Higher Digestibility Values Research Articles

Subunit, amino acid composition and in vitro digestibility of protein isolates from Chinese kabuli and desi chickpea (Cicer arietinum L.) cultivars

The subunit, amino acid composition and in vitro digestibility of the two protein isolates (GCPI and ZCPI) from one kabuli and one desi chickpea cultivars, grown extensively in Xinjiang Autonomous Region of China, were investigated and compared with those of soy protein isolate (SPI). SDS–PAGE showed that GCPI and ZCPI had almost the same band components under the reduced and unreduced conditions, with only minor difference in relative quantity for some bands, but different from that of SPI. The sulphur-containing amino acids were the first limiting amino acids for all three protein isolates of GCPI (2.11 g/100 g), ZCPI (2.20 g/100 g) and SPI (1.99 g/100 g). Amino acid score of the three protein isolates could reach the FAO/WHO requirement (1990) for the essential amino acids for preschool children. The order of in vitro digestibility was GCPI (87.47%) > ZCPI (80.82%) > SPI (71.04%). Our results indicated that, compared with soybean protein isolate, Chinese kabuli and desi chickpea protein isolates had higher digestibility value, and chickpea protein, especially for kabuli protein, could be utilized as a good source of protein for human nutrition.

Comparative digestibility of amino acids of maize, sorghum, finger millet and pearl millet in cockerels and Japanese quails

1. The objective of the present study was to determine the apparent digestibilities of amino acids of maize, low tannin sorghum, pearl millet and finger millet in adult cockerels and Japanese quails. 2. Adult White Leghorn cockerels (25 weeks of age) and adult Japanese quails (15 weeks of age) were used to determine the apparent digestibilities of amino acids in cereal grains. 3. The digestibilities of amino acids in sorghum determined with quails were similar to cockerels, with the exception of histidine, which was significantly lower in quails. 4. In finger millet, the digestibilities of methionine and leucine were significantly higher, while that of histidine and cystine were significantly lower in adult quails than in adult cockerels. 5. The digestibilities of pearl millet amino acids were similar in quails and cockerels, except for that of histidine, which was significantly lower in quails. 6. Almost all the amino acids in maize, except histidine, had significantly higher digestibility values in quails than in cockerels. Histidine digestibility of all the 4 cereal grains was significantly lower in quails than in cockerels. 7. The amino acid digestibility values for certain cereal grains determined with cockerels do not support their use in formulating practical quail diets. The amino acid digestibility values of maize were underestimated by using cockerels while that of finger millet was overestimated.

Apparent digestibilities of common feedstuffs for bluegillLepomis macrochirusand largemouth bassMicropterus salmoidesusing individual test ingredients

Apparent digestibility of dry matter and energy, and availability of amino acids from blood meal (BM), fish meal (FM), meat and bone meal (MBM), poultry by-product meal (PBM), soybean meal (SBM), corn, wheat and yellow grease (YG) were determined for bluegill Lepomis macrochirus (mean weight, 57 g), and likewise, but not for BM or wheat, for largemouth bass Micropterus salmoides (mean weight, 30 g). To avoid nutrient interaction from a reference diet, diets containing 98.5% (985 g kg−1) of test ingredients were used, except for semi-solid, YG which was mixed with corn to permit pelletization. Faeces were collected by a siphoning method. Apparent dry matter digestibility values ranged from 50% (corn) to 87% (BM) for bluegill and from 53% (MBM) to 76% (PBM) for largemouth bass. Apparent energy digestibility values ranged from 53% (corn) to 92% (BM) for bluegill and from 63% (MBM) to 93% (YG) for largemouth bass. Apparent digestibility of most amino acids exceeded 90% for evaluated protein sources, except for MBM which showed slightly lower values (80–90%) for both fishes. Isoleucine digestibility from BM was relatively low (82%) for bluegill. High digestibility values for SBM, PBM and BM, indicate good potential for replacing FM in diets for both fishes.

