Discrimination of Adsorbed Double-Stranded and Single-Stranded DNA Molecules on Surfaces by Fluorescence Emission Spectroscopy Using Acridine Orange Dye.

A sensitive and straightforward method for discriminating between surface-adsorbed double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA), based on analysis of the fluorescence emission spectra of DNAs dyed with the metachromatic dye acridine orange, has been developed. Since the degree of discrimination between dsDNA and ssDNA is dependent on dye-base ratio (as has been shown in early studies of DNAs in solution), a specific, reproducible protocol for obtaining good ss-ds discrimination was needed. We studied the emission spectra for DNAs dyed in-situ on two different surfaces, polymethylmethacrylate and poly-l-lysine, using acridine orange solutions of varying concentrations in either 2-(N-morpholino)ethanesulfonic acid (MES) or Tris-Borate EDTA (TBE) buffers. The method should prove useful in characterizing the efficacy of denaturing techniques applied to surface-adsorbed DNAs in preparation for hybridization, replication and transcription experiments on stretched and aligned DNAs.

Expression of urea transporters is affected by dietary nitrogen restriction in goat kidney.

Ruminants are known to be able to very effectively recycle urinary urea and reuse it as a source of N for ruminal microbes. It is presumed that urea recycling is accomplished by specialized urea transporters (UT) which are localized in the kidney. This could be especially important in times of increased N requirement, such as during growth or during reduced dietary N intake. The aim of our study was to characterize and to localize UT in the goat (capra hircus) kidney and to investigate its response to reduced dietary N intake in growing goats. Therefore, 12 growing, male goats were fed either a diet containing high (17% CP in complete diet) or low (9% CP in complete diet) N content for 6 wk. After harvesting, blood and kidney samples were taken and analyzed. The mRNA of the different UT isoforms, UT-A1, UT-A2 and UT-B, were detected semiquantitatively in renal tissue by Northern blot analysis. For UT-A2 and UT-B, no statistically significant effect of dietary N restriction on renal mRNA expression could be detected (UT-A2: P = 0.26, UT-B: P = 0.07). However, renal mRNA abundance of UT-A1 significantly increased in the kidney of low-N-fed goats (P = 0.01). Furthermore, protein amounts of UT-B were verified by western blotting; and the localization of UT-A2 and UT-B protein was demonstrated by immunohistochemistry. No significant differences in protein amounts of UT-B could be observed comparing the 2 feeding groups (P = 0.78). The UT-B was localized in renal medulla and papilla, whereas UT-A2 was only found in renal medulla. In addition, comparison of UT-A and UT-BAA sequences of monogastric animals and ruminants showed a high degree of homology, indicating a similar function of the transporters among these species. In summary, we conclude that in ruminants, urea reabsorption in the kidney is most likely increased in response to a low-N diet via an upregulation of UT-A1 mRNA expression. Hypothetically, the reabsorbed urea can then be returned to the rumen via the bloodstream and thus be reused as a source of N for protein synthesis of ruminal microbial community.

Dietary protein reduction in sheep and goats: different effects on L-alanine and L-leucine transport across the brush-border membrane of jejunal enterocytes.

