Total Dietary Lysine Research Articles

RESPONSE OF GROWING GUINEA FOWLS (NUMIDA MELEAGRIS) TO DIETARY L-LYSINE SUPPLEMENTATION

In two experiments, the performance of growing (day 1-6 weeks) guinea fowls, given 20 and 22.5% dietary protein supplemented with graded levels of lysine, was compared with control (25% protein birds). Weight gain, feed conversion and nitrogen retention were significantly (P.05) better in the control than other treatments at both 4 and 6 weeks of age. There was no growth response to 0.05% lysine supplementation in any of the diets. Supplementation of the 20% protein diets with 0.5% lysine produced significant (P.05) weight gains at both 4 and 6 weeks of age. However, supplementation of 22.5% protein diet with 0.5% lysine produced significant (P.05) weight gains, only, at 6 weeks. Best performances were obtained when total dietary lysine level was between 1.6% and 1.8% of the diet.

Effect of total lysine:crude protein ratio on growth performance of nursery pigs from 15 to 25 lb (2011)

A total of 282 nursery pigs (PIC TR4 × 1050, initially 15.9 ± 0.15 lb BW and 3 d postweaning) were used in a 28-d growth trial to evaluate the effects of total lysine:CP ratio, using fish meal as a source of non-essential N, on growth performance. Pigs were allotted to 1 of 6 dietary treatments. Each treatment had 5 replications with 7 pigs per pen and 2 replications with 6 pigs per pen. Pigs and feeders were weighed on d 0, 7, 14, 21, and 28 to calculate ADG, ADFI, and F/G. A 2-phase diet series was used with treatment diets fed from d 0 to 14 and a common diet fed from d 14 to 28. All diets were in meal form. The 6 total lysine:CP ratios were 6.79, 6.92, 7.06, 7.20, 7.35, and 7.51%. From d 0 to 14, there was a trend for increased (quadratic; P < 0.09) ADG with an increasing dietary total lysine:CP ratio up to 7.35%, with poorer performance in pigs fed the greatest lysine:CP diet. Increasing the total lysine:CP ratio tended to improve (quadratic; P < 0.09) F/G for pigs fed 7.35%, with poorer F/G as total lysine:CP ratio increased to 7.51%. When a common diet was fed (d 14 to 28), there was no difference in ADG or F/G. A response (quadratic; P < 0.04) was detected for ADFI due to an increase in ADFI from the pigs fed the intermediate diets (7.06 and 7.20% total lysine:CP) during the previous period. Overall (d 0 to 28), there was a trend (quadratic; P < 0.07) for increased ADG and ADFI caused by the numerically highest values from pigs fed a total lysine:CP ratio of 7.35% and the numerically lowest values from pigs fed a total lysine:CP ratio of 7.51%. Dietary treatment did not influence F/G for the overall trial. These results indicated that feeding total lysine:CP ratio greater than 7.35% may decrease growth performance of nursery pigs.

Effect of Dietary Lysine Supplement on the Performance of Mong Cai Sows and Their Piglets

The objective of this study was to determine optimal lysine requirement of lactating Mong Cai sows and their piglets. An experiment was conducted using 30 Mong Cai sows in a factorial randomized design with 5 dietary total lysine levels (0.60, 0.70, 0.85, 1.0 and 1.15%) for one-week pre-partum and 5 dietary total lysine levels (0.60, 0.75, 0.90, 1.05 and 1.2%) for lactation diets. Mong Cai sows were about 1 to 2 years old and had an initial body weight of 120 kg (sd = 2.5) after farrowing. Sows were restrictively fed 1.7 kg feed during gestation and were fed ad libitum during lactation. Diets of sows contained about 12% CP during pregnancy and about 14% CP for the lactation period. DE concentration of the diets ranged between 12.5-13.0 MJ of DE. Water was supplied at up to 8 liters per sow per day in a basin. Studied traits were related to both sows and their progeny. Sows were weighed at 107 days of gestation, after farrowing and at weaning. Sow back-fat depth was measured at 110 days of gestation, after farrowing, at 21 days of lactation and at weaning. Number of piglets born, at 24 h after birth, at 21 days of age and at weaning were recorded. Piglets were weighte at birth, at 21 days and at weaning. Supplying lysine one week pre-partum had no effect on the number of piglets born nor litter weight at birth (p = 0.776 and p = 0.224). A positive effect of increasing dietary lysine level during lactation from 0.60 to 1.20% was observed with regard to less sow weight loss, and increased piglet weight at 21 days and at weaning. The level of lysine that resulted in the lowest sow backfat loss and the highest weaned piglet weight was 1.05%; this may be the optimum level of lysine for the diet of lactating Mong Cai sows. At this lysine level, the number of weaned piglets was also highest.

