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Investigations of Threonine Requirements of Broiler Chicks Fed Diets Based on Grain Sorghum and Soybean Meal1
Investigations of Threonine Requirements of Broiler Chicks Fed Diets Based on Grain Sorghum and Soybean Meal 1 N. K. SMITH, JR. and P. WALDROUP2 Department of Animal Sciences, University of Arkansas, Fayetteville, Arkansas 72701 (Received for publication February 23, 1987)
1988 Poultry Science 67:108-112 INTRODUCTION
For approximately 30 years, methionine supplements have been routinely used to fortify soybean meal-based diets for broiler chickens. Through the use of this amino acid to overcome one of the major nutrient shortcomings of soybean meal, the overall protein content of broiler diets can be reduced without adversely affecting the performance of the chicken (Waldroup et al., 1976). Although lysine supplements have been available for approximately the same time, they have not been used as extensively. Soybean meal is a relatively good source of lysine, and the cost of lysine supplements has not been as favorable as methionine supplements. Therefore, the use of lysine in broiler feeds has been rather sporadic and inconsistent. Another factor that has limited the use of lysine in broiler diets has been an uncertainty about the levels of other essential amino acids that are needed in the diet. When lysine and methionine supplements are used to fortify broiler diets, the total crude protein content de-
Published with the approval of the Director, Arkansas Agricultural Experiment Station. 2 To whom correspondence should be addressed.
clines, usually accompanied by a decline in the level of other essential amino acids. There has been little work done using diets of a practical nature to delineate the requirements for amino acids other than methionine and lysine. A number of excellent studies with purified diets have been conducted, but requirements developed using these diets have not been directly convertible to more practical diets because of a number of factors such as digestibility of the amino acids in different feedstuffs and amino acid balance. Among the amino acids of interest in diets containing reduced protein levels is threonine (Thr), which appears to be limiting in low protein diets, especially those based on grain sorghum. Almquist and Grau (1944) reported that 1.0% DL-Thr was not sufficient for optimum growth whereas 2.0% appeared adequate. Almquist (1947) concluded that certain proteins were capable of supporting optimal chick growth when providing no more than .6% Thr. Grau (1949) indicated that .5% DL-Thr was insufficient for satisfactory growth, and 1.0% DL-Thr was satisfactory. Also, .3% L-Thr was inadequate but .5% L-Thr was satisfactory for growth. Chicks fed .45% L-Thr grew as well as those fed .5% L-Thr. Krautman et al. (1958) concluded that the L-Thr requirement of 7 to
108
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ABSTRACT Three trials were conducted to estimate the threonine (Thr) requirement of male broiler chicks. Chicks 7 days of age were fed a grain sorghum-soybean meal diet containing .59% Thr, supplemented with 0, .05, .09, .15, .22, .27, or .28% L-Thr. Levels of basal and supplemental amino acids were confirmed by ion-exchange chromatography. Diets were fed for 18 or 20 days, depending upon the trial. A corn-soybean meal diet analyzed to contain .90% Thr was used for comparison. Results of the three trials were pooled for determination of Thr requirements. A significant improvement in gain was observed when the basal grain sorghum-soybean meal diet was supplemented with .09% supplemental Thr (total .68% Thr). No further improvements in gain were observed at higher levels of Thr supplementation. Body weight gain of chicks fed the Thr-supplemented diets did not differ significantly from that of chicks fed the corn-soybean meal control diet. For maximum feed utilization, the Thr requirement was .79%, as estimated by regression analysis. This is in agreement with the .80% requirement suggested by the National Research Council in 1984. "Feed utilization of chicks fed the corn-soybean meal diet was significantly better than that of chicks fed any of the grain sorghum-soybean meal diets regardless of the level of Thr supplementation. (Key words: threonine, nutrition requirements, amino acids, body weight, feed conversion)
THREONINE REQUIREMENTS OF BROILERS MATERIALS AND METHODS
