Skip to main content
NCBI home page
The Journal of Poultry Science logoLink to The Journal of Poultry Science
. 2023 Feb 9;60(2):2023008. doi: 10.2141/jpsa.2023008

Effects of Dietary Tryptophan on Growth Performance, Plasma Parameters, and Internal Organs of 1–28-Day-Old Sichuan White Geese

Yang Fu 1, Bo Liu 2, Hui Lei 1, Zhenping Lin 3, JunPeng Chen 3, Yongwen Zhu 1, Hui Ye 1, Lin Yang 1, Wence Wang 1
PMCID: PMC10072300  PMID: 37025655

Abstract

Although the nutrient requirements of geese during the growing stage are known, the dietary requirement of amino acids during the starting period remains unclear. Optimum nutrient supplementation during the starting period is crucial for improved survival rates, body-weight gain, and marketing weight in geese. Our study focused on the effect of dietary tryptophan (Trp) supplementation on the growth performance, plasma parameters, and internal-organ relative weights in 1–28-day-old Sichuan white geese. A total of 1080 1-day-old geese were divided randomly into six Trp-supplemented (0.145%, 0.190%, 0.235%, 0.280%, 0.325%, and 0.370%) groups. Average daily feed intake (ADFI), average daily gain (ADG), and duodenal relative weight were highest in the 0.190% group, brisket protein level and jejunal relative weight in the 0.235% group, and plasma total protein and albumin levels in the 0.325% group (P < 0.05). Dietary Trp supplementation did not significantly affect the relative weights of the spleen, thymus, liver, bursa of Fabricius, kidneys, and pancreas. Moreover, the 0.145% – 0.235% groups showed significantly decreased liver fat (P < 0.05). Based on the non-linear regression analysis of ADG and ADFI, the dietary Trp levels between 0.183% and 0.190% were estimated to be optimal for 1–28-day-old Sichuan white geese. In conclusion, optimal dietary Trp supplementation in 1–28-day-old Sichuan white geese resulted in increased growth performance (0.180% – 0.190%) along with improved proximal intestinal development and brisket protein deposition (0.235%). Our findings provide basic evidence and guidance for optimal levels of Trp supplementation in geese.

Keywords: intestine, protein deposition, Sichuan white goose, tryptophan, relative weight

INTRODUCTION

Tryptophan (Trp) is an essential amino acid in poultry and plays a role in several physiological functions such as protein synthesis, immune response, and appetite regulation. A moderate Trp deficiency in the diet, especially in corn-based diets, can significantly reduce both the feed intake and growth rate in animals (Eder et al., 2001; Le Floc’h et al., 2011 ; Kwon et al., 2022). Increased Trp utilization is associated with the activation of immune tolerance and a reduction in inflammation (Wolf et al., 2004; Scott et al., 2009; Wensley et al., 2020; Fouad et al., 2021). The amino acid requirements of geese may change from those in the newborn to those in the adult owing to their accelerated growth and changes in physiological features over time. Wei et al. (2011) demonstrated that the dietary Trp supplementation of up to 0.23% could increase daily feed intake, weight gain, and breast-meat yield in 28–70-day-old Yangzhou geese. It was also found that supplementing appropriate levels of Trp into a low-Trp diet can improve protein deposition (Fatufe et al., 2005). Dietary Trp levels of 0.22% significantly increased ADG and ADFI in 28–70-day-old Yangzhou geese and reduced protein degradation by upregulating TTS mRNA expression and pTOR phosphorylation and inhibiting the expression of histone B and 20S protease mRNA in thigh tissue (Pan et al., 2013). However, the Trp requirements of geese during the starting period (first 4 weeks of life) remain unclear.

Sichuan white geese are a native breed in Sichuan Province, China. It has recently received increased attention owing to its good growth performance, short feeding period, and tolerance to diseases. Sichuan white geese account for approximately a quarter of the total goose production in China and therefore are the most important production breed of geese in the country (Zhou et al., 2013; Zheng et al., 2014; Li et al., 2015; Yan et al., 2022). We hypothesized that appropriate dietary Trp supplementation could improve the growth performance of Sichuan white geese and affect their plasma parameters. Therefore, the objective of this study was to examine the effect of dietary Trp supplementation on the growth performance and plasma parameters, and the relative weights of the intestine and immune organs in 1–28-day-old Sichuan white geese.

