Histidine Requirement Research Articles

Nutrient and bioactive compounds from Neltuma spp. seeds

AbstractIn the search for compounds with nutritional and functional value, seeds from several Neltuma species were examined for lipid, protein and phenolic components. Lipid contents ranged between 9.3 and 12.5 g/100 g (seed dry weight), and showed both oleic and linoleic acids predominating largely. Lipids were also a good source of tocopherols (170–603 mg total tocopherols/kg). Proteins accounted for 14.7–35.5 g/100 g seed. Essential amino acids (EAA) comprised 26.1%–40.2% of the total AA content. Based on the EAA score, proteins from all the species analyzed were deficient in leucine, isoleucine and valine, but could meet requirements for histidine, threonine, phenylalanine, tyrosine, and lysine. The qualitative patterns of phenolic compounds were similar each other (predominance of flavonoids, particularly apigenin derivatives). Keeping in mind the examined chemical components, Neltuma seeds have potential value as a source of healthy macronutrients and bioactive compounds.

Effects of dietary histidine level on growth, antioxidant capacity and TOR signaling pathway in juvenile swimming crabs, Portunus trituberculatus

An eight-week feeding trial was conducted to determine the optimal dietary histidine requirement of juvenile swimming crab (Portunus trituberculatus). Six isonitrogenous and isolipidic diets (45.0% crude protein and 8.0% crude lipid) were formulated to contain 0.43%, 0.68%, 0.97%, 1.24%, 1.45% and 1.79% histidine, respectively. Each diet was randomly assigned to triplicate groups of 30 juvenile crabs (approximately initial weight 17.63 ± 0.08 g). The results indicated that the highest percent weight gain (PWG) and specific growth rate (SGR) was presented in crabs fed the diet with 1.24% histidine (P < 0.05). Crabs fed the diet with 1.45% histidine showed remarkably higher activities of alanine transaminase (ALT) and aspartate transaminase (AST) in hemolymph than those fed the other diets (P < 0.05). Meanwhile, the concentrations of malondialdehyde (MDA) in hemolymph and hepatopancreas remarkably decreased with dietary histidine levels increasing from 0.43% to 1.79%, and activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC) and hydroxyl radical scavenging activity in hemolymph and hepatopancreas exhibited the significant trend of first increasing to 1.17% histidine and then decreasing (P < 0.05). The concentrations of carnosine significantly increased with the increase of dietary histidine levels (P < 0.05). Moreover, dietary histidine levels could significantly influence the mRNA levels of genes related to TOR pathway such as tor, akt, s6k1, s6, eif4e1a, eif4e2 and eif4e3, and antioxidant such as cat, cMnsod, gpx, trx and prx (P < 0.05). Two slope broken-line model analysis of PWG against the dietary histidine levels indicated that the optimal dietary histidine requirement was estimated to be 1.17% of the dry matter (2.60% of the dietary protein) for juvenile swimming crab. In conclusion, dietary 1.24% histidine can significantly increase the carnosine contents in muscle, hepatopancreas and hemolymph, improve antioxidant performance and activate the TOR signaling pathway.

Histidine requirement of snubnose silver pompano Trachinotus blochii

Histidine is necessary for the formation and repair of tissues to mitigate the effects of cataract on some fish species. Although the requirements for dietary amino acids of several Trachinotus species have been reported, the quantitative histidine requirement for a cost-effective diet for snubnose pompano or Trachinotus blochii, a high value finfish species in the Philippines, has been limited. A 90-day growth experiment determined the dietary histidine requirement of juvenile snubnose pompano (0.19 ± 0.03 g). Six isonitrogenous, isolipidic, and isoenergetic diets consisted of a control diet with 0% histidine inclusion level (basal histidine level of 0.65%) and five diets with histidine inclusion levels of 0.15 (0.80%), 0.3 (1.1%), 0.45 (1.55%), 0.6 (2.15%), and 0.75% (2.9%). To simulate the pompano whole-body amino acid composition, essential amino acids were added in the diet. Fifteen pompano juveniles per tank in three replicates were stocked randomly in 250-L fiberglass tanks and were fed to satiation for 90 d. When the dietary histidine level and percent weight gain were analyzed via quadratic regression, a dietary histidine level of 1.61 g per 100 g diet or 0.357 g per 100 g protein is required for juvenile snubnose pompano. Moreover, the occurrence of cataracts was not observed in fish fed all dietary treatments.