Effect of dietary leucine and lysine levels on intramuscular fat content in finishing pigs

Feeding high leucine levels (2.0 and 3.0% total dietary leucine) to finishing pigs (73 to 127 kg liveweight) increased the intra muscular fat content of the longissimus muscle in pigs fed diets with low lysine levels (0.5% total dietary lysine) but not in animals fed high lysine levels (0.7 %). Key words: Lysine, leucine, growth performance, carcass and meat quality

Comparison of modified Concept PR 100 and spray-dried animal plasma on nursery pig performance (2007)

One hundred eighty weanling pigs (initially 11.3 lb and 18 ± 2 d of age) were used in a 28-d growth assay to determine if Modified Concept PR 100 (MCNPR), a plant-based protein ingredient containing added synthetic amino acids and nucleic acids, can replace spray-dried animal plasma (SDAP) in nursery pig diets. The five experimental treatments were: 1) control (no specialty protein source); 2) 2.5% SDAP; 3) 5.0% SDAP; 4) 2.5% MCNPR; and 5) 5.0% MCNPR. Treatment diets were fed from d 0 to 14 post-weaning, with a common diet fed to all pigs from d 14 to 28 post-weaning. Analyzed values of MCNPR were noticeably lower than the manufacturer provided values used in diet formulation. The difference in calculated and analyzed lysine values would decrease the total dietary lysine content by 0.027 and 0.056% for the 2.5 and 5.0% MCNPR, respectively. From d 0 to 14, pigs fed increasing SDAP had improved (linear, P<0.01) ADG, ADFI, and F/G, which was primarily due to a large improvement from the 0 to 2.5% SDAP inclusion, with further increases when 5.0% was fed. In addition pigs fed increasing levels of MCNPR had improved (quadratic, P<0.002) feed efficiency, with pigs fed 2.5% MCNPR having the maximum response. While no statistical differences (P>0.21) were detected in ADG and ADFI for pigs fed increasing levels of MCNPR, there were improvements by approximately 21 and 11%, respectively, over the control diet. However, pigs fed SDAP had greater (P<0.05) ADG, ADFI, and BW at d 14 compared to pigs fed MCNPR. Overall (d 0 to 28), pigs fed increasing SDAP from d 0 to 14 had greater (P<0.03) ADG and tended to have improved (P<0.08) ADFI and F/G. Also, pigs fed increasing MCNPR had improved (quadratic, P<0.01) feed efficiency, with pigs fed 2.5% MCNPR having the maximum response. While no statistical differences (P>0.18) were detected in ADG and ADFI for pigs previously fed increasing MCNPR, there were improvements by approximately 10 and 7%, respectively, over the control diet. Although the magnitude of difference between pigs fed SDAP and MCNPR was maintained to the end of the trial, there were no overall significant differences in growth between pigs fed SDAP and MCNPR (P>0.21). These results indicated that SDAP and MCNPR can effectively be used in nursery pig diets to improve growth performance when used as a partial replacement for soybean meal. However, pigs fed SDAP had greater performance than pigs fed MCNPR during the test period, but these differences were not found at the conclusion of the studies.; Swine Day, 2007, Kansas State University, Manhattan, KS, 2007

Exigência nutricional de lisina para codornas européias machos de 21 a 49 dias de idade

