Variations in the digestible lysine requirement of broiler chickens due to sex, performance parameters, rearing environment, and processing yield characteristics

Enrichment of Broiler Chickens' Meat with Dietary Linseed Oil and Lysine Mixtures: Influence on Nutritional Value, Carcass Characteristics and Oxidative Stress Biomarkers

This study aimed to evaluate the effect of four combinations of dietary linseed oil and lysine mixtures on performance, fatty and amino acid profiles, oxidative stress biomarkers, cell energy and meat quality parameters of broiler chickens. One hundred and sixty broiler chicks were allocated into four groups. Birds of groups 1–4 were fed diets containing optimum lysine and 2% of linseed oil, optimum lysine and 4% of linseed oil, high lysine and 2% of linseed oil, and high lysine and 4% of linseed oil, respectively, for a period of 35 days. High linseed oil or lysine levels did not affect the performance of the tested birds, but the high level of dietary linseed oil decreased the concentrations of muscles’ saturated fatty acids (SFA). The highest values of ω-3 polyunsaturated fatty (ω-3 PUFA) and arachidonic acids with lowest levels of monounsaturated fatty (MUFA) were detected in the muscles of birds fed diets containing high linseed oils and/or lysine levels. High linseed oil or lysine levels provided the best essential amino acid profile and improved antioxidant components as well as cell energy, and tenderness and redness of the meat. Conclusively, high dietary lysine and linseed oil combinations improved the nutritional value, antioxidant status and cell energy of broiler chickens’ meat.

Growth performance and accretion of selected amino acids in response to three levels of dietary lysine fed to fast- and slow-growing broilers

Literature data indicate that feed intake is sensitive to the dietary Lys content particularly in fast-growing birds. From a conceptual and a practical viewpoint, an interaction between genotype (i.e., fast-growing vs. slow-growing birds) and dietary Lys content is of interest, but it needs confirmation owing to a dearth of studies addressing this issue. A study was conducted with 266 Cobb 500 birds and 266 Thai native crossbreed birds serving as models for fast-growing broilers (FGB) and slow-growing broilers (SGB), respectively. Within genotype, chicks were randomly allocated to diets containing either a high (H-LYS = 1.36%), medium (1.17%), or low Lys (1.01%) content. Growth performance and the accretion of protein and selected amino acids were determined in birds from 1 to 21 d of age. Treatments were arranged in a factorial design with 6 replications/treatment. Low Lys vs. H-LYS caused a 42.1% lower feed intake in FGB (P < 0.001), but not in SGB (P = 0.596). The feed conversion ratio (FCR (g feed/g BW gain)) was lowest in FGB (P < 0.001) and increased with decreasing dietary Lys contents (P < 0.001). The Lys induced increase in FCR, however, was more pronounced in SGB (P = 0.025). The absolute protein gain (g/bird) was influenced by the Lys content of feed and decreased by ∼54% and ∼23% in FGB and SGB, respectively (P < 0.001). The efficiency (% of intake) of protein accretion was found to be greater in FGB (P ≤ 0.001) and decreased with decreasing dietary Lys (P ≤ 0.001). The efficiency of Lys accretion was found to be negatively affected by the dietary Lys content in FGB (P < 0.001) but not SGB (P_{genotype × dietary Lys} = 0.008). It can be concluded that a dietary Lys content of 1.01% does not safeguard both growth performance and body protein accretion efficiency in both FGB and SGB. The suboptimal growth performance in FGB, but not SGB, is partially counteracted by a Lys-induced reduction in feed intake.

