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Investigations with 15N'-labelled urea were carried out to find out the influence of the amount of fibre on the reflux of 15N' into the caecum to take part in the caecal metabolism. Two pelleted diets, containing 9.7% (group 1 with 23% oat hulls) and 2.2% (Group 2 without oat hulls) crude fibre, with urea with 60 atom% 15N-excess (15N) used as marker were given to three White New Zealand rabbits each group. Group 1 and 2 consumed 109 and 72 g fresh matter per rabbit and day, respectively. Daily 15N'-intake per rabbit was 307 mg in group 1 and 279 mg in group 2. Most of 15N' was eliminated directly via the urine. The daily faecal excretion in group 1 and 2 was 5.3 and 2.3 mg 15N', respectively. Only about 20 to 30% of 15N' and volatile fatty acids in the caecum and higher amounts of 15N' in muscles were found. The animals of this group consumed nearly the total amount of faeces by caecotrophy. Therefore 24 g of group 2 was still satisfying compared to 33 g live weight gain/rabbit and day of group 1. It is concluded that the animals of group 2 could compensate the low fibre level within a period of about 20 days by a more efficient utilization, the consumption of crude protein and starch being 18 and 12% lower than in group 1, respectively. Feed intake and health status were not evidently affected. The results are in contradiction to the common knowledge.

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.

Object of investigations was to estimate lysine efficiency from different lysine sources (lysinemonohydrochloride and lysinesulfate resp.) for rats, piglets and broiler chickens to reach a higher level of calculation of lysine supply. Lysine limiting diets were based on wheat, soybean meal and wheat gluten, supplemented with different levels of lysine sources under investigation. Balance trials (rat, piglet, chicken) and growth trails with analyses of body composition (chicken) were done to estimate N-balance resp. N-deposition. N-utilization model from Gebhardt (1966) and its further development for efficiency estimation of feed amino acids were used for data calculation. Results allow conclusion, that there are no differences in utilization of lysine from lysinemonohydrochloride and lysinesulfate. Limitations of efficiency resulting from differences in time course of absorption between protein bound and free lysine were not observed under ad lib. feeding conditions.

The investigations were carried out in order to develop foundations for a complex growth model including the effect of N-efficiency mechanism first of all for the rat. Therefore N-balance trials with rats of different live weights were made using diets of equal protein quality. The curve of the regressively calculated N-efficiency function courses relatively linear in its lower part, i.e. for low N-intakes. The protein quality value "A.b" was proved to be constant for all investigated live weight ranges. In similar trials with different protein qualities was also found a linear course for low N-intakes. The regressively estimated N-maintenance requirement (for N-Intake = 0) related to metabolic live weight (NMR/LWkg0.67) amounts to 180 mg/d. In addition endogenous N-excretions were determined in 15N tracer experiments on animals of different live weight fed graduated amounts of a quality constant protein. The NMR-values (sum of endogenous excretions from faeces and urea) depend on the level of N-intake, i.e. they can not be considered as constant. The endogenous faecal N-loss related to metabolic live weight is relatively constant indeed, whereas the amount of endogenous urea N-loss is dependent on the level of N-intake. Therefore calculations based on the N-efficiency curve, e.g. amino acid requirement dependent on performance and prediction of N-deposition respectively, should not be carried out on the basis of "N-retention" (N-balance + NMR) but only on the basis of N-balance.

The validity of residues from hydrolysis of soya bean meal for production of lysine was tested in a growth experiment with 2 groups of 25 cross breeding lambs as well as in a N-balance trial with 5 lambs. The animals in the growth experiment started with an average body weight of 25 kg. An industrially produced concentrate for lamb fattening was given to the animals of the control group. To the second group a straw-concentrate mixture was given, containing 30% straw, 52% barley, 5% soya bean meal, 5% dried beet pulp and 5% of hydrolysis residue. The mixture included 10.71 MJ ME resp. 5.51 MJ net-energy fat (cattle) and 166 g digestible crude protein per kg dry matter. The lambs of group 2 showed an 8% lower intake of DM, connected with a 26% intake of energy and 32% lower intake of DCP in comparison to the control group. The average daily body weight gain was 374 g for the control group and 241 g for group 2 respectively, the difference being statistically significant. The feed/gain ratio was in group 2 = 14% higher for energy and 6% higher for DCP than in the control group. The N-balance trial resulted in a N-retention of 25 percent of the N-intake. The results approved the possible use of 5% of the hydrolysis residue product for 2% crude protein in straw-concentrate mixtures for ruminants.

During the milk feeding period (ca. 55th day of life) and 2 weeks after the milk feeding period (ca. 80th day of life) the influence of a hay quota in the ration (on DM basis) of 6, 10, 14 and 18% in the milk feeding period and of 16, 23, 31 and 37% in the period after milk feeding was tested as to ruminal N metabolization with calves supplied with duodenal re-entrant cannulae. The increase of the hay quota in the ration for ruminating calves reduced as a tendency duodenal NAN passage, its bacterial N-quota, post-ruminal NAN digestibility and, due to a worse utilization of available N for bacterial N-synthesis, bacterial N-synthesis rate. The apparent fermentation of organic matter was, as a tendency, increased with the growing hay quota in the ration.

Four experiments with 270, 44, 432 and 66800 Leghorn hens were carried out to investigate the influence of various Mn additions to diets differed in mineral or Ca contents on egg shell quality. The addition of 300 mg Mn/kg diet improved significantly egg shell breaking strength by 4 N over one year. The supply of 50-500 mg Mn/kg diet for 10-24 weeks of the second half of laying year did not influence the egg shell quality. Addition of mineral mixture or Ca grit to layer rations with adequate or higher Mn levels did not influence egg shell strength. High mineral content in a low manganese diet increased number of cracks by 3%. Strength, weight and ash content of tibia were significantly reduced by feeding a low mineral level. Addition of 50-150 mg Mn per kg low mineral diet normalized partially tibia stability in young hens. It was concluded that supplied dietary Manganese influences calcification positively only in young hens. High levels of Ca did not influence the effects of Mn. 50 mg Mn per kg layers mixture have been considered as an essential supply.

