Utilization of stereoisomers from alpha-tocopherol in livestock animals.

Alpha-tocopherol derived from natural source is a single stereoisomer (i.e. RRR-alpha-tocopherol), whereas synthetic alpha-tocopherol consists of a mixture of eight stereoisomers, including RRR-, RRS-, RSR-, RSS-alpha-tocopherol (the 2R isomers, R configuration at positions 2' of the phytyl tail) and SRR-, SSR-, SRS- and SSS-alpha-tocopherol (the 2S isomers, S configuration at positions 2' of the phytyl tail). R and S are assigned by the sequence-rule procedure, i.e. the priorities of the substituents decrease in clockwise direction or anti-clockwise direction at each chiral centre. Not all these stereoisomers are equally bio-available, which can be explained by the differences in the rate of degradation, transportation and retention. Humans and livestock animals can only utilize the 2R forms, while the 2S forms have very low bio-availability or basically are not bio-available. The utilization of 2R forms differs between different animal species. For humans and livestock animals, RRR-alpha-tocopherol has the highest bio-availability compared with other stereoisomers, while other 2R forms have lower bio-availability compared with RRR-alpha-tocopherol. The relative bio-availability of RRR- and all-rac-alpha-tocopherol is related to animal species, ages of animals and assessment criteria. In general, recent literature studies have demonstrated that the relative bioavailability of RRR- and all-rac-alpha-tocopherol is 2:1, differing from the commonly used conversion factor of 1.36:1. The latter was based on rat-resorption-gestation test. Most recent studies have shown that this conversion factor of 1.36:1 is not applicable to livestock animals and based on other metabolic functions. When IU is required to express vitamin E activity, new conversion factors need to be defined for livestock animals. Quantitative determination of bio-availability of the individual alpha-tocopherol stereoisomers will give a more detailed picture of the bioavailability of natural and synthetic vitamin E forms.

Bio-discrimination of alpha-tocopherol stereoisomers in rearing and veal calves fed milk replacer supplemented with all-rac-alpha-tocopheryl acetate.

This study evaluated the biological discrimination of different alpha-tocopherol stereoisomers (i. e. RRR-, RRS-, RSR-, RSS- and the four 2S-alpha-tocopherols) from all-rac-alpha-tocopheryl acetate supplementation in milk replacer for rearing and veal calves respectively, in practical farming conditions. Two experiments were conducted. In experiment 1, six rearing calves were fed milk replacer supplemented with 80 mg/kg all-rac-alpha-tocopheryl acetate for a period of 9 weeks. The calves were supplied calf starter concentrate from 1 to 12 weeks. In experiment 2, six veal calves were fed milk replacer supplemented with 80 mg/kg all-rac-alpha-tocopheryl acetate for a period of 24 weeks. Blood samples were taken at the start and every 4 weeks until 12 weeks for rearing calves in experiment 1, and until slaughter (24 weeks) for veal calves in experiment 2. Liver, adipose, muscle, and brain samples were taken at slaughter of the six veal calves in experiment 2. The distribution of different alpha-tocopherol stereoisomers in feed, plasma, and tissues was analyzed. In both experiments, it was observed that RRR-alpha-tocopherol was the dominant stereoisomer in plasma and tissues. The average percentage of the RRR-alpha-tocopherol stereoisomer was 64 %, and 39 % of the total alpha-tocopherol in plasma for rearing and veal calves, respectively. The higher RRR-alpha-tocopherol stereoisomer proportion as percentage of the total alpha-tocopherol in rearing calves was related to higher dietary natural vitamin E intake. Other 2R-alpha-tocopherol stereoisomers had lower utilization efficiency than RRR-alpha-tocopherol stereoisomer. 2S-alpha-tocopherol stereoisomers were basically not utilized by calves.

Expression of an abscisic acid-binding single-chain antibody influences the subcellular distribution of abscisic acid and leads to developmental changes in transgenic potato plants.

Potato (Solanum tuberosum L. cv. Désirée) plants were transformed to express a single-chain variable-fragment antibody against abscisic acid (ABA), and present in the endoplasmic reticulum at to up to 0.24% of the soluble leaf protein. The resulting transgenic plants were only able to grow normally at 95% humidity and moderate light. Four-week-old plants accumulated ABA to high extent, were retarded in growth and their leaves were smaller than those of control plants. Leaf stomatal conductivity was increased due to larger stomates. The subcellular concentrations of ABA in the chloroplast, cytoplasm and vacuole, and the apoplastic space of leaves were determined. In the 4-week-old transgenic plants the concentration of ABA not bound to the antibody was identical to that of control plants and the stomates were able to close in response to lower humidity of the atmosphere. A detailed analysis of age-dependent changes in plant metabolism showed that leaves of young transformed plants developed in ABA deficiency and leaves of older plants in ABA excess. Phenotypic changes developed in ABA deficiency partly disappeared in older plants.

Inhibition by light of CO(2) evolution from dark respiration: Comparison of two gas exchange methods.

