Lys Requirement Research Articles

Optimal sulfur amino acid to lysine ratio for post weaning piglets reared under clean or unclean sanitary conditions.

Two 14-day experiments, each with 90 (Duroc × [Yorkshire × Landrace]; 7.3 ± 0.6 kg) piglets, were conducted to determine the optimum sulfur amino acid (SAA) to lysine (Lys) ratio (SAA:Lys) for piglets when reared under clean or unclean sanitary conditions using performance and non-performance response criteria. Piglets were randomly assigned to the following dietary treatments. The basal diet contained 1.18% standardized ileal digestible (SID) Lys, and the SAA:Lys was 52%. In diets 2 to 5, the basal diet was supplemented with 4 graded levels of dl-Met to make SAA:Lys of 56%, 60%, 64% and 68%. In Exp. 1, piglets were housed in disinfected clean room. In Exp. 2, piglets were housed in a room previously occupied by other pigs and was not disinfected. On the last day, blood was collected to measure plasma urea nitrogen (PUN) and one pig per pen was euthanized to collect jejunal tissue to measure villus height (VH), crypt depth (CD), and VH:CD. In Exp. 1, increasing SAA:Lys linearly and quadratically increased VH and VH:CD (P < 0.05). In Exp. 2, increasing SAA:Lys linearly increased (P < 0.05) VH and VH:CD and linearly and quadratically decreased PUN (P < 0.05). Estimated PUN and VH-based optimum SAA:Lys requirements for clean and unclean sanitary condition were 60%, 63% and 66%, respectively.

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.

Changes of serum free amino acids in eventing horses at rest and during exercise in response to dietary protein

Although there are published expertise about serum free amino acids, to the knowledge of the authors no data were reported on eventing horses. In this way, it is important to study the concentration of dietary protein and serum free amino acid during exercise in order to improve nutritional strategies. The aim of this study was to investigate the concentration of the serum free lysine (Lys), threonine (Thr), leucine (Leu), isoleucine (Ile) and valine (Val) of eventing horses fed diets with different levels of protein at before and during exercise. Twenty-four Brazilian Sport Horses trained for eventing were used in a randomized block design with 4 diets (7.5%, 9.0%, 11.0% and 13.0% of CP) and 6 repetitions (horses). Horses were blocked according to their experience in competitions. The test protocol consisted of a warm up of walking and trotting and then a gallop starting at 6.0 m/s with increases in speed of 1 m/s every minute up to 10 m/s. Venous blood samples were collected before the test and during exercise. Concentration of Lys, Thr, Leu, Ile and Val from diets and serum free amino acids were determined by HPLC analysis. Total intake values of Lys, Thr, Leu, Ile and Val were affected by dietary protein levels. Differences on the serum free concentrations of Lys, Leu, Ile and Val as a function of the sampling time were observed. The Lys requirement for athletic horses appear to be lower than what is currently proposed. Moreover, the effect of exercise on serum free Lys, Leu, Ile and Val concentration, may be interpreted as an indicator of these amino acids metabolic response.

SID lysine requirement of immunologically and physically castrated male pigs during the grower, early and late finisher periods.

The main objective of this experiment was to determine the standardized ileal digestible (SID) Lys requirement of immunologically castrated (IC) and physically castrated (PC) male pigs during 3 growth phases. An additional objective was to compare the ADFI of PC and IC after the second anti-gonadotropin releasing factor (GnRF) injection. Three hundred male pigs (PIC 359 × C29), 150 each of IC and PC, were allotted to 1 of 5 treatments: 80, 90, 100, 110, or 120% of the estimated Lys requirement using the modeling program. Pigs remained on the same treatment throughout each of the 3 phases. Lysine requirements were determined at 3 stages of growth starting at a BW of 30.0 ± 0.8, 64.7 ± 1.4, and 111.9 ± 1.9 kg for IC and 32.4 ± 0.6, 69.8 ± 1.0, and 114.5 ± 1.3 kg for PC. Anti-GnRF injections were administered to IC at 11.5 and 19 wk (average BW = 96.3 ± 1.8 kg) of age. The one-slope broken line regression and quadratic plateau models were used, and the best model was selected based on the Akaike information criterion. The IC SID Lys requirements based on ADG were 1.03, 0.97, and 0.55% and for G:F, the requirements were 0.99, 0.72, and 0.55% for phases 1, 2, and 3, respectively. For PC, the SID Lys requirements based on ADG were 0.86, 0.62, and 0.47% and for G:F were 0.86, 0.58, and 0.47% for phases 1, 2, and 3, respectively. Immunologically castrated pigs had greater SID Lys requirements for phases 1 and 2 compared to PC (0.17 and 0.35% points greater for ADG and 0.13 and 0.14% points greater for G:F for phases 1 and 2, respectively). After the second injection, when IC pigs are believed to become physiologically more similar to PC pigs, the SID Lys requirements continue to be greater for IC (0.55 vs. 0.47% for both ADG and G:F). The ADFI of IC increased 4 d after the second injection relative to PC. By 2 wk post second injection, the ADFI of IC exceeded that of PC ( < 0.05). Adopting immunological castration as a management tool requires an understanding that IC need to be fed differently compared to PC, to maximize growth performance. Immunologically castrated pigs have a greater SID Lys requirement throughout the grower and finishing periods compared to the PC.

