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Detoxification of High Tannin Sorghum Grains
METABOLISM AND NUTRITION Detoxification of High Tannin Sorghum Grains R. G. TEETER, S. SARANI, M. O. SMITH, and C. A. HIBBERD Department of Animal Science, Oklahoma State University Stillwater, Oklahoma 74078 (Received for publication March 1, 1984)
1986 Poultry Science 6 5 : 6 7 - 7 1 INTRODUCTION
at 25 C for 2 days has been observed to reduce chemically detectable tannin and elevate rat weight gain and feed efficiency ratios to that observed for low tannin sorghum varieties (Reichert et al, 1980). Such a process, because of its low cost, may have application by reducing sorghum grain tannin content and enhancing feeding value of bird-resistant sorghums. Our study described was to evaluate the duration of water-imbibed sorghum grain incubation time upon chemically detectable tannin content, impact of water addition and incubation upon threonine availability, and overall feeding value of bird-resistant sorghum grain in broiler rations.
Studies have demonstrated that weight gain and feed utilization are reduced when hightannin sorghum grains are fed to broiler chicks (Chang and Fuller, 1964; Connor et al, 1969; Armstrong et al., 1973a) and layers (Sell et al., 1983). The toxic effects of tannin have been ascribed, in part, to reduced nitrogen digestibility and, hence reduced nitrogen retention (Vohra et al, 1966). Rostagno (1973) observed mean amino acid digestibilities of 73, 41, and 22% for low, intermediate, and high tannin sorghums, respectively. Several techniques have been utilized to reduce tannin's toxic effects. Mechanical abrasion reduces grain tannin content but also decreases yield (Chibber et al, 1978). Supplementing high tannin sorghum diets with methyl group donors such as methionine and choline partially alleviates the effects of tannic acid (Chang and Fuller, 1964; Fuller et al, 1967; Rayudu et al, 1970; Armstrong, 1973b), in that methyl donors presumably aid in detoxifying absorbed tannins (Chang and Fuller, 1964; Fuller et al, 1966, 1967; Conner et al, 1969). Chemically treating sorghum grains with alkali destroys tannins (Price et al, 1979). Addition of water to reduce sorghum grain dry matter to 70% followed by incubation
MATERIALS AND METHODS In each of the following experiments, sorghum grain was treated by: 1) determining grain dry matter content; 2) adding water to bring grain dry matter to 70%; 3) mixing in a rotary mixer until water was absorbed; 4) storing treated sorghum grain in airtight polyethylene bags at 32 C; 5) drying at 55 C to restore grain to air-dry water content, and 6) grinding grain through a 20-mesh screen. The experiments utilized Arbor Acre X Vantress 67
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 18, 2015
ABSTRACT One in vitro and two in vivo experiments were conducted to determine appropriate methodology for and effects of detoxifying Darset, Redlan, and one commercial hybrid brown sorghum grain variety in threonine-deficient and nutritionally complete poultry rations. The detoxification procedure, which involves adding water to sorghum grain to bring dry matter to 70% and subsequent anaerobic incubation at 32 C, removes up to 100% of the chemically detectable tannin. Rate of tannin elimination was dependent upon sorghum grain variety with commercial brown sorghum requiring approximately 3 days longer than the Darset for tannin elimination. Detoxification of high tannin sorghum grains improved (P<.05) growth rate and feed efficiency dramatically in threonine-deficient, crystalline amino acid-fortified rations; the same process applied to low tannin sorghum grains was without benefit. The desirable effects of this type of grain processing appear to be due to the reduced grain tannin content. Including detoxified sorghum grains in a practical-type broiler ration failed to elicit a weight gain response although feed efficiency was improved by 13% over untreated sorghum and 3% over corn grain. Lack of a gain response was likely due to the excess protein included in the basal diet. This type of grain processing offers an alternative method of reducing sorghum grain tannin content and is likely of greatest value in rations containing marginal indispensable amino acid and protein levels. (Key words: tannin, sorghum grain, threonine)
