DL-Met Research Articles

Higher concentrations of folic acid reduced the dietary requirements of supplemental methionine for commercial broilers.

An experiment was conducted to study the effect of supplementing DL methionine (DL Met) at graded concentrations on performance, carcass variables, immune responses and antioxidant variables in broiler chicken fed folic acid (FA) fortified (4 mg/kg) lowmethionine diet. A basal diet (BD) without supplemental DL Met, but with higher level (4 mg/kg) of FA and a control diet (CD) with the recommended concentration of methionine (Met) were prepared. The BD was supplemented with DL Met at graded concentrations (0%, 10%, 20%, 30%, 40%, and 50% supplemental DL Met of CD). Each diet was fed ad libitum to 10 replicates of 5 broiler male chicks in each from 1 to 42 d of age. Body weight gain (BWG) reduced, and feed conversion ratio (FCR) increased in broilers fed low-Met BD. At 30% and 20% inclusion of DL met, the BWG and FCR, respectively were similar to those fed the CD. Similarly, supplementation of 10% DL Met to the BD significantly increased ready to cook meat yield and breast meat weight, which were similar to those of the CD fed broilers. Lipid peroxidation reduced, the activity of antioxidant enzymes (GSHPx and GSHRx) in serum increased and lymphocyte proliferation increased with increased supplemental DL Met level in the BD. The concentrations of total protein and albumin in serum increased with DL Met supplementation to the BD. Based on the data, it can be concluded that supplemental Met can be reduced to less than 50% in broiler chicken diets (4.40, 3.94, and 3.39 g/kg, respectively in pre-starter, starter and finisher phases) containing 4 mg/kg FA.

Effects of DL and L-Methionine on Growth Rate, Feather Growth, and Hematological Parameters of Tetra-SL Layers from 1-28 Days of Age.

Simple SummaryMethionine is the first limiting amino acid and plays an important role in the growth and health status of chicks. Animal health status was easily detected by examining the hematological parameters. This study aimed to investigate the influence of methionine sources (L-methionine and DL-Methionine) at different supplementation levels (10% deficit, 100% and 10% surplus of the recommended) on growth performance and health status of chicks. The results of the feeding trial found no differences in the chicks’ growth performance and feather growth on neither methionine sources nor methionine levels. However, most of the hematology parameters were affected by the methionine sources and/or methionine levels, as well as their interaction being significant in some cases. Therefore, this trial showed that varying methionine by ±10% of the requirements does not adversely affect growth performance and feather growth.The study was carried out to determine whether sources or levels of methionine (Met) affect the health status of Tetra-SL (TSL) chicks by examining growth performance, feather growth, and hematological parameters. A total of ninety-six (96) day-old (44.2 ± 0.18 g lw) TSL chicks were randomly allotted to six treatment groups (three levels for each DL and L-Met source) with four replicates of four chicks each. Chicks were fed ad libitum diets supplemented with 90, 100, and 110% of methionine requirements for four weeks after hatch. The parameters examined are bodyweight (BW), average daily gain (ADG), feather length (FL), and hematological parameters, including: red blood cell (RBC) count, hemoglobin (Hb) concentration in the blood, hematocrit (Ht; %), number of white blood cells (WBC), platelet count, mean corpuscular volume of red blood cells (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), lymphocyte (LYM), mid-range (MID), and granulocyte (GRAN). There was no significant effect of Met sources and levels on BW, ADG, and FL of TSL chicks for the first four weeks of rearing. The RBC, Hb, Ht, WBC, LYM, MID, and GRAN values of TSL chicks were statistically influenced by dietary Met sources and Met levels (p < 0.05). Among the treatment groups, the number of white blood cells (WBC) on 90% DL–Met was the lowest. WBC, RBC, Hb, and Ht were higher from chicks that received 100% DL-Met than all other levels, regardless of the Met sources. The MCV, MCH, and MCHC values were not affected by either Met source or levels or their interactions. Met source and level interactively affected the Ht, WBC, LYM %, and GRAN values of TSL chicks (p < 0.05). The platelet number was affected by Met source only (p < 0.05) with chicks receiving L-Met source having more than twofold higher platelet values than DL-Met source. In conclusion, varying Met levels by ±10% of the requirement does not adversely affect the growth performance, feather growth, and hematological parameters of TSL chicks reared for up to four weeks of age. DL-Met increased the body weight and improved the white blood cells, red blood cells, and hematocrit at 28 days after hatch. DL-Met showed similar biological efficacy as L-Met for body weight and feather growth but not for the hematological parameters.