It was the aim of this study to examine the potential regulatory effects of a long-term low dietary protein supply on the transport capacity of the jejunal brush-border membrane for amino acids. For this purpose, we used the neutral amino acids L-alanine (representative for nonessential amino acids) and L-leucine (representative for essential amino acids) as model substances. Ten sheep lambs, 8 weeks of age and 19-27 kg body weight, were allotted to two dietary regimes with either adequate or reduced protein supply which was achieved by 17.9% and 9.7% of crude protein in the concentrated feed, respectively. The feeding periods were 4-6 weeks in length. Similarly, eight goat kids of 5-7 weeks of age and 8-14 kg body weight were allotted to either adequate (crude protein 20.1%, feeding period 9-12 weeks) or reduced protein supply (10.1%, feeding period 17-18 weeks). Dietary protein reduction in lambs caused a significant body weight loss of 0.6 +/- 0.7 kg, whereas the body weight in control animals increased by 1.9 +/- 0.7 kg (P<0.05). Plasma urea concentrations decreased significantly by 60% (low protein 2.3 +/- 0.1 versus control 5.7 +/- 0.2 mmol l(-1), P<0.001). In kids, reduction of dietary protein intake led to significant decreases of the daily weight gain by 48% from 181 +/- 8 g to 94 +/- 3 g (P<0.001) and daily dry matter intake by 27% from 568 +/- 13 g to 417 +/- 6 g (P<0.01). Respective urea concentrations in plasma were reduced by 77% from 5.2 +/- 0.4 to 1.2 +/- 0.2 mmol l(-1) (P<0.01). Kinetic analyses of the initial rates of alanine uptake into isolated jejunal brush-border membrane vesicles from sheep and goats as affected by low dietary protein supply yielded that the apparent Km was neither significantly different between the species nor significantly affected by the feeding regime thus ranging between 0.12 and 0.16 mmol.l(-1). Reduction of dietary protein, however, resulted in significantly decreased Vmax values of the transport system by 25-30%, irrespective of the species. Kinetic analyses of the initial rates of leucine uptake into jejunal brush-border membrane vesicles from sheep and goats yielded that leucine uptake was mediated by Na+-dependent as well as Na+-independent processes. Similar to alanine, apparent Km values of leucine uptake were neither different between the species nor affected due to low dietary protein and ranged between 0.08 and 0.15 mmol l(-1). In contrast to the alanine transport mechanism, dietary protein reduction resulted in increased Vmax values of Na+-dependent leucine transport by 53% in sheep and 230% in goats. Similarly, Na+-independent leucine uptake was stimulated by 85% and 200% in sheep and in goats, respectively. This study shows adaptation of amino acid absorption at the brush-border membrane level of jejunal enterocytes of small ruminants due to dietary protein reduction. Whereas the transport capacity for the nonessential amino acid alanine was reduced due to low dietary protein, the transport capacity for the essential amino acid leucine was markedly stimulated. From this, the involvement of rather different feedback mechanisms in adaptation of intestinal amino acid transport mechanisms has to be discussed.

Effects of raw and heat-treated bambara groundnut (Vigna subterranea) on the performance and body composition of growing broiler chicks.

Bambara groundnut (Vigna subterannea)--a leguminous root nut, which grows in the tropics and subtropics--was used in an experiment to test its effect on the performance of growing broiler chicks. Performance was measured by monitoring growth, measuring nutrients and energy balances and also by determining nutrient accretion. Twelve-day old broiler chicks, kept in individual metabolic cages, were used in an experiment in which birds were equally allotted (n = 10) into a control (fed high performance diet made up principally of wheat and soybean meal) and 6 test groups fed diets containing 19, 76 and 95% raw or autoclaved bambara groundnuts. All diets were similar in energy, nitrogen and total lipid contents. Diets were also balanced for amino acids, vitamins and minerals in accordance to the specific requirements of the birds. Feed and water were provided ad libitum. Growth performance was monitored over 15 days. Nutrient and energy balances were measured by use of TiO2 as marker. The comparative slaughter technique was implored for the determination of energy and nutrient accretion. The results showed that the level of raw or autoclaved bambara had no significant influence on feed intake. Increasing the bambara level in the diets caused a general linear drop in the performance of the broilers. However, with up to 95% bambara in the diet, the general performance was still above 75% compared to the control. Increasing levels of bambara groundnut caused a decrease in the metabolizability of energy and efficiency of utilisation of ME for BWG. The animals retained more water with increasing levels of raw bambara in the diets while autoclaving increased their DM content to levels comparable to the control. The protein composition of gain was comparable at all levels of inclusion. In general autoclaving improved the performance of bambara.

The effect of dietary crude protein level on intake, growth, protein retention and utilization of growing male Saanen kids.

The effects of increasing dietary levels of crude protein on growth, feed intake, feed efficiency and composition of gain in male Saanen kids were studied. Four groups of four kids each initially weighing 12.1+/-0.18kg and having a weight gain of 195+/-16g/d were penned individually and fed for 73 to 124 days up to 25kg of BW. They were fed chaffed wheat straw (45g CP/kg DM) which had been molasses sprayed (10%) and pelleted concentrates containing 8.7, 11.7, 14.4 and 17.6% crude protein (CP) on DM basis, the ratio of straw to concentrate being 1:5. Kids were fed controlled to satiation in which case small amounts of the feeds were offered about five times a day as long as the kids wanted to eat. Retention of protein, fat and energy were calculated from their initial and final concentrations in the empty body homogenates of the slaughtered kids. With increasing CP level in the diet, feed intake increased from 448 to 608g DM/d, weight gain from 94 to 181g/d, retention of protein from 9.7 to 27.8g/d, retention of fat from 9.6 to 19.1g/d and feed efficiency improved from 4.79 to 3.39kg DM/kg weight gain. Protein composition of gain increased from 103 to 154g/kg BWG while fat (103-105g/kg BWG) remained constant. Regression analyses showed that BWG can be optimized at 136g CP/kg DM and protein retention at 180g CP/kg DM, whereas, dietary nitrogen was utilized most efficiently at 120g CP/kg DM. Extrapolated from the regression equations, maintenance N requirement of the kids at zero N-retention and at zero BWG were 0.38 and 0.16g N/kg W(0.75), respectively. Recommended dietary CP concentrations and maintenance N requirements depend on the traits desired.

