effects of micronization (infrared treatment) of corn, low (LTS), and high tannin sorghum (HTS) was studied. Micronization decreased acid and neutral detergent fiber of the grains. Arginine was reduced in corn, LTS, and HTS and Lys was reduced in com. Tannin contents of untreated LTS, micronized, LTS, untreated HTS, and micronized HTS expressed as percentage catechin equivalents on a dry matter basis were .06, .05,5.6, and 4.1 %, respectively. The decrease in tannin content of HTS due to micronization was not enough to alleviate the depressing effects of tannin on weight gain (WG) and feed conversion (FC) of broilers. In vitro starch digestibility was improved for all grains. Broiler performance was evaluated in a feeding trial that involved a 2 x 3 factorial arrangement of grain processing and grain sources. No interactions among method of grain processing and grain sources for either WG or FC were observed. Micronization improved WG and FC for all grains. Birds fed com and LTS showed no differences in WG and FC. There were reductions in WG and FC of birds fed HTS as compared with those fed LTS. Micronization of grains improved the performance of broilers. (Key words: corn, sorghum, tannin, micronization, broilers)
MICRONIZATION OF CEREAL GRAINS
ground sorghum (McNeill et al, 1975). The objectives of the present research were 1) to determine the effect of micronization on chemical composition, tannin content, and feeding value of com, low-tannin sorghums (LTS), and HTS for broilers, and 2) to determine the effect of micronization on in vitro starch digestibility of corn, LTS, and HTS. MATERIALS AND METHODS
4 Pioneer 8333 from Pioneer Hi-Bred International, Inc..Lincoln, NE 68505. ^ e K a l b BR-64 from DeKalb-Pfizer Genetics, Lubbock, TX 79415. 6 Flakee Mills, Lincoln, NE 68524. 7 Parr Instrument Co., Moline, EL 61265. ^iazyme L-200, Mills Laboratories, Elkhart, IN 46515. 9 Technicon Instruments Corp., Tarrytown, NY 10591.
Hare, 1975). Norleucine was used as an internal standard. For analysis of sulfur amino acids, samples were oxidized before hydrolysis using the procedure described by Moore (1963). Methionine was oxidized to methionine sulfone and Cys to cysteic acid. These amino acids were then determined by the same procedure as unoxidized hydrolyzates. Starch in grain samples was determined as alpha-linked glucose polymers according to the procedure of Poore, 1989 (personal communication). This procedure, routinely used in the authors' laboratory, has been very consistent in quantitative recovery of starch from cornstarch, corn, and sorghum standards. Total starch in the grain was determined using a .2-g sample of cleaned, ground grain weighed into a 15-mL screw-cap test tube. The sample was suspended in 2 mL CaCl2 solution (25% wt/ vol, pH 2.0) for 1 h. The samples were autoclaved at 121 C for 1 h, and then allowed to cool to at least 60 C. When the test tubes had cooled sufficiently, 8 mL of an enzyme solution8 in .1 M acetate buffer (pH 4.2), was added and the samples were incubated for 16 h at 60 C. The samples were rinsed into 100 mL volumetric flasks and brought to volume with .2% (wt/vol) benzoic acid. An aliquot was centrifuged at 3,000 x g for 10 min. Analysis for glucose was conducted using an automated procedure.9 Starch content was calculated by multiplying the glucose concentration by .9. In determining the in vitro starch digestibility, the same procedure was used except that pregelatinization (autoclaving) was omitted, samples were incubated for 2, 4, 8, 12, and 16 h, and the reaction was terminated by the addition of 1.5 mL 10% H 2 S0 4 . The feeding trial involved 360 Vantress x Arbor Acres broilers. Chicks were randomly assigned to six dietary treatments in a 2 x 3 factorial arrangement of variables using a completely randomized design. Each treatment was replicated 10 times with six birds (three males and three females) per replicate pen. The main effects were method of grain processing and grain source. The two methods of grain processing were untreated and ground or micronized and ground. Grains were ground through a hammer mill that had a full circle screen with ,48-cm round holes. Micronized grains appeared to have more uniform particle size than unmicronized grain after grinding. Grain sources were corn, LTS, and HTS.