111 Validation of the Indicator Amino Acid Oxidation Technique in the Domestic Cat

Abstract There is a lack of data on the minimum Met or total sulfur AA (SAA) requirements for adult cats. Non-invasive and precise techniques, such as indicator AA oxidation (IAAO) can be used for these purposes. This pilot study aimed to validate the IAAO technique in cats and investigate the effect of dietary Met concentrations and sources on fasted plasma SAA concentrations. Six cats were fed three experimental diets in random order: Met-deficient diet (BASAL; 0.23% Met+Cys-DM) and two Met-sufficient diets in which either DL-Met (DLM) or Met-hydroxy-analogue (MHA) were supplemented, respectively, on an equimolar basis to meet the total SAA requirement (0.34%-DM). After 2d diet adaptation, IAAO studies were performed. Cats were offered 13 ½-hourly small meals. The 6th meal contained a priming dose (4.8 mg/kg-BW) of L-[1-13C]-Phe and the remaining meals the constant dose (1.04 mg/kg-BW). Breath samples were collected ½-hourly to measure 13CO2 enrichment. The following morning after an 16hr fast, blood samples were collected. Isotopic steady-state was evaluated through linear regression models. Plasma AA data were analyzed using PROC GLIMMIX procedure in SAS (Version 9.4). Met concentrations tended to be higher in cats fed DLM compared to BAS (P = 0.0877), but similar to those fed MHA (P &amp;gt; 0.05). Total cysteine plasma concentrations were similar between treatments (P &amp;gt; 0.05). Cats fed BAS had greater concentrations of plasma HCys compared to DLM and MHA (P = 0.0093). Cats did not reach isotopic steady-state in atom percent excess (P &amp;gt;0.05) regardless of the dietary treatment provided. Non-steady-state kinetics models are under development to predict 13CO2 flux. This study indicates that the short-term feeding of a Met-deficient diet in cats results in greater plasma Hcys and a tendency for lower plasma Met concentrations. A higher prime dose of L-[1-13C]-Phe is warranted to achieve isotopic steady-state and successfully apply the IAAO to estimate AA requirements.

Effect of DL-Methionine Supplementation on Tissue and Plasma Antioxidant Status and Concentrations of Oxidation Products of Cholesterol and Phytosterols in Heat-Processed Thigh Muscle of Broilers.

Simple SummaryThe occurrence of oxidative stress is a general problem in high-yielding farm animals. Oxidative stress not only affects animal health, but free radicals generated under oxidative stress conditions can also promote the oxidation of lipids in animal products which are detrimental for the consumer, such as lipid oxidation products. Therefore, prevention of oxidative stress by improving the antioxidant system has high priority in farm animal management. Methionine (Met) is a precursor of glutathione, one of the major antioxidants in the body. Therefore, we investigated the hypothesis that feeding diets with an excess of Met in relation to the requirement for optimum growth improves the antioxidant status by enhancing the formation of glutathione in broilers. We observed that broilers fed diets with an excess of Met had higher concentrations of glutathione in liver and thigh muscle, indicative of an improved antioxidant status, and moreover had lower concentrations of cholesterol oxidation products in heat-processed thigh muscle, in comparison to broilers of the control group. This effect is favorable with respect to animal health and quality of broiler meat.In this study, the hypothesis that supplementation with methionine (Met) as DL-Met (DLM) in excess of the National Research Council (NRC) recommendations improves the antioxidant system in broilers was investigated. Day-old male Cobb-500 broilers (n = 72) were divided into three groups which were fed a control diet or diets supplemented with two levels of DLM in which the concentrations of Met + Cys exceeded the recommendations of NRC by 15–20% (group DLM 1) or 30–40% (group DLM 2), respectively. The three groups of broilers did not show differences in body weight gains, feed intake, and feed conversion ratio. However, broilers of groups DLM 1 and DLM 2 had higher concentrations of glutathione (GSH) in liver and thigh muscle and lower concentrations of cholesterol oxidation products (COPs) in heat-processed thigh muscle than broilers of the control group. Concentrations of several oxidation products of phytosterols in heat-processed thigh muscle were also reduced in groups DLM 1 and DLM 2; however, the concentration of total oxidation products of phytosterols was not different between the three groups. The study shows that DLM supplementation improved the antioxidant status due to an increased formation of GSH and reduced the formation of COPs during heat-processing in thigh muscle.