O experimento foi conduzido como objetivo de estimar a exigência de lisina total para codornas européias (Coturnix coturnix coturnix) machos de 21 a 49 dias de idade. Foram utilizadas 315 codornas (peso vivo médio de 80 g) alimentadas com rações à base de milho, farelo de soja e farelo de glúten de milho. A ração basal, formulada sem suplementação de lisina sintética, continha 20% de PB, 2.900 kcal de energia metabolizável (EM)/kg e 0,9% de lisina total e foi suplementada com 0,125; 0,231; 0,357 e 0,483 de L-lisina-HCl (79%), resultando em rações com 1,0; 1,1; 1,2 e 1,3% de lisina total, respectivamente. Utilizou-se delineamento inteiramente casualizado, com cinco tratamentos, sete repetições e nove aves por unidade experimental. Foram avaliados o consumo de ração, o peso final, o ganho de peso, a conversão alimentar, o índice de eficiência produtiva e os rendimentos de peito e de carcaça. Observou-se efeito não-significativo para todas as variáveis avaliadas. A exigência dietética de lisina total para codornas européias machos de 21 a 49 dias de idade é de 0,9%, que corresponde a um consumo diário de 207 mg de lisina por ave.

Exigências de lisina, com base no conceito de proteína ideal, para suínos machos castrados, de 95 a 122kg, selecionados para deposição de carne magra

Determinaram-se as exigências de lisina para suínos machos castrados utilizando-se 40 animais distribuídos em delineamento experimental de blocos ao acaso, com cinco tratamentos (0,5; 0,6; 0,7; 0,8 e 0,9% de lisina total), quatro repetições e dois animais por baia. Adicionaram-se aminoácidos sintéticos para se manter o nível de acordo com o perfil da proteína ideal. Observou-se efeito quadrático dos tratamentos sobre o ganho de peso diário, espessura do toucinho na 10ª costela, espessura do toucinho na última costela e conversão alimentar. Houve efeito linear sobre o consumo de lisina diário e taxa de deposição de carne magra diária. O modelo linear response plateau ajustou-se melhor aos resultados da taxa de deposição de carne magra diária. Não houve efeito sobre o consumo de ração diário, espessura de toucinho no P1, espessura de toucinho no P2, profundidade de lombo, porcentagem de carne magra, rendimento de carcaça, comprimento de carcaça pelo método brasileiro, comprimento de carcaça pelo método americano e rendimento de pernil. A exigência de lisina total para suínos machos castrados de 95 a 122kg, selecionados para deposição de carne magra na carcaça, é de 0,76%, correspondendo ao consumo de 25,99g/dia.

Sensitivity to dietary lysine: energy content in pigs divergently selected for components of efficient lean growth rate

AbstractThe sensitivity to dietary lysine: energy content of pigs from lines divergently selected over seven generations for components of efficient lean growth rate was quantified by the within-selection line regression of performance test traits on diet class. Large White pigs were performance tested over three 14-day test-periods starting at 30, 50 and 75 kg and offered, to appetite, isoenergetic diets differing in dietary total lysine: energy (0•59, 0•69, 0•81, 0•91, 1•01, 1•12 and 1•23 g/MJ digestible energy (DE)). Within each litter, full-sibs were performance tested on different diets. Pigs were also performance tested on a diet-choice procedure using diets with total lysine: energy of 0•69 and 1•12 g/MJ DE to determine the correlation between performance on phase-feeding and diet-choice.The study consisted of 578 animals with 459 pigs tested with phase-feeding and 119 tested on diet-choice procedures. The study detected significant selection line and dietary effects on performance test traits, but no significant between-selection line differences in sensitivity to dietary total lysine: energy. When combinations of performance test traits were transformed into predicted lysine and energy utilization traits there were significant selection line effects on predicted nutrient allocation, but not in responses to increasing dietary total lysine: energy. The lack of between-selection line differences in sensitivity to dietary total lysine: energy indicated that the consequences of changing dietary total lysine: energy will be broadly similar across a range of genotypes, as spanned by the selection lines of the study.Genetic correlations between performance traits of phase-fed and diet-choice pigs suggested that predictions of genetic merit will be similar with animals tested on either procedure between 30 and 75 kg but post 75 kg predicted genetic merit for growth rate and lysine intake should be estimated separately for performance on diet-choice or for performance on a given diet. In contrast, predicted genetic merit for fat deposition with performance testing on diet-choice will be highly correlated with predicted genetic merit with testing on a single diet.

