Determination of lysine requirement in growing rats as based on the catabolism rate of 14-C- and 15-N-labeled lysine

Male Wistar rats (weighing some 80 g at the start of the experiment) were fed diets containing maize gluten as protein carrier and which was supplemented with amino acids (except lysine) in such way that their concentrations came up to the requirement norms. Lysine was gradually supplemented this resulting in 10 diets of different lysine content (1.6-10.6 g lysine/16 g N). On the 7th experimental day, 4 animals of each group were labelled with 14C-lysine and subjected to 2-hour measuring of 14CO2-excretion. On the following day, the animals were injected i.p. 15N-lysine, the urine being collected over 24 hours to determine 15N-frequency in urine. Both 14CO2-excretion and 15N-frequency in urine were found to remain constant at a lysine content of the diet up to 4.5 g/16 g N and rose steeply from 5.8 g lysine/16 N on. Under the experimental conditions chosen the lysine requirement is deduced to be 5 g/16 g N. This method of lysine requirement determination is highly sensitive and exact because it covers the catabolization of the amino acids under study and not so parameters that are known to be influenced by other factors such as growth, N-balance, total N-conversion or CO2-formation. The method can also be applied to metabolic situations not connected with productive performances.     

Activity and requirement of selected amino acids in growing female pigs. 4. Combination of protein sources with lysine, methionine/cystine and threonine limitation

On the basis of the results of 3 previous articles on the efficiency of amino acids in single protein sources a total of 16 protein sources was tested maintaining the limitation relations of the combination partners with regard to the additivity of the efficiencies of lysine, methionine/cystine and threonine. The results of the N metabolism measurements with a total of 60 female pigs of the country breed type (30...55 kg live weight) allow the conclusion that additive relations and thus suitable correction possibilities exist for the gross amino acid content through the amino acid efficiency for the calculation of requirement and requirement meeting. The N utilization model used (GEBHARDT 1963) is in its further development confirmed as the basis of amino acid efficiency.     

Studies on methods for the determination of amino acid requirements for metabolic balance based on the oxidation rate of 14C labeled lysine to 14CO2]

Male experimental rats (100 gm liveweight) were distributed into 10 groups of 8 animals each and received balanced diets, with the exception of lysine which was added to the diets in graded amounts in such a way that the lysine content of the diets ranged from 2.44 to 5.92 gm/16 gm N. After a feeding period of 7 days the animals received 3H- and 14C lysine injected intraperitoneally, 4 animals of each group were investigated for the total CO2 excretion and 14CO2 excretion during the first 2 hrs after the injection and for the urinary excretion of radioactivity (48 hours). The remaining animals in each group were used for determining the plasma amino acids and for establishing the specific radioactivity of free lysine in the liver and muscles after an 1-hour incorporation period. Total CO2 excretion was not found to be influenced by the lysine contents while the level of excretion of 14C activity through CO2 and that of specific 14C activity of CO2 increased with increasing lysine concentrations. This produced a broken curve pattern, showing an increased release of 14CO2 (under maintenance conditions) if the diet contained 4 gm lysine/16 gm N and more. Investigations for the specific 14C activity of free lysine in the liver, the main site of lysine oxidation, showed that the increase in 14CO2 release was due to an enhanced rate of lysine catabolism and was not brought about by changes in the pool volume or in specific radioactivity. The levels of urinary 14C excretion were not found to be related to the lysine content of the diets, whereas the curve pattern of 3H excretion observed 5 to 8 hrs after injection was similar to that of 14CO2 excretion. The lysine content of blood plasma and the content of free lysine in the liver increased continuously with increasing levels of dietary lysine. The methodological studies made in the present paper showed that in scientific research a determination of amino acid requirements on the basis of CO2 oxidation data may be a very exact and sensitive method. It will also yield values for maintenance requirements.     