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Commercial LTS 4 and HTS 5 were produced at the University of Nebraska Agricultural Research and Development Center, Mead, NE in 1988. The yellow corn was obtained from the University of Nebraska Agronomy farm. Tap water was added to 450 kg of each grain in a horizontal mixer to reconstitute to about 18% moisture. Grains were tempered overnight in multiwall paper bags to allow the added moisture to equilibrate. Tempered grains were micronized (infrared heated) to 150 C for 3 min in a 704 C Infraionizer.6 Infrared heating was immediately followed by a thin flaking process. Grain samples were analyzed for protein, lipid (ether extract), ash, Ca, and P by the methods of the Association of Official Analytical Chemists (1984). Acid detergent fiber (ADF; Van Soest, 1963), and neutral detergent fiber (NDF; Van Soest and Marcus, 1964) were also determined. Tannin content was determined using the vanillin HC1 method (Burns, 1971). The gross energy (GE) content of the grains was measured using an adiabatic bomb calorimeter.7 Grain samples were hydrolyzed at 110 C in a N atmosphere for 20 h in preparation for amino acid analysis. Amino acids of hydrolyzates were then separated by HPLC using ion-exchange column and lithium buffers as eluants. Amino acids were detected and measured fluorometrically using o-phthaldehyde postcolumn derivatization (Benson and
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DOUGLAS ET AL.
TABLE 1. Composition and calculated nutrient levels of diets fed from 1 to 21 days o\
Ingredients and calculated composition 1
Percentage 53.0 37.5 4.5 2 1.9 1.3 .4 1.2 100.0 3,041 22.6 .93 1.31 1.0 .5
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Corn, low-, or high-tannin sorghum in either ground or micronized then ground form. 2 Premix furnished the following per kilogram of diet vitamin A, 11,000 IU; vitamin D 3 , 4,400 IU; menadione sodium bisulfite, 3.3 mg; vitamin E, 11 IU; riboflavin, 6.6 mg; calcium pantothenate, 11.9 mg; niacin, 77 mg; dbiotin, .11 mg; folacin, .66 mg; B12, .011 mg; choline chloride, 880 mg; copper, 10 mg; iron, 100 mg; manganese, 100 mg; zinc, 100 mg; iodine, 3.0 mg; cobalt, 1.0 mg; calcium, 92 mg; and selenium, 2 mg.
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I Composition of diets are presented in Table 1. Sorghums replaced corn on an equal weight basis. Protein and metabolizable energy of the diets varied in accordance with the grain and method of processing. Birds were maintained in electrically heated, Petersime10 starting batteries with raised wire floors from 1 to 21 days. Feed and water were provided for ad libitum consumption. Starch digestibility was calculated as (solubilized starch •*• total grain starch) x 100. In vitro starch digestibility was determined by calculating multiple linear regression equations with the PROC REG procedure of SAS® (SAS Institute, 1985), with digestibility (Y) as the dependent variable and time (X) as the independent variable. Feeding trial data were analyzed as a 2 x 3 factorial arrangement using the General Linear Models procedure (SAS Institute, 1985). Treatment means were sepa-
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Grain Soybean meal (47.5% CP) Animal fat DL-methionine (99%) Dicalcium phosphate Ground limestone Sodium chloride Premix2 Total Calculated composition ME, kcal/kg CP Methionine and cystine Lysine Calcium Available phosphorus
-H-H-H-H-H-H-H-H-H-H
MICRONIZATION OF CEREAL GRAINS
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TABLE 3. Effect of micronization on amino acid profile of corn, low-, and high-tannin sorghum1
CP, %
Untreated
10.0 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.35 .15 .05 .06 .04 .03 .01 .09 .06 .09 .19 .02 .04 .04 .03 .38
5.9 2.6 4.2 2.7 35 12.5 2.1 2.0 3.4 4.6 2.7 3.3 4.2 5.9 18.0 6.1
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.05 .09 .01 .07 .01 .05 .02 .05 .13 .05 .05 .03 .09 .10 .25 .01
Micronized
Untreated
Untreated
9.9
9.6
9.8
4.8 2.8 4.1 2.0 32 10.5 2.3 2.0 2.2 4.2 2.3 3.2 4.0 6.1 16.5 7.0
on a DM b 3.1 ± .07 3.1 ± .02 3.6 ± .04 2.2 ± .01 3.7 ± .04 11.6 ± .13 2.3 ± .06 2.2 ± .07 2.9 ± .06 4.6 ± .22 2.5 ± .11 2.9 ± .07 4.5 ± .03 6.0 ± .06 17.4 ± .35 8.4 ± .06