Effect of body weight on phosphorus digestibility and efficacy of a microbial phytase in young pigs.

The effect of body weight on P digestibility and on efficacy of supplemental Aspergillus niger phytase was studied in two experiments with young growing pigs. Excreta were collected quantitatively. All diets contained 2.0 g digestible P per kg dry matter at a maximum and renal P excretion never exceeded 15 mg/d. When dietary P mainly originated from monocalcium-phosphate, both P digestibility and Ca net absorption linearly increased by 3.6 and 5.6 percentage units, respectively, when BW increased from 15 to 35 kg. With a similar range in BW, P digestibility and Ca net absorption were unaffected by BW when P mainly originated from maize, barley and soybean meal. In both types of diet, crude protein digestibility increased with increasing body weight, whereas organic matter digestibility was effected by BW only in the diet containing maize, barley and soybean meal. Phytase (400 U/kg) almost doubled P digestibility when supplemented to a diet with P mainly originating from maize, soybean meal and barley. This effect of phytase supplementation was equal in pigs at 15.7 kg BW (33 vs. 55%) and at 39.1 kg BW (32 vs. 56%). Digestibility of any organic fraction was unaffected by supplemental phytase. With regard to on-farm conditions, it appears eligible from this results to apply digestibility coefficients for P determined in growing-finishing pigs for piglets as well.

The course of phosphorus excretion in growing pigs fed continuously increasing phosphorus concentrations after a phosphorus depletion.

A balance study was performed in order to quantify the effect of continuously increased phosphorus (P) intake on faecal and urinary P excretion. The aim was to quantify the level of intake where regulatory P excretion becomes relevant for comparative digestibility measurements on P, and when the pig adapts its urinary P excretion to increased P intake. Phosphorus intake of growing pigs was continuously increased on a daily basis starting at a marginal level and P excretion via faeces and urine was continuously followed for 92 days. Two semi-synthetic diets were prepared with different proportions of Na2HPO4 resulting in 2.4 (diet 1) and 6.3 (diet 2) g P/kg DM. Concentration of Ca was adapted to achieve a Ca supply approximately 3.1 fold the digestible P supply. Six castrated male crossbred pigs (31 kg BW) were kept individually in metabolism crates after they had undergone a 14 d P depletion period during which they were fed diet 1 solely. Pigs received 1.04kg of diet 1 per day throughout the experiment, and each day the amount of feed and P supplied to pigs from diet 2 was increased by 12 g and 69 mg, respectively. ME supply was approximately 2.4 fold maintenance and average daily BW gain of pigs during the entire experiment was 690 +/- 30 g. While intake increased linearly, faecal excretion of P and Ca increased non-linearly and could be best described by third order polynomial functions. The proportion of ingested P not excreted via faeces followed a quadratic type of curve with a maximum of 81% at 25 days on experiment and P intake of 4.0 g/d. Thereafter, the proportion decreased continuously. The digestibility of P from diet 2, determined by the slope ratio technique, was constant and not affected by P intake up to a P intake of 5 g/d. Renal P excretion did not exceed inevitable losses until day 60 and increased exponentially thereafter when body P reserves were restored. It is concluded, that an adaptation to surplus P supply occurred earlier on the intestinal than on the renal level. While faecal P excretion appeared regulated depending on the actual requirement for P retention, the regulation via urine depended on the P status of the pig. Once the renal P excretion of growing pigs exceeds a level of 25 mg/d, intake of digestible P cannot be regarded sufficiently low to measure P digestibility as a capacity of the feedstuff.

Inevitable losses of phosphorus in pigs, estimated from balance data using diets deficient in phosphorus.