Early dietary amino acid restrictions and flaxseed oil supplementation on the leanness of pigs and quality of pork: Growth performance, serum metabolites, carcass characteristics, and physical and sensory characteristics of pork

A total of 64 pigs (Yorkshire) were used to investigate the effect of early dietary amino acid (AA) restrictions [100 or 80% of the 2012 NRC standardized ileal digestible (SID) Lys requirements during the grower and finisher-1 phases] and flaxseed oil supplementation [0 or 3% (+2% poultry fat)] in a 2×2 factorial arrangement of treatments on grower-finisher pigs. At 24.7±0.5kg body weight (BW), pigs were randomly assigned to 4 grower diets with 4 gilt and 4 castrated male pens/treatment and 2 gilts or 2 castrated males/pen, and switched to fnisher-1 diets when they reached 51.2±0.3kg. Pigs were offered common finisher-2 diets after 80.0±0.4kg, and those received 0 or 5% lipids during the grower and finisher-1 phases were continued to receive 0 or 5% lipids. Ultrasound backfat measurements and blood samples were collected at the end of the grower, finisher-1, and finisher-2 phases, and pigs were harvested at 110.5±0.5kg to assess carcass traits and physical and sensory characteristics of pork. During the grower phase, although pigs consumed less feed, SID Lys, and digestible energy (DE; P<0.015), their average daily BW gain was not really depressed by the dietary AA restrictions. During the finisher-1 phase, however, pigs fed the AA restricted diets had greater BW gain (P=0.042) and utilized SID Lys more efficiently (P<0.001) for BW gain than those fed the unrestricted diets. Pigs fed the diets supplemented with lipids had lower feed intake (P=0.007) but greater BW gain (P =0.03) during the grower phase, and their BW gain:feed (P<0.045) was improved during the all phases of production. Overall BW gain was not affected by the early dietary AA restrictions, but overall efficiency of feed, SID Lys, or DE utilization for BW gain (P<0.005) was improved by the AA restrictions. Similarly, the early dietary AA restrictions had no effect on fat-free lean (FFL) gain but increased FFL gain:SID Lys (P<0.001) and tended to increase FFL gain:DE (P=0.095). Serum urea-N (P<0.026) at the end of the grower and finisher-1 phases was reduced, and serum glucose (P=0.027) at the end of the grower phase was increased by the dietary AA restrictions. The dietary lipids tended to increase and increased serum triglycerides at the end of the grower (P=0.075) and finisher-1 and 2 (P<0.018) phases, respectively, and reduced urea-N (P=0.037) at the end of the finisher-2 phase. At the end of the finisher-1 phase, the dietary lipids increased serum cholesterol in pigs fed the unrestricted diet but had no effect on those fed the AA restricted diet (AA restrictions x lipid supplementation, P=0.029). The dietary AA restrictions tended to reduce the initial tenderness (P<0.057) and reduced flavor intensity (P=0.048) of pork slightly. Belly firmness (P<0.001) was reduced and off-flavor (P=0.007) was increased slightly by the dietary lipids. There was no effect of dietary treatments on ultrasound backfat. In conclusion, the dietary lipids improved BW gain:feed but reduced belly firmness and increased off-flavor slightly. The dietary AA restrictions had no effect on overall BW gain or FFL gain but improved overall efficiency of AA and DE utilization for BW gain and FFL gain.

