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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.

This study investigated the hypothesis that dietary supplementation of leucine (Leu) above actual recommendations activates protein synthesis and inhibits protein degradation pathways on the molecular level and supports higher muscle growth in broilers. Day-old male Cobb-500 broilers (n = 180) were allotted to 3 groups and phase-fed 3 different corn-wheat-soybean meal-based basal diets during periods 1 to 10, 11 to 21, and 22 to 35 D. The control group (L0) received the basal diet which met the broiler's requirements of nutrients and amino acids for maintenance and growth. Groups L1 and L2 received basal diets supplemented with Leu to exceed recommendations by 35 and 60%, respectively, and isoleucine (Ile) and valine (Val) were supplemented to keep Leu: Ile and Leu: Val ratios fixed. Samples of liver and breast muscle and pancreas were collected on days 10, 21, and 35. The gene expression and abundance of total and phosphorylated proteins involved in the mammalian target of rapamycin pathway of protein synthesis, in the ubiquitin-proteasome pathway and autophagy-lysosomal pathway of protein degradation, in the general control nonderepressible 2/eukaryotic translation initiation factor 2A pathway involved in the inhibition of protein synthesis, and in the myostatin-Smad2/3 pathway involved in myogenesis were evaluated in the muscle, as well as expression of genes involved in the growth hormone axis. Growth performance, feed intake, the feed conversion ratio, and carcass weights did not differ between the 3 groups (P > 0.05). Plasma concentrations of Leu, Ile, and Val and of their keto acids, and the activity of the branched-chain α-keto acid dehydrogenase in the pancreas increased dose dependently with increasing dietary Leu concentrations. In the breast muscle, relative mRNA abundances of genes and phosphorylation of selected proteins involved in all investigated pathways were largely uninfluenced by dietary Leu supplementation (P > 0.05). In summary, these data indicate that excess dietary Leu concentrations do not influence protein synthesis or degradation pathways, and subsequently do not increase muscle growth in broilers at fixed ratios to Ile and Val.

This study investigated the hypothesis that dietary fats rich in lauric (C12) and myristic acid (C14) increase broiler performance and that the underlying mechanism involves antimicrobial effects on gut bacteria and changes in gut morphology. One hundred eighty 1-day-old Cobb-500 broilers were allotted to 3 groups. All groups received a basal diet consisting of maize, wheat, soybean meal, and a fat source (4.5, 7.0, 7.6, and 8.0% of fat product in the diet during d 1 to 9, 10 to 17, 18 to 27, and 28 to 35, respectively) until 35 d of age. The diet of the control group contained a fat with 67% of oleic and linoleic acid and 1.4% of C12 and C14 of total fatty acids, that of the esterified lauric and myristic acid (ELA) group a fat with 33% of esterified C12 and C14 and that of the free lauric and myristic acid (FLA) group a fat with 31% of both esterified and free (1:1) C12 and C14 (6 replicates/treatment, 10 birds/replicate). Gain and feed consumption did not differ between groups, but feed:gain was lower in FLA group as compared to the control group (P < 0.05). Carcass weight, liver weight, triglyceride content of liver and muscle, and muscle cholesterol were similar between groups; however, breast muscle weight was higher in the FLA than in the control group (P < 0.05). The villus height:crypt depth ratio of the duodenal wall did not differ between groups, but in the jejunum, it was lower in the FLA group as compared to the control group (P < 0.05). DNA copy numbers of Lactobacillus, Bifidobacteria, Enterobacteria, Escherichia coli, and Campylobacter jejuni in jejunal digesta were similar among groups. The study shows that dietary fats rich in free C12 and C14 improved feed:gain and breast muscle yield, but the observed effects could not be conclusively explained based on the parameters measured. The decreased jejunal villi:crypt ratio may point to changes in gut protein or cell turnover.

This study investigated the hypothesis that dietary supplementation of lignocellulose in broilers influences the gut bacterial population and bacterial fermentation, has anti-inflammatory effects, and increases mucin synthesis in the intestine, and, through these changes, influences broiler performance positively. Day-old male Cobb 500 broilers (n = 96) were allotted to 3 experimental groups and fed 3 different maize-wheat-soybean meal-based basal diets during days 1 to 10, 11 to 21, and 22 to 35. The basal diets were fed to the control group, and were supplemented with 0.8% of a standard lignocellulose (LCS) or a fermentable lignocellulose (LCF). Body weight and feed consumption were determined, and at slaughter (day 35), carcass and gizzard weights and gizzard content pH were recorded, and samples of jejunum, cecum, and colon mucosa and of cecum digesta were collected from 15 birds/group. Growth performance and feed intake were not influenced, but dressing percentage was higher in group LCF compared to the other groups. In group LCS and the control group, performance, gizzard weight and gizzard content pH, intestinal gene expression of pro-inflammatory cytokines and of the mucins 2, 5ac and 13, the cecal short-chain fatty acid (SCFA) profile, and bacterial diversity were similar, and relative abundance of bacterial groups (16S DNA sequencing) differed. Supplementation of LCF decreased the expression of the pro-inflammatory genes encoding interleukins 1s and 17 (P < 0.05) and those of 2 and 8 (P < 0.10) in the jejunum only. The bacterial population differed, and the SCFA profile shifted toward acetate at the expense of butyrate in group LCF compared to the control group. For example, the abundance of Firmicutes and of Ruminococcaceae and Lactobacillaceae decreased, whereas those of Peptostreptococcaceae, Erysipelotrichaceae, and Enterobacteriaceae and that of members of the phylum Proteobacteria increased in group LCF compared to the control group. These data indicate that the susceptibility of lignocellulose to fermentation is crucial for mediating its effects on intestinal gene expression and the bacterial population in the cecum, which may also affect dressing percentage.