Absorption and utilization of amino acids infused into the cecum of growing pigs. 2. 15N-labeled lysine

Over a period of 4 days 15N-labelled lysine was infused into two growing female pigs (live weight approximately 50 kg) through a caecal cannula. The feeding was restrictive (1,400 g dry matter/day) and, with regard to lysine, it didn't meet the requirement. In a 7-day experiment the N- and 15N-content was measured periodically in the excretions (feces and urine), in various fractions of the blood and in selected slaughtering samples. From the infused 15N 3-5% are excreted as lysine in feces, another 5% are in other amino acids of the bacteria protein. The disappearance rate of 15N' from the large intestine makes greater than or equal to 90%. The biggest part of this 15N (78-88%) is excreted with the urine in form of 15N-urea. Obviously the infused amino acid is decomposed to NH3 in the large intestine and then absorbed. The absorbed ammonia is changed into urea in the ornithine cycle and excreted in urine. The recovery rate of the 15N infused as 15N-lysine is 93 and 84% resp. Incorporation of 15N in to serum protein or other body protein could not be detected so that the remaining difference of 7-16% cannot necessarily be interpreted as incorporation rate of 15N into the body protein. Under practical conditions the maximal utilisation of lysine from the feed in the large intestine is 1.6% and should thus be without importance.     

The determination of a gross utilization of 15N-lysine in laboratory rats. 1. Experiment with normal intestinal flora (without antibiotic supplement)]

Wistar rats of a live weight of about 100 g were divided into 14 groups (5 animals/group). The rations given supplied the animals with 75%, 100% and 125% lysine, which brought about a moderate growth of the animals of approximately 2 g/animal and day achieved by limited feeding. The 3 lysine levels mentioned could be achieved by lysine supplements (L-lysine-HCl) for the following rations: barley (B), wheat (W), and wheat gluten (WG). For isolated soybean protein (assay protein) (S) the lysine levels 100% and 125% and for soybean meal (SM) the levels 116% and 125% could only be achieved. A control group with whole egg ration (W) (with its natural lysine content of 125% of the requirement) were also tested as comparison. During the 10-day period of the main experiment all 14 rations were supplemented with 0.5 g 15N-lysine (alpha amino group, 95% labelled with 15N). The N balance could only be significantly improved by lysine supplements in the rations B, W and SM with the lysine level of 125%. The biologic value of the protein sources was in rations B and WG also significantly improved by the highest lysine supplement. 15N excess (15N') from the deaminated 15N lysine was excreted with diet B rich in crude fibre mainly in faeces (more than 15% of the intake) and only about 10% in urine. With the diets without native crude fibre the excretion quota changed in favour of urine. The following 15N' amounts in per cent of 15N' intake from lysine were excreted in urine and faeces: B 75 = 31.3, B 100 = 30.9, B 125 = 28.0, W 75 = 24.3, W 100 = 32.2, W 125 = 32.6, GW 75 = 18.3, WG 100 = 24.2, WG 125 = 28.1, S 100 = 39.4, S 125 = 50.4, SM 116 = 34.9, SM 125 = 32.9, W 125 = 19.1. 15N excretion in urine and faeces increased in comparable relations in 6 cases of lysine increase levels only. Gross utilization of lysine can only conditionally be quantified by 15N labelled lysine supplement.     

Effect of graded high-energy-level protein supply on fattening performance and retention and utilization of feed energy, protein and amino acids in female fattening swine. 4. Nitrogen and amino acid content in carcasses and parts

The slaughtering and cutting up of 7 (6) female pigs in each of 3 groups (live weight approximately 113 kg) fed on approximately 80, 100 and 120% protein (lysine) of the norm as well as the determination of nitrogen and amino acids in the individual parts of the body had--in comparison to 6 reference animals (live weight approximately 36 kg) treated in the same way at the beginning of the experiment--the following results: In the course of growth the quota (in % of the slaughter weight) of bacon, belly fat + intestinal fat tissue is more than doubled; the relative quotas of bones, skin + ears, bristles + claws, blood and entrails, however, decrease. The total meat quota is 54% and remains relatively equal independent of the live weight. The N-quotas (in % of the empty body-N) of muscle and fat tissue and of the skin increase in the course of fattening, those of bones, useable organs and offal decrease distinctly. At the end of fattening the muscle protein of the animals amounted to 59% of the empty body protein and to 87% of the carcass protein. The amino acid content (g/16 g N) hardly changes in the individual parts during growth; the percentage amino acid distribution follows the weight-and N-distribution. The lysine content of the edible parts of the carcass is 8.4 g/16 g N. The chosen grades in the protein (lysine) supply of the test animals did not result in any significant changes with regard to the qualitative parameters (protein and amino acid content of the valuable and less valuable parts of the body as well as their percentage distribution in the empty body). The quantitative parameters (live weight gain, protein (amino acid) retention per day) are diminished in approximately the same relation as the insufficiency of the alimentary supply; by excessive supply, however, they do not significantly increase. The results are compared with corresponding data from literature and discussed.     