MATERIALS AND METHODS

Birds and diets

This study was conducted in accordance with the guidelines of the Declaration of Helsinki, and all procedures involving animals were approved by the Committee of Animal Experiments of the South China Agricultural University (approval ID 21004152). A total of 1080 geese (1-day old, 1:1 male: female) with similar body weights (78 g) from Shantou Baisha Research Institute of Original Species of Poultry and Stock were randomly assigned to six groups, with six replicates in each group (30 geese per replicate). The treatment groups were fed a basal diet supplemented with Trp. The experimental Trp levels were 0.190%, 0.235%, 0.280%, 0.325%, and 0.370%, respectively. The duration of the experiment was 28 days. During the experiment, the geese were allowed free access to water and food. The composition and nutrient components of the diets are shown in Table 1.

Table 1.  Composition and nutrient content of the standard diet fed to each group (air-dry basis, %) of Sichuan white geese.

Ingredient (%) Values Nutrient level (%) Values
Corn 58.07 ME(MJ/kg) 11.99
Corn gluten meal 14.00 CP2 18.56
Wheat 3.50 CF 2.35
Wheat bran 12.50 Lys 1.06
Peanut meal 6.55 Met 0.44
DL-Met 0.13 Met+Cys 0.72
L-Lys-HCl 0.80 Ca 0.68
Limestone 1.20 TP 0.53
CaHPO4 0.90 AP 0.30
NaCl 0.35 Tryptophan 0.145
NaHCO3 1.00
L-Trp 0.00
Premix1 1.00
Total 100
Open in a new tab

ME, metabolizable energy; CP, crude protein; CF, crude fiber; AP, available phosphorus

1 Premix supplied the following constituents per kilogram of complete diet: vitamin A, 12,000 IU; vitamin D, 33,000 IU; vitamin E, 30 mg; vitamin K, 6 mg; vitamin B1, 3 mg; vitamin B2, 9 mg; vitamin B6, 6 mg; vitamin B12, 0.03 mg; D-pantothenic acid, 18 mg; nivotinic acid, 60 mg; folic acid, 1.5 mg; biotinm 0.15 mg; Fe, 80 mg; Cu, 8 mg; Mn, 96 mg; Zn, 80 mg; Co, 0.32 mg; Se, 0.32 mg; I, 0.56 mg.

2 Trp value was measured, whereas the other values were calculated.

Sample collection

On day 28, one bird was selected from each replicate and fasted overnight. The chosen geese (three males and three females) were euthanized by severing their jugular veins after anesthesia. Collection of blood samples during euthanasia. Blood samples containing 0.1 M sodium citrate as an anticoagulant were centrifuged at 3000 × g and 4 °C for 5 min, and the supernatants (plasma samples) were stored at -20 °C for biochemical parameter assays. The duodenum, jejunum, ileum, colon, rectum, spleen, kidney, liver, thymus, bursa of Fabricius, pancreas, and the breast and thigh muscles were collected for testing. The duodenum extended from the exit of the gizzard to the pancreatic duct (approximately 35–46 cm long), the jejunum from the pancreatic duct to the vitellicle, and the ileum from the vitellicle to the ileocecal junction. The jejunum-ileum was 110–175 cm in length. Samples from each part of the intestine were obtained from the middle of each of the three parts and were stored at -80 °C until needed. Tissue samples were stored at -20 °C during collection and at -80 °C until the next procedure.

Growth performance

The body weights of the geese were recorded once every 7 days to calculate the average daily gain (ADG), and daily feed consumption was recorded to calculate the average daily feed intake (ADFI) and feed/gain ratio (F/G).

Determination of plasma biochemical parameters

Assay kits for the analyses of plasma biochemical parameters were obtained from the Nanjing Jiancheng Biotechnology Company, China. The plasma globulin, albumin, total protein (TP), triglyceride (TG), uric acid (UA), total cholesterol (TC), glutamic-oxaloacetic transaminase (GOT), and glutamic-pyruvic transaminase (GPT) levels were determined using an Automatic Biochemistry Radiometer (AU640, Olympus Corporation, Tokyo, Japan).

Relative organ weights

The weights of the different organs (spleen, thymus, bursa of Fabricius, liver, and kidney) from the control and test groups were measured. The relative weights of the different organs for each animal were calculated as follows:

Relativeorganweight=Absoluteorganweight(g)Bodyweightofgeeseonthedayofsacrifice(g)×100%

Relative weight and length of the intestines

The weights of the duodenum, jejunum, ileum, colon, and rectum of the 28-day-old Sichuan white geese were measured. The relative organ weight of each segment of the intestine was calculated, as described above. The relative intestinal length was determined as the ratio of intestinal length to body weight.

