Methionine Hydroxy Analogue Free Acid Research Articles

Relative biological efficacy of methionine hydroxy analogue-free acid compared to dl-methionine in the broiler chickens.

In the broiler's diets based on corn-soya bean meal, methionine (Met) and cystine (Cys), known as sulphur amino acids (SAAs), are the first limiting indispensable amino acids because of their limited presence, which are supplemented with different synthetic sources. Evaluation of the biological effectiveness of these sources can be important in their correct replacement, especially in the starter and growth diets. The current study was done to assess the relative biological efficacy (RBE) of liquid Met hydroxy analogue-free acid (MHA-FA) in comparison with dl-Met (dl-Met) based on broiler performance traits at different levels of digestible SAA in the 1-11 (starter) and 11-25 (grower) days of age periods. Two experiments were developed with treatments consisting of a basal diet without Met addition that met the nutrient and energy requirements of broilers with the exception of SAAs (Met+Cys) and five increasing Met doses for both sources (dl-Met and/or MHA-FA), resulting in digestible SAA concentrations from 0.62% to 1.02% of diet in the starter period (Trial 1) and 0.59% to 0.94% of diet in the grower period (Trial 2). The multi-linear regression model and slope ratio method were employed to calculate the RBE of MHA-FA compared with dl-Met for measured variables. In both experiments, the results obtained during the starter and grower periods with the different Met supplementations show significant growth responses to digestible SAAs levels. By increasing dietary dl-Met and/or MHA-FA levels, the growth performance traits and immune responses were improved (quadratic; p<0.05). The RBE of MHA-FA compared to dl-Met on an equimolar basis was estimated 66%-89% (59%-79% on a weight-to-weight basis). It is concluded that the RBE of MHA-FA in comparison with dl-Met depends on broiler chicken age and what attribute is being evaluated.

Multitissue transcriptomics demonstrates the systemic physiology of methionine deficiency in broiler chickens

Methionine (Met) supplementation is common practice in broilers to support nutrition, yet there are gaps in the understanding of its role in systemic physiology. Furthermore, several different Met sources are available that may have different physiological effects. This study evaluated the mode of action of Met deficiency (no Met-supplementation) and supplementation (0.25% DL- or L-Met, 0.41% liquid methionine hydroxy analog-free acid (MHA-FA)), and of Met source (DL-, L- or MHA-FA) in broiler chickens, via host transcriptomics. Biological pathway activation modeling was performed to predict the likely phenotypic effects of differentially expressed genes (DEGs) in tissue samples from the jejunum, liver and breast obtained at 10, 21 and 34/35 d of age from three experiments in a combined analysis. Animal performance data showed that Met deficiency reduced BW, daily BW gain, daily feed intake, and breast yield, and increased feed conversion ratio in all experiments (P < 0.05). Effects of Met deficiency on gene expression were least evident in the jejunum and most evident in the liver and breast, as evidenced by the number of DEG and activated pathways. Activated pathways suggested Met deficiency was associated with inhibited protein turnover, gut barrier integrity, and adaptive immunity functions in the jejunum, that predicted reduced breast yield. There was an interaction with age; in Met-deficient birds, there were 333 DEGs in the jejunum of starter vs finisher birds suggesting young birds were more sensitive to Met deficiency than older birds. In the liver, Met deficiency activated pathways associated with lipid turnover, amino acid metabolism, oxidative stress, and the immune system, whereas in breast, it activated pathways involved in metabolic regulation, hemostasis, the neuronal system, and oxidative stress, again predicting a negative impact on breast yield. In the starter phase, supplementation with DL-Met compared to MHA-FA inhibited gamma-aminobutyric acid activity and oxidative stress in breast tissue. When data from all tissues were integrated, increased expression of a liver gene (ENSGALG00000042797) was found to be correlated with the expression of several genes that best explained variation due to the Met deficiency in jejunum and breast muscle. Some of these genes were involved in anti-oxidant systems. Overall, the findings indicate that impaired growth performance due to Met deficiency results from an array of tissue-specific molecular mechanisms in which oxidative stress plays a key systemic role. Young birds are more sensitive to Met-deficiency and DL-Met was a preferential source of Met than L- or MHA-FA during the starter phase.

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.