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Experiment 3. Effects of water addition to Darset grain, followed by a 3-day incubation were studied with a practical ration during a 28-day feeding trial utilizing 96 chicks. Birds were randomly assigned to four replicates of three treatment groups. A corn-soy basal ration (Table 3) formed the first treatment with Darset and water-treated Darset grain incubated
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Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 18, 2015
broiler chicks and were conducted in a thermostatically controlled environment under continuous tungsten filament lighting. Birds were housed in electrically heated batteries with feed and water provided ad libitum. Body weight gain, feed consumption, and feed efficiency were measured at the end of the feeding period. Sorghum grain tannin content was estimated as catechin equivalents per gram grain (Price et al., 1979). Catechin is useful as a standard reference to quantitate tannin, as it is the basic subunit of polymeric procyanidin, i.e., tannin. All data were subjected to analysis of variance using the general linear model of the Statistical Analysis System (Barr et al., 1976). Experiment 1. The effect of incubation time upon tannin content of treated grain was evaluated in three separate in vitro assays. In Assay 1, water-treated Darset grain (2.5 3 catechin eq/g) was incubated for 1, 2, 4, and 8 days after water imbibing; in Assay 2, Darset, Redlan, and a commercial brown sorghum grain variety were also water treated and incubated for 3 days; and in Assay 3, the three watertreated grain types were incubated for 3, 6, and 12 days. Experiment 2. Two high tannin (Darset, Commercial brown sorghum) and one low tannin (Redlan) sorghum grain varieties were used in nine treatments (Table 1) to judge the effect of water addition and subsequent 12-day incubation upon threonine bioavailability. The experimental period, Day 8 to 16 posthatching, utilized three replicates of 8 chicks per replicate for each treatment. Rations (Table 1) were supplemented with crystalline amino acids (Table 2) such that each was first limiting in threonine. Amino acids were added quantum sufficient to bring all essential amino acids to 60% of the chicks requirement (National Research Council, 1977) for maximal growth except for threonine, which was approximately 45% of the herd. Supplemental threonine was added to Treatments 3, 6, and 9 to validate threonine as the first limiting nutrient. Choline chloride was provided in each ration to meet the full choline requirement.
(Ex
68
a S
DETOXIFICATION OF HIGH TANNIN SORGHUM TABLE 2. Crystalline amino acid mixtures added to sorghum varieties, (Experiment 2)
::
2.5
\
2.0
Amino acids
Darset
Brown
Redlan
\ \
1.5
— (%) L-Glutamine L-Lysine HC1 L-Arginine HC1 DL-Methionine L-Cysteine L-Tryptophan Glycine L-Serine
2.80 .47 .42 .16 .09 .02
3.80 .49 .46 .17 .11 .04 .02 .01
1.80 .43 .36 .15 .06 .01
Incubating water-imbibed Darset sorghum grain reduced (P<.05) detectable tannin con-
TABLE 3. Formulas and analysis of the diets (Experiment 3) Sorghum grain
- (% Corn, ground (8.9%) Darset (11.7%) Soybean meal (44%) Meat plus bone meal (55%) Alfalfa meal (17%) Dicalcium phosphate Calcium carbonate Vitamin premix 2 Sodium chloride DL-Methionine Trace minerals3 Chromic oxide Protein ME, kcal/kg 1
. 5
U-
- - - - - - _ - - - -•
0 Incubation Time (Days)
53.15 35.95 5.00 3.00 1.00 .90 .40 .30 .10 .10 .10
53.15 35.95 5.00 3.00 1.00 .90 .40 .30 .10 .10 .10
24.00 2,764.00
25.00 2,732.00
Percentage refers to crude protein content.
2 Mix contained vitamin A, 3,527,360 IU; vitamin D 3 , 1,322,760 IU; vitamin E, 11,905 IU; vitamin B 1 2 , 3.5 mg; riboflavin, 2,205 mg; niacin, 6,614 mg; d-panthothenic acid, 7,055 mg; choline, 176,368 mg; menadione, 291 mg; folic acid, 441 mg; pyridoxine, 882 mg; thiamine, 882 mg; d-biotin, 44 mg/kg. 3 Mix contained manganese, 12.0%; zinc, 8.0%; iron, 6.0%; copper, 1.0%; iodine, . 1 % ; calcium, 18.0%.