Evaluation of the digestible lysine requirements in female turkeys from 0 to 68 days of age

Over the past years, turkey meat has gained a prominent position in the global market. As lysine (Lys) is among the main essential amino acids (AA) for protein deposition in the carcass, defining Lys requirements can contribute to improving the performance and carcass yield of turkey for meat production. Thus, the objective of this study was to evaluate if the digestible Lys levels proposed by breeder’s guidelines are adequate to achieve the best performance in the used rearing and feed conditions of this study. In each phase, 800 female turkeys of the BUT (British United Turkey) hybrid strain were used. The turkeys were distributed in a completely randomized design in experiment 1 (initial phase: 0–25 d) and in a randomized block design in experiment 2 (growth phase: 26–48 d) and experiment 3 (finishing phase: 49–68 d). The treatments consisted of graded levels of digestible Lys with eight replications of 20 turkeys each. The digestible Lys levels tested were 13.6, 14.5, 15.8, 16.9 and 18.2g/kg in the initial phase; 12.2, 13.2, 14.4, 15.4 and 16.2g/kg in the growth phase; and 9.7, 10.4, 11.4, 12.1 and 13.7g/kg in the finishing phase. The average daily gain (ADG), average daily feed intake (ADFI), feed efficiency (FE) and carcass yield (CY) were evaluated. The ADG, FE and CY data were improved by the digestible Lys levels (P<0.05), and the data were adjusted to the quadratic and broken line functions. The digestible Lys level was estimated by the first intercept of the quadratic function with the plateau of the broken line function. At the end of experiment 3, the CY was evaluated (at 68 d). The digestible Lys level for better ADG and FE were, respectively, 16.69g/kg and 16.55g/kg in the initial phase, 14.25g/kg and 14.15g/kg in the growth phase, and 12.23g/kg and 12.07g/kg in the finishing phase. The digestible Lys level for CY was 12.32g/kg. The current study concludes that digestible Lys levels are in the range of the nutritional guidelines for the strain used, except in the initial phase. Due to the difference in the initial recommendation, these levels should be validated in further investigations through performance trials.

Feeding behavior of growing-finishing pigs reared under precision feeding strategies.

The feeding behavior of growing-finishing pigs reared under precision feeding strategies was studied in 35 barrows and 35 females (average initial BW of 30.4 ± 2.2 kg) over 84 d. Five different feeding programs were evaluated, namely a conventional 3-phase program in which pigs were fed with a constant blend of diet A (high nutrient density) and diet B (low nutrient density) and 4 daily phase-feeding programs in which pigs were fed daily with a blend meeting 110, 100, 90, or 80% of the individual Lys requirements. Electronic feeder systems automatically recorded the visits to the feeder, the time of the meals, and the amount of feed consumed per meal. The trial lasted 84 d and the database contained 59,701 feeder visits. The recorded database was used to calculate the number of meals per day, feeding time per meal (min), intervals between meals (min), feed intake per meal (g), and feed consumption rate (feed intake divided by feeding time per meal, expressed in g/min) of each animal. The feeding pattern was predominantly diurnal (73% of the feeder visits). Number of meals, duration of meals, time between meals, feed consumed per meal, and feed consumption rate were not affected by the feeding programs. The females ingested 19% less feed per meal and had a 6% lower feed consumption rate in comparison with the barrows ( < 0.05). Pig feeding behavior was not correlated with diet composition. However, feed efficiency was negatively correlated with amount of feed consumed per meal ( = -0.38, < 0.05) and feed consumption rate ( = -0.44, < 0.05). Feed consumption rate was also negatively correlated with protein efficiency ( = -0.44, < 0.05). Multivariate analysis indicated that feed consumption rate and number of meals per day are the variables related most closely to pig production performance results. Current results indicate that using precision feeding as an approach to reduce Lys intake does not interfere with the feeding behavior of growing-finishing pigs.

Reduction of dietary lysine increases free glutamate content in chicken meat and improves its taste.

Taste is a crucial factor of meat quality, and amino acids are important taste-active components in meat. Here, the effects of dietary lysine (Lys) content on taste-active components in meat, especially free glutamate (Glu), were investigated. Twenty-eight-day-old broilers (Gallus gallus) were fed diets with graded Lys content of 90% or 100% of the recommended Lys requirement, (according to the National Research Council, ) for 10 days. Free amino acid content in meat and sensory scores of meat soup were estimated. Free Glu content, the main taste-active component of meat, was significantly increased by a reduction of dietary Lys. Compared with the Lys 100% group (control), free Glu concentrations of meat were increased by 35.7% in the Lys 90% group (P < 0.05). In addition, free glycine, valine, isoleucine, leucine, histidine and threonine concentrations of meat were significantly increased in the Lys 90% group (P < 0.05). Sensory evaluation of meat soup made from the Lys 100% and 90% groups indicated different meat tastes. Sensory scores of taste intensity, umami and kokumi tastes were significantly higher in the Lys 90% group. These results suggest that a reduction of dietary lysine increased free glutamate content in meat and improved its taste.

Effect of a lysine depletion-repletion protocol on the compensatory growth of growing-finishing pigs.

