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Threonine requirements of laying hens
METABOLISM AND NUTRITION Threonine Requirements of Laying Hens T. ISHIBASHI,1 Y. OGAWA, T. ITOH, S. FUJIMURA, K. KOIDE, and R. WATANABE Faculty of Agriculture, Niigata University, Niigata-shi, 950-21, Japan and daily egg mass increased and then decreased linearly as dietary Thr increased. Plasma Thr increased slowly, then sharply with increasing dietary Thr levels. Using the broken-line model, the Thr requirements were estimated to be 0.425, 0.428, and 0.430% or 453, 456, and 458 mg/hen per d in Experiment 1 and 0.395, 0.404, and 0.400%, or 457, 467, and 462 mg/hen per d, in Experiment 2, for egg mass, feed efficiency, and plasma Thr concentration, respectively. These results indicate that the Thr requirements expressed as milligrams per hen per day as determined by plasma Thr concentration agree with those of laying performance.
(Key words: layer, plasma threonine, threonine requirement) 1998 Poultry Science 77:998–1002 agreed well with that of laying performance. Recently, Yamamoto and Ishibashi (1997a,b) reconfirmed that the Lys requirements determined by laying performance and plasma Lys concentration were in good agreement. The present study was conducted to evaluate the Thr requirement of laying hens reared in environmentally controlled and open house facilities as measured by laying performance and plasma Thr concentration.
INTRODUCTION The previous Thr requirement of laying hens (NRC, 1984, 1994) has been increased by 0.02% from 0.45 to 0.47%. There are only two available reports that studied the Thr requirement of laying hens. Huyghebaert and Butler (1991) found that 0.51% or 637 mg Thr per hen per d is adequate for egg mass and feed efficiency for a flock of medium weight laying hens producing an average of a 50-g egg daily from 28 to 38 wk of age. Yamazaki et al. (1997) demonstrated that 0.31, 0.45, and 0.40% or 384, 524, and 467 mg Thr per hen per d were needed for egg mass, feed efficiency, and plasma Thr concentration, respectively, for 32 to 42 wk of age. Threonine recommendations before 1974 were 440 mg per hen per d (Moran et al., 1967) and 500 mg per hen per d (Hurwitz and Bornstein, 1973). It has been well documented that the amino acid (AA) requirements determined by plasma AA concentration agree well with direct parameters such as growth, feed efficiency, and nitrogen balance in many species; i.e., chicks (Zimmerman and Scott, 1965), rats (Stockland et al., 1970), pigs (Mitchell et al., 1968), and young men (Young et al., 1972). In laying hens, Chi and Speers (1976) and Ishibashi (1985) reported that the Lys requirement determined by plasma Lys concentration
MATERIALS AND METHODS
Animals and Experimental Design Two thousand Single Comb White Leghorn Dekalb XL Link hens were given free access to a basal diet containing 16.0% CP and 2,900 kcal ME/kg in an open-sided house. At 29 and 39 wk of age, a BW distribution curve was created and birds with light and heavy BW were removed from the experiment. Average hen weight in both experiments was 171 ± 29 g. Only hens that had laid more than 7 eggs for the last 10 d were chosen for the experiment. Experiments 1 and 2 utilized 100 and 600 hens, respectively. Hens were housed in individual wire cages in an environmentally controlled room (22 ± 2 C and receiving 16 h light/d) in Experiment 1. Hens were raised in an open house in Experiment 2 (16 h light/d). Egg weight and feed intake were recorded every 2 d.
Received for publication June 16, 1997. Accepted for publication March 2, 1998. 1To whom correspondence should be addressed.
Abbreviation Key: AA = amino acid.
998
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ABSTRACT In order to determine the Thr requirement of laying hens, two experiments were conducted using laying performance and plasma Thr concentration as parameters. At 29 and 39 wk of age, 100 and 600 laying hens in Experiments 1 and 2, respectively, with average BW and high egg production rate, were randomized, housed in individual cages, and given free access to water and experimental diets with five graded levels of Thr: 0.31, 0.39, 0.46, 0.54, and 0.61% for 21 d in Experiment 1 and diets with 0.31, 0.36, 0.41, 0.46 and 0.51% Thr for 58 d in Experiment 2. On the last day of the experiment, blood samples were taken for determination of plasma amino acid concentration. Feed intake
999
THREONINE REQUIREMENT OF LAYING HENS TABLE 1. Composition of experimental diet Ingredients
Percentage
Grain sorghum Corn grain Wheat bran Corn gluten meal Soybean oil Limestone Ca3(PO4)2 NaCl Vitamin mineral premix1 Choline chloride Amino acid mixture2 Glutamic acid Calculated analysis CP, % ME, kcal/kg 1See 2See
(%) 42.20 30.70 5.50 4.40 1.00 9.63 1.42 0.32 0.30 0.32 2.22 2.22 14.4 2,900
Yamamoto and Ishibashi (1997a). Table 2.