APPARENT DIGESTIBILITY OF SELECTED FEED INGREDIENTS IN DIETS FOR MUD CRAB (Scylla paramamosain)

Cultured mud crabs (Scylla spp.) are commonly fed with ‘trash’ fish. Insufficient supply, high cost and variable quality of ‘trash’ fish has lead to a need to develop costeffective and environmentally friendly formulated diets. This study was conducted to determine quality of selected feed ingredients as protein sources in mud crab diets based on their nutrient composition and digestibility coefficients for dry matter (ADMD), crude protein, lipid and energy. The digestibility coefficients for ADMD ranged from 82.46% to 89.20%. Animal-based feedstuffs such as shrimp head, tiny shrimp and squid liver meal had higher ADMD values than fish meal. Of the plant-based feedstuffs, soy bean meal had the highest ADMD values (89.20%) and corn gluten had the lowest (82.46%). Corn gluten had the lowest protein digestibility (78.81%) and soy bean meal had the highest (96.05%). The lowest energy digestibility (71.13%) was obtained in corn gluten meal. Soy bean meal had a higher energy digestibility value (98.48%) than fish meal (85.95%). All animal meal sources had similar energy digestibility values (85.86%—92.09%).

Genetic variations of cell wall digestibility related traits in floral stems of Arabidopsis thaliana accessions as a basis for the improvement of the feeding value in maize and forage plants

Floral stems of Arabidopsis thaliana accessions were used as a model system relative to forage plant stems in genetic variation studies of lignin content and cell wall digestibility related traits. Successive investigations were developed in a core collection of 24 Arabidopsis accessions and in a larger collection of 280 accessions. Significant genetic variation for lignin content in the cell wall, and for the two in vitro cell wall digestibility investigated traits, were found both in the core collection and in the large collection. Genotype x environment interactions, investigated in the core collection, were significant with a few genotypes contributing greatly to interactions, based on ecovalence value estimates. In the core collection, genotypes 42AV, 224AV, and 8AV had low cell wall digestibility values, whatever be the environmental conditions. Genotype 157AV, observed only in one environment, also appeared to have a low cell wall digestibility. Conversely, genotypes 236AV, 162AV, 70AV, 101AV, 83AV had high cell wall digestibility values, genotype 83AV having a slightly greater instability across differing environments than others. The well-known accession Col-0 (186AV) appeared with a medium level of cell wall digestibility and a weak to medium level of interaction between environments. The ranges of variation in cell wall digestibility traits were higher in the large collection than in the core collection of 24 accessions, these results needing confirmation due to the lower number of replicates. Accessions 295AV, 148AV, and 309AV could be models for low stem cell wall digestibility values, with variable lignin content. Similarly, accessions 83AV and 162AV, already identified from the study of the core collection, and five accessions (6AV, 20AV, 91AV, 114AV, and 223AV) could be models for high stem cell wall digestibility values. The large variations observed between Arabidopsis accessions for both lignin content and cell wall digestibility in floral stems have strengthened the use this species as a powerful tool for discovering genes involved in cell wall biosynthesis and lignification of dicotyledons forage plants. Investigations of this kind might also be applicable to monocotyledons forage plants due to the basic similarity of the genes involved in the lignin pathway of Angiosperms and the partial homology of the cell wall composition and organization of the mature vascular system in grasses and Arabidopsis.

Production, survival and nutritive value of the perennial legumes Dorycnium hirsutum and D. rectum subjected to different cutting heights