Various sources of methionine in broiler chicken rations

Fodder methionine is one of the most important amino acids in animal nutrition, and its deficiency in the ration negatively affects productivity. Currently, the following sources of methionine are represented on the Russian market of feed additives: DL-Methionine and Methionine Hydroxy. Liquid form — Methionine Hydroxy Analog Free Acid (MHA-FA) and dry (for example, МНA) — calcium salt (MHA-Ca2+). The most popular sources of dry methionine are DL-Methionine and hydroxy analog as calcium salt. Many sources state that the bioavailability of the hydroxy analog varies from 65 to 72% (one of the manufacturers of the commercial hydroxy analog claims that the availability of methionine is 84%). The experiment was carried out on broiler chickens. As a result of the studies carried out, it can be argued that the content of DL-methionine in the ration (in the amount of 65% of the hydroxyanalogue) in comparison with MHA-Ca increases the productivity of broilers: preservation – by 4%; live weight by 4.3%; average daily gains by 4.6%; feed conversion decreased by 7.1%; has a positive effect on meat productivity. Based on the data obtained during the experiment, it follows that the efficiency of MHA-Ca does not exceed 65%, compared to DL-Methionine.

Influence of homeopathic medicines and feeding regimen on egg shell quality of layers in hot and humid summer

An experiment was conducted to study the effect of six dietary manipulations in fish meal and corn soya based diet on the egg shell quality of white leghorn hens (WLH) during hot and humid summer. A total of ninety six WLH were divided among 12 dietary treatment groups with 8 birds per treatment. The birds were housed in individual cages for an experimental period of 30 days. Following a 2x6 factorial design six dietary manipulations viz. 1) early (5: 00 am) morning feeding, 2) Calcarea carbonica (Calc carb®), 3) Kalium phosphoricum (Kali phos®), 4) control 5) 0.1% NaHCO3, and 6) 0.3% Methionine hydroxy analogue free acid (MHA-FA) were employed in each fish meal (FM) based and corn-soya (CS) based diet to form 12 dietary treatments. The results have revealed that Kali phos® and Calc carb® were helpful in improving egg shell quality. The former resulted in better egg shell quality in FM based diet. The sodium bi-carbonate, MHA-FA, and early-morning-feeding resulted in significant improvement compared to control in parameters pertinent to egg shell quality. The FM based ration resulted in better egg shell quality compared to CS (Corn-Soya) based ration. Therefore, based on the results of the present study the homeopathic medicine viz. Kali phos® and or Calc carb® in fish meal based diet are a good choice for layer birds to control the loss due to poor shell quality during hot and humid summer.

Bioavailability of liquid methionine hydroxy analogue-free acid relative to DL-methionine in broilers

An experiment with broiler chickens was conducted to compare the relative bioavailability of liquid methionine hydroxy analogue free acid (MHA-FA) with that of DL-methionine (DLM) during fattening to 35 days of age. Ross 308 male chicks were allotted to 9 treatments, each consisting of six replicates of 140 birds/pen. Four graded levels (0.04, 0.08, 0.16, and 0.28 %) of MHA-FA or DLM products (weight/weight comparison) were added to a maize-wheat-soyabean meal basal diet deficient in sulphur amino acids. The criteria of response were body weight, feed conversion ratio, carcass yield and breast meat yield. Significant responses to graded levels of both methionine sources were observed in all response criteria. Using a multi-exponential model describing the dose-response relationships, the bioavailability estimates of MHA-FA relative to DLM on a weight-to-weight basis were 68, 70, 54 and 59 % for body weight, feed conversion, carcass yield and breast meat yield, respectively. If MHA-FA was compared with DLM on equimolar basis its bioavailability was 77.7, 79.0, 59.3 and 64.6 for body weight, feed conversion, carcass yield and breast meat yield, respectively. The bioavailability of MHA-FA for carcass yield and breast meat yield was significantly (P &lt; 0.05) lower than that of DLM on a weight-to-weight and on equimolar basis.