The aim of this study was to investigate the influence of different methionine sources and concentrations on the quality and spoilage process of broiler meat. The trial was comprised of 7 treatment groups: one basal group (suboptimal in Methionine+Cysteine; i.e., 0.89, 0.74, 0.69% in DM SID Met+Cys in starter, grower, and finisher diets, respectively) and 3 doses (0.10, 0.25, and 0.40%) of either DL-Methionine (DLM) or DL-2-hydroxy-4-methylthio butanoic acid (DL-HMTBA) on an equimolar basis of the DLM-supplemented groups. The broilers were fed the diets for 35 d, then slaughtered and processed. The filets were aerobically packed and stored under temperature controlled conditions at 4°C. Meat quality investigations were comprised of microbial investigations (total viable count and Pseudomonas spp.), pH and drip loss measurements of the filets. The shelf life of the meat samples was determined based on sensory parameters. After slaughtering, all supplemented meat samples showed a high quality, whereby no differences between the 2 methionine sources could be detected for the microbial load, pH, and drip loss. In comparison to the control group, the supplemented samples showed a higher sensory quality, characterized by a fresh smell and fresh red color. Methionine supplementation had a significant influence on meat quality parameters during storage. The microbial load, pH and drip loss of the chicken filets were positively correlated to the methionine concentration. Additionally, the microbial load at the end of storage was positively correlated to pH and drip loss values. Nevertheless, the microbial parameters were in a normal range and the positive correlation to methionine concentration did not affect the sensory shelf life. The mean sensory shelf life of the broiler filets varied between 7 to 9 d. During storage, no difference in the development of sensory parameters was observed between the supplemented groups, while the spoilage process of the basal group occurred slightly faster. In conclusion, methionine concentration, but not methionine source, effected meat quality parameters in breast muscles of broilers.

The present study was performed to assess the bioefficacy of DL-methionine hydroxy analogue-free acid (MHA) in comparison to DL-methionine (DLM) as sources of methionine for growing male white Pekin ducks in the first 3 wk of life. For this aim, 580 1-day-old male ducks were allocated into 12 treatment groups and received a basal diet that contained 0.29% of methionine, 0.34% of cysteine and 0.63% of total sulphur containing amino acids or the same diet supplemented with either DLM or MHA in amounts to supply 0.05, 0.10, 0.15, 0.20, and 0.25% of methionine equivalents. Ducks fed the control diet without methionine supplement had the lowest final body weights, daily body weight gains and feed intake among all groups. Supplementation of methionine improved final body weights and daily body weight gains in a dose dependent-manner. There was, however, no significant effect of the source of methionine on all of the performance responses. Evaluation of the data of daily body weight gains with an exponential model of regression revealed a nearly identical efficacy (slope of the curves) of both compounds for growth (DLM = 100%, MHA = 101%). According to the exponential model of regression, 95% of the maximum values of daily body weight gain were reached at methionine supplementary levels of 0.080% and 0.079% for DLM and MHA, respectively. Overall, the present study indicates that MHA and DLM have a similar efficacy as sources of methionine for growing ducks. It is moreover shown that dietary methionine concentrations of 0.37% are required to reach 95% of the maximum of daily body weight gains in ducks during the first 3 wk of life.

The present study was undertaken to find out whether the tryptophan requirement of laying hens is influenced by the supply of large neutral amino acids (LNAA). A factorial experiment was performed in which the dietary tryptophan concentration was varied at six different levels (1.0, 1.25, 1.5, 1.75, 2.0, and 2.5 g tryptophan/kg diet). As the second factor, the dietary concentrations of LNAA (isoleucine, valine, leucine, phenylalanine, and tyrosine) were varied at two levels. The first level provided an adequate supply of these amino acids; at the second level the concentrations of these amino acids were 40% higher than at the first level. The tryptophan requirement was estimated by a broken-line model and an exponential model of regression analysis. The tryptophan intake required for optimum (100% of maximum in the broken-line model, 95% of the maximum in the exponential model) egg production and daily egg mass was lower in hens fed the diets with high LNAA concentrations (145 and 155 mg/hen per day, respectively, in average of both models) than in hens fed the diets with adequate concentrations of LNAA (184 and 198 mg/hen per day, respectively, in average of both models). In contrast, the tryptophan requirement for optimum BW gain was lower in hens fed the diets with adequate LNAA concentrations (178 mg tryptophan per day) than in hens fed the diets with a high concentration of LNAA (212 mg tryptophan per day). In conclusion, the study suggests that an interaction between dietary LNAA and tryptophan exists in laying hens.