Abstract Dorycnium hirsutum and D. rectum are perennial legumes which may have potential for use as pastures for the control of groundwater recharge in southern Australia. Little is known about the quality of the forage of Dorycnium species for grazing livestock or how these species respond to cutting. The effect of cutting height on plant survival, production of dry matter (DM), the proportion of leaf, edible stem (approximately <5 mm diameter) and woody stem in the DM and the nutritive value of the edible components was investigated. Biomass above five cutting‐height treatments (uncut, ground level, 5–8 cm, 10–15 cm and 15–30 cm above ground level) was removed at 8‐week intervals from plots of D. hirsutum and D. rectum from September 2002 to July 2003. In both species, plants subjected to lower cutting height treatments produced less DM above the height of the cut than those cut at higher heights. DM production declined over time in all treatments. Plants cut to ground level failed to regrow after the second harvest in D. hirsutum and the fourth harvest in D. rectum. Thus, these Dorycnium species were susceptible to high severity defoliations at 8‐week intervals. Negligible inedible woody stem was present in regrowth of both species after 8 weeks but D. hirsutum regrowth had a higher proportion of leaf (0·72) than D. rectum (0·56). Plants left uncut accumulated a large proportion of inedible woody stem in the DM (0·69 in both species) by July 2003, particularly at the base of the plant. Edible DM from regrowth of D. hirsutum and D. rectum had crude protein (CP) concentrations of 120 and 150 g kg−1 DM; dry matter digestibility (DMD) values of 0·45 and 0·58; organic matter digestibility (OMD) values of 0·50 and 0·64; neutral‐detergent fibre (NDF) concentrations of 370 and 290 g kg−1 DM; and acid‐detergent fibre (ADF) concentrations of 260 and 210 g kg−1 DM, respectively. Medicago sativa, grown under similar conditions, had higher digestibility values (0·63 DMD and 0·66 OMD) and similar CP concentrations to D. rectum (140 g kg−1 DM), but higher concentrations of NDF and ADF (410 and 290 g kg−1 DM). Leaf material from both Dorycnium species had a higher nutritive value than edible stems, with DMD and OMD values of leaf of D. rectum being 0·68 and 0·74 respectively. Uncut plants had a much lower nutritive value of edible DM than the regrowth from cut treatments; older material was also of a lower nutritive value. The relatively low nutritive value of even the young regrowth of Dorycnium species suggests that forage quality is a major limitation to its use. Forage of Dorycnium species could be used during periods when other sources of forage are in short supply but infrequent grazing it is likely to produce forage of a low nutritive value.

Effect of free-choice feeding on the performance and ileal digestibility of nutrients in broilers

An experiment was conducted to study ileal digestibility of nutrients and to verify the ability of broilers to select feed in order to meet their requirements for protein and energy. The treatments consisted of six diets: R+S: free-choice feeding with rice bran (energy) and soybean meal (protein); C+G: free-choice feeding with corn (energy) and corn gluten meal (protein); R+G: free-choice feeding with rice bran (energy) and corn gluten meal (protein); C+S: free-choice feeding with corn (energy) and soybean meal (protein); R+C+G+S: free-choice feeding with rice bran and corn (energy) and corn gluten meal and soybean meal (protein); and BD: basal diet represented by a complete diet composed of 63% corn and 33% soybean meal. The results indicated that the adjustment to nutritional requirements does not depend only on the ability of birds to select feed. It might also depend on intake and ingredient quality, since some ingredients did not provide a balanced amount of nutrients. The birds were able to fulfill their requirements for maintenance, that is, they consumed the minimum amount of amino acids (g per day) for maximum growth. The free-choice group with corn gluten meal as the protein source had the worst performance, which indicated that this feed is not recommended as a primary source of amino acids for broilers. The C+G diet presented the highest digestibility coefficient of dry matter and crude protein, whereas the C+S diet resulted in the highest digestibility coefficient of ether extract and nitrogen-free extract, indicating that diet digestibility was affected by the type of feed used as energy and protein sources. In general, the high digestibility values indicate that broilers are able to efficiently digest and absorb the supplied feed.