Methodologic studies on the metabolically-oriented determination of lysine requirements in broiler chickens. 2. Effect of the lysine content of the diet on the lysine oxidation rate in a 15-hour feed withdrawal before 14C-lysine injection

This experiment was designed to narrow the estimated range for lysine requirement of broiler chickens determined by isotopic techniques. In addition the influence of a long-term feed withdrawal previous 14C-lysine-injection on the lysine catabolism was investigated. 120 male broiler chickens 7 to 21 days posthatching received a diet based on wheat and wheat gluten. Lysine content was varied from 8.3 to 16.0 g/kg DM (3.2 to 6.3 g/16 g N) at 8 levels by supplementing the basal diet with L-lysine-HCl. After the feeding period animals of each group were labelled with 14C-L-lysine by intravenous injection 5.5 and 15.5 hours after feed withdrawal, respectively. During the following 4 hours the excretion of 14CO2 and CO2 was measured. Highest body weight gain was observed in the group with 13.8 g lysine/kg DM. In case of 14CO2 excretion measurements starting 5.5 hours after feed withdrawal an increase of 14CO2 excretion was observed if the lysine content of the diet exceeded 11.6 g/kg DM. This estimated range for lysine requirement (11.6 to 12.7 g/kg DM with 26% CP in the DM) was lower compared with the lysine requirement estimated by the growth curve (12.7 to 13.8 g/kg DM). This discrepancy could be explained by the fact that the results of the metabolism oriented determination of lysine requirement represent the requirement at the actual age, while the feeding experiment reflects a mean lysine requirement of the previous period of 14 days. If the animals were labelled with 14C-lysine 15.5 hours after feed withdrawal no clear response in 14CO2 excretion and specific radioactivity of CO2 on the dietary lysine content was observed.     

A first estimate of the amino acid requirement for milk production of the high-producing female mink (Mustela vison)

Thirty mink dams nursing litters of six kits were assigned to one of three dietary treatments [high protein (HP), medium protein (MP) and low protein (LP)], fed ad libitum for 4 week from parturition, to investigate the effects of protein supply on milk yield and milk composition in order to estimate the amino acid requirement of the lactating mink. Twelve dams were held in an intensive care unit and subjected to balance experiments and the kits were injected with deuterium oxide to determine water kinetics and milk yield. Eighteen dams were kept under normal farm conditions but with feed intake of dams and live weight gain of kits being determined and milk samples collected. The ME intake was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet, whereas the amino acid intake (g/day) was lowest (p < 0.05) in dams fed the LP diet. In the third and fourth weeks of lactation milk yield was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet. Chemical composition of milk was not affected (p > 0.05) by dietary treatment. However, protein content tended (p = 0.06) to be lower in dams fed the LP diet. Amino acid content (g/16 g N) of milk was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet. This resulted in the highest (p < 0.05) amino acid intake and highest (p < 0.001) live weights of kits nursed by dams fed the LP and MP diets, which may be explained by a combined effect of higher ME intake and reduced energetic costs for glucose production through less amino acids being used in gluconeogenesis. In conclusion, the improved performance of dams fed the LP diet suggested that their requirement of essential amino acids and non-specific N were covered, and the requirement of digestible amino acids of lactating mink (kg(0.75)) was, thereby, estimated by use of a factorial approach including the amino acid excretion in milk of LP dams.     

