- Email: [email protected]
Efficiency of tryptophan-niacin conversion in chickens and ducks
Nutrition Research, Vol. 16, No. I, pp. 91-104, 1996 Copyright Q 1995 Elsevier Science Inc. Printed intheUSA. Allrightsreserved
0271-5317/96$15.00+.00 ELSEVIER
EFFICImCY
0271-5317(95)02063-2
OF TFtYPTOPEAN-NIACIN CONVRRSION AND DUCRS1
IN CBICRRNS
Bao-Ji Chen PhD'; Tian-Fuh Shen PhD'; Richard E. Austic PhD' 'Duck Research Center, Taiwan Livestock Research Institute, I-Lan, Taiwan, ROC 3Department of Animal Science, National Taiwan University Taipei, Taiwan, ROC 'Department of Poultry and Avian Sciences, Cornell University Ithaca, NY 14853
Experiments were conducted with Pekin ducklings, mule ducklings and broiler chicks to determine the efficiency of conversion of tryptophan to niacin. When were fed a diet marginal in tryptophan and chicks deficient in niacin, either tryptophan or niacin supplementation improved growth and prevented niacin deficiency symptoms. However, only niacin improved growth and prevented symptoms in Pekin or mule ducklings. Liver picolinic acid carboxylase (PAC) activity was 4 to 5 times higher in ducklings than in chicks. The activity the ratio of 3-hydroxyanthranilic acid of PAC and oxygenase (3-BAA01 activity to PAC activity in liver were significantly influenced by tryptophan or niacin in the diet in chicks but not in ducks. The efficiency of conversion of tryptophan to niacin was calculated from the relative responses in weight gains when graded levels of tryptophan or niacin were added to the diet. The results indicate that 181 mg, 172 mg and 47 mg of tryptophan are equivalent to 1 mg of niacin in Pekin ducklings, mule ducklings and broiler chicks, respectively. The duckling has a limited ability to use tryptophan to spare niacin. KEY WORDS:
Tryptophan-Niacin, Conversion Efficiency, Picolinic Carboxylase, Chickens, Ducks INTRODUCTION
It has been known for many years that tryptophan can counteract growth retardation in chicks (1) and ducks (2,3) that 'Supported by the Council of Agriculture,Taiwan, ROC. 'Current address: Department of Animal Science, National Taiwan University, Taipei, Taiwan, ROC. 'Current address: Department of Animal Science, 248 Morrison Hall, Cornell University, Ithaca, NY 14853. Telephone: 607-255-8497; Fax: 607-255-9829; email: [email protected].
91
92
B.-J. CHEN etal.
are fed diets limiting in niacin. Early studies on the extent to which tryptophan can substitute for niacin in chicks provided conflicting results (4,5,6,7). The quantitative conversion of tryptophan to niacin in chicks was first reported by Baker et al. (8) who indicated that 45 mg of dietary tryptophan is equivalent to 1 mg of niacin. Other investigations have provided similar estimates (9,10,11). The niacin requirement of mule ducks5 (3) and Pekin ducks (12,13) was reported to be 45 mg/kg and 55 mg/kg, respectively. This is nearly twice the requirement of Leghorn or broiler chicks (27 to 35 mg/kg; 13,14,15). The difference in requirement seems to be related to the efficiency of biosynthesis of NAD from tryptophan The efficiency is controlled, at least in part, by liver (9). picolinic acid carboxylase (PAC) activity (16). Picolinic acid carboxylase (aminocarboxymuconate-semialdehyde decarboxylase, EC of 2-amino-3catalyzes decarboxylation 4.1.1.451, the carboxymuconic-6-semialdehyde, an unstable intermediate formed by action of 3-hydroxyanthranilic acid oxygenase the (3hydroxyanthranilate 3,4-dioxygenase, EC 1.13.11.6) (3-BAA01 on 3hydroxyanthranilic acid. PAC diverts 2-amino-3-carboxymuconic-6semialdehyde toward the formation of CO, rather than toward the formation of quinolinic acid, an intermediate in the synthesis of Henderson and Swan (17) proposed the use of liver 3-IiAAO:PAC NAD. ratio to predict the efficiency with which dietary tryptophan serves as a source of dietary niacin - a lower ratio indicating less efficient conversion of tryptophan to niacin. Pekin ducks appear to have the highest liver PAC in poultry about 4 to 5 fold higher than that of chicks (9). species, However, the efficiency of conversion of tryptophan to niacin in The purpose of this work was to ducks has never been reported. investigate the difference in the efficiency of conversion of tryptophan to niacin in chicks and ducks, and to establish the quantitative efficiency for the conversion in ducks. MATERIALS
AND METHODS
Day-old broiler chickens (Arbor Acres Farm, Taiwan), Pekin ducklings (Duck ducklings (Cherry-Valley, Taiwan), and mule Research Center, Taiwan) were weighed, and assigned at random to experimental groups of eight birds each containing equal numbers of females and males. They were raised in electrically heated Birds were kept at brooders with wire floors (60 X 90 cm). temperatures of 32 and 28 (i 2 C) during the first week and second Water and feed were provided ad libitum. week, respectively. Three hundred and twelve birds of each kind were divided into triplicate groups of eight birds each in a factorial arrangement of 12 treatments with 3 levels of L-tryptophan (0, 0.02, and 0.04%) and 4 levels of niacin (0, 3, 6, and 9 mg/kg) added to the basal diet containing 0.16% tryptophan and 24.5 mg/kg niacin (Table 11, and one additional treatment of 0.08% L-tryptophan supplementation All amino acids for the diets were purchased from Ajinomoto only.
TRYPTOPHAN-NIACIN
CONVERSION
93
Company, Inc. (Tokyo, Japan) and niacin (crystalline nicotinic acid) was obtained from Merck & Co., Inc., Rahway, NJ. The crude protein (N X 6.251, moisture and niacin contents of the basal diet were determined according to the methods of the Association of Official Analytical Chemists (18). Body weights were determined prior to experiment, and at the end of the experiment after feed had been withheld for at least 2 hours. The number of birds showing niacin deficiency symptoms such as inflammation of the tongue and mouth and enlargement of the tibiotarsal joint in chicks, and bowed legs or hock enlargement in ducks was recorded. Six Birds were re-fed for 2 hours after the final weighing. birds from each treatment (2 per replicate) were killed by cervical dislocation. The livers and kidneys were removed, immediately frozen in liquid nitrogen and then analyzed for 3-BAA0 and PAC in duplicate with activities. Enzyme assays were conducted substrate blanks according to the spectrophotometric method of Mehler et al. (19) and using 4.5 X 10' as the molar extinction 2-amino-3-carboxymuconic-6-semialdehyde in the coefficient of calculation of enzyme activity (Nishizuka, et al., 20). feed efficiency (body weight Data on body weight gain, were subjected to gain/feed intake), 3-BAA0 and PAC activities (21) new multiple range test analysis of variance and Duncan's SAS program (Statistical Analysis System, using a computer Snedecor and Cochran's linear calibration formula and Institute). the the method of inverse prediction was used for evaluating efficiency of conversion of tryptophan to niacin (22).
RESULTS The effects of tryptophan and niacin on gross measures in Pekin ducklings is shown in Table 2. Ducklings fed the basal diet had lower body weight gain and higher incidence of deficiency symptoms than ducklings that received diets containing supplemental niacin. Increases in niacin level resulted in significant increases in body weight gain and feed efficiency (P c .05). feed efficiency was influenced by However, growth and not The incidence of deficiency symptoms supplemental tryptophan. to niacin, decreased in response but was not affected by Yortality was noted only at the lower niacin levels tryptophaa. and was prevented by niacin and the highest level of tryptophan. The responses of mule ducklings to tryptophan and niacin were similar to those of Pekin ducklings (Table 3).
'Sterile hybrids that were resulting from the mating
produced by crossing Muscovy drakes of Pekin drakes and Tsaiya ducks.
with
the P, female
94
B.-J. CHEN et al.
