Trp Supplementation Research Articles

Dietary tryptophan modulates intestinal immune response, barrier function, antioxidant status and gene expression of TOR and Nrf2 in young grass carp (Ctenopharyngodon idella)

The present research evaluated the effects of dietary tryptophan (Trp) on growth performance, intestinal mucosal immune, barrier function and antioxidant capacity and gene expression of young grass carp (Ctenopharyngodon idella). Fish were fed six different experimental diets containing graded levels of Trp at 0.7(control), 1.7, 3.1, 4.0, 5.2 and 6.1 g kg−1 diet for 8 weeks. The results showed that Trp supplementation significantly enhanced the percent weight gain (PWG), feed intake and feed efficiency (P < 0.05), and decreased the plasma ammonia content (PAC) (P < 0.05). After the 8-week feeding trail, an environmental copper exposure trail was conducted for 4 days. Results from the copper exposure trail showed that dietary Trp enhanced the lysozyme, acid phosphatase activities and complement 3 contents in the intestine of young grass carp (P < 0.05). In addition, Trp supplementation increased the copper/zinc superoxide dismutase (SOD1), glutathione peroxidase (GPx) activities and glutathione contents (P < 0.05), and decreased the protein carbonyl and malondialdehyde contents (P < 0.05). Furthermore, the relative gene expression levels of interleukin 10, transforming growth factor-β1, occludin, zonula occludens 1, claudin-b, -c, and −3, SOD1, GPx and NF-E2-related factor 2 in the intestine were significantly up-regulated with increasing of dietary Trp up to a certain level (P < 0.05). Conversely, the mRNA levels of tumor necrosis factor α, interleukin 8, target of rapamycin, Kelch-like-ECH-associated protein 1, claudin-12 and -15a in the intestine were significantly down-regulated by Trp (P < 0.05). Collectively, appropriate dietary Trp level improves fish growth, intestinal immune response, barrier function and antioxidant status, and regulated the mRNA levels of related signal molecules of young grass carp. Based on the quadratic regression analysis of the PWG and PAC, the dietary Trp requirement of young grass carp (287–699 g) was estimated to be 3.81 g kg−1 diet (12.7 g kg−1 protein) and 3.89 g kg−1 diet (13.0 g kg−1 protein), respectively.

Melatonin and Dopamine as Biomarkers to Optimize Treatment in Phenylketonuria: Effects of Tryptophan and Tyrosine Supplementation

To determine whether additional supplementation of tryptophan (Trp) and tyrosine (Tyr) improve serotonin and dopamine metabolism in individuals with phenylketonuria treated with large neutral amino acid (LNAA) tablets. Ten adult individuals with phenylketonuria participated in a randomized, double-blind, placebo-controlled cross-over study consisting of three 3-week phases: washout, treatment with LNAA tablets plus supplementation with either Trp and Tyr tablets or placebo, and LNAA tablets plus the alternate supplementation. An overnight protocol to measure blood melatonin, a serotonin metabolite in the pinealocytes, and urine 6-sulfatoxymelatonin and dopamine in first-void urine specimens was conducted after each phase. Serum melatonin and urine 6-sulfatoxymelatonin and dopamine levels were increased in the LNAA phase (LNAA plus placebo) compared with the washout phase. Serum melatonin and urine 6-sulfatoxymelatonin were not increased in the active phase (LNAA plus Trp + Tyr) compared with the LNAA phase, although plasma Trp:LNAA was increased compared with the LNAA phase. Among 7 subjects with a plasma Trp/LNAA >0.03, a negative correlation between urine 6-sulfatoxymelatonin and plasma phenylalanine levels was observed (r = -0.072). Urine dopamine levels and plasma Tyr:LNAA were increased in the active phase compared with the LNAA phase. Melatonin levels were not increased with the higher dose of Trp supplementation, but dopamine levels were increased with the higher dose of Tyr supplementation. Serotonin synthesis appears to be suppressed by high phenylalanine levels at the Trp hydroxylase level.

Effects of niacin status on tryptophan requirements of starter white Pekin ducks

A 4×5 factorial experiment, using 4 supplemental nicotinamide levels (0, 40, 80, and 120mg/kg) and 5 dietary Trp levels (1.32, 1.67, 2.02, 2.37, and 2.72g/kg), was conducted to study the effects of niacin status on Trp requirements for growth of starter white Pekin ducks from hatch to 3wk 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 40mg 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<0.001). Supplementation of Trp in diets alleviated the depression of weight gain and feed intake caused by niacin deficiency at 0mg 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 (1.32gTrp/kg). According to the broken-line regression, the Trp requirements of starter Pekin ducks for weight gain from hatch to 3wk of age at 0, 40, 80, and 120mg/kg of supplemental nicotinamide were 2.42, 1.68, 1.69, and 1.69g/kg, respectively, and the Trp requirement was much greater at 0mg/kg of supplemental nicotinamide than at other 3 supplemental nicotinamide levels (P<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.

