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Effects of niacin status on tryptophan requirements of starter white Pekin ducks
Livestock Science 159 (2014) 75–78
Contents lists available at ScienceDirect
Livestock Science journal homepage: www.elsevier.com/locate/livsci
Short communication
Effects of niacin status on tryptophan requirements of starter white Pekin ducks M. Xie a, X.F. Han b, W. Huang a, S.S. Hou a,n a b
Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China
a r t i c l e i n f o
abstract
Article history: Received 26 March 2013 Received in revised form 12 September 2013 Accepted 29 October 2013
A 4 5 factorial experiment, using 4 supplemental nicotinamide levels (0, 40, 80, and 120 mg/kg) and 5 dietary Trp levels (1.32, 1.67, 2.02, 2.37, and 2.72 g/kg), was conducted to study the effects of niacin status on Trp requirements for growth of starter white Pekin ducks from hatch to 3 wk of age. Eight hundred and forty 1-d-old male white Pekin ducks were assigned to 20 treatments with 6 replicate pens and 7 ducks per pen. All ducks were reared in raised wire-floor pens from hatch to 21d of age. No supplementation of nicotinamide in diets caused bowed leg deformity regardless of dietary Trp levels and the 40 mg and greater supplemental nicotinamide/kg completely prevented bowed leg deformity at all Trp levels. The interaction between nicotinamide and Trp influenced weight gain and feed intake of ducks (P o 0.001). Supplementation of Trp in diets alleviated the depression of weight gain and feed intake caused by niacin deficiency at 0 mg supplemental nicotinamide/kg, but supplementation of nicotinamide in diets did not alleviate the depression of weight gain and feed intake caused by dietary Trp deficiency (1.32 g Trp/kg). According to the broken-line regression, the Trp requirements of starter Pekin ducks for weight gain from hatch to 3 wk of age at 0, 40, 80, and 120 mg/kg of supplemental nicotinamide were 2.42, 1.68, 1.69, and 1.69 g/kg, respectively, and the Trp requirement was much greater at 0 mg/kg of supplemental nicotinamide than at other 3 supplemental nicotinamide levels (P o 0.05). In conclusion, the interaction between niacin and Trp in duck diets was supported by the effects of niacin status on Trp requirements of starter white Pekin ducks and niacin deficiency markedly increased the Trp requirements of white Pekin ducks. & 2013 Published by Elsevier B.V.
Keywords: Ducks Niacin Nicotinamide Tryptophan
1. Introduction Tryptophan is an indispensable amino acid for poultry and supplementation of Trp in diets could linearly increase growth performance of Pekin ducks when supplied below but not above the requirement (Adeola, 1998). However, there is still little information in the literatures about Trp requirements for ducks. The Trp recommendation of NRC (1994) for Pekin ducks was based on the only 1 literature
n
Corresponding author. Tel.: þ86 10 62816227; fax: þ86 10 62815832. E-mail address: [email protected] (S.S. Hou).
1871-1413/$ - see front matter & 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.livsci.2013.10.029
reported by Wu et al. (1984) who estimated the minimum Trp requirement of mule ducklings to be 0.23% of the diet for maximum growth and feed efficiency. On the other hand, Trp has niacin-sparing activity because of its conversion to niacin (Heidelberger et al., 1949). In rat, more dietary Trp was required by niacin-deficient rats compared with normal rats (Salmon, 1954). In broilers, the greater niacin level improved the effectiveness of the Trp and apparently decreased the minimum requirement for Trp (West et al., 1952). However, in ducks, although the interrelationship between niacin and Trp were examined in Pekin or mule ducks by a 2-factor design (Chen et al., 1996; Wu et al., 1984), the quantitative effects of niacin on
76
M. Xie et al. / Livestock Science 159 (2014) 75–78