TABLE 1 Composition Composition
%
Corn, yellow Soybean meal (44% protein) Gelatin Cellulose' Soybean oil Amino acids' NaHCO, Choline-Cl (50%) Dicalcium phosphate Limestone, pulverized Salt, iodized Vitamin premix' Mineral premix4 Crude protein (%) Metabolizable energy Tryptophan (%I Niacin (mg/kg)
of the Basal Diet
(Kcal/Kg)
64.00 15.50 7.00 3.50 3.50 2.00 0.20 0.10 2.40 1.00 0.30 0.30 0.20 21.6 2970 0.16 24.5
'Solka Floe, Brown Co., Berlin, NH. 'Provided as % of diet: L-lysine.HCl, 0.38; DL-methionine, 0.43; L-arginine, 0.18; L-isoleucine, 0.13; L-threonine, 0.20; L-valine, 0.05; L-tyrosine, 0.15; L-glutamic acid, 0.48. 'Provided in IU per Kg diet: vitamin A, 6000; vitamin Do, 1000; vitamin E, 15; and in mg per Kg of diet: vitamin K, 2.0; thiaminHC1, 2.0; riboflavin, 5.0; Ca-pantothenate, 15.0; . * B,,; pyridoxineHC1 6.0; folic acid, 0.5; biotin, 0.15; vitamin 0.02; ethoxyquin, 100. 'Provided in mg per Kg diet: MnSO;H,O, 165; ZnO, 100; CuSO,'SH,O, 50; FeS0,'7H,O, 200; Na,SeO,, 0.22 increased weight gain and feed Niacin supplementation efficiency and decreased symptoms of niacin deficiency in chicks In contrast to the results with (Table 41, as in ducklings. alone increased body weight ducklings, tryptophan supplementation gain, feed efficiency, and decreased niacin deficiency symptoms. the deficiency When the dietary tryptophan level was 0.24%, The differences between were completely prevented. symptoms ducklings and chicks are readily apparent in the main effects of treatments (Table 5). The activity of liver PAC in chicks was approximately 30% that of ducklings and the ratio of 3-HAAO:PAC in chicks was twice as Both measures in ducklings were high as in ducklings (Table 6). unaffected by dietary tryptophan or niacin concentration. In chicks, however, PAC was decreased by tryptophan and increased by niacin (P c .05), and the ratio of 3-HAAO:PAC activities increased in response to tryptophan and decreased in response to niacin (P c .05).
TRYPTOPHAN-NIACIN
CONVERSION
95
TABLE 2 Effects of Tryptophan and Niacin on Growth, Feed Efficiency, Niacin Deficiency Symptoms and Mortality of Pekin Ducklings Dietary L-Trp
Niacin added
Body wt. gain
Feed efficiency
Incidence of niacin deficiency'
Mortality
%
mg/kg
g
gain/feed
%
%
0.16 0.18 0.20 0.24
0 0 0 0
65 81 67 108
06 86 86 28
a 8 4 0
0.16 0.18 0.20
3 3 3
91 f 12' 88 f 32' 100 f 29*
.31 f .03*= .30 f .04* .31 f .02*=
75 86 63
0 8 0
0.16 0.18 0.20
6 6 6
119 * 31*= 131 f 46*O 117 f 46*"
.37 f .03b"d .32 f .08*' .35 f .08*cd
29 21 41
0 0 0
0.16 0.18 0.20
9 9 9
167 f 3gb" 182 f 55" 107 f 63"
.46 f .02' .43 f .03d. .40 f .03**
25 8 0
0 0 0
f 16" f 7' f 20' f 27*
.26 -28 .28 .30
f f f f
.04* .02* .08* .oa*
'Percent of birds showing niacin deficiency symptoms. 'Mean f standard deviation. Means in the same column that do not have a common letter in their superscripts are significantly different (Pc.05).
The 3-HAAO activities of kidney were approximately SO%, 80% and 25%, respectively, of liver activities in Pekin ducklings, mule ducklings and broiler chicks, respectively (Table 6). The PAC activities of kidney and liver were similar in ducklings, but the PAC activity of kidney in chicks was 2.5-fold higher than that of The ratio of 3-FfAAO:PAC activities in duck kidney was liver. approximately one-half that of duck liver whereas the ratio in chick kidney was one-tenth that of chick liver. The activities of 3-HAAO and PAC in duck kidney were unaffected by dietary tryptophan and niacin concentrations. The activities in chick kidney were unaffected by tryptophan, but PAC activity was significantly increased by dietary niacin.
B.-J. CHEN et al.
96
TABLE 3 Effect of Tryptophan and Niacin on Growth, Peed Efficiency, Niacin Deficiency Symptoms and Mortality of Mule Ducklings Dietary L-Trp
Niacin added
Body wt. gain
Peed efficiency
Incidence of niacin deficiency'
Mortality
%
mg/kg
g
gain/feed
%
%
0.16 0.18 0.20 0.24
0 0 0 0
49 51 40 86
55 SO 61 23
a 0 4 0
0.16 0.18 0.20
3 3 3
67 f a*= 79 f 26*= 85 f 24bcd
.2s f .03bC .27 f .06bcd .29 f .05b=d
30 33 50
0 0 0
0.16 0.18 0.20
6 6 6
108 f g&i 106 f 20Cd* 98 f 22cd'
.31 f .03Ed' .29 f .03b"d .30 f .05fd'
25 21 25
0 0 0
0.16 0.18 0.20
9 9 9
123 * 26'*' 141 f 38" 149 f 33=
.30 f .03.= .35 f .o7d** .41 f .06'
0 0 4
0 0 4
f 0*b' f 19* f 11' f 23bcd
.20 .22 .16 .32
f f f f
.06& .05*= .03' .05-
'.'Refer to Table 2.
DISCUSSION The tryptophan level used in this experiment (0.16% to 0.20%) was marginal for both ducklings and chicks (13). The same dietary tryptophan level also was used by Baker et al. (8); Oduho and Baker (10); and Penz et al. (23) and a slightly lower level (.14%) was used by Oduho and Baker (10). The niacin content of the basal diet was 24.5 mg/kg, which is below the requirements for both chicks and ducklings (13). Thus, the experimental diet contained a tryptophan level marginally adequate for growth but was limiting in niacin. This is an appropriate condition for evaluating the efficiency of It is noteworthy that chicks conversion of tryptophan to niacin. This responded to dietary niacin supplementation up to 9 mg/kg. suggests that the bioavailable niacin concentration in the diet was This could explain considerably less than the analyzed content. the observed linear responses for growth of chicks to both tryptophan and niacin over the full range of the nutrients used in these studies.
TRYPTOPHAN-NIACIN
CONVERSION
97
TABLE 4 Effect of Tryptophan and Niacin on Growth, Feed Efficiency, Deficiency Symptoms and Mortality of Broiler Chicks Dietary L-Trp %
Niacin
Niacin added
Body wt. gain
Feed efficiency
Incidence of niacin deficiencv'
mdkg
B
gain/feed
%
%
.02* .04* .03"6' .04g
71 71 46 0
0 0
4 0
.45 f .03b' .48 f .06bC .59 f .o26'f
62 47 25
4 0 4 4 0 0
0.16 0.18 0.20 0.24
0 0 0 0
41 55 86 203
0.16 0.18 0.20
3 3 3
61 * 73 f 111 f
0.16 0.18 0.20
6 6 6
97 * 144" 120 f 16'O 150 f 1P
.51 f .00Od :61 62 f .08'
26 17 10
0.16 0.18 0.20
9 9 9
127 f 24gh 162 f 19' 200 + 23'
1.61 f .02' .65 f .03' .68 f .02fP
13 0 0
f 3.' f 3& gCd. f f 18' 5*= 7&d 8'm
.35 .42 .52 .73
f f f f
Mortality
0
8
"'Refer to Table 2.
Ducklings were not able to use tryptophan effectively to replace niacin under the conditions of this study. On the other hand, broiler chicks exhibited significant improvement in growth and feed utilization as well as reduced incidence of deficiency symptoms in response to dietary tryptophan or niacin. These results are in agreement with those of Fisher et al. (4) and Patterson et al. (5) which indicated that tryptophan could completely replace niacin in chick diets. It has been reported that ducks also have the ability to use tryptophan to spare niacin This effect was observed only in diets with very high (2,3). tryptophan levels (i.e., 0.60% tryptophan in the studies of Bernard and Deters (2); 0.33% tryptophan in the work of Wu et al. (3). It might be concluded that although the conversion of tryptophan to niacin is possible in ducks, it is very inefficient under normal dietary conditions.
98
B.-J. CHEN et al.