Short- and long-term effects of dietary l-tryptophan supplementation on the neuroendocrine stress response in seawater-reared Atlantic salmon (Salmo salar)

The essential amino acid l-tryptophan (Trp) is the immediate precursor of the neurotransmitter serotonin (5-HT). Supplementing Trp through diet has been shown to suppress the neuroendocrine stress response in vertebrates including teleosts. In salmonid fish, adjusting to the social environment as well as habituation to seawater involves the neuroendocrine stress response, suggesting that such environmental factors may modulate the stress-reducing effects of Trp. To date, studies that have investigated the neuroendocrine effects of dietary Trp have only been conducted in rainbow trout (Oncorhynchus mykiss), a salmonid species, under conditions featuring social isolation in the freshwater environment. Here, we address the effects of dietary Trp on post-stress plasma cortisol and hypothalamic monoamines in seawater-adapted Atlantic salmon (Salmo salar), reared at densities relevant for aquaculture. Fish were given feed containing 1, 2, 3 or 4 times the Trp content in normal feed for one week. Subsequently, the fish were reintroduced to feed containing the lowest Trp level, corresponding to standard commercial feed for a number of days prior to exposure to an acute confinement stressor. Basal plasma cortisol levels were lower among non-stressed fish at 1 and 10days post dietary Trp supplementation. By comparison, stressed fish displayed stimulatory post-stress plasma cortisol responses at 1 and 2days after the Trp regimen was terminated. However, a reversed pattern was observed among these fish at 10days after Trp treatment. The overall effects of dietary Trp were more pronounced in dopamine (DA) neurochemistry compared to 5-HT in the hypothalamus. The results demonstrate both short- and long-term effects of elevated dietary Trp on the neuroendocrine stress response. These findings suggest that hypothalamic DA may be more involved than 5-HT in the stress reducing effects of Trp in seawater-adapted Atlantic salmon, reared at densities relevant for aquaculture.

Branched-chain amino acids alter neurobehavioral function in rats

Recently, we have described a strong association of branched-chain amino acids (BCAA) and aromatic amino acids (AAA) with obesity and insulin resistance. In the current study, we have investigated the potential impact of BCAA on behavioral functions. We demonstrate that supplementation of either a high-sucrose or a high-fat diet with BCAA induces anxiety-like behavior in rats compared with control groups fed on unsupplemented diets. These behavioral changes are associated with a significant decrease in the concentration of tryptophan (Trp) in brain tissues and a consequent decrease in serotonin but no difference in indices of serotonin synaptic function. The anxiety-like behaviors and decreased levels of Trp in the brain of BCAA-fed rats were reversed by supplementation of Trp in the drinking water but not by administration of fluoxetine, a selective serotonin reuptake inhibitor, suggesting that the behavioral changes are independent of the serotonergic pathway of Trp metabolism. Instead, BCAA supplementation lowers the brain levels of another Trp-derived metabolite, kynurenic acid, and these levels are normalized by Trp supplementation. We conclude that supplementation of high-energy diets with BCAA causes neurobehavioral impairment. Since BCAA are elevated spontaneously in human obesity, our studies suggest a potential mechanism for explaining the strong association of obesity and mood disorders.

Effects and Side Effects Associated with the Non-Nutritional Use of Tryptophan by Humans1–3

The daily nutritional requirement for ʟ-tryptophan (Trp) is modest (5 mg/kg). However, many adults choose to consume much more, up to 4–5 g/d (60–70 mg/kg), typically to improve mood or sleep. Ingesting ʟ-Trp raises brain tryptophan levels and stimulates its conversion to serotonin in neurons, which is thought to mediate its actions. Are there side effects from Trp supplementation? Some consider drowsiness a side effect, but not those who use it to improve sleep. Though the literature is thin, occasional side effects, seen mainly at higher doses (70–200 mg/kg), include tremor, nausea, and dizziness, and may occur when Trp is taken alone or with a drug that enhances serotonin function (e.g., antidepressants). In rare cases, the “serotonin syndrome” occurs, the result of too much serotonin stimulation when Trp is combined with serotonin drugs. Symptoms include delirium, myoclonus, hyperthermia, and coma. In 1989 a new syndrome appeared, dubbed eosinophilia myalgia syndrome (EMS), and was quickly linked to supplemental Trp use. Key symptoms included debilitating myalgia (muscle pain) and a high peripheral eosinophil count. The cause was shown not to be Trp but a contaminant in certain production batches. This is not surprising, because side effects long associated with Trp use were not those associated with the EMS. Over 5 decades, Trp has been taken as a supplement and as an adjunct to medications with occasional modest, short-lived side effects. Still, the database is small and largely anecdotal. A thorough, dose-related assessment of side effects remains to be conducted.