Effects of supplementation of DL-methionine on tissue and plasma antioxidant status during heat-induced oxidative stress in broilers

Exposure to high ambient temperature has been shown to impair growth performance and to cause oxidative stress in broilers. This study investigated the hypothesis that supplementation with methionine (Met) as DL-Met (DLM) more than the National Research Council recommendations improves growth performance and alleviates oxidative stress in broilers exposed to high ambient temperature. One-day-old male Cobb-500 broilers (n = 68) were allotted to 4 groups and phase-fed 3 basal diets during days 1 to 10, 11 to 21, and 22 to 35. One group was kept under thermoneutral temperature conditions and received the basal diets with Met + cysteine (Cys) concentrations according to recommendations of NRC. The other 3 groups were kept in a room with an increased ambient temperature from week 3 to 5 and were fed either the basal diet or the basal diets supplemented with 2 levels of DLM in which Met + Cys concentrations exceeded NRC recommendations by around 20% (group DLM1) and 40% (group DLM2), respectively. As expected, the broilers exposed to high ambient temperature showed a lower feed intake, lower body weight gains, a higher feed:gain ratio, and biochemical indications of oxidative stress in comparison to broilers kept under thermoneutral temperature conditions. Supplementation of DLM did not improve the growth performance in broilers exposed to high ambient temperature. However, the broilers supplemented with DLM had increased concentrations of glutathione in liver and breast muscle (groups DLM1 and DLM2), increased concentrations of tocopherols in the liver (group DLM2), and reduced concentrations of 7α-hydroxycholesterol and 7-ketocholesterol in heat-processed thigh muscle (groups DLM1 and DLM2) in comparison to the control group exposed to high ambient temperature. Concentrations of thiobarbituric acid-reactive substances and vitamin C in plasma, liver, and muscle were not different between the 3 groups exposed to heat stress. Nevertheless, the study shows that supplementation of DLM in slight excess of the Met concentration required for maximum growth performance improved the antioxidant status in tissues and reduced the susceptibility of muscle toward oxidation in heat-stressed broilers.

Tissue and plasma antioxidant status in response to dietary methionine concentration and source in broilers.

This study hypothesized that plasma and tissue antioxidant status of broilers is positively influenced when dietary Met concentrations exceed, and negatively when they go below NRC recommendations. In addition, different Met sources are hypothesized to affect the antioxidant defence system differently. Day-old male Cobb-500 broilers (n=336) were allotted to seven groups and phase-fed three wheat-soya bean meal-based basal diets during days 1-10, 11-21 and 22-35. The basal diets (Met- group, Met+Cys concentration 15% below NRC recommendations) were supplemented with 0.10%, 0.25% or 0.40% Met either as DL-Met (DLM) or DL-2-hydroxy-4-(methylthio) butanoic acid (DL-HMTBA) (equimolar comparison). Growth performance and carcass weights were lower in the Met- group compared to the groups whose diets met or exceeded Met requirements. The antioxidant defence system was not influenced by the Met source. However, in the liver, concentrations of glutathione increased with increasing dietary Met concentrations. Tocopherol concentrations in the liver at days 10 and 21 were lower in the Met- group than in the groups supplemented with Met. However, liver concentrations of thiobarbituric acid reactive substances (TBA-RS) and protein carbonyls (PC) were largely not influenced by dietary Met concentration. Plasma tocopherol concentrations at day 35 were lower, and those of TBA-RS and PC at day 35 were higher in Met- group than in the groups fed the Met-supplemented diets. In jejunum, but not in liver, relative mRNA abundances and activities of superoxide dismutase, catalase and glutathione peroxidase were higher in the Met- group than in the groups fed Met-supplemented diets. These data indicate that suboptimum supply of Met results in decreased antioxidant concentrations in plasma and body tissues, and increases oxidative stress in the jejunum mucosa. However, supplementation of Met in excess of the requirements (based on NRC) compared to diets adequate in Met+Cys did not influence the antioxidant defence system.