Dietary methionine effects on IGF-I and GHR mRNA expression in broilers

This study aimed to evaluate liver and breast muscle insulin-like growth factor I (IGF-I) and growth hormone receptor (GHR) gene expression between broilers fed different methionine levels and sources. Broiler chicks were 22 to 42 days old, distributed in 5 treatments (control diet, DL1 - 0.08% DL-methionine, DL2 - 0.24% DL-methionine, MHA-FA1 - 0.11% methionine hydroxy analogue-free acid, and MHA-FA2 - 0.33% methionine hydroxy analogue-free acid). The broilers were euthanized by cervical dislocation. RNA was extracted from liver and breast muscle, followed by cDNA synthesis and amplification using qRT-PCR. DL2 methionine supplementation provided best animal performance results. GHR and IGF-I gene expression in the muscle tissue was not affected by methionine supplementation. IGF-I gene expression in the liver was higher in animals fed methionine supplementation than in animals fed control diet. IGF-I mRNA levels in broilers fed DL2 were greater than DL1 (1.56 vs 0.97 AU) and greater than MAH-FA1 and MAH-FA2. Broilers fed DL2 increased significantly GHR gene expression in the liver than animals fed the control diet. Addition of methionine improved animal performance by stimulating synthesis and release of growth factor.

An economic analysis of a methionine source comparison response model

Methionine is the first-limiting amino acid in corn and soybean meal-based poultry diets. Therefore, its supplementation level is of primary economic importance to poultry production. The responses to the methionine sources dl-methionine (DLM) and methionine-hydroxy analog-free acid (HMTBA) have been compared using various methodologies. The so-called common plateau nonlinear model has been used to estimate relative bioavailabilities of the sources. This model has a coefficient that is used as a single value to compare the relative bioavailabilities of the sources for independent technical parameters like gain and feed efficiency. This model was used previously in a meta-analysis of published experiments and found 79 and 81% relative biological efficiencies of HMTBA for DLM for ADG and feed utilization efficiency, respectively. Because different sources would have different optimal feeding levels to maximize profits, we demonstrate the challenge of calculating a single optimal level for the different methionine sources. Further, we apply an economic analysis to results of the previous meta-analysis to demonstrate that the relative values of HMTBA and DLM for BW and ADG are between 81 and 86%, depending on the value of a broiler and the costs of feed and DLM.

Fontes e níveis de metionina em dietas para frangos de corte

Objetivou-se avaliar o efeito de duas fontes de metionina, DL-metionina e metionina hidroxi análoga (MHA-AL), e de três níveis de suplementação desse aminoácido em dietas comerciais sobre o desempenho de frangos de corte. Foram utilizados 1.232 pintos de corte machos da linhagem Ross, de 1 a 47 dias de idade, distribuídos em delineamento inteiramente casualizado, em esquema fatorial 2 X 3 (fonte de metionina X nível de suplementação) e uma dieta adicional (basal) sem suplementação, com oito repetições de 22 aves por unidade experimental. A dieta basal (sem suplementação) foi suplementada com 50, 100 e 150% de MHA ou DL-metionina em quantidade equivalente a 65% da quantidade de cada nível de MHA-AL utilizado. Avaliaram-se o consumo de ração, o ganho de peso, a conversão alimentar e o fator de produção. Em cada nível de suplementação, não houve diferença entre as dietas contendo 100 partes de MHA-AL e 65 partes de DL-metionina, exceto no período de 1 a 10 dias de idade, quando houve diferença significativa no ganho de peso no menor nível de suplementação. Sessenta e cinco partes de DL-metionina equivalem a 100 partes de MHA-AL.

Divergent modulation of swine ileal microbiota by formic acid and methionine hydroxy analogue-free acid

Management of intestinal microbiota of monogastric animals has increased in importance since the ban of growth promoting antibiotics in many countries. Organic acids have been used as alternatives to antibiotics by many feed manufacturers. Regardless of the wide usage, the effect, dose response and mode of action of acids on intestinal microbes is poorly understood. In this study, we investigated the effects of dietary supplementation of three commonly used products, namely formic acid (FA) (90%), dl-methionine (DLM) (99%) and liquid methionine hydroxy analogue-free acid (88%), on ileal microbiota of pigs. Laboratory simulation system, mimicking swine ileum, was used to study the products at various concentrations and combinations. Furthermore, selected combinations were tested in a piglet trial to confirm the findings made in in vitro studies. FA turned out to have a dual effect on ileal microbiota. At concentrations below 0.5%, it significantly stimulated bacteria, but at higher inclusion rates it was highly inhibitory. This finding, which was consistent in in vitro and in vivo studies, implies that reducing the dose of FA does not lead to a diluted inhibitory effect, but in fact, an opposite, stimulatory effect on intestinal microbiota. It is highly important that feed compounders acknowledge this finding. Unlike FA, the inhibitory effect of methionine hydroxy analogue on ileal bacteria was linearly dose dependent and significant at inclusion levels above 0.2%, in vitro. Partial replacement of methionine hydroxy analogue by FA, or FA by methionine hydroxy analogue, led to an unpredictable outcome due to the dual effects of FA; e.g., a minor inclusion of added FA changed the inhibitory effect of methionine hydroxy analogue into microbial stimulation by FA. Inhibition of ileal microbiota by methionine hydroxy analogue was detected only in in vitro studies, suggesting that intact methionine hydroxy analogue may not have reached the ileum, in live animals. Therefore, if the target is to ensure the inhibitory effect of FA, the FA level in feed should be kept above 0.6%, and not reduced, if methionine hydroxy analogue is used as a methionine source instead of DLM. DLM was totally inert with regard to bacterial growth and metabolism, both in vitro and in vivo. The results of these studies reveal the importance of knowing how each acid product works. Inconsistent results in animal trials may have been partly due to quadratic dose–response effects of products, and unpredictable product combination effects.

