Impacts of Dietary Lysine and Crude Protein on Performance, Hepatic and Renal Functions, Biochemical Parameters, and Histomorphology of Small Intestine, Liver, and Kidney in Broiler Chickens

The present study aimed to investigate the effects of increasing dietary lysine (Lys) levels with an adequate dietary crude protein (CP) content, as well as the effects of a reduction in dietary CP content with the recommended amino acid (AAs) level, on the performance, blood biochemical parameters, and histomorphology of the duodenum, liver, and kidney in broiler chickens. A total of 500 broiler chickens were randomly distributed into five dietary treatment groups, following a completely randomized design, where, at the beginning, the control group (C) was fed a diet containing the standard CP and Lys levels: 23% CP with 1.44% Lys during the starter period; 21.5% CP with 1.29% Lys during the growing period; and 19.5% CP with 1.16% Lys during the finishing period. The Lys content was increased by 10% above the recommended control basal requirements in the second group (Gr1) and by 20% in the third group (Gr2), while using the same recommended CP percentage as the C group. The fourth group (Gr3) had a 1% lower CP content and the fifth group had a 2% lower CP content than the C group, with the same recommended AA level as the C group. Increasing the Lys content in the Gr1 group improved the broilers' weight gains (p < 0.05) during the starter, growing, and finishing periods. Decreasing dietary CP with the standard AA levels (Gr3 and Gr4) did not significantly affect (p > 0.05) the live weight gain, feed intake, or feed conversion ratio (FCR) of the broilers compared with those fed with the C diet. Blood total bilirubin, direct and indirect bilirubin, triglycerides, cholesterol, low-density lipoprotein (LDL), and very LDL were not different among the experimental groups. However, blood aspartate aminotransferase levels were increased (p < 0.05) in the Gr1 and Gr3 groups compared with the other treatment groups. All dietary treatments decreased the serum creatinine levels (p < 0.05) compared with the C group. The Gr2 broilers had greater serum total protein and globulin (p < 0.05) than those receiving the other treatments. Increasing dietary Lys levels resulted in a significant improvement in duodenum villus height and width (p < 0.05), while the low-CP diets resulted in shorter villi length and width, along with degenerated areas and lymphocytic infiltration. Low dietary CP content induced hepatocyte disorganization and moderate degeneration, along with vacuolated hepatic cells, excessive connective tissue, and lymphocytic infiltration. The cortical regions of the kidney exhibited obvious alterations in the Gr3 and Gr4 groups and large interstitial spaces were found between tubules. Renal tubules in the Gr3 and Gr4 groups were smaller in size and some of these tubules were atrophied. In conclusion, reducing dietary CP levels to 1% or 2% lower than the recommended level did not negatively affect growth performance, inducing minimal influence on the blood metabolic indicators of health status, and resulting in moderate alterations to the histomorphology of the duodenum, liver, and kidney. Furthermore, increasing the Lys content by 10% above the recommended level improved the growth performance, health status, and histomorphology of the duodenum, liver, and kidney in broiler chickens.

Efficiency of lysine utilization by growing meat quail

The objective of present study was to estimate the efficiency of lysine utilization by meat quail of 21 to 35 d of age. A total of 500 meat quails were distributed in a completely randomized design in a 2 × 5 factorial arrangement, with 2 sexes (male and female) and 5 digestible lysine levels (0.714, 0.816, 0.918, 1.020, and 1.122%) and 5 replications of 10 birds each. The variables studied were feather-free body weight (FFBW), feed intake (FI), lysine intake (LysI), feather-free body protein deposition (FFBPD), feather-free body lysine deposition (FFBLysD), feather-free body fat deposition (FFBFatD), feather weight (FW), feather protein deposition, feather lysine deposition, and feather fat deposition. The FFBW, FFBPD, FFBLysD, and FFBFatD were regressed as a function of LysI for each sex to estimate the efficiency of lysine utilization in the feather-free body (ELysFFB), and the individual equations were compared. In addition, a multiple regression without intercept was also used to estimate the ELysFFB and in feathers (ELysF) individually. To compare the ELysFFB obtained by the different methods, the t-statistic was used. There was no effect on sex × lysine level interactions for any variable. The females showed higher FFBW (5.07%) and FFBFatD (26.23%) than males. All variables increased with the level of dietary lysine, with the exception of FI, FW, and the deposition of nutrients within them. The ELysFFB values obtained by simple linear regression and multiple linear regression were 48.0 and 44.6%, respectively. As there was no difference in the efficiencies estimated by the different methodologies, the best estimate of ELysFFB was 46.3%, that is, the average. The best estimate of ELysF was 18.1%, obtained by multiple linear regression.