Chemical composition

A representative sample was taken from the same part of each frozen liver, brisket, and thigh muscle, uniformed to the same weight, and then used for measurement. The chemical composition of the liver and the protein levels in the brisket and thigh muscles were determined as described by Liu et al. (2011). The values were calculated as percentages of the eviscerated carcass weight.

Statistical analysis

Data on growth performance and plasma parameters were presented as the mean and pooled standard error of the mean (SEM). Other data are presented as the mean ± SEM. Data were analyzed by one-way analysis of variance (ANOVA) using the GLM program of the SAS software (SAS Institute, Inc., Cary, NC, USA). Both linear and quadratic broken-line models (SAS NLIN procedure) were used to determine the breakpoint for a nutrient (Trp) requirement. Values of P < 0.05 were regarded as significant.

RESULTS

Growth performance in geese

As shown in Table 2, ADFI values increased from the 0.145% to the 0.235% group, and then decreased with further increases in the Trp levels in the diet (P < 0.05). ADFI and ADG were highest in the 0.190% group (P < 0.05). Moreover, a non-linear regression analysis showed that both ADFI and ADG exhibited cubic responses to increasing levels of dietary Trp. The regression equations are as follows:

YADG = 44.18-39.78(0.183-X) (X ≤ 0.183),
YADG = 44.18-12.78(X-0.183) (X > 0.183), R2 = 0.83, P = 0.0695
YADFI = 90.60-56.62(0.187-X) (X ≤ 0.187),
YADFI = 90.60-31.49(X-0.187) (X > 0.187), R2 = 0.87, P = 0.0483.

Table 2.  Effects of dietary tryptophan (Trp) levels on the growth performance of Sichuan white geese at 28 days of age.

Item Group Pooled SEM P value Contrast
0.145% 0.190% 0.235% 0.280% 0.325% 0.370% Linear Quadratic Cubic
ADFI (g) 88.24ab 90.92a 89.25ab 86.14bc 87.01bc 84.96c 0.90 <0.01 <0.01 0.09 0.05
ADG (g) 42.66b 44.40a 43.49ab 42.31b 42.28b 42.18b 0.52 0.02 0.02 0.22 0.02
F/G 2.07 2.05 2.05 2.04 2.06 2.02 0.03 0.85 0.32 0.92 0.50
Open in a new tab

a,b,c Means within rows with different superscript letters are significantly different (P < 0.05), whereas values with no letters or the same superscript letters are not significantly different (P > 0.05).

ADFI, average daily feed intake; ADG, average daily gain; F/G, feed/gain ratio

Based on the results of growth performance and non-linear regression analysis of ADFI and ADG, the dietary Trp requirement in 1–28-day-old Sichuan white geese was estimated to be between 0.183% and 0.190%, and the highest ADG and ADFI were achieved in the 0.190% Trp group.

Plasma biochemical parameters in geese

As shown in Table 3, the 0.145% group had the lowest albumin values, whereas the 0.325% group had the highest (P < 0.05). The TP concentration in the plasma significantly increased when the Trp level increased from 0.145% to 0.325% (P < 0.05). However, the plasma concentrations of globulin, TG, UA, and TC were not affected significantly by increasing Trp levels in the diet (P > 0.05). The 0.145% group had the highest levels of GOT and GPT, which then decreased with a further increase in the Trp levels in the diet (P > 0.05).

Table 3.  Effects of dietary tryptophan (Trp) levels on the plasma biochemical parameters of Sichuan white geese at 28 days of age.

Item Group Pooled
SEM		 P value Contrast
0.145% 0.190% 0.235% 0.280% 0.325% 0.370% Linear Quadratic Cubic
Globulin (mg/mL) 22.93 24.57 24.13 24.70 25.35 24.30 0.75 0.21 0.08 0.14 0.92
Albumin (mg/mL) 14.47b 15.82ab 15.68ab 15.67 ab 16.98a 15.50ab 0.43 0.02 0.03 0.05 0.62
TG (μmol/mL) 0.81 0.72 0.97 0.88 0.93 1.14 0.11 0.18 0.03 0.52 0.77
UA (nmol/mL) 288.33 360.00 278.50 317.00 269.83 253.50 29.62 0.17 0.07 0.21 0.38
TC (μmol/mL) 4.23 4.55 3.93 4.42 4.41 4.61 0.20 0.22 0.24 0.31 0.72
TP (mg/mL) 37.40b 40.38ab 39.82ab 40.37ab 42.33a 39.80ab 1.07 0.05 0.03 0.06 0.77
GOT (U/gprot) 16.04 15.46 13.00 12.76 14.13 13.93 0.17 0.14 <0.01 <0.01 0.93
GPT (U/gprot) 16.36 15.36 13.84 15.19 14.64 15.93 0.14 0.39 0.01 <0.01 0.14
Open in a new tab

a,b,c Means within rows with different superscript letters differ significantly (P < 0.05), whereas values with no letters or the same superscript letters do not differ significantly (P > 0.05).