Histidine Deficiency Inhibits Intestinal Antioxidant Capacity and Induces Intestinal Endoplasmic-Reticulum Stress, Inflammatory Response, Apoptosis, and Necroptosis in Largemouth Bass (Micropterus salmoides).

This 56-day study aimed to evaluate the effects of histidine levels on intestinal antioxidant capacity and endoplasmic-reticulum stress (ERS) in largemouth bass (Micropterus salmoides). The initial weights of the largemouth bass were (12.33 ± 0.01) g. They were fed six graded levels of histidine: 0.71% (deficient group), 0.89%, 1.08%, 1.26%, 1.48%, and 1.67%. The results showed that histidine deficiency significantly suppressed the intestinal antioxidant enzyme activities, including SOD, CAT, GPx, and intestinal level of GSH, which was supported by significantly higher levels of intestinal MDA. Moreover, histidine deficiency significantly lowered the mRNA level of nrf2 and upregulated the mRNA level of keap1, which further lowered the mRNA levels of the downstream genes sod, cat, and gpx. Additionally, histidine-deficiency-induced intestinal ERS, which was characterized by activating the PEPK-signalling pathway and IRE1-signalling pathway, including increased core gene expression of pepk, grp78, eif2α, atf4, chopα, ire1, xbp1, traf2, ask1, and jnk1. Dietary histidine deficiency also induced apoptosis and necroptosis in the intestine by upregulating the expressions of proapoptotic genes, including caspase 3, caspase 8, caspase 9, and bax, and necroptosis-related genes, including mlkl and ripk3, while also lowering the mRNA level of the antiapoptotic gene bcl-2. Furthermore, histidine deficiency activated the NF-κB-signalling pathway to induce an inflammatory response, improving the mRNA levels of the proinflammatory factors tnf-α, hepcidin 1, cox2, cd80, and cd83 and lowering the mRNA levels of the anti-inflammatory factors tgf-β1 and ikbα. Similarly, dietary histidine deficiency significantly lowered the intestinal levels of the anti-inflammatory factors TGF-β and IL-10 and upregulated the intestinal levels of the proinflammatory factor TNF-α, showing a trend similar to the gene expression of inflammatory factors. However, dietary histidine deficiency inhibited only the level of C3, and no significant effects were observed for IgM, IgG, HSP70, or IFN-γ. Based on the MDA and T-SOD results, the appropriate dietary histidine requirements of juvenile largemouth bass were 1.32% of the diet (2.81% dietary protein) and 1.47% of the diet (3.13% dietary protein), respectively, as determined by quadratic regression analysis.

Dietary Histidine Supplementation Maintained Amino Acid Homeostasis and Reduced Hepatic Lipid Accumulation of Juvenile Largemouth Bass, Micropterus Salmoides.

This 56-day research aimed to evaluate the recommended histidine requirement and the influence of dietary histidine levels on the protein and lipid metabolism of juvenile largemouth bass (Mieropterus salmoides). The initial weight of the largemouth bass was 12.33 ± 0.01 g, which was fed with six graded levels of histidine. The results showed that appropriate dietary histidine had a positive effect on growth, with a higher specific growth rate, final weight, weight gain rate, protein efficiency rate, and a lower feed conversion rate and feed intake rate being observed in 1.08-1.48% dietary histidine groups. Furthermore, the mRNA levels of GH, IGF-1, TOR, and S6 showed an increasing trend first and then declined, similar to the trend of the growth and protein content of the whole body composition. Meanwhile, dietary histidine levels could be sensed by the AAR signaling pathway, representing as downregulation of core genes of AAR signaling pathway with the increased dietary histidine levels, including GCN2, eIF2α, CHOP, ATF4, and REDD1. In addition, increased dietary histidine levels decreased the lipid content of the whole body and the liver by upregulating the mRNA levels of core genes of the PPARα signaling pathways, including PPARα, CPT1, L-FABP, and PGC1α. However, increased dietary histidine levels downregulated the mRNA levels of core genes of the PPARγ signaling pathways such as PPARγ, FAS, ACC, SREBP1, and ELOVL2. These findings were also supported by the positive area ratio of hepatic oil red O staining and the TC content of plasma. According to the specific growth rate and feed conversion rate, the recommended histidine requirement of juvenile largemouth bass was 1.26% of the diet (2.68% of dietary protein) by regression lines calculated using a quadratic model. In general, histidine supplementation promoted protein synthesis and lipid decomposition and reduced lipid synthesis by activating the TOR, AAR, PPARα, and PPARγ signaling pathways, which provided a new perspective to solve the fatty liver problem of largemouth bass by nutritional means.