TABLE 5 The Main Effects of Tryptophan and Niacin on Body Weight Gain, Feed Efficiency and Niacin Deficiency Symptoms of Pekin Ducklings, Mule Ducklings and Broiler Chicks Pekin TrD
BWG=
(%I
9
0.16 0.18 0.20
111" 121' 118'
Niacin 0 3 6 9
ducklings FE1
0.35' 0.33' 0.33'
Mule
ducklings FE
Broiler
ID
BWF
%
g *
chicks
ID'
BWG
FE
ID
%
9
53 48 49
87' 94' 94‘
0.29' 0.28. 0.29.
31 25 35
1S 137'
0.48' 0.54b 0.60"
58 46 26
87 72 30 14
48' 77b 104" 1386
0.20. 0.27b 0.30b 0.38"
55 40 16 4
61' 81b 122" 163'
0.43' 0.51b 0.58" 0.65'
84 62 23 5
%
(ma/ku) 72' 93* 122b 179=
0.27' 0.31* 0.34b 0.43=
'Abbreviation: BWG: body weight gain; FE: feed efficiency (gain/intake). 'ID: % of birds showing niacin deficiency symptoms. 'Means for tryptophan or niacin treatments in the same column not having a conanon letter in their superscripts are significantly different (P<.O5). A comparison of the efficiency of conversion of tryptophan to niacin in chicks and ducklings was evaluated using the body weight gains from the 0.16%, 0.18% and 0.20% tryptophan groups. Linear calibration equations, based on the level of niacin supplementation (Y) of Pekin ducklings, (X1 and the body weight gains mule ducklings and broiler chicks, were calculated. The body weight gains of the birds that received 0.24% tryptophan and no niacin were compared to the reference response to predict the efficiency of conversion of tryptophan to niacin (Figure 1). Examples of the calculation using the 0.18% tryptophan groups are shown below: Pekin ducklings: Y = 68.45 + 11.57 X r = 0.960 0.06% Trp had the same effect as 3.42 mg/kg niacin. Therefore 175 mg Trp = 1 mg niacin. r = 0.998 Mule ducklings: Y = 49.62 + 9.92 X 0.06% Trp had the same effect as 3.66 mg/kg niacin. Therefore 164 mg Trp = 1 mg niacin (Figure 1). Broiler
chicks: Y - 47.37 + 12.27 X r = 0.986 had the same effect as 12.66 mg/kg niacin. Therefore 47 mg/kg Trp = 1 mg niacin. 0.06%
Trp
The conversion efficiency observed in chicks is similar to the efficiency reported by DiLorenzo (9); Baker et al. (8); Oduho and
TRYPTOPHAN-NIACIN
CONVERSION
99
The efficiency Baker (10); and Oduho et al. (11) (Table 7). This increase appeared to increase in the 0.20% tqptophan group. is consistent with the 3-EAAO:PAC ratio (Table 6) and could be expected on the basis of studies of the rat (24). However, the estimate of the conversion efficiency for the .20% tryptophan group may be less reliable because of the relatively small increment of dietary tryptophan (0.04%) used in the calculation versus the increments (0.08% and 0.06%, respectively) used for the calculation of efficiency in the 0.16% and 0.18% tryptophan groups. Ducklings had relatively high PAC activities and high ratios of 3-HAAO:PAC activity in liver and kidney as compared to chicks. This may be the reason for the different abilities of ducks and The results are in chicks to use tryptophan to replace niacin. agreement with the reports of Ikeda et al. (16) and DiLorenzo (9) indicating that the efficiency of conversion of tryptophan to niacin is inversely related to liver PAC activity.
160
,130 2
?? g 100
-
Weight gain in response to 0.06% L-tryptophan
*J _____________
: m
70
40
Niacin-equivalent of 0.06% L-tryptophan
! f
0
3
Niacin
6
9
1
Added (ppm)
FIGURE 1 The linear regression of body weight gain (Y) on dietary level of niacin supplementation (X) from In this example, a dietary mule ducklings. supplement of 0.06% tryptophaa (.24% total dietary tryptophan (Table3)) is equivalent to a dietary supplement of 3.66 mg/kg of niacin.
(ma/kc) 0 3 6 9
76.8 74.1 64.6 69.8 la.5 18.8 18.8 17.1
16.5 19.1 19.1
16.3 19.6 18.7 16.5
17.1 10.2 17.7
PACI"
4.6 4.1 3.8 4.5
4.8 4.0 4.1
9.0 7.9 7.4 9.0
9.0 8.0 0.2
Ratio'
69.3 77.5 74.0 75.6
68.0 03.0 71.3
89 96 96 94
103 90 89
3BAAo
4.6 6.5 5.1 4.8
4.3 5.8 5.7
Kidney 16.5 15.2 14.0 15.3 13.9 15.8 15.8
6.5 9.0 9.4 0.8
0.0 a.2 9.0
Liver 13.6 11.3 11.3 14.5 11.3 11.4 11.0
Ratio
PAC
Mule ducklings
18.9 20.4 24.4 20.1
20.8 21.5 20.2
04 91 92 90
a7 aa 92
3BAAo
9.7.' 10.2* 11.7* 12.5b
10.5 11.0 11.4
3.9b 4.2& 4.6* 5.1'
4.9" 4.6& 3.ab
PAC
2.0 2.1 2.1 1.7
2.0 2.1 1.0
21.7* 23.4' 20.7b 18.5b
10.7b 19.9b 24.9.
Ratio
Broiler chicks
'Abbreviations: 3IiAAo: 3-hydroxyanthranilic acid oxygenase; PAC: picolinic acid carboxylase; Ratio: 3BAAO/PAC. pmole of 2-amino-3-carboxymuconic-6-semialdehyde per hour per gram of 'Enzyme activities: wet liver or kidney. 3Means for tryptophan or niacin treatment in the same column within liver or kidney having no superscripts are not significantly different (P>.O5). 'Means for tryptophan or niacin treatments in the same column within liver or kidney that do not have a common letter in their superscripts are significantly different (P<.O5).
Niacin
73.53 70.3 71.1
136 143 132 137
Niacin (rno/ks) 0 3 6 9
TvrptoPhan 0.16 0.18 0.20
14s3 137 134
(%I
Trwtouhan 0.16 0.18 0.20
3BAAo=,=
Pekin ducklings
Main Effects of Tryptophan and Niacin on the Liver Enzyme Activities of Pekin Ducklings, Mule Ducklings and Broiler Chicks
TABLE 6
TRYPTOPHAN-NIACIN
CONVERSION
101
The efficiency of the conversion of tryptophan to niacin in mammals is influenced by dietary tryptophan and niacin levels. Badawy and Evans (25) found that kynurenine production in the rat was increased by lowering the intake of nicotinamide. This suggests that the oxidation of tryptophan to kynurenine may be more active in niacin-deficient animals. An increase in dietary tryptophan has been reported also to enhance this pathway and apparently increase NAD biosynthesis from tryptophan (24). The latter investigators observed that the NAD content of rat liver increased 1.5 to 3.0 fold as dietary tryptophan level increased from 0% to 0.39%. Therefore, when niacin-deficient diets are adequate in tryptophan, the rate of conversion of tryptophan to niacin would be expected to be higher than when tryptophan is deficient. Dietary influence on tryptophan-niacin conversion also may be reflected in liver PAC activity and the ratio of 3-BAAO:PAC. In this study, there was decreased PAC activity and an increase in the ratio of 3-IiAAO:PAC in broiler chicks (P c 0.05) when dietary A similar tryptophan increased from 0.16% to 0.20% (Table 6). trend in 3-HAAO:PAC ratio was observed in the study of DiLorenzo (9) when Leghorn chicks received a semipurified diet lacking supplemental niacin. These results suggest that more niacin was synthesized from tryptophan when more dietary tryptophan became available. There was also an increase in PAC activity and a decrease in the 3-BAAO:PAC ratio in liver when the dietary niacin supplement exceeded 3 mg/kg. This may indicate a decrease in the synthesis of NAD from tryptophan when dietary niacin levels are Cho-Chung and Pitot that dietary adequate. found (26,271 nicotinamide resulted in end-product inhibition of tryptophan pyrrolase (tryptophan 2,3-dioxygenase, EC 1.13.11.11). Thus when dietary niacin is adequate, both tryptophan pyrrolase and PAC may be regulated to decrease NAD synthesis from tryptophan in chicks. On the other hand, there were no significant changes in liver 3BAA0 and PAC activities or 3-BAAO:PAC ratios in Pekin ducklings and mule ducklings when dietary tryptophan and niacin levels were changed. This may also be a further indication that the tryptophan-niacin pathway is relatively inactive in ducks. Since tryptophan pyrrolase is found only in the liver of animals, it is believed that liver is the major organ for niacin biosynthesis from tryptophan (28,291. However, other enzymes of the tryptophan-NAD pathway also in kidney are found (30). Tryptophan, furthermore, may be oxidized by a widely distributed enzyme, indoleamine 2,3-dioxygenase (31) andtryptophanmetabolites from liver and other tissues may be transported in the blood to kidney (16). Both ducklings and chicks had relatively high PAC and low 3-BAA0 activities in their kidneys. Therefore, the 3-BAAO:PAC ratio in kidney is much lower than that of liver, which suggests that the conversion of tryptophan metabolites to niacin is less active in avian kidney than in liver. However, as in liver, there was a significant increase in PAC activity in kidney when dietary niacin increased. A similar response also was observed by Penz et al. (23). This could be an indication that the kidney has a role in niacin synthesis.