Publications from Williams were the stimulation to study the relations between wool yield and cyst(e)ine concentration in blood plasma. Methodical experiments were carried out and the two methods used each provided clear results. At the same time the reversible binding of a part of the free cystine in the plasma with the plasma proteins and its effect on the analysis results might be considered. After an interpretation of the two methods their use is described taking into consideration the factors influencing the results of the analysis. It is concluded that the two methods are usable for the planned purpose.

In two digestibility and N-balance experiments the following solvent extracted meals were examined in a grain (barley and wheat in equal parts) or in a starch diet with four female pigs/group fitted with urethra catheters during the 5 days sampling period: 48% soyabean meal (SBM) (1), 24% conventional rapeseed meal (RSM) (2), 24 (3) or 48% (4) RSM from a newly bred low glucosinolate variety, groups 1 to 4 with grain, 48% low glucosinolate RSM (5) or 48% SBM (6) both with starch. In numeric order of the groups 88, 85, 86, 84, 79 and 89% N were digested. Pigs responded to the additional faecal N excretion from RSM diets by a lower urinary N excretion and thus they reached the N-balance of the animals fed on SBM. In numeric order of the groups 86, 79, 80, 73, 73 and 92% of the organic matter of the solvent extracted meals were digested. In comparison with SBM even 48% RSM in the feed significantly lowered the digestibility of organic matter. Using detergents the additional faecal organic matter excretion of RSM versus SBM could quantified as two third lignin. In the case of 24% RSM in the diet--i.e. 15% of the carbohydrates given--the carbohydrate digestibility is estimated with a high error, that an energetic feed value should not calculated. Investigating 48% SBM or RSM respectively in a grain diet the net energy content was 9.8 MJ (666 Energetic Feed Units, EFU pig) or 8.3 MJ (569 EFU pig)/kg dry matter (DM). Based on the starch diet, however, little relevant for estimation of normal pig diets, there were evaluated 10.6 MJ (720 EFU pig) for SBM and 8.3 MJ (567 EFU pig) net energy/kg DM for RSM.

Analytical possibilities for nitrate determination in milk on the base of photometric methods are discussed. An automated method, similar to Nijhuis u. a. (1979), is proposed using flow stream analyser ADM 300. Natrium nitrate (5 g and 10 g/kg live weight resp.) was given to two dairy cows after morning feeding on the 1st and on the 3rd day of experiment. The increase of nitrate content in the milk was very quick, maximal concentrations after 2 h were found as 5.6 mg/l (animal 1) and 3.2 mg nitrate-N/l (animal 2). But nitrate also disappeared relatively quickly, after 24 h there only values were observed corresponding to normal range of 1 mg/l.

Feed intake is regulated in a dialogue between the animal and the feed, which is influenced by numerous factors. The hypothalamus has a central integrative function. Furthermore, caudal brain areas (medulla oblongata, pons) are of importance because these areas are relays of peripheral signals and gustatory afferents. All peripheral informations are integrated by various neurotransmitters and neurohormones. The function of this neuronal system is not exactly known yet. Sensorial informations, mechano-, chemo- and osmoreceptors of the gastrointestinal tract and gastrointestinal hormones are discussed as influences of the periphery. The physiological satiety function of cholecystokinin is questionable in poultry. Hepatic chemoreceptors, which are activated by various metabolites, influence the amount of feed ingested. The feed choice appears to be regulated by the same mechanisms. Our knowledge about the translation of peripheral signals into choice behaviour by changes of neurotransmitter systems is limited.

In the experiment, 2 x 12 growing pigs received 19 or 6.7 mmol glucosinolates + aglucones/kg feed via conventional rapeseed meal (RSM) or RSM of a newly bred variety. These pigs and 24 littermates pair fed with a soya bean meal (SBM) diet were subdivided in groups of 4 animals each. Their diet contained either no supplementary iodine or an iodine supplementation of up to 1 mg/kg feed. In the RSM and SBM groups the lack of additional iodine lowered the serum T4 and T3 content below the detection limit and caused goitre with about 1 mg iodine in the total thyroid. The SBM diet with 0.0625 mg supplementary iodine/kg increased the serum T4 level and reversed the thyroid enlargement but not that of epithelial cells. The hypothyroidism (goitre and serum T4 level approximately 10 nmol/l) still existed in the case of this iodine dosage together with the RSM of the newly bred variety. A serum T4 level comparable to that of the animals fed SBM was only reached by supplementing the low glucosinolate diet with 0.25 mg iodine/kg feed. The iodine content of the thyroid, however, was reduced by 50 per cent. Though thyroid and epithelial cells were enlarged, this enlargement was not so obvious as in animals exposed to higher glucosinolate level. In spite of 1 mg supplementary iodine/kg feed, the feeding of the conventional RSM resulted in a lower serum T4 level a reduced thyroid iodine content and the enlargement of thyroid and that of epithelial cells. Compared to the high glucosinolate RSM, a significantly lower antithyroid effect of the low glucosinolate RSM was found in pigs with iodine supply. The degree of thyroid enlargement and the serum T4 level were the criteria.

Three experiments with five wether each were carried out in order to investigate the influence of various levels of flavomycin (0, 5 and 10 mg per animal and day) on apparent digestibility of artificially dried grass. A short time individual feeding experiment (42 days) with 9 bulls and a long term individual feeding experiment (225 days) with 52 heifers were conducted. Animals consumed 0 or 30 mg flavomycin per day. Parameters of rumen fermentation were investigated. Feed intake and weight gain were measured in the experiment with heifers. Flavomycin did not significantly influence the apparent digestibility of organic matter and crude nutrients as well as parameters of rumen fermentation. Flavomycin did not influence dry matter intake, but increased significantly weight gain (49 g per animal and day, 10.5%) and reduced feed and energy required per kg weight gain (10.6%) in heifers. The reasons of ergotropic effects of flavomycin are mostly unknown at present.