Physiological responses of dietary tryptophan fedLabeo rohitato temperature and salinity stress

Two experiments were conducted to elucidate the possible effects of dietary L-tryptophan (TRP) in Labeo rohita based on growth performance and physio-biochemical responses. In the experiment I, a 60-day feeding trial was carried out to elucidate the effects of dietary TRP enrichment on growth performance and physio-biochemical responses. In the experiment II, the TRP pre-fed L.rohita, from experiment I, was exposed to temperature and salinity stress to evaluate stress-mitigating efficacy of TRP. In L.rohita, dietary supplementation of TRP showed significant effect on weight gain percentage and feed conversion ratio but not on blood glucose. A significant increase in RNA content and RNA/DNA ratio upon TRP supplementation was observed and was positively correlated with growth performance. The results of experiment II indicated that weight gain percentage, serum T3 and T4 levels were significantly reduced in groups that were exposed to temperature and salinity stress and fed diets without TRP supplementation. However, dietary supplementation of TRP significantly augmented weight gain percentage in stress-exposed groups. Tryptophan supplementation helped in bringing back T3 and T4 levels comparable with control. A significant increase in superoxide dismutase, catalase, Adenosine triphosphatase, blood glucose and serum cortisol was observed in temperature- and salinity-exposed groups fed without TRP-supplemented diets. However, TRP supplementation was found to be effective in restoring the above parameters. The results of these experiments suggest that dietary TRP supplementation augments growth, lowers energy demand and helps in mitigating thermal and salinity stress in L.rohita.

Changes in regional brain monoaminergic activity and temporary down-regulation in stress response from dietary supplementation withl-tryptophan in Atlantic cod (Gadus morhua)

The brain monoamines serotonin (5-hydroxytryptamine; 5-HT) and dopamine (DA) both play an integrative role in behavioural and neuroendocrine responses to challenges, and comparative models suggest common mechanisms for dietary modulation of transmission by these signal substances in vertebrates. Previous studies in teleosts demonstrate that 7 d of dietary administration with L-tryptophan (Trp), the direct precursor of 5-HT, suppresses the endocrine stress response. The present study investigated how long the suppressive effects of a Trp-enriched feed regimen, at doses corresponding to two, three or four times the Trp levels in commercial feed, last in juvenile Atlantic cod (Gadus morhua) when the fish are reintroduced to a diet with standard amino acid composition. We also wanted to determine whether Trp supplementation induced changes in brain monoaminergic neurochemistry in those forebrain structures innervated by DA and 5-HTergic neurons, by measuring regional activity of DA and 5-HT in the lateral pallial regions (Dl) of the telencephalon and nucleus lateralis tuberis (NLT) of the hypothalamus. Dietary Trp resulted in a dose-dependent suppression in plasma cortisol among fish exposed to confinement stress on the first day following experimental diet; however, such an effect was not observed at 2 or 6 d after Trp treatment. Feeding the fish with moderate Trp doses also evoked a general increase in DA and 5-HT-ergic activity, suggesting that these neural circuits within the NLT and Dl may be indirectly involved in regulating the acute stress response.

Nursery Culture of Grouper (Epinephelus fuscoguttatus Forsskal) and Sea Bass (Lates calcarifer Bloch) in Brackish Water Ponds: Co-Feeding of Zooplankton and Formulated Diets Containing L-Tryptophan

This study compared co-feeding zooplankton (ZP, mixed copepods and mysids) and formulated diets (FD) supplemented with L-tryptophan (TRP) on the survival and growth of grouper and sea bass fry nursed in brackish water ponds. Grouper (84 fry m−3) and sea bass (150 fry m−3) were reared for 30 days and 60 days, respectively, in net cages within two separate 743 m2 nursery ponds. Five treatments (with three replicates each) were compared (P < 0.05): FD-1 = ZP + basal FD (no added TRP, but containing 0.29% endogenous TRP); FD-2 = ZP + (FD 0.58% TRP); FD-3 = ZP + (FD 1.22% TRP); FD-4 = ZP + (FD 2.50% TRP); and FD-5 = minced fish (Sardinella sp.) + basal FD (no additional TRP). TRP supplementation in grouper diets produced no significant affect on growth but increased survival at rates of 0.58% and above. TRP supplementation at 2.5% (FD-4) produced significantly better sea bass growth than other diets but had no affect on survival. Zooplankton improved both survival and growth in both grouper and sea bass juveniles compared to the minced fish diet, and may be a practical and lower cost alternative to indoor nursing.