Effect of dietary digestible lysine level on growth performance, blood metabolites and meat quality of broilers 23-38 days of age

This study was done to evaluate the effects of different dietary digestible lysine (dig Lys) levels on growth performance, blood metabolites, carcass and breast yield, and breast meat quality of broilers 23-38 days of age. Three hundred 23-day-old Cobb-500 male broiler chickens were allocated to a completely randomized design with five treatments (finisher diet containing 0.88%, 0.94%, 1.00%, 1.06% and 1.12% dig Lys) and six replicates of 10 birds each. Feed intake (FI) was not affected by different dietary dig Lys levels. Weight gain (WG) linearly increased and feed conversion ratio (FCR) linearly decreased with an increasing dietary dig Lys levels. With increasing dietary dig Lys levels, carcass and breast yield and breast meat hue angle (h^* ) linearly increased, but abdominal fat decreased quadratically, whereas breast meat lightness (L^* ) and ether extract composition linearly decreased. Dietary dig Lys levels did not show any significant effect on serum metabolites, breast meat cooking loss and water holding capacity. Based on the linear broken-line regression models, the weight gain, feed conversion ratio and breast yield were optimized when dietary dig Lys levels were 0.95%, 1.01% and 1.02% respectively. It is concluded that Lys requirements vary according to what productive parameter is taken for optimization. A minimum of 1.02% dig Lys concentration in the finisher diet is suggested to optimize breast yield, feed efficiency and performance in broiler chickens.

Changes in body composition and meat quality in response to dietary amino acid provision in finishing broilers

In order to control and optimize chicken quality products, it is necessary to improve the description of the responses to dietary amino acid (AA) concentration in terms of carcass composition and meat quality, especially during the finishing period. The aim of this study was to investigate the effects of Lysine (Lys, i.e. a limiting AA used as reference in AA nutrition) and AA other than Lys (AA effect). In total, 12 experimental diets were formulated with four levels of digestible Lys content (7, 8.5, 10 and 11.5 g/kg) combined with either a low (AA-), adequate control (AAc) and high (AA+) amount of other essential AA (EAA) expressed as a proportion of Lys. They were distributed to male Ross PM3 from 3 to 5 weeks of age. No significant AA×Lys interaction was found for growth performance or carcass composition. Body weight and feed conversion ratio were significantly improved by addition of Lys but were impaired in broilers receiving the AA- diets, whereas breast meat yield and abdominal fat were only affected by Lys. No additional benefit was found when the relative amount of other EAA was increased. There was a significant AA×Lys interaction on most of the meat quality traits, including ultimate pH, color and drip loss, with a significant effect of both AA and Lys. For example, AA- combined with reduced Lys level favored the production of meat with high ultimate pH (&gt;6.0), dark color and low drip loss whereas more acid, light and exudative meat (&lt;5.85) was produced with AA+ combined with a low Lys level. In conclusion, growth performance, carcass composition and meat quality are affected by the levels of dietary Lys and AA in finishing broilers. In addition, interactive responses to Lys and AA are found on meat quality traits, leading to great variations in breast pHu, color and drip loss according AA balance or imbalance.

Evaluation of starter dietary digestible lysine level on broilers raised under a sex-separated or straight-run housing regime, part 2: Economics of sex separation and digestible lysine level for maximum returns

The objective of this experiment was to determine the maximum net returns digestible lysine (dLys) levels (MNRL) when maintaining the ideal amino acid ratio for starter diets of broilers raised sex separate or comingled (straight-run). A total of 3,240 Ross 708 chicks was separated by sex and placed in 90 pens by 2 rearing types: sex separate (36 males or 36 females) or straight-run (18 males + 18 females). Each rearing type was fed 6 starter diets (25 d) formulated to have dLys levels between 1.05 and 1.80%. A common grower diet with 1.02% of dLys was fed from 25 to 32 days. Body weight gain (BWG) and feed intake were assessed at 25 and 32 d for performance evaluation. Additionally, at 26 and 33 d, 4 birds per pen were sampled for carcass yield evaluation. Data were modeled using response surface methodology in order to estimate feed intake and whole carcass weight at 1,600 g live BW. Returns over feed cost were estimated for a 1.8-million-broiler complex of each rearing system under 9 feed/meat price scenarios. Results indicated that females needed more feed to reach market weight, followed by straight-run birds, and then males. At medium meat and feed prices, female birds had MNRL at 1.07% dLys, whereas straight-run and males had MNRL at 1.05%. As feed and meat prices increased, females had MNRL increased up to 1.15% dLys. Sex separation resulted in increased revenue under certain feed and meat prices, and before sex separation cost was deducted. When the sexing cost was subtracted from the returns, sex separation was not shown to be economically viable when targeting birds for light market BW.