In a individual feeding experiment (348 days) 24 fattening bulls were given either a ration high in roughage (2.8 kg concentrate mixture, wheat straw ad libitum: group I) or high in concentrate (5.6 kg concentrate mixture, wheat straw ad libitum group II) supplemented with various levels of vitamin D3 (0, 250, 500, 1,000, 2,000, 4,000 and 8,000 IU per 100 kg body weight (bw) and day) and minerals as required. After 58, 101, 134, 172, 205, 277 and 340 days 25-OH-D3 plasma concentration was estimated. Fattening and slaughtering parameters were measured. The 25OH-D3 plasma concentration was significantly influenced by vitamin D3 supply, kind of ration and day of taking samples. 25-OH-D3 plasma concentration decreased below 5 ng per ml when vitamin D3 supply was less than or equal to 250 IU per 100 kg bw and day. The initial plasma levels were maintained when 500 IU vitamin D3 per 100 kg bw and day was given (6.6 ng per ml). Administration of greater than or equal to 1,000 IU per 100 kg bw and day increased 25OH-D3 plasma level (greater than 10 ng/ml). Plasma 25OH-D3 concentration was significant higher when bulls consumed diets rich in concentrate (10.6 and 18.2 ng/ml for I and II after 340th day). Differences in content of cell walls and crude fat of rations may be responsible for results. Daily weight gain of bulls amounted to 712 and 945 g when fed diets I or II. Dry matter intake and live weight gain were not significantly influenced by different vitamin D3 supply. Clinical symptoms of rachitis did not appear.

The influence of salinomycin (0, 15, 30 and 60 mg per animal and day) on apparent digestibility of artificially dried grass was investigated in four experiments with five wether each. Three long term individual feeding experiments (210 to 252 days) with 72 growing bulls were carried out. The influence of various salinomycin levels (100 to 300 mg per animal and day) were investigated on parameters of rumen fermentation as well as fattening and slaughtering results. Salinomycin decreased insignificantly (P greater than 0.05) the apparent digestibility of organic matter (71.0; 70.1; 68.7 and 68.4%) and crude carbohydrates (71.8; 70.3; 69.2 and 68.5% resp.). The digestibility of other nutrients was not influenced. Supplementation of salinomycin reduced molar concentration of acetate (49 to 115) and butyrate (22 to 82) and increased propionate (110 to 199 mmoles per mol) in rumen liquid. Dry matter intake of bulls declined (0.8%, 13.5 and 24.6; 4.7% of experiments 1 to 3) when salinomycin was added. Daily weight gain (6.5 and 1.0%) and feed efficiency (6.8 and 6.3%) of bulls supplemented with salinomycin were improved in experiments 1 and 3. Significant decrease of feed intake of bulls of experiment 2 affected decline of weight gain probably as consequence of high salinomycin levels. Slaughtering results (except experiment 2) and body composition of bulls were not significantly influenced by salinomycin. Under consideration of own results and some references 10 to 20 mg per kg dry matter or 50 to 150 mg salinomycin per fattening bull and day are recommended as optimal level.

The genetically caused intensity of growth from piglets (barrows) of four breeds and two crossbreeds was evaluated by estimation of maximum daily capacity per LW 0.67 kg of N-balance plus N-maintenance-requirement (A) on the basis of a total of 130 N balance measurings on 66 piglets in the live weight range between 10 and 20 kg. The estimation was realized by using the N utilization model by Gebhardt (1963) and of its further development. In comparison with Landrace (A = 2575 mg) the breeds Edelschwein (A = 3,242 mg) and Leicoma (A = 3,038 mg) had a higher A in the midst of the piglet period (9th and 10th week of life), but not so the breed Schwerfurter (A = 2,350 mg). The capacity of the following N balances during growing and fattening stages is not derivable from these values. The experimentally evaluated A of crossbreeds is in good agreement with the calculated A on the basis of the used races for breeding. The product A.b = 1.15 is characterizing the quality of the feed protein (a mixture of wheat and casein in the relation 2.2:1), independently of the live weight and also of the breed or the genotype of the pig.

Four digestion experiments with 5 wethers each (Feeding: artificially dried grass; 0, 15, 30 or 60 mg lasalocid per animal and day), two short time experiments (Exp. 1: 3 rumen fistulated sheep; feeding; artificially dried grass; 0, 15, 30 or 60 mg lasalocid per animal and day; exp. 2: 20 bulls; feeding; 2 kg concentrates per animal and day; wheat straw ad libitum; 0, 150 or 300 mg lasalocid per animal and day) and one individual feeding experiment (24 bulls per group; duration: 279 days, feeding: 2 kg concentrates per animal and day, corn silage and whole barley-grass silage ad libitum; 0 or 100/200 mg lasalocid per animal and day) were carried out in order to investigate the influence of the ionophore lasalocid on digestibility, figures of rumen fermentation as well as fattening and slaughtering results of bulls. Higher doses of lasalocid (30 and 60 mg per animal and day) decreased significantly digestibility of organic matter (1.8 and 2.8 units) and crude fibre (5.8 and 7.2 units). Relative acetate (22 to 120 mmoles per mol) and butyrate concentration (23 to 58 mmoles per mol) were decreased and molar propionate concentration of rumen liquid (25 to 154 mmoles per mol) was increased depending on level of lasalocid supplementation. Lasalocid did not significantly influence the dry matter intake; daily weight gain and slaughtering results were increased (4.4 and 6.1%), energy efficiency was improved (3.8%). Effects of lasalocid are similar to that of monensin. A dose of 20 to 30 mg lasalocid per kg dry matter is recommended.