Faecal losses of phosphorus (P) were determined in 66 growing pigs weighing between 30 and 70 kg on a semi-purified diet containing less than 1.3 g P/kg DM. Regression analysis showed that the coefficient of absorption of P from this diet was 82.5% and that inevitable faecal P excretion of pigs fed this diet was, on average, 5.9 mg/kg BW.d-1 with no statistically significant effect of body weight on faecal P excretion within the range of body weight studied. Semi-purified diets almost identical in composition were also fed to 5 piglets weighing about 20 kg and to 4 heavy pigs of about 150 kg BW. Inevitable daily faecal losses of P were calculated to be 6.2 mg/kg BW in piglets and 6.8 mg/kg BW in the heavy pigs. It is concluded that inevitable faecal losses of P do depend on body weight and that the variation faecal P excretion was too great to allow detecting this effect within the limited range between 30 and 70 kg BW. Further diets were obtained by blending various ingredients into the semi-purified diet. From a total of 262 balances measured under the condition of suboptimal P supply it is concluded that daily inevitable urinary losses of P depend on body weight and, on average, amount to 0.35 mg/kg BW. It is concluded that under the conditions of suboptimal P supply the utilisation of digestible P is almost complete.

Response of rainbow trout (Oncorhynchus mykiss) to supplements of individual essential amino acids in a semipurified diet, including an estimate of the maintenance requirement for essential amino acids.

We studied the effects of increasing dietary concentrations of each of the following amino acids on growth, feed intake, feed conversion ratio and composition of gain in rainbow trout in six dose-response experiments: L-lysine, L-tryptophan, L-histidine, L-valine, L-leucine and L-isoleucine. Semipurified diets containing 20.1 MJ digestible energy/kg dry matter, with wheat gluten and crystalline amino acids as sole sources of amino acids, were fed to rainbow trout [initial mean body weight (BW) 40-51 g, depending on the amino acid studied]. In one series of 24 diets, lysine concentration ranged from 4.5 to 58.0 g/kg dry matter; in five further series of 12 diets each, concentrations ranged from (in g/kg dry matter): tryptophan, 1.3 to 5.6; histidine, 2.6 to 13.5; valine, 6.2 to 34.2; leucine, 10.0 to 42.0 and isoleucine, 5.0 to 15.3. Each diet was fed to a group of 20 fish for 53-64 d, depending on the amino acid studied. Dry matter intake, weight gain, feed conversion ratio, protein concentration of gain and total protein deposition followed exponential response functions. To achieve 95% of the maximum protein deposition, dietary concentrations of 27.7 g lysine, 2.0 g tryptophan, 5.8 g histidine, 15.7 g valine, 13.6 g leucine and 13.7 g isoleucine/kg dry matter were required. Maintenance requirements, estimated from exponential functions for protein deposition, were [in mg/(100 g BW.d)]: lysine, 1.93; tryptophan, 1.05; histidine, 1.07; valine, 2.92; leucine, 8.26 and isoleucine, 0.91. This corresponds to 4% of the requirement for protein deposition for lysine and isoleucine but 32% for leucine, with the other amino acids being intermediate. Therefore, different dietary amino acid requirement patterns were derived from protein deposition data depending on the chosen level of performance.

[Influence of the ration content on the fecal phosphorus excretion of growing bulls varying in body weight]. / Einfluss der Rationsgestaltung auf die faecale Phosphorausscheidung bei unterschiedlich schweren Mastbullen.

Five smaller (body weight: 227.9 +/- 23.7 kg) and large growing bulls (435.2 +/- 14.3 kg per animal) each were fed with rations rich (chopped wheat straw:concentrate = 1:1) or poor in roughage (straw: concentrate = 1:4). Animals were kept in balance cages; 20 days adaptation period were followed by 10 days collection period. Body weight of bulls did not significantly influence apparent digestibility of rations. digestibility of organic matter of fibre rich ration was significantly lower (66.8%) than those of concentrate rich ration (74.4%). Feeding and body weight did not significantly influence metabolic parameters of mineral status. The fecal P-excretion amounted to 0.94 and 1.08 g per kg DMI in bulls fed with rations rich and poor in roughage. No influence of body weight was measured. Feeding and body weight did not significantly influence fecal P-excretion per kg DOMI (between 1.44 and 1.58 g P/kg DOM). For calculation of P-requirements for growing cattle fecal P-excretion amounted to 1.0 or 1.5 g P/kg DM and DOMI, respectively.