Serum urea concentration as a predictor of dietary lysine requirement in selected lines of pigs.

Serum urea concentrations were measured in Large White pigs from lines divergently selected for components of efficient lean growth rate and performance tested over three 14-d test periods starting at 30, 50, and 75 kg. Two methods of performance testing were used. Phase-fed pigs were fed to appetite isoenergetic diets differing in total lysine:energy ratio (0.58, 0.69, 0.81, 0.91, 1.01, 1.12, and 1.23 g/MJ of digestible energy), whereas diet-choice pigs were offered a choice of the 0.69 and 1.12 lysine:energy diets. Between test periods, all animals were fed one diet: 0.91 g of lysine/MJ of digestible energy. The study consisted of 230 boars and gilts with 150 pigs performance tested on phase-feeding and 80 pigs on diet-choice. The line selected for high lean food conversion had lower urea concentrations on each diet than the line selected for high lean growth rate, despite similar predicted lysine balances. Efficiency of lean growth rather than the rate of lean growth may be a better selection strategy in the context of nitrogen excretion. Urea concentrations at the end of each test period were correlated with lysine intake (0.33, 0.48 and 0.65; standard error, 0.08) and predicted lysine balance (0.39,0.44, and 0.64), but were uncorrelated with predicted lysine for protein deposition (0.01, 0.08, and 0.08) and maintenance. Urea concentration at the end of a test period was not a useful predictor of protein deposition, even after accounting for pretest variation in urea concentration and food intake during test. The expected response pattern of serum urea concentration to diets differing in total lysine:energy would be nonlinear, with the point of inflection occurring at the required dietary total lysine:energy for each genotype. However, there was no evidence of such an inflection point such that the prediction of lysine requirement from urea concentration was not possible for the selection lines in the study.

Effects of increasing dietary lysine in transition diets on nursery pig growth performance (2003)

A total of 1,400 weanling pigs (initially 13.6 lb) was used in a 9 d growth assay (d 4 to 13 postweaning) to determine the effects of increasing lysine in the transition diet on nursery pig growth performance. All pigs were fed a common SEW diet until d 4 after weaning. Pigs were then switched to experimental diets with total dietary lysine levels of 1.40, 1.50, 1.60, 1.70 or 1.80%. All diets were formulated to contain 20% soybean meal, with increasing amounts of synthetic amino acids to achieve desired amino acid concentrations in the diets. From d 4 to 9 postweaning, increasing lysine increased ADG (linear, P<0.03) and improved feed efficiency (linear, P<0.001), but ADFI was not affected. Overall (d 4 to 13 postweaning), pigs fed diets containing increasing dietary lysine had improved ADG (linear, P<0.03) and feed efficiency (linear, P<0.001), with no differences in ADFI. Although responses to increasing dietary lysine were linear, there was little improvement either ADG or F/G above 1.7% lysine. There was no difference in average pig weight at the end of the trial, probably because of the short duration of the study. In conclusion, increasing dietary lysine up to 1.7% in transition diets (13 to 19 lb) for nursery pigs maximized growth performance.; Swine Day, 2003, Kansas State University, Manhattan, KS, 2003