Digestible lysine requirements of male broilers from 1 to 42 days of age reassessed

Three experiments were conducted separately to estimate the digestible Lys (dig. Lys) requirements of Cobb × Cobb 500 male broilers using different statistical models. For each experiment, 1,200 chicks were housed in 48 floor pens in a completely randomized design with 6 treatments and 8 replicates. Broilers were fed diets with increasing dig. Lys levels from 1 to 12 d (Exp. 1), from 12 to 28 d (Exp. 2), and 28 to 42 d (Exp. 3). Increasing dig. Lys levels were equally spaced from 0.97 to 1.37% in Exp. 1, 0.77 to 1.17% in Exp. 2, and 0.68 to 1.07% in Exp. 3. The lowest dig. Lys diets were not supplemented with L-Lysine and all other essential AA met or exceeded recommendations. In Exp. 3, six birds per pen were randomly selected from each replication to evaluate carcass and breast yields. Digestible Lys requirements were estimated by quadratic polynomial (QP), linear broken-line (LBL), quadratic broken-line (QBL), and exponential asymptotic (EA) models. Overall, dig. Lys requirements varied among response variables and statistical models. Increasing dietary dig. Lys had a positive effect on BW, carcass and breast yields. Levels of dig. Lys that optimized performance using QP, LBL, QBL, and EA models were 1.207, 1.036, 1.113, and 1.204% for BWG and 1.190, 1.027, 1.100, and 1.172% for FCR in Exp. 1; 1.019, 0.853, 0.944; 1.025% for BWG and 1.050, 0.879, 1.032, and 1.167% for FCR in Exp. 2; and 0.960, 0.835, 0.933, and 1.077% for BWG, 0.981, 0.857, 0.963, and 1.146% for FCR in Exp. 3. The QP, LBL, QBL, and EA also estimated dig. Lys requirements as 0.941, 0.846, 0.925, and 1.070% for breast meat yield in Exp. 3. In conclusion, Lys requirements vary greatly according to the statistical analysis utilized; therefore, the origin of requirement estimation must be taken into account in order to allow adequate comparisons between references.

Quantitative estimates of the optimal balance between digestible lysine and the true protein contents of broiler feeds

Typical poultry feed formulation models have been developed for meeting the minimum specifications of the essential amino acids (EAAs), ignoring the importance of providing precise levels of the non-essential amino acids (NEAAs) that are required for maximum performance. Including true protein (TP) values in these models in relation to EAAs can most accurately account for the requirements of all amino acids (AAs) in the ration (essential, non-essential and excess EAAs). Data from recent research reports on the digestible lysine (dLys) requirements for maximum weight gain and minimum feed conversion ratio (FCR) were compiled from the literature. dLys requirements and the TP contents of the feeds were recalculated based on common ingredient composition values. Broken-line linear (BLL) and broken-line quadratic (BLQ) models were fitted to the data and compared. The dLys requirements of broilers (g/kg diet) for body weight gain (BWG) and FCR were found to increase linearly as a function of the true and crude protein contents of the diet. These relationships were not affected by either age or sex. As chickens aged, the dLys requirements decreased. However, the dLys requirement to TP ratio did not change with age for BWG or FCR. For maximum BWG and minimum FCR, the dLys requirements were estimated from the prediction models to be 4.92% ± 0.51 and 5.58% ± 0.70 of the TP level of the diet, using the BLL models, respectively. The good linear relationship between the dLys requirement and TP level allows the prediction of the variables from each other for use in feed formulation to represent the requirements of both EAAs and NEAAs. The dietary dLys requirements were estimated to be lower using the BLL vs. the BLQ models. TP was a better predictor of dLys requirements than crude protein (higher R(2) values).