Effects of Adequate or Marginal Excess of Dietary Methionine Hydroxy Analogue Free Acid on Growth Performance, Edible Meat Yields and Inflammatory Response in Female Broiler Chickens

Two experiments were conducted to determine the effects of adequate or marginal excess of dietary DL-2-hydroxy-4-(methylthio) butanoic acid (MHA) on productive performance and inflammatory response induced by E. coli lipopolysaccharide (LPS). In first experiment, day-old-female chicks (Ross strain) were provided for 48 days with four experimental diets; (1) AB diet: a diet with antibiotics (AB) and DL-methionine (DLM) to meet the total sulfur amino acid (TSAA) requirements of broiler chickens, (2) DLM diet: the first diet without AB, (3) MHA diet: a diet supplemented with MHA in place of DLM of the diet 2 to meet the TSAA requirement, (4) excess MHA diet: a diet with 1.6 folds higher than the content of MHA in the MHA diet. All diets were formulated with ingredients of plant origin. There was no difference in growth performance among the dietary treatments. Edible meat yields in chicks fed the excess MHA diet were better than that in chicks fed the DLM or MHA diet. Chicks fed the excess MHA or MHA diet showed lower plasma ceruloplasmin and alpha-1 acid glycoprotein concentration following LPS injection than those fed the DLM diet at 23 days of age. The concentrations in chicks fed the excess MHA diet were comparable to those chicks fed the AB diet. In second experiment, 7-days -old female chicks were fed either of the DLM or MHA diet for 14 days. Chicks fed the MHA showed higher excreta dry matter content than chicks fed the DLM diet. Heterophil to lymphocyte ratio in blood after LPS injection was lower in chicks fed the MHA diet than that in chicks fed the DLM diet. These results suggest that marginal excess supplementation of MHA, in place of DLM, to diet improved meat production in female broiler chicks and dietary MHA has potential to alleviate certain stress responses.

The Relative Effectiveness of Liquid Methionine Hydroxy Analogue Compared to DL-methionine in Broilers

The present experiment was conducted to assess the efficacy of liquid methionine hydroxy analogue-free acid (MHA- FA) in comparison to DL-methionine (DL-Met) in broilers. 567 day-old Avian chicks were divided into 7 treatments with 5 replicates of 16 birds each. During the 35d (7-42 d) experimental periods chicks were given two basal diets. From 7 to 21d of age, a starting basal diet containing 19.5% protein and 0.33% methionine was supplemented with two graded levels of DL-Met (0.070 and 0.160%) or four levels of MHA-FA (0.118, 0.143, 0.221 and 0.268%). From 22 to 42d of age DL-Met (0.050 and 0.080%) or MHA-FA (0.071, 0.074, 0.112 and 0.140%) were added to a finishing basal diet with 18.0% protein and 0.28% methionine. Chicks fed on supplemental DL-Met or MHA-FA had significantly higher (p<0.05) body weight gain and feed conversion ratio (FCR) than the control group from 7-21d of age. During the finishing phase (22-42 d), body weight and weight gain of chicks in DL-Met or MHA-FA treatments were similar to those in the control, but FCR was improved (p<0.05) with supplementation of DL-Met or MHA-FA. Breast yield was higher (p<0.05) on DL-Met or MHA-FA supplemented than un-supplemented diets. The thigh meat yields emanating from diets with DL-Met or MHA-FA were lower (p<0.05) than that in control. Abdominal fat was also higher in broilers fed the control diet than in DL-Met or MHA-FA supplemented treatments. Methionine requirement of broilers was calculated to be 0.44 and 0.35% and cystine requirement was 0.35 and 0.31% for the starting (7-21 d) and finishing phase (22-42 d), respectively. The efficacy of MHA-FA in comparison to DL-Met for weight gain was 64 and 85% and for FCR was 55 and 60% at 7-21 and 22-42 d of age, respectively, while it was 74, 72, 52 and 48% for breast yield, thigh meat production, body energy content and energy deposition ratio at 42 d of age, respectively. In conclusion, in practical diet formulation for broiler chicks the average bioavailability of MHA-FA relative to DL-Met could be considered as 60 and 73% for 7 to 21d and 22 to 42 d of age, respectively. (Key Words : DL-Met, MHA-FA, Broiler, Growth Performance, Carcass Traits)