Diets The same basal diets were used in Experiments 1 and 2. The diets were formulated using grain sorghum, corn, wheat bran and corn gluten meal. In order to meet 115% of NRC (1994) AA recommendations, crystalline L-form AA were supplemented (Tables 1 and 2), because it has been shown that laying hens at 30 to 60 wk of age need 115% of NRC (1994) AA recommendations (Okazaki et al., 1993). The dietary AA concentration was calculated from analytical data of dietary feedstuffs for all AA except Met, Cys, and Trp. The dietary composition of Met, Cys, and Trp were calculated from NRC (1994). Treatments consisted of five graded levels of Thr: 0.31, 0.39, 0.46, 0.54, and 0.61% in Experiment 1 and 0.31, 0.36, 0.41, 0.46, and 0.51% in Experiment 2. An equal concentration of Thr in place of Glu was added to all experimental treatments in both experiments.
AA Analysis The AA concentrations of feedstuffs were analyzed after heating at 110 C in 6N HCl for 20 h. The plasma AA concentrations of hens that laid on the day of blood sampling were determined by HPLC2 in the same way as described by Fujimura et al. (1994), because the plasma AA concentration was affected by oviposition (Okazaki et al., 1993).
2Shimazu
Co., Kyoto, Japan.
The Thr requirement was estimated using a broken-line model by Ohtsuka and Yoshihara (1975). One-way analysis of variance was employed using the General Linear Models procedure of SAS (SAS Institute, 1988). When differences among treatments were found, means were separated by the Least Significant Difference test (Snedecor and Cochran, 1980). Statements of significance were based on P < 0.05 unless otherwise stated.
RESULTS During each experiment, two hens receiving the lowest Thr treatment in Experiment 1, and 4, 2, 1, 3, and 0 laying hens from each respective treatment in Experiment 2, stopped laying because of molting. Data from molted hens were omitted. It took 10 d until the effects of dietary deficient or excess Thr levels on the egg production rate were noticed. Therefore, the data of laying performance for the 11 to 21 and 11 to 58-d experimental periods were used for calculation of Thr requirement. There were no relationships between dietary Thr levels and BW change or egg size in either experiment (Tables 3 and 4). Feed intake (Tables 1, and 2), egg mass (Figure 1) and feed efficiency (egg mass:feed intake, Figure 1) increased, and then decreased with increasing dietary Thr levels. The Thr requirements were estimated to be 0.425 and 0.428 for the maximum daily egg mass and feed efficiency in Experiment 1. At the Thr requirement, feed intake was 106.6 g per hen per d for maximum egg mass and feed efficiency. The Thr requirements for maximum egg mass and feed efficiency were estimated to be 453 and 456 mg per hen per d, respectively. The Thr requirements were estimated to be 0.395 and 0.404%, for the maximum daily egg mass and feed efficiency, respectively, in Experiment 2. When the Thr requirements were obtained, feed intake was 115.6 g
TABLE 2. Amino acid composition of amino acid mixture and experimental diet Amino acid
Amino acid mixture
Arg Gly+Ser His Ile Leu Lys Met+Cys Phe+Thr Thr Trp Val Glu
0.393
Experiment diet (%)
1Values
0.365 0.530 0.250 0.047 0 to 0.300 0.315 0.300 to 0
0.805 0.804 0.243 0.748 1.293 0.794 0.891 0.954 0.310 0.38 0.805
(115)1 (124) (115) (137) (115) (115) (115) to 0.610 (209) (115)
in parentheses are percentages to NRC requirements (1994).
Downloaded from http://ps.oxfordjournals.org/ at colostateuniv on June 30, 2015
Individual BW was recorded at the beginning and end of the experiment. At 1300 to 1500 h on the last day of the experiment, 0.4 mL of blood was taken from the brachial vein from 20 hens of each treatment.
