Sulfur Amino Acid Requirement Research Articles

Effect of dietary methionine hydroxy analogue‐free acid (MHA‐FA) supplementation levels on growth performance, blood metabolites and immune responses in broiler chickens

AbstractBackgroundBroiler diets are commonly supplemented by liquid methionine hydroxy analogue‐free acid (MHA‐FA) containing as product with 88% of active substance to meet sulphur amino acid (SAA) requirements.ObjectivesTwo experiments were conducted to assess the effects of different dietary MHA‐FA levels on growth performance, blood metabolites and immune responses in broilers.MethodsIn experiments 1 and 2, 432 and 360 male broilers were fed either a basal corn–soya bean meal diet that met the energy and nutrient requirements with the exception of SAAs or the basal diet supplemented with 5 graded levels of MHA‐FA (+0.9 and +0.8 g/kg), for 1–11 and 11–24‐day ages, respectively. Chicks were vaccinated with inactivated H9N2/Newcastle disease (ND) and live‐ND on days 5 and 11, respectively.ResultsResponses in both experiments had similar tendency at corresponding dietary MHA‐FA levels. By increasing dietary MHA‐FA level, weight gain (WG), feed efficiency (FE), relative breast weight (RBW) and immunity against ND and avian influenza virus inoculation improved with quadratic trend. Blood serum triglyceride, low‐density lipoprotein, alanine aminotransferase and alkaline phosphatase concentration were affected in response to dietary MHA‐FA levels with quadratic trends. By using broken‐line regression analysis, the optimum dietary MHA‐FA levels for optimized WG, FE and RBW during 1–10‐day age were obtained at 2.20, 3.31 and 3.33 g/kg, respectively; based on MHA‐FA content of Met equivalent, the digestible SAA requirements were estimated 0.81%, 0.91% and 0.92%, respectively. Similarly, for the 11–24‐day age period, the optimum dietary MHA‐FA supplementation levels were obtained 1.79, 2.21, 2.41 and 2.53 g/kg, with the digestible SAA requirements estimated 0.75%, 0.79%, 0.80% and 0.81% for optimized WG, FE, RBW and immune responses, respectively.ConclusionsSupplemental levels of MHA‐FA that optimize performance, breast meat and immunity in broilers fed corn–soya bean meal diet, varied from 0.18% to 0.33%, correspond to age and what traits are considered for optimization.

62 Sulphur Amino Acids: Assessing Requirements and Utilization in Dogs and Cats

Abstract Methionine (Met), cyst(e)ine (Cys), homocysteine and taurine are the four sulfur-containing amino acids. Met can serve as a substrate for protein synthesis or to produce homocysteine, which can be remethylated to Met or irreversibly catabolized to Cys. Unlike dogs, cats are unable to further metabolize Cys to taurine, making the latter an indispensable amino acid for the cat. Met, on the other hand, is a dietary indispensable amino acid for all mammals with Cys having the ability to spare part of the Met requirement (total sulfur amino acid requirement; Met + Cys). The amount of Met that cannot be replaced by Cys is defined as the Met requirement (NRC, 2006). Empirical determinations of the Met requirement in adult dogs and cats are still limited and the recommendations proposed by the NRC (2006) are based on studies that used insensitive techniques for mature animals. When a more robust technique, the indicator amino acid oxidation, and more practical experimental diets were used to empirically determine the Met requirement, a greater estimate was found in adult cats (Pezzali et al., 2022) and adult Labrador Retrievers and Beagles, but not in miniature Dachshunds (Mansilla et al., 2020), compared with the current recommendations proposed by the NRC (2006) and AAFCO (2023). Harrison et al. (2020), however, found a decreased estimate for the Met requirement in adult Labrador Retrievers compared with Mansilla et al. (2020), likely due to differences in experimental design and diet composition. This discrepancy highlights the need to standardize methodologies and to investigate the effect of other dietary factors on the Met and total sulfur amino acid requirements owing to their complex metabolism. Indeed, the metabolism of sulfur amino acids may differ between dog breeds, resulting in differences in Met requirements and potentially making taurine a conditionally indispensable amino acid in some breeds under specific dietary conditions. While dietary Met is usually provided in excess in commercial diets, excess of Met may lead to hyperhomocysteinemia, which has been associated with detrimental health effects in other species. Due to the complex metabolism of sulfur amino acids and the complex matrix of pet foods, determining the ideal provision of sulfur amino acids in commercial diets to maximize animal health is a challenge. More long-term studies investigating the effect of different doses and ratios (Met:Cys) of sulfur amino acids on overall metabolism are necessary, in addition to requirement studies, to optimize the dietary delivery of sulfur amino acids in dogs and cats.