Four digestion experiments with 5 wethers each (0, 15, 30 or 60 mg avoparcin per animal and day), three individual feeding experiments (28, 18 or 56 bulls per experiment; 0 and 150/200; 0, 250 and 500 or 0 and 200 mg avoparcin per animal and day in the experiments 1, 2 or 3) and two group feeding experiments (60 bulls and 161 heifers per experiment; salt lick stones without or with 2.5 g avoparcin per kg) were carried out in order to investigate the influence of avoparcin on apparent digestibility, figures of rumen fermentation, fattening and slaughtering results as well as protein, fat and energy retention. Avoparcin supplementation did not significantly influence the apparent digestibility of organic matter and crude nutrients. Concentration of acetate of rumen liquid was decreased (16 or 36) and that of propionate was increased (25 or 50 mmoles per mol) when 200 or 500 mg avoparcin per animal and day were added. Acetate:propionate ratio decreased from 4.2 to 3.5 and 3.1:1. Avoparcin did not influence feed intake, enhanced daily weight gain (37 to 174 g per animal and day) and improved feed efficiency (5 to 26%). Salt lick stones with avoparcin increased weight gain (58 and 96 g per animal and day). Slaughtering results and body composition of bulls were not influenced by avoparcin. Daily retention of protein, fat and energy was significantly increased (16 to 18%; P less than 0.05) when avoparcin was supplemented.

In a feeding experiment with 48 growing pigs 16% high glucosinolate rapeseed meal (HGRSM) (136 mumol glucosinolates + aglucones/kg dry matter, DM) or low glucosinolate (LG) RSM (48 mumol glucosinolates + aglucones/kg DM) in the feed were compared with 14% soya-bean meal (SBM) in each case. It were established 24 pairs of animals, which received the same quantity of the isonitrogenous but not isocaloric diets with SBM and the both RSM (pair fed). Four of the 2.12 animal pairs were not given supplementary I, four received 0.25 mg supplementary I/kg feed. Further four animals which were fed on LGRSM or HGRSM were provided with 0.0625 or 1 mg supplementary I/kg feed. In case of high glucosinolate intake (HGRSM) the lacking I supplementation decreased feed intake and growth and led to remarkable I deficiency symptoms from the fifth week onwards. The 2/3 lower glucosinolate dosage of the LGRSM diet also decreased performance and provoked I deficiency, however significantly later. The investigated I dosages (greater than 0.0625 mg/kg feed) did not effect the performance. In the experiment the eight animals which received LGRSM with supplementary I consumed 13% more feed than animals fed on HGRSM (P less than 0.05). The additional weight gain was 20% (P less than 0.05). Comparing the live weight gain of the SBM and RSM fed animals (pair fed) there was a significant increase of 9% versus the HGRSM groups and 5% versus the LGRSM groups.

Energetically differing rations which received ca. 45% of their crude protein from a supplement of soybean oil meal or urea were tested in a model experiment with adult wethers fitted with duodenal re-entrant cannulae or rumen cannulae resp. The N-equivalent exchange of soybean oil meal by urea in wethers resulted in a distinct increase of the NH3-N content of the rumen fluid, an increase of irreversible N losses and thus a worsening of the utilization of the available N for bacterial N-efficiency. A significant influence on duodenal NAN passage, on the apparent fermentation of the organic matter, on postruminal NAN digestibility and on the content of amino acid nitrogen as well as the amino acid composition of the duodenal NAN could not be detected. The increase of the energy level of the rations did not have a significant influence on the parameters of the ruminal N metabolism in the wethers. The studies with calves and adult wethers showed that a transposition of the parameters of ruminal N metabolism obtained to calves is not possible under the conditions given.

In a model experiment with calves supplied with duodenal re-entrant and rumen fistula resp. rations were tested that were energetically different (535 and 585 EFU cattle/kg DM) due to changing quotas of wheat starch and straw resp., dry matter intake being equal, and in which 45% of the crude protein came from soybean oil meal or urea resp. Due to the N-equivalent exchange of soybean oil meal by urea in rations for ruminating calves (130th day of life) the ammonia-N content in the rumen fluid, the quota of bacteria-N in the duodenal non-ammonia N (NAN) as well as the fermentation of crude plant protein in the ration were clearly increased. The iso-acid content in the rumen fluid and the utilization of the N available for bacteria N synthesis (N intake minus not degraded feed N in the duodenum) were reduced. An influence on duodenal NAN passage, on the apparent fermentation of the organic matter, on postruminal NAN digestibility and on the content of amino acid nitrogen as well as the amino acid composition of duodenal NAN could not be proved. A ca. 20% higher energy intake by ruminating calves did not have a clear influence on other parameters, with the exception of the reduction of the molar quota of acetic acid in favour of the quota of propionic acid in the rumen fluid.

Eight feeding experiments (4 on pasture and indoors each) with 401 growing cattle were carried out in order to measure the influence of a monensin device on daily weight gain. The monensin device effected on the average 7 g (1.4%) and 37 g (4.3%) higher daily weight gain on pasture and indoors resp. (P greater than 0.05). The weight gain of animals varied between 92.5 and 112.5% compared with the unsupplemented groups. The monensin device caused a higher weight gain of easier cattle than of heavier ones (greater than 300 kg body weight). The device has had no significant effect on figures of rumen fermentation. Probably the monensin level delivered from the device (100 +/- 50 mg per animal and day) is to low for heavier cattle.

Five groups of five colostomized laying hens each received 0 g, 15 g, 30 g, 45 g and 60 g peas of the variety Grapis per animal and day with Triticum rations. The apparent digestibility of the crude nutrients of the rations and the peas was determined, ascertained according to the difference method in dependence on their quotas in the rations. The digestibility of the N-free extracts of the peas increases by 3 digestion units each under the influence of the increasing intake of peas, so that the digestibility of the organic matter of the peas increases with the growing quota. On an average of the 20 individual values the following digestion values for the pea variety Grapis are indicated: organic matter 66.9%, crude protein 78.5%, crude fat 48.7%, N-free extracts 70.3%. Energy concentration amounts to 572 EFU-hen/kg dry matter.