In vitro studies on calcium absorption from the gastrointestinal tract in small ruminants.

Unidirectional flux rates of Ca2+ across gastrointestinal tissues from sheep and goats were measured in vitro by applying the Ussing-chamber technique. Except for the sheep duodenum, mucosal to serosal Ca2+ flux rates (Jms) exceeded respective flux rates in the opposite direction (Jsm) in both species and in all segments of the intestinal tract. This resulted in net Ca2+ flux rates (Jnet = Jms-Jsm) ranging between -2 and 9 nmol.cm-2.h-1 in sheep and between 10 and 15 nmol cm-2.h-1 in goats. In sheep, only Jnet in jejunum, and in goats, Jnet in duodenum and jejunum were significantly different from zero. Using sheep rumen wall epithelia, significant Jnet of Ca2+ of around 5 nmol.cm-2.h-1 could be detected. Since the experiments were carried out in the absence of an electrochemical gradient, significant net Ca2+ absorption clearly indicates the presence of active mechanisms for Ca2+ transport. Dietary Ca depletion caused increased calcitriol plasma concentrations and induced significant stimulations of net Ca2+ absorption in goat rumen. Jnet of Ca2+ across goat rumen epithelia was significantly reduced by 1 mmol.l-1 verapamil in the mucosal buffer solution. In conclusion, there is clear evidence for the rumen as a main site for active Ca2+ absorption in small ruminants. Stimulation of active Ca2+ absorption by increased plasma calcitriol levels and inhibition by mucosal verapamil suggest mechanistic and regulatory similarities to active Ca2+ transport as described for the upper small intestines of monogastric species.

Effects of varying dietary calcium and phosphorus on growth and on composition of empty bodies and isolated bones of male kids.

Two experiments, each following a two-factorial design (2 x 2), were carried out using 12 and 13 male kids initially weighing about 10 kg. Concentrations per kg dietary dry matter were 10 vs. 4 g Ca and 4.5 vs. 2.0 g P in experiment 1 as compared to 10 vs. 17 g Ca and 4.2 vs. 2.5 g P in experiment 2, respectively. In experiment 1, low Ca intake significantly reduced empty body concentrations of ash, Ca and P with no negative effect on performance traits, whereas low P intake negatively affected feed intake, growth rate and feed conversion ratio, and reduced empty body concentrations of ash, Ca, P and Mg. Low intake of either one or both of these elements increased lipid concentrations of femora, pelvis and vertebrae. In these three bones, the respective ratios Ca/P, Ca/Mg and P/Mg were decreased by low Ca intake and, to greater extents, increased by low P intake. Low intake of both elements caused less pronounced changes than low intake of P alone. In experiment 2, lowering dietary P concentration to 2.5 g/kg dry matter significantly reduced growth rates without affecting empty body concentrations of ash, Ca, P or Mg. Almost doubling Ca intake significantly increased body concentrations of ash, Ca and P at both levels of P intake without influencing growth rates.

Mechanisms of intestinal phosphate transport in small ruminants.

In order to study the localization and mechanisms of intestinal phosphate transport in sheep and goats, unidirectional inorganic phosphate (Pi) flux rates across isolated stripped epithelial tissues were measured in vitro by applying the Ussing-chamber technique. In the first experiment the tissues were obtained from animals which had been kept on an adequate dietary P supply. In the second experiment the animals had either been kept on an adequate Ca and P supply or were Ca- and/or P-depleted. Significant net Pi absorption was measured in all segments of the small intestine and in the proximal colon of sheep and in the duodenum and jejunum of goats. Since the experiments were carried out in the absence of any electrochemical gradient, this clearly indicates the presence of active mechanisms for Pi transport in the intestinal tract of small ruminants. In sheep jejunum, reduction of mucosal Na concentration to 1.8 mM or serosal application of ouabain (0.1 mM) resulted in significant decreases of net Pi absorption of the same order of magnitude, indicating that about 65% of active Pi transport in sheep jejunum is mediated by a Na-dependent active transport mechanism. The mechanism for the remaining Na(+)-independent active Pi transport has not yet been identified. Dietary P depletion caused hypophosphataemia and induced a significant stimulation of net Pi absorption in goat duodenum and jejunum. This increase was independent of dietary Ca supply and was not associated with increased plasma calcitriol concentrations. This suggests substantial differences in hormonal regulation of Pi transport in small ruminants in comparison with single-stomached species.