B.-J. CHEN etal.
102
TABLE 7 Summary of the Efficiency of Conversion of Tryptophan to Niacin in Pekin Ducklings, Mule Ducklings, and Broiler Chicks Conversion Efficiency (mg of tryptophan equivalent to 1 mg of niacin) Tryptophan (%I
Pekin ducklings
Mule ducklings
Broiler chicks*
0.16 0.18 0.20
187 175 107
181 164 103
47 47 41
*Others have reported similar estimates: DiLorenzo (91, 43 to 63; Baker et al. (81, 45; and Oduho and Baker (lo), 52; and Oduho et al (111, 42 mg of tryptophan to equivalent of 1 mg of niacin. From the growth studies and liver enzyme activities in ducklings and chicks, it is apparent that chicks can use tryptophan as a niacin precursor to support normal growth and prevent niacin deficiency symptoms. If the data from the .16% and .18% dietary tryptophan levels are used in order to provide conservative estimates, chicks have a conversion efficiency of 47 mg tryptophan equivalent to 1 mg niacin. The conversion efficiency of Pekin and mule ducklings averaged 177 mg of tryptophan equivalent to 1 mg niacin. On a molar basis, this represents about 1% of tryptophan converted to niacin in ducks and about 3.5% converted in chicks. Only under conditions in which very high dietary levels of tryptophan are present, can ducks use tryptophan as a significant source of niacin. REFERENCES 1.
Briggs GM. Influence of gelatin and tryptophane on nicotinic acid requirement of chicks. J Biol Chem 1945;161:749-50.
2.
Bernard R, Demers JM. Inter-relationship de l'acide nicotinique et du tryptophane chez le caneton (p8kin blanc). Rev Can Biol 1949;8:504-08.
3.
Niacin and tryptophan requirements Wu L-S, Wu C-L, Shen T-F. Poult Sci of mule ducklings fed corn and soy-based diets. 1984; 63:153-58.
4.
Fisher Ii, Scott HM, Johnson BC. Quantitative aspects of the nicotinic acid-tryptophan interrelationship in the chick. Brit J Nutr 1955;9:340-49.
5.
Patterson EB, Hunt JR, Vohra P, Blaylock niacin and tryptophan requirements of 1956;35:499-504.
LG, McGinnis J. Poult chicks.
The Sci
TRYPTOPHAN-NIACINCONVERSION
103
6.
Childs GR, Carrick CW, Hauge SM. The niacin young chickens. Poult Sci 1952;31:551-58.
7.
Oh SY, Summers JD, Wood AS. Performance of chicks fed graded levels of niacin and tryptophan. Can J Anim Sci 1972;52:74550.
8.
Baker DH, Allen NK, Kleiss AJ. Efficiency of tryptophan as a niacin precursor in the young chick. J Anim Sci 1973;36:299302.
9.
DiLorenzo RN. Studies of the genetic variation in tryptophannicotinic acid conversion in chicks. Ph.D. thesis. Cornell University. 1972.
10.
Quantitative efficacy of niacin sources Oduho GW, Baker DE. nicotinic acid, nicotinamide, NAD and tryptophan. for chicks: J Nutr 1993:123:2201-06.
11.
Oduho GW, Han Y, Baker efficacy of tryptophan 1994;124:444-50.
12.
Nutrient requirements of ducks. Dean WF. Cornell Nutrition Conference, Syracuse, BY.
13.
National National
14.
Ruiz N, Harms RH. Comparison of the biopotencies of nicotinic Brit Poult Sci acid and nicotinamide for broiler chicks. 1988$29:491-98.
15.
Niacin requirement of broiler Ruiz N, Harms RH, Linda SB. chickens fed a corn-soybean meal diet from 1 to 21 days of age. Poult Sci 1990;69:433-39.
16.
Ikeda M, Tsuji Studies 0. dinucleotide. biosynthesis tryptophan in
17.
Henderson LY, Swan PB. Methods in Enzymology. Academic Wright LD eds.
18.
Association of Official Analytical Chemists. Official of Analysis. 12th ed. Arlington, VA. 1980:743-46.
19.
Wehler AH, McDaniel EG, Bundley JbX. Changes in the enzymatic I. Increase of picolinic carboxylase in composition of liver. J Biol Chem 1958;232:323-30. diabetes.
DE. as a
requirement
of
Iron deficiency reduces the niacin precursor. J Nutr In: Proceedings, 1978:132-40.
Nutrient requirements of poultry. Research Council. Academy of Sciences, Washington, DC. 1994.
H,Nakamura S, Ichiyama A, Nishizuka Y, Hayaishi on the biosynthesis of nicotinamide adenine carboxylase in the II. A role of picolinic nicotinamide from of adenine dinucleotide J Biol Chem 1965;240:1395-1401. mammals. Picolinic Vol XVIII, Press, NY.
acid carboxylase. Part B. McCormick 1971:175-80.
In: DB,
Methods
B.-J. CHEN etal.
104 20.
Nishizuka Y, Ichiyama A, Hayaishi 0. Metabolism of the benzene ring of tryptophan (mammals). In: Methods in Enzymology Vol Academic Press, NY. XVII, Part A. 1970:460-505.
21.
Duncan DB. Multiple 1955;11:1-42.
22.
Snedecor GW, Cochran WG. State Univ. Press, Ames,
23.
Penz AM Jr, Clifford AJ, Rogers QR, Kratzer PH. dietary leucine to influence the tryptophan-niacin the chicken. J Nutr 1984;114:33-41.
24.
Hayakawa T, Iwai SC. Effect of tryptophan and/or casein supplementation on NAD levels in livers of the rats fed on niacinand protein-free diet. J Nutr Sci Vitamin01 1984;30:303-06.
25.
Badawy AA-B, Evans W. The regulation of rat liver tryptophan pyrrolase activitybyreducednicotinamide-adenine dinucleotide (phosphate): experiments with glucose and nicotinamide. Biochem J 1976;156:381-90.
26.
Cho-Chung YS, Pitot EC. Feedback control of rat liver tryptophan pyrrolase. I. End product inhibition of tryptophan pyrrolase activity. J Biol Chem 1967;242:1192-98.
27.
Cho-Chung YS, Pitot HC. Regulatory effects of nicotinamide on tryptophan pyrrolase synthesis in rat liver in vivo. Europ J Biochem 1968;3:401-06.
28.
Knox WE, Mehler AH. The conversion of tryptophan to kynurenine in liver. I. The coupled tryptophan peroxidase-oxidase system forming formylkynurenine. J Biol Chem 1950;187:419-30.
29.
Mehler AH, Knox, WE. The conversion of tryptophan kynurenine in liver. hydrolysis II. The enzymatic formylkynurenine. J Biol Chem 1950;187:431-38.
30.
Lan SJ, Gholson RK. A comparative study catabolism. J Biol Chem 1965;240:3934-37.
31.
Knowles RG, Clarkson NA, Pogson CI, Salter M, Duch DS, Edelstein MP. The role of tryptophan and kynurenine transport in the catabolism of tryptophan through indoleamine 2,3Kynurenine and Serotonin Pathways, eds. dioxygenase. Press, NY. RR, Plenum Schwartz R, Y:;, SN, and Brown 21991;161-66.
Accepted
for
publication
June
range
16,
and multiple
F tests.