Trp requirements of ducks was not clear. Therefore, the objective of present study was to estimate the Trp requirements of white Pekin ducks from deficient to adequate niacin levels and to evaluate the effects of niacin status on the requirements of Trp for ducks. 2. Materials and methods 2.1. Experimental design and duck husbandry All procedures of our experiments were approved by the animal care and use committee of Institute of Animal Sciences of Chinese Academy of Agricultural Sciences. A 4 5 factorial arrangement with 4 supplemental nicotinamide levels (0, 40, 80, and 120 mg/kg) and 5 dietary Trp levels (1.32, 1.67, 2.02, 2.37, and 2.72 g/kg) was utilized in the study. A total of 840 one-d-old male white Pekin ducks with average body weight of 5372 g were assigned to 20 experimental treatments and each treatment contained 6 replicate pens with 7 ducks per pen. Ducks were reared in raised wire-floor pens (200 cm 100 cm 40 cm) from hatch to 21 d of age. During this period, ducks had free access to water and feed. Water was provided by dripnipple water supply lines and feed was fed in pellet form. In the birdhouse, lighting was continuous and the temperature was kept at 33 1C from 1 to 3 d of age and then it was reduced gradually to room temperature until 21 d of age. 2.2. Diet and chemical analysis A corn–corn gluten meal basal diet that was low in both Trp and niacin was formulated (Table 1). To produce experimental diets, the basal diets were supplemented with different levels of L-Trp (0, 0.35, 0.70, 1.05, and 1.40 g/kg) and nicotinamide (0, 40, 80, and 120 mg/kg). The supplemental nicotinamide content in diets was confirmed by reverse-phase high performance liquid chromatography and ultraviolet detection after being extracted by water according to the method recommended by Ministry of Agriculture of China (2012) and the total Trp content in diets were confirmed by reverse-phase high performance liquid chromatography and fluorometric detection after hydrolysis at 110 1C for 20 h with barium hydroxide according to the method recommended by Standardization Administration of China (2000).
Table 1 Composition of basal diets (as-fed basis). Item Ingredient, g/kg Corn Corn gluten meal Peanut meal CaHPO4 Limestone Sodium chloride DL-Met L-Lys HCL L-Thr Premixa Total Calculated composition Metabolizable energy (MJ/kg)b Crude protein (g/kg) Ca (g/kg) Nonphytate P (g/kg) Lys (g/kg) Met (g/kg) MetþCys (g/kg) Thr (g/kg) Trp (g/kg)c Niacin (mg/kg)
Content
715.0 170.0 65.0 15.0 10.0 3.0 1.2 8.8 2.0 10.0 1000.0 12.75 181.0 9.00 4.00 11.05 4.69 7.67 7.57 1.32 35
a Supplied per kilogram of total diet: Cu (CuSO4 5H2O), 8 mg; Fe (FeSO4 7H2O), 60 mg; Zn (ZnO), 60 mg; Mn (MnSO4 H2O), 100 mg; Se (NaSeO3), 0.3 mg; I (KI), 0.4 mg; choline chloride, 1000 mg; vitamin A (retinyl acetate), 4000 IU; vitamin D3 (cholcalciferol), 2000 IU; vitamin E (DL-α-tocopheryl acetate), 20 IU; vitamin K3 (menadione sodium bisulfate), 2 mg; thiamin (thiamin mononitrate), 2 mg; riboflavin, 10 mg; pyridoxine hydrochloride, 4 mg; cobalamin, 0.02 mg; calcium-D-pantothenate, 20 mg; folic acid, 1 mg; and biotin, 0.15 mg. b The value is calculated according to the AME of chickens (Ministry of Agriculture of China, 2004). c The numbers are values analyzed by high performance liquid chromatography.
At 21 d of age, the weight gain, feed intake and feed/ gain of each pen were determined and the incidence of bowed leg deformity from each treatment group was recorded according to the symptom of bowed legs in ducks observed by Heuser and Scott (1953). Feed intake and feed/gain were all corrected for mortality.
and quadratic polynomial contrasts were performed to determine the effects of supplemental nicotinamide and dietary Trp. The variability in the data was expressed as the standard error of the means (SEM) and a probability level of Po0.05 was considered to be statistically significant. In our study, when regression was significant (Po0.05), the broken-line regression analysis (Robbins et al., 2006) was used to estimate the Trp requirements of ducks at each supplemental nicotinamide level using the NLIN procedure of SAS (SAS Inst. Inc., Cary, NC, US) and the broken-line model was: y¼lþu(rx), where y¼weight gain, x¼dietary Trp level (g/kg), r¼Trp requirement, l¼ weight gain at x¼ r, and u¼the steepness of the curve. In this model, y¼l when x4r. In addition, according to the statistical method suggested by Sterling et al. (2003), a ttest was used to determine if the difference (Po0.05) existed for the Trp requirements established between at no supplemental nicotinamide level and at other 3 supplemental nicotinamide levels.