Effects of tryptophan supplementation on cashmere fiber characteristics, serum tryptophan, and related hormone concentrations in cashmere goats

This study was designed to investigate the effects of tryptophan (Trp) supplementation on cashmere fiber characteristics and on serum Trp, melatonin (MEL), prolactin (PRL), insulin-like growth factor 1 (IGF-1), triiodothyronine (T3), and thyroxine (T4) concentrations in cashmere goats during the cashmere fast-growth period. Thirty-six Liaoning cashmere wether goats were stratified on the basis of body weight (28 ± 0.8 kg) and assigned randomly to 1 of the following 4 rumen-protected Trp treatments: 0, 2.0, 4.0, and 6.0 g per goat per day. The experimental period lasted 137 d. Blood samples were collected monthly during the daytime (8:00 AM) and at night (8:00 PM). Tryptophan supplementation improved cashmere growth rates, cashmere weight, and body weight (P = 0.001) and increased serum Trp levels, nighttime MEL concentrations, IGF-1, and T3 and T4 concentrations (P < 0.05). Across the treatments and sampling months, a highly positive correlation between cashmere growth rate and nighttime serum MEL concentrations was observed (r = 0.879, P = 0.001). A moderately negative correlation between cashmere growth rates and serum PRL concentrations during the day and at night (rday = –0.645, P = 0.007; rnight = –0.583, P = 0.018) was observed. A moderately positive correlation between the cashmere growth rate and the daytime serum IGF-1 concentration (r = 0.536, P = 0.032) was observed, and no correlation was found between the cashmere growth rate and the other serum hormone concentrations. These data indicate that changes in serum concentrations of MEL, IGF-1, and PRL are related to cashmere growth in Liaoning cashmere goats during the cashmere fast-growth period. Under the experimental conditions of the current trial, we suggest that Trp may promote cashmere growth by increasing daytime IGF-1 and nighttime MEL secretion.

Dietary l-tryptophan alters aggression in juvenile matrinxã Brycon amazonicus

This study evaluated the effect of dietary supplementation with L: -tryptophan (L-TRP), a serotonin precursor, on the aggressiveness of juvenile matrinxã Brycon amazonicus. Fish were kept in individual aquaria for 7days receiving the diets: D1 (control: 0.47% of TRP), D2 (0.94% of TRP), D3 (1.88% of TRP), and D4 (3.76% of TRP). After this, they were grouped with an intruder fish to establish a resident-intruder relationship during periods of 20min. Blood cortisol, glucose, chloride, sodium and calcium; hemoglobin, hematocrit, red blood cell count and volume; liver glycogen and lipids were measured. Territoriality had significant effect on the aggressiveness of matrinxã (the residents were more aggressive than intruders, P<0.001) and tryptophan significantly affected their behavior. Fish fed with the D2 diet presented a longer latency until the first attack (P=0.0069) and bit the intruder fewer times (P=0.0136) during the period of observation, compared to the control group. The frequency of bites and chases after the first attack was not affected by the dietary supplementation of TRP. Physiological variables were not significantly affected by the diet, except for a moderate increase in cortisol level in fish fed with D2 diet after the fight, indicating slight activation of the hypothalamus-pituitary-interrenal axis. The results show that juvenile matrinxã have aggressive and territorial behavior and that a diet containing 9.4g TRPkg(-1) alter their aggressiveness, without affecting the stress-related physiological parameters.

Interaction between dietary tryptophan and pyridoxine on tryptophan metabolism, immune responses and growth performance in post-weaning pigs