Influence of source of soybean meal and lysine content of the diet on performance and total tract apparent retention of nutrients in broilers from 1 to 36 days of age

The influence of soybean meal (SBM) source and total Lys content of the diet on performance and total tract apparent retention of nutrients was evaluated in broilers from 1 to 36 d of age. There were 6 treatments arranged factorially with 2 sources of SBM [regular SBM with 46.3% CP (R-SBM) and high-protein SBM with 48.6% CP (HP-SBM)] and 3 Lys:AME(n) ratios (Lys:ME; 380, 415, and 450 mg of total Lys:1,000 kcal of AME(n) from 1 to 21 d; and 312, 338, and 364 mg of total Lys:1,000 kcal of AME(n) from 22 to 36 d of age). From 1 to 36 d of age, broilers fed the HP-SBM diets had higher ADG and better feed:gain ratio (F:G) than broilers fed the R-SBM diets (P < or = 0.001). Both ADG and F:G improved (P < or = 0.05) with increases in the Lys:ME ratio. From 1 to 21 d of age, ADG and F:G (P < or = 0.001) were improved when the Lys:ME ratio increased and the benefits were more pronounced with the diets based on R-SBM. From 22 to 36 d of age, increasing the Lys:ME ratio from 312 to 338 increased ADG (P < or = 0.05) and F:G (P < or = 0.01), but no further improvements were observed when the ratio was increased to 364. The total tract apparent retention of DM and gross energy of the diets were higher (P < or = 0.05) for the HP-SBM than for the R-SBM diets. An increase in the Lys:ME ratio reduced organic matter and N retention (P < or = 0.05). The improvements in growth performance and nutrient retention observed in broilers fed the HP-SBM diets with respect to those fed the R-SBM are consistent with a better availability of nutrients of the high-protein meal. In addition, the results indicate that Lys requirements of broilers are at least, 30, 20, and 8% higher from 1 to 10, 10 to 21, and 21 to 36 d of age, respectively, than current NRC recommendations.

Alpha-aminoadipate delta-semialdehyde synthase mRNA knockdown reduces the lysine requirement of a mouse hepatic cell line

Alpha-aminoadipate delta-semialdehyde synthase (AASS) is the bifunctional enzyme containing the lysine alpha-ketoglutarate reductase (LKR) and saccharopine dehydrogenase activities responsible for the first 2 steps in the irreversible catabolism of lysine. A rare disease in humans, familial hyperlysinemia, can be caused by very low LKR activity and, as expected, reduces the lysine "requirement" of the individual. This concept was applied to a murine hepatic cell line (ATCC, FL83B) utilizing RNA interference (RNAi) to achieve AASS mRNA knockdown. Cells were antibiotic selected for stable transfection of 2 plasmids that express different short hairpin RNA sequences for AASS knockdown. Compared with the wild-type cell line, AASS mRNA abundance was reduced 79.0 +/- 6.4% (P < 0.05), resulting in a 29.8 +/- 5.2% (P < 0.05) reduction in AASS protein abundance, 41.3 +/- 10.0% (P < 0.05) less LKR activity, and a reduction in lysine oxidation by 50.7 +/- 11.8%. To determine the effect of AASS knockdown on the lysine requirement, cells were grown in media containing 12.5, 25.0, 50.0, 100, or 200 micromol/L lysine. Using a segmented model approach for growth rate analysis, the lysine requirement of the cell line with AASS silencing was 43.4 +/- 1.7 micromol/L, approximately 26% lower (P < 0.05), than the lysine requirement of the wild-type cell line. These results indicate AASS knockdown decreases the lysine requirement of the cell via a reduction of lysine catabolism through the saccharopine pathway, providing the initial proof in principle that RNAi can be used to reduce the nutrient requirement of a system.