Biometrics
Statistical Methods. 7th ed., Iowa IA. 1980:169-71, 233-36, 289-330.
1995.
of
Failure pathway
of in
to of
tryptophan
0271-5317/96$15.00+.00 ELSEVIER
EFFICImCY
0271-5317(95)02063-2
OF TFtYPTOPEAN-NIACIN CONVRRSION AND DUCRS1
IN CBICRRNS
Bao-Ji Chen PhD'; Tian-Fuh Shen PhD'; Richard E. Austic PhD' 'Duck Research Center, Taiwan Livestock Research Institute, I-Lan, Taiwan, ROC 3Department of Animal Science, National Taiwan University Taipei, Taiwan, ROC 'Department of Poultry and Avian Sciences, Cornell University Ithaca, NY 14853
Experiments were conducted with Pekin ducklings, mule ducklings and broiler chicks to determine the efficiency of conversion of tryptophan to niacin. When were fed a diet marginal in tryptophan and chicks deficient in niacin, either tryptophan or niacin supplementation improved growth and prevented niacin deficiency symptoms. However, only niacin improved growth and prevented symptoms in Pekin or mule ducklings. Liver picolinic acid carboxylase (PAC) activity was 4 to 5 times higher in ducklings than in chicks. The activity the ratio of 3-hydroxyanthranilic acid of PAC and oxygenase (3-BAA01 activity to PAC activity in liver were significantly influenced by tryptophan or niacin in the diet in chicks but not in ducks. The efficiency of conversion of tryptophan to niacin was calculated from the relative responses in weight gains when graded levels of tryptophan or niacin were added to the diet. The results indicate that 181 mg, 172 mg and 47 mg of tryptophan are equivalent to 1 mg of niacin in Pekin ducklings, mule ducklings and broiler chicks, respectively. The duckling has a limited ability to use tryptophan to spare niacin. KEY WORDS:
Tryptophan-Niacin, Conversion Efficiency, Picolinic Carboxylase, Chickens, Ducks INTRODUCTION
It has been known for many years that tryptophan can counteract growth retardation in chicks (1) and ducks (2,3) that 'Supported by the Council of Agriculture,Taiwan, ROC. 'Current address: Department of Animal Science, National Taiwan University, Taipei, Taiwan, ROC. 'Current address: Department of Animal Science, 248 Morrison Hall, Cornell University, Ithaca, NY 14853. Telephone: 607-255-8497; Fax: 607-255-9829; email: [email protected].
91
92
B.-J. CHEN etal.
are fed diets limiting in niacin. Early studies on the extent to which tryptophan can substitute for niacin in chicks provided conflicting results (4,5,6,7). The quantitative conversion of tryptophan to niacin in chicks was first reported by Baker et al. (8) who indicated that 45 mg of dietary tryptophan is equivalent to 1 mg of niacin. Other investigations have provided similar estimates (9,10,11). The niacin requirement of mule ducks5 (3) and Pekin ducks (12,13) was reported to be 45 mg/kg and 55 mg/kg, respectively. This is nearly twice the requirement of Leghorn or broiler chicks (27 to 35 mg/kg; 13,14,15). The difference in requirement seems to be related to the efficiency of biosynthesis of NAD from tryptophan The efficiency is controlled, at least in part, by liver (9). picolinic acid carboxylase (PAC) activity (16). Picolinic acid carboxylase (aminocarboxymuconate-semialdehyde decarboxylase, EC of 2-amino-3catalyzes decarboxylation 4.1.1.451, the carboxymuconic-6-semialdehyde, an unstable intermediate formed by action of 3-hydroxyanthranilic acid oxygenase the (3hydroxyanthranilate 3,4-dioxygenase, EC 1.13.11.6) (3-BAA01 on 3hydroxyanthranilic acid. PAC diverts 2-amino-3-carboxymuconic-6semialdehyde toward the formation of CO, rather than toward the formation of quinolinic acid, an intermediate in the synthesis of Henderson and Swan (17) proposed the use of liver 3-IiAAO:PAC NAD. ratio to predict the efficiency with which dietary tryptophan serves as a source of dietary niacin - a lower ratio indicating less efficient conversion of tryptophan to niacin. Pekin ducks appear to have the highest liver PAC in poultry about 4 to 5 fold higher than that of chicks (9). species, However, the efficiency of conversion of tryptophan to niacin in The purpose of this work was to ducks has never been reported. investigate the difference in the efficiency of conversion of tryptophan to niacin in chicks and ducks, and to establish the quantitative efficiency for the conversion in ducks. MATERIALS
AND METHODS
Day-old broiler chickens (Arbor Acres Farm, Taiwan), Pekin ducklings (Duck ducklings (Cherry-Valley, Taiwan), and mule Research Center, Taiwan) were weighed, and assigned at random to experimental groups of eight birds each containing equal numbers of females and males. They were raised in electrically heated Birds were kept at brooders with wire floors (60 X 90 cm). temperatures of 32 and 28 (i 2 C) during the first week and second Water and feed were provided ad libitum. week, respectively. Three hundred and twelve birds of each kind were divided into triplicate groups of eight birds each in a factorial arrangement of 12 treatments with 3 levels of L-tryptophan (0, 0.02, and 0.04%) and 4 levels of niacin (0, 3, 6, and 9 mg/kg) added to the basal diet containing 0.16% tryptophan and 24.5 mg/kg niacin (Table 11, and one additional treatment of 0.08% L-tryptophan supplementation All amino acids for the diets were purchased from Ajinomoto only.
TRYPTOPHAN-NIACIN
CONVERSION
93
Company, Inc. (Tokyo, Japan) and niacin (crystalline nicotinic acid) was obtained from Merck & Co., Inc., Rahway, NJ. The crude protein (N X 6.251, moisture and niacin contents of the basal diet were determined according to the methods of the Association of Official Analytical Chemists (18). Body weights were determined prior to experiment, and at the end of the experiment after feed had been withheld for at least 2 hours. The number of birds showing niacin deficiency symptoms such as inflammation of the tongue and mouth and enlargement of the tibiotarsal joint in chicks, and bowed legs or hock enlargement in ducks was recorded. Six Birds were re-fed for 2 hours after the final weighing. birds from each treatment (2 per replicate) were killed by cervical dislocation. The livers and kidneys were removed, immediately frozen in liquid nitrogen and then analyzed for 3-BAA0 and PAC in duplicate with activities. Enzyme assays were conducted substrate blanks according to the spectrophotometric method of Mehler et al. (19) and using 4.5 X 10' as the molar extinction 2-amino-3-carboxymuconic-6-semialdehyde in the coefficient of calculation of enzyme activity (Nishizuka, et al., 20). feed efficiency (body weight Data on body weight gain, were subjected to gain/feed intake), 3-BAA0 and PAC activities (21) new multiple range test analysis of variance and Duncan's SAS program (Statistical Analysis System, using a computer Snedecor and Cochran's linear calibration formula and Institute). the the method of inverse prediction was used for evaluating efficiency of conversion of tryptophan to niacin (22).
RESULTS The effects of tryptophan and niacin on gross measures in Pekin ducklings is shown in Table 2. Ducklings fed the basal diet had lower body weight gain and higher incidence of deficiency symptoms than ducklings that received diets containing supplemental niacin. Increases in niacin level resulted in significant increases in body weight gain and feed efficiency (P c .05). feed efficiency was influenced by However, growth and not The incidence of deficiency symptoms supplemental tryptophan. to niacin, decreased in response but was not affected by Yortality was noted only at the lower niacin levels tryptophaa. and was prevented by niacin and the highest level of tryptophan. The responses of mule ducklings to tryptophan and niacin were similar to those of Pekin ducklings (Table 3).
'Sterile hybrids that were resulting from the mating
produced by crossing Muscovy drakes of Pekin drakes and Tsaiya ducks.
with
the P, female
94
B.-J. CHEN et al.