Several aspects of tryptophan (Trp) metabolism are dependent upon pyridoxine (B 6) status. The present experiment aimed to determine if Trp metabolism and the eventual growth responses to dietary supplementation of Trp is modulated by dietary B 6. Exploratory measurements related to the modulation of the immune system were also made. Piglets weaned at 15 to 18 days of age ( n = 544) were grouped in 32 pens of 17 animals and distributed in a factorial arrangement of treatments with two dietary additions of B 6 [0 (B 6−) or 5 mg/kg (B 6+)] and two dietary additions of synthetic Trp [0 (Trp−) or 0.5 g/kg (Trp+)]. Basal dietary concentrations of B 6 varied according to age, between 2.1 and 3.5 mg/kg, and for Trp, between 1.9 and 2.5 g/kg. Growth performance was recorded every week from 2 to 9 weeks of age. Blood samples were taken from two piglets in each pen at 2, 4, 6 and 8 weeks of age. Another piglet in each pen was immunized twice with ovalbumin emulsified with incomplete Freund adjuvant to evaluate the antibody response. No treatment effect was observed on feed intake, body weight gain or feed conversion ratio for the whole experimental period but feed conversion increased more drastically in Trp− than in Trp+ piglets during the last week of experiment (B 6 × Trp × age, P<0.05). Pyridoxal, an active B 6 vitamer, was 19% lower in red blood cells of B 6− than B 6+ piglets (B 6 × age, P<0.01). Plasma Trp and kynurenine (an intermediate metabolite of Trp oxidation) decreased with age (P<0.01). Plasma nicotinamide, an indicator of niacin status, increased with age and remained approximately 45% higher in Trp+ piglets than in Trp− piglets (Trp × age, P<0.01). Antibody response to ovalbumin was enhanced in Trp− piglets (Trp × age, P<0.01). The lymphocyte proliferative response to Concavalin A was lower (P<0.05) in B 6+ than in B 6− piglets. The percentage of B lymphocyte population at 4 and 6 weeks of age dropped in B 6− animals whereas it remained stable in B 6+ piglets (B 6 × age, P<0.05). In spite of late and short changes of feed conversion ratio (interaction B 6 × Trp × age), the results indicate that, globally, within the present dietary levels, pyridoxine is not a major factor for Trp metabolism and therefore, for Trp requirements of post-weaning piglets. The absence of interaction between B 6 and Trp on the present immunological indicators suggest that each nutrient modulates the immune response through independent mechanisms.

Effects of tryptophan supplementation on aggression among group-housed gestating sows1

The objective of this study was to determine the effects of dietary Trp supplementation on mixing-induced aggression and the associated stress, and on reproductive performance in gestating sows. After weaning, sows were mixed in pens with electronic sow feeders on concrete-slatted floors. Each pen housed 21 ± 2.8 sows, with approximately 2.7 ± 0.43 m(2)/sow of floor space allowance. Multiparous sows (n = 168) from 8 breeding groups were used, with 4 groups assigned to a control diet and 4 groups assigned to a high-Trp diet. Control sows received corn- and soybean meal-based diets throughout gestation (0.15% Trp) and lactation (0.21% Trp). Three days before and after mixing, sows assigned to the high-Trp treatment received approximately 2.3 times the dietary Trp (0.35% in the gestation diet and 0.48% in the lactation diet) fed to control sows. Six focal sows (2 sows from each of parity 1, 2, and 3 or greater) in each pen were designated and videotaped for 72 h after mixing to determine the type and number of aggressive interactions among sows. Before and 48 h after mixing, saliva samples were collected from focal sows, and scratches were assessed on all sows. Data were analyzed using the FREQ and GLIMMIX procedures (SAS Inst. Inc., Cary, NC). Aggression among sows was intense during the initial 6 h and decreased between 6 and 72 h after mixing. The initial aggression caused scratches and increased cortisol concentrations (P < 0.05). Mature sows tended to fight for longer periods (112 vs. 52 s/h per sow, SE = 23.8; P < 0.10) but had fewer scratches caused by aggression (injury score = 4.3 vs. 6.5, SE = 1.13; P < 0.01) than parity-1 sows. Supplementation of dietary Trp reduced the total duration of head-to-head knocking (P < 0.05) but did not affect other aggressive behaviors. There was no difference between dietary treatments in injury scores or saliva cortisol concentrations. Sows in the high-Trp treatment had more total piglets born (12.5 vs. 10.5 pigs/litter, SE = 0.55; P < 0.05) and more stillborn piglets (1.5 vs. 0.8 pigs/litter, SE = 0.20; P < 0.05), but had no significant change (P = 0.12) in piglets born alive (10.8 vs. 9.7 pigs/litter, SE = 0.42) compared with control sows. The results indicate that the initial aggression after mixing caused more injuries in young sows than in mature sows. Supplementation of dietary Trp at 2.3 times the control amount for a short period did not effectively reduce aggression and the associated stress in sows at mixing.