TG, triglyceride; UA, uric acid; TC, total cholesterol; TP, total protein; GOT, glutamic-oxaloacetic transaminase; GPT, glutamic-pyruvic transaminase

Relative organ weights in geese

As shown in Table 4, dietary Trp supplementation had no significant effects on the relative weights of the spleen, thymus, bursa of Fabricius, liver, kidney, and pancreas in 28-day-old geese. The 0.190% group had the highest relative weights of the thymus and liver, but these differences were not significant (P > 0.05). Both the 0.190% and 0.235% groups had the highest relative weights for the spleen and kidney (P > 0.05).

Table 4.  Effects of dietary tryptophan (Trp) levels on the relative weights of the immune organs in Sichuan white geese at 28 days of age.

Item Group P value
0.145% 0.190% 0.235% 0.280% 0.325% 0.370%
Spleen 1.04±0.02 1.17±0.05 1.26±0.05 1.09±0.03 0.91±0.02 1.03±0.05 0.14
Thymus 2.43±0.09 2.65±0.07 2.47±0.10 2.05±0.08 1.96±0.04 2.20±0.0.7 0.08
Bursa of Fabricius 0.97±0.04 0.95±0.03 1.03±0.05 1.00±0.03 0.70±0.03 0.97±0.04 0.13
Liver 31.13±0.31 33.30±0.49 32.47±0.43 32.59±0.37 30.90±0.28 33.25±0.32 0.26
Kidney 8.46±0.21 10.19±0.19 10.42±0.17 9.75±0.32 9.59±0.09 9.11±0.20 0.10
Pancreas 4.42±0.11 5.05±0.08 4.88±0.10 5.08±0.09 4.75±0.07 4.92±0.15 0.18
Open in a new tab

a,b,c Means within rows with different superscript letters differ significantly (P < 0.05), whereas values with no letters or the same superscript letters do not differ significantly (P > 0.05). Data are presented as the mean and pooled SEM.

Relative length and weight of intestines in geese

As shown in Table 5, there were no significant differences in the relative intestinal lengths among the groups (P > 0.05). As shown in Table 6, the relative weight of the duodenum was the highest in the 0.190% group (P < 0.05) and that of the jejunum was highest in the 0.235% group (P < 0.05). Although the 0.190% group had the highest relative weight for the ileum, the differences were not significant (P > 0.05). There were no marked differences in the relative weights of the rectum, colon, and total intestine among the groups (P > 0.05).

Table 5.  Effects of dietary tryptophan (Trp) levels on the relative length of intestines in Sichuan white geese at 28 days of age.

Item Group P value
0.145% 0.190% 0.235% 0.280% 0.325% 0.370%
Duodenum 21.80±0.35 21.42±0.24 21.73±0.24 21.89±0.24 21.61±0.14 21.61±0.27 0.98
Jejunum 44.86±0.40 46.41±0.83 45.04±0.40 45.42±0.26 45.13±0.32 45.47±0.82 0.93
Ileum 43.43±0.23 43.58±0.44 43.62±0.37 41.85±0.27 43.70±0.09 41.84±0.53 0.30
Colon 18.62±0.61 19.88±0.20 20.54±0.23 19.32±0.13 20.65±0.18 20.00±0.28 0.34
Rectum 7.26±0.12 7.64±0.13 7.95±0.18 7.50±0.09 6.98±0.13 7.45±0.11 0.42
Total intestine 141.48±1.31 136.45±1.67 137.72±2.36 141.76±1.06 138.33±0.80 140.67±2.01 0.87
Open in a new tab

a,b,c Means within rows with different superscript letters differ significantly (P < 0.05), whereas values with no letters or the same superscript letters do not differ significantly (P > 0.05). Data are presented as the mean and pooled SEM.

Table 6.  Effects of dietary tryptophan (Trp) levels on the relative weights of the intestines in Sichuan white geese at 28 days of age.