Bioavailability comparison between herbal methionine and DL-methionine on growth performance and immunocompetence basis in broiler chickens

BACKGROUND:Herbal methionine can be compared relative toDl-methionine with evaluation of bioavailability of this source ofmethionine. OBJECTIVES: An experiment was carried out todetermine the relative bioefficacy of herbal methionine (H-Met)®relative to DL-methionine (DL-Met) on performance criteria andimmunocompetence of Met sources in male broilers. Atotal of 160male broilers were fed a Met-deficient basal diet or the basal dietsupplemented with three or four concentrations of each Metsources. METHODS: Multiexponential and multilinear regressionswere used to determined bioavailability of herbal methionine (HMet)®relative to DL-Met on performance and immunocompetenceof broilers. RESULTS: Body weight gain and feed intake of thebroilers fed H-Met or DL Met improved in the experiment,regardless of Met sources, relative to those broilers that were fed thebasal diet. Immunocompetence of broilers were not significant at 28day of age (p>0.05), whereas the broilers were significantlyaffected by the additional levels of Met sources at 42 day of age.CONCLUSIONS: The bioefficacy estimates for H-Met® relative toDL-Met on a product basis were 55% for weight gain, 71% for feedintake, 78% for feed conversion ratio, 70% for dilution 1-choloro 2-3-dinitrobenzene (DNCB), 67% for sheep red blood cell (SRBC),and 68% for phytohemagglutinine (PHA-P). The relativeeffectiveness of H-Met® compared to that of DL-Met is 68% onaverage across performance criteria and all immune criteria tested.H-Met®can be supplemented as a new and natural source of Met forthe poultry industry.

Milk composition as technique to evaluate the relative bioavailability of a liquid rumen protected methionine source

Rumen protected amino acids (RPAA) are increasingly being used in dairy cattle diet formulation to obtain the required concentrations of lysine and methionine in metabolisable protein for optimal milk and milk protein production. The objective of this study was to evaluate the relative bioavailability of a liquid rumen protected lysine prototype using the milk composition technique. Forty mid-lactation Holstein cows were used in a complete randomised block design experiment and allocated to one of four experimental treatments. The treatments were: (1) Methionine deficient (Met-) diet, (2) Met- diet supplemented with Smartamine M (SMM), (3) Met- diet supplemented with liquid rumen protected prototype (LRPMet) and (4) Met- diet supplemented with DL Met (DLMet), a hydroxyl analogue of methionine. After an adaptation phase all four groups received the Met- diet and thereafter switched over to the four treatments. Cows supplemented with SMM had higher milk protein and milk fat % compared to the other treatments and increased milk casein % significantly when compared to the Met-control treatment. The milk protein percentages were 3.06, 3.25, 2.95 and 3.46 and the milk fat percentages 3.84, 3.93, 3.75 and 4.27 for the Met-, LRPMet, DL Met and SMM treatments, respectively. SMM again proved to be the RPAA with a high relative bioavailability, while the LRPMet failed to elicit any milk yield or milk composition response. The milk composition technique proved to be a simple but effective technique to evaluate the bioavailability of rumen protected products or prototypes.Keywords: Milk composition, rumen protected methionine, amino acids, Holstein cows

The site of intestinal disappearance of DDLmethionine and methionine hydroxy analog differs in pigs1

A study was conducted with pigs to determine the sites of and the influence of dietary wheat middlings (WM) as a fiber source on the absorption of dl-Met (DLM) and dl-2-hydroxy-4-methylthio butanoic acid (HMTBA). Twelve 25-kg barrows were used in a replicated 6 × 4 incomplete Latin-square design with 6 diets and 4 periods per pig. Each pig was surgically fitted with simple T-cannulas in the terminal duodenum and ileum 2 wk before the initiation of the experiment and housed in a stainless-steel metabolism crate. The 6 diets were arranged in a 2 × 3 factorial of WM at 0 (CON) or 8% and Met source including none, DLM, or HMTBA. Supplemental DLM doubled the duodenal free Met concentration from 9.6 to 19.6 g/100 g of DMI. Supplemental DLM also increased the apparent ileal digestibility (AID) of free Met from 52 to 92% (P < 0.05). Adding 8% WM increased (P < 0.01) duodenal NDF concentrations by 2 g/100 g of DMI and decreased (P < 0.05) AID of free Met. No HMTBA was detected in digesta collected from the duodenum or ileum of pigs fed the CON + HMTBA or the WM + HMTBA diets, indicating complete absorption before the terminal duodenum regardless of WM inclusion. Interactions between Met supplementation and WM were observed for the digestibility of all other nutrients (P < 0.05). Fiber and AA digestibility in the ileum were the greatest for the CON + HMTBA diet, and least for the WM + HMTBA diet. The CON + HMTBA diet had greater AID of ADF, NDF, CP, and Thr, and greater AID of ADF, NDF, ash, Arg, Ile, Gly, and Pro when compared with the CON and CON + DLM diets, respectively (P < 0.05). The WM + HMTBA had less AID of ADF, CP, and all AA with the exception of Lys, Trp, and Val when compared with the CON + HMTBA (P < 0.05). In summary, absorption of HMTBA in the pig is complete by the end of the duodenum, but negative interaction between HMTBA and WM can decrease the AID of most AA.