4.4 2.8 4.2 2.1 3.4 10.7 2.1 1.9 1.9 42 2.3 3.2 42 6.0 17.1 7.3
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
CP .04 .06 .11 .02 .03 .28 .02 .18 .07 .10 .02 .10 .08 .17 .62 .30
Micronized 9.7
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.20 .03 .02 .04 .06 .15 .02 .07 .08 .08 .07 .01 .16 .04 .30 .12
3.0 2.9 3.5 2.1 3.8 11.5 2.1 2.5 2.8 4.6 2.3 2.9 4.5 5.9 17.5 8.0
± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
.07 .11 .09 .05 .04 .12 .08 .29 .01 .04 .14 .14 .04 .08 .01 .52
Values are the x ± SD of two determinations per sample
rated using single degree of freedom preplanned nonorthogonal contrasts (Steel and Torrie, 1980). RESULTS AND DISCUSSION
The results of the chemical composition analyses are presented in Table 2. Micronization decreased the ADF and NDF content regardless of the grain source. Micronization slightly decreased the lipid content and GE value of com. Tannin contents (expressed as
percentage catechin equivalents on a dry matter basis) of untreated LTS, micronized LTS, untreated HTS, and micronized HTS, were .06, .05, 5.6, and 4.1%, respectively. Amino acid profiles of untreated and micronized com, LTS, and HTS, expressed as percentage of protein on a DM basis, are presented in Table 3. Proline was not reported because it does not react with o-phthaldehyde unless it is oxidized first. Com, LTS, and HTS had minor differences in their protein and amino acid composition. Micronization caused
TABLE 4. In vitro starch digestibility with glucoamylase1,2 Corn
Low-tannin sorghum
Hours
Untreated3
Micronized4
2 4 8 12 16
50.3 59.2 67.2 77.8 80.5
88.6 94.4 95.2 98.1 97.1
± .99 ± 4.01 ± 1.13 ± .01 ± 1.46
± ± ± ± ±
.83 .34 .20 .11 .64
High-tannin sorghum
Untreated5
Micronized6
Untreated7
Micronized8
44.7 60.0 64.1 78.3 81.7
70.4 82.1 82.9 93.2 93.2
50.3 62.7 68.1 78.5 80.4
76.4 85.2 85.7 94.1 93.5
± .02 ± 1.54 ± 2.33 ± 1.77 ± .62
± 22 ± 1.26 ± .88 ± 1.04 ± .32
± 1.88 ± 1.55 ± .67 ± .74 ± 1.29
± .66 ± 155 ± 1.69 ± .30 ± .86
'Values are the x ± SD of two determinations per sample. Percentage starch was calculated as (solubilized starch + total grain starch) x 100. 3 Regression equation Y = 43.15 + 4.09XJ - .073X2 (r2 = .96), where Y is starch digestibility and X is time in minutes. ''Regression equation Y = 86.73 + 1.82X! - .074X2 (r2 = .77), where Y is starch digestibility and X is time in minutes. ^Regression equation Y = 38.74 + 4.63Xj - .12X2 (r2 = .94), where Y is starch digestibility and X is time in minutes. degression equation Y = 6650 + 3.33Xj - .10X2 (r2 = .89), where Y is starch digestibility and X is time in minutes. 'Regression equation Y = 43.85 + 4.38Xj - .13X2 (r2 = .95), where Y is starch digestibility and X is time in minutes. degression equation Y = 72.97 + 2.60XX - .08X2 (r 2 = .88), where Y is starch digestibility and X is time in minutes.
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6.4 3.1 4.2 2.8 3.3 11.0 2.8 2.1 3.4 4.5 3.0 3.4 4.3 6.3 16.9 6.1
Arg Gly Ser His lie Leu Lys Met Cys Phe Tyr Thr Val Asp Glu Ala
Micronized
10.3
High-tannin. sorghum
Low-tannin sorghum
Com Amino acid
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DOUGLAS ET AL. TABLE 5. Effect of micronization and grain source on weight gain, feed conversion, and feed intake of broilers, 1 to 21 days of age Grain source
Measurement Weight gain,1 g Untreated Micronized X
Feed conversion,2 g:g Untreated Micronized X
X
High-tannin sorghum
541 584 562
556 584 570
510 552 530
1.57 1.49 1.53 848 870 855
1.54 1.51 1.52 854 882 868
1.58 1.55 1.56 805 855 830
X
CV
536 573
6.3
1.56 1.52
836 869
3.9
5.6
Grain treatment by grain source interaction (P>.80); micronized versus untreated (P-c.0006); corn versus low-tannin (LTS) sorghum (P>.55); LTS sorghum versus high-tannin (HTS) sorghum (P<003). Grain treatment by grain source interaction (P>.39); micronized versus untreated (P<005); com versus LTS sorghum (P>.80); LTS sorghum versus HTS sorghum (P<08). 3 Grain treatment by grain source interaction (P>.76); micronized versus untreated (P<.02); corn versus LTS sorghum (P>.46); LTS sorghum versus HTS sorghum (P<03).