Effects of rumen-protected tryptophan on growth performance, fibre characteristics, nutrient utilization and plasma essential amino acids in Cashmere goats during the cashmere slow growth period

Tryptophan (Trp) is a limiting amino acid in growing ruminants and supplementation of Trp in a rumen-protected form may have positive effects on performance in ruminants. Trp may affect cashmere fibre growth by regulating plasma melatonin secretion. From December to February, identified as the cashmere slow growth period, cashmere growth rate slows down and plasma melatonin secretion declines. Thus, Trp supplementation may affect cashmere fibre growth positively during this period. This study was conducted to investigate the effects of rumen-protected tryptophan (RPT) on Cashmere goats during the cashmere slow growth period. Optimal RPT supplementation level was determined. The Thirty-six Liaoning Cashmere goat wethers (41.63 ± 0.37 kg) aged 1.5-year-old were stratified by weight and randomly assigned to the following treatments: without RPT (control), low RPT (LRPT), medium RPT (MRPT) and high RPT (HRPT) at RPT levels of 0, 2.0, 4.0 and 6.0 g per goat per day, respectively. LRPT and MRPT supplementation increased average daily gain ( P < 0.05) and N retention ( P < 0.05).The length and growth rate of cashmere fibre increased both linearly ( P < 0.05) and quadratically ( P < 0.05) with increasing RPT supplementation. Plasma Trp concentration increased linearly ( P < 0.05) with increasing RPT supplementation. Conversely, RPT supplementation decreased plasma isoleucine, valine and total essential amino acid concentrations ( P < 0.05). In conclusion, RPT supplementation potentially enhanced growth performance, cashmere fibre growth and N utilization in Liaoning Cashmere goat wethers. In experimental conditions of the current trial, the optimum RPT supplementation level was 2.0 g per goat per day during the cashmere slow growth period.

Tryptophan Stimulates Immune Response in Broiler Chickens Challenged with Infectious Bursal Disease Vaccine

Infectious bursal disease is still a challenging issue by posing a serious threat to the commercial poultry industry especially due to the emergence of highly Infectious Bursal Disease Virus (IBDV). In the present study, we evaluated the immunomodulatory effects of Tryptophan (Tip) on innate, humoral and cellular immune responses in chickens challenged by oral administration of intermediate plus strain of IBD virus at 28 days of age. A corn-soybean meal based diet containing different levels of Tip (0, 0.10 and 0.20) for the starter, (0, 0.07 and 0.15) for the grower and (0, 0.05 and 0.13) for the finisher has been utilized. In a completely randomized design with three treatments of five replicates each and 10 chickens per replicate, 150 Cobb 500 male broiler chickens from 0-49 days of age were subjected to Tip diet. To measure the innate, cellular and humoral immunity indicators (interferon-alpha, interferon-gamma, immunoglobulin G, respectively) at 27, 35, 42 and 49 days of age, serum samples from each replicate of treatments were collected and subjected to ELISA. The result showed that Trp supplementation in the chickens basal diets significantly increased the serum levels of interferon-alpha at 35, 42 and 49 days of age (p<0.05), interferon-gamma at 27, 35 and 49 days of age (p<0.05) and immunoglobulin G at 27, 35, 42 and 49 days of age (p<0.05). These results strongly suggest that tryptophan plays a vital role in modulation of protective immune response against IBDV.

The effect of diet composition on tryptophan requirement of young piglets1

The aim of the study was to evaluate the requirement for Trp in relation to diet composition in piglets in the period after weaning (BW range of 9 to 24 kg). Two Trp-deficient [relative to the Dutch (CVB, 1996) and NRC (NRC, 1998) requirement values for piglets of 10 to 20 kg of BW] basal diets were formulated: one based on corn and soybean meal and a second one based on wheat, barley, soybean meal, peas, and whey powder [10.0 g/kg of apparent ileal digestible (AID) Lys; 1.4 g/kg of AID Trp; 1.5 g/kg of standardized ileal digestible (SID) Trp]. Both basal diets were supplemented with 0.3, 0.6, and 0.9 g of l-Trp per kg of diet to obtain diets with 1.7, 2.0, and 2.3 g of AID Trp per kg (1.8, 2.1, and 2.4 g of SID Trp per kg), respectively. Each of the 8 treatments was evaluated in 8 replicates (pens with 8 male or female piglets). Average daily feed intake, ADG, and G:F were measured as response criteria. Over the 28-d experimental period, ADG and G:F were greater for the treatments on the wheat/barley diet compared with those on the corn/soybean meal and were increased by the level of Trp in the diet (P < 0.05). Average daily feed intake was only increased by the level of Trp supplementation (P < 0.05). Increasing the Trp level increased ADFI for the corn/soybean meal diet up to 2.3 g of AID Trp per kg (2.4 g of SID Trp per kg) and up to 2.0 g of AID Trp per kg (2.1 g of SID Trp per kg) in the wheat/barley diet (P < 0.05). For both diet types supplementation of free l-Trp increased the G:F up to 1.7 g of AID Trp per kg (1.8 g of SID Trp per kg). Nonlinear regression analysis of the response curves for ADFI using an exponential model for estimating a requirement value for Trp (defined as the Trp level resulting in 95% of the maximum response) revealed a requirement estimate of 2.3 g of AID Trp per kg for the corn/soybean meal-based diet and 2.1 g of AID Trp per kg for the wheat/barley-based diet, equivalent to 2.4 and 2.2 g of SID Trp per kg of diet, respectively. For ADG, a requirement estimate of 2.1 g of AID Trp per kg for both types of diets was derived, equivalent to 2.2 g of SID Trp per kg of diet. The Trp requirement for young piglets seems to be greater than indicated by some commonly used recommendations and does not seem largely dependent on diet ingredient composition.