Dietary histidine requirement for fingerlings of Channa punctatus (Bloch)

To estimate the requirement of fingerling Channa punctatus (6.34 ± 0.08 g) for dietary histidine, the present study was conducted by feeding six isoproteic (450 g kg−1 CP) and isoenergetic (14.73 kJ g−1 DE) diets with six histidine levels (2.5, 5, 7.5, 10, 12.5 and 15 g kg−1 diet). The trial diets were fed for 12 weeks in a triplicate group of fish at 08:00, 12:30, and 17:30 h to apparent satiation. Absolute weight gain (AWG; 49.1 g fish−1), daily growth index (DGI, 2.34%), feed conversion ratio (FCR, 1.42), protein retention efficiency (PRE; 28.12), and histidine retention efficiency (HRE; 29.69%) improved significantly with increasing histidine from 2.5 to 12.5 g kg−1 diet. Dietary histidine concentrations considerably affected carcass protein, lipid, and moisture contents. Increment in hematocrit (Hct), hemoglobin (Hb), and red blood cell counts (RBCs) were noted with increasing histidine up to 12.5 g kg−1 after that decreased. In contrast, erythrocyte sedimentation rate (ESR) and erythrocyte osmotic fragility (EOF) showed a reverse pattern. Total Serum protein, superoxide dismutase (SOD), and catalase (CAT) activities responded positively up to 12.5 g kg−1 dietary histidine, whereas malondialdehyde (MDA) aspartate aminotransferase (AST) and alanine aminotransferase (ALT) significantly declined up to 12.5 g kg−1 of dietary histidine. Second-order regression of AWG, FCR, PRE, and HRE against different histidine concentrations showed the requirements at 12.2, 11.7, 12.3, and 11.2 g kg−1, respectively. Dietary inclusion of 12.5 g kg−1 histidine is recommended for fingerling C. punctatus for optimum growth, hematological parameters, and antioxidant activities.

The digestible histidine requirement of juvenile yellowtail kingfish Seriola lalandi

The Essential Amino Acid (EAA) requirements of many cultured species remains unknown and therefore aquafeeds used in new industries are often based on the requirements of similar species or those from a similar trophic level. One such example is the formulation of aquafeeds for Australian Yellowtail Kingfish Seriola lalandi (YTK), which are historically based on the published EAA requirements of Japanese Yellowtail Seriola quinqueradiata. The requirements of YTK for sulphur-amino acids as well as taurine have recently been quantified. These studies indicated that cultured YTK may have different EAA requirements to Japanese Yellowtail which has raised doubts about the adequacy of other EAAs in commercial feeds for YTK. Of these, the adequacy of histidine was considered particularly important due to concerns about cataract formation and poor growth. Therefore, the digestible histidine requirement of YTK was quantified using a dose-response design that employed a fishmeal-free basal diet containing 0.61% digestible histidine. Supplemental crystalline L-histidine was added to the basal formulation in 0.5% increments resulting in four additional diets with a digestible histidine content of 0.96, 1.32, 1.61 and 2.0%, respectively. Each dietary treatment was assigned to triplicate saltwater tanks containing 10 × 80 g YTK which were fed to apparent satiation for seven weeks at a temperature of 20 °C. Despite the incremental addition of histidine there were no differences in growth rate, feed intake, condition factor and feed conversion ratio of YTK in response to dietary treatment. In contrast, evaluation of whole carcass revealed histidine deposition rate increased in response to digestible histidine content before declining at the highest dietary level (i.e. >1.61%), suggesting YTK had reached their maximum rate of histidine deposition under our experimental conditions. A factorial analysis of the retention data from the current study was compared to and combined with previous factorial models on histidine utilisation by YTK. The combined model indicated that while the maintenance demand for histidine varied with experimental conditions, the unit cost of histidine deposition in YTK was constant at 1.99. A conservative estimate of the variable digestible histidine requirement for maintenance at temperatures between 15 and 24 °C was found to be 64.2 mg kgBW-0.7d−1. Feed ration models generated from the factorial data sets indicate YTK should be fed diets that contain between 1.6 and 2.0% digestible histidine in order to meet their daily histidine requirement. These amounts are slightly higher than generally recommended for Japanese Yellowtail.