Binding properties of goat intestinal vitamin D receptors as affected by dietary calcium and/or phosphorus depletion.

The binding capacity (Bmax) and the affinity (Kd) of the intestinal vitamin D receptor (VDR) have been studied using mucosa preparations from the duodenum, jejunum and proximal colon of male growing goats which had been kept in a two-factorial (2 x 2) trial on Ca and/or P deficient diets for 9 weeks. This treatment resulted in significant changes of different parameters of Ca and P homeostasis. Irrespective from the level of Ca intake, P depletion caused significant hypophosphatemia with corresponding hypercalcemia. In both Ca depleted groups the calcitriol concentrations in plasma significantly increased by more than 100% in comparison with normal Ca supply. No changes were recorded for plasma calcitriol concentrations in response to P depletion with an adequate Ca supply. Plasma PTH levels were only increased significantly in Ca depletion with adequate P supply. Irrespective of different feeding regimens, the highest Bmax values were found in the jejunum. In all intestinal segments tested, the Bmax values were significantly decreased by P depletion as compared with an adequate P supply. No effects on the Bmax of VDR were observed in response to changes of Ca supply. The Kd values of the VDR were neither affected by different intestinal localizations nor by Ca and/or P depletion. From the present results, it has to be concluded that the physiological relevance of VDR down-regulation may not be related to P homeostasis rather than to Ca homeostasis by minimizing the hypercalcemia induced by P depletion.

Free amino acids can replace protein-bound amino acids in test diets for studies in rainbow trout (Oncorhynchus mykiss).

Effects of reducing dietary concentration of protein-bound amino acids on growth, feed intake and composition of gain in rainbow trout were studied in four experiments. Average initial body weights ranged between 29 +/- 0.7 and 55 +/- 0.5 g per trout. Diets contained approximately 20 MJ digestible energy/kg dry matter. Each diet was fed to satiation to four replicate groups of 20 trout. Feed intake and growth rates were recorded for each group. Body composition was analyzed in representative groups at the start of each experiment and in all experimental groups at the end of each experiment. Reduction of dietary protein concentration to < 380 g/kg dry matter caused significantly lower growth rates and reduced protein concentrations of gain, but these reductions in growth could be offset by the addition of 10 crystalline essential amino acids. Fish meal was completely replaced by a mixture of wheat gluten and crystalline amino acids without negative influences on growth. In the absence of fish meal, almost half the wheat gluten could be replaced by crystalline amino acids in diets containing about 32 g N x 6.25/kg dry matter without significant influences on growth. In such diets, concentrations of individual amino acids may be varied widely with no variation in other amino acids or nutrients.

Response of rainbow trout (Oncorhynchus mykiss) growing from 50 to 150 g to supplements of DL-methionine in a semipurified diet containing low or high levels of cystine.

We studied the effect of increasing dietary concentrations of DL-methionine on growth, feed intake, feed conversion ratio and the composition of gain in rainbow trout. Twenty-four groups of 20 trout initially weighing 51 +/- 0.5 g/trout were fed semipurified diets containing 20.1 MJ digestible energy and either 3.0 or 5.8 g cystine/kg dry matter. At each level of cystine, 12 levels of methionine (2 to 11 g/kg dry matter) were achieved by supplementation with graded quantities of DL-methionine. During an experiment of 49 feeding days, no significant effect of the level of dietary cystine was found for any performance trait. Nonlinear responses to increasing dietary methionine concentrations were found for feed intake, growth rate, protein concentration of gain and protein deposition, whereas fat concentration of gain decreased concurrently. Dietary methionine was utilized most efficiently at a concentration of 3.5 g methionine/kg dry matter or 0.17 g/MJ digestible energy. Ninety-five percent of the plateau deposition of body protein was achieved at a dietary methionine concentration of 8 g/kg dry matter or 0.40 g/MJ digestible energy. For achieving 98%, the required concentration was 9.0 g/kg or 0.49 g/MJ. Recommended dietary methionine concentration will depend on the trait chosen.

Response of rainbow trout (Oncorhynchus mykiss) growing from 50 to 170 g to supplements of either L-arginine or L-threonine in a semipurified diet.