The effect of Lys restriction followed by a repletion period on the performance of growing pigs was studied during 3 feeding phases, each lasting 28 d. A total of 47 castrated male pigs (G Performer 8.0 × Fertilis 25 pigs; Genetiporc Inc., Saint-Bernard, QC, Canada; initial BW of 26.7 ± 2.7 kg) were given each d 70% or 100% of their Lys requirements according to 1 of the following 5 sequences: 70-70-70, 70-70-100, 70-100-70, 70-100-100, or 100-100-100 (for each sequence, numbers indicate the Lys supply percentage in phase 1, 2, and 3, respectively). Individual Lys requirements were estimated daily on the basis of each pig's actual BW and feed intake and BW gain patterns obtained by regression using each pig's historical data. At the end of phase 1, the pigs given 100% of their Lys requirements had higher ADFI ( = 0.01), ADG ( < 0.01), and average daily protein deposition ( < 0.01) than did the pigs given 70% of their requirements. Similar results were observed during phases 2 and 3. At the end of phase 2, the pigs in the 70-100 sequence did not display any compensatory response, given that their ADFI, ADG, and average daily protein deposition did not differ from those of the pigs in the 100-100 sequence. Similar results were observed during phase 3. Although no compensatory growth was observed during the growing phases, the fact that the pigs in the 70-100-100 treatment were able to catch up in terms of BW and body protein mass to the pigs in the 100-100-100 sequence could indicate that a small degree of compensation did occur; these research results cannot ascertain that any compensatory growth occurred.

Validation of the Lysine Requirement as Reference Amino Acid for Ideal In-Feed Amino Acid Ratios in Modern Fast Growing Meat-Type Chickens

Nitrogen (N) balance studies were conducted with male growing broiler chickens to reevaluate the lysine (Lys) requirement of a modern broiler strain (Ross 308), making use of eight diets with graded crude protein (CP) supply (6% - 34% CP as-fed). Wheat, soy protein concentrate, wheat gluten, fishmeal and crystalline amino acids (AAs) were the protein sources in the experimental diets with Lys as limiting AA. Following an adaptation period of five days, two consecutive excreta collection periods (2 × 5 d) were conducted: 10 - 20 d of age (starter period) and 25 - 35 d of age (grower period). Statistical evaluation of N balance data utilized an exponential modelling approach. Based on different dietary Lys efficiency, Lys requirement data were derived by modelling depending on average body weight (BW) during starter and grower period and targeted body protein deposition (PD), respectively. In addition, the influence of graded feed intake was taken into account. For the starter period at 600 g BW and assumed 10 g daily body PD, Lys requirement data between 741 mg and 823 mg per day were observed. The corresponding Lys in-feed concentration was 1.06% and 1.18%, dependent on supposed Lys efficiency at 70 g daily feed intake. For the grower period (average BW 1800 g), 1272 mg to 1473 mg Lys per day was needed to yield 16.5 g daily PD. The corresponding required Lys in-feed concentration was between 0.85% and 0.94% Lys for 150 g daily feed intake.

Growth performance of male broilers fed diets varying in digestible threonine to lysine ratio from 1 to 14 days of age

Summary Threonine (Thr) is the third limiting amino acid for broilers fed corn-soybean meal–based diets. Digestible Thr to lysine (Lys) ratios utilized by commercial nutritionists vary from 0.63 to 0.68 in the starter period. Low Thr to Lys ratios used during the early growth period can limit performance. This study examined growth responses of broilers provided experimental diets varying in digestible Thr from 1 to 14 d of age. Dietary treatments were formulated at 8 digestible Thr to Lys ratios (0.55, 0.58, 0.61, 0.64, 0.67, 0.70, 0.73, and 0.76). Two diets (dilution and summit) consisting of corn and soybean meal were formulated to be adequate in all other amino acids with the exception of Thr and Lys. All diets were formulated to contain 1.13% digestible Lys, which is slightly below the digestible Lys requirement for male broilers from 1 to 14 d of age. Digestible Thr to Lys ratios were estimated using broken-line methodology. Linear (P = 0.003) and quadratic (P = 0.005) increases in body weight gain (BWG) were observed for broilers fed progressive additions of digestible Thr. Additionally, linear (P

Evaluation of the effects of crude protein and lysine on the growth performance of two commercial strains of broilers using meta-analysis