Statistical Analysis
1000
ISHIBASHI ET AL. TABLE 3. Effects of dietary threonine levels on laying performance and plasma amino acid concentration of laying hens, Experiment 11 Dietary Thr
Number of hens
(%) 0.31 0.36 0.41 0.46 0.51 Pooled SE
18 20 20 20 20
Body weight
Plasma concentration
Initial
Change
Feed intake
Egg size
Gly
(g) 1,729 1,726 1,727 1,725 1,731 29
(g/d) –3.01 –1.09 –0.95 +0.69 –0.76 –0.20
(g/d) 102.5 104.8 106.9 106.7 105.9 2.9
(g) 57.1 56.4 56.7 56.2 56.5 1.3
447 439 434 409 413 29
Ser (nmol/mL) 1,008a 907ab 798b 764b 725b 67
a–cValues
in the same column with no common superscript differ significantly (P < 0.05). are means at 0 and 21 d for BW change, and from 11 to 21 d for feed intake and egg size. Values for plasma amino acid of concentration are means for 10 hens that laid eggs on the blood sampling day. 1Values
DISCUSSION Hens in Experiment 2 receiving the diet containing 0.50% Thr (identical to DeKalb recommendations) had
daily egg masses higher than DeKalb standards, suggesting that the diets in Experiment 2 were nutritionally adequate to support maximal egg production traits. The Thr requirements expressed as milligrams per hen per day obtained in Experiment 1 (453, 456, and 458 mg per hen per d) agreed with those in Experiment 2 (457, 467, and 462 mg per hen per d for egg mass, feed efficiency, and plasma Thr concentration). The Thr requirements expressed as percentages of diet estimated by egg mass, feed efficiency, and plasma Thr concentration in Experiment 1 (0.425, 0.428, and 0.430%), and (0.395, 0.404, and 0.400%) in Experiment 2 agreed with each other in both experiments. However, the Thr requirements expressed as percentages of diet in Experiment 1 (0.425, 0.428, and 0.430%) were higher than those in Experiment 2 (0.395, 0.404, and 0.400%) for egg mass, feed efficiency, and plasma Thr concentration. In Experiment 2, the lowest and highest temperatures were recorded to be 13.3 and 26.5 C, respectively. Although these temperatures were within the thermoneutral zone of laying hens (12 to 25 C), the average temperature was lower than the 22 C in the environmentally controlled room in Experiment 1. Because feed intake increases as environmental temperature decreases, feed intake increased about 8.4% (106.6: 115.6) in Experiment 2. Therefore, the Thr requirements
TABLE 4. Effects of dietary threonine levels on laying performance and plasma amino acid concentration of laying hens, Experiment 21 Dietary Thr
Number of hens
(%) 0.31 0.36 0.41 0.46 0.51 Pooled SE
116 118 119 117 120
a–dValues
Body weight
Plasma concentration
Initial
Change
Feed intake
Egg size
Gly
(g) 1,733 1,721 1,729 1,734 1,737 38
(g/d) –1.72 0.11 –0.14 –0.15 –0.80 0.11
(g/d) 109.8 114.7 115.6 112.3 109.0 7.1
(g) 57.0 56.8 56.5 57.3 57.2 0.4
458 423 432 412 449 26
Ser (nmol/mL) 1,109a 966b 725d 711d 793c 54
in the same column with no common superscript differ significantly (P < 0.05). for BW change, feed intake, and egg size are means for 11 to 58 d of experiment, and those for plasma amino acid concentration are means for 10 hens that laid an egg on the blood sampling day. 1Values
Downloaded from http://ps.oxfordjournals.org/ at colostateuniv on June 30, 2015
per hen per d for maximum egg mass and feed efficiency. The Thr requirements for maximum egg mass and feed efficiency were estimated to be 457 and 467 mg per hen per d, respectively. The plasma Thr concentration increased slowly, and then linearly with increasing dietary Thr levels in both experiments (Figure 1). From the intersection of both lines, the requirements were estimated to be 0.431% in Experiment 1 and 0.399% in Experiment 2. At these Thr requirements, feed intakes were 106.2 and 114.4 g per hen per d in Experiments 1, and 2, respectively. The Thr requirements were estimated to be 458 and 456 mg per hen per d, respectively, for plasma Thr concentration. The plasma Gly concentration was not affected by changes in dietary Thr levels, but the plasma Ser concentration decreased linearly and then increased slowly as dietary Thr was increased. The break points were estimated to be 0.411% in Experiment 1 and 0.440% in Experiment 2, respectively. There was no clear relationship between dietary Thr and other plasma essential AA concentrations (data not presented).