Two approaches to determine the fraction (mu) of mitochondrial respiration sustained during illumination by measuring CO(2) gas exchange are compared. In single leaves, the respiration rate in the light ('day respiration' rate R(d)) is determined as the ordinate of the intersection point of A-c(i) curves at various photon flux densities and compared with the CO(2) evolution rate in darkness ('night respiration' rate R(n)). Alternatively, using leaves with varying values of CO(2) compensation concentration (Gamma), intracellular resistance (r(i)) and R(n), an average number for mu can be derived from the linear regression between Gamma and the product r(i)cR(n). Both methods also result in a number c* for that intercellular CO(2) concentration at which net CO(2) uptake rate is equal to -R(d). c* is an approximate value of the photocompensation point Gamma* (Gamma in the absence of mitochondrial respiration), which is related to the CO(2)/O(2) specificity factor of Rubisco S(c/o). The presuppositions and limitations for application of both approaches are discussed. In leaves of Nicotiana tabacum, at 22 degrees C, single leaf measurements resulted in mean values of mu = 0.71 and c(*) = 34 mumol mol(-1). At the photosynthetically active photon flux density of 960 mumol quanta m(-2) s(-1), nearly the same numbers were derived from the linear relationship between Gamma and r(i)cR(n). c* and R(d) determined by single leaf measurements varied between 31 and 41 mumol mol(-1) and between 0.37 and 1.22 mumol m(-2) s(-1), respectively. A highly significant negative correlation between c* and R(d) was found. From the regression equation we obtained estimates for Gamma* (39 mumol mol(-1)), S(c/o) (96.5 mol mol(-1)) and the mesophyll CO(2) transfer resistance (7.0 mol(-1) m(2) s).

Efficiency of a lysine-tryptophan blend as a tryptophan source in animal nutrition.

The use of L-tryptophan for balancing tryptophan deficient diets in animal feeding is currently impeded by the cost of feed-grade product. Recently ADM CORP. (Decatur, IL, USA) developed a method whereby liquid L-tryptophan and liquid L-lysine-HCl could be blended before drying. The final product contains at least 15% L-tryptophan and 70% L-lysine-HCl (Trademark Tryptosine). Experiments have been conducted with pigs and broilers to evaluate the efficiency of tryptophan from Tryptosine in comparison with feed grade L-tryptophan. Results indicated a clear tryptophan deficiency of the basal diet. Graded doses of tryptophan to the basal diet resulted in improvements in weight gain, daily feed intake and feed conversion rate. In pigs the differences in weight gain, feed intake and feed conversion rate between both tryptophan sources were not significant. In broilers feed intake with commercial L-tryptophan was higher than with Tryptosine. Weight gain, feed conversion rate and health state did not differ significantly between both sources. Protein deposition in broilers was significantly improved with dietary supplementation of 0.3 g/kg tryptophan, whereas the addition with 0.6 g/kg showed no further response. No differences were observed between both tryptophan sources. From the results of the two studies it was concluded that the biological activity of tryptophan from Tryptosine is equal to that of L-tryptophan for pigs and broilers.

Expression of a single-chain Fv antibody against abscisic acid creates a wilty phenotype in transgenic tobacco.

The plant hormone abscisic acid (ABA) participates in the control of several important physiological processes in plants such as stomata regulation, seed dormancy and stress tolerance. A new strategy was developed to study these phenomena by blocking abscisic acid with intracellularly expressed specific single-chain variable fragment (scFv) antibodies. Here evidence is presented that the expression of single-chain Fv antibodies against abscisic acid in the endoplasmic reticulum of transgenic tobacco cells leads to a wilty phenotype. Stomatal conductance is increased at high CO2 concentrations dependent on the level of antibody expression in leaves. Symptoms of abscisic acid deficiency were generated in the transformants although they have even higher levels of abscisic acid than wild-type plants.

[Effect of physical treatment of rapeseed expeller, wheat, corn and corn gluten feed on the degradability in the rumen and the enzymatic in vitro digestibility of nondegraded crude proteins]. / Einfluss der physikalischen Behandlung von Rapsexpeller, Weizen, Mais und Maiskleberfutter auf die Abbaubarkeit im Pansen und die enzymatische in-vitro-Verdaulichkeit des nichtabgebauten Rohproteins.

The influence of physical treatment-expansion and flaking-on crude proteins degradability in the rumen was studied in maize, maize-gluten feed, rape extracted meal and in the expanded one at 120 degrees C and 150 degrees C, rape cake, wheat and flaked wheat by in sacco method. The enzymatic digestibility of crude protein in the rumen undegraded residues of the above mentioned feeds was determined by an enzymatically in vitro method. The treatment of feed decreased significantly the original solubility and theoretical degradability of crude proteins, and the amount of undegraded crude proteins was increased. Positive influence on the amount of enzymatically digested crude protein was determined in rape expanded at 120 degrees C and 150 degrees C (60, 61 and/or 68%). Flaking of wheat had a similar effect. Enzymatic digestibility at undegraded rests where increased by 8-10% after the heat treatment and it remained almost unchanged in expanded maize-gluten feed.

[Relation between creatinine excretion in the urine and feed protein quality in the growing pig]. / Untersuchungen zum Zusammenhang zwischen Kreatininausscheidung im Harn und der Qualität des Nahrungsproteins bei wachsenden Schweinen.

N-balance experiments, in which creatinine excretion in urine was measured, were carried out with 80 female fattening pigs. 16 protein sources of different quality were used. In addition to that, an N-increase experiment--protein quality remaining the same--and N-free experiment and results from literature were included into the assessment. The b-value (Gebhardt, 1963) served as the criterion for protein quality. The creatinine coefficient (mg creatinine in urine per kg live weight and day) could be determined as 40.2. There was a direct relation between the N-balance value and creatinine excretion, not however, in the N-increase experiment. Significant relations to the protein quality (b-value, Gebhardt, 1963) could only be established when N-excretion in urine was included.