Nutritional Interaction of Methionine Sources and Sodium and Potassium Levels on Broiler Performance Under Brazilian Summer Conditions

Two experiments were conducted to study the performance of heat-stressed chickens fed different levels of Na or K with 2 Met sources. In experiment 1, chickens from 7 to 21 d were fed Na at 3 levels (0.15, 0.20, or 0.25%) and from 21 to 48 d at 0.12, 0.17, or 0.22% Na. In experiment 2, chickens from 8 to 21 d were fed K at 3 levels (0.9, 1.0, or 1.1%) and 22 to 48 d at 0.8, 0.9, or 1.0% K. In both experiments, chickens were fed 2 Met sources, dl-Met (DLM), and 2-hydroxy-4 methylthio butanoic acid (HMB), added equimolar. In experiment 1, all-vegetable diets (corn-soy) were used, and in experiment 2, meat and bone meal was included. Both experiments were performed under Brazilian summer conditions. In experiment 1, no significant interactions between Met and Na levels were found. A positive response for HMB, compared with DLM, was found across Na levels for weight gain (P < 0.05) and feed conversion ratio (FCR P < 0.02) at 48 d. There was no response to Na for weight gain and feed intake (FI), but birds fed the higher level had the best FCR (P < 0.03). In experiment 2, K levels showed a consistent interaction with Met for FI: the highest level of K showed greater FI in HMB birds, but this was not seen when DLM was used. Low and intermediate K levels resulted in better FCR (P < 0.03) compared with higher K levels. No differences in litter moisture were observed between different levels of K. Feathering problems were not evidenced in either experiment. The HMB used in an equimolar amount to DLM resulted in equal bird performance.

Evidence of a Different Dose Response in Turkeys When Fed 2-Hydroxy-4(Methylthio) Butanoic Acid Versus dl-Methionine

In broilers, 2-hydroxy-4(methylthio) butanoic acid (HMTBA) can elicit a different dose response relative to dl-Met (DLM) such that birds could have lower gain responses at deficient TSAA concentrations but greater gain responses at maximum response concentrations. Two experiments tested if the 2 Met sources have a different dose response in 1-d-old turkeys using a 2 x 4 factorial plus a control design with 8 replicates of 12 toms per treatment. 2-Hydroxy-4(methylthio) butanoic acid and DLM were supplemented at equimolar concentrations of 0.05, 0.10, 0.15, and 0.20% or 0.04, 0.08, 0.16, and 0.32% for experiments 1 and 2, respectively, in commercial-type TSAA-deficient (0.99 to 1.02%) diets for 21 d. No differences in any performance parameter tested were found between HMTBA and DLM in either trial by ANOVA. Linear (LIN), quadratic (QUAD), and exponential regressions were fitted to the gain response of birds fed HMTBA or DLM. Equations with better goodness of fit as determined by Schwarz's Bayesian information criteria index were used for further calculations of predicted differences between HMTBA and DLM. In both trials, the shape of the dose response differed according to the Met source used, and best-fit equations were obtained when using Met intake over control rather than dietary Met concentration as the dependent variable. In experiment 1, the best-fit equations were an inverse QUAD for HMTBA and a LIN for DLM, and in experiment 2 with higher Met concentrations, the best-fit equations were a QUAD for DLM and a LIN for HMTBA. Feeding HMTBA at deficient TSAA resulted in lower (P <0.05) gains in experiment 1 but greater gains at maximum response concentrations (P <0.05) in both experiments. Plasma-free Met increased at 3 times the rate for DLM than HMTBA (P <0.01) with increasing Met concentration, which may play a role in the evolution of different dose responses at the extremes of the Met dose response. These results demonstrate that Met sources elicit a differential dose response in turkeys such that feeding HMTBA at deficient TSAA concentrations can be lower than DLM and can reach a higher maximum performance than with DLM.