The Minimum Methionine Requirement for Adults Aged ≥60 Years Is the Same in Males and Females.

The minimum methionine requirement in the presence of excess dietary cysteine has not been determined in older adults. This study aimed to determine the minimum methionine requirement in healthy older adults using the indicator amino acid oxidation (IAAO) method. Fifteen healthy adults ≥ 60 years of age received seven methionine intakes (0 to 20 mg/kg/d) plus excess dietary cysteine (40 mg/kg/d). Oxidation of the indicator, L-[1-13C]phenylalanine (F13CO2), was used to estimate the mean minimum methionine requirement using a change-point mixed-effect model. There was no statistical difference between male and female requirement estimates, so the data were pooled to generate a mean of 5.1 mg/kg/d (Rm2 = 0.46, Rc2 = 0.77; p < 0.01; 95% CI: 3.67, 6.53 mg/kg/d). This is the first study to estimate the minimum methionine requirement in healthy older adults, which is the same between the sexes and as our lab's previous estimate in young adults. The findings are relevant considering current recommendations for increased consumption of plant foods, which will help to establish the appropriate balance of methionine and cysteine intake required to satisfy the sulphur amino acid requirements of older adults.

P07-051-23 Total Sulfur Amino Acid Requirements Are Higher in Late Gestation Compared to Early Gestation During Healthy Human Pregnancy

P07-051-23 Total Sulfur Amino Acid Requirements Are Higher in Late Gestation Compared to Early Gestation During Healthy Human Pregnancy

The dietary requirement for total sulfur amino acids in adults aged ≥60 years appears to be higher in males than in females

BackgroundThe total sulfur amino acid (TSAA) recommendation in older adults is based on data from young adults. Physiological evidence suggests that older adults have a higher requirement than young adults. ObjectivesThe objective of this study was to determine the TSAA requirement in healthy men and women aged ≥60 y. MethodsThe TSAA requirement was determined using the indicator amino acid oxidation method with L-[1-13C]phenylalanine as the indicator. At recruitment, 15 older adults (n = 7 men and n = 8 women; BMI < 30 kg/m2) were assigned to receive 7 methionine intakes (5, 10, 15, 19, 25, 35, and 40 mg/kg/d) without dietary cysteine. Intake levels were randomly assigned to each subject. Following enrollment, 2 subjects completed 2 intakes and 3 completed 3, while the remainder completed all 7. Mean TSAA requirement was determined from oxidation of L-[1-13C]phenylalanine using a mixed-effect change-point model. The 95% CI was calculated using parametric bootstrap. To test whether breakpoints were different between men and women, the overlap in the 95% CI was calculated. ResultsThe mean TSAA requirement was 26.2 (Rm2 = 0.39, Rc2 = 0.89; P < 0.001) and 17.1 mg/kg/d (Rm2 = 0.22, Rc2 = 0.79; P < 0.001) for men and women, respectively. The requirement was significantly higher in men than in women (difference in CI: 9.1 ± 8.85). ConclusionsTo our knowledge, this is the first study to determine the TSAA requirement in older adults. The requirement in older women is similar to current recommendations but is 75% higher in older men. These findings are important given recommendations for increased plant protein consumption. They will help in the assessment of diet quality and provide the basis of dietary guidelines for older adults consuming a plant-based diet.This trial was registered at clinicaltrials.gov as NCT04595188.