Using linear programming, a diet was formulated to meet the nutrient needs of the young (0 to 3 wk old) broiler chick as suggested by NRC (1984). Nutrient composition values provided by the NRC were used. The computer was directed to meet the minimum nutrient needs and provide the lowest amount of Thr possible with the combination of ingredients available. All other amino acids were provided at a minimum of 110% of the suggested NRC (1984) standards for the young chick. Composition of the basal diet is shown in Table 1. The diet was calculated to contain 3.2 kcal metabolizable energy per gram of feed and 15.34% crude protein from the intact protein sources. All diets were supplemented with sodium bicarbonate (.50%) and aluminum hydroxide (.30%) as buffers and antacids. Previous work from our laboratory (Watkins, 1986) indicated that corn-soybean meal-meat and bone meal diets with 15% crude protein from intact ingredients, fortified with sufficient amounts of amino acids and buffered with sodium bicarbonate and aluminum hydroxide, can support broiler gains and feed utilization equivalent to that of diets with 23% crude protein. A corn-soybean meal positive-control diet was used during this series of studies (Table 1). This control diet contained 23% crude protein and met all nutrient requirements of the young chick. After mixing, all diets were pelleted using a laboratory-model California Pellet Mill (California Pellet Mill Co., Crawfordsville, IN). The basal diet was calculated to contain .56% Thr (Table 2). Aliquots of the basal diet were fortified with .06, .12, .18, .24, .30, and .36% L-Thr to provide calculated Thr levels of .62, .68, .72, .78, .84, and .92%, respectively. Aliquots of the mixed feeds were analyzed for amino acid content. Each of the eight diets (seven test and one corn-soybean meal control) was fed to six replicate pens of five male chicks. Three consecutive feeding trials were conducted in this study. Male chicks of a commercial broiler strain (Vantress x Arbor Acres) were obtained from a local hatchery and randomly assigned to pens in electrically heated Petersime battery brooders. For the first 7 days they were fed the cornsoybean meal control diet with 23% crude protein calculated to meet or exceed all of the nutrient requirements suggested by the NRC
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF ARIZONA on April 19, 2015
21-day old chicks was between .55 and .60%. Klain et al. (1960) calculated the Thr requirement to be .58% in 7 to 12 or 14-day old chicks. Bhargava et al. (1971) found no significant differences in body weight or feed utilization at levels greater than .7% dietary Thr. Hewitt and Lewis (1972) determined that the Thr requirement for male broiler chicks 7 to 21 days of age was not more than .53%. Woodham and Deans (1975) found the Thr requirement for 14 to 28day-old broiler chicks to be .50 to .52% of the diet in the presence of .91 to 1.41% glycine. Thomas et al. (1979) reported that .82% Thr was required in one experiment with .81% needed in the second, based upon feed conversion data. Highest weight gains were obtained at .86% Thr in the first study and .85% in the second study. Thomas and Bossard (1982) found that .87% Thr was adequate for gain and feed conversion for male chicks to 3 wk of age, whereas .82% was adequate for females. Davis and Austic (1982) reported that the addition of Thr increased growth and feed efficiency in 8 to 21-day old chicks, with these effects being significantly greater at .72% Thr than at the .68% level. Thomas et al. (1986) calculated the Thr requirement is .7% for 7 to 21-day old chicks, using regression analysis. Uzu (1986) conducted two trials to determine the Thr requirement of broilers from 1 to 21 days of age. The Thr level was .70% in the basal diet and .79% in the control diet in the first experiment. In the second trial, the Thr level was .68% in the basal diet and .76% in the control diet. When L-Thr was added to the basal diets, performance was equal to that of birds fed the control diet when Thr was present at .75% in the first experiment or .73% in the second experiment. Additional Thr supplementation produced no further improvements in gain or feed conversion. The current National Research Council (NRC, 1984) requirements are .80% from 0 to 3 wk, .74% from 3 to 6 wk and .68% from 6 to 8 wk. With the development of two domestic lysine manufacturing plants in the United States, there is great interest in defining the potential needs for amino acids other than methionine and lysine in the diet of broiler chickens. To estimate what the potential for supplemental Thr might be, studies were conducted to evaluate the needs for this amino acid in diets similar in content to those used in the broiler industry.