Homocysteine Remethylation in Broilers Fed Surfeit Choline or Betaine and Varying Levels and Sources of Methionine from Eight to Twenty-Two Days of Age

Experiments were conducted to assess the effect of surfeit choline (CHOL) or betaine (BET) on growth performance and homocysteine (HCY) remethylation of young broilers fed graded levels of DL-Met (DLM) or 2-hydroxy-4-(methylthio) butanoic acid (HMB). In Experiment 1, a corn-peanut meal diet deficient in Met (0.25% digestible) and Cys (0.28% digestible) was fed; treatments were formulated to contain graded levels (0, 0.04, or 0.08%) of Met from DLM or 0.04% HMB (adjusted for 88% purity) that were fed in the presence or absence of surfeit isomethyl CHOL (0.25%) or BET (0.28%). In Experiment 2, identical treatments were used, but an additional level of HMB (0.08%) was fed, and the basal diet was adequate in Cys (0.43% digestible). There was no overall effect of CHOL or BET on growth performance in Experiments 1 and 2 (P > 0.05); a significant improvement (P < 0.05) in weight gain and feed efficiency did occur with CHOL and BET addition to the basal diet in Experiment 2. In both experiments, weight gain increased linearly (P < 0.05) with the addition of DLM or HMB. Slope ratio methodology was used to assess HMB efficacy in Experiment 2. In the presence of adequate Cys, HMB efficacy was 81.3%; addition of surfeit BET or CHOL had minimal effect on efficacy. The stable isotope study revealed that CHOL and BET addition to diets deficient in Met and Cys or Met alone increased HCY remethylation. It also showed that CHOL and BET have greater influence on folate-dependent remethylation of HCY (via Met synthase) than on BET-dependent remethylation (via BET-HCY methyltransferase) and that levels of CHOL and BET and type of S amino acid deficiency effect remethylation and HMB efficacy.

Effect of Arginine:Lysine Ratios and Source of Methionine on Growth and Body Protein Accretion in Acutely and Chronically Heat-Stressed Broilers

The effect of Arg:Lys, Met source, and time of exposure to heat stress on growth and body protein accretion was tested in acutely heat-stressed (AHS) or chronically heat-stressed (CHS) broilers. Ross 308 1-day-old chickens were raised under normal brooding conditions from 1 to 25 d of age and were then suddenly moved to 32°C (AHS), whereas another group was kept at constant high temperatures throughout the grow-out period (32°C; CHS). From 26 to 33 d of age, both groups were therefore at 32.8 ± 1.0°C. Two rooms were used per environmental treatment. A basal diet deficient in TSAA was supplemented with L-Arg monohydrochloride to achieve Arg:Lys ratios of 0.95 and 1.40. Diets were supplemented with either l-Met, 2-hydroxy-4-(methylthio) butanoic acid (HMB), or dl-Met (DLM) to a level of TSAA 5% lower than requirements. Each Arg:Lys and Met source combination was diluted with a N-free diet to achieve graded levels of CP (0.0, 3.5, 7.0, 10.5, 14.0, and 17.5% CP) and fed to 18 replicates of 3 chickens (3 replicates per level). Treatment effects were obtained by the slope-ratio technique using average daily BW gain and body CP deposition as dependent variables and protein intake as the independent variable. Protein utilization remained unaffected by Met source when fed at high Arg:Lys for birds under AHS and CHS (P > 0.05). However, lower protein utilization was observed in birds fed l-Met in low Arg:Lys compared with those fed DLM (P < 0.05). Birds fed HMB at low Arg:Lys utilized dietary protein better than those fed L-Met only under CHS conditions (P < 0.05). Protein utilization for birds fed HMB was similar to that of birds fed DLM in all instances. It was concluded that Arg:Lys, Met source, and time of exposure to heat stress affected protein utilization in hyperthermic birds.