Revaluating the dietary methionine requirements in an improved strain of nile tilapia (Oreochromis niloticus)

It has been shown with terrestrial animals that the genetic improvement increases the nutrient requirements of the animal, which becomes more efficient in using these nutrients to achieve their higher growth potential. This study was conducted to estimate the dietary methionine requirements of different generations of the Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia at the juvenile stage (17.51 g–19.55 g initial body weight). To achieve this objective, a completely randomized 2 × 6 factorial design was applied, with the genetic background of fish (generation) as the first independent variable with two levels, the 16th and 17th generations, and the methionine content of the diet as the second independent variable, with 6 graded levels, 0.52, 0.62, 0.84, 0.94, 1.04 and 1.27% of methionine in the diets, respectively. At the end of the 42-day experiment, the interaction effect of the generation × diet was not significant (P > 0.05) for any of the response parameters studied. The genetic improvement led to 15% more growth in the 17th generation than the 16th generation of the GIFT strain of Nile tilapia, which was accompanied with better feed conversion ratio, protein productive value, and energy productive value in the former generation (P < 0.05). Whatever the generation considered, the optimum dietary methionine requirement for the growth of the improved GIFT strain of Nile tilapia was estimated in this study, using the broken-line model, between 0.75% and 0.80% of the diet (with a cysteine level of 0.50% of the diet), which is higher than 0.49% of the diet previously estimated for conventional Nile tilapia at the juvenile stage. Therefore, the genetic improvement applied to the GIFT strain of Nile tilapia likely led to a higher methionine and total sulfur amino acid requirement than the conventional strains. The results of this study support the need to update the existing nutrient requirement databases of fish, in order to ensure that diets are formulated to effectively satisfy the requirements of not only conventional, but also improved strains of fish, for the full expression of their accrued growth potential of the latter strains.

Effects of levels of methionine supplementations in forms of L- or DL-methionine on the performance, intestinal development, immune response, and antioxidant system in broilers challenged with Eimeria spp.

The study was conducted to investigate the effects of 2 isoforms of methionine on growth performance and intestinal health induced by methionine (Met) deficiency and Eimeria infection in broilers. A total of 720 one-day old male chicks (Cobb500) were randomly allocated to 10 groups in a 2×5 factorial arrangement (6 reps/group, 12 birds/cage) with diets and Eimeria challenge as the main factors. Hundred percent DL-Met, 100% L-Met, 80% DL-Met, and 80% L-Met diets were formulated to meet approximately 100 or 80% of the total sulfur amino acid (TSAA) requirement with DL-Met or L-Met as Met supplementation sources. The 60% TSAA basal diet (60% Met) was formulated without Met supplementation. At d14, the challenge groups were gavaged with mixed Eimeria spp. Growth performance was recorded on d7, 14, 20 (6-day postinfection [DPI]), and 26 (12 DPI). The gut permeability was measured on 5 and 11 DPI. Antioxidant status and gene expression of immune cytokines and tight junction proteins were measured on 6 and 12 DPI. Data were analyzed by 1-way and 2-way ANOVA before and after the challenge, respectively. Orthogonal polynomial contrasts were used for post hoc comparison. Overall, the Eimeria challenge and 60% Met diet significantly reduced growth performance, antioxidant status, and mRNA expression of tight junction genes and immune cytokines. For other Met treatments, the L-Met groups had significantly higher BWG and lower FCR than the DL-Met group from d 1 to 20. The L-Met groups had less gut permeability than the DL-Met groups on 5 DPI. Compared to the 80% Met groups, the 100% Met groups reduced gut permeability. At 6 DPI, the 80% Met groups showed higher ZO1 expression than the 100% Met groups. The challenge groups had higher Muc2 expression and GSH/GSSG compared to the nonchallenge groups, and SOD activity was lower in the L-Met groups compared to the DL-Met groups at 6 DPI. The 100% Met groups had higher GPx activity than the 80% Met groups at 12 DPI. In conclusion, during coccidiosis, the 100% Met groups had better gut integrity and antioxidant status. Met supplementation in the form of L-Met improved growth performance in the starter phase and gut permeability in the challenge phase.