Níveis de lisina para frangos de corte de 1 a 21 e 15 a 40 dias de idade

Foram realizados dois experimentos para determinar a exigência nutricional de lisina total para frangos de corte Hubbard e Ross de ambos os sexos, nos períodos de 1 a 21 e 15 a 40 dias de idade. Foram avaliados ganho de peso, consumo de ração, conversão alimentar e rendimentos de carcaça, peito com osso, carne de peito e gordura abdominal. Para cada fase, o delineamento experimental utilizado foi em blocos casualizados, em esquema fatorial 2 x 2 x 6, constituído de dois sexos, duas marcas e seis níveis dietéticos de lisina, com quatro repetições e um total de 1920 aves. Dietas basais com 1,0% de lisina, 22,61% PB, 3050 kcal EM/kg, no primeiro experimento, e 0,825% de lisina, 19,6% PB e 3200 kcal EM/kg, no segundo experimento, foram suplementadas com seis níveis de lisina (0; 0,06; 0,12; 0,18; 0,24; e 0,30%). Considerando-se características como ganho de peso e conversão alimentar, as estimativas das exigências dietéticas para a fase de 1 a 21 dias foram 1,191 e 1,198% de lisina total para machos e fêmeas Ross e de 1,174 e 1,188% de lisina total para machos e fêmeas Hubbard, respectivamente. Para a fase de 15 a 40 dias, considerando-se ganho de peso, consumo de ração, conversão alimentar e rendimentos de carcaça, peito com osso, carne de peito e gordura abdominal, o nível de 1,125% de lisina total na ração foi considerado adequado para ambos os sexos das duas marcas comerciais.

Influence of soybean meal variety and processing temperature on the growth performance of pigs from 25 to 45 lb (1998)

Three hundred ninety high-lean growth pigs were used in a 17 d growth assay from 25 to 45 lb. Treatments consisted of soybean meal (SBM) from either high-oleic or check-line soybean varieties processed under pilot-plant processing conditions at four temperature ranges (80-85, 85-90, 90-95, 100-105 °C). Positive and negative controls were made using commercially obtained SBM (46.50%CP). Total dietary lysine was maintained at .95% except for the positive control (1.30%). Pigs fed commercial SBM with 1.30% dietary lysine had increased ADG and better F/G than pigs fed any other treatment. A SBM variety x processing temperature interaction was observed for ADG and F/G for each growth period. The interaction likely resulted from improvement in ADG and F/G with high-oleic SBM, but not the check-line SBM, as processing temperature increased. Pigs fed high-oleic SBM had improved ADG and F/G throughout all growth periods as processing temperature increased, so pigs fed high-oleic SBM processed at 80-85 °C had poorer growth performance than pigs fed any other treatment. These results indicate that pigs fed high-oleic SBM processed above 80-85 °C have similar performance to pigs fed SBM from other varieties.; Swine Day, Manhattan, KS, November 19, 1998

Effects of increasing total sulfur amino acid:lysine ratio on growth performance of 25 to 50 lb pigs (1998)

Three hundred and fifty pigs were used in a 27-d growth study to determine the appropriate total sulfur amino acid:lysine ratio for 25 to 50 lb pigs. Pigs were blocked by weight (initially 22.5 lb) and allotted to one of 10 treatments arranged in a 2 x 5 factorial with two levels of total dietary lysine (.95 and 1.250/0) and five total sulfur amino acid ratios (.45, .50, .55, .60, and .65% of total lysine). Increasing total lysine from .95 to 1.25% increased ADG and improved FIG. Increasing the total sulfur amino acid:lysine ratio did not affect ADG but improved F/G. These results indicate that the optimal total sulfur amino acid:lysine ratio for the 25 to 50 lb pig is not greater than 55%.; Swine Day, Manhattan, KS, November 19, 1998

Lysine requirement of the lactating sow determined by using plasma urea nitrogen as a rapid response criterion.

The dietary lysine requirement of adult sows nursing 10 pigs was estimated by using plasma urea nitrogen (PUN) concentration as a rapid response criterion. A preliminary experiment indicated that a 3-d feeding time is required to re-equilibrate PUN concentrations after a change in the dietary concentration of lysine. In the main experiment, 12 sows (BW = 219 +/- 5 kg; parity = 4.5 +/- .3; ultrasound backfat = 21.3 +/- .9 mm) were used in two 6 x 6 Latin squares. Treatments consisted of dietary lysine intakes (30.2, 36.9, 43.6, 50.3, 57.0, and 63.7 g/d) that were assigned to six 4-d periods and to six sows in each square. Diets provided adequate levels of all nutrients other than lysine. The treatment periods started on d 5 of lactation and ended on d 29. Plasma urea N concentrations were determined on the 3rd and 4th d of each of the six 4-d treatment periods. Plasma urea N concentrations decreased quadratically (P < .02) with, increasing dietary lysine intakes. A two-slope, broken-line regression model was used to estimate the dietary lysine intake that minimizes PUN concentrations. The results indicated that adult sows nursing 10-pig litters with an average growth of 2.22 kg/d required 55.3 g/d of dietary total lysine to minimize PUN concentrations and, therefore, presumably to minimize body protein mobilization.