THREONINE REQUIREMENT OF LAYING HENS
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expressed as percentages of diet in Experiment 2 resulted in lower Thr estimated than those in Experiment 1 due to feed intake. Using data of Yamazaki and Kaku (1988), the digestibility of Thr in this study was calculated to be 87.7%. Therefore, the digestible Thr requirements were estimated to be 397, 400, and 405 mg per hen per d in Experiment 1, and 401, 410, and 405 mg per hen per d for egg mass, feed efficiency, and plasma Thr concentration in Experiment 2, respectively. Egg contained 5.52 mg/g Thr. The efficiency of digestible Thr for the maximum egg mass was calculated to be 74.5% (5.52 × 54.0/400 × 100) and 71.4% (5.52 × 53.2/410 × 100), respectively, in Experiments 1 and 2, respectively. The values obtained in Experiments 1 and 2 indicated that the Thr requirements determined by plasma Thr concentration agreed with those by laying performance. Thus, future research on Thr requirements of laying hens may utilize small numbers of hens if plasma Thr is the parameter of interest. The Thr requirements determined in this study, however, were far lower than those of 700 to 710 mg per hen per d reported by Huyghebaert and Butler (1991) and higher than those of 329 (digestible) and 387 mg per hen per d (total) by Yamazaki et al. (1997). This wide range may be due to factors affecting the requirements such as strain of hens, age of hens, egg production rate, dietary CP levels, and each dietary AA level. Polbrow and Morris (1974) reported that there were no differences in Lys requirements among eight strains of laying hens. The age of laying hens did not differ so widely, 29 to 32, and 39 to 47 wk in this study, 32 to 42 wk in the study of Huyghebaert and Butler (1991), and 39 to 47 wk of age in the study of Yamazaki et al. (1997). The maximum egg mass in grams per hen per day was 53.9 and 53.2 in this study, 52.6 in the study of Huyghebaert and Butler (1991), and 49.9 in the study of Yamazaki et al. (1997), respectively. Yamamoto and Ishibashi (1997b), determined that the Lys requirements increase with dietary CP or AA levels. The dietary CP levels were 14.4 in this study, 9.6 to 16.0% in the study of Huyghebaert and Butler (1991), and 15.0%, in the study of Yamazaki et al. (1997). Therefore, these differences in strain of hens, age, egg mass, dietary CP levels, or a combination of them may be a factor in the differences in the Thr requirements among the above three studies. As the dietary Thr exceeded the requirement level, egg mass and feed efficiency decreased with increasing dietary Thr levels. In broilers, addition of excess Lys reduces BW gain, but the reduced BW gain is alleviated by addition of Arg due to the structural relationship of these AA (Ueno et al., 1994), and the growth depression
1001
FIGURE 1. Effects of dietary threonine levels on egg mass, feed efficiency, and plasma concentration of laying hens in Experiments 1 (◊) and 2 (o). Each value is the means ± SE for 10 hens.
1002
ISHIBASHI ET AL.
by dietary excess Met is alleviated by Thr of Gly addition (Ohta and Ishibashi, 1994). However, there is no report that the dietary excess of Thr induces the Met deficiency. Kidd et al. (1996) demonstrated that increasing dietary Thr above a finishing broiler requirement increases breast meat yield with little effect on BW. The reason that laying performance is reduced by excess Thr levels remains to be clarified.
REFERENCES
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Chi, M. S., and G. M. Speers, 1976. Effects of dietary protein and lysine levels on plasma amino acids, nitrogen retention and egg production in laying hens. J. Nutr. 106: 1192–1201. Fujimura, S., A. Yamamoto, K. Kobayashi, and T. Ishibashi, 1994. Comparison of performance of amino acid analysis with high performance liquid chromatograph equipped with sodium and lithium type column. Bull. Fac. Agric. Niigata Univ. 46:71–77. Hurwitz, S., and S. Bornstein, 1973. The protein and amino acid requirements of laying hens: Suggested models for calculation. Poultry Sci. 52:1124–1134. Huyghebaert, G., and E. A. Butler, 1991. Optimum threonine requirement of laying hens. Br. Poult. Sci. 32:575–582. Ishibashi, T., 1985. Lysine requirement of laying hens. Jpn. Zootech. Sci. 56:827–834. Kidd, T. M., B. Kerr, J. D. Firman, and S. P. Boling, 1996. Growth and carcass of broilers fed low-protein, threoninesupplemented diets. J. Appl. Poult. Res. 5:180–190. Mitchell, J. R., Jr., D. E. Becker, A. H. Harmon, and H. W. Norton, 1968. Determination of amino acid needs of the young pig nitrogen balance and plasma free amino acids. J. Anim. Sci. 27:1327–1331. Moran, E. T., Jr., J. D. Summers, and W. F. Pepper, 1967. Effect of non-protein nitrogen supplementation of low protein ratios on laying hen performance with a note on essential amino acid requirements. Poultry Sci. 46:1134–1144. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. National Research Council, 1994. Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press. Washington, DC.