109
110
SMITH, JR AND WALDROUP TABLE 1. Composition of diets
Ingredient
Control
Test -
Total
ygi Kg,/
.00 40.00 26.00 726.65 104.00 40.00 9.00 11.00 5.00
563.80
.60
4.00 5.00 1.00
5.00 1.00 3.00 2.66 2.88 9.26 7.78 1.75
.00
50.00 .00
319.50 44.10 5.20 5.10 .00
.00
2.30
1.50
.00 .00 .00 .00 .00 .00 .00 .00 .00
1,000.00
1,000.00
.92 .72 .62 .66
1 Provides per kilogram of diet: 6,612 IU vitamin A; 2,204 ICU vitamin D 3 ; 6.6 1U vitamin E; 3.3 mg menadione; 5.5 mg riboflavin; 66 mg niacin; 8.8 mg pantothenic acid; 495 mg choline; 1.1 mg thiamin; 1.1 mg pyridoxine; .01 mg vitamin B 12 ; .11 mg biotin; .66 mg folacin; 125 mg ethoxyquin; .11 mg selenium. 2
Provides per kilogram of diet: 100 mg Fe; 100 mg Mn; 100 mg Zn; 10 mg Cu; 1 mg I.
(1984). At 7 days of age the chickens were individually weighed and divided into different weight subclasses. These subclasses were randomly divided among the replicate pens. After division, birds were wingbanded and individually weighed. From 7 to 20 days of age in the first trial and from 7 to 18 days of age in the second and third trials birds were fed the experimental diets in pellet form ad libitum. At the conclusion of the study, birds were again individually weighed and the weight gain was calculated. The total pen feed consumption was determined. Any bird that died during the study was weighed, and its weight was used to correct feed consumption. The data were analyzed using initial bird weight as a covariate. Effects of Thr level upon performance were examined by regression procedures in the Statistical Analysis System (SAS Institute Inc., 1982). Both linear and quadratic models were examined. In the absence of significant (P>.05) linear or quadratic response,
means were separated using repeated t tests with values generated by the LSMEANS option of the General Linear Models procedure of SAS. There were no treatment x trial interactions, so data from the three trials were combined for presentation. RESULTS AND DISCUSSION
Analyses of the diets for Thr content were in agreement with calculated values (Table 2). By actual analysis, the basal diet contained .59% Thr with added levels of Thr being .05%, .09%, .15%, .22%, .27%, and .28%. The analyzed Thr level of the corn-soybean meal control diet was .90%. The crude protein content (N x 6.25%) of the basal test diet with all supplemental amino acids other than the Thr was 20.0%. Body weight gains, corrected for initial weight at 7 days, are shown in Table 2. There was no significant (P>.05) linear or quadratic response to Thr levels for body weight gain. Higher Thr values-.68% vs. .59%-resulted in
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF ARIZONA on April 19, 2015
Yellow corn Corn gluten meal (60% protein) Meat and bone meal (50% protein) Grain sorghum Soybean meal (48.5% protein) Blended animal-vegetable fat Ground limestone Dicalcium phosphate Sodium bicarbonate Sodium chloride Vitamin premix 1 Trace mineral mix 2 Aluminum hydroxide DL-Methionine (98%) Cystine Lysine HC1 (98%) Arginine HC1 Isoleucine Tryptophan Phenylalanine Tyrosine Valine Glycine
THREONINE REQUIREMENTS OF BROILERS
111
TABLE 2. Influence of dietary threonine levels on performance of male broiler chickens* Dietary threonine Calculated2
Analyzed 3
Body weight gain"
Feed efficiency5
(g) 328 b 349ab 364 a 349 a b 360 a 342 a b 356 a b 365 a 12
(gain/feed)
.59 .64 .68 .74 .81 .86 .87
('»)
.613.c .654;be .660,bc .670 b .674 b .648 r c .667'be
.709 .008
a—d Means in columns with no common superscripts differ significantly (P<.05). Means of three experiments, each with six replicate groups of five male chicks of a commercial broiler strain. 1
2
Calculated from values of National Research Council (1984).