Seasonality as experienced in the market and the resulting variation in the amino acid and elemental composition of chub mackerel (Scomber colias)

Chub mackerel (Scomber colias) is an underutilised fish species, abundant in the Atlantic Ocean. Its amino acid profile and elemental composition are still insufficiently studied. Accordingly, these aspects were studied on a monthly basis. The most abundant essential amino acids, lysine and leucine, had contents ranging from 1270 ± 40 mg/100 g in August to 1820 ± 96 mg/100 g in November and from 1210 ± 36 mg/100 g in August to 1570 ± 20 mg/100 g in March, respectively. The other essential amino acids’ contents varied between 500 and 1200 mg/100 g. Essential amino acids represented between 41.9 % and 44.6 % of all amino acids. As a result of high histidine content in S. colias, three weekly meals (160 g/meal) guarantee all human histidine requirements. Regarding elemental composition, K was the most abundant, varying its content between 331 ± 3 mg/100 g and 499 ± 4 mg/100 g. The other studied elements’ order of abundance was P > Na > Mg > Ca > Fe > Zn. Under optimal conditions, consumption of a 160 g daily meal of S. colias may provide at most 20 % of the Fe and 30 % of the Zn requirements. Therefore, though not an outstanding Fe and Zn source, S. colias can give a significant contribution to these elements’ requirements.

De novo histidine biosynthesis protects Mycobacterium tuberculosis from host IFN-\u03b3 mediated histidine starvation

Intracellular pathogens including Mycobacterium tuberculosis (Mtb) have evolved with strategies to uptake amino acids from host cells to fulfil their metabolic requirements. However, Mtb also possesses de novo biosynthesis pathways for all the amino acids. This raises a pertinent question- how does Mtb meet its histidine requirements within an in vivo infection setting? Here, we present a mechanism in which the host, by up-regulating its histidine catabolizing enzymes through interferon gamma (IFN-γ) mediated signalling, exerts an immune response directed at starving the bacillus of intracellular free histidine. However, the wild-type Mtb evades this host immune response by biosynthesizing histidine de novo, whereas a histidine auxotroph fails to multiply. Notably, in an IFN-γ−/− mouse model, the auxotroph exhibits a similar extent of virulence as that of the wild-type. The results augment the current understanding of host-Mtb interactions and highlight the essentiality of Mtb histidine biosynthesis for its pathogenesis.

Histidine requirement of rainbow trout ( Oncorhynchus mykiss ) fed a low fishmeal‐based diet for maximum growth and protein retention

A two-phase feeding trial was conducted to estimate the dietary histidine requirement of juvenile and post-juvenile rainbow trout for maximum growth and protein retention. Twelve isonitrogenous experimental diets were formulated where diet 1 was an 8% fishmeal basal diet having 0.5% histidine. Histidine was added to diets 2–6 to achieve levels of 0.7, 0.9, 1.1, 1.3 and 1.5% histidine respectively. Diets 7–12 were identical to diets 1–6 except for pellet size. In trial 1, fish (4 g) were fed test diets 1–6, and in trial 2, fish (40 g) were fed diets 7–12, to four replicate tanks per diet for 12 weeks. A nutrient digestibility trial was also conducted with trout from trial 2. Growth performance and feed utilization were not significantly influenced by dietary histidine supplementation above the basal diet level in either rainbow trout juveniles or post-juveniles. Supplementation of histidine significantly increased protein and histidine digestibility, and it was lowest in the basal diet group. The highest histidine retention was in the lowest dietary histidine treatment group, and histidine retention progressively decreased at each increase in dietary histidine. In post-juvenile trout, the same pattern was observed except that for the two lowest histidine levels, retention was similar and high. Finally, considering the overall growth and nutrient retention performances, the dietary histidine requirement is relatively higher in post-juvenile trout (>0.6%) rather than juvenile trout (0.6%) under the present experimental conditions.