Ohta, Y., and T. Ishibashi, 1994. Effect of dietary glycine on reduced performance by deficient and excessive methionine in broilers. Jpn. Poult. Sci. 31:369–380. Ohtsuka, Y., and M. Yoshihara, 1975. Fitting a family of intersecting regression models with one or two intersection points. Appl. Statis. 5:29–39. Okazaki, Y., K. Totsuka, A. Fukazawa, E. Watanabe, M. Toyomizu, and T. Ishibashi, 1993. Relationship of oviposition, feed consumption and body weight to plasma amino acid concentration of laying hens. Anim. Sci. Technol. (Jpn.) 64:364–370. Pobrow, P. J., and T. R. Morris, 1974. Composition of lysine requirements amongst eight stocks of laying fowl. Br. Poult. Sci. 15:51–73. SAS Institute, 1988. SAS User’s Guide. Version 5 Edition. SAS Institute Inc., Cary, NC. Snedecor, G. W., and W. G. Cochran, 1980. Statistical Methods. 7th ed. Iowa University Press, Ames, IA. Stockland, W. L., J. L. Meade, and J. L. Melliere, 1970. Lysine requirement of the growing rat: Plasma free lysine as a response criterion. J. Nutr. 100:925–933. Ueno, K., K. Koide, and T. Ishibashi, 1994. Factors affecting arginine requirement in broilers. Anim. Sci. Technol. (Jpn.) 65:9–15. Yamamoto, A., and T. Ishibashi, 1997a. Usefulness of plasma lysine concentration as a parameter to estimate lysine requirement in a shorter period in laying hens. Anim. Sci. Technol. (Jpn.) 68:360–366. Yamamoto, A., and T. Ishibashi, 1997b. Lysine requirements in a farm. Anim. Sci. Technol. (Jpn.) 68:529–536. Yamazaki, M., and K. Kaku, 1988. Chemical composition, metabolizable energy value and available amino acid composition of feedstuffs for poultry in Japan. Memories of Natl. Inst. Anim. Indust. 1:1–35. Yamazaki, M., H. Ohguchi, H. Murakami, M. Takemasa, M. Ando, and M. Yamazaki, 1997. Available threonine requirement of laying hens. (in Japanese). Jpn. Poult. Sci. 34:52–57. Young, V. R., K. Tontisirin, I. Ozalp, F. Lakshmanan, and N. S. Scrimshaw, 1972. Plasma amino acid response curve and amino acid requirements in young men: valine and lysine. J. Nutr. 102:1159–1169. Zimmerman, R. A., and H. M. Scott, 1965. Interrelationship of plasma amino acid levels and weight gain in the chicks as influenced by suboptimal and superoptimal dietary concentrations of single amino acids. J. Nutr. 87:13–18.
(Key words: layer, plasma threonine, threonine requirement) 1998 Poultry Science 77:998–1002 agreed well with that of laying performance. Recently, Yamamoto and Ishibashi (1997a,b) reconfirmed that the Lys requirements determined by laying performance and plasma Lys concentration were in good agreement. The present study was conducted to evaluate the Thr requirement of laying hens reared in environmentally controlled and open house facilities as measured by laying performance and plasma Thr concentration.
INTRODUCTION The previous Thr requirement of laying hens (NRC, 1984, 1994) has been increased by 0.02% from 0.45 to 0.47%. There are only two available reports that studied the Thr requirement of laying hens. Huyghebaert and Butler (1991) found that 0.51% or 637 mg Thr per hen per d is adequate for egg mass and feed efficiency for a flock of medium weight laying hens producing an average of a 50-g egg daily from 28 to 38 wk of age. Yamazaki et al. (1997) demonstrated that 0.31, 0.45, and 0.40% or 384, 524, and 467 mg Thr per hen per d were needed for egg mass, feed efficiency, and plasma Thr concentration, respectively, for 32 to 42 wk of age. Threonine recommendations before 1974 were 440 mg per hen per d (Moran et al., 1967) and 500 mg per hen per d (Hurwitz and Bornstein, 1973). It has been well documented that the amino acid (AA) requirements determined by plasma AA concentration agree well with direct parameters such as growth, feed efficiency, and nitrogen balance in many species; i.e., chicks (Zimmerman and Scott, 1965), rats (Stockland et al., 1970), pigs (Mitchell et al., 1968), and young men (Young et al., 1972). In laying hens, Chi and Speers (1976) and Ishibashi (1985) reported that the Lys requirement determined by plasma Lys concentration
MATERIALS AND METHODS
Animals and Experimental Design Two thousand Single Comb White Leghorn Dekalb XL Link hens were given free access to a basal diet containing 16.0% CP and 2,900 kcal ME/kg in an open-sided house. At 29 and 39 wk of age, a BW distribution curve was created and birds with light and heavy BW were removed from the experiment. Average hen weight in both experiments was 171 ± 29 g. Only hens that had laid more than 7 eggs for the last 10 d were chosen for the experiment. Experiments 1 and 2 utilized 100 and 600 hens, respectively. Hens were housed in individual wire cages in an environmentally controlled room (22 ± 2 C and receiving 16 h light/d) in Experiment 1. Hens were raised in an open house in Experiment 2 (16 h light/d). Egg weight and feed intake were recorded every 2 d.