2.4. Statistical analysis
3. Results and discussion
Data were analyzed by 2-way ANOVA procedure of SAS (SAS Inst. Inc., Cary, NC, US) with the pen being used as the experimental unit. The model utilized included the effects of nicotinamide and Trp, as well as the interaction. Linear
In the present study, because of the poor availability of niacin in grain and grain by-products (Manoukas et al., 1968; Yen et al., 1977), the corn and corn gluten meal were used as the main ingredients of basal diets, and their
2.3. Experimental data collection
M. Xie et al. / Livestock Science 159 (2014) 75–78
contribution to meet niacin adequacy may have been very limited, although the calculated niacin in the basal diet was 35 mg/kg. Bowed leg and growth depression were the characteristic symptom of niacin deficiency for ducks (Hegsted, 1946; Heuser and Scott, 1953; Scott and Heuser, 1952). No supplementation of nicotinamide in diets caused bowed leg deformity regardless of dietary Trp levels and the depression of weight gain and feed intake was also observed in these ducks (Table 2), which indicated that the basal diet was niacin-deficient. Fortunately, 40 mg and greater supplemental nicotinamide/kg completely prevented bowed leg deformity at all Trp levels in our study. Tryptophan had more growth-promoting effect than niacin because increasing dietary Trp increased weight gain and feed intake and decreased feed/gain linearly and quadratically (Po 0.001), but it was not true for increasing nicotinamide. As precursor amino acid, Trp could be converted to niacin (Heidelberger et al., 1949) and the precursor amino acid would be the first growth-limiting factor when a precursor amino acid and its corresponding vitamin deficiencies coexisted (Czarnecki et al., 1982), which was clearly supported by the Trp nicotinamide interaction in our data. In the present study, the response of weight gain and feed intake to increasing nicotinamide was small until dietary Trp was 1.67 g/kg and above but
77
the response in weight gain and feed intake to increasing Trp was large at all supplemental nicotinamide levels (0–120 mg/kg). Furthermore, supplementation of Trp in diets could alleviate the depression of weight gain and feed intake caused by niacin deficiency at 0 mg supplemental nicotinamide/kg, but supplementation of nicotinamide in diets could not alleviate the depression of weight gain and feed intake caused by Trp deficiency (1.32 g Trp/ kg). Our results were in agreement with the conclusion of Wu et al. (1984) who found that excess Trp could spare the mule duckling's need for niacin but excess niacin failed to compensate for Trp deficiency. On the other hand, the interaction between niacin and Trp on growth performance in our study could also be explained by the effects of niacin status on Trp requirements of ducks, which is different from the previous research in ducks (Chen et al., 1996; Wu et al., 1984). The Trp requirements of ducks for weight gain at each supplemental nicotinamide level were all estimated by brokenline regression (Table 3) and these estimated requirements were identical with the observed gain response data (Table 2), which also indicated that this regression was appropriate for estimation of Trp requirements in our study. According to the regression, the Trp requirements for optimal weight gain occurred at 2.42 g/kg for ducks fed basal diets with no supplemental nicotinamide and 1.68,
Table 2 Effects of nicotinamide and Trp on growth performance of Pekin ducks from hatch to 3 wk of age. Dietary treatment
Weight gain (g/bird/d)
Feed intake (g/bird/d)
Feed/gain (g/g)
Incidence of bowed leg deformity (%)
Supplemental nicotinamide (mg/kg)