A meta-analysis was conducted to evaluate the effects of crude protein (CP) and Lys on feed intake (FI; g/broiler chicken per day), average daily gain (ADG; g/broiler per day), and feed efficiency (FE) of broilers of Ross and Cobb strains during the first 21 d of age. A series of criteria was set to search the literature and a database was extracted and used to generate 6 different data sets: (1) male and female broilers of Ross and Cobb strains (n=169); (2) Ross and Cobb male broilers (n=124); (3) Ross males and females (n=80); (4) Cobb males and females (n=89); (5) Ross males (n=64); and (6) Cobb males (n=60). Each of these 6 data sets was analyzed separately for the effects of CP and Lys on FI, ADG, and FE. All models were able to demonstrate a linear effect of Lys (P≤0.08) except in 1 case, while a quadratic effect for all models was highly significant (P≤0.001). However, the results for CP level were not as consistent as for Lys. The FE response was more affected by CP level than were FI and ADG. The models developed showed that the interaction between CP and Lys was an important factor affecting broiler growth performance (P≤0.06 except for 2 cases). Results showed that the optimal value of Lys was increased by an increase in CP level, though its proportion to CP (% of CP) decreased. The Lys levels required to maximize FI, ADG, and FE in a diet containing 170g CP for the first group (male and female broilers of Ross and Cobb strains) were 11.3, 12.2, and 12.8, while these values for a diet containing 245g CP increased to 13.4, 14.2, and 14.5g/kg of diet, respectively. By comparing results from the different data sets, it was concluded that the Lys requirement for males is greater than for females. Optimization of the models for all data groups showed that Lys required for maximum ADG was greater than for FI and was greatest for maximum FE. The results of this study illustrate that dietary CP level, desired response (FI, ADG, and FE), sex, and strain are important factors affecting the Lys requirement of broilers.

Optimal lysine:DE ratio in growing pigs is independent of starch or fat as main energy source at two energy intake levels1

In a 2 × 2 factorial arrangement, 28 growing boars (initial BW of 24.7 ± 1.5 kg) were used to examine the effects of energy source (high starch vs. high fat) and DE level (2.2 vs. 2.7 times the DE requirements for maintenance) on Lys requirements. Pigs were allotted to 1 of 4 dietary treatments. A within-animal Lys titration technique was used to assess the responses to changes in Lys to energy ratio. The amount of apparent ileal digestible Lys in the diet decreased stepwise from 1.74 to 0.5 g/MJ DE in 8 equidistant steps of 3 d each. From 48-h urinary nitrogen excretion, the optimal Lys to energy ratio was estimated for each pig using a linear-plateau model. Feces were collected quantitatively over 27 d to determine apparent total tract digestibility (ATTD) of nutrients. The DE to ADG ratio, but not DE intake and ADG, tended ( < 0.1) to be 4% lower in the high-starch group than in the high-fat group. The ATTD of energy and CP tended ( < 0.1) to be lower (0.8% and 0.9% units, respectively) at the high DE level. The ATTD of energy was 2.2% units greater ( < 0.001) for pigs fed the high-starch diet, but the ATTD of CP was not affected by ES. Estimates for the intercept (21.2% to 22.8%), slope (57.4 to 59.6), transition point (0.84 to 0.86 g Lys/MJ DE), and plateau (70.6% to 72.3%) of the linear-plateau Lys titration curves were not affected by the dietary treatments. In conclusion, ES does not affect Lys requirements in growing pigs regardless the level of DE intake.

Simultaneous determination of standardized ileal digestible tryptophan and lysine for barrows from 15 to 30 kg live weight

The digestible amino acid (AA) determination of ingredients, or experimental diets, are essential in obtaining the real levels of AA that are being studied, as well as of other indispensable AA, because the lack of a single indispensable AA may limit pig growth performance. Two experiments were conducted to determine the optimum levels and the ideal ratio of standardized ileal digestible (SID) Trp and Lys for barrows from 15 to 30kg of live weight. The first experiment (Exp. 1) was conducted to determine the SID AA content of the basal diet used in the growth performance study (Exp. 2). Ten crossbred barrows (21.5±1.6kg live weight) were used in Exp. 1. Pigs were fed a basal diet and a protein free diet to determine the SID of Trp, Lys, and all other indispensable AA of the basal diet. In Exp. 2, 64 barrows (15.0±1.6kg) were allotted to 16 diets in a 4×4 factorial arrangement of treatments (1.55, 1.85, 2.15, and 2.45g SID Trp and 9.72, 11.12, 12.52, and 13.92g SID Lys/kg) with 4 replications per treatment. In both Exp. 1 and 2, each pig was considered as an experimental unit. Growth performance, Longissimus muscle (LM), backfat thickness, and plasma urea nitrogen (PUN) were evaluated. Average daily feed intake and average daily gain increased linearly (P<0.05) with increasing levels of SID Trp. There was a quadratic effect (P=0.04) of dietary SID Trp and Lys levels on the gain:feed, and the optimal levels were estimated to be 2.1 (0.65g/Mcal ME) and 11.98g/kg (3.71g/Mcal ME), respectively, resulting in a SID Trp:Lys of 17.5:100. A quadratic effect of SID Trp (P=0.021) and Lys (P=0.026) levels on LM was observed, and the optimum levels were 2.08 and 11.36g/kg diet, respectively, with a Trp:Lys of 18.3:100. The amount of PUN decreased linearly (P=0.004) as SID Lys increased. For pigs used in our study (between 15 and 30kg live weight), the SID Trp and SID Lys requirements are 2.10 and 11.98g/kg, respectively. The corresponding Trp:Lys are 17.5:100.