Qualidade protéica de linhagens de soja com ausência do Inibidor de Tripsina Kunitz e das isoenzimas Lipoxigenases

OBJETIVO: Avaliar a qualidade protéica de farinhas de soja, que diferem entre si com relação à presença de lipoxigenases e/ou Inibidor de Tripsina Kunitz. MÉTODOS: Procedeu-se aos ensaios biológicos com ratos, em que foram avaliados a Razão da Eficiência Protéica, Razão Protéica Líquida, Utilização Protéica Líquida e a digestibilidade. Determinou-se a composição aminoacídica das farinhas e cálculo do Escore Químico Corrigido pela Digestibilidade. RESULTADOS: Os valores de Razão da Eficiência Protéica, Razão Protéica Líquida, Utilização Protéica Líquida para as variedades de soja foram inferiores aos valores obtidos para caseína. Para as farinhas sem Inibidor de Tripsina Kunitz foram obtidos valores de digestibilidade maiores que para as farinhas com Inibidor de Tripsina Kunitz, e esses foram bem próximos aos da caseína. Com relação ao teor aminoacídico, constatou-se que o aminoácido limitante dessa soja é lisina e não metionina, ao contrário do que aponta a literatura. CONCLUSÃO: A eliminação genética do Inibidor de Tripsina Kunitz melhora consideravelmente a digestibilidade da proteína de soja. Os resultados do Escore Químico Corrigido pela Digestibilidade não indicaram diferença entre as farinhas sem Inibidor de Tripsina Kunitz das farinhas derivadas de linhagens com Inibidor de Tripsina Kunitz, como foi observado pelos resultados da digestibilidade in vivo.

The use of markers to determine energy metabolizability and nutrient digestibility in avian species

Apart from elimination of errors in obtaining exact measurements of feed intake and total faeces output in the traditional total collection method, the use of markers to determine nutrient digestibility of feeds in animal species would fit into animal welfare considerations. The external marker chromic oxide has been the prominent marker in the 1960s to evaluate metabolizable energy content of feeds for poultry. A preliminary feeding period of 5 days and collection of a sample representing day and night excreta over a 24 hour period have been suggested as protocol to get reliable results with the use of chromic oxide as marker. However, difficulty in obtaining repeatability between laboratories because of the analytical assay for chromic oxide, variability in results, incomplete and inconsistent recovery in excreta, and hazardous possibilities, resulted in replacement of the chromic oxide marker technique with the method of total excreta collection. Although titanium dioxide, which can be analysed by an accurate and simple colourimetrical assay, has been used in several studies in poultry, only one study has evaluated this marker for recovery (98%) in excreta. The internal marker, acid-insoluble ash, which also could present an external marker when the internal content is aided with the use of siliceous substances, is gaining popularity in recent times, although most studies presented higher digestibility values with this marker in avian species than those derived through the total excreta collection method. Lack of standardisation of analytical assays could partly explain the latter phenomenon. Although crude fibre has presented recovery rates of near 100% in excreta of laying hens and turkeys, fear of possible digestion of this substance by cecal microflora has prevented the further utilisation of this substance as marker. Lignin, determined by digestion in 72% sulphuric acid, presented recovery rates of 99 and 98% in chickens and ostriches, respectively, and similar (P>0.05) results than the total collection method in partridges. The elimination of the use of markers to determine energy metabolizability and nutrient digestibility with avian species have been based on a small number of studies conducted mainly before 1965, and extrapolation of results obtained with other animal species.

Increasing nutrient availability of feather meal for ruminants and non-ruminants using an ammonia pressurisation/depressurisation process

An ammonia pressurisation/depressurisation process (PDA) was evaluated for efficacy in enhancing solubility and digestibility of feather meal (FM) protein. Commercial FM was processed for 5 min with variable ammonia loadings (0.5–2 g g−1 DM), moisture contents (10–50%) and temperatures (75–90 °C). Dry matter and protein solubility were determined in a 0.15 M NaCl solution (6 h, 39 °C) and soluble protein content was determined by the Lowry method. Ruminal solubility was determined by the Kjeldahl method as protein lost in the rumen (1 min) of a cannulated steer. Protein digestibility (crude protein by Kjeldahl analysis) was determined using the in situ dacron bag and pepsin techniques. Protein solubility in the untreated FM was low (13.3 and 7.2%, in NaCl and in rumen fluid, respectively) and increased (p < 0.05) to 39.4 and 23.0%, respectively, in the treated FM at the optimal conditions (50% moisture, 2 g ammonia g−1 dry FM and 90 °C). Ruminal and pepsin protein digestibilities increased (p < 0.05) with increasing moisture content, ammonia loading and temperature. Protein digested in the rumen at 12 h increased from 21.9 (untreated) to 43.0%. Highest digestibility value at 48 h was 54.8%. Pepsin protein digestibility increased (p < 0.05) from 35.4% in the untreated FM to 89.3% in the optimal treatment. Protein solubility in NaCl correlated very well (0.98) with pepsin digestibility. The 3-fold increase in solubility and 2-fold increase in digestibility could improve nutrient availability of FM and increase its value as a protein source for both ruminants and non-ruminants. © 1999 Society of Chemical Industry