Dietary Trp (g/kg)
0
1.32 1.67 2.02 2.37 2.72
12.9 24.8 40.9 44.6 49.0
23.7 39.6 64.1 71.9 81.9
1.85 1.60 1.57 1.61 1.67
40 37 34 13 6
40
1.32 1.67 2.02 2.37 2.72
13.3 49.4 52.0 50.3 50.0
25.7 80.6 87.5 83.2 81.9
1.96 1.63 1.68 1.66 1.64
0 0 0 0 0
80
1.32 1.67 2.02 2.37 2.72
17.7 48.2 51.6 50.4 48.5
33.3 80.0 89.2 85.1 82.4
1.88 1.66 1.73 1.69 1.70
0 0 0 0 0
120
1.32 1.67 2.02 2.37 2.72
15.8 48.6 52.0 49.5 51.3
32.2 81.2 88.4 83.8 87.4
2.03 1.67 1.70 1.69 1.70
0 0 0 0 0
1.3
2.2
0.01
o0.001 o0.001 o0.001 0.390 0.551 o0.001 o0.001
o 0.001 o 0.001 o 0.001 0.254 0.500 o 0.001 o 0.001
o 0.001 o 0.001 0.068 0.230 0.806 o 0.001 o 0.001
Pooled SEM Probability Nicotinamide Trp Nicotinamide Trp Nicotinamide linear Nicotinamide quadratic Trp linear Trp quadratic
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M. Xie et al. / Livestock Science 159 (2014) 75–78
Table 3 Tryptophan requirements for weight gain at different supplemental nicotinamide levels according to broken-line regression. Nicotinamide Broken-line model (mg/kg) 0 40 80 120
Y ¼49.0 31.8 (2.42 x) Y ¼ 50.8 103.1 (1.68 x) Y ¼ 50.2 87.1 (1.69 x) Y ¼ 50.9 93.7 (1.69 x)
R2
Trp requirement (g/kg) a
0.967 0.998 0.994 0.997
2.42 7 0.16 1.687 0.01b 1.69 7 0.02b 1.69 7 0.02b
a
It was expressed as requirement7 SE. Compared with the Trp requirement at 0 mg supplemental nicotinamide/kg diet, the requirement was considered different (Po 0.05). b
1.69, and 1.69 g/kg for ducks fed basal diets with 40, 80, and 120 mg/kg of supplemental nicotinamide, respectively (Table 3). The t-test showed that the Trp requirement at no supplemental nicotinamide level was much greater than the requirements of Trp at 40, 80 and 120 mg/kg of supplemental nicotinamide (Po0.05). Therefore, it was clearly showed that niacin deficiency markedly increased the Trp requirements for ducks, and this result also indicated that surplus Trp above the requirement may be converted to niacin in absence of the vitamin. 4. Conclusion The interaction between niacin and Trp in duck diets was supported by the effects of niacin status on Trp requirements of starter white Pekin ducks. And niacin deficiency markedly increased the Trp requirements for ducks. Conflict of interest statement None. Acknowledgment This work was sponsored by National Scientific and Technical Supporting program of China (2012BAD39B0404)
and Chinese Earmarked Fund for Special Fund for Agroscientific Research in the Public Interest (200903006). References Adeola, O., 1998. Bioavailability of tryptophan in soybean meal and tryptophan retention in the carcasses of four-week-old ducks. Poult. Sci. 77, 1312–1319. Chen, B.J., Shen, T.F., Austic, R.E., 1996. Efficiency of tryptophan–niacin conversion in chickens and ducks. Nutr. Res. 16, 91–104. Czarnecki, G.L., Halpin, K.M., Baker, D.H., 1982. Precursor (amino acid): product (vitamin) interrelationship for growing chicks as illustrated by tryptophan–niacin and methionine–choline. Poult. Sci. 62, 371–374. Hegsted, D.M., 1946. Nutritional studies with the duck. III. Niacin deficiency. J. Nutr. 32, 467–472. Heidelberger, C., Abraham, E.P., Lepkovsky, S., 1949. Tryptophan metabolism. II. Concerning the mechanism of the mammalian conversion of tryptophan into nicotinic acid. J. Biol. Chem. 179, 151–155. Heuser, G.F., Scott, M.L., 1953. Studies in duck nutrition. 