Determining optimal sulfur amino acid (Met+Cys) requirements in broilers supplemented with L-Met

Determining optimal sulfur amino acid (Met+Cys) requirements in broilers supplemented with L-Met

The Total Sulphur Amino Acid Requirement Is Higher in Older Men Than Women

ObjectivesThe primary aim of this study was to determine the total sulphur amino acid (TSAA) requirement of adults > 60 years, using the indicator amino acid oxidation (IAAO) method and to compare the requirement estimates between older males and females. The secondary aim was to compare the requirement estimates in older adults to the previously derived IAAO requirement in young males.MethodsFifteen healthy older adults (n = 7 male and n = 8 female participants), were randomized to receive 2 to 7 methionine intakes: 5, 10, 15, 19, 25, 35 and 40 mg. kg−1. d−1 without dietary cysteine. The TSAA requirement was determined using the IAAO method with L-[1–13C]phenylalanine as the indicator. The mean TSAA requirement was determined using two-phase linear mixed effect model, which identified a breakpoint in the F13CO2 in response to graded methionine intakes. The parametric bootstrap method was used to determine the 95% confidence interval (CI). To assess whether the breakpoints were different between older males and females or between older adults and young males the overlap in 95% CI was calculated. The null hypothesis was accepted if the interval contained zero.ResultsThe mean TSAA requirement for older males was 26.2 mg · kg−1· d−1 and 17.1 mg · kg−1· d−1 for older females. The TSAA requirement of older males is higher than older females (Difference in CI: 9.1 ± 8.85) and higher compared to young males based on our previous IAAO estimate of 12.6 mg · kg−1· d−1 (Difference in CI: 13.6 ± 5.98).ConclusionsTo our knowledge this is the first study to experimentally derive the TSAA requirement in older adults. The results can be used to assess whether the amino acid requirements of older adults can be met on a plant-based diet, especially given the current recommendations for increased plant protein consumption.Funding SourcesThis study was funded by CIHR. First author Alyssa Paoletti funded by Restracomp Scholarship provided by the Research Training Centre at SickKids Hospital.

52 Weaning Elicits a Distinct Increase in Plasma Cysteine Concentration in Pigs

Abstract Weaning is a stressful event in pigs that is associated with low and variable feed intake, poor nutrient utilization, and high feed costs. The sulfur amino acids (SAA) methionine and cysteine have key roles in pig production, but how SAA metabolism, and thus SAA requirements, is affected by weaning is poorly understood. The objective of this study was to determine weaning-induced changes in SAA metabolism. Pigs (initial BW = 7,233 ± 683 g) were either weaned at 21 d age and euthanized at 23 d age (n = 4) or remained with the sow and euthanized at 23 d age (n = 4). Weaned pigs were fasted but had free access to water. At euthanasia, blood and liver tissue were collected. Plasma amino acids and amino thiols were analyzed by HPLC following pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate and 4-fluoro-7-aminosulfonylbenzofurazan, respectively. The protein abundance of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CTH), enzymes needed for methionine transsulfuration to cysteine, in liver were determined by Western blot. Total plasma non-essential amino acid (NEAA) concentrations declined in weaned compared with unweaned pigs (2,664 versus 4,290 ± 211 µmol/L, P &amp;lt; 0.01). Among NEAA, however, only plasma cysteine concentration increased in weaned compared with unweaned pigs (total cysteine, 253 versus 173 ± 16 µmol/L, P &amp;lt; 0.05; cystine, 43 versus 23 ± 5 µmol/L, P &amp;lt; 0.05). Plasma methionine tended to be less in weaned pigs (53 versus 65 ± 4 µmol/L, P = 0.075), whereas plasma taurine was less in weaned pigs (64 versus 128 ± 10 µmol/L, P &amp;lt; 0.01). The abundance of CBS and CTH protein in liver was not different between groups. Elevated plasma cysteine concentrations after weaning in pigs is likely due to decreased cysteine oxidation to taurine rather than greater methionine transsulfuration to cysteine.

PSV-9 Effects of Supplemental Methionine Sources in Finishing Pig Diets on Carcass Characteristics, Cutting Yields, and Meat Quality