Item Group P value
0.145% 0.190% 0.235% 0.280% 0.325% 0.370%
Duodenum 3.70±0.03c 4.36±0.07a 4.22±0.08ab 3.94±0.08abc 3.87±0.03bc 3.91±0.07bc 0.03
Jejunum 7.60±0.05c 8.43±0.09ab 8.68±0.12a 8.12±0.11abc 7.63±0.09c 7.78±0.07bc 0.01
Ileum 6.13±0.10 6.67±0.10 6.52±0.11 6.26±0.11 5.93±0.08 5.85±0.08 0.20
Colon 1.21±0.02 1.24±0.03 1.31±0.03 1.22±0.03 1.23±0.02 1.14±0.04 0.76
Rectum 2.63±0.05 2.66±0.07 2.80±0.08 2.61±0.05 2.62±0.05 2.62±0.06 0.92
Total intestine 22.20±0.16 23.32±0.33 23.26±0.42 23.57±0.38 22.01±0.25 21.71±0.22 0.26
Open in a new tab

a,b,c Means within rows with different superscript letters are significantly different (P < 0.05), whereas values with no letters or the same superscript letters are not significantly different (P > 0.05). Data are presented as the mean and pooled SEM.

Chemical composition

Dietary Trp levels from 0.145% to 0.235% significantly decreased the percentage of liver fat in 28-day-old geese, whereas those from 0.280% to 0.370% showed a gradual increase (P < 0.05) (Table 7). The percentage of liver protein gradually increased and was the highest in the 0.325% group; however, this difference was not significant (P > 0.05). Dietary Trp levels from 0.145% to 0.235% enhanced the protein content in the brisket muscle. However, further increase in Trp supplementation significantly decreased the percentage of protein in the brisket muscle (P < 0.01). The percentages of liver and thigh muscle proteins were not altered significantly by the increasing the levels of Trp supplementation.

Table 7.  Chemical compositions of the liver and the brisket and thigh muscles of 28-day-old Sichuan white geese.

Item (%) Group P value
0.145% 0.190% 0.235% 0.280% 0.325% 0.370%
Liver fat 5.27±0.26ab 3.80±0.14b 3.67±0.11b 4.09±0.18ab 4.92±0.21ab 5.76±0.34a 0.05
Liver protein 20.46±0.13 20.71±0.13 20.81±0.09 20.81±0.14 21.36±0.17 20.30±0.11 0.27
Brisket protein 15.94±0.09c 16.35±0.08c 17.18±0.07a 16.51±0.11bc 16.97±0.06ab 16.24±0.07c <0.01
Thigh muscle protein 20.68±0.09 20.50±0.02 20.27±0.07 20.52±0.04 20.32±0.05 20.25±0.10 0.48
Open in a new tab

a,b,c Means within rows with different superscript letters differ significantly (P < 0.05), whereas values with no letters or the same superscript letters did not differ significantly (P > 0.05). Data are presented as the mean and pooled SEM.

DISCUSSION

In waterfowl, Trp is an indispensable amino acid and must be supplied in the diet. The present results showed that ADFI and ADG in 1–28-day-old goslings increased significantly in the 0.190% Trp group and then started decreasing up to the 0.370 group (P < 0.05). There were no significant differences in the F/G ratios among the six groups. A similar trend was observed in previous studies, wherein supplementation with moderate levels of Trp (0.22%, 0.23%) at the 28–70-day stage improved ADFI and ADG in geese, whereas that with excess levels of Trp (0.30%, 0.31%) downregulated both parameters (Wei et al., 2011; Pan et al., 2013). Results from previous studies and those from the current study suggest that optimal dietary Trp levels in geese could increase their growth performance at different growth stages. The results of our non-linear regression analysis, based on ADG and ADFI, showed that the highest ADG and ADFI values were achieved in the 0.190% Trp group.

Although the feed efficiency in some birds, such as turkeys, is not affected by dietary supplementation with Trp, other poultry and mammals show obvious changes in feed intake after Trp supplementation (Denbow et al., 1993; Corzo et al., 2005; Wang et al., 2012). This improvement in growth performance was largely attributed to the enhanced appetite and increased feed intake induced by Trp and/or its metabolites. Serotonin, an important neuromediator, may play an important role in regulating increased feed intake (Le Floc’h and Seve, 2007; Le Floc’h et al., 2011). Thus, our results suggest that an optimum level of Trp in the diet of geese stimulates their appetite. However, further studies are required to support this hypothesis.