The requirement of the cat in respect to protein, energy, vitamins and minerals are presented. The special requirements of this carnivore appear to be due to the loss or charge of certain metabolic processes which are normally present in species such as the dog.

In six experiments with laying hybrids the influence of a varied nutritive beta-carotene and vitamin A supply during rearing on the performance in the laying period was tested. Basal rations poor in carotene without vitamin A supplementation in the rearing period diminished feed intake and laying performance in the laying period, retarded the beginning of intensive laying and increased feed expenditure per 100 g egg if the feed for laying hens contained less than 5000 IU vitamin A per kg. Relations between varied vitamin A supply and the performance parameters of the laying performance could not be proved if chick and young hen feed with maize even without vitamin A supplement or if rearing feed with approximately 2500 IU vitamin A or laying hen feed greater than 5000 IU vitamin A supply were used.

Five experiments with 18 to 36 male calves each of the black and white dairy cattle breed (age: 14-21 days, initial live weight: approximately 45 kg per animal) were carried out in order to investigate the influence of various vitamin A supply (0-80,000 IU per 100 kg LW and day) on dry matter intake and weight gain as well as the vitamin A status of liver and blood plasma over 84 days. The calves consumed a diet free of carotene and vitamin A consisting of milk replacer, concentrate and chopped wheat straw. The calves were fed in three experiments for a longer time in order to observe the further vitamin A depletion. Nine animals consumed an unsupplemented ration, nine other one got 10,000 IU vitamin A per 100 kg LW and day. Biopsies of liver and plasma samples were taken from 4 animals per group every four weeks. The various vitamin A supplementation did not significantly influence the dry matter intake (Mean: 1.67; 1.48 to 1.80 kg DM per animal and day) and the weight gain of calves (Mean: 702, 599 to 770 g per animal and day). First vitamin A deficiency symptoms (reduced feed intake, decreased weight gain, diarrhoea etc.) were observed in animals of unsupplemented group after 100 days of experiments. After 84 days the vitamin A concentration of liver of animals of unsupplemented groups decreased to 1.3-32.2% compared with the begin of experiments (60.6-155.7 mumol/kg fresh matter). Up to 51% of initial concentration were found when 10,000 IU vitamin A per 100 kg LW and day were fed. About 25,000 IU vitamin A per 100 kg LW and day were required in order to keep the initial level of vitamin A concentration of liver. The plasma vitamin A concentration is unsuitable for estimation of vitamin A status of calves. The concentration of vitamin A of liver and plasma amounted to 114 mumol per kg and 0.25 mumol per litre at the begin of experiments. The vitamin A concentration of liver of unsupplemented group decreased to 20 mumol per kg, that of plasma increased to 0.28 mumol per 1 at the end. A strong vitamin A deficiency (liver concentration: less than 10 mumol/kg) may cause a decrease of vitamin A concentration of blood.

Three long time individual feeding experiments (greater than 258 days) with 48 beef cattle each (dairy breed and beef breed, 50% each) were carried out in order to measure the influence of various vitamin A supply (0, 2,500, 5,000 and 10,000 IU vitamin A per 100 kg body weight and day) on fattening and slaughtering performance, vitamin A concentration of liver and serum as well as carotene concentration of serum. The bulls consumed corn silage (experiments 1 and 2; 9.4 and 18.3 mg carotene per kg dry matter) or NaOH-treated and pelleted straw (experiment 3; no carotene). The roughages were supplemented with 2 (exp. 1 and 2) and 3 kg (exp. 3) concentrate per day. The vitamin A supply of corn silage diet did not significantly influence the dry matter intake (exp. 1: means: 6.95; 6.91 to 7.05; exp. 2: means: 6.54; 6.53 to 6.54 kg dry matter per animal and day) and the daily weight gain of bulls (exp. 1: means: 1076; 1028 to 1157; exp. 2: means: 1058; 1041 to 1057 g per animal). The bulls consumed 8.87 kg dry matter per day, the daily weight gain amounted to 1030 g per animal and day in experiment 3. The bulls of unsupplemented group reduced feed intake and weight gain after 150 days, an additional vitamin A supply was necessary. At the end of experiments 1 and 2 the liver vitamin A concentration of unsupplemented groups amounted to 38.8 and 65.9 mumol/kg, it increased after vitamin A supply (up to 153.4 mumol/kg). Feeding of pelleted straw effected a liver vitamin A concentration lower than 10 mumol/kg except the group supplemented with 10,000 IU vitamin A per 100 kg body weight and day (35.7 mumol per kg fresh matter of liver). The vitamin A concentration of blood is unsuitable for evaluation of vitamin A status of cattle. The carotene content of feeds and level of vitamin A supply determined the carotene concentration of blood. Recommendations for a suitable vitamin A supply of ration of growing cattle were given depending on body weight and type of diet.

The Cd status of animals is best reflected by kidneys and much worse by liver and hair. Breed (heavy- and warm-blooded horses) only took an insignificant effect on the Cd content of kidneys and liver. On the average, however, warm-blooded horses stored more Cd than heavy ones. Geldings from Cd-exposed living areas accumulated insignificantly more Cd in liver, kidneys and hair than mares. The influence of age on the Cd content of kidneys and liver of Cd-exposed horses was significant. The Cd exposure of a living area was very well reflected by kidneys and liver. On the average, horses from two areas with nonferrous metal smelting stored 1000 mg Cd/kg kidney dry matter and 100 to 200 mg Cd/kg liver dry matter. The highest Cd concentration of the kidneys of horses amounted to 2.6 and 2.3 g/kg dry matter, resp.