5. Bowed legs in ducks, a nutritional disorder. Poult. Sci. 32, 137–143. Manoukas, A.G., Ringrose, R.C., Teeri, A.E., 1968. The availability of niacin in corn, soybean meal and wheat middlings for the hen. Poult. Sci. 47, 1836–1842. Ministry of Agriculture of China, 2004. Feeding Standard of Chicken. Standards Press of China, Beijing, China. Ministry of Agriculture of China, 2012. Determination of Niacinamide in Feeds: High-Pressure Liquid Chromatography. China Agriculture Press, Beijing, China. NRC, 1994. Nutrient Requirements of Poultry, 9th rev. ed. National Academy Press, Washington, DC. Robbins, K.R., Saxton, A.M., Southern, L.L., 2006. Estimation of nutrient requirements using broken-line regression analysis. J. Anim. Sci. 84, E155–E165. Salmon, W.D., 1954. The tryptophan requirement of the rat as affected by niacin and level of dietary nitrogen. Arch. Biochem. 51, 30–41. Scott, M.L., Heuser, G.F., 1952. Studies in Duck nutrition 4. Bowed legs in ducks caused by niacin deficiency. Poult. Sci. 41, 752–754. Standardization Administration of China, 2000. Determination of Amino Acids in Feeds. Standards Press of China, Beijing, China. Sterling, K.G., Pesti, G.M., Bakalli, R.I., 2003. Performance of broiler chicks fed various levels of dietary lysine and crude protein. Poult. Sci. 82, 1939–1947. West, J.W., Carrick, C.W., Hauge, S.M., Mertz, E.T., 1952. The tryptophan requirement of young chickens as influenced by niacin. Poult. Sci. 31, 479–487. Wu, L.S., Wu, C.L., Shen, T.F., 1984. Niacin and tryptophan requirements of mule ducklings fed corn and soy-based diets. Poult. Sci. 63, 153–158. Yen, J.T., Jensen, A.H., Baker, D.H., 1977. Assessment of the availability of niacin in corn, soybeans and soybean meal. J. Anim. Sci. 45, 269–278.
Contents lists available at ScienceDirect
Livestock Science journal homepage: www.elsevier.com/locate/livsci
Short communication
Effects of niacin status on tryptophan requirements of starter white Pekin ducks M. Xie a, X.F. Han b, W. Huang a, S.S. Hou a,n a b
Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China
a r t i c l e i n f o
abstract
Article history: Received 26 March 2013 Received in revised form 12 September 2013 Accepted 29 October 2013
A 4 5 factorial experiment, using 4 supplemental nicotinamide levels (0, 40, 80, and 120 mg/kg) and 5 dietary Trp levels (1.32, 1.67, 2.02, 2.37, and 2.72 g/kg), was conducted to study the effects of niacin status on Trp requirements for growth of starter white Pekin ducks from hatch to 3 wk of age. Eight hundred and forty 1-d-old male white Pekin ducks were assigned to 20 treatments with 6 replicate pens and 7 ducks per pen. All ducks were reared in raised wire-floor pens from hatch to 21d of age. No supplementation of nicotinamide in diets caused bowed leg deformity regardless of dietary Trp levels and the 40 mg and greater supplemental nicotinamide/kg completely prevented bowed leg deformity at all Trp levels. The interaction between nicotinamide and Trp influenced weight gain and feed intake of ducks (P o 0.001). Supplementation of Trp in diets alleviated the depression of weight gain and feed intake caused by niacin deficiency at 0 mg supplemental nicotinamide/kg, but supplementation of nicotinamide in diets did not alleviate the depression of weight gain and feed intake caused by dietary Trp deficiency (1.32 g Trp/kg). According to the broken-line regression, the Trp requirements of starter Pekin ducks for weight gain from hatch to 3 wk of age at 0, 40, 80, and 120 mg/kg of supplemental nicotinamide were 2.42, 1.68, 1.69, and 1.69 g/kg, respectively, and the Trp requirement was much greater at 0 mg/kg of supplemental nicotinamide than at other 3 supplemental nicotinamide levels (P o 0.05). In conclusion, the interaction between niacin and Trp in duck diets was supported by the effects of niacin status on Trp requirements of starter white Pekin ducks and niacin deficiency markedly increased the Trp requirements of white Pekin ducks. & 2013 Published by Elsevier B.V.
