[Nitrogen metabolism in growing swine with special reference to the efficacy of lysine from various lysine sources]

[Methodical investigations on evaluation of lysine utilization in pigs after extreme changes of protein quantity and quality]

Aim of investigations was to measure lysine utilisation under dietary conditions which could have negative effects on well known relation between limiting amino acid and level of N-utilisation. Incorrect conclusions about level of lysine availability (efficiency) could be drawn under such conditions. Therefore N-balance trials were done with 32 female pigs (35-45 LW, fitted with urine bladder catheters), based on semisynthetic diets (wheatgluten / cornstarch) supplemented with glutamic acid as additional nitrogen source. Lysine concentration in the protein was further reduced by this way near to N-balance +/- 0. Data calculation followed a further developed N-utilisation model from Gebhardt (1966). Experimental conditions resulted in disturbed relationships between lysine concentration and protein utilisation and led to the conclusion, that N-balance trials related to estimation of amino acid efficiency in feed proteins resp. to amino acid requirements should be realised under conditions of > 500 mg / LWkg0.67 daily N-balance connected with > 2000 mg/LWkg0.67 daily N-intake.

[Parameters of nitrogen metabolism for male broilers of Tetra 82 descent]

In several growth and N-balance experiments with male broilers of the genotype Tetra 82 the course of live weight and parameters of N-metabolism were investigated. Semi-synthetic feed mixtures of different protein concentration but equal protein quality (protein mixture: 70% soybean meal and 30% fish meal) were used in the trials. Data from N-balance investigations were reckoned up in the N-turnover model from Gebhardt (1963). The course of maximum (N-balance plus endogenous N-loss) capacity in dependence on live weight was regressive calculated. Based on this regression a possibility of calculation of efficiency depended protein and amino acid requirement for the whole fattening period in dependence on live weight, protein intake and protein quality (A.b) was illustrated.

[Mechanism of action of lysine in relation to its form of supply in swine]

It was the aim of this study to check the maximum value of lysine efficiency in feed proteins used as yet for the ascertainment of amino acid efficiency coefficients (cf. Liebert and Gebhardt 1988 b). For this purpose N balance measurements were carried out with 5 female pigs (30-35 kg LW) under conditions of continuous lysine infusion (duration of infusion 12 hours) through subclavian indwelling catheters with the help of a proven N utilization model. Based on defined limiting relations in the wheat/wheat gluten ration used, the lysine efficiency coefficient for infused lysine could be ascertained according to the difference method as 1.03, i.e., slightly above the maximum value for lysine efficiency determined up to now. The current standard of maximum lysine efficiency was determined as bc-1 Lys = 102, which is the basis of further calculations of lysine efficiency coefficients.

[Evaluation of the protein quality of silaged corn ear products with different crude fiber contents]

The assessment of the protein quality of silaged maize ear products was carried out on the basis of crude protein and amino acid analyses and of N balance measurings with growing pigs including comparative studies with maize corns and cereals. The differences found in the amino acid concentrations between the individual maize ear products could be verified on the basis of the analysed values of husks, cobs and corns. There were no significant differences in the parameters of total protein utilization (PNu, b-value) between the studied silages. The differing crude fibre content resulted, however, in reverse shifts in N excretion in faeces and urine, i.e. diminished protein digestibility was compensated by improved intermediary utilization.

[The effectiveness of and requirements for selected amino acids in growing female swine. 6. Summarizing discussion, evaluation and recommendations for use of the method presented]

Physiologically based statements on the effectivity of lysine, methionine/cystine and threonine of protein sources as well as on the requirement of these amino acids depending on performance were derived on the basis of a total of 568 N balance measurings at growing female fattening pigs in the live weight range between 30 and 50 kg (Liebert, 1986) with the application of the N utilization model by Gebhardt (1963) as well as of particular further developments by the linking of N utilization and the utilization of the respective limiting amino acid. By means of combining protein sources with known amino acid effectivity, the additivity principle for content values of effective amino acid in the feed protein (c.k) suggested as criteria was verified. On the whole, it could thus be proved that the suggested method can decisively contribute to the elaboration of a closed system of quality assessment and requirement assessment depending on performance as well as of supply covering requirements of growing pigs. The advantages in particular over the 'slope ratio' method are emphasized.

[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.

[The activity of and requirements for selected amino acids in growing female swine. 2. Methionine and cystine]

The methionine/cystine efficiency of ten protein sources including that of different charges of the same protein source was ascertained in N balance experiments with a total of 60 female pigs in the live weight range of 35-50 kg. The variability of the derived sulfur amino acids (SAS) efficiency coefficient (Csas) ranged between 0.64... 0.91 based on the SAS efficiency of casein as a standard. There was an analogous differentiation for the derived requirement values on the basis of the analysed methionine/cystine values of the proteins. For a protein retention of 100 g/day and a live weight of 40 kg, 6.2g methionine/cystine was ascertained based on the highest SAS efficiency (Csas = 1) as yet.

[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.

[Nitrogen and amino acid absorption in the small intestine of growing pigs. 2. Apparent and true crude protein digestibility and amino acid absorption to the end of the small intestine]

Studies of the apparent and true ileal digestibility of crude protein and the apparent and true amino acid (AA) absorption were carried out with 7 female pigs in the live weight range between 22 and 34 kg after ileorectostomy. Protein sources of varied quality with regard to the method of treatment (toasted) and untoasted soybean oilmeal) and to the AA composition (vital gluten or vital gluten + L-lysine X HCl) were used. Distinct differences regarding the apparent ileal digestibility of crude protein and the apparent absorption of amino acids were discovered between the protein sources, the cause of which is to be seen in the different amounts of endogenous N. The true ileal digestibility of crude protein and amino acid absorption were partly distinctly higher than the values of the apparent ileal digestibility of crude protein and AA absorption. On the whole one can say that the results of the investigation gained by means of ileorectostomy can be compared to the values gained from cannulated animals. Thus the experimental method used is suitable for studying the absorption process to the end of the small intestine of pigs.