Four colostomized laying hens per group were given a ration of barley and soya bean oil meal (SBM) with 12.5, 25.0 and 37.5% SBM resp. The crude protein intakes were 14.0, 17.7 and 21.4 g per animal and day. The lysine intake raised from 681 mg (group 1) to 1275 mg (group 3) per animal and day. The digestibility of dry matter and of the N-free extracts of the ration decreased with the rising SBM portion in the ration. The digestibility of crude protein remained constant. The investigated amino acids (Lys, His, Arg, Cys, Met) were higher digested in the 37.5% SBM ration than in the 12.5% SBM ration. The following digestibility values for SBM were found by means of the difference method: Dry matter 52.5%, crude protein 83.1%, crude fat 51.7%, crude fibre 5.5%, N-free extracts 50.6%. The level of the SBM did not influence the digestibility of the crude nutrients. The apparent digestibility of lysine from SBM depended on the level of intake and was found to be 82.3, 83.4 and 89.0%, resp. There were no differences in the digestibility of other amino acids.

The metabolization of the straw N and the influence of the straw on N excretion in urine were studied in 2 experiments with colostomized broiler hens and with 15N labelled wheat straw as well as 15N labelled wheat. In experiment 1 the test animals divided up into 4 groups received 0 g, 20 g, 30 g and 40 g straw meal per animal and day in addition to 120 g mixed feed. The daily 15N-excess (15N') intake from the straw was 18.4 mg, 27.5 mg and 36.7 mg. The amount of 15N' daily consumed with the labelled wheat in experiment 2 was 119.7 mg. 40 g straw meal resulted in a significantly increased amount of urine (p less than 0.05). The amounts of urine N and uric acid N were only increased as a tendency. On average the productive N decreased as a consequence of the straw meal supplement from 1070 mg/animal and day (control) to 764 mg/animal and day after 40 g straw meal supplement. The productive 15N' of the labelled wheat was not influenced by the straw meal supplement. The productive 15N' of the straw increased from 3.8 mg/animal and day (20 g straw) to 13.4 mg/animal and day (40 g straw). In contrast to 15N wheat, straw as a 15N source resulted in a lower labelling of uric acid N in comparison with urine N. It can be assumed that the changed metabolization of the straw N is influenced by microbial processes in the intestines.

Even with a high vitamin E offer, Se deficiency (less than 38 micrograms/kg DM of the ration) led to a 33% lower conception rate (P less than 0.05) in goats and to a greater than 50% lower number of kids on the 91st day of life. The Se deficiency reduced the milk production significantly by 23% during the first 56 days of lactation, the milk fat production by 11% and the milk protein production by 12%.

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.

In an N balance experiment with male crossbreeding lambs at an age of 3 ... 4 months four different rations were given differing in energy concentration (high greater than 700 EFU cattle/kg DM and low less than 650 EFU cattle/kg DM) and in the energy source (sugar, starch or crude fibre) with crude protein intake being almost equal. The rations contained 2% urea. Microbial protein synthesis in the rumen was assessed according to ROTH and KIRCHGESSNER (1978) (1), RYS et al. (1975) (2) and BICKEL-BAUMANN and LANDIS (1986) (3) on the basis of allantoin excretion in urine. The highest ruminal protein synthesis quotas were 868 ... 921 mg protein N per kg LW0.75 in (2). In (3) 723 ... 766 mg protein N/kg LW0.75 were synthesized. From the 15N labelling of the supplemented urea and the excreted allantoin it could be calculated that 26 ... 40% of the microbial protein resulted from the urea-N of the ration. Despite a high crude protein content of the ration of between 16 and 17% in the DM and a relation of NPN: pure protein of 0.95 the utilization of the NPN in the ration was relatively high but slightly lower than the utilization of pure protein. The variants with higher energy concentration showed as a tendency higher allantoin excretion in spite of slightly lower dry matter intake and a slightly higher NPN utilization than the variants with lower energy concentration.

The average passage time, the rumen fluid volume and the digestibility of the organic matter were determined in addition to 3 individual feeding experiments with fertility oriented crossbreed ewes, which received pelleted straw-concentrate mixtures. The average passage time of the feed particles through the digestive tract is shorter in pregnant animals than in lactating ones. It is longest in non-pregnant sheep. High quotas of straw and coarse particles prolong the passage time, increasing feed intake and supplements of long straw shorten it. The volume of rumen fluid is lower in ewes fed ad libitum in the stage of late pregnancy and after lactation than during lactation. The rumen fluid volume is also lower in restrictively fed animals during the stage of late pregnancy than during lactation. In animals in the stage of late pregnancy it correlates negatively with the weight of the litter. On an average of all experiments at maintenance level the digestibility of the organic matter in ewes in the 4th month of pregnancy gravidity amounted to 56.6%, in the 2nd month of lactation to 59.8% and in wethers to 59.5% Due to an increase of energy intake from maintenance to 2. maintenance digestibility of the straw-concentrate mixture with 40% straw decreased by 5.5 units and of that with 60% straw by 17.8 units in the period before delivery. Pregnancy in the 4th month resulted in a digestion depression of between 3.0 and 5.8 units.

With the help of an N utilization model by Gebhardt (1963) and its further development the threonine efficiency coefficients (kThr) of wheat, barley, maize, rye and peanut oil meal of different charges with a supply of L-lysine monohydrochloride, DL-methionine and DL-tryptophan was ascertained with a total of 59 female pigs of the local breed (35-45 kg live weight) by means of an N balance method. The variation range of kThr was between 0.61 and 0.87 based on a threonine effectivity of wheat gluten with lysine as standard. The derived threonine requirement for 100 g daily protein retention with a live weight of 40 kg was ascertained as 6.9 g (kThr = 1) and 9.6 kg (kThr = 0.71 as mean values of the protein sources studied). The proof of threonine limitation in the protein sources was provided by the supplementation of DL threonine.