tent markedly (3%/hr) during the first day of incubation after which the decline slowed to .3%/hr (Fig. 1). Based upon this assay, incubation of 3 days appeared sufficient to reduce sorghum grain tannin content. However, in the second assay, incubating a second hightannin commercial brown sorghum variety reduced tannin content only 7% after 3 days incubation; this in sharp contrast to the dramatic tannin reduction in the Darset (Table 4). This suggests that sorghum grain variety can have a profound impact upon either the benefits derived from water addition or the incubation period required to ensure tannin elimination. To evaluate further water treatment and incubation effects upon sorghum grain, a third assay was conducted varying incubation to 12 days. Once again, differences in the rate of tannin elimination by grain varieties were detected, although by 12 days all chemically detectable tannin was eliminated (Table 5). In the second experiment, rations were formulated to make threonine the first-limiting
TABLE 4. Darset, Redlan, and commercial brown sorghum grain tannin concentration in Assay 2 of Experiment 1
Sample
Incubation time (days)
Darset Treated Darset Brown sorghum Treated brown sorghum Redlan Treated Redlan
0 3 0 3 0 3
Tannin (catechin eq/g) 2.53 .69 2.41 2.25 0 0
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 18, 2015
RESULTS AND DISCUSSION
Corn
1.0
FIG. 1. Relationship between Darset sorghum grain tannin concentration and incubation time in Assay 1 of Experiment 1.
for 3 days substituted for corn (w/w) in Treatments 2 and 3, respectively.
Ingredients 1
Tannin (% Catechin eq./g)
69
70
TEETER ET AL.
TABLE 5. Darset, Redlan, and commercial brown sorghum grain tannin concentration in Assay 3 of Experiment 1 Tannin, incubation time 0 days
Darset Treated Darset Brown Treated brown Redlan Treated Redlan
2.5 3 2.53 2.41 2.41 0 0
3 days
6 days
12 days
(catechin equivalent/g)69
50
25
14
nutrient in an 8-day feeding study. Previous work in our laboratory utilizing lysine as the first-limiting nutrient failed to detect beneficial effects of this type of treatment upon lysine availability, presumably because sorghum grain lysine is quite low, thereby creating an insensitive nutrient for growth assays. Lysine binding by tannin during the water treatment and incubation process, however, cannot be refuted. The sorghum grains utilized in this study contained sufficient threonine to meet 45% of this amino acid's requirement and was therefore utilized to ensure adequate sorghum concentration of the limiting nutrient. A preliminary experiment validated that the crystalline amino acid mixture used (Table 3) indeed made threonine the first-limiting nutrient.
Including untreated and treated sorghum grain in a commercial-type broiler ration (Table 7) failed to enhance growth rate significantly in Experiment 3. The feed efficiency of detoxified grain, enhanced by 13% (P<.01) over untreated sorghum grain and by 3% over corn grain was not significantly different. Protein content of these rations exceeded the broiler protein requirement and conceivably could have allowed a normal growth rate. Including excess dietary protein to eliminate the deleterious effects of tannin upon broiler growth would not be expected to eliminate the negative impact of sorghum tannin upon feed efficiency as the protein-tannin complex thus formed would be indigestible.
TABLE 6. Assayed tannin and threonine and body weight gain and feed efficiency for Experiment 2
Treatments
Darset Treated Darset 2 Darset plus t h r e o n i n e Brown Treated brown2 Brown plus t h r e o n i n e Redlan Treated Redlan2 Redlan plus t h r e o n i n e
Tannin
Threonine1
Weight gain/chick
(catechin eq/g)
(%)
(g)
2.5 3 0 2.53 2.41 0 2.41 0 0 0
.34 .34 .47 .32 .32 .49 .33 .30 .43
218f 415d 584c 265f 347e 641b 413d 436d 85 l a
a—f Statistically significant at (P<.05) or (P<.01). 'Threonine determination made utilizing a Beckman amino acid analyzer. 2
Incubation for 12 days at 32 C.
Feed/ gam
4.4a 2.7cd 2.5d 4.1b 3.0C 2.4d 3.0C 27cd 2.ie
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 18, 2015
Treatments
Addition of water to Darset and Brown sorghum grain followed by a 12-day incubation eliminated 100% of the chemically detectable tannin and increased (P<.01) body weight gain and feed efficiency (Table 6) for chicks fed rations in which threonine was the first-limiting nutrient. Supplementing untreated sorghum grains with threonine to bring ration threonine content to 60% of the National Research Council requirement similarly elevated body weight gain (P<.01) and feed efficiency (P<.05), which confirmed that threonine was indeed the first-limiting nutrient. The detoxification process increased sorghum bioavailable but not assayable threonine as affirmed by amino acid analysis. Chicks receiving the processed low tannin sorghum did not have significantly heavier body weights or better feed efficiency than those receiving the untreated sorghum.