Reduced feed intake of lactating primiparous sows is associated with increased insulin resistance during the peripartum period and is not modified through supplementation with dietary tryptophan1

The aim of this experiment was to investigate whether insulin resistance is related to the dietary concentration of Trp and the ADFI of primiparous sows having similar body conditions. Twenty-four primiparous sows were catheterized on d 97 of pregnancy. Blood samples were collected during 3 tests: after the ingestion of 1.5 kg of feed (meal test), after the intravenous infusion of 0.5 g of glucose/kg of BW (glucose tolerance test), and during an euglycemic hyperinsulinemic clamp with an infusion rate of 100 ng of insulin x kg of BW(-1) x min(-1). Both tests were performed at 4 stages at approximately d 103 and 110 of pregnancy and at d 3 and 10 of lactation. Sows were fed a diet containing 0.16 or 0.26% of total Trp (suboptimal vs. slight excessive Trp supply according to recommendations for lactating sows) from d 104 of pregnancy after the first clamp until weaning. The dietary treatment did not result in differences in ADFI, BW, and backfat changes, and growth of piglets during lactation. Plasma Trp concentration was greater for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet (P < 0.05). Plasma glucose, NEFA, and urea profiles during the meal tests were not affected by the dietary treatment. At d 3 of lactation, the insulin concentration at 105 (P = 0.03) and 120 min (P = 0.04) after meal intake was less for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet. On d 10 of lactation, the glucose half life (P = 0.03) and the time needed to reach 25% of the area under the insulin curve (P = 0.04) during the tolerance test were less for the sows allocated to the slight excessive Trp diet than for the sows allocated to the suboptimal Trp diet. The glucose infusion rate during euglycemic hyperinsulinemic clamps was similar in the 2 Trp groups of sows. Irrespective of the dietary treatment, the ADFI of the sows was negatively related to the glucose half life during the glucose tolerance test and positively related to the glucose infusion rate during the clamp (P < 0.05). This relationship observed with the tests performed during early lactation was already found with the tests performed during late pregnancy (P < 0.02). Present findings indicate that a dietary Trp supply of 0.26% does not increase feed intake in lactating primiparous sows. This result indicates that the interest in a Trp supplementation during the peripartum period can be questioned. Irrespective of the dietary treatment, the reasons why sows with similar rearing conditions develop different rates of insulin resistance during pregnancy remain to be elucidated.

Effect of magnesium sulphate and l-tryptophan and genotype on the feed intake, behaviour and meat quality of pigs

Sixty-nine entire male pigs with different halothane genotype (homozygous halothane positive — nn-, n = 36; and homozygous halothane negative — NN-, n = 33) were fed with a supplementation of magnesium sulphate (Mg) and/or l-tryptophan (Trp) in the diet for 5 days before slaughter. Animals were housed individually and were submitted to stressful ante mortem conditions (mixed in the lorry according to treatments and transported 1 h on rough roads). Individual feed intake was recorded during the 5-d treatment. At the abattoir, pig behaviour was assessed in the raceway to the stunning system and during the stunning period by exposure to CO 2. Muscle pH, colour, water holding capacity, texture and cathepsin activities were determined to assess meat quality. The number of pigs with an individual feed intake lower than 2 kg/day was significantly different among diets ( P < 0.05; Control: 8.7%; Mg&Trp: 43.5%; Trp: 17.4%) and they were considered to have inadequate supplement intake. During the ante mortem period, 15.2% of pigs included in the experiment died, and this percentage decreased to 8.7% in those pigs with a feed intake > 2 kg/day, all of them from the stress-sensitive pigs (nn). In general, no differences were observed in the behaviour of pigs along the corridor leading to the stunning system and inside the CO 2 stunning system. During the stunning procedure, Trp diet showed shorter periods of muscular excitation than control and Mg&Trp diets. The combination of a stressful ante mortem treatment and Mg&Trp supplementation led to carcasses with high incidence of severe skin lesions. Different meat quality results were found when considering all pigs or considering only those with adequate supplement intake. In this later case, Trp increased pH 45 (6.15) vs Control diet (5.96) in the Longissimus thoracis (LT) muscle ( P < 0.05) and pH at 24 h (Trp: 5.59 vs C: 5.47) led to a higher incidence of dark, firm and exudative (DFD) traits in SM muscle ( P < 0.05). Genotype affected negatively all the meat quality traits. Seventy-five percent of LT and 60.0% of the SM muscles from nn pigs were classified as pale, soft and exudative (PSE), while none of the NN pigs showed these traits ( P < 0.0001). No significant differences were found between genotypes on the incidence of DFD meat. Due to the negative effects observed in the Mg&Trp group in feed intake and carcass quality, the utilization of a mixture of magnesium sulphate and tryptophan is not recommended.