Action of proteinase inhibitors in rats. 3. Influence of leupeptin on the rate of protein synthesis and the intracellular protein degradation by use of a test system including constant infusion of labelled amino acids, estimation of 3-methyl-histidine excretion and a triple-labelling technique

Male Wistar rats (initial body weight 90 g) were fed ad libitum a whole-egg diet containing 10,5% crude protein. The animals of the experimental group received in each case of 1 mg leupeptin per 100 g of body weight in 12 hrs-intervals by i. p.-injection (3 days of treatment). Control animals got a leupeptin free solution. In addition, lysine dihydrochloride-alpha-15N was applied during the first three days of experiment to all animals and the nitrogen balance was determined. Urine from the N-Balance collection was analysed for 3-methyl-histidine excretion in order to calculate the degradation rate of myofibrillar proteins. On the fourth day the fractional rate of protein synthesis in several organs was estimated using the continuous infusion technique with 14C-leucine and 14C-lysine. The apparent biological half-lives of tissue protein were determined by a triple labelling technique, with (14C)-guanidino-L-arginine, L-5-3H-arginine and 15N-Lysine. The short-term treatment 3 days) with leupeptin did not affect the weight gain, the apparent digestibility of nitrogen and the N-balance. The fractional rate of protein synthesis was highest in the small intestine followed by the large intestine, liver and skeletal muscle and no influence of leupeptin treatment was observed. Furthermore no differences in the degradation rates of myofibrillar proteins between treated and untreated animals were found. The 3-methyl-histidine excretion via urine was 1.44 mg . kg-1 day-1 in both groups corresponding to a fractional rate of degradation of myofibrillar proteins of 2,5% per day. Apparent half-lives of tissue proteins in the small intestine, large intestine and liver, respectively, were shortest when estimated from the decay curves for the 14C-label and longest from the curves for the 15N-label. Leupeptin treatment resulted in prolonged apparent half-lives of the proteins in the large intestine and of the slowly turning over proteins in the liver. However, this effect seems to be caused rather by an increased reutilization of labelled amino acids than by a decreased protein degradation. Before continuing this kind of work the rate of uptake of injected leupeptine into tissues has to be investigated. Studies dealing with the in vivo action of proteinase inhibitors on protein metabolism have to include estimations of N-balance, protein synthesis rate, intracellular degradation rate of proteins as well as amino acid reutilization.     

Dynamics of amino acid and protein metabolism of laying hens after the administration of 15N-labeled wheat protein. 1.Problems, research program and 15N-labeling of urine

In a 6-day preliminary period with a pelleted ration 12 colostomized laying hybrids received 15N labelled wheat protein over 4 days. The labelling of the wheat was 14.37 atom-% 15N excess (15N'). During the 4-day application of 15N wheat protein each hen consumed 12.08 g nitrogen, 3.52 g lysine, 2.12 g histidine, 4.41 g arginine, of which were 540 mg 15N', 18.1 mg lysine 15N', 21.5 mg histidine 15N' and 47.9 mg arginine 15N'. Heavy nitrogen was determined in urine and its uric acid-N in the daily urine samples of the individual animals. The average daily urine N excretion was 54% of the total nitrogen consumed with the ration. The labelling of the urine N reached a plateau on the fourth day of the experiment with 3.2 atom-% 15N'. On an average of the total experiment the quota of heavy nitrogen of the uric acid in the total 15N' of the urine was 83.4% and that of uric acid nitrogen in the total urine nitrogen 80.8%.     