Histidine: A Systematic Review on Metabolism and Physiological Effects in Human and Different Animal Species.

Histidine is an essential amino acid (EAA) in mammals, fish, and poultry. We aim to give an overview of the metabolism and physiological effects of histidine in humans and different animal species through a systematic review following the guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). In humans, dietary histidine may be associated with factors that improve metabolic syndrome and has an effect on ion absorption. In rats, histidine supplementation increases food intake. It also provides neuroprotection at an early stage and could protect against epileptic seizures. In chickens, histidine is particularly important as a limiting factor for carnosine synthesis, which has strong anti-oxidant effects. In fish, dietary histidine may be one of the most important factors in preventing cataracts. In ruminants, histidine is a limiting factor for milk protein synthesis and could be the first limiting AA for growth. In excess, histidine supplementation can be responsible for eating and memory disorders in humans and can induce growth retardation and metabolic dysfunction in most species. To conclude, the requirements for histidine, like for other EAA, have been derived from growth and AA composition in tissues and also have specific metabolic roles depending on species and dietary levels.

Dietary histidine requirement of grow-out Nile tilapia (Oreochromis niloticus), based on growth performance, muscle development, expression of muscle-growth-related genes, and blood parameters

ABSTRACT This research was conducted to determine optimal dietary histidine requirement of grow-out Nile tilapia, Oreochromis niloticus, based on muscle development, expression of muscle-growth-related genes, and blood parameters. Fish (n = 288, initial body weight of 64.17±0.53 g) were fed extruded diets with graded levels of histidine (4.23, 5.44, 7.17, 8.91, and 11.57 g kg−1), containing approximately 289 g kg−1 crude protein and 3565 kcal kg−1 digestible energy. The study followed a completely randomized design with five treatments and four [...]

MIG1 as a positive regulator for the histidine biosynthesis pathway and as a global regulator in thermotolerant yeast Kluyveromyces marxianus

Kmmig1 as a disrupted mutant of MIG1 encoding a regulator for glucose repression in Kluyveromyces marxianus exhibits a histidine-auxotrophic phenotype. Genome-wide expression analysis revealed that only HIS4 in seven HIS genes for histidine biosynthesis was down-regulated in Kmmig1. Consistently, introduction of HIS4 into Kmmig1 suppressed the requirement of histidine. Considering the fact that His4 catalyzes four of ten steps in histidine biosynthesis, K. marxianus has evolved a novel and effective regulation mechanism via Mig1 for the control of histidine biosynthesis. Moreover, RNA-Seq analysis revealed that there were more than 1,000 differentially expressed genes in Kmmig1, suggesting that Mig1 is directly or indirectly involved in the regulation of their expression as a global regulator.

Safety of Graded-doses of Histidine in Healthy Adults (P08-062-19)