Effects of standardized ileal digestible tryptophan: lysine ratio on growth performance of nursery pigs.

Two experiments were conducted to estimate the standardized ileal digestible (SID) Trp:Lys ratio requirement for growth performance of nursery pigs. Experimental diets were formulated to ensure that lysine was the second limiting AA throughout the experiments. In Exp. 1 (6 to 10 kg BW), 255 nursery pigs (PIC 327 × 1050, initially 6.3 ± 0.15 kg, mean ± SD) arranged in pens of 6 or 7 pigs were blocked by pen weight and assigned to experimental diets (7 pens/diet) consisting of SID Trp:Lys ratios of 14.7%, 16.5%, 18.4%, 20.3%, 22.1%, and 24.0% for 14 d with 1.30% SID Lys. In Exp. 2 (11 to 20 kg BW), 1,088 pigs (PIC 337 × 1050, initially 11.2 kg ± 1.35 BW, mean ± SD) arranged in pens of 24 to 27 pigs were blocked by average pig weight and assigned to experimental diets (6 pens/diet) consisting of SID Trp:Lys ratios of 14.5%, 16.5%, 18.0%, 19.5%, 21.0%, 22.5%, and 24.5% for 21 d with 30% dried distillers grains with solubles and 0.97% SID Lys. Each experiment was analyzed using general linear mixed models with heterogeneous residual variances. Competing heteroskedastic models included broken-line linear (BLL), broken-line quadratic (BLQ), and quadratic polynomial (QP). For each response, the best-fitting model was selected using Bayesian information criterion. In Exp. 1 (6 to 10 kg BW), increasing SID Trp:Lys ratio linearly increased ( 0.05) ADG and G:F. For ADG, the best-fitting model was a QP in which the maximum ADG was estimated at 23.9% (95% confidence interval [CI]: [<14.7%, >24.0%]) SID Trp:Lys ratio. For G:F, the best-fitting model was a BLL in which the maximum G:F was estimated at 20.4% (95% CI: [14.3%, 26.5%]) SID Trp:Lys. In Exp. 2 (11 to 20 kg BW), increasing SID Trp:Lys ratio increased ( 0.05) ADG and G:F in a quadratic manner. For ADG, the best-fitting model was a QP in which the maximum ADG was estimated at 21.2% (95% CI: [20.5%, 21.9%]) SID Trp:Lys. For G:F, BLL and BLQ models had comparable fit and estimated SID Trp:Lys requirements at 16.6% (95% CI: [16.0%, 17.3%]) and 17.1% (95% CI: [16.6%, 17.7%]), respectively. In conclusion, the estimated SID Trp:Lys requirement in Exp. 1 ranged from 20.4% for maximum G:F to 23.9% for maximum ADG, whereas in Exp. 2 it ranged from 16.6% for maximum G:F to 21.2% for maximum ADG. These results suggest that standard recommendations may underestimate the SID Trp:Lys requirement for nursery pigs from 11 to 20 kg BW.

Estimation of lysine requirements of growing Japanese quail during the fourth and fifth weeks of age

A dose-response assay was conducted using broken-line regressions to estimate the lysine (Lys) requirements of quail chicks from 21 to 35 d of age. A basal diet was formulated to be adequate in all nutrients other than Lys. Incremental levels of L-Lys.HCl were added to the basal diet at the expense of a mix of cornstarch, NaHCO3, and NaCl to create 6 experimental diets containing 0.84 to 1.59% Lys. Feed intake (FI), weight gain (WG), and feed conversion ratio (FCR) responded quadratically to incremental levels of Lys (P < 0.0001). Using the linear broken-line (LBL) model, the estimated Lys requirements for WG during the fourth and fifth wk of age were 1.25 and 1.23% of diet, respectively. The corresponding values for FCR were estimated at 1.23 and 1.26% of diet, respectively. Fitting the quadratic broken-line (QBL) model, the estimated Lys requirements for WG during the fourth and fifth wk of age were 1.34 and 1.34% of diet, respectively. The corresponding values for FCR were estimated at 1.35 and 1.36% of diet, respectively. This study showed that using the QBL model as a promising way to estimate amino acids needed in the diet, the optimal Lys level to optimize performance of growing Japanese quail at the late stage of production might be 1.36% of diet, which is 105% of NRC recommendations.