Transcriptome Analysis and Expression of Selected Cationic Amino Acid Transporters in the Liver of Broiler Chicken Fed Diets with Varying Concentrations of Lysine

Amino acids are known to play a key role in gene expression regulation. Amino acid signaling is mediated via two pathways: the mammalian target of rapamycin complex 1 (mTORC1) and the amino acid responsive (AAR) pathways. Cationic amino acid transporters (CATs) are crucial in these pathways due to their sensing, signaling and transport functions. The availability of certain amino acids plays a key role in the intake of other amino acids, hence affecting growth in young birds. However, the specific mechanism for regulating lysine transport for growth is not clear. In this study, we analyze the transcriptome profiles and mRNA expression of selected cationic amino acid transporters in the livers of broilers fed low and high lysine diets. Birds consumed high-lysine (1.42% lysine) or low-lysine (0.85% lysine) diets while the control group consumed 1.14% lysine diet. These concentrations of lysine represent 125% (high lysine), 75% (low lysine) and 100% (control), respectively, of the National Research Council's (NRC) recommendation for broiler chickens. After comparing the two groups, 210 differentially expressed genes (DEGs) were identified (fold change >1 and false discovery rate (FDR) <0.05). When comparing the high lysine and the low lysine treatments, there were 67 upregulated genes and 143 downregulated genes among these DEGs. Analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) and the Gene Ontology (GO) enrichment analysis show that cellular growth, lipid metabolism and lysine metabolism pathways were among the significantly enriched pathways. This study contributes to a better understanding of the potential molecular mechanisms underlying the correlation between lysine intake, body weight gain (BWG) and feed intake (FI) in broiler chickens. Moreover, the DEGs obtained in this study may be used as potential candidate genes for further investigation of broiler growth customized responses to individualized nutrients such as amino acids.

Exigência de lisina digestível de frangos de corte machos de 22 a 42 dias de idade

RESUMO O objetivo deste estudo foi determinar a exigência de lisina digestível para frangos de corte machos sob as características de desempenho, composição corporal e rendimento de carcaça dos animais, de 22 a 42 dias de idade. As dietas diferiram quanto aos níveis de lisina digestível, mantendo-se a relação dos demais aminoácidos com a lisina. Foram utilizados seis níveis de lisina digestível: 0,88%; 0,96%; 1,05%; 1,13%; 1,22%; e 1,30%. Distribuídos em 36 unidades experimentais de 36 aves cada, 1296 animais da linhagem Cobb - 500® tiveram as seguintes características de desempenho avaliadas: consumo de ração (CR), peso corporal (PC), ganho de peso (GP), conversão alimentar (CA), viabilidade criatória (VC) e índice de eficiência produtiva (IEP). Aos 42 dias de idade, foram selecionadas ao acaso cinco aves para avaliação do rendimento de carcaça, e duas para avaliação da composição corporal. A CA, o IEP e o rendimento de peito foram influenciados, sendo sua exigência de 1,30%, sugerindo que níveis maiores de lisina digestível que as recomendações utilizadas como base neste estudo (1,13%) trouxeram benefícios aos animais sobre essas características.

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.

High doses of phytase on growth performance and apparent ileal amino acid digestibility of broilers fed diets with graded concentrations of digestible lysine

Two experiments of the same design were conducted to determine the influence of phytase on performance and apparent ileal digestibility (AID) of amino acids in broilers fed graded concentrations of digestible lysine (dgLys). Cobb 400, male broilers were allocated to 1 of 16 diets consisting of 4 basal diets formulated at 80, 88, 96, or 104% of the Cobb 400 dgLys requirements for each feeding phase. Phytase was included in each basal diet at 0, 750, 1,500, or 3,000 phytase units (FTU)/kg. In Exp. 1, 33 birds/pen from hatch to day 42 were fed a 2-phase feeding program with 12 replicate pens/diet. In Exp. 2, there were 25 birds/pen from hatch to day 21 and 8 replicate pens/diet. Data were analyzed as a 4 × 4 factorial and means separated using orthogonal contrasts. In Exp. 1, feed intake (FI) increased (quadratic, P < 0.05) as dgLys increased in the diet. Body weight gain (BWG) increased (quadratic, P < 0.05) as dgLys concentration or phytase dose increased in the diet. As phytase dose increased in the diet, feed conversion ratio (FCR) was improved in a linear or quadratic (P < 0.05) manner depending on the dgLys concentration of the diet (dgLys × phytase, P<0.05). In Exp. 2, FI linearly (P < 0.05) increased as dgLys increased in the diet. Increasing the concentration of dgLys or phytase in the diet increased (quadratic, P < 0.05) BWG and improved (quadratic, P < 0.05) FCR. The AID of most amino acids was influenced by a dgLys × phytase interaction (P < 0.05), except threonine, valine, tryptophan, serine, cysteine, or leucine (linear or quadratic effect of phytase, P < 0.05), where phytase improved the AID in birds fed diets containing 80, 88, or 96% of the dgLys requirement, but not birds fed 104%. The predicted dgLys requirement to maximize performance, carcass, and digestible lysine intake was 97.6 to ≥ 104%. The predicted dose of phytase to maximize BWG or FCR was between 1,990 and 2,308 FTU/kg, regardless of the dgLys concentration in the diet. The predicted dose of phytase to maximize carcass weight was between 1,527 and 2,658 FTU/kg of diet and to maximize breast weight was 0 to ≥ 3,000 FTU/kg diet, depending on the dgLys concentration in the diet. In conclusion, optimal performance in the absence of phytase could be achieved at much lower levels of lysine in the presence of phytase.