Keywords: Ducks Niacin Nicotinamide Tryptophan
1. Introduction Tryptophan is an indispensable amino acid for poultry and supplementation of Trp in diets could linearly increase growth performance of Pekin ducks when supplied below but not above the requirement (Adeola, 1998). However, there is still little information in the literatures about Trp requirements for ducks. The Trp recommendation of NRC (1994) for Pekin ducks was based on the only 1 literature
n
Corresponding author. Tel.: þ86 10 62816227; fax: þ86 10 62815832. E-mail address: [email protected] (S.S. Hou).
1871-1413/$ - see front matter & 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.livsci.2013.10.029
reported by Wu et al. (1984) who estimated the minimum Trp requirement of mule ducklings to be 0.23% of the diet for maximum growth and feed efficiency. On the other hand, Trp has niacin-sparing activity because of its conversion to niacin (Heidelberger et al., 1949). In rat, more dietary Trp was required by niacin-deficient rats compared with normal rats (Salmon, 1954). In broilers, the greater niacin level improved the effectiveness of the Trp and apparently decreased the minimum requirement for Trp (West et al., 1952). However, in ducks, although the interrelationship between niacin and Trp were examined in Pekin or mule ducks by a 2-factor design (Chen et al., 1996; Wu et al., 1984), the quantitative effects of niacin on
76
M. Xie et al. / Livestock Science 159 (2014) 75–78
Trp requirements of ducks was not clear. Therefore, the objective of present study was to estimate the Trp requirements of white Pekin ducks from deficient to adequate niacin levels and to evaluate the effects of niacin status on the requirements of Trp for ducks. 2. Materials and methods 2.1. Experimental design and duck husbandry All procedures of our experiments were approved by the animal care and use committee of Institute of Animal Sciences of Chinese Academy of Agricultural Sciences. A 4 5 factorial arrangement with 4 supplemental nicotinamide levels (0, 40, 80, and 120 mg/kg) and 5 dietary Trp levels (1.32, 1.67, 2.02, 2.37, and 2.72 g/kg) was utilized in the study. A total of 840 one-d-old male white Pekin ducks with average body weight of 5372 g were assigned to 20 experimental treatments and each treatment contained 6 replicate pens with 7 ducks per pen. Ducks were reared in raised wire-floor pens (200 cm 100 cm 40 cm) from hatch to 21 d of age. During this period, ducks had free access to water and feed. Water was provided by dripnipple water supply lines and feed was fed in pellet form. In the birdhouse, lighting was continuous and the temperature was kept at 33 1C from 1 to 3 d of age and then it was reduced gradually to room temperature until 21 d of age. 2.2. Diet and chemical analysis A corn–corn gluten meal basal diet that was low in both Trp and niacin was formulated (Table 1). To produce experimental diets, the basal diets were supplemented with different levels of L-Trp (0, 0.35, 0.70, 1.05, and 1.40 g/kg) and nicotinamide (0, 40, 80, and 120 mg/kg). The supplemental nicotinamide content in diets was confirmed by reverse-phase high performance liquid chromatography and ultraviolet detection after being extracted by water according to the method recommended by Ministry of Agriculture of China (2012) and the total Trp content in diets were confirmed by reverse-phase high performance liquid chromatography and fluorometric detection after hydrolysis at 110 1C for 20 h with barium hydroxide according to the method recommended by Standardization Administration of China (2000).
Table 1 Composition of basal diets (as-fed basis). Item Ingredient, g/kg Corn Corn gluten meal Peanut meal CaHPO4 Limestone Sodium chloride DL-Met L-Lys HCL L-Thr Premixa Total Calculated composition Metabolizable energy (MJ/kg)b Crude protein (g/kg) Ca (g/kg) Nonphytate P (g/kg) Lys (g/kg) Met (g/kg) MetþCys (g/kg) Thr (g/kg) Trp (g/kg)c Niacin (mg/kg)
Content
715.0 170.0 65.0 15.0 10.0 3.0 1.2 8.8 2.0 10.0 1000.0 12.75 181.0 9.00 4.00 11.05 4.69 7.67 7.57 1.32 35
a Supplied per kilogram of total diet: Cu (CuSO4 5H2O), 8 mg; Fe (FeSO4 7H2O), 60 mg; Zn (ZnO), 60 mg; Mn (MnSO4 H2O), 100 mg; Se (NaSeO3), 0.3 mg; I (KI), 0.4 mg; choline chloride, 1000 mg; vitamin A (retinyl acetate), 4000 IU; vitamin D3 (cholcalciferol), 2000 IU; vitamin E (DL-α-tocopheryl acetate), 20 IU; vitamin K3 (menadione sodium bisulfate), 2 mg; thiamin (thiamin mononitrate), 2 mg; riboflavin, 10 mg; pyridoxine hydrochloride, 4 mg; cobalamin, 0.02 mg; calcium-D-pantothenate, 20 mg; folic acid, 1 mg; and biotin, 0.15 mg. b The value is calculated according to the AME of chickens (Ministry of Agriculture of China, 2004). c The numbers are values analyzed by high performance liquid chromatography.