Lysine requirement relative to total dietary protein for optimum performance and carcass protein deposition of Iberian piglets

This work aims at establishing dietary Lys requirements [g Lys/kg crude protein (CP, N×6.25)] of post-weaned Iberian piglets based on responses on growth performance, carcass nutrient deposition and plasma metabolites. Sixty piglets (10.7±0.1kg initial BW) were randomly assigned into six isoenergetic diets based on corn, barley and soybean meal. Diets contained increasing Lys concentrations at a constant dietary CP content (165±0.7g/kg DM). l-Lys HCl was added at the expense of corn starch providing Lys:CP ratios (g/kg) of 43, 47, 52, 57, 64 and 72g/kg. Other amino acids and nutrients remained constant. Six additional piglets were slaughtered at the start of the experiment to estimate initial carcass composition. Piglets were individually housed in 2m2 pens in an environmentally controlled room until slaughter (25.3±0.4kg BW) to analyze carcass composition. Average daily gain, G:F and Gain:ME intake (g/MJ) increased linearly (P<0.001) on increasing Lys concentration. Using average daily gain as a response, the linear broken-line regression and the first derivative of the quadratic function gave the same estimation for Lys requirement (71.0g Lys/kg dietary CP, respectively). Lysine content of dietary protein has no effect upon the apparent digestibility of DM, OM and nitrogen. Carcass protein deposition (PD) increased linearly (P<0.001) and quadratically (P<0.05) on increasing dietary Lys, reaching maximum values (39.3–40.2g protein/d) with diets providing 57, 64 and 72g Lys/kg CP. Carcass PD:CP intake, and carcass PD:digestible protein intake increased linearly (P<0.001) and quadratically (P<0.05) on increasing dietary Lys concentration. The linear broken-line regression using carcass PD (g/d) as response criterion estimated Lys requirement as 58.6g Lys/kg dietary CP with a plateau PD value of 39.9g/d. The first derivative of the quadratic function relating carcass PD and dietary Lys content gave a value of 63.7g Lys/kg CP. Plasma urea concentration tended to decrease on increasing Lys concentration (P=0.06 and P=0.10, for linear and quadratic effects). For plasmatic urea, both linear and quadratic approach gave a similar estimate for Lys requirements, 61.2g Lys/kg dietary CP. It is concluded that the preferred estimate based on carcass PD – the more reliable measure of metabolic Lys utilization – is 63.7g Lys/kg CP, somewhat below the established for conventional piglets.

Modeling the Effects of Standardized Ileal Digestible Tryptophan:Lysine Ratio on Growth Performance of 65- to 275-lb Pigs

The objective of this study was to model the effects of standardized ileal digestible (SID) Trp:Lys ratio on growth performance of 65to 275-lb pigs. The present experiment, along with three previous experiments from Goncalves et al. (2014), were used in the analysis. For all studies, dietary treatments consisted of SID Trp:Lys ratios of 14.5, 16.5, 18.0, 19.5, 21.0, 22.5, and 24.5%. The experiments were 21 d in duration and used corn and soybean meal-based diets with 30% dried distillers grains with solubles formulated to be deficient in Lys at the end of each of the experiments. In the current experiment, a total of 975 gilts (337 × 1050; PIC, Hendersonville, TN) were used with initial BW of 234.1 ± 6.8 lb and final BW of 274.9 ± 10.4 (mean ± SD). Pens of pigs were blocked by weight and assigned to one of the seven dietary treatments in a randomized complete block design. There were 6 pens/treatment with 20 to 24 pigs per pen. For 235 to 275 lb-pigs, increasing SID Trp:Lys improved ADG (quadratic, P < 0.022), ADFI (linear, P < 0.001), and F/G (linear, P < 0.001). Data from all experiments were then combined for analysis using linear and non-linear mixed models with random effects of experiment and weight block nested within experiment allowing for heterogeneous variances. Competing models included broken-line linear (BLL), broken-line quadratic (BLQ), and quadratic polynomial (QP). In the combined analysis for ADG, QP was the best fitting model and estimated SID Trp:Lys requirement at 23.5% (95% CI: [22.7, 24.3%]). In the combined analysis for F/G, BLL and BLQ had comparable fit and estimated SID Trp:Lys requirements at 16.9% (95% CI: [16.0, 17.8%]) and 17.0% (95% CI: [15.0, 18.9%]), respectively. Thus, the estimated mean requirements for SID Trp:Lys for 65to 275-lb pigs ranged from 16.9% for optimum mean F/G to 23.5% for maximum mean ADG. Furthermore, 95% of the maximum estimated mean ADG was obtained by feeding 17.6% SID Trp:Lys and 98% of the maximum estimated mean ADG was obtained by feeding 19.8% SID Trp:Lys.