Protein utilization responses of growing pigs to supplemental lysine as liquid versus crystalline form in barley-barley protein diet

The study examined the influence of increasing dietary supplements of liquid compared to crystalline lysine on nitrogen (N) balance and protein utilization in growing pigs (30-100 kg LW) in a 8*8 Latin square. Eight isonitrogenous diets with 160 g CP/kg were formulated from barley and barley protein supplemented with the two lysine sources at levels of none, 1, 2 and 3 g/kg to provide 5.5, 6.5, 7.5 and 8.5 g/kg total dietary lysine. Barley-SBM served as a contol diet. The dietary lysine concentration had substantial effect on N retention and metabolism. The lysine supplements to the cereal-based diet with a low lysine content, 5.5 g/kg, significantly improved N-retention, decreased urinary-N excretion and enhanced protein utilization and daily gain. There was a linear response of N-retention, urinary-N and urea-N excretion and apparent biological value (P

Effect of extrusion on the ileal and fecal digestibilities of lysine, nitrogen, and energy in diets for young pigs.

Forty crossbred barrows (initial average BW of 20 kg) were fitted with T-cannulas in the distal ileum to determine the effects of extrusion of soybean meal on the apparent ileal and fecal digestibilities of lysine, N, and GE. A basal corn-soybean meal diet was formulated to contain .525% lysine. Nonextruded soybean meal (SM), extruded soybean meal (ESM), and L-lysine.HCl (LLH) replaced cornstarch in the basal diet to make diets containing .60, .675, and .75% total dietary lysine for each lysine source. Treatments were arranged as a 3 x 3 factorial with the basal diet as an additional treatment. Ileal and fecal digestibilities of lysine were not affected (P greater than .05) by source of lysine. However, linear increases (P less than .05) occurred in ileal lysine digestibilities with increasing concentrations of dietary lysine provided as LLH, but not when lysine was provided as SM or ESM. Apparent ileal and fecal retention of N as percentages of N absorbed or consumed were greater (P less than .05) for diets containing LLH than for diets containing SM, and diets containing ESM were intermediate. Linear increases (P less than .05) occurred in ileal and fecal N retained as percentages of N absorbed or consumed with increasing concentration of dietary lysine provided as LLH or ESM, but not when provided as SM. Fecal DE and ME (kilocalories per gram of diet) for diets containing LLH and ESM were similar and greater (P less than .05) than the values obtained for diets containing SM.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of extrusion on the ileal and fecal digestibilities of lysine in yellow corn in diets for young pigs.

Forty crossbred barrows (initial avg BW of 20 kg) were fitted with T-cannulas to determine the effects of extrusion of yellow corn on lysine digestibility. A basal corn-cornstarch-soybean meal diet was formulated to contain .55% lysine. Extruded corn (EC), non-extruded corn (C) and L-Lysine-HCl (LLH) replaced cornstarch in the basal diet to provide total dietary lysine levels of .60, .65 and .70% lysine for each lysine source. Diet intake was 5.5% of BW. Treatments were arranged as a 3 x 3 factorial with the basal diet as an extra dietary treatment. Apparent ileal digestibilities of lysine, threonine, methionine and isoleucine were greater (P less than .05) for diets with added LLH than for diets containing EC or C, which were similar (P greater than .05). Apparent ileal and fecal digestibilities and retention of nitrogen (N) as a percentage of N absorbed or consumed were greater (P less than .05) for diets containing LLH than for those containing EC or C, which were not different (P greater than .05). Plasma urea N levels were also lower (P less than .05) for pigs fed diets containing LLH than for pigs fed EC or C. Fecal DE and ME as a percentage of GE were greater (P less than .05) in diets containing EC than in those containing C. In summary, extrusion improved (P less than .05) energy utilization but did not affect the utilization of lysine or N in corn by pigs. However, lysine and N utilization were greater (P less than .05) in diets supplemented with LLH compared with EC or C.