Performance of broilers fed with different levels of methionine hydroxy analogue and DL-methionine

One-day-old male Ross chicks were used in an experiment designed to compare two methionine sources, DL-methionine and methionine hydroxy analogue free acid (MHA-FA), and four different levels: 0.41; 0.47; 0.53; 0.59% (starter diet); 0.35; 0.41; 0.47; 0.53% (grower diet); and 0.30; 0.36; 0.42; 0.48% (finisher diet). One thousand two hundred and eighty chicks were housed in 32 experimental floor-pens (40 birds each) and fed 8 experimental diets based on corn and soybean meal for 47 days. The effects of methionine sources and levels were evaluated by performance data, carcass and cut yields, feather yield and abdominal fat content. Data were analyzed as a completely randomized design in a 2x4 factorial arrangement (2 sources and 4 levels), with 8 treatments and 4 repetitions. Analysis of variance was performed using PROC GLM of SAS©. Data indicated DL-methionine to be more effective in promoting growth than MHA-FA, and weight gain increased numerically in response to increasing levels of methionine in all phases.

Dietary supplements of methionine increase breast meat yield and decrease abdominal fat in growing broiler chickens

The response of male broiler chickens to graded amounts of an essential amino acid (methionine) or an amino acid analogue (methionine hydroxy analogue free acid, MHA-FA) was examined in this experiment. The effects of each supplement on food intake, food conversion and the masses of a demand tissue (breast meat) and an indicator of body fat (abdominal fat pad) were measured. Birds grew significantly faster, ate more and had a lower food conversion ratio when there was more DL-methionine or MHA-FA in the diet. After standardising the differences in food intake between treatments, there were still highly significant differences in liveweight between diets. After removing the variation due to treatment differences in body mass, the data showed that adding either DL-methionine or MHA-FA to the diet increased the mass of breast meat and reduced the size of the abdominal fat pad. Exponential equations fitted to the body mass and feed conversion ratio data indicate that, in an equimolar comparison, MHA-FA is 78 and 70% as potent as DL-methionine for growth and feed conversion ratio respectively. Similar equations fitted to the carcass data show that MHA-FA is only 71% as potent as DL-methionine in depositing breast tissue. Increasing amounts of DL-methionine reduced the variability in liveweight and carcass, breast and abdominal fat pad weights. Adding 0.05% MHA-FA reduced variability in these traits compared with the basal ration but higher amounts of MHA-FA had no additional effect.

Liquid Methionine Hydroxy Analog (Free Acid) and DL-Methionine Attenuate Calcium-Induced Kidney Damage in Domestic Fowl

To evaluate the possibility that kidney damage may be induced by the commercial practice of feeding high-Ca (HCa) prelayer rations, and to evaluate the protective efficacy of supplementing HCa diets with liquid methionine hydroxy analog free acid or DL-methionine, 12-wk-old female Single Comb White Leghorn pullets were fed one of the following corn-soybean meal-based diets until they reached 22 wk of age: normal-Ca (NC, 1% Ca); HCa (HC, 3.5% Ca); HCa supplemented with .34 or .68% liquid methionine hydroxy analog free acid (HC3A or HC6A); or HCa supplemented with .3 or .6% DL-methionine (HC3DL or HC6DL). The unsupplemented HC diet caused a significant reduction in kidney mass and a significant increase in the incidence of gross kidney damage and urolithiasis in pullets necropsied at 22 wk of age. Calcium-induced kidney damage was attenuated in a dose-response fashion by supplementing the HC diet with liquid methionine hydroxy analog and DL-methionine. None of the diets caused a significant metabolic acidosis. Plasma uric acid concentrations were not predictive of the extent of Ca-induced kidney damage. Analyses of glomerular size distributions indicated that subclinical or “hidden” kidney damage may not progressively develop into urolithiasis as hens mature. When compared with hens reared on the NC diet, rearing hens on the HC, HC3A, HC3DL, HC6A, or HC6DL diets did not consistently affect hen-day egg production, egg mass, eggshell mass, percentage eggshell, or bone mineralization.