Evaluation of a method estimating real-time individual lysine requirements in two lines of growing–finishing pigs

The implementation of precision feeding in growing–finishing facilities requires accurate estimates of the animals’ nutrient requirements. The objectives of the current study was to validate a method for estimating the real-time individual standardized ileal digestible (SID) lysine (Lys) requirements of growing–finishing pigs and the ability of this method to estimate the Lys requirements of pigs with different feed intake and growth patterns. Seventy-five pigs from a terminal cross and 72 pigs from a maternal cross were used in two 28-day experimental phases beginning at 25.8 (±2.5) and 73.3 (±5.2) kg BW, respectively. Treatments were randomly assigned to pigs within each experimental phase according to a 2×4 factorial design in which the two genetic lines and four dietary SID Lys levels (70%, 85%, 100% and 115% of the requirements estimated by the factorial method developed for precision feeding) were the main factors. Individual pigs’ Lys requirements were estimated daily using a factorial approach based on their feed intake, BW and weight gain patterns. From 25 to 50 kg BW, this method slightly underestimated the pigs’ SID Lys requirements, given that maximum protein deposition and weight gain were achieved at 115% of SID Lys requirements. However, the best gain-to-feed ratio (G : F) was obtained at a level of 85% or more of the estimated Lys requirement. From 70 to 100 kg, the method adequately estimated the pigs’ individual requirements, given that maximum performance was achieved at 100% of Lys requirements. Terminal line pigs ate more (P=0.04) during the first experimental phase and tended to eat more (P=0.10) during the second phase than the maternal line pigs but both genetic lines had similar ADG and protein deposition rates during the two phases. The factorial method used in this study to estimate individual daily SID Lys requirements was able to accommodate the small genetic differences in feed intake, and it was concluded that this method can be used in precision feeding systems without adjustments. However, the method’s ability to accommodate large genetic differences in feed intake and protein deposition patterns needs to be studied further.

Estimation of the standardized ileal digestible lysine requirement and the ideal ratio of threonine to lysine for late finishing gilts fed low crude protein diets supplemented with crystalline amino acids

Two experiments were conducted to investigate the effects of various standard ileal digestible (SID) lysine (Lys) levels and SID threonine (Thr) to Lys ratios on the performance and carcass characteristics of finishing gilts receiving low crude protein (CP) diets supplemented with crystalline amino acids (CAA). In Exp. 1, 108 gilts (87.8±5.9kg) were randomly allotted to one of six diets which consisted of a high CP (135g/kg) diet with 6.1g/kg SID Lys or five low CP (100g/kg) diets providing SID Lys levels of 4.9, 5.5, 6.1, 6.7 and 7.3g/kg, respectively. Gilts were housed in three pigs per pen with six pens per treatment. At the end of the 28 days experiment, 36 gilts (one pig per pen) with average body weight (BW) of 116kg were killed to evaluate carcass traits. The SID Lys levels required to maximize average daily gain (ADG) and optimize feed conversion ratio (FCR) as well as to minimize serum urea nitrogen (SUN) levels were 5.7, 5.8 and 6.1g/kg using a linear-break point model and 6.5, 6.5 and 6.6g/kg using a quadratic model. The fat-free lean gain tended to increase linearly with the increase in dietary SID Lys levels from 4.9 to 7.3g/kg when gilts receiving a low CP diet (linear effect, P=0.06). In Exp. 2, 90 gilts (90.6±5.7kg) were utilized in another dose–response study. Based on the Lys requirement estimated in Exp. 1, dietary treatments were formulated to contain 5.1g/kg SID Lys to ensure the dietary Lys level was marginally deficient for late finishing gilts. Graded levels of crystalline Thr (0, 0.3, 0.6, 0.9 or 1.2g/kg) were added to the basal diet providing SID Thr to Lys ratios of 0.54, 0.60, 0.66, 0.72 or 0.78, respectively. Each diet was fed to six pens with three gilts per pen. At the end of Exp. 2, 30 gilts (one pig per pen) were slaughtered to evaluate carcass traits (average BW=118kg). The optimum SID Thr to Lys ratios to maximize ADG and FCR as well as to minimize SUN levels were 0.61, 0.63 and 0.64 using a linear-break point model and 0.70, 0.75 and 0.74 using a quadratic model. With the exception of L* light (linear effect, P<0.05), no effect on carcass characteristics was observed with increasing dietary SID Thr to Lys ratio.