Lysine requirement of growing puppies fed practical and purified diets

Growing Pointer puppies were used in four experiments to establish a quantitative requirement for lysine in an intact-protein (22.25% crude protein, 3863 kcal ME/kg) and purified crystalline L-amino acid diet (13.69% crude protein, 4099 kcal ME/kg). In experiments 1 and 2, a corn gluten meal, sesame meal and meat and bone meal (CGM-SM-MBM) diet was supplemented with L-lysine•HC1 to contain lysine levels varying from 0.5 to 1.0% of the diet. Weight gain and feed efficiency were maximized when total dietary lysine was present at 0.8% of the diet (207 mg/100 kcal ME). In experiments 3 and 4, crystalline amino acids were fed as the sole source of nitrogen. Rate of gain and feed efficiency of puppies fed dietary lysine levels ranging from 0.4 to 0.9% suggested a requirement not exceeding 0.7% of the diet (171 mg/100 kcal ME). Plasma and urinary urea decreased linearly when puppies were fed the crystalline amino acid diet supplemented with increasing levels of lysine. Plasma free lysine concentration in puppies fed either the intact protein or free amino acid diet remained relatively low until dietary lysine reached the level required for maximal growth and efficiency of feed conversion. At dietary lysine levels above this point, plasma free lysine increased markedly.

Evaluation of optimum lysine and threonine supplements to a wheat and barley-based diet in rats

Experiments were conducted on growing male SPF-rats to study the optimum supplementation with essential amino acids of diets containing wheat and barley (1.4:1) as the only source of nitrogen. In growth and balance experiments comprising 30 and 17 combinations of L-lysine and L-threonine, respectively, the concentrations of the two amino acids corresponding to maximum body weight gain, feed conversion efficiency, biological value of protein and net protein utilization were calculated using multiple regression analysis. Addition of lysine and threonine to the basal diet markedly improved the nutritional value of cereal proteins. The optimum concentrations found were 0.69–0.70% total dietary lysine and 0.52–0.55% total dietary threonine. Statistical analysis showed that the number of observations used for the estimation of regression functions in the growth experiment could be reduced to ca. 100 without substantially affecting precision.

Lysine requirement of weanling European pigs fed on yellow maize and groundnut cake diets in the humid lowland tropics

Two groups of Large White × Landrace pigs (each with 30 castrates and 30 gilts) were grown from approximately 10 kg to 16 or 23 kg liveweight. The 60 pigs per group were allocated on the basis of sex, initial liveweight and litter origin to ten treatments involving individual feeding with a basal diet supplemented with graded levels of L-lysine at a common digestible energy level of 15.2 MJ/kg dry matter. Total dietary lysine ranged from 0.52 to 1.42%. The pigs reared to 23 kg liveweight were slaughtered at the end of the experiment. Growth rate, N retention and efficiency of N retained of the pigs reared to 16 or 23 kg were significantly ( P < 0.01) influenced by dietary lysine levels. Optimum performance, N retention and carcass leanness was observed with a diet containing 1.02% total lysine. Estimated lysine requirements for optimum growth of 10–16 and 10–23-kg pigs were 1.03 and 0.98%, respectively. No sex difference in lysine requirement was observed, although regression analysis suggested non-significantly higher lysine requirements for gilts. With the exception of the liver, relative weights of other organs were not significantly influenced by dietary lysine levels. Plasma urea concentration was minimal when the basal diet was supplemented to contain about 0.92% lysine in 16 or 23-kg pigs, suggesting this to be the minimum lysine requirement of these classes of pigs.