3
Determined by ion-exchange chromatography.
"Gain from 7 to 20 days (Trial 1) or 7 to 18 days (Trials 2 and 3). 5
Threonine requirement for feed utilization estimated to be .79% by regression analysis. Formulated to meet minimum nutrient standards established by the National Research Council (1984). Analyzed to contain .90% threonine. 6
7
SEM = Standard error of the mean.
significantly higher body weight gains; there were no further gains from higher levels of Thr. Gains of chicks fed .68% Thr did not differ from those of chicks fed the corn-soybean meal control diet with 23% protein. Feed utilization, expressed as gain per gram of feed consumed, was not as good on the unsupplemented grain sorghum-soybean meal test diet as on the corn-soybean meal control diet with 23% crude protein (Table 2). Addition of Thr to the basal grain sorghum-soybean meal diet resulted in significantly better feed utilization. By regression analysis, the Thr requirement for maximum feed utilization was found to be .79%. Feed utilization of birds on all test diets containing supplemental Thr differed significantly from that of birds on both the unsupplemented basal diet and the corn-soybean meal-positive control diet. The results of these studies indicate that the Thr requirement for body weight gains of the young broiler chicken to 21 days of age is less than the .80% suggested by the NRC (1984) and appears to be no more than .68%. For maximum feed utilization, however, the results of our studies agree well with the NRC (1984) requirement.
The Thr requirement estimated in these studies was greater than either the .53% Thr found by Hewitt and Lewis (1972) for 7 to 21day-old chicks or the .50 to .52% Thr determined by Woodham and Deans (1975) for 14 to 28-day-old broiler chicks. However, the Thr requirement for gain determined in this study was in close agreement with the .67% Thr requirement determined by Thomas et al. (1986). The requirement of Thr for maximum feed utilization found in this study is in good agreement with the .82% reported by Thomas et al. (1979) and slightly greater than the level of .71% found by Thomas et al. (1986). In conclusion, the results of this study indicate that the Thr requirement for body weight gains of the young broiler chick appear to be less than the .80% suggested by the NRC (1984) and appear to be not more than .68%. Higher levels, similar to the .80% suggested by the NRC (1984), are needed for maximum feed utilization. ACKNOWLEDGMENTS
This study was conducted with the financial and laboratory support of Heartland Lysine,
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.56 .62 .68 .74 .80 .86 .92 Corn-soy control 6 Pooled SEM7
112
SMITH, JR AND WALDROUP
Inc., Chicago, IL and with the technical assistance of Merck Farms, Springdale, AR. REFERENCES
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF ARIZONA on April 19, 2015
Almquist, H. J., 1947. Evaluation of amino acid requirements by observation of the chick. J. Nutr. 34:543563. Almquist, H. J., and C. R. Grau, 1944. The amino acid requirements of the chick. J. Nutr. 28:325-331. Bhargava, K. K., R. P. Hanson, and M. L Sunde, 1971. Effects of threonine on growth and antibody production in chicks infected with Newcastle disease virus. Poultry Sci. 50:710-713. Davis, A. J., and R. E. Austic, 1982. Threonine imbalance and the threonine requirement of the chicken. J. Nutr. 112:2170-2176. Grau, C. R., 1949. The threonine requirement of the chick. J. Nutr. 37:105-113. Hewitt, D., and D. Lewis, 1972. The amino acid requirements of the growing chick. 1. Determination of amino acid requirements. Br. Poult. Sci. 13:449-463. Klain, G. J., H. M. Scott, and B. C. Johnson, 1960. The amino acid requirement of the growing chick fed a crystalline amino acid diet. Poultry Sci. 39:39-44. Krautman, B. A., S. M. Hauge, E. T. Mertz, and C. W. Carrick, 1958. Phenylalanine and threonine levels for young chicks. Poultry Sci. 37:535-538. National Research Council, 1984. Nutrient Requirements