DETOXIFICATION OF HIGH TANNIN SORGHUM TABLE 7. Assayed tannin, body weight gain, and feed efficiency ratios for Experiment 3
Treatments
Tannin
Corn Darset Detoxified Darset1
(catechin eq/g) 0 2.53 .63
Weight gain
Gain/ feed
(g) 892 891 895
.61a .56 b .63 a
1
Water-treated and incubated 3 days at 32 C.
A d d i t i o n of water t o sorghum grain and subsequent anaerobic incubation provided an effective m e t h o d t o detoxify tannin in the sorghum grains evaluated; however, t o utilize fully this t e c h n i q u e in a commercial setting would likely necessitate feeding higher moisture rations t o p o u l t r y unless economical m e t h o d s are available t o dry detoxified grain.
REFERENCES Armstrong, W. D., 1973a. Nutritive evaluation of bird resistant and non-resistant sorghum grain in chicks. M. S. Thesis, Purdue Univ., West Lafayette, IN. Armstrong, W. D., W. R. Featherston, and J. C. Rogler, 1973b. Influence of methionine and other dietary additions on the performance of chicks fed bird resistant sorghum grain diets. Poultry Sci. 52:1592-1599. Barr, A. J., J. H. Goodnight, J. P. Sail, and J. T. Helwig, 1976. A User's Guide to SAS. Stall. Anals. Syst. Inst., Inc., Cary, NC. Chang, S. I., and H. L. Fuller, 1964. Effect of tannin content of grain sorghums on their feeding value for growing chicks. Poultry Sci. 43:30—36. Chibber, A. K., E. T. Mem, and J. D. Axtell, 1978.
Effect of dehulling on tannin content, protein distribution and quality of high and low tannin sorghum. J. Agric. Food Chem. 26:679-683. Connor, J. K., I. S. Hurwood, H. W. Burton, and D. E. Fuelling, 1969. Some nutritional aspects of feeding sorghum grain of high-tannin content to growing chickens. Aust. J. Agric. Anim. Husb. 9:497-501. Fuller, H. L„ D. K. Potter, and A. R. Brown, 1966. The feeding value of grain sorghums in relation to their tannin content. Georgia Agric. Exp. Stat., Univ. Georgia Bull. N. S. 176. Fuller, H. L., S. I. Chang, and D. K. Potter, 1967. Detoxification of dietary tannic acid by the chick. J. Nutr. 91:477-481. Katz, R. S., and D. H. Baker, 1975. Methionine toxicity in the chick: Nutritional and metabolic implications. J. Nutr. 105:1168. National Research Council, 1977. Nutrient Requirements of Domestic Animals. 1. Nutrient Requirements of Poultry. Natl. Acad. Sci. Washington, DC. Price, M. L., L. C. Butler, J. C. Rogler, and W. R. Featherston, 1979. Overcoming the nutritionally harmful effects of tannin in sorghum grain by treatment with inexpensive chemicals. J. Agric. Food Chem. 27:441-445. Rayudu, G. V., N. R. Kadirvel, P. Vohra, and F. H. Kratzer, 1970. Toxicity of tannic acid and its metabolities for chickens. Poultry Sci. 49: 957-960. Reichert, R. D., S. E. Fleming, and D. J. Schwab, 1980. Tannin deactivation and nutritional improvement of sorghum by anaerobic storage of H 2 0 , HC1, or NaOH treated grain. J. Agric. Food Chem. 28:824-829. Rostagno, H. S., J. C. Rogler, and W. R. Featherston, 1973. Studies on the nutritional value of sorghum grain with varying tannin content for chicks. I. Amino acid digestibility studies. Poultry Sci. 52:772-778. Sell, D. R., J . C . Rogler, andW. R. Featherston, 1983. The effects of sorghum tannin and protein level on the performance of laying hens maintained in two temperature environments. Poultry Sci. 62:2420-2428. Vohra, P., F. H. Kratzer, and M. A. Joslyn, 1966. The growth depressing and toxic effects of tannins to chicks. Poultry Sci. 45:135-142.