minor alterations in the amino acid profiles of the grains. The Arg in corn, LTS, and HTS and Lys in corn were decreased by this treatment. In contrast, the Cys level in micronized LTS and HTS was higher than in untreated LTS and HTS. The result of Diazyme L-200 (glucoamylase) hydrolysis is a quantitative conversion of starch polymers to glucose. Starch that has been gelatinized or disrupted is more rapidly degraded by the enzyme than untreated starch (McNeill et al, 1975). Results of in vitro digestibility with glucoamylase are presented in Table 4. Micronization improved in vitro starch digestibility regardless of grain source. Starch of micronized corn was more susceptible to glucoamylase during the first 8 h of incubation than starch of micronized LTS and HTS. In vitro starch digestibility of untreated corn, LTS, and HTS was not different. This was not expected because sorghum tannins reportedly cause inhibition of a-amylase in vitro (Miller and Kneen, 1947; Strumeyer and Malin, 1969; Maxon et al, 1973; Daiber, 1975; Reichert et al, 1980; Mitaru and Blair, 1984). However, Daiber (1975) suggested that the enzymatic inhibition by tannins might be dependent on their quantity as well as quality and nature. Furthermore, they reported that the tannins assayed by the vanillin HCl procedure
(used in the present study) are of the anthocyanogens type and are not enzyme inhibiting. Weight gain, FC, and feed intake data are presented in Table 5. Because there were no interactions among grain sources and method of grain processing for WG (P>.80), FC (P>.39), and feed intake (P>.76) only the main effects will be considered. Birds fed corn and LTS showed no differences in WG (P>.55) and FC (P>.80). There were reductions in WG (P<003) and FC (P<08) of birds fed HTS compared with those fed LTS. The poor performance of broilers fed HTS is in agreement with the reports of Armstrong et al. (1973), Featherston and Rogler (1975), Nelson et al. (1975), Elkin et al. (1978a,b), Rogler and Sell (1984), and Rogler et al. (1985). Regardless of the grain source, micronization improved WG (P<0006), FC (P<005), and feed intake (P<.02). The improvement in WG and FC could be related to the increase in feed intake and to the rapid availability of starch during the early hours of digestion. Also, in vitro starch digestibility of untreated grain after 16 h was still lower than micronized grain (Table 4). Savage and Clark (1988) reported that micronization of HTS significantly improved apparent digestible energy but remained lower than LTS. Micronization did
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Feed intake, g Untreated Micronized
Corn
Low-tannin sorghum
MICRONIZATION OF CEREAL GRAINS
REFERENCES Armstrong, W. D., W. R. Featherston, and J. C. Rogler, 1973. Influence of methionine and other dietary additions on the performance of chicks fed bird resistant sorghum grain diet. Poultry Sci. 52: 1592-1599. Association of Official Analytical Chemists, 1984. Pages 153-336 in: Methods of Analysis. 14th ed. Association of Official Analytical Chemists, Washington, DC. Benson, J. R., and P. E. Hare, 1975. 0-Phthaldehyde fluorogenic detection of primary amines in the picomole range: comparison with fluorescamine and ninhydrin. Proc. Natl. Acad. Sci. 72:619-622. Burns, R. E., 1971. Method for estimation of tannin in sorghum grain. Agron. J. 63:511-512. Daiber, K. H., 1975. Enzyme inhibition by polyphenols of sorghum grain and malt J. Sci. Food Agric. 26: 1399-1411. Dreher, M L., C. J. Dreher, and J. W. Berry, 1984. Starch digestibility of foods: A nutritional perspective. CRC Crit. Rev. Food Sci. Nutr. 20:47-71. Elkin, R. G., W. R. Featherston, and J. C. Rogler, 1978a. Investigations of leg abnormalities in chicks consuming high tannin sorghum grain diets. Poultry Sci. 57: 757-762. Elkin, R. G., J. C. Rogler, and W. R. Featherston, 1978b. Influence of sorghum grain tannins on methionine utilization in chicks. Poultry Sci. 57:704-710. Featherston, W. R., and J. C. Rogler, 1975. Influence of tannins on the utilization of sorghum grain by rats and chicks. Nutr. Rep. Int 11:491-497. Harbers, L. H., 1975. Starch granule structural changes and amylolytic patterns in processed sorghum grain. J. Anim. Sci. 41:1496-1501. Maxon, E. D., L. W. Rooney, R. W. Lewis, L. E. Clark, and J. W. Johnson, 1973. The relationship between tannin content, enzyme inhibition, the rat performance and characteristics of sorghum grain. Nutr. Rep.