A tryptophan-enriched diet improves feed intake and growth performance of susceptible weanling pigs orally challenged with Escherichia coli K881

We tested the effect of Trp addition to a standard weaning diet and oral challenge with enterotoxigenic Escherichia coli K88 (ETEC) on growth and health of piglets susceptible or nonsusceptible to the intestinal adhesion of ETEC. Sixty-four pigs weaned at 21 d of age were divided into 3 groups based on their ancestry and BW: a control group of 8 pigs fed a basal diet (B), the first challenged group of 28 pigs fed B diet (BCh), and the second challenged group of 28 pigs fed a diet with Trp (TrpCh). The Trp diet was produced by the addition of 1 g of l-Trp/kg to the basal diet. On d 5, pigs were orally challenged with 1.5 mL suspension containing 10(10) cfu ETEC/mL or placebo, and killed on d 9 or 23. Based on in vitro villus adhesion assay, the pigs (except the B group) were classified as susceptible (s(+)) or nonsusceptible (s(-)) to the intestinal ETEC adhesion. Thus, after the challenge, treatments were B, BChs(-), BChs(+), TrpChs(-), and TrpChs(+). Pigs susceptible to ETEC were 50.0% in the BChs(+) group (3 pigs lost included) and 46.4% in the TrpChs (+) group (1 pig lost included). During the first 4 d after challenge, the challenge reduced ADG (P < 0.05), and this reduction was greater in susceptible pigs (P < 0.05) than nonsusceptible ones. Tryptophan increased ADG and feed intake in susceptible pigs (P < 0.05) from challenge to d 4, but not thereafter. Tryptophan supplementation did not improve the fecal consistency and did not reduce the number of pigs positive for ETEC in feces on d 4 after the challenge. The K88-specific immunoglobulin A activity in blood serum tended to be greater in challenged pigs (P = 0.102) and was not affected by the addition of Trp. Villous height was affected by the addition of Trp and challenge in different ways, depending on the site of small intestine. The need to consider the phenotype for the adhesion of the ETEC in studies with different supply of Trp was clearly evident. When compared with practical weaning standard diets, Trp supplementation allowed susceptible pigs to partially compensate for the effects of ETEC challenge by increasing feed intake and maintaining an adequate BW growth. This is of practical importance for the formulation of diets for pigs selected for lean growth because of the presence of an association between this trait and the susceptibility to the intestinal adhesion of ETEC.

Effects of supplementing pig diets with tryptophan and acidifier on protein digestion and deposition, and on brain serotonin concentration in young pigs

The objective of the study was to find out whether feeding acidifying preparation with diets containing crystalline tryptophan (Trp) affects availability of this amino acid for protein and serotonin (5-HT) synthesis in young pigs. Two experiments were performed. Supplementation of Trp-deficient diet with 3 g/kg of acidifier (A) (mixture of phosphoric, citric and fumaric acids) did not affect the coefficients of ileal apparent digestibility (CIAD) of protein and protein-bound amino acids except CIAD of Trp which was increased from about 0.65 to 0.73. In pigs of initial body weight 16 kg, the increase of digestible dietary Trp level from 0.77 to 1.39 and 1.85 g/kg improved growth performance, nitrogen retention and utilization of nitrogen absorbed, while the increase from 0.77 to 1.39 g/kg enhanced 5-HT concentration in all six analyzed brain structures. Supplementation with A did not affect blood Trp level in animals fed on Trp-deficient diet while it decreased it considerably on diet supplemented with Trp to 1.85 g/kg. Feeding A affected 5-HT metabolism: decreased its level in five of six brain structures in pigs fed on Trp-deficient diet, changed 5-HT metabolite 5-hydroxy-indolo-3-acetic acid (5-HIAA) and 5-HIAA/5-HT ratio, and modified response of 5-HT to Trp supplementation. It is concluded that feeding A both with Trp-deficient and Trp-supplemented diets has positive net effect on growth and protein deposition in pigs while it seems to affect negatively 5-HT synthesis and, probably, accelerates its turnover. The mechanism of this action is not known, and it was not proved that it is related to destructive effect of acids on crystalline Trp.