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' Values within a column with different letters differ (P<.01).
71
1986 Poultry Science 6 5 : 6 7 - 7 1 INTRODUCTION
at 25 C for 2 days has been observed to reduce chemically detectable tannin and elevate rat weight gain and feed efficiency ratios to that observed for low tannin sorghum varieties (Reichert et al, 1980). Such a process, because of its low cost, may have application by reducing sorghum grain tannin content and enhancing feeding value of bird-resistant sorghums. Our study described was to evaluate the duration of water-imbibed sorghum grain incubation time upon chemically detectable tannin content, impact of water addition and incubation upon threonine availability, and overall feeding value of bird-resistant sorghum grain in broiler rations.
Studies have demonstrated that weight gain and feed utilization are reduced when hightannin sorghum grains are fed to broiler chicks (Chang and Fuller, 1964; Connor et al, 1969; Armstrong et al., 1973a) and layers (Sell et al., 1983). The toxic effects of tannin have been ascribed, in part, to reduced nitrogen digestibility and, hence reduced nitrogen retention (Vohra et al, 1966). Rostagno (1973) observed mean amino acid digestibilities of 73, 41, and 22% for low, intermediate, and high tannin sorghums, respectively. Several techniques have been utilized to reduce tannin's toxic effects. Mechanical abrasion reduces grain tannin content but also decreases yield (Chibber et al, 1978). Supplementing high tannin sorghum diets with methyl group donors such as methionine and choline partially alleviates the effects of tannic acid (Chang and Fuller, 1964; Fuller et al, 1967; Rayudu et al, 1970; Armstrong, 1973b), in that methyl donors presumably aid in detoxifying absorbed tannins (Chang and Fuller, 1964; Fuller et al, 1966, 1967; Conner et al, 1969). Chemically treating sorghum grains with alkali destroys tannins (Price et al, 1979). Addition of water to reduce sorghum grain dry matter to 70% followed by incubation
MATERIALS AND METHODS In each of the following experiments, sorghum grain was treated by: 1) determining grain dry matter content; 2) adding water to bring grain dry matter to 70%; 3) mixing in a rotary mixer until water was absorbed; 4) storing treated sorghum grain in airtight polyethylene bags at 32 C; 5) drying at 55 C to restore grain to air-dry water content, and 6) grinding grain through a 20-mesh screen. The experiments utilized Arbor Acre X Vantress 67
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 18, 2015
ABSTRACT One in vitro and two in vivo experiments were conducted to determine appropriate methodology for and effects of detoxifying Darset, Redlan, and one commercial hybrid brown sorghum grain variety in threonine-deficient and nutritionally complete poultry rations. The detoxification procedure, which involves adding water to sorghum grain to bring dry matter to 70% and subsequent anaerobic incubation at 32 C, removes up to 100% of the chemically detectable tannin. Rate of tannin elimination was dependent upon sorghum grain variety with commercial brown sorghum requiring approximately 3 days longer than the Darset for tannin elimination. Detoxification of high tannin sorghum grains improved (P<.05) growth rate and feed efficiency dramatically in threonine-deficient, crystalline amino acid-fortified rations; the same process applied to low tannin sorghum grains was without benefit. The desirable effects of this type of grain processing appear to be due to the reduced grain tannin content. Including detoxified sorghum grains in a practical-type broiler ration failed to elicit a weight gain response although feed efficiency was improved by 13% over untreated sorghum and 3% over corn grain. Lack of a gain response was likely due to the excess protein included in the basal diet. This type of grain processing offers an alternative method of reducing sorghum grain tannin content and is likely of greatest value in rations containing marginal indispensable amino acid and protein levels. (Key words: tannin, sorghum grain, threonine)