Box-Behnken optimisation of growth performance, plasma metabolites and carcass traits as influenced by dietary energy, amino acid and starch to lipid ratios in broiler chickens

A Box-Behnken designed study was completed to predict growth performance, carcass characteristics and plasma hormone and metabolite levels as influenced by dietary energy, amino acid densities and starch to lipid ratios in male broiler chickens. The design comprised three dietary energy densities (11.25, 12.375 and 13.5 MJ/kg), three digestible lysine concentrations (9.2, 10.65 and 12.1 g/kg) and three starch to lipid ratios (4.5, 12.25 and 20.0) in broiler diets based on maize and soybean meal. Each of thirteen dietary treatments was offered to 10 replicates of 15 birds per replicate floor pen or a total of 1,950 Ross 308 male broiler chickens from 21 to 35 days post-hatch. Increasing dietary energy decreased feed intake with a quadratic relationship between feed intake and dietary standardised ileal digestible (SID) Lys concentrations, where increasing SID Lys initially increased and then depressed feed intake. Increasing dietary amino acid density increased body weight gain and carcass weight; however, dietary energy did not influence body weight gain, carcass and breast meat weight. Feed efficiency was positively influenced by energy and amino acid densities but negatively influenced by starch to lipid ratios and energy and amino acids had more pronounced impacts than starch to lipid ratios. This study indicated that both energy and amino acid densities regulate feed intakes in broiler chickens. Body weight gain of modern broiler chickens is more responsive to amino acid densities; nevertheless, dietary energy density continues to play an important role in protein utilisation, as reflected in significantly reduced plasma uric acid levels.

Effects of reduced digestible lysine density on myopathies of the Pectoralis major muscles in broiler chickens at 48 and 62 days of age

Quantitative control of nutrient intake may decrease the incidence of wooden breast (WB) and white striping (WS) myopathies with some impairment of live performance. Two experiments (Exp) utilizing Yield Plus × Ross 708 male broilers were conducted to determine if a reduction in myopathies may be obtained through a qualitative approach by reducing digestible lysine (dLys) density. All birds received an identical starter diet until 11 d of age. In Exp 1 (63 pens; 22 birds/pen), each pen was then randomly assigned to 1 of the following 7 dietary treatments (TRT) for a 47 d production period. Seven dietary treatments were provided for the grower 1 (G1; 12 to 18 d of age) and grower 2 (G2; 19 to 26 d of age) phases: 1) 100% of primary breeder recommendations for dLys throughout Exp; 2) 85% of TRT 1 dLys for G1; 3) 85% of TRT 1 dLys for G2; 4) 85% of TRT 1 dLys for G1 and G2; 5) 75% of TRT 1 dLys for G1; 6) 75% of TRT 1 dLys for G2; 7) 75% of TRT 1 for G1 and G2. In Exp 2 (24 pens; 30 birds/pen), birds were randomly assigned to 1 of the following 4 dietary TRT (Table 2) during a 61 d production period. Four dietary treatments were provided for the grower (G; 12 to 28 d) and finisher 1 (F1; 29 to 40 d of age) phases: 1) 100% of primary breeder recommendations for dLys 2) 85% of TRT 1 dLys for G; 3) 85% of TRT 1 dLys for F1; 4) 85% of TRT 1 dLys for G and F1; thereafter, birds received common finisher 1 (Exp 1: 27 to 42 d of age), finisher 2 (Exp 2: 41 to 48 d of age) and withdrawal (Exp 1: 43 to 47 d of age; Exp 2: 49 to 61 d of age) diets. Ideal amino acid ratios were not maintained in reduced dLys diets in either Exp. At 48 (Exp 1; 18 birds/pen) and 62 (Exp 2; 30 birds/pen) d of age, selected birds were processed and fillets were visually scored for WB and WS. No differences (P > 0.05) in cumulative live performance responses between TRT 1 and the remaining TRT were observed in either Exp. In Exp 1, the incidence of severe WB (20.8%) and WS (42.3%) at 48 d of age among birds receiving TRT 7 was reduced (P < 0.01) compared with TRT 1 (WB: 36.6%; WS: 64.3%), at the expense of reduced (P = 0.003) breast weights and yield. In Exp 2, the incidence of severe WB (18.8%) and WS (17.8%) at 62 d of age for birds receiving TRT 4 was reduced (P < 0.05) compared with TRT 1 (WB: 39.3%; WS: 38.3%), without any detrimental effects on processing characteristics. These results indicate that altering dietary dLys during critical periods of the growth trajectory may be a viable strategy for reducing the incidence and severity of WB and WS.