Abstract While supplemental methionine (Met) is widely used within the swine industry, data are limited regarding the effect of Met sources on carcass cutability and meat quality. The objective was to determine the effects of DL-methionine (DLM, 99%), L-methionine (LM, 99%), or calcium salt of DL-methionine hydroxyanalogue (MHA-Ca, 84%) in finishing pig diets on carcass characteristics and meat quality. Pigs (n = 240) were allocated to 60 single-sex pens. For the final 7 wk of the finisher phase, pigs (BW= 79.9 ± 0.80 kg) were fed diets containing DLM, LM, or MHA-Ca, with the supplemental methionine source providing 25% of the sulfur amino acid requirement. One pig per pen was slaughtered, and left sides of carcasses were fabricated into subprimal cuts to determine carcass-cutting yields. Loin quality including proximate composition and shear force was measured. Data were analyzed using the MIXED procedure of SAS. Hot carcass weight was not different (P= 0.34) between treatments (DLM 103.0 kg; LM 104.5 kg; MHA-Ca 101.5kg), moreover loin eye area was not different (P= 0.98) between treatments (DLM 52.49 cm²; LM 52.65 cm²; MHA-Ca 52.81 cm²). Boneless carcass cutting yield was not different (P = 0.56) between treatments (DLM 54.82 kg; LM 54.97 kg; MHA-Ca 54.52 kg). Loin pH was not different (P = 0.24) between treatments (DLM 5.48; LM 5.45; MHA-Ca 5.45). However, drip loss tended to be reduced (P = 0.11) by the DLM treatment (5.58%) compared with LM (7.03%) and MHA-Ca (6.68%) treatments. Shear force was not different (P = 0.85) between treatments (DLM 3.06 kg; LM 3.03 kg; MHA-Ca 3.10 kg). However, cook loss tended to be reduced (P = 0.06) by the DLM treatment (16.20%) compared with LM (18.18%) and MHA-Ca (18.50%) treatments. These data suggest that only minimal differences in carcass cutability and meat quality can be attributed to methionine sources in finishing pig diets.

Evaluating growth response of broiler chickens fed diets supplemented with synthetic DL-methionine or DL-hydroxy methionine: a meta-analysis

Methionine (Met) is the first limiting amino acid in corn and soybean meal-based diets (containing L-Met) in broiler chickens, which are often supplemented with synthetic DL-Met or DL-Hydroxy Met (OH-Met). Our objective was to quantitatively assess the efficacy of synthetic Met sources and determine differences in growth rate of broilers fed at or below requirements in response to Met intake. A systematic literature search resulted in building a database containing 480 treatment means from 39 articles published between 1985 and 2019 globally. The database was divided into starter, grower, and finisher subsets based on the age of the broilers. For each subset, linear-plateau and quadratic-plateau models were fitted to determine Met or sulfur amino acid (SAA; Met + Cysteine) requirements using average daily gain as a response variable. For each phase, 4 new subsets were obtained by only retaining records with digestible Met or SAA intake at or below requirement by linear-plateau or quadratic-plateau models. Then, a linear model (without plateau) was fitted for all new subsets for each rearing phase using supplemental digestible synthetic Met or SAA intake (basal Met intake was subtracted from total Met intake) as independent variables. The basal diet was made of only raw materials without supplementation of any synthetic Met source. Finally, the models were extended to evaluate source of synthetic Met effects on the slope parameter. At all stages of model fitting, the inclusion of a random study effect was evaluated for each parameter. All models were fitted within a Bayesian framework, for which minimally informative priors were used. The best models, that is, the most accurate inclusion of random effects, were selected based on at least 10-point difference in leave-one-out cross-validation information criterion. Model selection criteria did not consistently favor either of the linear- and quadratic-plateau models to determine Met or SAA requirements across broiler growth phases. Extending models with covariates (e.g., dietary energy and amino acids) did not improve any model fit. Body weight gain response of broiler chickens to the 2 sources was not different when fed at or below Met requirements for any of the growth phases.

Lysine and sulfur amino acid requirements of broiler chicks over short time periods within the starter phase

SUMMARY Six experiments were conducted to validate the hypothesis that Lys and SAA requirements decrease within the starter phase using 3-day periods from 2 to 11 d of age. In the first 3 experiments, 7 diets were generated by adding L-Lys to a lysine deficient basal diet in 0.10% increments, ranging from 0.85 to 1.45% Digestible Lys. In Experiments 4 to 6, 7 diets were generated by adding 0.07% increments of DL-methionine to a SAA deficient diet to produce diets ranging from 0.63 to 1.04% DSAA. The linear broken line estimate for digestible Lys was 1.22, 1.17 and 1.16% for BWG and 1.31, 1.21, and 1.14% for FCR in experiments 1, 2, and 3, respectively. The linear broken line estimate for DSAA was 0.82, 0.81 and 0.94% for BWG and 0.82, 0.80, and 0.90 for FCR in experiments 4, 5, and 6, respectively. These results indicated that Lys requirements decreased linearly as hypothesized, however, the SAA requirements did not follow same pattern.