Ruminal and total plant cell-wall digestibility estimated by a combined in situ method utilizing mathematical models.

Three ruminally and duodenally cannulated non-lactating Finnish Ayrshire cows were used to investigate ruminal and intestinal digestion of cell-wall carbohydrates by a combined in situ method. Five grasses cut at 10 d intervals were incubated in the rumen for 0, 6, 12, 24, 48, 72 and 96 h, and the undegraded residues were exposed to intestinal digestion. With advancing maturity of grass both the rate and extent of cell-wall digestion decreased. At early stages of growth the decreases were faster for the rate of digestion and at late stages of growth for the extent of digestion. Applying a passage rate of 0.02/h in one compartmental rumen model resulted in digestibility values markedly lower than typically observed in vivo. However, applying a rumen model incorporating a selective retention of particles and time-dependent release of particles from the non-escapable pool resulted in much higher digestibility values. Recovery of lignin after 96 h ruminal incubation with a subsequent mobile-bag incubation was very low (from 244 to 460 mg/g). Intestinal disappearance of neutral-detergent fibre (NDF) and hemicellulose decreased with advancing maturity of grass and with increasing length of preceding ruminal incubation period, i.e. with decreasing potential digestibility of the material. Disappearance of hemicellulose was much greater than that of cellulose for intact grasses but the difference diminished with increasing length of preceding rumen incubation period. On average, 195 mg/g of potentially digestible NDF disappeared from the mobile bags in the intestines. The post-ruminal digestion as a proportion of the total NDF digestibility varied between 0.034 and 0.058. Despite methodological problems both in ruminal in situ and intestinal mobile bag techniques, these methods can be used to investigate ruminal and intestinal cell-wall digestion and to partition cell-wall digestibility between ruminal and post-ruminal digestion providing that appropriate rumen models are used.

Maintenance energy requirements of the one-humped camel

Five female one-humped camels were fed at maintenance energy and twice maintenance energy in two different periods. Higher digestibility values (63·2 ± 3·06 vs. 50·2 ± 4·44%) were obtained at the higher intake levels. Heat production at the higher feed level was greater than at the lower but proportionately less than values reported for sheep on similar intake levels. The efficiency of conversion of metabolizable energy intake to body tissue was 68%, this figure being higher than previously reported data for the one-humped camel and also higher than most values reported for conventional ruminants.

Evaluation of undehydrated barley feed fractions and dried oat feed fractions from integrated starch-ethanol process in diets of growing pigs

The nutrient digestibility and protein utilization of undehydrated barley fractions: protein (BP), protein fibre mixture (BPF) and distillers solids (DS) at two levels of inclusion in diets fortified to equal lysine content were assayed with growing pigs in a 6 x 6 Latin square. Dried barley fibre (BF), oat protein (OP) and oat fibre (OF) from integrated starch-ethanol production were evaluated as feed ingredients for pigs in three other trials. DS and OP had a higher essential amino acids content than BP, especially with respect to lysine. All fractions had a rather high ether extract content 46-196 g/kg and their fatty acid composition is presented. BP showed higher protein digestibility than DS (0.931 vs. 0.857) and pigs on BP-diet retained more N than on DS-diet. BF showed a low digestibility of OM and CP and 0.1 inclusion of BF mixed with BP depressed CP digestibility and N-retention. A higher protein supply from cereal protein in the diet promoted N-retention but decreased protein utilization. OP had high digestibility and OF was more digestible than BF. The study confirmed the high digestibility and energy values of the proteinous grain fractions and a high protein utilization when adequately fortified with lysine. The fibrous fractions have a rather low nutrient digestibility and their use in pig diets is therefore limited.