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.

Occurrence of white striping and wooden breast in broilers fed grower and finisher diets with increasing lysine levels

Two experiments were conducted to evaluate the prevalence and severity of white striping (WS) and wooden breast (WB) in breast fillets from broilers fed diets with increasing digestible Lysine (dLys) from 12 to 28 d (Exp. 1) and from 28 to 42 d (Exp. 2). Trials were sequentially conducted using one-d-old male, slow-feathering Cobb 500 × Cobb broilers, both with 6 treatments and 8 replicates. Increasing dLys levels were equally spaced from 0.77 to 1.17% in Exp. 1 and from 0.68 to 1.07% in Exp. 2. The lowest dLys diet was not supplemented with L-Lysine (L-Lys) in either one of the studies and all other essential amino acid (AA) met or exceeded current commercial recommendations such that their dietary concentrations did not limit broiler growth. Four birds per pen were randomly selected from each replication and processed at 35 and 42 d in Exp. 1 and Exp. 2, respectively. Deboned breast fillets (Pectoralis major) were submitted to a 3 subject panel evaluation to detect the presence of WS and WB, as well as to provide scores of WS (0-normal, 1-moderate, 2-severe) and WB (0-normal, 1-moderate light, 2-moderate, 3-severe). Increasing the level of dLys had a positive effect on BW, carcass, and breast weight, as well as breast yield. White striping and WB prevalences were 32.3 and 85.9% in Exp. 1 and 87.1 and 89.2% in Exp. 2. Birds fed diets not supplemented with L-Lys had the lowest average WS and WB scores (0.22 and 0.78 in Exp. 1 and 0.61 and 0.68 in Exp. 2). White striping and WB presented linear responses to performance variables in Exp. 1, whereas quadratic responses were observed for all variables in Exp. 2. In conclusion, increasing the level of dLys improved growth performance and carcass traits as well as induced the occurrence and severity of WS and WB lesions.

Combined effect of divergent selection for breast muscle ultimate pH and dietary amino acids on chicken performance, physical activity and meat quality

Responses to changes in dietary Lys and other essential amino acid (AA) concentrations were evaluated in 480 male and female broilers originating from two lines divergently selected for high (pHu+) or low (pHu-) ultimate pH (pHu) of breast muscle. The two genetic lines were fed with two grower isoenergetic diets differing in both true digestible Lys (control=10.2 g/kg and experimental=7.0 g/kg) and amounts of other essential AA calculated in relation to Lys, which were sufficient for the control diet or in excess for the experimental diet. There were six repetitions per treatment. Birds were weighed individually at days 0, 21, 28 and 43. Feed consumption was recorded per pen and feed conversion was calculated over the growing period. The physical activity and walking ability of broilers were recorded during the whole rearing period. Breast and leg yield, and abdominal fat percentage were measured at 43 days of age, as were pHu, color, drip and cooking loss, Warner-Bratzler shear force, and curing-cooking yield of the breast Pectoralis major and pHu of the thigh Sartorius muscle. Divergent selection greatly affected most breast meat quality traits without significantly changing growth rate or feed efficiency. When subjected to a variation in dietary intake of AA, birds from the two genotypes responded in a similar way in terms of animal's growth, feed efficiency, body composition and meat quality traits. Although line and diet did not affect physical or feeding activities of the broilers, a significant effect of line-by-diet interaction was observed on gait score. Contrary to the pHu- birds, the walking ability of pHu+ birds was impaired when fed the control diet that favored growth and breast muscle development and limited storage of carbohydrate in muscle.

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).