ObjectivesHistidine is an essential amino acid found in the diet through protein-rich foods. Previous research demonstrated benefits of histidine due to anti-inflammatory, anti-oxidant, and glucoregulatory properties. To date, histidine requirement for adults has not be established; current expert opinion for histidine is 8 and 12 mg/(kg body weight × day), an estimate that was extrapolated from the infant requirement for histidine. Further, the clinical safety of histidine supplementation above the average dietary intake has not been determined. Objective: To determine the safety of graded-doses of histidine in a healthy adult population. MethodsOur preliminary study includes 30 adults (n = 12 males and n = 18 females, aged 21–50 y). Following the completion and review of a health history questionnaire, vitals, and a biochemical panel, participants were deemed healthy and able to participate. After baseline measures were obtained, participants consumed encapsulated histidine pills daily for four weeks followed by a three-week washout period between each dose. Participants consumed one of three doses (4 g, 8 g, and 12 g) of histidine during each of the four-week supplement periods. A complete biochemical panel was run at baseline, week 2 and 4 of supplement, as well as washout. Anthropometric, body composition, sleep patterns, dietary intake, and urine samples were also collected throughout the study (analyses underway). ResultsBaseline descriptive statistics are as follows for females [males]: body weight 65 ± 0.55 kg [62.91 ± 3.17 kg], systolic pressure 113 ± .54 mmHg [125 ± 2.93 mmHg], diastolic pressure 70 ±.48 mmHg [74 ± 3.22 mmHg], and heart rate 74 ± 0.56 bpm [63 ±3.17 bpm]. There were no observed differences between baseline and measurements taken at any of the three doses for body weight, systolic blood pressure, diastolic blood pressure, and heart rate. There was no effect of histidine dose on the biochemical measures of aspartarte amino transferase (U/L, P = 0.096), alanine amino transferase (U/L, P = 0.47), creatinine (mg/dL, P = 0.79), glucose (mg/dL, P = 0.06), insulin (μIU/ml, P = 0.48), or c-reactive protein (mg/L, P = 0.19). ConclusionsIn our current analyses, we observe no deleterious effects of taking up to 12 grams of histidine in healthy young adults. Funding SourcesInternational Council on Amino Acid Science.

Dietary histidine requirement and physiological effects of dietary histidine deficiency in juvenile red drum Sciaenop ocellatus

In order to develop nutritious and cost-effective diets, the amino acid requirements of cultured fish species must be quantified. Several indispensable amino acid requirements of red drum Sciaenops ocellatus have already been reported; however, its requirement for histidine (His) has yet to be quantified. The aims of the present studies were to determine the minimum dietary His requirement of juvenile red drum and the physiological effects of His deficiency. A basal diet was prepared using lyophilized red drum muscle as an intact protein (10.5% of dietary protein) supplemented with crystalline amino acids (excluding His) to provide a total of 35% crude protein (CP) in the diet. Five isonitrogenous and isoenergetic experimental diets were prepared by supplementing the basal diet (0.3g His/100g dry diet) with increasing amounts of His (0.5, 0.7, 0.9, 1.1, 1.3g/100g dry diet). These diets were fed to triplicate tanks of juvenile red drum (initial average weight of 0.98±0.08g/fish) for 6weeks in feeding trial 1 to quantify the minimum dietary His requirement. His level had significant effects on relative weight gain, feed efficiency ratio, protein efficiency ratio, and plasma free His. According to quadratic broken-line regression on relative weight gain percentage, the dietary His requirement was 0.59 (±0.15) g/100g dry diet (1.6% of CP). Feeding trial 2 was performed to further examine His deficiency in red drum. In that trial, the basal diet and a His-supplemented diet (~1.2g/100g dry diet) were fed to juvenile red drum (initial average weight of 1.53±0.08g/fish) in triplicate tanks for 8weeks. Cataracts were found in 16.7% of eyes from fish fed the basal diet while no fish in the supplemented group developed cataracts. His-supplemented fish were found to have higher erythrocyte fragility than those fed the basal diet. Based on these results, the His requirement of red drum was defined and His deficiency was observed to affect blood parameters and increase the possibility of cataract development.

Dietary histidine requirement of Nile tilapia juveniles based on growth performance, expression of muscle-growth-related genes and haematological responses