Utilization of 15N-labeled urea in laying hens. 8. 15N-incorporation in the amino acids of the oviduct

3 colostomized laying hybrids received orally with a conventional ration 1% urea with 96.06 atom-% 15N excess (15N'). over a period of 6 days. In the period of the experiment every hen consumed 2.87 g 15N'. After another 2 days, on which they received conventional feed urea, the animals were butchered. 15N' was determined in the total N and in 15 amino acids of the oviduct. Of the 15 amino acids the labelling of glutamic acid, glycine and serine was highest and on average amounted to 0.80, 0.66 and 0.67 atom-% 15N'. In lysine and arginine only 0.10 and 0.11 atom-% 15N' could be detected. The amino acid N with natural isotopic frequency amounted to a quarter for the basic amino acids, a tenth for the branched chain ones and for the non-essential ones (glutamic acid, aspartic acid, serine, glycine, alanine, proline) a third of the total oviduct 14N, The average quota of 15N' is only 3.6%, that of the branched chain amino acids 4.5 and that of the non-essential ones 21.1%. Consequently, the 15N' of the urea is mainly used for the synthesis of the non-essential amino acids of the oviduct.     

Efficiency of amino acid utilization in the growing pig at suboptimal levels of intake: lysine, threonine, sulphur amino acids and tryptophan

A series of N balance experiments using growing pigs was conducted to study the efficiency of utilization of lysine, threonine, sulphur amino acids and tryptophan and to estimate their maintenance requirements. Purified diets based on casein and crystalline amino acids as the sole source of N contained graded levels of each amino acid, corresponding to expected protein accretion rate of 0, 33, 66, 99 and 132 g/day, respectively. N retention increased linearly (p < 0.01) as the dietary concentration of the limiting amino acid increased. Based on linear regression equations relating amino acid deposition in body protein to amino acid intake, marginal efficiencies of ileal digestible amino acid utilization were calculated to be lysine 0.91, threonine 0.83, sulphur amino acids 0.85 and tryptophan 0.66. Extrapolating the regression equations to zero N retention, the daily requirements of amino acids for N equilibrium were estimated to be (mg/kg(0.75)) lysine 39, threonine 49, sulphur amino acids 46 and tryptophan 16.     

Activity of and requirement for selected amino acids in growing female pigs. 1. Lysine

In N balance experiments with a total 59 growing female pigs in the live weight range of 33 to 55 kg the lysine efficiency (bc-1 value) and the lysine efficiency coefficient (kLys) of various cereal proteins were ascertained under the consideration of various charges and varieties. The range of kLys = 0.65 ... 0.96 shows a wide spectrum of lysine efficiency, which results in an analogous differentiation of the derived lysine requirement values. Assuming kLys = 1.0 (lysine efficiency 100%, i.e. the maximum value for bc-1 found as yet for native proteins) a daily lysine requirement (efficient amino acid) of 8.9, 10.8 and 12.6 g resp. was ascertained for 100 g daily protein retention at 30, 40 and 50 kg live weight resp.     

The effect of straw meal on the crude protein and amino acid metabolism and the digestibility of crude nutrients in broiler breeding hens. 3. Digestibility of amino acids

In two experiments with colostomized broiler hens the influence of a straw meal supplement on the apparent digestibility of the amino acids of the ration and the 15N labelled basic amino acids in wheat was studied. In experiment 1 the animals received 120 g mixed feed plus 0, 20, 30 and 40 g straw meal per animal and day. The digestibility of the amino acids decreased on average from 86% to 83%, 80% and 79% with the growing straw intake. In contrast to the control variant, 20 g straw meal intake resulted in a significant decrease of digestibility for lysine, histidine, glycine, tyrosine, phenylalanine, cystine and methionine. 30 and 40 g straw meal reduced significantly the digestibility of all amino acids with the exception of arginine. The amino acid composition of the crude protein in faeces changed only very slightly due to the straw supplement. In experiment 2 15N labelled wheat was a component of the ration. Of the 15N labelled amino acids lysine, histidine and arginine, 88, 90 and 95% were apparently digested. The adaptation of the animals to straw meal intake did not change the digestibility of the amino acids.     