Evidence for 2-Hydroxy-4(Methylthio) Butanoic Acid and dl-Methionine Having Different Dose Responses in Growing Broilers

The objective of this study was to compare the gain-response curve to dietary levels of 2-hydroxy-4(methylthio) butanoic acid (HMTBA) and dl-Met (DLM) across 4 floor pen trials in which different diets were used. Six replicates of 38 or 41 birds per pen (trials 1 to 2 and 3 to 4, respectively) were used in a 2 × 3 factorial arrangement. A control with 12 replicates was also included. The 2 Met sources were fed at 3 equimolar levels equally spaced, with the highest level added at requirements from 1 to 48, 49, 43, or 49 d for trials 1, 2, 3, and 4, respectively. Commercial-type TSAA-deficient control diets contained sorghum, wheat, corn, or corn plus meat and bone meal for trials 1, 2, 3, and 4, respectively. Performance improved at all times for most parameters after supplementing with HMTBA or DLM (P < 0.05). No differences were found in the birds fed HMTBA or DLM at any age and trial (P > 0.05), except for trial 1, in which 17-d-old birds performed better when fed HMTBA than DLM (P < 0.05). In each trial, linear, quadratic, and exponential regressions were conducted upon the gain response of birds fed HMTBA and DLM separately. Equations with better goodness of fit were used to compare the estimated gain responses to feeding HMTBA vs. DLM. In 3 trials, the shape of the gain-response curve differed when feeding HMTBA vs. DLM. In trials 3 and 4, feeding HMTBA at commercial levels resulted in greater gain responses than DLM (P < 0.05), whereas, in trials 2 and 4, at very deficient levels, DLM-fed birds outperformed those fed HMTBA (P < 0.05). When the 4 trials were combined, the dose-response curve with the best goodness of fit was linear for HMTBA and quadratic for DLM. It can be concluded that the 2 Met sources have a different dose-response form, HMTBA could outperform DLM at commercial levels, and DLM could outperform HMTBA at deficient levels.

Concentrations of Putrescine, Spermidine, and Spermine in Duodenum and Pancreas as Affected by the Ratio of Arginine to Lysine and Source of Methionine in Broilers Under Heat Stress

An experiment was designed to investigate the effect of Arg, Lys, Met, and environmental temperature on broiler performance and associated changes in duodenal and pancreatic polyamines. Two groups of 26-d-old Ross male broilers raised under thermoneutral (TN) conditions were reallocated to 4 rooms kept at heat stress (HS) or TN. Birds were fed equimolar amounts of 2-hydroxy-4-(methylthio) butanoic acid (HMB) or dl-Met (DLM) at requirement levels with Arg:Lys at 0.95 or 1.40. Twelve replicates of 4 birds were offered each diet ad libitum. Body weight gain, efficiency of dietary CP accretion (CPE), feed intake, and feed conversion ratio were ascertained from 26 to 33 d and from 34 to 47 d of age. One bird per cage was killed at 33 and 47 d, and samples of duodenum and pancreas were assayed for putrescine, spermidine, and spermine (Spm), together with estimates of duodenal villus height. From 26 to 33 d, birds fed HMB performed better than those fed DLM, but only at TN conditions. From 34 to 47 d, feeding HMB tended to optimize CPE when added to diets high in Arg. However, lower CPE was obtained when HMB was added to low-Arg diets, whereas birds fed DLM were unaffected by these treatments (P < 0.10). Methionineh source, Arg:Lys, or both affected the concentrations of duodenal and pancreatic polyamines, with some changes correlating with performance variables during HS (P > 0.05). It was found that HS caused lower tissue spermidine (P < 0.001) and higher pancreatic Spm (P = 0.08) from 34 to 47 d. Putrescine concentrations were affected by diet and HS, depending on tissue and experimental period. Pancreatic Spm correlated negatively with changes in CPE influenced by Arg:Lys by Met source interaction in chronically heat-stressed birds. The possible association between polyamine metabolism and some of the effects of the Arg:Lys by Met source interaction observed in chronically stressed birds deserves further investigation.