Evaluating the dietary taurine requirement of hybrid striped bass, (Morone chrysops x M. saxatilis)

A dietary requirement for the sulfonic acid taurine has been documented in many marine species. However, it has not been well studied in hybrid fish with freshwater and marine genes, such as the hybrid striped bass (Morone chrysops x M. saxatilis). Therefore, an 8-week feeding trial was conducted to evaluate the effects of various levels of dietary taurine on growth performance, health, and body composition of juvenile hybrid striped bass. Four diets were formulated from practical ingredients and supplemented with DL-methionine at 0.54% of dry weight to meet the hybrid striped bass' established total sulfur amino acid requirement of 1.0% of dry diet, and taurine was supplemented incrementally at 0, 0.5, 1, and 2% of dry weight. Two additional diets were prepared without DL-methionine supplementation to be marginally deficient in methionine (0.49% by weight) and either supplemented with or without taurine at 1% dry weight to evaluate the potential interactions between methionine and taurine. Diets containing increment levels of taurine were determined to show no significant (P > .05) differences in terms of weight gain, feed efficiency (FE), whole-body composition, hepatosomatic index (HSI), intraperitoneal fat ratio (IPF ratio), or muscle yield. However, hybrid striped bass fed the methionine-deficient diets had significantly (P < .05) reduced percentage weight gain and FE as well as reduced muscle yield and HSI compared to fish fed the methionine-supplemented diets. Interestingly, taurine inclusion at 1% in the diet containing 0.49% methionine increased weight gain and feed efficiency of fish compared to those fed the diet without supplemental taurine or methionine. These results indicated that growth performance and body composition of hybrid striped bass did not respond to taurine supplementation when dietary methionine was adequate but did respond when dietary methionine was limiting.

RESPONSE TO METHIONINE SUPPLEMENTATION OF BROILER CHICKS FED PRACTICAL CORN-GROUNDNUT MEAL DIETS IN THE TROPICS

Two floor feeding trials, involving 1000 broiler chicks fed two different practical-type diets, were conducted in order to determine the methionine and total sulphur amino acid (TSAA) requirements of broiler chicks 0-6 weeks). Two protein levels (20 and 23%) each with an energy concentration of 2800 Kcal ME (kg diet and four supplemental methionine levels (0.1, 0.2, 0.3 and 0.4%) were tested. At the end of 6 - week feeding period, a common finisher ration was fed to 10 weeks of age. Under our experimental circumstances with dietshaving 23% protein and metabolizable energy of 2800 Kcal ME/kg diet and based on assumed methionine and cystine content of feeding stuff, the quantitative requirement for methionine of broiler chicks up to six weeks of age were about 0.53% diet which is equivalent to 2.3% of the dietary protein (or TSSA of 0.85 per cent diet, that is 3.7 per cent protein). Higher supplemental methionine at this protein and energy levels resulted in deterioration in liveweight gain and slight but non-significant improvement in feed/gain ratio. The rations containing 20% protein performed poorly relative to those containing 23%. Feeding of high quality common finisher rations neutralized the initial gains due to supplemental methionine within each protein levelbut did not offset the gains due to different dietary proteins.

Sulfur amino acid requirements for pullets in growth and pre-laying trials

Context To obtain a good performance of the hens in the laying phase, adequate nutrition in the growth and pre-laying phase is necessary, especially for meeting amino acid requirements that are related to development of reproductive organs (ovary and oviduct). Aims The objective of the present study was to predict the requirements for methionine (Met) plus cystine (Cys) from the growth of the body, feathers and reproductive organs of laying hens. Methods The model estimates Met+Cys requirements as the relationship between the deposition of Met+Cys into three compartments (body, feathers, and reproductive organs) and their utilisation efficiency. The efficiency of utilisation was determined by a linear regression between Met+Cys deposition and intake for pullets aged 14–28, 56–70 and 98–112 days. Protein weight and deposition in the body and feathers were determined by the comparative slaughter method. The Gompertz function was used to model body, feathers, ovary, oviduct and liver weight against age. Key results Our results showed that the inclusion of parameters descriptive of the growth of reproductive organs and the correction for feather losses in the model enabled Met+Cys requirements for growth in pre-laying trials to be predicted with a greater precision. Conclusions The model developed in this study for determining the Met+Cys requirements for Dekalb White pullets could be extended, provided the necessary adjustments are made, to other amino acids, strains and species. Implications Meeting Met+Cys requirements in the phase of maximum growth of the reproductive organs (weeks) contributes to the uniformity of the age when the pullets reach sexual maturity and, consequently, start the egg production.