of Domestic Animals. Nutrient Requirements of Poultry. 8th ed. Natl. Acad. Sci., Washington, DC. SAS Institute Inc., 1982. SAS User's Guide: Statistics. SAS Inst. Inc., Cary, NC. Thomas, O. P., and E. H. Bossard, 1982. Amino acid requirements for broiler males and females. Pages 34— 38 in: Proc. Maryland Nutr. Conf., Univ. Maryland, College Park, MD. Thomas, O. P., P. V. Twining, Jr., E. H. Bossard, J. L. Nicholson, and M. Rubin, 1979. Broiler chick studies with threonine and lysine. Pages 44-48 in: Proc. Maryland Nutr. Conf., Univ. Maryland, College Park, MD. Thomas, O. P., A. I. Zuckerman, M. Farran, and C. B. Tamplin, 1986. Updated amino acid requirements of broilers. Pages 79-85 in: Proc. Maryland Nutr. Conf., Univ. Maryland, College Park, MD. Uzu, G., 1986. Threonine requirement for broilers. A.E.C. Information Poultry 252. 03600 Commentry, France. Waldroup, P. W., R. J. Mitchell, J. R. Payne, and K. R. Hazen, 1976. Performance of chicks fed diets formulated to minimize excess levels of essential amino acids. Poultry Sci. 55:243-253. Watkins, S. E., 1986. An estimation of the requirements for non-essential amino acids by the broiler chicken. M. S. Thesis. University of Arkansas, Fayetteville, AR. Woodham, A. A., and P. S. Deans, 1975. Amino acid requirement of growing chickens. Br. Poult. Sci. 16:269-287.
1988 Poultry Science 67:108-112 INTRODUCTION
For approximately 30 years, methionine supplements have been routinely used to fortify soybean meal-based diets for broiler chickens. Through the use of this amino acid to overcome one of the major nutrient shortcomings of soybean meal, the overall protein content of broiler diets can be reduced without adversely affecting the performance of the chicken (Waldroup et al., 1976). Although lysine supplements have been available for approximately the same time, they have not been used as extensively. Soybean meal is a relatively good source of lysine, and the cost of lysine supplements has not been as favorable as methionine supplements. Therefore, the use of lysine in broiler feeds has been rather sporadic and inconsistent. Another factor that has limited the use of lysine in broiler diets has been an uncertainty about the levels of other essential amino acids that are needed in the diet. When lysine and methionine supplements are used to fortify broiler diets, the total crude protein content de-
Published with the approval of the Director, Arkansas Agricultural Experiment Station. 2 To whom correspondence should be addressed.
clines, usually accompanied by a decline in the level of other essential amino acids. There has been little work done using diets of a practical nature to delineate the requirements for amino acids other than methionine and lysine. A number of excellent studies with purified diets have been conducted, but requirements developed using these diets have not been directly convertible to more practical diets because of a number of factors such as digestibility of the amino acids in different feedstuffs and amino acid balance. Among the amino acids of interest in diets containing reduced protein levels is threonine (Thr), which appears to be limiting in low protein diets, especially those based on grain sorghum. Almquist and Grau (1944) reported that 1.0% DL-Thr was not sufficient for optimum growth whereas 2.0% appeared adequate. Almquist (1947) concluded that certain proteins were capable of supporting optimal chick growth when providing no more than .6% Thr. Grau (1949) indicated that .5% DL-Thr was insufficient for satisfactory growth, and 1.0% DL-Thr was satisfactory. Also, .3% L-Thr was inadequate but .5% L-Thr was satisfactory for growth. Chicks fed .45% L-Thr grew as well as those fed .5% L-Thr. Krautman et al. (1958) concluded that the L-Thr requirement of 7 to
108
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF ARIZONA on April 19, 2015