Received for publication June 16, 1997. Accepted for publication March 2, 1998. 1To whom correspondence should be addressed.
Abbreviation Key: AA = amino acid.
998
Downloaded from http://ps.oxfordjournals.org/ at colostateuniv on June 30, 2015
ABSTRACT In order to determine the Thr requirement of laying hens, two experiments were conducted using laying performance and plasma Thr concentration as parameters. At 29 and 39 wk of age, 100 and 600 laying hens in Experiments 1 and 2, respectively, with average BW and high egg production rate, were randomized, housed in individual cages, and given free access to water and experimental diets with five graded levels of Thr: 0.31, 0.39, 0.46, 0.54, and 0.61% for 21 d in Experiment 1 and diets with 0.31, 0.36, 0.41, 0.46 and 0.51% Thr for 58 d in Experiment 2. On the last day of the experiment, blood samples were taken for determination of plasma amino acid concentration. Feed intake
999
THREONINE REQUIREMENT OF LAYING HENS TABLE 1. Composition of experimental diet Ingredients
Percentage
Grain sorghum Corn grain Wheat bran Corn gluten meal Soybean oil Limestone Ca3(PO4)2 NaCl Vitamin mineral premix1 Choline chloride Amino acid mixture2 Glutamic acid Calculated analysis CP, % ME, kcal/kg 1See 2See
(%) 42.20 30.70 5.50 4.40 1.00 9.63 1.42 0.32 0.30 0.32 2.22 2.22 14.4 2,900
Yamamoto and Ishibashi (1997a). Table 2.
Diets The same basal diets were used in Experiments 1 and 2. The diets were formulated using grain sorghum, corn, wheat bran and corn gluten meal. In order to meet 115% of NRC (1994) AA recommendations, crystalline L-form AA were supplemented (Tables 1 and 2), because it has been shown that laying hens at 30 to 60 wk of age need 115% of NRC (1994) AA recommendations (Okazaki et al., 1993). The dietary AA concentration was calculated from analytical data of dietary feedstuffs for all AA except Met, Cys, and Trp. The dietary composition of Met, Cys, and Trp were calculated from NRC (1994). Treatments consisted of five graded levels of Thr: 0.31, 0.39, 0.46, 0.54, and 0.61% in Experiment 1 and 0.31, 0.36, 0.41, 0.46, and 0.51% in Experiment 2. An equal concentration of Thr in place of Glu was added to all experimental treatments in both experiments.
AA Analysis The AA concentrations of feedstuffs were analyzed after heating at 110 C in 6N HCl for 20 h. The plasma AA concentrations of hens that laid on the day of blood sampling were determined by HPLC2 in the same way as described by Fujimura et al. (1994), because the plasma AA concentration was affected by oviposition (Okazaki et al., 1993).
2Shimazu
Co., Kyoto, Japan.
The Thr requirement was estimated using a broken-line model by Ohtsuka and Yoshihara (1975). One-way analysis of variance was employed using the General Linear Models procedure of SAS (SAS Institute, 1988). When differences among treatments were found, means were separated by the Least Significant Difference test (Snedecor and Cochran, 1980). Statements of significance were based on P < 0.05 unless otherwise stated.