Dynamics of amino acid and protein metabolism in laying hens after the administration of 15N-labeled wheat protein. 2. 15N excretion with nitrogen and basic amino acids of the feces

Over 4 days 12 colostomized laying hens received together with a commercial ration labelled wheat with a 15N excess (15N') of 14.37 atom-%. The labelling of the basic amino acids amounted to 13.58 atom-% for lysine, to 14.38 atom-% for histidine and to 13.63 atom-% 15N' for arginine. 3 animals each were butchered 12 h, 36 h, 60 h and 108 h resp. after the last application of 15N. The heavy nitrogen in the total N and in the N fraction of non-protein origin as well as in the basic amino acids in faeces was daily determined for the individual hens in the total experimental period. On average the crude protein of faeces contained 5.45 % lysine, 2.32% histidine histidine and 3.68% arginine: the protein of faeces correspondingly contained 5.43% lysine, 2.32% histidine and 4.07% arginine. The quota of TCA soluble N in the total N of faeces amounts to one third on the 3rd und 4th days of the experiment and that of 15N' to 28%. The average atom-% 15N' of the protein fraction is 3.48 atom-% 15N' and that of the non-protein N fraction of faeces 2.93 atom-% 15N'. The apparent digestibility and that of the non-protein N fraction of faeces 2.93 atom-% 15N'. The apparent digestibility of the 14N of the ration on average amounts to 82.8% and that of the wheat 15N' to 87.5%. The average quota of the basic amino acids in the protein compounds of faeces amounts to 70.9% for lysine 15N', 73.7% for histidine 15N' and 70.3% for arginine 15N'. The digestibility of the 15N labelled amino acids amounts to 80.4% for lysine, 90.8% for histidine and 90.2% for arginine.     

Methodologic aspects of the determination of N-exchange parameters from 15N-tracer studies in swine on the basis of models of N-metabolism. 3. Calculation of protein synthesis and decomposition rate on the basis of lysine flux, ascertained from the amount of 15N in the urine

The final product method introduced here is based on the use of 15N L-Lysine as tracer amino acid for the determination of the protein synthesis and decomposition quotas of the total body with the flux of lysine. For this purpose it is necessary to complete the N flow and N compartments of the 3-pool model by the values of lysine content. The ascertained values of protein synthesis--8.4 g/d/kg--and protein decomposition--6.9 g/d/kg--agree very well with those determined with 15N glycine as tracer amino acid.     

Physiologic and nutritional studies in pigs with ileorectal anastomoses. 3. Nitrogen retention and utilization following energy an electrolyte supplementation

In order to guarantee an equally good development of ileorectostomized pigs (IRA) used for the determination of precaecal protein digestibility and the absorption of amino acids as for intact animals (INT), the supplementation of their rations with easily soluble carbohydrates and minerals is necessary. The effects of these supplements on live weight development, nitrogen balance and N utilization level were the subject of the assessment of 21 rations with 129 and 117 balance measuring resp. with growing IRA and INT pigs. Without any supplementation of the rations the N balances of the IRA pigs showed significantly lower and partly negative N balances and N utilization levels in comparison to the INT pigs. The combined supplement of easily soluble carbohydrates (100 g/kg DM intake) and 300 ... 400 ml electrolyte solution per day (approximately 1 ... 1.3 g additional Na) resulted in N balances almost equal to those of INT pigs. The supplement of both electrolyte solution and NaHCO3 (approximately 2 g Na per animal and day additionally) to a barley + lysine ration resulted in a significant increase of the N balance and N utilization in IRA pigs of a live weight between 120 and 140 kg in contrast to the control period. A supplement of carbohydrates to a ration consisting of barley + fish meal + grass meal and electrolyte supplements of 400 ml per animal and day only resulted in significantly higher N balances and N utilization levels in the live weight range up to 70 kg in comparison to the control periods, which then corresponded to those of INT pigs. There was no essential influence of carbohydrate supplementations on pigs of more than 70 kg live weight. The postileal digestibility of the crude carbohydrates (CC) of 14 rations calculated from the difference between total digestibility (faecal analysis) and precaecal digestibility (analysis of the ileal chyme of IRA pigs) showed that between 40 and 100 g (70 g on average) out of the 780 g CC per kg DM consumed disappear in the large intestine. These studies show that in the testing of concentrates and mixed feed rations the supplementation of 100 g easily soluble carbohydrates/kg DM intake should be sufficient to guarantee a normal development of IRA pigs. In addition, an oral supply of 1 to 2 g sodium in the form of electrolyte solution exceeding the requirement of INT pigs is necessary as this supplementation significantly improves the N retention of IRA pigs even heavier than 100 kg.     