ABSTRACT Three trials were conducted to estimate the threonine (Thr) requirement of male broiler chicks. Chicks 7 days of age were fed a grain sorghum-soybean meal diet containing .59% Thr, supplemented with 0, .05, .09, .15, .22, .27, or .28% L-Thr. Levels of basal and supplemental amino acids were confirmed by ion-exchange chromatography. Diets were fed for 18 or 20 days, depending upon the trial. A corn-soybean meal diet analyzed to contain .90% Thr was used for comparison. Results of the three trials were pooled for determination of Thr requirements. A significant improvement in gain was observed when the basal grain sorghum-soybean meal diet was supplemented with .09% supplemental Thr (total .68% Thr). No further improvements in gain were observed at higher levels of Thr supplementation. Body weight gain of chicks fed the Thr-supplemented diets did not differ significantly from that of chicks fed the corn-soybean meal control diet. For maximum feed utilization, the Thr requirement was .79%, as estimated by regression analysis. This is in agreement with the .80% requirement suggested by the National Research Council in 1984. "Feed utilization of chicks fed the corn-soybean meal diet was significantly better than that of chicks fed any of the grain sorghum-soybean meal diets regardless of the level of Thr supplementation. (Key words: threonine, nutrition requirements, amino acids, body weight, feed conversion)
THREONINE REQUIREMENTS OF BROILERS MATERIALS AND METHODS
Using linear programming, a diet was formulated to meet the nutrient needs of the young (0 to 3 wk old) broiler chick as suggested by NRC (1984). Nutrient composition values provided by the NRC were used. The computer was directed to meet the minimum nutrient needs and provide the lowest amount of Thr possible with the combination of ingredients available. All other amino acids were provided at a minimum of 110% of the suggested NRC (1984) standards for the young chick. Composition of the basal diet is shown in Table 1. The diet was calculated to contain 3.2 kcal metabolizable energy per gram of feed and 15.34% crude protein from the intact protein sources. All diets were supplemented with sodium bicarbonate (.50%) and aluminum hydroxide (.30%) as buffers and antacids. Previous work from our laboratory (Watkins, 1986) indicated that corn-soybean meal-meat and bone meal diets with 15% crude protein from intact ingredients, fortified with sufficient amounts of amino acids and buffered with sodium bicarbonate and aluminum hydroxide, can support broiler gains and feed utilization equivalent to that of diets with 23% crude protein. A corn-soybean meal positive-control diet was used during this series of studies (Table 1). This control diet contained 23% crude protein and met all nutrient requirements of the young chick. After mixing, all diets were pelleted using a laboratory-model California Pellet Mill (California Pellet Mill Co., Crawfordsville, IN). The basal diet was calculated to contain .56% Thr (Table 2). Aliquots of the basal diet were fortified with .06, .12, .18, .24, .30, and .36% L-Thr to provide calculated Thr levels of .62, .68, .72, .78, .84, and .92%, respectively. Aliquots of the mixed feeds were analyzed for amino acid content. Each of the eight diets (seven test and one corn-soybean meal control) was fed to six replicate pens of five male chicks. Three consecutive feeding trials were conducted in this study. Male chicks of a commercial broiler strain (Vantress x Arbor Acres) were obtained from a local hatchery and randomly assigned to pens in electrically heated Petersime battery brooders. For the first 7 days they were fed the cornsoybean meal control diet with 23% crude protein calculated to meet or exceed all of the nutrient requirements suggested by the NRC
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF ARIZONA on April 19, 2015
21-day old chicks was between .55 and .60%. Klain et al. (1960) calculated the Thr requirement to be .58% in 7 to 12 or 14-day old chicks. Bhargava et al. (1971) found no significant differences in body weight or feed utilization at levels greater than .7% dietary Thr. Hewitt and Lewis (1972) determined that the Thr requirement for male broiler chicks 7 to 21 days of age was not more than .53%. Woodham and Deans (1975) found the Thr requirement for 14 to 28day-old broiler chicks to be .50 to .52% of the diet in the presence of .91 to 1.41% glycine. Thomas et al. (1979) reported that .82% Thr was required in one experiment with .81% needed in the second, based upon feed conversion data. Highest