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Experiment 3. Effects of water addition to Darset grain, followed by a 3-day incubation were studied with a practical ration during a 28-day feeding trial utilizing 96 chicks. Birds were randomly assigned to four replicates of three treatment groups. A corn-soy basal ration (Table 3) formed the first treatment with Darset and water-treated Darset grain incubated
•o • oo
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 18, 2015
broiler chicks and were conducted in a thermostatically controlled environment under continuous tungsten filament lighting. Birds were housed in electrically heated batteries with feed and water provided ad libitum. Body weight gain, feed consumption, and feed efficiency were measured at the end of the feeding period. Sorghum grain tannin content was estimated as catechin equivalents per gram grain (Price et al., 1979). Catechin is useful as a standard reference to quantitate tannin, as it is the basic subunit of polymeric procyanidin, i.e., tannin. All data were subjected to analysis of variance using the general linear model of the Statistical Analysis System (Barr et al., 1976). Experiment 1. The effect of incubation time upon tannin content of treated grain was evaluated in three separate in vitro assays. In Assay 1, water-treated Darset grain (2.5 3 catechin eq/g) was incubated for 1, 2, 4, and 8 days after water imbibing; in Assay 2, Darset, Redlan, and a commercial brown sorghum grain variety were also water treated and incubated for 3 days; and in Assay 3, the three watertreated grain types were incubated for 3, 6, and 12 days. Experiment 2. Two high tannin (Darset, Commercial brown sorghum) and one low tannin (Redlan) sorghum grain varieties were used in nine treatments (Table 1) to judge the effect of water addition and subsequent 12-day incubation upon threonine bioavailability. The experimental period, Day 8 to 16 posthatching, utilized three replicates of 8 chicks per replicate for each treatment. Rations (Table 1) were supplemented with crystalline amino acids (Table 2) such that each was first limiting in threonine. Amino acids were added quantum sufficient to bring all essential amino acids to 60% of the chicks requirement (National Research Council, 1977) for maximal growth except for threonine, which was approximately 45% of the herd. Supplemental threonine was added to Treatments 3, 6, and 9 to validate threonine as the first limiting nutrient. Choline chloride was provided in each ration to meet the full choline requirement.
(Ex
68
a S
DETOXIFICATION OF HIGH TANNIN SORGHUM TABLE 2. Crystalline amino acid mixtures added to sorghum varieties, (Experiment 2)
::
2.5
\
2.0
Amino acids
Darset
Brown
Redlan
\ \
1.5
— (%) L-Glutamine L-Lysine HC1 L-Arginine HC1 DL-Methionine L-Cysteine L-Tryptophan Glycine L-Serine
2.80 .47 .42 .16 .09 .02
3.80 .49 .46 .17 .11 .04 .02 .01
1.80 .43 .36 .15 .06 .01
Incubating water-imbibed Darset sorghum grain reduced (P<.05) detectable tannin con-
TABLE 3. Formulas and analysis of the diets (Experiment 3) Sorghum grain
- (% Corn, ground (8.9%) Darset (11.7%) Soybean meal (44%) Meat plus bone meal (55%) Alfalfa meal (17%) Dicalcium phosphate Calcium carbonate Vitamin premix 2 Sodium chloride DL-Methionine Trace minerals3 Chromic oxide Protein ME, kcal/kg 1
. 5
U-
- - - - - - _ - - - -•
0 Incubation Time (Days)
53.15 35.95 5.00 3.00 1.00 .90 .40 .30 .10 .10 .10
53.15 35.95 5.00 3.00 1.00 .90 .40 .30 .10 .10 .10
24.00 2,764.00
25.00 2,732.00
Percentage refers to crude protein content.
2 Mix contained vitamin A, 3,527,360 IU; vitamin D 3 , 1,322,760 IU; vitamin E, 11,905 IU; vitamin B 1 2 , 3.5 mg; riboflavin, 2,205 mg; niacin, 6,614 mg; d-panthothenic acid, 7,055 mg; choline, 176,368 mg; menadione, 291 mg; folic acid, 441 mg; pyridoxine, 882 mg; thiamine, 882 mg; d-biotin, 44 mg/kg. 3 Mix contained manganese, 12.0%; zinc, 8.0%; iron, 6.0%; copper, 1.0%; iodine, . 1 % ; calcium, 18.0%.