The digestibility of the crude nutrients of 6 rations on the basis of oat, hay and wheat straw (in one case a straw-concentrate mixture as sole feed) was compared at a nutrition level of 1.0 and 1.3 resp. with adult geldings of the species "Noble Crossbreed", adult pony geldings and wethers The energy concentration of the rations varied between 424 and 585 EFUcattle/kg DM, the crude fibre content between 17 and 25% of the DM. In the studied field, a good agreement between horse and pony could be ascertained as to the digestibility of the organic matter and NFE. There are partly considerable differences between the apparent digestibility of crude protein and crude fibre. The differences in the digestibility of crude fibre between horse and sheep increase with a growing crude fibre content. The differences of the apparent digestibility between horse and pony on the one hand and sheep on the other were highly significant in all cases.

3 colostomized laying hybrids received 1% 15N labelled urea with 96.06 atom-% 15N excess (15N') with a commercial ration over a period of 6 days. After the application of the same ration with unlabelled urea on the following 2 days the animals were butchered. In the muscles of the breast, the leg and the heart, the labelling of total nitrogen and the incorporation of urea 15N' into 15 amino acids of the 3 different kinds of muscles were ascertained. On average, significant differences could be ascertained between the atom-% 15N of the muscles of the skeleton and those of the heart. The 15N' of the breast and leg muscles was 0.25 and 0.34 atom-% resp.; that of the cardial proteins 0.71 atom-% 15N'. The incorporation of urea 15N into the basic amino acids is low and varies both between the kinds of muscles and between the amino acids. On average the highest level of labelling was found among the essential amino acids valine, isoleucine and leucine; the average atom-% 15N' for the muscles of the breast is 0.13, of the leg 0.17, and of the heart 0.27; the 15N' quota of branched chain amino acids in the total 15N' of the respective muscle is accordingly 6.0%, 5.0% and 4.5%. The non-essential amino acids, particularly glutamic acid, are more highly labelled in the muscles than the essential ones. A 15N' for glutamic acid of 0.24 atom-% in the breast muscles, of 0.27 atom-% in those of the legs and of 0.64 atom-% in the heart muscle could be detected. The average quota of the 15N' of these acid amino acids in the 15N' for breast, leg and heart muscles is 7.4, 6.2 and 6.7 resp. The quota of the 15N' in the 6 non-essential amino acids in the total 15N' in all 3 kinds of muscles is approximately two thirds and in the 9 essential ones one third of the total 15N'. Although the results show that there is a certain incorporation of 15N' from urea into the amino acids of the muscle proteins, their contribution to meeting the demands is to be considered irrelevant.

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.

Over 4 days 12 colostomized laying hens received, together with the ration, 36 g wheat with 14.37 atom-% 15N excess (15N'), The basic amino acids were nearly equally labelled. Three animals each were butchered after 12 h, 36 h, 60 h, and 108 h after the last 15N' application. Emission spectrometric determination of 15N' in the liver and in the amino acids was carried out. In addition, atom-% 15N' was determined in the free amino acids and the peptides. The labelling in the liver 12 h after the last 15N' application amounted to 1.75 atom-% 15N' and decreased after 108 h to 0.81 atom-% 15N'. The average TCA precipitable 15N' quota in the total 15N' amounted to 81.4% and was nearly identical at all measuring times. The arginine 15N' amount in the liver was twice as high as that of lysine 15N'. In dependence on the period of time after the last 15N' application the decrease in the labelling of the free arginine is considerable in comparison to free lysine. At the first measuring time (12 h) it was 1.69 atom-% 15N' and at the last one (108 h) 0.57 atom-% 15N'. Based on the results of 15N' labelling of the peptides in the liver further, more detailed series of experiments for studies of the peptide metabolism in the liver should be carried out.

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.

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.

Lambs of an age of 2 or 4 months and of an average live weight of 14.7 and 27.4 kg resp. received rations consisting of 44% cereals, 46% dried sugar beet pulp, 6% wheat starch, 2% urea and 2% mineral-vitamin mixture. The crude protein content was 17.1 and 15.9% resp. in the dry matter, that of native crude protein 10.6 and 9.4% resp. During a 6-day N balance period 8 and 16 g 15N urea resp. with a 15N excess (15N') of 9.26 and 9.40 atom-% were fed orally instead of commercial feeding urea. There were no significant differences between the two age groups with regard to the digestibility of the organic matter and the crude nutrients. The average N balance of 372 +/- 85 mg/kg LW 0.75/day were in the intermediate range of N retention capacity and accounted for 26 +/- 5% of the consumed N. N retention in per cent. was slightly lower in younger lambs. Projections of urea utilization in a quasi stationary state resulted in an efficiency of the utilization of 33 +/- 4%. The dismembering of the lambs at the end of the main period showed between 0.02 and 0.22 atom-% 15N' in the total N, TCA precipitable N and amino acid N of the meat. At between 0.24 and 0.38 atom-% 15N' they were highest in the heart and jaw muscles. The quota of 15N' amounts found in the total N of the meat were 10.6 +/- 3% of the 15N-intake and 20.1 +/- 5.1% of the 15N' amount remaining in the body. The bones contained 7.7 +/- 1.7% and the fleece 7.9 +/- 3.1% of the 15N'-intake. Generally seen, the total N and urea utilization was slightly lower in younger lambs than in older ones.