Increasing dietary lysine increases final pH and decreases drip loss of broiler breast meat

Responses to increased dietary Lys concentrations were evaluated on 1,584 Ross 308 male broilers between 21 and 42 d of age housed according to 2 bird densities. The experimental design was composed of 8 factorial treatments: 2 bird densities (22 or 44 broilers/ 1.7 m(2) pen) x 4 true digestible (TD) Lys levels (0.83, 0.93, 1.03, and 1.13%). There were 6 repetitions per treatment. Birds were weighed individually at d 21 and 42. Feed consumption was recorded per pen. Body weight gain and feed conversion were calculated over the experimental period. Forty-eight broilers per treatment were dissected at 42 d of age. Final pH and drip loss during storage were measured on the pectoralis major. Density adversely affected feed intake (169 +/- 1 and 160 +/- 1 g/d with 22 and 44 birds per pen, respectively, P < 0.05), growth rate (97.4 +/- 0.5 and 91.0 +/- 0.7 g/d, P < 0.05), and feed conversion (1.730 +/- 0.008 and 1.760 +/- 0.006, P < 0.05). Except for feed intake, there was no interaction between the effects of bird density and dietary Lys. An increase in dietary TD Lys from 0.83 to 0.93% resulted in an increased growth rate (from 91.8 +/- 1.6 to 95.5 +/- 0.8 g/d, P < 0.05), improved feed conversion (from 1.783 +/- 0.008 to 1.742 +/- 0.009, P < 0.05), and increased breast meat yield (22.0 +/- 0.1% to 22.7 +/- 0.2%, P < 0.01). Performance and body composition traits were not significantly improved for concentrations of TD Lys higher than 0.93%. However, final breast pH increased from 0.83 up to 1.03% TD Lys in the diet (6.02 +/- 0.01 vs. 5.91 +/- 0.01, P < 0.05), and drip loss correlatively decreased (0.85 +/- 0.03% vs. 1.10 +/- 0.06, P < 0.05). This result opens new way of research for the definition of an amino acid requirement and on metabolic pathways involved in variations of breast muscle pH.

Influence of Canola Meal-Based Diets Supplemented with Exogenous Enzyme and Digestible Lysine on Performance, Digestibility, Carcass, and Immunity Responses of Broiler Chickens

The response of broiler chickens to 2 levels of endo-1,4-beta xylanase and endo-1,3-beta glucanase combination (with and without), 3 levels of digestible Lys (0.8, 0.9, and 1.0%), and 2 levels of canola meal (CM; 20 and 30%) were evaluated in 2 x 3 x 2 factorial arrangement. A total of 2,448 male Hubbard broiler chicks were fed on practical mash diets having 2,750 kcal of ME.kg(-1) and 19.6% CP from 1 to 42 d of age. The BW gain was significantly reduced when 30% CM was added in the diets during 1 to 21 d. Feed:gain and mortality were also observed to be high. No significant effect of enzyme addition or Lys level was observed on feed intake, BW gain, feed:gain, and mortality during the starter phase. When the data were pooled for 42 d, BW gain and feed:gain were unaffected by enzyme addition or Lys levels. A depression in breast weight was observed due to 30% CM or 0.8 and 0.9% digestible Lys at 43 d. Leg weights were significantly depressed by enzyme addition or increasing digestible Lys to 1.0% of the diets. The AME, nitrogen digestibility, and antibody titers against Newcastle and infectious bursal diseases were also unaffected by the dietary treatments. In conclusion, the 30% CM is not recommended in broiler diets especially during starter phase (1 to 21 d). However, the CM may be used up to 30% of the diets during finishing phase. The digestible Lys can be lowered to 0.8% when amino acids in proportion to digestible Lys follow the ideal AA ratio. The glucanase and xylanase cocktail have no pronounced effect on the growth performance, nutrient digestibility, and carcass characteristics.