The effect of level and source of protein, fibre and fat in the diet on the energy value of compounded pig feeds

The digestibility of protein, fibre and fat sources, when added at various levels to a constant basal diet, was determined in growing pigs. Digestible energy (DE) contents of the foods were estimated by regression of DE intake against level of addition of test food. The DE values (MJ/kg DM) obtained were: fish meal, 19.1; soya bean meal, 17.1; oatfeed, 9.4; extracted rice bran, 11.3; sugar beet pulp, 12.7; tallow, 38.8; palm acid oil, 37.5; soya oil, 40.8. The DE of barley was 14.7 MJ/kg DM and the DE of wheat was calculated to be 15.2 MJ/kg DM. The DE values of barley and fish meal with pregnant sows were 14.7 and 19.2 MJ/kg DM, respectively. Digestibility of fibre components was very variable between pigs and sources of fibre, sugar beet pulp having the highest digestibility values. Digestibility values for the fat sources were high at 0.963, 0.917 and 0.981 for tallow, palm acid oil and soya oil, respectively. Prediction of dietary DE from fibre content was best achieved by use of neutral detergent fibre (DE = 17.37 − 0.016 NDF; R 2 = 0.90). Application of predictive equations derived from diets with one fibre source to another source gave rise to substantial error. Prediction of dietary DE from oil content was more successful, and predictive equations were similar for all fat sources.

Protein Quality of Raw and Autoclaved Plant Protein Blends

The protein quality of both raw and autoclaved plant protein blends was evaluated in weanling male rats by determining the net protein ratio and the net protein utilization derived from liver nitrogen values. True digestibility of these blends was also determined in order to evaluate whether digestibility was the only factor that affected protein quality as revealed by the other parameters. Casein and lactalbumin were reference standards. Combinations of corn meal, whole wheat meal, ground polished rice, oats, white beans, and solvent-extracted meals of soybean, peanut and sesame were studied. All blends were autoclaved at 1.034 kg/cm2 (15 lb.) pressure for 20min. Improvements in protein quality were obtained when each of the blends was autoclaved, but some blends showed greater improvements than others. In most cases the heat treatment resulted in greater digestibility which was directly reflected in higher net protein ratio and net protein utilization values. However, the relatively high true digestibility value for one of the raw blends was reduced by autoclaving. In spite of this, both the net protein ratio and net protein utilization were improved significantly by autoclaving. Therefore, other factors besides digestibility had an effect on protein quality. Certain plant protein blends can be effective substitutes for good quality animal proteins if adequate heat treatment is used.

Digestibility of sorghum proteins.

Published information indicates that rice, maize, and wheat proteins are much more digestible in children than sorghum proteins are (66-81% compared with 46%). However, this digestibility difference cannot be demonstrated with the weanling rat, which gave digestibility values of 80% for cooked and 85% for uncooked sorghum gruels. Therefore, a search was made for a laboratory system sensitive to the digestibility differences between sorghum and other cereals. We found that porcine pepsin in vitro shows these digestibility differences. Using pepsin, we have found that uncooked sorghum proteins have a high digestibility (78-100%), which drops to a range of 45-55% after cooking. Two fermented sheet-baked sorghum products (kisra and abrey) from Sudan gave pepsin digestibility values of 65-86%. In contrast, unfermented cooked gruels made in our laboratory from the same flours used for the kisra and abrey gave pepsin values of only 44-56%. Therefore, fermentation improves pepsin digestibility of sorghum. The digestibility values of other sorghum-based foods prepared in the semiarid tropics need surveying. Those with high pepsin digestibility values hopefully should be more digestible (in children) than are the cooked sorghum gruels studied to date by human nutritionists.