Impact of Methionine Sources on Performance in Turkeys

Data are scarce for relative effectiveness of the liquid hydroxy analogue of Met (MHA-FA) relative to DL-Met (DLM) in turkeys. In the current paper, 2 experiments are presented in order to determine the relative effectiveness of liquid MHA-FA. In trial 1, female 1-d-old Hybrid Converter turkeys were fed 13 different corn-soy diets supplemented with graded levels of DLM, diluted DLM (65%), or liquid MHA-FA (0.07, 0.14, 0.21, 0.28%) from d 7 to 50. DLM (65%) treatments can be regarded as an internal standard for the validation of exponential regression analysis. In trial 2, male 1-d-old BUTA Big 6 turkeys were assigned to 63 battery cages for 21 d. Treatments consisted of a basal corn-soy diet and 2 series each containing graded levels of either DLM (0.100, 0.200, 0.300%) or liquid MHA-FA (0.154, 0.308, 0.462%). The ratio between both products at the 3 corresponding inclusion levels was 65% weight/weight. In both trials, basal diets were formulated to be deficient in Met + Cys but adequate in all other nutrients and energy. Exponential regression analysis revealed a relative effectiveness for weight gain and feed conversion of liquid MHA-FA of 68 and 56% vs. DLM in trial 1, respectively, and of 66 and 44% in trial 2, respectively. These findings support the hypothesis of a relative bioeffectiveness of approximately 65% of liquid MHA-FA as compared with DLM.

Relative effectiveness of methionine hydroxy analog compared to DL-methionine in broiler chickens

Two broiler experiments were conducted to assess the relative bioefficacy of liquid DL-Met hydroxy analog-free acid (MHA-FA) and DL-Met (DLM). Exponential regression analysis was used to determine biological efficacy based on body weight, feed conversion, and carcass responses to dietary Met source. In Trial 1, four graded inclusion levels of DLM and liquid MHA-FA (0.06, 0.12, 0.18, and 0.24%) were each added to a basal diet that met the nutrient and energy requirements of broiler chickens, with the exception of Met + Cys. In four additional treatments, diluted DLM (65%) was added at the same supplementation levels as pure DLM and liquid MHA-FA. In the 42-d trial, broilers responded significantly (P < 0.05) to the supplements. Regression analysis revealed that liquid MHA-FA was 68% (weight gain), 67% (feed conversion), 62% (carcass yield), and 64% (breast meat yield) as efficacious as pure DLM on an as-fed basis. Responses to liquid MHA-FA and diluted DLM were very similar at corresponding supplementation levels. Diluted DLM as an internal standard confirmed that exponential regression analysis was a statistically valid technique for determination of the relative efficacy of nutrient sources. In Trial 2, five graded inclusion levels of each DLM (0.040, 0.091, 0.152, 0.222, and 0.303%) and liquid MHA-FA (0.045, 0.102, 0.170, 0.250, and 0.350%) were added to a basal diet limiting in Met + Cys but adequate in all other nutrients and energy. Liquid MHA-FA was 72% (weight gain), 51% (feed conversion), 48% (carcass yield), and 60% (breast yield) as efficacious as DLM on a weight-for-weight basis.

Effects of 2-Hydroxy-4-(methylthio)butanoic Acid and dl-Methionine on Broiler Performance and Compensatory Growth After Exposure to Two Different Environmental Temperatures

The effects of previous environmental heat stress (HS; 25 to 35°C) or a thermoneutral environment (TNE; 25°C); Met source, DL-Met (DLM) or the hydroxy-analogue of Met (HMB); and Met level were measured in broilers under a TNE (25°C). Performance, carcass measurements, nitrogen retention, and compensatory growth (CG) were evaluated by removing 195 birds from each environment and placing them in individual chambers for 5 d. TNE birds were removed to the chambers at 25, 36, and 49 d of age, and HS birds were removed at 30, 43, and 56 d of age. They continued to receive the same Met source at three different levels: 0.09% DLM or HMB on equimolar basis, 0.04% DLM or HMB, or no Met supplementation. CG was regarded as the difference between a bird's actual growth rate in the chambers and predicted growth based on TNE bird data. Birds from HS exhibited CG for weight gain (WG), breast, leg, abdominal fat, and carcass weight (P < 0.001) but had negative intestinal growth (P < 0.01). There was no difference in CG between Met sources. Birds fed HMB showed better nitrogen retention (P < 0.05), and those from TNE had better WG (P < 0.05) and feed efficiency (P < 0.07) when fed HMB. Only drumstick weights of birds under previous TNE were positively affected by Met level.