RESULTS During each experiment, two hens receiving the lowest Thr treatment in Experiment 1, and 4, 2, 1, 3, and 0 laying hens from each respective treatment in Experiment 2, stopped laying because of molting. Data from molted hens were omitted. It took 10 d until the effects of dietary deficient or excess Thr levels on the egg production rate were noticed. Therefore, the data of laying performance for the 11 to 21 and 11 to 58-d experimental periods were used for calculation of Thr requirement. There were no relationships between dietary Thr levels and BW change or egg size in either experiment (Tables 3 and 4). Feed intake (Tables 1, and 2), egg mass (Figure 1) and feed efficiency (egg mass:feed intake, Figure 1) increased, and then decreased with increasing dietary Thr levels. The Thr requirements were estimated to be 0.425 and 0.428 for the maximum daily egg mass and feed efficiency in Experiment 1. At the Thr requirement, feed intake was 106.6 g per hen per d for maximum egg mass and feed efficiency. The Thr requirements for maximum egg mass and feed efficiency were estimated to be 453 and 456 mg per hen per d, respectively. The Thr requirements were estimated to be 0.395 and 0.404%, for the maximum daily egg mass and feed efficiency, respectively, in Experiment 2. When the Thr requirements were obtained, feed intake was 115.6 g
TABLE 2. Amino acid composition of amino acid mixture and experimental diet Amino acid
Amino acid mixture
Arg Gly+Ser His Ile Leu Lys Met+Cys Phe+Thr Thr Trp Val Glu
0.393
Experiment diet (%)
1Values
0.365 0.530 0.250 0.047 0 to 0.300 0.315 0.300 to 0
0.805 0.804 0.243 0.748 1.293 0.794 0.891 0.954 0.310 0.38 0.805
(115)1 (124) (115) (137) (115) (115) (115) to 0.610 (209) (115)
in parentheses are percentages to NRC requirements (1994).
Downloaded from http://ps.oxfordjournals.org/ at colostateuniv on June 30, 2015
Individual BW was recorded at the beginning and end of the experiment. At 1300 to 1500 h on the last day of the experiment, 0.4 mL of blood was taken from the brachial vein from 20 hens of each treatment.
Statistical Analysis
1000
ISHIBASHI ET AL. TABLE 3. Effects of dietary threonine levels on laying performance and plasma amino acid concentration of laying hens, Experiment 11 Dietary Thr
Number of hens
(%) 0.31 0.36 0.41 0.46 0.51 Pooled SE
18 20 20 20 20
Body weight
Plasma concentration
Initial
Change
Feed intake
Egg size
Gly
(g) 1,729 1,726 1,727 1,725 1,731 29
(g/d) –3.01 –1.09 –0.95 +0.69 –0.76 –0.20
(g/d) 102.5 104.8 106.9 106.7 105.9 2.9
(g) 57.1 56.4 56.7 56.2 56.5 1.3
447 439 434 409 413 29
Ser (nmol/mL) 1,008a 907ab 798b 764b 725b 67
a–cValues
in the same column with no common superscript differ significantly (P < 0.05). are means at 0 and 21 d for BW change, and from 11 to 21 d for feed intake and egg size. Values for plasma amino acid of concentration are means for 10 hens that laid eggs on the blood sampling day. 1Values
DISCUSSION Hens in Experiment 2 receiving the diet containing 0.50% Thr (identical to DeKalb recommendations) had
daily egg masses higher than DeKalb standards, suggesting that the diets in Experiment 2 were nutritionally adequate to support maximal egg production traits. The Thr requirements expressed as milligrams per hen per day obtained in Experiment 1 (453, 456, and 458 mg per hen per d) agreed with those in Experiment 2 (457, 467, and 462 mg per hen per d for egg mass, feed efficiency, and plasma Thr concentration). The Thr requirements expressed as percentages of diet estimated by egg mass, feed efficiency, and plasma Thr concentration in Experiment 1 (0.425, 0.428, and 0.430%), and (0.395, 0.404, and 0.400%) in Experiment 2 agreed with each other in both experiments. However, the Thr requirements expressed as percentages of diet in Experiment 1 (0.425, 0.428, and 0.430%) were higher than those in Experiment 2 (0.395, 0.404, and 0.400%) for egg mass, feed efficiency, and plasma Thr concentration. In Experiment 2, the lowest and highest temperatures were recorded to be 13.3 and 26.5 C, respectively. Although these temperatures were within the thermoneutral zone of laying hens (12 to 25 C), the average temperature was lower than the 22 C in the environmentally controlled room in Experiment 1. Because feed intake increases as environmental temperature decreases, feed intake increased about 8.4% (106.6: 115.6) in Experiment 2. Therefore, the Thr requirements
TABLE 4. Effects of dietary threonine levels on laying performance and plasma amino acid concentration of laying hens, Experiment 21 Dietary Thr
Number of hens
(%) 0.31 0.36 0.41 0.46 0.51 Pooled SE
116 118 119 117 120
a–dValues
Body weight
Plasma concentration
Initial
Change
Feed intake
Egg size
Gly
(g) 1,733 1,721 1,729 1,734 1,737 38
(g/d) –1.72 0.11 –0.14 –0.15 –0.80 0.11
(g/d) 109.8 114.7 115.6 112.3 109.0 7.1
(g) 57.0 56.8 56.5 57.3 57.2 0.4
458 423 432 412 449 26
Ser (nmol/mL) 1,109a 966b 725d 711d 793c 54
in the same column with no common superscript differ significantly (P < 0.05). for BW change, feed intake, and egg size are means for 11 to 58 d of experiment, and those for plasma amino acid concentration are means for 10 hens that laid an egg on the blood sampling day. 1Values
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per hen per d for maximum egg mass and feed efficiency. The Thr requirements for maximum egg mass and feed efficiency were estimated to be 457 and 467 mg per hen per d, respectively. The plasma Thr concentration increased slowly, and then linearly with increasing dietary Thr levels in both experiments (Figure 1). From the intersection of both lines, the requirements were estimated to be 0.431% in Experiment 1 and 0.399% in Experiment 2. At these Thr requirements, feed intakes were 106.2 and 114.4 g per hen per d in Experiments 1, and 2, respectively. The Thr requirements were estimated to be 458 and 456 mg per hen per d, respectively, for plasma Thr concentration. The plasma Gly concentration was not affected by changes in dietary Thr levels, but the plasma Ser concentration decreased linearly and then increased slowly as dietary Thr was increased. The break points were estimated to be 0.411% in Experiment 1 and 0.440% in Experiment 2, respectively. There was no clear relationship between dietary Thr and other plasma essential AA concentrations (data not presented).