weight gains were obtained at .86% Thr in the first study and .85% in the second study. Thomas and Bossard (1982) found that .87% Thr was adequate for gain and feed conversion for male chicks to 3 wk of age, whereas .82% was adequate for females. Davis and Austic (1982) reported that the addition of Thr increased growth and feed efficiency in 8 to 21-day old chicks, with these effects being significantly greater at .72% Thr than at the .68% level. Thomas et al. (1986) calculated the Thr requirement is .7% for 7 to 21-day old chicks, using regression analysis. Uzu (1986) conducted two trials to determine the Thr requirement of broilers from 1 to 21 days of age. The Thr level was .70% in the basal diet and .79% in the control diet in the first experiment. In the second trial, the Thr level was .68% in the basal diet and .76% in the control diet. When L-Thr was added to the basal diets, performance was equal to that of birds fed the control diet when Thr was present at .75% in the first experiment or .73% in the second experiment. Additional Thr supplementation produced no further improvements in gain or feed conversion. The current National Research Council (NRC, 1984) requirements are .80% from 0 to 3 wk, .74% from 3 to 6 wk and .68% from 6 to 8 wk. With the development of two domestic lysine manufacturing plants in the United States, there is great interest in defining the potential needs for amino acids other than methionine and lysine in the diet of broiler chickens. To estimate what the potential for supplemental Thr might be, studies were conducted to evaluate the needs for this amino acid in diets similar in content to those used in the broiler industry.
109
110
SMITH, JR AND WALDROUP TABLE 1. Composition of diets
Ingredient
Control
Test -
Total
ygi Kg,/
.00 40.00 26.00 726.65 104.00 40.00 9.00 11.00 5.00
563.80
.60
4.00 5.00 1.00
5.00 1.00 3.00 2.66 2.88 9.26 7.78 1.75
.00
50.00 .00
319.50 44.10 5.20 5.10 .00
.00
2.30
1.50
.00 .00 .00 .00 .00 .00 .00 .00 .00
1,000.00
1,000.00
.92 .72 .62 .66
1 Provides per kilogram of diet: 6,612 IU vitamin A; 2,204 ICU vitamin D 3 ; 6.6 1U vitamin E; 3.3 mg menadione; 5.5 mg riboflavin; 66 mg niacin; 8.8 mg pantothenic acid; 495 mg choline; 1.1 mg thiamin; 1.1 mg pyridoxine; .01 mg vitamin B 12 ; .11 mg biotin; .66 mg folacin; 125 mg ethoxyquin; .11 mg selenium. 2
Provides per kilogram of diet: 100 mg Fe; 100 mg Mn; 100 mg Zn; 10 mg Cu; 1 mg I.
(1984). At 7 days of age the chickens were individually weighed and divided into different weight subclasses. These subclasses were randomly divided among the replicate pens. After division, birds were wingbanded and individually weighed. From 7 to 20 days of age in the first trial and from 7 to 18 days of age in the second and third trials birds were fed the experimental diets in pellet form ad libitum. At the conclusion of the study, birds were again individually weighed and the weight gain was calculated. The total pen feed consumption was determined. Any bird that died during the study was weighed, and its weight was used to correct feed consumption. The data were analyzed using initial bird weight as a covariate. Effects of Thr level upon performance were examined by regression procedures in the Statistical Analysis System (SAS Institute Inc., 1982). Both linear and quadratic models were examined. In the absence of significant (P>.05) linear or quadratic response,
means were separated using repeated t tests with values generated by the LSMEANS option of the General Linear Models procedure of SAS. There were no treatment x trial interactions, so data from the three trials were combined for presentation. RESULTS AND DISCUSSION
Analyses of the diets for Thr content were in agreement with calculated values (Table 2). By actual analysis, the basal diet contained .59% Thr with added levels of Thr being .05%, .09%, .15%, .22%, .27%, and .28%. The analyzed Thr level of the corn-soybean meal control diet was .90%. The crude protein content (N x 6.25%) of the basal test diet with all supplemental amino acids other than the Thr was 20.0%. Body weight gains, corrected for initial weight at 7 days, are shown in Table 2. There was no significant (P>.05) linear or quadratic response to Thr levels for body weight gain. Higher Thr values-.68% vs. .59%-resulted in