The sulfur amino acid requirements of juvenile Yellowtail Kingfish (Seriola lalandi)

The dietary methionine and cysteine requirements of Yellowtail Kingfish (YTK) are unknown. Methionine, an essential sulfur-containing amino acid, acts as a sulfur and methyl donor for key metabolites, such as cysteine and taurine. Cysteine, a conditionally essential sulfur-containing amino acid, can spare significant amounts of methionine in the total sulfur amino acid (TSAA) requirement. Both methionine and cysteine are an integral part of YTK aquafeeds, in which methionine supplementation levels are based on the requirements of the closely related Japanese Yellowtail (Seriola quinqueradiata) at approximately 11.1 g kg−1 diet. However, recent research has demonstrated better growth and feed efficiency in YTK fed diets containing more than 11 g methionine kg−1, although the precise methionine requirement and potential interactions with cysteine remain unknown. Therefore, the present study was designed to (1) elucidate the methionine requirement of YTK at low and high dietary cysteine contents and to (2) quantify cysteine's sparing capacity for methionine in the TSAA requirement. These requirements and relationships were established by feeding ten isonitrogenous and isoenergetic diets, made from common feed ingredients, to triplicate groups of 12 fish (initial 52.6 ± 1.0 g fish−1) over 54 days. The orthogonal design consisted of two levels of dietary cysteine (5.6 & 13.9 g kg−1), crossed with five levels of dietary methionine, increasing from 7.9 to 25.2 g kg−1. Non-linear regression analysis indicated an average digestible TSAA requirement of 0.70 g kgBW−1 d−1 (0.56 g Met kgBW−1 d−1 & 0.14 g Cys kgBW−1 d−1) based on feed conversion ratio, specific growth rate, and protein retention efficiency. This approximates to an average dietary sulfur amino acid specification of 24.5 g kg−1 (18.9 g Met kg−1 & 5.6 g Cys kg−1). Cysteine spared 40.4–49.2% of methionine in the TSAA requirement on an equimolar sulfur basis. Sub- and supra-optimal levels of dietary methionine and cysteine induced inferior growth and feed efficiency. Additionally, fish fed the diet lowest in dietary methionine and cysteine indicated early stages of cataract. This study provides quantitative data on the sulfur amino acid requirements of juvenile YTK and will facilitate the formulation of better diets for this species.

Modelling of sulphur amino acid requirements and nitrogen endogenous losses in kittens

ABSTRACT The objective of this study was to estimate the sulphur amino acid (methionine + cystine) requirements and nitrogen endogenous losses in kittens aged 150 to 240 d. Thirty-six cats were distributed in six treatments (six cats per treatment) consisting of different concentrations of methionine + cystine (M + C): T1, 6.5 g/kg; T2, 8.8 g/kg; T3, 11.3 g/kg; T4, 13.6 g/kg; T5, 16.0 g/kg; and control, 6.5 g/kg. Diets were formulated by serial dilution of T5 (a diet relatively deficient in M + C but containing high protein concentrations) with a minimal nitrogen diet (MND). Thus, crude protein and amino acid concentrations in diets T1–T5 decreased by the same factor. The control diet was the T1 diet supplemented with adequate concentrations of M + C (6.5 g/kg; 8.8 g/kg; 11.3 g/kg; 13.6 g/kg and 16.0 g/kg). All diets were based on ingredients commonly used in extruded cat diets. Digestibility assays were performed for the determination of nitrogen balance. Nitrogen intake (NI) and nitrogen excretion (NEX) results data were fitted with an exponential equation to estimate nitrogen maintenance requirement (NMR), theoretical maximum for daily nitrogen retention (NRmaxT), and protein quality (b). M + C requirements were calculated from the limiting amino acid intake (LAAI) equation assuming a nitrogen retention of 45 to 65% NRmaxT. The NMR of kittens aged 150, 195, and 240 d was estimated at 595, 559, and 455 mg/kg body weight (BW)0.67 per day, respectively, and M + C requirements were estimated at 517, 664, and 301 mg/kg BW0.67 per day, respectively.