The present study was undertaken to investigate the interactions among the supplies of isoleucine, leucine, valine, and tryptophan in laying hens. A three-factor trial was conducted with laying hens in which the dietary concentrations of isoleucine (5.7, 8.0, and 11.5 g/kg), valine and leucine (6.3 and 7.2 g/kg and 10.1 and 11.5 g/kg, respectively), and tryptophan (1.5 and 2.4 g/kg) were varied. At the lowest concentration of valine + leucine, an increase in dietary isoleucine concentration led to a dose-dependent reduction in feed consumption, daily egg mass, and body weight gain and an increase of the isoleucine concentration in plasma. At a high dietary concentration of valine + leucine, excess dietary isoleucine concentration caused only a weak depression of performance parameters; the isoleucine concentration in plasma was independent of the dietary isoleucine concentration. Increasing the dietary tryptophan concentration did not influence the effect of an excessive dietary isoleucine concentration on performance parameters. Increasing the tryptophan concentration from 1.5 to 2.4 g/kg diet did, however, lead to a significant increase in feed consumption, irrespective of the supply of isoleucine, valine, and leucine. In conclusion, our study demonstrates that the supply of valine + leucine influenced the effects of excess dietary isoleucine in laying hens, whereas the supply with tryptophan did not.

Three production trials and one nitrogen balance trial were conducted with Lohmann Brown hens to determine the requirement for and effects of an excess of isoleucine in layers at different ages (24 to 32 and 46 to 54 wk of age). The trials were designed as dose-response studies where isoleucine-deficient basal rations with 11.4 MJ metabolizable energy per kilogram were supplemented with varying amounts of L-isoleucine. In the production trials, dietary isoleucine concentrations ranged from 0.37 to 1.05%. In the three production trials, maximum daily egg mass was achieved at dietary isoleucine concentrations of between 0.39 and 0.75% (25 to 32 wk of age, daily egg mass 53 g), 0.40 and 0.57% (24 to 32 wk of age, daily egg mass 57 g), and 0.40 and 0.81% (46 to 54 wk of age, daily egg mass 56 g). The corresponding ranges of daily isoleucine intakes were 412 to 770 mg, 436 to 624 mg, and 431 to 874 mg. In the nitrogen balance trial, maximum total nitrogen retention was achieved at dietary isoleucine concentrations of between 0.43 and 0.57%. Dietary isoleucine concentrations higher than 0.8% caused a reduction in hen BW. Dietary isoleucine concentrations higher than 1.0% additionally caused a reduction in the daily egg mass. The study thus shows that the margin between requirement and excess of isoleucine is narrow in laying hens.

The effects of dietary conjugated linoleic acid (CLA) and an alpha-glucosidase inhibitor--Bay g 5421--on tissue lipid concentrations and fatty acid composition were investigated in male broiler chicks fed a low-protein diet. The trial comprised six isoenergetic broiler diets. One diet (high-protein diet) was used as a control diet and contained 230 g crude protein per kilogram. The other five diets were low-protein diets (180 g crude protein/kg) without additional supplement, or supplemented with 20 or 40 g/kg of a CLA-enriched oil, or supplemented with 50 or 100 mg of Bay g 5421/kg. Broilers fed the low-protein diets had higher concentrations of triglycerides and cholesterol in the liver than broilers fed the high-protein diet. Broilers fed low-protein diets supplemented with CLA had a higher cholesterol concentration in plasma, lower hepatic triglyceride concentrations, higher relative concentrations of saturated fatty acids (SFA), and lower relative concentrations of monounsaturated fatty acids (MUFA) in lipids of liver, thigh muscle, and adipose than broilers fed low-protein diets without CLA supplement. Broilers fed the low-protein diets supplemented with Bay g 5421 had lower concentrations of triglycerides and cholesterol in the liver and lower concentrations of triglycerides in plasma than broilers fed the low-protein diet without supplementation. Moreover, broilers fed diets with Bay g 5421 had higher relative concentrations of polyunsaturated fatty acids and lower relative concentrations of MUFA in lipids of liver, muscle, and adipose tissue. The results show that supplementation of the low-protein diets with CLA and Bay g 5421 affected tissue lipid concentrations and fatty acid composition in broilers, which are of practical relevance with regards to meat quality.