A 100-day feeding trial was carried out to determine the dietary histidine requirement of Nile tilapia juveniles based on growth performance, muscle development, expression of muscle-growth-related genes, biochemical and hematological responses. Nile tilapia juveniles (4.84±0.04g) were fed six extruded practical isonitrogenous (265.7g of crude protein kg−1) and isoenergetic (17.3MJ of gross energy kg−1) diets containing graded levels of histidine (4.2, 5.4, 7.1, 8.9, 9.8 and 11.5gkg−1 dry diet). The feeding trial was conducted in a flow-through system (1.5Lmin−1) at 28°C water temperature, and triplicate groups of fish were hand-fed each diet four times a day until apparent satiation. Final weight, weight gain, feed conversion ratio, protein efficiency ratio and net protein utilization were optimized in fish fed 8.9g of histidine kg−1. Whole-body protein content was enhanced in fish fed 7.1 and 9.8g of histidine kg−1 compared to fish fed 11.5g of histidine kg−1. Active hypertrophic growth process was observed in fish fed 8.9g of histidine kg−1, as confirmed by lower frequency of occurrence of muscle fibers <20µm diameter and higher frequency of occurrence of muscle fibers >50 µm diameter, compared to fish fed 5.4g of histidine kg−1. Fish fed 9.8g of histidine kg−1 showed the highest expression level of MyoD. However, myogenin expression was higher in fish fed 9.8 and 11.5g of histidine kg−1 compared to fish fed 4.2 to 7.1g of histidine kg−1. Myostatin expression was similar among fish from all treatments. Biochemical and haematological responses were not affected in fish fed graded levels of histidine. Based on second-order regression analysis, the dietary histidine requirement for maximum WG of Nile tilapia juveniles was estimated to be 8.2gkg−1, corresponding to 3.1% of crude protein. Statement of RelevanceHistidine is a limiting amino acid in Nile tilapia diets.

Estimation of the leucine and histidine requirements for piglets fed a low-protein diet

Reduction of the CP content in the diets of piglets requires supplementation with crystalline essential amino acids (AA). Data on the leucine (Leu) and histidine (His) requirements of young pigs fed low-CP diets are limited and have primarily been obtained from nonlinear models. However, these models do not consider the possible decline in appetite and growth that can occur when pigs are fed excessive amounts of AA such as Leu. Therefore, two dose-response studies were conducted to estimate the standardised ileal digestible (SID) Leu: lysine (Lys) and His: Lys required to optimise the growth performance of young pigs. In both studies, the average daily gain (ADG), average daily feed intake (ADFI) and gain-to-feed ratio (G: F) were determined during a 6-week period. To ensure that the diets had sub-limiting Lys levels, a preliminary Lys dose-response study was conducted. In the Leu study, 60 35-day-old piglets of both sexes were randomly assigned to one of five treatments and fed a low-CP diet (15%) with SID Leu: Lys levels of 83%, 94%, 104%, 115% or 125%. The His study used 120 31-day-old piglets of both sexes, which were allotted to one of five treatments and fed a low-CP diet (14%) with SID His: Lys levels of 22%, 26%, 30%, 34% or 38%. Linear broken-line, curvilinear-plateau and quadratic-function models were used for estimations of SID Leu: Lys and SID His: Lys. The minimum SID Leu: Lys level needed to maximise ADG, ADFI and G: F was, on average, 101% based on the linear broken-line and curvilinear-plateau models. Using the quadratic-function model, the minimum SID Leu: Lys level needed to maximise ADG, ADFI and G: F was 108%. Data obtained from the quadratic-function analysis further showed that a ±10% deviation from the identified Leu requirement was accompanied by a small decline in the ADG (−3%). The minimum SID His: Lys level needed to maximise ADG, ADFI and G: F was 27% and 28% using the linear broken-line and curvilinear-plateau models, respectively, and 33% using the quadratic-function model. The preferred model to estimate the His requirement was the curvilinear-plateau model. However, a 10% reduction in the SID His: Lys level was associated with an 11% reduction in the ADG. In conclusion, the SID Leu: Lys level needed to maximise growth was 108% when using the quadratic-function model as the best-fitting model. The minimum SID His: Lys level required to optimise growth was 28% when using the curvilinear-plateau model as the best-fitting model.

Effects of graded levels of histidine on growth performance, digested enzymes activities, erythrocyte osmotic fragility and hypoxia-tolerance of juvenile grass carp Ctenopharyngodon idella