Stable isotopes to study sulfur amino acid utilization in broilers

Nutritionists have been discussing whether the dietary supplementation of cyst(e)ine is required as a part of the dietary methionine (Met) in the total sulfur amino acid (TSAA) requirement to achieve optimum performance in broilers. Part of Met is converted to cysteine (Cys) to meet the Cys requirement, especially for feather growth. The TSAA requirement has been determined by using graded levels of free Met in the diet, without supplementation of free cyst(e)ine. It has also been argued that the Met to Cys ratio (Met : Cys) changes with age and even with different Met sources. The objective of this study was to evaluate the two sources of Met, while determining the proportion of Met and Cys in total dietary TSAA that optimize the performance of broilers. A performance assay was carried out in a factorial arrangement (5 × 2) using 1080 broilers from 42 to 56 days of age fed diets having different dietary proportions of Met and Cys (44 : 56, 46 : 54, 48 : 52, 50 : 50 or 52 : 48) while maintaining the same dietary TSAA in the diets. Two synthetic Met sources (dl-Met or l-Met) were used for each of the diets with different dietary Met : Cys ratios. Twenty-one broilers of the same age were fed the diets 44 : 56, 48 : 52 and 52 : 48 by supplementing the diet with L-(15N) Met or L-(15N2) Cystine to study the metabolism of TSAA. No differences were observed between Met sources for feed intake, BW gain and feed conversion ratio (FCR; P > 0.05); however, FCR was numerically improved at 50 : 50 Met : Cys. Regarding TSAA utilization, the conversion of Met to Cys increased with increase in Met : Cys ratios, but the concentration of Met intermediates decreased. Broiler chickens responded to different dietary proportions of sulfur amino acids by altering their sulfur amino acid metabolism, and diets containing 50 : 50 Met : Cys is recommended for broilers of age 42 to 56 days.

Immune system stimulation increases the irreversible loss of cysteine to taurine, but not sulfate, in starter pigs.

An isotope tracer study was conducted to evaluate the effects of immune system stimulation (ISS) on the irreversible loss of cysteine (Cys) to taurine (Tau) and sulfate (SO4), as well as glutathione (GSH) synthesis, during the fed state in pigs. We previously have reported that ISS increases plasma Cys flux and the GSH synthesis rate at the tissue and whole-body levels in growing pigs. Thus, the current article presents the data on the irreversible loss of Cys during ISS in pigs. Ten gilts (BW: 7.0 ± 0.12 kg) were feed restricted a sulfur amino acids (SAA) limiting diet and injected twice with either saline (n = 4) or increasing amounts of E. coli lipopolysaccharide (n = 6). The day after the second injection, a 5-h primed continuous intravenous infusion of 35S-Cys was conducted. ISS reduced plasma Cys and total SAA concentrations (16% and 21%, respectively; P < 0.05). However, ISS had no effect on the plasma concentrations of Tau and SO4, nor did it affect the appearance of 35S in plasma Tau, plasma SO4, urinary Tau, or urinary SO4 (P > 0.19). On a whole-body basis and including urinary excretion, ISS increased the appearance of 35S in Tau by 67% (P < 0.05), but tended to decrease the appearance of 35S in SO4 by 22% (P < 0.09). Overall, the current findings indicate that during ISS, decreased plasma SAA concentrations and increased plasma Cys flux are attributed in part to increased rates of Cys conversion to Tau, but not Cys catabolism to SO4. Thus, increased utilization of Cys for the synthesis of immune system metabolites, such as GSH and Tau, is likely the main contributor to increased Cys flux during ISS in pigs. In addition, the irreversible loss of Cys during ISS is small and has a minimal impact on the daily SAA requirements of starter pigs.