We studied the effects of increasing dietary concentrations of either L-arginine or L-threonine on growth, feed intake, feed conversion ratio and composition of gain in rainbow trout. Semipurified diets containing 20.1 MJ digestible energy/kg dry matter, with wheat gluten and crystalline amino acids as sole sources of amino acids, were fed to rainbow trout (initial mean body weight 47 +/- 0.7 g). In one series of 12 diets, arginine concentration ranged from 5.0 to 23.8 g/kg dry matter; in a second series of 12 diets, threonine concentration ranged from 3.7 to 21.0 g/kg dry matter. Each diet was fed to a group of 20 fish. During the experiment of 51 feeding days, dry matter intake, weight gain, feed conversion ratio, protein concentration of gain and total protein deposition followed exponential functions. For achieving 95% of the potential maximum protein deposition, dietary concentrations of 11.6 g arginine and 10.4 g threonine/kg dry matter were required. Arginine and threonine were both utilized most efficiently at dietary concentrations of approximately 6 g/kg dry matter. At low dietary concentrations of arginine, deposition of this amino acid exceeded the quantity fed. Recommended dietary concentrations of arginine and threonine will depend on the trait desired in the trout.

[Effect of a supplemental Aspergillus niger phytase on the utilization of plant phosphorus by rainbow trout (Oncorhynchus mykiss)]. / Einfluss des Zusatzes einer Aspergillus niger-Phytase auf die Verwertung Pflanzlichen Phosphors durch die Forelle (Oncorhynchus mykiss).

Effects of a supplemental Aspergillus niger-phytase on digestibility and utilization of dietary phosphorus (P) were studied in three experiments with rainbow trout. P concentration in the diets was 4.8 and 5.8 g/kg DM, respectively. The P contained in the diet originated solely from plants, mainly soy-products. Digestibility of P was studied using the stripping method and hydrochloride insoluble ash as marker. Utilization was studied in growth trials by use of the comparative body analysis. At a water temperature of 15 degrees C, both digestibility and utilization of P were increased from 25 to 57% and from 17 to 49%, respectively when 1000 U/kg phytase were supplemented. Feed consumption and gain of trout were significantly increased. At a water temperature of 10 degrees C, utilization of P was also increased from 6 to 25%. However, feed consumption and gain of trout were very low at this water temperature and not influenced by the supplemental phytase.

Effects of drastic changes in P intake on P concentrations in blood and rumen fluid of lactating ruminants.

The course of inorganic-phosphate (Pi) concentrations in blood plasma and serum were determined in lactating ruminants when P intake was changed abruptly from adequate, during a control period, to very low in a period of P depletion, and back to adequate during a period of P repletion. In each of three trials, four or three goats and, in one trial, four cows were used. In addition, the course of P concentration in the rumen fluid of three fistulated goats was studied. Pi concentrations in plasma or serum started to fall immediately with changing P intake from adequate to low, reaching a minimum plateau of less than 0.25 mM in three trials and 0.4 mM in one trial. Correspondingly, concentrations rose instantly with return of P intake to adequate, overshooting the range observed in goats during the control period and then returning to normal. P concentrations in particle-free rumen fluid declined from about 30 mM in the control period to 5.7 mM during P depletion and returned to 30 mM during P repletion, paralleling the respective course of Pi in blood plasma.

Hydrolyzed feather meal as feed component in diets for rainbow trout (Oncorhynchus mykiss) and effects of dietary protein/energy ratio on the efficiency of utilization of digestible energy and protein.

Two feeding trials were performed on rainbow trout of mean initial weights of 40 and 50 g and lasting for 12 and 14 weeks, respectively. In trial 1, diets contained per kg 300 g fish meal and varying proportions of gelatinized maize starch plus either casein or hydrolyzed feather meal. Dietary crude protein content varied from about 27 to 53%. In trial 2, all diets had about 45% crude protein. Fish meal (300 g/kg) was replaced in 3 steps by hydrolyzed feather meal either without or with supplementation of L- lysine.HCl and/or DL-methionine. In trial 1, efficiency of utilization of digestible energy (DE) rose from 38 to 50% when the ratio digestible crude protein (DCP)/DE was increased from about 11 to 17 g/MJ irrespective of the source of additional DCP, but did not further increase at higher ratios DCP/DE. Efficiency of utilization of DCP was about 50% as long as the ratio DCP/DE did not exceed 17 g/MJ. With progressing replacement of fish meal by hydrolyzed feather meal, efficiencies of utilization of DE as well as of DCP were reduced, the respective rates of reduction being about halved by supplementing lysine with no effect of supplementing methionine.