Fortification of maize flour based diets with blends of cashewnut meal, African locust bean meal and sesame oil meal

AbstractThe relative efficacy of protein blends (Blends I, 2:1:1; II, 1:2:1; III, 1:1:2, IV, 3:1:0; V, 1:3:0; VI, 3:0:1; VII, 1:0:3; VIII, 0:3:1 and IX, 0:1:3 of cashewnut, African locust bean and Beninseed flours) as compared to some commercially available baby foods ( “Farlene”, “Cerelac”, “Farex” and “Cow and Gate” cereal food) in meeting the protein needs of weanling albino rats have been studied. Growth promoting ability of the different blends ranged between 0.75 and 4.73 g/day while those for the commercial foods were 2.64–4.59 g/day. The values of 4.73 and 4.61 g/day for blends I and II were the best, being comparable to those of 4.59 g/day for “Cow and Gate” Cereal food but superior to those of 3.41 and 2.64 g/day for “Farlene” and “Cerelac”. The protein efficiency ratio (PER), net protein retention (NPR), net protein utilisation (NPU) and biological value (BV) for blends I and II were respectively 3.6, 4.4, 72.4 and 75.9 and 3.11, 3.8, 69.1 and 72.4, compared with the values of 2.5, 3.3, 65.8 and 69.5; 4.80, 0.41, 85.8 and 90.1; 3.2, 4.0, 73.5 and 76.1 and 4.0, 4.8, 76.5 and 79.8 for “Farlene”, “Cerelac”, “Farex” and “Cow and Gate” cereal food respectively. The blends and commercial baby foods showed high true digestibility values between 94.9 and 98.1 %. The results are discussed in the light of balance and limitation of amino acids in the component oil seed meals.

Zur Problematik des Stickstoff-Stoffwechsels monogastrischer Tierarten

A new method has been developed for determining the proportion of endogenic and exogenic faecal N by measuring the degree of specific labelling in the feeding-stuff (administered orally) and in the excreta (faeces and urine). The method has also been developed to find out whether the endogenic excretion of intestinal N is actually independent of the N intake. The present technique had been worked out on the basis of the model that had been originally established by Czarnetzki et al. in 1969 with the aim of characterizing processes of nitrogen metabolism in monogastric animals. As a result, a multi-compartment model was developed and a number of conclusions were derived from it. These conclusions were tested in 3 series of experiments on rats fed 15N labelled spring barley and 15N labelled feed yeast. Additionally, 15N labelled experimental rats were used receiving unlabelled extracted soya bean meal. The proportion of endogenic intestinal nitrogen (DVN) varied between 15-22% relative to the proportion of N ingested. The relative proportion of endogenic faecal N in the tota faecal N was found to be 100% in the case of the nitrogen-free diet. With increasing levels of dietary N this proportion lended to decrease down to a final value that was quite characteristic for each partitular feeding-stuff. The absolute amount of endogenic faecal N, however, was found to increase with increasing N levels. This shows that contrary to current views, DVN is not constant and is not independent of protein intake. Rather, a close relationship was found to exist between the level of N intake and DVN excretion (r = 0.951...0.972). So, the proportion of exogenic N contained in the faeces is much smaller than was previously assumed on the basis of the classical and regressive methods. These were based on the assumption that DVN is constant. Consequently, higher digestibility values will be obtained in comparison with those calculated on the basis of the previous methods. Digestibility data for spring barley increased from 83.9 to 95.6, i.e. by 11 digestibility units; for feed yeast there was an increase by 6.2 units, from 83.3 to 90.0; and for extracted soya bean meal an increase of 6.2 units was observed (from 90.7 to 96.9).

FACTORS AFFECTING THE VOLUNTARY INTAKE OF SILAGE AND HAY

Experiments with cows and sheep are described in which the voluntary intakes of hay and silage of differing digestibility were determined. The voluntary intake of hay increased consistently with increasing digestibility, but the relationship was not as well defined for silage. The addition of concentrates depressed the intake of hay, and this effect was more marked for hay with a high digestibility than with poorer quality hay. Concentrates appeared to depress the intake of hay by sheep more than by cows, an effect which was again more marked when the hay had a high digestibility value.