Lysine requirement of growing steers

Eight Limousin-cross steers (355 kg) were used in a replicated 4 x 4 Latin-square designed to estimate lysine requirements. Steers were fed a semipurified diet containing little ruminal escape protein. Treatments were abomasal infusions of 0, 8, 16, or 24 g/day L-lysine. All steers were additionally infused with 400 g/day dextrose and 285.9 g/day of an amino acid mix that contained (g/day) L-methionine (12.0), L-histidine (8.1), L-arginine (10.5), L-threonine (12.0), L-valine (18.0), L-isoleucine (13.8), L-leucine (27.3), L-phenylalanine (28.2), L-glutamic acid (76.5), glycine (76.5) and L-tryptophan (3.0); it had been demonstrated previously that when lysine was included in this infusion mixture, nutritional requirements of steers for maximal N retention were met or exceeded. Nitrogen retention averaged 38 g/day and was not affected by treatment, implying that the lysine requirement of steers was less than the 37.8 g/day lysine estimated to be absorbed from the small intestine when the basal diet was fed.     

Performance dependent lysine requirement of fattening pigs. 3. Effect of amino acid and energy intake on fat, protein and lysine deposition of swine

The gain in structural matter had a linear course with a corresponding feeding intensity and depending on the period of fattening. However, the animals given high-energy diets deposited 130 g protein per day during the first fattening period, this deposition being compensated in the course of further growth by a considerably lower deposition in the sense of aequifinality. Up to a live weight of 70 kg, animals subjected first to restricted feeding and then to fully balanced feeding revealed the highest protein deposition during the last period of fattening, this fact emphasizing the leanmeat character of the animal material used. The daily fat deposition was found clearly determined by energy intake and independent of amino acid supply. Lysine conversion was influenced by the intake of lysine and energy. Under feeding to norm it reached some 40 and 30% during the first and second periods of fattening, respectively.     

Methodologic studies on the metabolism-oriented determination of methionine requirements of broiler chickens

In a preliminary experiment the time course of 35S-excretion following a single injection of 35S-methionine in male broiler chickens was measured for 5 days. Within 2 days 65 to 69% of the amount of 35S excreted during the whole 5-day-period were recovered. Therefore, in the main experiment excrements for 35S measurement were collected only 2 days. During the main experiment starting 7 days posthatching 48 male broiler chickens received diets based on peas and wheat. The basal diet was supplemented with DL-methionine at 8 levels increasing the methionine content from 3.3 to 7.5 g/kg DM or 1,51 to 3.42 g/16 g N and the content of sulphur containing amino acids varied from 6.8 to 11.8 g/kg DM or 3.11 to 5.02 g/16 g N, respectively. Daily body weight gain was followed up to day 30 posthatching and N-balance was estimated during the 21st to 26th day posthatching. Up to day 26 a methionine content of 3.9 g/kg DM was sufficient for maximum weight gain. However, during the last period of the experiment highest weight gains were observed in animals receiving diets with 4.5 or more methionine/kg DM. Highest N-retention (1.2 g N/d) was measured if the diet contained 3.9 g methionine/kg DM or more. At day 28 posthatching 35S-methionine was injected intravenously and the subsequent 35S-excretion was measured. The 35S-excretion started to increase at a methionine content in the diet of 4.5 g/kg DM and continued to rise up to the highest methionine content of 7.5 g/kg DM. The metabolism oriented methionine requirement determination indicates for male broiler chickens at the beginning of the 5th week posthatching a methionine requirement of 3.9 to 4.5 g/kg DM (1.78 to 2.05 g/16 g N) and a requirement of S-containing amino acids of 7.4 to 8.0 g/kg DM (3.38 to 3.65 g/16 g N). The method used is potential in studying the age-dependent changes in methionine requirement.