Serum TP content can be influenced by dietary nutrient levels or amino acid balance and tends to increase when animals were fed nutrient-rich diets (Choi et al., 2005). In our study, TP and albumin concentrations in 1–28-day-old geese increased significantly with increasing levels of Trp supplementation and were highest in the 0.325% group (P < 0.05). Some studies have shown that the plasma TP content in 22–70-day-old Yangzhou geese was significantly affected by dietary Trp levels, without any changes in serum albumin (Pan et al., 2013). This difference in serum albumin concentrations in the two studies may be because of the dietary supplementation carried out at different growth stages in geese. Trp has been shown to bind mainly to the albumin in the blood and plasma of animals (Salter et al., 1989; Pardridge and Fierer, 1990; Chanut et al., 1992; Badawy, 2018). This may explain the significant increase in plasma albumin levels after Trp supplementation in the present study (P < 0.05).

Our results suggest that Trp promotes the relative weights of the proximal intestine, particularly the duodenum and jejunum; however, the mechanism requires further investigation. Studies have shown that Trp activates mammalian rapamycin complex 1 and increases the mRNA levels of amino acid transporters (e.g., SLC6A19, SLC6A14, and ATP1A1) (Wang et al., 2015; Wang et al., 2022). Moreover, dietary Trp increases the abundance of tight junction proteins, ZO-1, ZO-3, and claudin-1, in the jejunum and duodenum (Liang et al., 2018). Trp also regulates the proliferation of intestinal epithelial cells, protects the integrity of intestinal epithelial cells in vivo, and reduces intestinal permeability (Liu et al., 2017). These results suggest that dietary Trp protects intestinal epithelial cell integrity and improves intestinal epithelial cell protein synthesis, which in turn increases the relative weight of the duodenum and jejunum in geese. However, further mechanisms related to increase in relative weight of the intestines have yet to be elucidated.

Although several studies on geese have focused on their nutrient requirements during the growing stage, few have focused on the balance of amino acids in the diet during the starting period (Wei et al., 2011; Pan et al., 2013; Li et al., 2022). Optimal nutrient supplementation during the starting period is considered crucial for attaining the desired growth rate in the whole stage and the final marketing weight. Based on our results, we propose that 0.183%–0.190% dietary Trp levels may be appropriate for 1–28-day-old Sichuan white goslings to enhance growth performance, and a 0.235% Trp level would be beneficial for intestinal development and brisket protein deposition. Thus, our study provides basic evidence and guidance regarding the optimal levels of Trp supplementation required in Sichuan white geese.

ACKNOWLEDGMENTS

The authors would like to thank all the partners who participated in the experiment. This study was sponsored by the National Science Fund Project of China (32072751), Guangdong Province Natural Science Funds for Distinguished Young Scholars (2022B1515020016), National Key Research Program (2021YFD1300404), National Science Fund for Outstanding Young Scholars (32222080), Natural Science Foundation of Guangdong Province (2019B1515210012), China Agriculture Research System (CARS-42-15), and Modern Agricultural Industrial Technology System Innovation Team of Guangdong Province (2021KJ137).

*These authors contributed equally to this article.

Footnotes

Authors’ Contributions: Fu Yang, Liu Bo, and Yang Lin designed this study; Fu Yang, Lei Hui, and Lin Zhenping acquired the data and performed the experiments; Lin Zhenping, Zhu Yongwen, and Chen Junpeng conducted animal experiments; Wang Wence, Zhu Yongwen, and Ye Hui performed data analysis; and Fu Yang, Wang Wence, Yang Lin, and Bo Liu wrote the manuscript. All authors have read and approved the manuscript.

Conflicts of Interest: The authors declare no conflict of interest.