For studying the incorporation of the 15N labelled urea into individual organs and tissues 3 colostomized laying hens were butchered after they had received 1% urea (96.06 atom-% 15N excess) with a high quality ration over a period of six days and after receiving conventional urea for another two days. Nitrogen and atom-% 15N excess (15N') were determined in the bones, the feathers and the remaining body (skin, lungs and windpipe, head with comb and wattle, lower leg without bones and with skin, pancreas and fatty tissue). In the remaining body the atom-% 15N' was determined in 15 amino acids. The labelling in the remaining body and the bones was approximately the same and averaged 0.37 atom-% 15N'. A significantly lower relative frequency could be detected in the feathers. The lysine of the remaining body contained only 0.04 atom-% 15N', tyrosine 0.06, histidine and arginine 0.07. The phenylalanine and proline molecules were labelled with 0.11 atom-% 15N'. Most 15N' was incorporated in serine and glutamic acid with over 0.30 atom-%. In the six non-essential amino acids out of the 15 amino acids studied, 48.6 of the non isotopic nitrogen of the total N of the remaining body and 70.7% of the isotopic nitrogen of total 15N' could be detected. Consequently the urea-N is mainly used for the synthesis of the non-essential amino acids, with its utilization being very low.

The nylon-bag method was applied for determination of the rumen degradation of dry matter and nitrogen of 15N-labelled wheat straw. For the experiment 4 wethers fitted with a rumen cannula were used. The bags containing 15N straw were introduced into the rumen and withdrawn 3, 6 or 12 h after incubation. In a second experiment the apparent 15N-digestibility of the same straw was determined in wether and pony. The dry matter disappearance varied between 6 and 23%. For 15N-labelled straw the disappearance of 15N was higher than that of total N. 12 h after incubation 71% of 15N and only 25% of total N were disappeared. It was calculated that after incubation rumen microbial-N in the nylon bag increased from 31% (3 h) to 45% (6 h) and 61% (12 h) resp. The apparent 15N digestibility amounted 53 +/- 2% for wethers and 51 +/- 2% for ponies.

In a multi-generation trial with 120 or 96 hens of the breed White Leghorn per group the effect of diets containing 7.5% or 15.0% of methanol-grown dried bacterial cells was examined. The hens were kept in conventional three-stage battery. In two of the three experiments the feed intake was decreased if it was used methanol-grown bacterial cells as a protein source. The period of intensive laying (50% egg production) started later and the egg production has been decreased by using the bacterial cells. For the traits egg weight and mortality no relation to the nutrition could be found. The feeding of methanol-grown bacterial cells showed in two incubatory trials no negative effects on reproductive ability of the hens. The cock's sperm quality was not influenced in two experiments. In one trial the sperm volume was reduced and the sperm concentration was raised if diets contained methanol-grown dried bacterial cells. Indications of toxic influences of the methanol-grown bacterial cells were not found.

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.

A total of 90 lambs (fattening hybrids of either sex of three different genetic constructions and male merino meat sheep) were butchered at the beginning (9...16 kg live weight) or at the end (29...33 kg live weight) of a growth experiment. Total body and the meat of carcass, cutlet and loin were analysed. Significant differences between the genotypes could only proved in the crude ash content. The female animals showed a significantly higher content of fat, dry matter and energy as well as a significantly lower content of crude ash--at the end of the experiment also of protein--in the total body than the male animals. The content of nutrients and energy in the total body could be much more precisely derived regressively from the corresponding content values in the meat of the carcass than from the values of cutlet and loin.

The purpose of the investigations was to prove a method, developed for monogastric mammalians, based on a 3-compartment-model and assuming a proportional growth of the pools of total N, whether it is applicable to growing poultry. The tracer, 15N-L-lysine, was given quasi-continuously for four days. In this time and in the following period of five days without tracer intake, the 15N-excretion in the urine was measured. The average of the live weight of the broiler cockerels was 1724 g. The animals were obliged to be colostomized to sample the urine. Using the fluxes of lysine, the calculation of the whole body protein synthesis rate yields 64.1 g/d. The protein degradation rate yields 54.4 g/d. The adequate values of the fractional rates of protein synthesis and -degradation for the whole body (without feathers) were 23.3% respectively 19.8%. By this it is clearly shown, that the applied method gives real dates of the parameters of the N-metabolism for growing broilers, which are in the range of values for muscle proteins and proteins of the whole body of growing poultry, published by other authors.

Male calves between 15 and 26 days old and with a live weight between 45 and 46 kg received dried skim milk dissolved in water plus fat concentration from lard--suet mixtures made with a synthetic emulsifier of the type ethoxylated partial ester with and without soybean lecithin supplement. One group received bone fat with an emulsifier as sole fat component. In the course of 9 experiment weeks the calves of the lard--suet group without lecithin reached an average daily weight gain of 710 g, which was not significantly better than the gains of 689 g of the lard--suet group with lecithin and of 674 g of the bone fat group. The calves of the lard--suet group with lecithin did not digest the feed fat significantly better than the calves in the other two groups. The quota of fatty acids in the feed distinctly influenced the composition of the fatty acids in the intestines, the kidneys and the hypodermis. With the example of suet the general relationship between the fatty acid patterns of the feed and body fats are recognizable, with the fatty acids C 16:0, C 18:2 and C 18:3 having a lower and C 16:1, C 18:0 and C 18:1 having a higher quota in the suet than in the feed fat. Due to the application of high amounts of bone fat, vegetable oil or sea animal fat there are deviations from this rule. There is a higher quota of linolenic acid in the suet of the calves than in butter fat but a lower quota than in foreign fat.

Retention in the animal body was studied in a growth experiment with lambs of various genetic constructions (3 different fattening hybrids of both sexes and male merino meat sheep). The result of the control butchering method was for female animals a significantly higher crude fat, dry matter and energy content as well as lower crude protein content in the weight gain than for the male animals, whereas there were no significant differences between the various genotypes. The daily crude protein retention was higher in the male animals as in the female lambs. The male fattening hybrids were superior to the merino meat sheep with regard to daily N retention and the productive protein value. Concerning energy maintenance requirement, there were no significant differences between the genotypes or the sexes either. The N balance method resulted in similar statements on N retention as the control butchering method did, it produced, however, higher absolute values and a higher standard deviation. Conclusions for the standardization of the requirement and for the methodology of the experiments are drawn.