A 10-week experiment was conducted to estimate the effects of graded levels of histidine on growth performance, digested enzymes activities, erythrocyte osmotic fragility and hypoxia-tolerance of juvenile grass carp Ctenopharyngodon idella. Six isonitrogenous (38%) and isoenergetic semi-purified diets containing casein and gelatin with graded levels of histidine (0.45, 0.72, 1.02, 1.28, 1.55, 1.78g100g−1DM) were formulated. Each diet was assigned to triplicate groups of 30 fish (3.68±0.01) for each tank. The highest weight gain (WG, %), final body weight (FBW, g) and specific growth rate (SGR) were recorded when histidine level was 1.02% of the diet. Whole body protein and muscle protein were not significantly affected by the histidine level (P>0.05). Muscle histidine content was linearly increased along with the dietary histidine increasing (P<0.05). Fish fed histidine deficient diet (0.45g100g−1) exhibited highest erythrocyte osmotic fragility (P<0.05). Meanwhile, the shortest survival time and lowest catalase (CAT) activity and total antioxidant capacity were also recorded in fish fed histidine deficient diet (P<0.05). Second-degree polynomial regression analysis of final body weight data indicated that the minimum recommended dietary histidine requirement for grass carp was 1.21% of the diet, corresponding to 3.2% of dietary protein. Statement of relevanceThe present study determined optimum dietary histidine requirement for juvenile grass carp and the data goes to 1.21% of the diet, corresponding to 3.2% of dietary protein. We also found that juvenile grass carp fed with histidine deficiency diet not only limited their growth performance, but also exhibited higher erythrocyte osmotic fragility, lower hypoxia-tolerance and antioxidant enzyme activities. Digested enzyme activities were also significantly affected by the dietary histidine levels. Thus, it is important to meet histidine requirement when commercial diets are formulated for this species.

Antimutagenic activity of major fractions of Zataria multiflora Boiss by Ames method

Zataria multiflora is a medicinal plant that has been interested in antimutagenicity effect because of its high antioxidant activity and richness of flavonoids. Antimutagenicity effect of total extract of the plant has been reported previously. Aerial parts of Z. multiflora were extracted by petroleum ether, chloroform and 80% methanol by liquid‐liquid extraction method consequently. The fractions were concentrated in vacuum and dried at 40°C in oven. The genotype of two standard strains of Salmonella typhimurium (TA98, TA100) was confirmed by the evaluation of two important factors of histidine requirement and the presence of R factor. The minimum inhibition concentration (MIC) of the fractions against these two strains was determined by agar dilution method. From each fraction, various concentrations less than MIC were studied for anti‐mutagenic test. The sample along with bacterial strain and mutagen agent were incubated at 37°C for 48 h. The number of revertant colonies was counted and compared with control plates. Our results showed that all fractions especially petroleum ether and chloroform ones maintain the number of colonies in the standard range in control plates and prevent from the growth of many strains of bacteria and increase of revertant colonies enhancement in a concentration‐dependent manner. This effect was prominent against TA100 starin. Methanolic fraction exhibited anti‐mutagen activity just in the highest used concentration in the presence of TA98. Key words: Ames test, anti‐mutagenicity, fraction, phenylpropanoids, Salmonella typhimurium, Zataria multiflora

Antimutagenic activity of major fractions of Zataria multiflora Boiss by Ames method

Zataria multiflora is a medicinal plant that has been interested in antimutagenicity effect because of its high antioxidant activity and richness of flavonoids. Antimutagenicity effect of total extract of the plant has been reported previously. Aerial parts of Z. multiflora were extracted by petroleum ether, chloroform and 80% methanol by liquid‐liquid extraction method consequently. The fractions were concentrated in vacuum and dried at 40°C in oven. The genotype of two standard strains of Salmonella typhimurium (TA98, TA100) was confirmed by the evaluation of two important factors of histidine requirement and the presence of R factor. The minimum inhibition concentration (MIC) of the fractions against these two strains was determined by agar dilution method. From each fraction, various concentrations less than MIC were studied for anti‐mutagenic test. The sample along with bacterial strain and mutagen agent were incubated at 37°C for 48 h. The number of revertant colonies was counted and compared with control plates. Our results showed that all fractions especially petroleum ether and chloroform ones maintain the number of colonies in the standard range in control plates and prevent from the growth of many strains of bacteria and increase of revertant colonies enhancement in a concentration‐dependent manner. This effect was prominent against TA100 starin. Methanolic fraction exhibited anti‐mutagen activity just in the highest used concentration in the presence of TA98. Key words: Ames test, anti‐mutagenicity, fraction, phenylpropanoids, Salmonella typhimurium, Zataria multiflora