At 21 d of age, the weight gain, feed intake and feed/ gain of each pen were determined and the incidence of bowed leg deformity from each treatment group was recorded according to the symptom of bowed legs in ducks observed by Heuser and Scott (1953). Feed intake and feed/gain were all corrected for mortality.
and quadratic polynomial contrasts were performed to determine the effects of supplemental nicotinamide and dietary Trp. The variability in the data was expressed as the standard error of the means (SEM) and a probability level of Po0.05 was considered to be statistically significant. In our study, when regression was significant (Po0.05), the broken-line regression analysis (Robbins et al., 2006) was used to estimate the Trp requirements of ducks at each supplemental nicotinamide level using the NLIN procedure of SAS (SAS Inst. Inc., Cary, NC, US) and the broken-line model was: y¼lþu(rx), where y¼weight gain, x¼dietary Trp level (g/kg), r¼Trp requirement, l¼ weight gain at x¼ r, and u¼the steepness of the curve. In this model, y¼l when x4r. In addition, according to the statistical method suggested by Sterling et al. (2003), a ttest was used to determine if the difference (Po0.05) existed for the Trp requirements established between at no supplemental nicotinamide level and at other 3 supplemental nicotinamide levels.
2.4. Statistical analysis
3. Results and discussion
Data were analyzed by 2-way ANOVA procedure of SAS (SAS Inst. Inc., Cary, NC, US) with the pen being used as the experimental unit. The model utilized included the effects of nicotinamide and Trp, as well as the interaction. Linear
In the present study, because of the poor availability of niacin in grain and grain by-products (Manoukas et al., 1968; Yen et al., 1977), the corn and corn gluten meal were used as the main ingredients of basal diets, and their
2.3. Experimental data collection
M. Xie et al. / Livestock Science 159 (2014) 75–78
contribution to meet niacin adequacy may have been very limited, although the calculated niacin in the basal diet was 35 mg/kg. Bowed leg and growth depression were the characteristic symptom of niacin deficiency for ducks (Hegsted, 1946; Heuser and Scott, 1953; Scott and Heuser, 1952). No supplementation of nicotinamide in diets caused bowed leg deformity regardless of dietary Trp levels and the depression of weight gain and feed intake was also observed in these ducks (Table 2), which indicated that the basal diet was niacin-deficient. Fortunately, 40 mg and greater supplemental nicotinamide/kg completely prevented bowed leg deformity at all Trp levels in our study. Tryptophan had more growth-promoting effect than niacin because increasing dietary Trp increased weight gain and feed intake and decreased feed/gain linearly and quadratically (Po 0.001), but it was not true for increasing nicotinamide. As precursor amino acid, Trp could be converted to niacin (Heidelberger et al., 1949) and the precursor amino acid would be the first growth-limiting factor when a precursor amino acid and its corresponding vitamin deficiencies coexisted (Czarnecki et al., 1982), which was clearly supported by the Trp nicotinamide interaction in our data. In the present study, the response of weight gain and feed intake to increasing nicotinamide was small until dietary Trp was 1.67 g/kg and above but
77