Int 8:145-152. McNeill, J. W., G. D. Potter, J. K. Riggs, and L. W. Rooney, 1975. Chemical and physical properties of processed sorghum grain carbohydrates. J. Anim. Sci. 40:335-341. Miller, B. S., and E. Kneen, 1947. The amylase inhibitor of leoti sorghum. Arch. Biochem. Biophys. 15: 251-264. Mitaru, B. N., and R. Blair, 1984. Comparative effects of cooking and high moisture storage of sorghums on protein digestibility in rats. Nutr. Rep. Int. 30: 397-^105. Moore, S., 1963. On the determination of Cystine as cystic acid. J. Biol. Chem. 238:235-237. Nelson, T. S., E. L. Stephenson, A. Burgos, J. Floyd, and J. O. York, 1975. Effect of tannin content and dry matter digestion on energy utilization and average amino acid availability of hybrid sorghum grains. Poultry Sci. 54:1620-1623. Reichert, R. D., S. E. Fleming, and D. J. Schwab, 1980. Tannin deactivation and nutritional improvement of sorghum by anaerobic storage of H2O-, HC1-, or NaOH-treated grains. X. Agric. Food Chem. 28: 824-829. Rogler, J. C , HJIJR. Ganduglia, and R. G. Elkin, 1985. Effects of nitrogen source and level on the performance of chicks and rats fed low and high tannin sorghum. Nutr. Res. 5:1143-1151. Rogler, J. C , and D. R. Sell, 1984. Effects of stage of maturity on the tannin content and nutritional quality of low and high tannin sorghum. Nutr. Rep. Int. 29: 1281-1287. Rooney, L. W., and R. L. Pflugfelder, 1986. Factors affecting starch digestibility with special emphasis on sorghum and com. J. Anim. Sci. 63:1607-1623. SAS Institute, 1985. SAS® User's Guide: Statistics. SAS Institute, Inc., Cary, NC. Savage, G. P., and A. Clark, 1988. The effect of micronization on the nutritional value of yellow and brown sorghum. Nutr. Rep. Int 37:829-837. Savage, G. P., W. C. Smith, and P. A. Briggs, 1980. A note on the influence of micronization and polyethylene glycol on the nutritional value of brown sorghum for growing pigs. Anim. Prod. 30:157-160. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics: A Biometrical Approach. 2nd. ed. McGraw Hill Book Co., New York, NY. Strumeyer, D. H., and M. J. Malin, 1969. Identification of the amylase inhibitor from seeds of leoti sorghum. Biochim. Biophys. Acta 184:643-645. Sullins, R. D., and L. W. Rooney, 1975. Light and scanning electron microscopic studies of waxy and nonwaxy endosperm sorghum varieties. Cereal Chem. 52:361-366. Thome, M. J., L. TJ. Thompson, and D J A . Jenkins, 1983. Factors affecting starch digestibility and the glycemic response with special reference to legumes. Am. J. Clin. Nutr. 34:481-488. Van Soest, P. J., 1963. Use of detergents in the analysis of fibrous feeds. II. A rapid method for the determination of fiber and lignin. J. Assoc. Off. Agric. Chem. 46:829-835. Van Soest P- J-, and W. C. Marcus, 1964. Methods for the determination of cell wall constituents in forages using detergents and the relationship between this fraction and voluntary intake and digestibility. J. Dairy Sci. 47:704.
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not decrease the assayable tannin (Table 2), which may be why feeding micronized HTS resulted in poorer WG and FC (Table 5) in the present research as well as in the results reported by Savage and Clark (1988). The present results indicate that LTS is equal to corn in nutritive value when fed to broilers. Micronization does not seem to alter the chemical composition and amino acid profile of the grain. Regardless of the grain source, micronization did increase the in vitro starch digestibility. Micronization did not decrease the assayable tannins. Improvement in grains due to micronization are consistent based on results of the current study and previous research. These improvements may or may not be economically justifiable in the future. Various cost factors involved and the manner in which grains and grain products are used will determine future trends in processing.
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