TABLE 1 Composition Composition
%
Corn, yellow Soybean meal (44% protein) Gelatin Cellulose' Soybean oil Amino acids' NaHCO, Choline-Cl (50%) Dicalcium phosphate Limestone, pulverized Salt, iodized Vitamin premix' Mineral premix4 Crude protein (%) Metabolizable energy Tryptophan (%I Niacin (mg/kg)
of the Basal Diet
(Kcal/Kg)
64.00 15.50 7.00 3.50 3.50 2.00 0.20 0.10 2.40 1.00 0.30 0.30 0.20 21.6 2970 0.16 24.5
'Solka Floe, Brown Co., Berlin, NH. 'Provided as % of diet: L-lysine.HCl, 0.38; DL-methionine, 0.43; L-arginine, 0.18; L-isoleucine, 0.13; L-threonine, 0.20; L-valine, 0.05; L-tyrosine, 0.15; L-glutamic acid, 0.48. 'Provided in IU per Kg diet: vitamin A, 6000; vitamin Do, 1000; vitamin E, 15; and in mg per Kg of diet: vitamin K, 2.0; thiaminHC1, 2.0; riboflavin, 5.0; Ca-pantothenate, 15.0; . * B,,; pyridoxineHC1 6.0; folic acid, 0.5; biotin, 0.15; vitamin 0.02; ethoxyquin, 100. 'Provided in mg per Kg diet: MnSO;H,O, 165; ZnO, 100; CuSO,'SH,O, 50; FeS0,'7H,O, 200; Na,SeO,, 0.22 increased weight gain and feed Niacin supplementation efficiency and decreased symptoms of niacin deficiency in chicks In contrast to the results with (Table 41, as in ducklings. alone increased body weight ducklings, tryptophan supplementation gain, feed efficiency, and decreased niacin deficiency symptoms. the deficiency When the dietary tryptophan level was 0.24%, The differences between were completely prevented. symptoms ducklings and chicks are readily apparent in the main effects of treatments (Table 5). The activity of liver PAC in chicks was approximately 30% that of ducklings and the ratio of 3-HAAO:PAC in chicks was twice as Both measures in ducklings were high as in ducklings (Table 6). unaffected by dietary tryptophan or niacin concentration. In chicks, however, PAC was decreased by tryptophan and increased by niacin (P c .05), and the ratio of 3-HAAO:PAC activities increased in response to tryptophan and decreased in response to niacin (P c .05).
TRYPTOPHAN-NIACIN
CONVERSION
95
TABLE 2 Effects of Tryptophan and Niacin on Growth, Feed Efficiency, Niacin Deficiency Symptoms and Mortality of Pekin Ducklings Dietary L-Trp
Niacin added
Body wt. gain
Feed efficiency
Incidence of niacin deficiency'
Mortality
%
mg/kg
g
gain/feed
%
%
0.16 0.18 0.20 0.24
0 0 0 0
65 81 67 108
06 86 86 28
a 8 4 0
0.16 0.18 0.20
3 3 3
91 f 12' 88 f 32' 100 f 29*
.31 f .03*= .30 f .04* .31 f .02*=
75 86 63
0 8 0
0.16 0.18 0.20
6 6 6
119 * 31*= 131 f 46*O 117 f 46*"
.37 f .03b"d .32 f .08*' .35 f .08*cd
29 21 41
0 0 0
0.16 0.18 0.20
9 9 9
167 f 3gb" 182 f 55" 107 f 63"
.46 f .02' .43 f .03d. .40 f .03**
25 8 0
0 0 0
f 16" f 7' f 20' f 27*
.26 -28 .28 .30
f f f f
.04* .02* .08* .oa*
'Percent of birds showing niacin deficiency symptoms. 'Mean f standard deviation. Means in the same column that do not have a common letter in their superscripts are significantly different (Pc.05).
The 3-HAAO activities of kidney were approximately SO%, 80% and 25%, respectively, of liver activities in Pekin ducklings, mule ducklings and broiler chicks, respectively (Table 6). The PAC activities of kidney and liver were similar in ducklings, but the PAC activity of kidney in chicks was 2.5-fold higher than that of The ratio of 3-FfAAO:PAC activities in duck kidney was liver. approximately one-half that of duck liver whereas the ratio in chick kidney was one-tenth that of chick liver. The activities of 3-HAAO and PAC in duck kidney were unaffected by dietary tryptophan and niacin concentrations. The activities in chick kidney were unaffected by tryptophan, but PAC activity was significantly increased by dietary niacin.
B.-J. CHEN et al.
96
TABLE 3 Effect of Tryptophan and Niacin on Growth, Peed Efficiency, Niacin Deficiency Symptoms and Mortality of Mule Ducklings Dietary L-Trp
Niacin added
Body wt. gain
Peed efficiency
Incidence of niacin deficiency'
Mortality
%
mg/kg
g
gain/feed
%
%
0.16 0.18 0.20 0.24
0 0 0 0
49 51 40 86
55 SO 61 23
a 0 4 0
0.16 0.18 0.20
3 3 3
67 f a*= 79 f 26*= 85 f 24bcd
.2s f .03bC .27 f .06bcd .29 f .05b=d
30 33 50
0 0 0
0.16 0.18 0.20
6 6 6
108 f g&i 106 f 20Cd* 98 f 22cd'
.31 f .03Ed' .29 f .03b"d .30 f .05fd'
25 21 25
0 0 0
0.16 0.18 0.20
9 9 9
123 * 26'*' 141 f 38" 149 f 33=
.30 f .03.= .35 f .o7d** .41 f .06'
0 0 4
0 0 4
f 0*b' f 19* f 11' f 23bcd
.20 .22 .16 .32
f f f f
.06& .05*= .03' .05-
'.'Refer to Table 2.
DISCUSSION The tryptophan level used in this experiment (0.16% to 0.20%) was marginal for both ducklings and chicks (13). The same dietary tryptophan level also was used by Baker et al. (8); Oduho and Baker (10); and Penz et al. (23) and a slightly lower level (.14%) was used by Oduho and Baker (10). The niacin content of the basal diet was 24.5 mg/kg, which is below the requirements for both chicks and ducklings (13). Thus, the experimental diet contained a tryptophan level marginally adequate for growth but was limiting in niacin. This is an appropriate condition for evaluating the efficiency of It is noteworthy that chicks conversion of tryptophan to niacin. This responded to dietary niacin supplementation up to 9 mg/kg. suggests that the bioavailable niacin concentration in the diet was This could explain considerably less than the analyzed content. the observed linear responses for growth of chicks to both tryptophan and niacin over the full range of the nutrients used in these studies.
TRYPTOPHAN-NIACIN
CONVERSION
97
TABLE 4 Effect of Tryptophan and Niacin on Growth, Feed Efficiency, Deficiency Symptoms and Mortality of Broiler Chicks Dietary L-Trp %
Niacin
Niacin added
Body wt. gain
Feed efficiency
Incidence of niacin deficiencv'
mdkg
B
gain/feed
%
%
.02* .04* .03"6' .04g
71 71 46 0
0 0
4 0
.45 f .03b' .48 f .06bC .59 f .o26'f
62 47 25
4 0 4 4 0 0
0.16 0.18 0.20 0.24
0 0 0 0
41 55 86 203
0.16 0.18 0.20
3 3 3
61 * 73 f 111 f
0.16 0.18 0.20
6 6 6
97 * 144" 120 f 16'O 150 f 1P
.51 f .00Od :61 62 f .08'
26 17 10
0.16 0.18 0.20
9 9 9
127 f 24gh 162 f 19' 200 + 23'
1.61 f .02' .65 f .03' .68 f .02fP
13 0 0
f 3.' f 3& gCd. f f 18' 5*= 7&d 8'm
.35 .42 .52 .73
f f f f
Mortality
0
8
"'Refer to Table 2.
Ducklings were not able to use tryptophan effectively to replace niacin under the conditions of this study. On the other hand, broiler chicks exhibited significant improvement in growth and feed utilization as well as reduced incidence of deficiency symptoms in response to dietary tryptophan or niacin. These results are in agreement with those of Fisher et al. (4) and Patterson et al. (5) which indicated that tryptophan could completely replace niacin in chick diets. It has been reported that ducks also have the ability to use tryptophan to spare niacin This effect was observed only in diets with very high (2,3). tryptophan levels (i.e., 0.60% tryptophan in the studies of Bernard and Deters (2); 0.33% tryptophan in the work of Wu et al. (3). It might be concluded that although the conversion of tryptophan to niacin is possible in ducks, it is very inefficient under normal dietary conditions.
98
B.-J. CHEN et al.