the response in weight gain and feed intake to increasing Trp was large at all supplemental nicotinamide levels (0–120 mg/kg). Furthermore, supplementation of Trp in diets could alleviate the depression of weight gain and feed intake caused by niacin deficiency at 0 mg supplemental nicotinamide/kg, but supplementation of nicotinamide in diets could not alleviate the depression of weight gain and feed intake caused by Trp deficiency (1.32 g Trp/ kg). Our results were in agreement with the conclusion of Wu et al. (1984) who found that excess Trp could spare the mule duckling's need for niacin but excess niacin failed to compensate for Trp deficiency. On the other hand, the interaction between niacin and Trp on growth performance in our study could also be explained by the effects of niacin status on Trp requirements of ducks, which is different from the previous research in ducks (Chen et al., 1996; Wu et al., 1984). The Trp requirements of ducks for weight gain at each supplemental nicotinamide level were all estimated by brokenline regression (Table 3) and these estimated requirements were identical with the observed gain response data (Table 2), which also indicated that this regression was appropriate for estimation of Trp requirements in our study. According to the regression, the Trp requirements for optimal weight gain occurred at 2.42 g/kg for ducks fed basal diets with no supplemental nicotinamide and 1.68,
Table 2 Effects of nicotinamide and Trp on growth performance of Pekin ducks from hatch to 3 wk of age. Dietary treatment
Weight gain (g/bird/d)
Feed intake (g/bird/d)
Feed/gain (g/g)
Incidence of bowed leg deformity (%)
Supplemental nicotinamide (mg/kg)
Dietary Trp (g/kg)
0
1.32 1.67 2.02 2.37 2.72
12.9 24.8 40.9 44.6 49.0
23.7 39.6 64.1 71.9 81.9
1.85 1.60 1.57 1.61 1.67
40 37 34 13 6
40
1.32 1.67 2.02 2.37 2.72
13.3 49.4 52.0 50.3 50.0
25.7 80.6 87.5 83.2 81.9
1.96 1.63 1.68 1.66 1.64
0 0 0 0 0
80
1.32 1.67 2.02 2.37 2.72
17.7 48.2 51.6 50.4 48.5
33.3 80.0 89.2 85.1 82.4
1.88 1.66 1.73 1.69 1.70
0 0 0 0 0
120
1.32 1.67 2.02 2.37 2.72
15.8 48.6 52.0 49.5 51.3
32.2 81.2 88.4 83.8 87.4
2.03 1.67 1.70 1.69 1.70
0 0 0 0 0
1.3
2.2
0.01
o0.001 o0.001 o0.001 0.390 0.551 o0.001 o0.001
o 0.001 o 0.001 o 0.001 0.254 0.500 o 0.001 o 0.001
o 0.001 o 0.001 0.068 0.230 0.806 o 0.001 o 0.001
Pooled SEM Probability Nicotinamide Trp Nicotinamide Trp Nicotinamide linear Nicotinamide quadratic Trp linear Trp quadratic
78
M. Xie et al. / Livestock Science 159 (2014) 75–78
Table 3 Tryptophan requirements for weight gain at different supplemental nicotinamide levels according to broken-line regression. Nicotinamide Broken-line model (mg/kg) 0 40 80 120
Y ¼49.0 31.8 (2.42 x) Y ¼ 50.8 103.1 (1.68 x) Y ¼ 50.2 87.1 (1.69 x) Y ¼ 50.9 93.7 (1.69 x)
R2
Trp requirement (g/kg) a
0.967 0.998 0.994 0.997
2.42 7 0.16 1.687 0.01b 1.69 7 0.02b 1.69 7 0.02b
a
It was expressed as requirement7 SE. Compared with the Trp requirement at 0 mg supplemental nicotinamide/kg diet, the requirement was considered different (Po 0.05). b
1.69, and 1.69 g/kg for ducks fed basal diets with 40, 80, and 120 mg/kg of supplemental nicotinamide, respectively (Table 3). The t-test showed that the Trp requirement at no supplemental nicotinamide level was much greater than the requirements of Trp at 40, 80 and 120 mg/kg of supplemental nicotinamide (Po0.05). Therefore, it was clearly showed that niacin deficiency markedly increased the Trp requirements for ducks, and this result also indicated that surplus Trp above the requirement may be converted to niacin in absence of the vitamin. 4. Conclusion The interaction between niacin and Trp in duck diets was supported by the effects of niacin status on Trp requirements of starter white Pekin ducks. And niacin deficiency markedly increased the Trp requirements for ducks. Conflict of interest statement None. Acknowledgment This work was sponsored by National Scientific and Technical Supporting program of China (2012BAD39B0404)
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