REFERENCES

  1. Badawy AAB. Targeting tryptophan availability to tumors: the answer to immune escape? Immunology and Cell Biology, 96: 1026–1034. 2018. 10.1111/imcb.12168 [DOI] [PubMed] [Google Scholar]
  2. Chanut E,Zinit R,Trouvin JH,Riant P,Tillement JP andJacquot C. Albumin binding and brain uptake of 6-fluoro-DL-tryptophan: competition with L-tryptophan. Biochemical Pharmacology, 44: 2082–2085. 1992. 10.1016/0006-2952(92)90112-V [DOI] [PubMed] [Google Scholar]
  3. Choi HK,Liu S andCurhan G. Intake of purine-rich foods, protein, and dairy products and relationship to serum levels of uric acid: The Third National Health and Nutrition Examination Survey. Arthritis and Rheumatism, 52: 283–289. 2005. 10.1002/art.20761 [DOI] [PubMed] [Google Scholar]
  4. Corzo A,Moran ET Jr.,Hoehler D andLemmell A. Dietary tryptophan need of broiler males from forty-two to fifty-six days of age. Poultry Science, 84: 226–231. 2005. 10.1093/ps/84.2.226 [DOI] [PubMed] [Google Scholar]
  5. Denbow DM,Hobbs FC,Hulet RM,Graham PP andPotter LM. Supplemental dietary L‐tryptophan effects on growth, meat quality, and brain catecholamine and indoleamine concentrations in Turkeys. British Poultry Science, 34: 715–724. 1993. 10.1080/00071669308417630 [DOI] [PubMed] [Google Scholar]
  6. Eder K,Peganova S andKluge H. Studies on the tryptophan requirement of piglets. Archiv fur Tierernahrung, 55: 281–297. 2001. 10.1080/17450390109386198 [DOI] [PubMed] [Google Scholar]
  7. Fatufe AA,Hirche F andRodehutscord M. Estimates of individual factors of the tryptophan requirement based on protein and tryptophan accretion responses to increasing tryptophan supply in broiler chickens 8 – 21 days of age. Archives of Animal Nutrition, 59: 181–190. 2005. 10.1080/17450390500147925 [DOI] [PubMed] [Google Scholar]
  8. Fouad AM,El-Senousey HK,Ruan D,Wang S,Xia W andZheng C. Tryptophan in poultry nutrition: Impacts and mechanisms of action. Journal of Animal Physiology and Animal Nutrition, 105: 1146–1153. 2021. 10.1111/jpn.13515 [DOI] [PubMed] [Google Scholar]
  9. Kwon WB,Soto JA andStein HH. Effects of dietary leucine and tryptophan on serotonin metabolism and growth performance of growing pigs. Journal of Animal Science, 100: skab356. 2022. 10.1093/jas/skab356 [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Le Floc’h N,Otten W andMerlot E. Tryptophan metabolism, from nutrition to potential therapeutic applications. Amino Acids, 41: 1195–1205. 2011. 10.1007/s00726-010-0752-7 [DOI] [PubMed] [Google Scholar]
  11. Le Floc’h N. andSeve B. Biological roles of tryptophan and its metabolism: Potential implications for pig feeding. Livestock Science, 112: 23–32. 2007. 10.1016/j.livsci.2007.07.002 [DOI] [Google Scholar]
  12. Li Q,Chen M andPeng X. Effects of dietary crude protein and metabolizable energy levels on performance and nitrogen balance of Sichuan white geese aged from 4 to 8 weeks. Chinese Journal of Animal Nutrition, 27: 67–75. 2015. [Google Scholar]
  13. Li Y,Xia D,Chen J,Zhang X,Wang H,Huang L,Shen J,Wang S,Feng Y,He D,Wang J,Ye H,Zhu Y,Yang L andWang W. Dietary fibers with different viscosity regulate lipid metabolism via ampk pathway: roles of gut microbiota and short-chain fatty acid. Poultry Science, 101: 101742. 2022. 10.1016/j.psj.2022.101742 [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Liang H,Dai Z,Kou J,Sun K,Chen J,Yang Y,Wu G andWu Z. Dietary L-tryptophan supplementation enhances the intestinal mucosal barrier function in weaned piglets: implication of tryptophan-metabolizing microbiota. International Journal of Molecular Sciences, 20: 20. 2018. 10.3390/ijms20010020 [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Liu BY,Wang ZY,Yang HM,Wang JM,Xu D,Zhang R andWang Q. Influence of rearing system on growth performance, carcass traits, and meat quality of Yangzhou geese. Poultry Science, 90: 653–659. 2011. 10.3382/ps.2009-00591 [DOI] [PubMed] [Google Scholar]
  16. Liu W,Mi S,Ruan Z,Li J,Shu X,Yao K,Jiang M andDeng Z. Dietary tryptophan enhanced the expression of tight junction protein ZO-1 in intestine. Journal of Food Science, 82: 562–567. 2017. 10.1111/1750-3841.13603 [DOI] [PubMed] [Google Scholar]