Comparison of DL‐methionine and methionine hydroxy analogue‐free acid in broilers by using multi‐exponential regression models

Abstract 1. Methionine hydroxy analogue‐free acid (MHA‐FA) was evaluated for biopotency compared to DL‐methionine in a practical diet for broiler chicks. 2. Both methionine sources were added at equimolar concentrations of 0.03, 0.07, 0.11, 0.15, 0.20 and 0.25% to the diet. 3. A non‐linear multi‐exponential regression model was used to describe the weight gain and food conversion response to supplemental sources of methionine. 4. Compared with DL‐methionine on an equimolar basis, bioefficacy of MHA‐FA was calculated at 73% from weight gain and 68% from food conversion data, respectively. This corresponds to an efficiency of Alimet® between 60 and 64% relative to DL‐methionine on a weight for weight basis.

An Evaluation of Methionine Hydroxy Analog Free Acid Using A Nonlinear (Exponential) Bioassay

Two experiments were conducted to determine the bioefficacy of methionine hydroxy analog free acid (MHA-FA) using the nonlinear (exponential) bioassay method. Male broiler chicks were fed a low methionine diet composed primarily of ground yellow corn and soybean meal for the 1st wk. The experimental diets, which varied in eight levels of DL-methionine and in eight equimolar levels of MHA-FA, were fed from 7 to 21 days of age. The source of protein was soybean meal and isolated soybean meal (15% of each) in the first experiment and soybean meal and peanut meal (23 and 21%, respectively) in the second experiment with glucose as the primary source of energy. Compared with DL-methionine on an equimolar basis, the bioefficacy of the MHA-FA was 72 ± 5 and 73 ± 7% using weight gains and feed conversions, respectively, from the first experiment and 85 ± 11 and 79 ± 8% using weight gain and feed conversion from the second experiment. These results clearly show that DL-methionine is much superior to MHA-FA on an equimolar basis.

Responses of finishing broilers at high temperatures to dietary methionine source and supplementation levels

The methionine requirements of 3-6-week-old broilers kept at a constant 30�C or at diurnally cycling temperatures of 25-35�C were reduced compared with broilers kept at 21�C. The methionine requirements varied from 0.29 g/MJ of metabolizable energy (ME) at 2 1�C to 0.26 g/MJ of ME at 25-35�C to 0.22 g/MJ of ME at 30�C with total sulfur amino acid requirements of between 0.51 and 0.55 g/MJ of ME. The estimate at 21�C is similar to recommendations made by others for moderate temperatures. Differences in response to DL-methionine and methionine hydroxy analogue free acid were small.

A rapid h.p.l.c. method for the determination of methionine hydroxy analogue free acid in supplemented feeds

AbstractTwo methods are described for determining methionine hydroxy analogue free acid (HMB) in supplemented poultry feeds. The procedure is based on extraction of analogue from the feed, followed by high‐pressure liquid chromatographic measurement of the HMB directly after extraction or, more rigorously, after extraction and hydrolysis of oligomers to monomer. Recoveries of HMB over the supplementation range 0.08–0.25% (by wt) are 98% with coefficients of variation of 5.4% in commercial poultry feeds. A 98% correlation coefficient is obtained when the analyses are compared with the gas chromatographic method.

Biological Efficacy of Liquid Methionine and Methionine Hydroxy Analogue-Free Acid in Chicks

An experiment was conducted to determine biological efficacies of DL-methionine-Na (Liquimeth®) and DL-methionine hydroxy analogue (MHA)-free acid (Alimet®) relative to DL-methionine in Single Comb White Leghorn male chicks. A crystalline amino acid mixture devoid of sulfur-containing amino acids was used for the basal diet, and the test substances were added at .1, .2, and .3% levels, equivalent to DL-methionine on a molar basis, in place of cornstarch. By a slope ratio assay using chick growth as a criterion, the relative biological efficacies of DL-MHA-free acid and DL-methionine-Na to DL-methionine were found to be 70 and 113%, respectively, on a molar basis.