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF ARIZONA on April 19, 2015
Yellow corn Corn gluten meal (60% protein) Meat and bone meal (50% protein) Grain sorghum Soybean meal (48.5% protein) Blended animal-vegetable fat Ground limestone Dicalcium phosphate Sodium bicarbonate Sodium chloride Vitamin premix 1 Trace mineral mix 2 Aluminum hydroxide DL-Methionine (98%) Cystine Lysine HC1 (98%) Arginine HC1 Isoleucine Tryptophan Phenylalanine Tyrosine Valine Glycine
THREONINE REQUIREMENTS OF BROILERS
111
TABLE 2. Influence of dietary threonine levels on performance of male broiler chickens* Dietary threonine Calculated2
Analyzed 3
Body weight gain"
Feed efficiency5
(g) 328 b 349ab 364 a 349 a b 360 a 342 a b 356 a b 365 a 12
(gain/feed)
.59 .64 .68 .74 .81 .86 .87
('»)
.613.c .654;be .660,bc .670 b .674 b .648 r c .667'be
.709 .008
a—d Means in columns with no common superscripts differ significantly (P<.05). Means of three experiments, each with six replicate groups of five male chicks of a commercial broiler strain. 1
2
Calculated from values of National Research Council (1984).
3
Determined by ion-exchange chromatography.
"Gain from 7 to 20 days (Trial 1) or 7 to 18 days (Trials 2 and 3). 5
Threonine requirement for feed utilization estimated to be .79% by regression analysis. Formulated to meet minimum nutrient standards established by the National Research Council (1984). Analyzed to contain .90% threonine. 6
7
SEM = Standard error of the mean.
significantly higher body weight gains; there were no further gains from higher levels of Thr. Gains of chicks fed .68% Thr did not differ from those of chicks fed the corn-soybean meal control diet with 23% protein. Feed utilization, expressed as gain per gram of feed consumed, was not as good on the unsupplemented grain sorghum-soybean meal test diet as on the corn-soybean meal control diet with 23% crude protein (Table 2). Addition of Thr to the basal grain sorghum-soybean meal diet resulted in significantly better feed utilization. By regression analysis, the Thr requirement for maximum feed utilization was found to be .79%. Feed utilization of birds on all test diets containing supplemental Thr differed significantly from that of birds on both the unsupplemented basal diet and the corn-soybean meal-positive control diet. The results of these studies indicate that the Thr requirement for body weight gains of the young broiler chicken to 21 days of age is less than the .80% suggested by the NRC (1984) and appears to be no more than .68%. For maximum feed utilization, however, the results of our studies agree well with the NRC (1984) requirement.
The Thr requirement estimated in these studies was greater than either the .53% Thr found by Hewitt and Lewis (1972) for 7 to 21day-old chicks or the .50 to .52% Thr determined by Woodham and Deans (1975) for 14 to 28-day-old broiler chicks. However, the Thr requirement for gain determined in this study was in close agreement with the .67% Thr requirement determined by Thomas et al. (1986). The requirement of Thr for maximum feed utilization found in this study is in good agreement with the .82% reported by Thomas et al. (1979) and slightly greater than the level of .71% found by Thomas et al. (1986). In conclusion, the results of this study indicate that the Thr requirement for body weight gains of the young broiler chick appear to be less than the .80% suggested by the NRC (1984) and appear to be not more than .68%. Higher levels, similar to the .80% suggested by the NRC (1984), are needed for maximum feed utilization. ACKNOWLEDGMENTS
This study was conducted with the financial and laboratory support of Heartland Lysine,
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.56 .62 .68 .74 .80 .86 .92 Corn-soy control 6 Pooled SEM7
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SMITH, JR AND WALDROUP
Inc., Chicago, IL and with the technical assistance of Merck Farms, Springdale, AR. REFERENCES
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