  17. Pan X,Wei Z,Wang H,Yu L andLiang X. Effects of dietary tryptophan on protein metabolism and related gene expression in Yangzhou goslings under different feeding regimens. Poultry Science, 92: 3196–3204. 2013. 10.3382/ps.2012-02953 [DOI] [PubMed] [Google Scholar]
  18. Pardridge WM. andFierer G. Transport of tryptophan into brain from the circulating, albumin-bound pool in rats and in rabbits. Journal of Neurochemistry, 54: 971–976. 1990. 10.1111/j.1471-4159.1990.tb02345.x [DOI] [PubMed] [Google Scholar]
  19. Salter M,Knowles RG andPogson CI. How does displacement of albumin-bound tryptophan cause sustained increases in the free tryptophan concentration in plasma and 5-hydroxytryptamine synthesis in brain? Biochemical Journal, 262: 365–368. 1989. 10.1042/bj2620365 [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Scott GN,DuHadaway J,Pigott E,Ridge N,Prendergast GC,Muller AJ andMandik-Nayak L. The immunoregulatory enzyme IDO paradoxically drives B cell-mediated autoimmunity. Journal of Immunology (Baltimore, Md.: 1950), 182: 7509–7517. 2009. 10.4049/jimmunol.0804328 [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Wang B,Jiang L,Wu Z andDai Z. L-tryptophan differentially regulated glucose and amino acid transporters in the small intestine of rat challenged with lipopolysaccharide. Animals (Basel), 12: 3045. 2022. 10.3390/ani12213045 [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Wang H,Ji Y,Wu G,Sun K,Sun Y,Li W,Wang B,He B,Zhang Q,Dai Z andWu Z. L-tryptophan activates mammalian target of rapamycin and enhances expression of tight junction proteins in intestinal porcine epithelial cells. Journal of Nutrition, 145: 1156–1162. 2015. 10.3945/jn.114.209817 [DOI] [PubMed] [Google Scholar]
  23. Wang S,Khondowe P,Chen S,Yu J,Shu G,Zhu X,Wang L,Gao P,Xi Q,Zhang Y andJiang Q. Effects of “Bioactive” amino acids leucine, glutamate, arginine and tryptophan on feed intake and mRNA expression of relative neuropeptides in broiler chicks. Journal of Animal Science and Biotechnology, 3: 27. 2012. 10.1186/2049-1891-3-27 [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Wei ZY,Wang L,Ji Y,Yu LH,Pan XH,Wang MZ andWang HR. Effects of dietary tryptophan supplementation and feed restriction on growth performance and carcass characteristics of goslings. Journal of Animal and Veterinary Advances, 10: 2079–2083. 2011. 10.3923/javaa.2011.2079.2083 [DOI] [Google Scholar]
  25. Wensley MR,Woodworth JC,Derouchey JM,Dritz SS,Tokach MD,Goodband RD,Walters HG,Leopold BA,Coufal CD,Haydon KD andLee JT. Effects of amino acid biomass or feed-grade amino acids on growth performance of growing swine and poultry. Translational Animal Science, 4: 49–58. 2020. 10.1093/tas/txz163 [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Wolf AM,Wolf D,Rumpold H,Moschen AR,Kaser A,Obrist P,Fuchs D,Brandacher G,Winkler C,Geboes K,Rutgeerts P andTilg H. Overexpression of indoleamine 2,3-dioxygenase in human inflammatory bowel disease. Clinical Immunology (Orlando, Fla.), 113: 47–55. 2004. 10.1016/j.clim.2004.05.004 [DOI] [PubMed] [Google Scholar]
  27. Yan X,Xu Y,Zhen Z,Li J,Zheng H,Li S,Hu Q andYe P. Slaughter performance of the main goose breeds raised commercially in China and nutritional value of the meats of the goose breeds: a systematic review. Journal of the Science of Food and Agriculture, 2022. 10.1002/jsfa.12244 [DOI] [PubMed] [Google Scholar]
  28. Zheng M,Dong MJ,Kang B,He H andMa R. Study on ENO1 characteristic and its developmental expression profiling in tissues of HPG axis of Sichuan white goose. Huabei Nongxuebao, 29: 93–97. 2014. [Google Scholar]
  29. Zhou X,Gao Q,Yang F,Jiang S,Xiao R andLuo M. Effect of dietary methionine (Met) levels on growth performances, blood metabolic indexes for 6 ~ 10 week old Sichuan white geese. Journal of Southwest China Normal University, 37: 90–93. 2013. [Google Scholar]

Articles from The Journal of Poultry Science are provided here courtesy of Japan Poultry Science Association

RESOURCES