THREONINE REQUIREMENT OF LAYING HENS
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expressed as percentages of diet in Experiment 2 resulted in lower Thr estimated than those in Experiment 1 due to feed intake. Using data of Yamazaki and Kaku (1988), the digestibility of Thr in this study was calculated to be 87.7%. Therefore, the digestible Thr requirements were estimated to be 397, 400, and 405 mg per hen per d in Experiment 1, and 401, 410, and 405 mg per hen per d for egg mass, feed efficiency, and plasma Thr concentration in Experiment 2, respectively. Egg contained 5.52 mg/g Thr. The efficiency of digestible Thr for the maximum egg mass was calculated to be 74.5% (5.52 × 54.0/400 × 100) and 71.4% (5.52 × 53.2/410 × 100), respectively, in Experiments 1 and 2, respectively. The values obtained in Experiments 1 and 2 indicated that the Thr requirements determined by plasma Thr concentration agreed with those by laying performance. Thus, future research on Thr requirements of laying hens may utilize small numbers of hens if plasma Thr is the parameter of interest. The Thr requirements determined in this study, however, were far lower than those of 700 to 710 mg per hen per d reported by Huyghebaert and Butler (1991) and higher than those of 329 (digestible) and 387 mg per hen per d (total) by Yamazaki et al. (1997). This wide range may be due to factors affecting the requirements such as strain of hens, age of hens, egg production rate, dietary CP levels, and each dietary AA level. Polbrow and Morris (1974) reported that there were no differences in Lys requirements among eight strains of laying hens. The age of laying hens did not differ so widely, 29 to 32, and 39 to 47 wk in this study, 32 to 42 wk in the study of Huyghebaert and Butler (1991), and 39 to 47 wk of age in the study of Yamazaki et al. (1997). The maximum egg mass in grams per hen per day was 53.9 and 53.2 in this study, 52.6 in the study of Huyghebaert and Butler (1991), and 49.9 in the study of Yamazaki et al. (1997), respectively. Yamamoto and Ishibashi (1997b), determined that the Lys requirements increase with dietary CP or AA levels. The dietary CP levels were 14.4 in this study, 9.6 to 16.0% in the study of Huyghebaert and Butler (1991), and 15.0%, in the study of Yamazaki et al. (1997). Therefore, these differences in strain of hens, age, egg mass, dietary CP levels, or a combination of them may be a factor in the differences in the Thr requirements among the above three studies. As the dietary Thr exceeded the requirement level, egg mass and feed efficiency decreased with increasing dietary Thr levels. In broilers, addition of excess Lys reduces BW gain, but the reduced BW gain is alleviated by addition of Arg due to the structural relationship of these AA (Ueno et al., 1994), and the growth depression
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FIGURE 1. Effects of dietary threonine levels on egg mass, feed efficiency, and plasma concentration of laying hens in Experiments 1 (◊) and 2 (o). Each value is the means ± SE for 10 hens.
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ISHIBASHI ET AL.
by dietary excess Met is alleviated by Thr of Gly addition (Ohta and Ishibashi, 1994). However, there is no report that the dietary excess of Thr induces the Met deficiency. Kidd et al. (1996) demonstrated that increasing dietary Thr above a finishing broiler requirement increases breast meat yield with little effect on BW. The reason that laying performance is reduced by excess Thr levels remains to be clarified.
REFERENCES
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