TABLE 5 The Main Effects of Tryptophan and Niacin on Body Weight Gain, Feed Efficiency and Niacin Deficiency Symptoms of Pekin Ducklings, Mule Ducklings and Broiler Chicks Pekin TrD
BWG=
(%I
9
0.16 0.18 0.20
111" 121' 118'
Niacin 0 3 6 9
ducklings FE1
0.35' 0.33' 0.33'
Mule
ducklings FE
Broiler
ID
BWF
%
g *
chicks
ID'
BWG
FE
ID
%
9
53 48 49
87' 94' 94‘
0.29' 0.28. 0.29.
31 25 35
1S 137'
0.48' 0.54b 0.60"
58 46 26
87 72 30 14
48' 77b 104" 1386
0.20. 0.27b 0.30b 0.38"
55 40 16 4
61' 81b 122" 163'
0.43' 0.51b 0.58" 0.65'
84 62 23 5
%
(ma/ku) 72' 93* 122b 179=
0.27' 0.31* 0.34b 0.43=
'Abbreviation: BWG: body weight gain; FE: feed efficiency (gain/intake). 'ID: % of birds showing niacin deficiency symptoms. 'Means for tryptophan or niacin treatments in the same column not having a conanon letter in their superscripts are significantly different (P<.O5). A comparison of the efficiency of conversion of tryptophan to niacin in chicks and ducklings was evaluated using the body weight gains from the 0.16%, 0.18% and 0.20% tryptophan groups. Linear calibration equations, based on the level of niacin supplementation (Y) of Pekin ducklings, (X1 and the body weight gains mule ducklings and broiler chicks, were calculated. The body weight gains of the birds that received 0.24% tryptophan and no niacin were compared to the reference response to predict the efficiency of conversion of tryptophan to niacin (Figure 1). Examples of the calculation using the 0.18% tryptophan groups are shown below: Pekin ducklings: Y = 68.45 + 11.57 X r = 0.960 0.06% Trp had the same effect as 3.42 mg/kg niacin. Therefore 175 mg Trp = 1 mg niacin. r = 0.998 Mule ducklings: Y = 49.62 + 9.92 X 0.06% Trp had the same effect as 3.66 mg/kg niacin. Therefore 164 mg Trp = 1 mg niacin (Figure 1). Broiler
chicks: Y - 47.37 + 12.27 X r = 0.986 had the same effect as 12.66 mg/kg niacin. Therefore 47 mg/kg Trp = 1 mg niacin. 0.06%
Trp
The conversion efficiency observed in chicks is similar to the efficiency reported by DiLorenzo (9); Baker et al. (8); Oduho and
TRYPTOPHAN-NIACIN
CONVERSION
99
The efficiency Baker (10); and Oduho et al. (11) (Table 7). This increase appeared to increase in the 0.20% tqptophan group. is consistent with the 3-EAAO:PAC ratio (Table 6) and could be expected on the basis of studies of the rat (24). However, the estimate of the conversion efficiency for the .20% tryptophan group may be less reliable because of the relatively small increment of dietary tryptophan (0.04%) used in the calculation versus the increments (0.08% and 0.06%, respectively) used for the calculation of efficiency in the 0.16% and 0.18% tryptophan groups. Ducklings had relatively high PAC activities and high ratios of 3-HAAO:PAC activity in liver and kidney as compared to chicks. This may be the reason for the different abilities of ducks and The results are in chicks to use tryptophan to replace niacin. agreement with the reports of Ikeda et al. (16) and DiLorenzo (9) indicating that the efficiency of conversion of tryptophan to niacin is inversely related to liver PAC activity.
160
,130 2
?? g 100
-
Weight gain in response to 0.06% L-tryptophan
*J _____________
: m
70
40
Niacin-equivalent of 0.06% L-tryptophan
! f
0
3
Niacin
6
9
1
Added (ppm)
FIGURE 1 The linear regression of body weight gain (Y) on dietary level of niacin supplementation (X) from In this example, a dietary mule ducklings. supplement of 0.06% tryptophaa (.24% total dietary tryptophan (Table3)) is equivalent to a dietary supplement of 3.66 mg/kg of niacin.
(ma/kc) 0 3 6 9
76.8 74.1 64.6 69.8 la.5 18.8 18.8 17.1
16.5 19.1 19.1
16.3 19.6 18.7 16.5
17.1 10.2 17.7
PACI"
4.6 4.1 3.8 4.5
4.8 4.0 4.1
9.0 7.9 7.4 9.0
9.0 8.0 0.2
Ratio'
69.3 77.5 74.0 75.6
68.0 03.0 71.3
89 96 96 94
103 90 89
3BAAo
4.6 6.5 5.1 4.8
4.3 5.8 5.7
Kidney 16.5 15.2 14.0 15.3 13.9 15.8 15.8
6.5 9.0 9.4 0.8
0.0 a.2 9.0
Liver 13.6 11.3 11.3 14.5 11.3 11.4 11.0
Ratio
PAC
Mule ducklings
18.9 20.4 24.4 20.1
20.8 21.5 20.2
04 91 92 90
a7 aa 92
3BAAo
9.7.' 10.2* 11.7* 12.5b
10.5 11.0 11.4
3.9b 4.2& 4.6* 5.1'
4.9" 4.6& 3.ab
PAC
2.0 2.1 2.1 1.7
2.0 2.1 1.0
21.7* 23.4' 20.7b 18.5b
10.7b 19.9b 24.9.
Ratio
Broiler chicks
'Abbreviations: 3IiAAo: 3-hydroxyanthranilic acid oxygenase; PAC: picolinic acid carboxylase; Ratio: 3BAAO/PAC. pmole of 2-amino-3-carboxymuconic-6-semialdehyde per hour per gram of 'Enzyme activities: wet liver or kidney. 3Means for tryptophan or niacin treatment in the same column within liver or kidney having no superscripts are not significantly different (P>.O5). 'Means for tryptophan or niacin treatments in the same column within liver or kidney that do not have a common letter in their superscripts are significantly different (P<.O5).
Niacin
73.53 70.3 71.1
136 143 132 137
Niacin (rno/ks) 0 3 6 9
TvrptoPhan 0.16 0.18 0.20
14s3 137 134
(%I
Trwtouhan 0.16 0.18 0.20
3BAAo=,=
Pekin ducklings
Main Effects of Tryptophan and Niacin on the Liver Enzyme Activities of Pekin Ducklings, Mule Ducklings and Broiler Chicks
TABLE 6
TRYPTOPHAN-NIACIN
CONVERSION
101
The efficiency of the conversion of tryptophan to niacin in mammals is influenced by dietary tryptophan and niacin levels. Badawy and Evans (25) found that kynurenine production in the rat was increased by lowering the intake of nicotinamide. This suggests that the oxidation of tryptophan to kynurenine may be more active in niacin-deficient animals. An increase in dietary tryptophan has been reported also to enhance this pathway and apparently increase NAD biosynthesis from tryptophan (24). The latter investigators observed that the NAD content of rat liver increased 1.5 to 3.0 fold as dietary tryptophan level increased from 0% to 0.39%. Therefore, when niacin-deficient diets are adequate in tryptophan, the rate of conversion of tryptophan to niacin would be expected to be higher than when tryptophan is deficient. Dietary influence on tryptophan-niacin conversion also may be reflected in liver PAC activity and the ratio of 3-BAAO:PAC. In this study, there was decreased PAC activity and an increase in the ratio of 3-IiAAO:PAC in broiler chicks (P c 0.05) when dietary A similar tryptophan increased from 0.16% to 0.20% (Table 6). trend in 3-HAAO:PAC ratio was observed in the study of DiLorenzo (9) when Leghorn chicks received a semipurified diet lacking supplemental niacin. These results suggest that more niacin was synthesized from tryptophan when more dietary tryptophan became available. There was also an increase in PAC activity and a decrease in the 3-BAAO:PAC ratio in liver when the dietary niacin supplement exceeded 3 mg/kg. This may indicate a decrease in the synthesis of NAD from tryptophan when dietary niacin levels are Cho-Chung and Pitot that dietary adequate. found (26,271 nicotinamide resulted in end-product inhibition of tryptophan pyrrolase (tryptophan 2,3-dioxygenase, EC 1.13.11.11). Thus when dietary niacin is adequate, both tryptophan pyrrolase and PAC may be regulated to decrease NAD synthesis from tryptophan in chicks. On the other hand, there were no significant changes in liver 3BAA0 and PAC activities or 3-BAAO:PAC ratios in Pekin ducklings and mule ducklings when dietary tryptophan and niacin levels were changed. This may also be a further indication that the tryptophan-niacin pathway is relatively inactive in ducks. Since tryptophan pyrrolase is found only in the liver of animals, it is believed that liver is the major organ for niacin biosynthesis from tryptophan (28,291. However, other enzymes of the tryptophan-NAD pathway also in kidney are found (30). Tryptophan, furthermore, may be oxidized by a widely distributed enzyme, indoleamine 2,3-dioxygenase (31) andtryptophanmetabolites from liver and other tissues may be transported in the blood to kidney (16). Both ducklings and chicks had relatively high PAC and low 3-BAA0 activities in their kidneys. Therefore, the 3-BAAO:PAC ratio in kidney is much lower than that of liver, which suggests that the conversion of tryptophan metabolites to niacin is less active in avian kidney than in liver. However, as in liver, there was a significant increase in PAC activity in kidney when dietary niacin increased. A similar response also was observed by Penz et al. (23). This could be an indication that the kidney has a role in niacin synthesis.