tent markedly (3%/hr) during the first day of incubation after which the decline slowed to .3%/hr (Fig. 1). Based upon this assay, incubation of 3 days appeared sufficient to reduce sorghum grain tannin content. However, in the second assay, incubating a second hightannin commercial brown sorghum variety reduced tannin content only 7% after 3 days incubation; this in sharp contrast to the dramatic tannin reduction in the Darset (Table 4). This suggests that sorghum grain variety can have a profound impact upon either the benefits derived from water addition or the incubation period required to ensure tannin elimination. To evaluate further water treatment and incubation effects upon sorghum grain, a third assay was conducted varying incubation to 12 days. Once again, differences in the rate of tannin elimination by grain varieties were detected, although by 12 days all chemically detectable tannin was eliminated (Table 5). In the second experiment, rations were formulated to make threonine the first-limiting
TABLE 4. Darset, Redlan, and commercial brown sorghum grain tannin concentration in Assay 2 of Experiment 1
Sample
Incubation time (days)
Darset Treated Darset Brown sorghum Treated brown sorghum Redlan Treated Redlan
0 3 0 3 0 3
Tannin (catechin eq/g) 2.53 .69 2.41 2.25 0 0
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on June 18, 2015
RESULTS AND DISCUSSION
Corn
1.0
FIG. 1. Relationship between Darset sorghum grain tannin concentration and incubation time in Assay 1 of Experiment 1.
for 3 days substituted for corn (w/w) in Treatments 2 and 3, respectively.
Ingredients 1
Tannin (% Catechin eq./g)
69
70
TEETER ET AL.
TABLE 5. Darset, Redlan, and commercial brown sorghum grain tannin concentration in Assay 3 of Experiment 1 Tannin, incubation time 0 days
Darset Treated Darset Brown Treated brown Redlan Treated Redlan
2.5 3 2.53 2.41 2.41 0 0
3 days
6 days
12 days
(catechin equivalent/g)69
50
25
14
nutrient in an 8-day feeding study. Previous work in our laboratory utilizing lysine as the first-limiting nutrient failed to detect beneficial effects of this type of treatment upon lysine availability, presumably because sorghum grain lysine is quite low, thereby creating an insensitive nutrient for growth assays. Lysine binding by tannin during the water treatment and incubation process, however, cannot be refuted. The sorghum grains utilized in this study contained sufficient threonine to meet 45% of this amino acid's requirement and was therefore utilized to ensure adequate sorghum concentration of the limiting nutrient. A preliminary experiment validated that the crystalline amino acid mixture used (Table 3) indeed made threonine the first-limiting nutrient.
Including untreated and treated sorghum grain in a commercial-type broiler ration (Table 7) failed to enhance growth rate significantly in Experiment 3. The feed efficiency of detoxified grain, enhanced by 13% (P<.01) over untreated sorghum grain and by 3% over corn grain was not significantly different. Protein content of these rations exceeded the broiler protein requirement and conceivably could have allowed a normal growth rate. Including excess dietary protein to eliminate the deleterious effects of tannin upon broiler growth would not be expected to eliminate the negative impact of sorghum tannin upon feed efficiency as the protein-tannin complex thus formed would be indigestible.
TABLE 6. Assayed tannin and threonine and body weight gain and feed efficiency for Experiment 2
Treatments
Darset Treated Darset 2 Darset plus t h r e o n i n e Brown Treated brown2 Brown plus t h r e o n i n e Redlan Treated Redlan2 Redlan plus t h r e o n i n e
Tannin
Threonine1
Weight gain/chick
(catechin eq/g)
(%)
(g)
2.5 3 0 2.53 2.41 0 2.41 0 0 0
.34 .34 .47 .32 .32 .49 .33 .30 .43
218f 415d 584c 265f 347e 641b 413d 436d 85 l a
a—f Statistically significant at (P<.05) or (P<.01). 'Threonine determination made utilizing a Beckman amino acid analyzer. 2
Incubation for 12 days at 32 C.
Feed/ gam
4.4a 2.7cd 2.5d 4.1b 3.0C 2.4d 3.0C 27cd 2.ie
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Treatments
Addition of water to Darset and Brown sorghum grain followed by a 12-day incubation eliminated 100% of the chemically detectable tannin and increased (P<.01) body weight gain and feed efficiency (Table 6) for chicks fed rations in which threonine was the first-limiting nutrient. Supplementing untreated sorghum grains with threonine to bring ration threonine content to 60% of the National Research Council requirement similarly elevated body weight gain (P<.01) and feed efficiency (P<.05), which confirmed that threonine was indeed the first-limiting nutrient. The detoxification process increased sorghum bioavailable but not assayable threonine as affirmed by amino acid analysis. Chicks receiving the processed low tannin sorghum did not have significantly heavier body weights or better feed efficiency than those receiving the untreated sorghum.
DETOXIFICATION OF HIGH TANNIN SORGHUM TABLE 7. Assayed tannin, body weight gain, and feed efficiency ratios for Experiment 3
Treatments
Tannin
Corn Darset Detoxified Darset1
(catechin eq/g) 0 2.53 .63
Weight gain
Gain/ feed
(g) 892 891 895
.61a .56 b .63 a
1
Water-treated and incubated 3 days at 32 C.
A d d i t i o n of water t o sorghum grain and subsequent anaerobic incubation provided an effective m e t h o d t o detoxify tannin in the sorghum grains evaluated; however, t o utilize fully this t e c h n i q u e in a commercial setting would likely necessitate feeding higher moisture rations t o p o u l t r y unless economical m e t h o d s are available t o dry detoxified grain.
REFERENCES Armstrong, W. D., 1973a. Nutritive evaluation of bird resistant and non-resistant sorghum grain in chicks. M. S. Thesis, Purdue Univ., West Lafayette, IN. Armstrong, W. D., W. R. Featherston, and J. C. Rogler, 1973b. Influence of methionine and other dietary additions on the performance of chicks fed bird resistant sorghum grain diets. Poultry Sci. 52:1592-1599. Barr, A. J., J. H. Goodnight, J. P. Sail, and J. T. Helwig, 1976. A User's Guide to SAS. Stall. Anals. Syst. Inst., Inc., Cary, NC. Chang, S. I., and H. L. Fuller, 1964. Effect of tannin content of grain sorghums on their feeding value for growing chicks. Poultry Sci. 43:30—36. Chibber, A. K., E. T. Mem, and J. D. Axtell, 1978.
Effect of dehulling on tannin content, protein distribution and quality of high and low tannin sorghum. J. Agric. Food Chem. 26:679-683. Connor, J. K., I. S. Hurwood, H. W. Burton, and D. E. Fuelling, 1969. Some nutritional aspects of feeding sorghum grain of high-tannin content to growing chickens. Aust. J. Agric. Anim. Husb. 9:497-501. Fuller, H. L„ D. K. Potter, and A. R. Brown, 1966. The feeding value of grain sorghums in relation to their tannin content. Georgia Agric. Exp. Stat., Univ. Georgia Bull. N. S. 176. Fuller, H. L., S. I. Chang, and D. K. Potter, 1967. Detoxification of dietary tannic acid by the chick. J. Nutr. 91:477-481. Katz, R. S., and D. H. Baker, 1975. Methionine toxicity in the chick: Nutritional and metabolic implications. J. Nutr. 105:1168. National Research Council, 1977. Nutrient Requirements of Domestic Animals. 1. Nutrient Requirements of Poultry. Natl. Acad. Sci. Washington, DC. Price, M. L., L. C. Butler, J. C. Rogler, and W. R. Featherston, 1979. Overcoming the nutritionally harmful effects of tannin in sorghum grain by treatment with inexpensive chemicals. J. Agric. Food Chem. 27:441-445. Rayudu, G. V., N. R. Kadirvel, P. Vohra, and F. H. Kratzer, 1970. Toxicity of tannic acid and its metabolities for chickens. Poultry Sci. 49: 957-960. Reichert, R. D., S. E. Fleming, and D. J. Schwab, 1980. Tannin deactivation and nutritional improvement of sorghum by anaerobic storage of H 2 0 , HC1, or NaOH treated grain. J. Agric. Food Chem. 28:824-829. Rostagno, H. S., J. C. Rogler, and W. R. Featherston, 1973. Studies on the nutritional value of sorghum grain with varying tannin content for chicks. I. Amino acid digestibility studies. Poultry Sci. 52:772-778. Sell, D. R., J . C . Rogler, andW. R. Featherston, 1983. The effects of sorghum tannin and protein level on the performance of laying hens maintained in two temperature environments. Poultry Sci. 62:2420-2428. Vohra, P., F. H. Kratzer, and M. A. Joslyn, 1966. The growth depressing and toxic effects of tannins to chicks. Poultry Sci. 45:135-142.
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' Values within a column with different letters differ (P<.01).
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