B.-J. CHEN etal.
102
TABLE 7 Summary of the Efficiency of Conversion of Tryptophan to Niacin in Pekin Ducklings, Mule Ducklings, and Broiler Chicks Conversion Efficiency (mg of tryptophan equivalent to 1 mg of niacin) Tryptophan (%I
Pekin ducklings
Mule ducklings
Broiler chicks*
0.16 0.18 0.20
187 175 107
181 164 103
47 47 41
*Others have reported similar estimates: DiLorenzo (91, 43 to 63; Baker et al. (81, 45; and Oduho and Baker (lo), 52; and Oduho et al (111, 42 mg of tryptophan to equivalent of 1 mg of niacin. From the growth studies and liver enzyme activities in ducklings and chicks, it is apparent that chicks can use tryptophan as a niacin precursor to support normal growth and prevent niacin deficiency symptoms. If the data from the .16% and .18% dietary tryptophan levels are used in order to provide conservative estimates, chicks have a conversion efficiency of 47 mg tryptophan equivalent to 1 mg niacin. The conversion efficiency of Pekin and mule ducklings averaged 177 mg of tryptophan equivalent to 1 mg niacin. On a molar basis, this represents about 1% of tryptophan converted to niacin in ducks and about 3.5% converted in chicks. Only under conditions in which very high dietary levels of tryptophan are present, can ducks use tryptophan as a significant source of niacin. REFERENCES 1.
Briggs GM. Influence of gelatin and tryptophane on nicotinic acid requirement of chicks. J Biol Chem 1945;161:749-50.
2.
Bernard R, Demers JM. Inter-relationship de l'acide nicotinique et du tryptophane chez le caneton (p8kin blanc). Rev Can Biol 1949;8:504-08.
3.
Niacin and tryptophan requirements Wu L-S, Wu C-L, Shen T-F. Poult Sci of mule ducklings fed corn and soy-based diets. 1984; 63:153-58.
4.
Fisher Ii, Scott HM, Johnson BC. Quantitative aspects of the nicotinic acid-tryptophan interrelationship in the chick. Brit J Nutr 1955;9:340-49.
5.
Patterson EB, Hunt JR, Vohra P, Blaylock niacin and tryptophan requirements of 1956;35:499-504.
LG, McGinnis J. Poult chicks.
The Sci
TRYPTOPHAN-NIACINCONVERSION
103
6.
Childs GR, Carrick CW, Hauge SM. The niacin young chickens. Poult Sci 1952;31:551-58.
7.
Oh SY, Summers JD, Wood AS. Performance of chicks fed graded levels of niacin and tryptophan. Can J Anim Sci 1972;52:74550.
8.
Baker DH, Allen NK, Kleiss AJ. Efficiency of tryptophan as a niacin precursor in the young chick. J Anim Sci 1973;36:299302.
9.
DiLorenzo RN. Studies of the genetic variation in tryptophannicotinic acid conversion in chicks. Ph.D. thesis. Cornell University. 1972.
10.
Quantitative efficacy of niacin sources Oduho GW, Baker DE. nicotinic acid, nicotinamide, NAD and tryptophan. for chicks: J Nutr 1993:123:2201-06.
11.
Oduho GW, Han Y, Baker efficacy of tryptophan 1994;124:444-50.
12.
Nutrient requirements of ducks. Dean WF. Cornell Nutrition Conference, Syracuse, BY.
13.
National National
14.
Ruiz N, Harms RH. Comparison of the biopotencies of nicotinic Brit Poult Sci acid and nicotinamide for broiler chicks. 1988$29:491-98.
15.
Niacin requirement of broiler Ruiz N, Harms RH, Linda SB. chickens fed a corn-soybean meal diet from 1 to 21 days of age. Poult Sci 1990;69:433-39.
16.
Ikeda M, Tsuji Studies 0. dinucleotide. biosynthesis tryptophan in
17.
Henderson LY, Swan PB. Methods in Enzymology. Academic Wright LD eds.
18.
Association of Official Analytical Chemists. Official of Analysis. 12th ed. Arlington, VA. 1980:743-46.
19.
Wehler AH, McDaniel EG, Bundley JbX. Changes in the enzymatic I. Increase of picolinic carboxylase in composition of liver. J Biol Chem 1958;232:323-30. diabetes.
DE. as a
requirement
of
Iron deficiency reduces the niacin precursor. J Nutr In: Proceedings, 1978:132-40.
Nutrient requirements of poultry. Research Council. Academy of Sciences, Washington, DC. 1994.
H,Nakamura S, Ichiyama A, Nishizuka Y, Hayaishi on the biosynthesis of nicotinamide adenine carboxylase in the II. A role of picolinic nicotinamide from of adenine dinucleotide J Biol Chem 1965;240:1395-1401. mammals. Picolinic Vol XVIII, Press, NY.
acid carboxylase. Part B. McCormick 1971:175-80.
In: DB,
Methods
B.-J. CHEN etal.
104 20.
Nishizuka Y, Ichiyama A, Hayaishi 0. Metabolism of the benzene ring of tryptophan (mammals). In: Methods in Enzymology Vol Academic Press, NY. XVII, Part A. 1970:460-505.
21.
Duncan DB. Multiple 1955;11:1-42.
22.
Snedecor GW, Cochran WG. State Univ. Press, Ames,
23.
Penz AM Jr, Clifford AJ, Rogers QR, Kratzer PH. dietary leucine to influence the tryptophan-niacin the chicken. J Nutr 1984;114:33-41.
24.
Hayakawa T, Iwai SC. Effect of tryptophan and/or casein supplementation on NAD levels in livers of the rats fed on niacinand protein-free diet. J Nutr Sci Vitamin01 1984;30:303-06.
25.
Badawy AA-B, Evans W. The regulation of rat liver tryptophan pyrrolase activitybyreducednicotinamide-adenine dinucleotide (phosphate): experiments with glucose and nicotinamide. Biochem J 1976;156:381-90.
26.
Cho-Chung YS, Pitot EC. Feedback control of rat liver tryptophan pyrrolase. I. End product inhibition of tryptophan pyrrolase activity. J Biol Chem 1967;242:1192-98.
27.
Cho-Chung YS, Pitot HC. Regulatory effects of nicotinamide on tryptophan pyrrolase synthesis in rat liver in vivo. Europ J Biochem 1968;3:401-06.
28.
Knox WE, Mehler AH. The conversion of tryptophan to kynurenine in liver. I. The coupled tryptophan peroxidase-oxidase system forming formylkynurenine. J Biol Chem 1950;187:419-30.
29.
Mehler AH, Knox, WE. The conversion of tryptophan kynurenine in liver. hydrolysis II. The enzymatic formylkynurenine. J Biol Chem 1950;187:431-38.
30.
Lan SJ, Gholson RK. A comparative study catabolism. J Biol Chem 1965;240:3934-37.
31.
Knowles RG, Clarkson NA, Pogson CI, Salter M, Duch DS, Edelstein MP. The role of tryptophan and kynurenine transport in the catabolism of tryptophan through indoleamine 2,3Kynurenine and Serotonin Pathways, eds. dioxygenase. Press, NY. RR, Plenum Schwartz R, Y:;, SN, and Brown 21991;161-66.
Accepted
for
publication
June
range
16,
and multiple
F tests.
Biometrics
Statistical Methods. 7th ed., Iowa IA. 1980:169-71, 233-36, 289-330.
1995.
of
Failure pathway
of in
to of
tryptophan