Apparent digestion coefficients for dry matter, protein and essential amino acids in terrestrial ingredients for Pacific shrimp Litopenaeus vannamei (Decapoda: Penaeidae)

Protein quality mainly depends on the essential amino acid (EAA) profile, but also on its bioavailability, because EAA digestibility is generally lower than the analyzed amounts. This information is needed in the aquaculture industry for aquafeed formulation. For this purpose, the apparent digestibility coefficients of dry matter, protein, and essential amino acids of eight feedstuffs of terrestrial origin were determined for the juvenile whiteleg shrimp Litopenaeus vannamei (15-19 g), using 1% chromic oxide as an inert marker. A reference diet was formulated and produced in the laboratory. Eight experimental diets were prepared each with 30% of one of the experimental ingredients added to the reference diet: casein, porcine byproduct meal poultry byproduct meal, corn meal, wheat gluten meal, soybean paste, sorghum meal, and wheat meal. The experiment consisted of a single-factor, completely randomized design with three replicates per treatment. Samples of ingredients, diets and feces were analyzed for nitrogen and amino acids. For amino acid assay, we used reverse-phase high performance liquid chromatography. To avoid partial loss of methionine and cystine, samples of ingredients, diets, and feces were oxidized with performic acid to methionine sulfone and cysteic acid prior to acid hydrolysis. The apparent dry matter and protein digestive utilization coefficients varied from 68% to 109% and from 70% to 103%, respectively. Apparent digestibility of protein for casein, soy paste, wheat meal and wheat gluten were very high (over 90%), corn gluten and poultry byproducts meal showed high protein digestibility (over 80%), but porcine byproducts meal and sorghum meal had low digestibility (76% and 70%, respectively). There was a reasonable, but not total, correspondence between apparent protein digestibility and average essential amino acid digestibility coefficients, except for arginine in corn gluten, phenylalanine and leucine in sorghum meal, phenylalanine in soy paste and lysine in wheat meal and poultry by-product meal. The most digestible feed ingredients for whiteleg shrimp were: wheat gluten, wheat meal and soy paste; poultry byproduct meal and corn gluten were less digestible and the lowest digestibility occurred in porcine byproduct meal and sorghum meal. Feedstuffs exhibited great variability in dry matter, protein and amino acid digestive utilization coefficients, which should be considered when formulating shrimp feeds.     

长吻对鱼粉等六种商品饲料中粗蛋白和能量的消化率

本试验以三氧化二铬（Ｃｒ２Ｏ３）为指示物测定Ⅰ龄长吻对鱼粉、猪血粉、豆饼粉、菜籽饼粉、小麦粉和玉米蛋白粉等六种商品饲料原料粗蛋白和总能量的消化率。试验饲料由参考饲料和试验原料以７０∶３０的比例混合挤压制成颗粒饲料。试验鱼粪便样品用虹吸方式收集,并将测试的消化率结果经过降低１０％的校正。由此所得消化率值更能反应长吻的消化生理状况。另外本文对六种饲料的消化率结果进行了讨论。     

黄颡鱼对四种动物性蛋白原料在不同制粒工艺下的表观消化率研究

实验以三氧化二铬(Cr2O3)为外源指示剂,采用"70%基础饲料+30%实验原料"的方法配制实验饲料,测定了初始体质量为(28.68±0.49) g的黄颡鱼(Peltobagrus fulvidraco)对国产鱼粉、进口鱼粉、进口鸡肉粉和脱脂黄粉虫粉在膨化制粒和非膨化制粒两种工艺下的干物质、粗蛋白、粗脂肪和氨基酸表观消化率。结果显示,在非膨化制粒工艺下,黄颡鱼对进口鸡肉粉的干物质表观消化率显著高于另外3种原料(P<0.05),黄颡鱼对黄粉虫粉蛋白消化率最低(P<0.05),黄颡鱼对进口鸡肉粉脂肪表观消化率显著高于国产鱼粉和进口鱼粉(P<0.05);在膨化制粒工艺下,进口鸡肉粉的干物质表观消化率显著低于另外3种原料(P<0.05),国产鱼粉和进口鱼粉的粗蛋白质消化率达94%以上,显著高于另外两种原料(P<0.05),但进口鸡肉粉的脂肪表观消化率显著低于其他原料(P<0.05)。在非膨化制粒工艺和膨化制粒工艺下国产鱼粉、进口鱼粉和黄粉虫粉的干物质表观消化率无显著性差异,但在非膨化制粒工艺下进口鸡肉粉的干物质表观消化率显著高于膨化制粒工艺(P<0.0...     

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal, soybean meal and white flakes

The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.     

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal,soybean meal and white flakes

Abstract

The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.     

Amino Acid Profile of Escaped Feed Protein After Rumen Incubation and Their Intestinal Digestibility

The crude protein content and amino acid profile of seven feedstuffs (linseed meal, maize gluten meal, rapeseed meal, rapeseed meal protected, soybean meal, fullfat soybean extruded and sunflower meal) were determined before and after ruminal incubation for 16h in three bulls with large rumen cannulas. The intestinal disappearance of amino acids was measured using mobile bag technique. Ruminal incubation affected amino acid profile of all experimental feedstuffs. Crude protein degradation varied from 29.3% for maize gluten meal to 86.4% for rapeseed meal. A tendency towards increased disappearance was observed for glutamic acid, histidine, lysine and proline and decreased disappearance for branched-chain amino acids. The intestinal crude protein digestibility was higher than >80%, except rapeseed meal (66.4%) and sunflower meal (77.8%). The least digestible individual amino acids were methionine and isoleucine in rapeseed meal, histidine and methionine in rapeseed meal protected and arginine in sunflower meal. In general, the lowest amino acid digestibilities were found in feedstuffs with the highest fibre content. The feedstuffs show that they have different potential for supplying of limiting amino acids. Of particular value are the feedstuffs with low crude protein degradability in the rumen and high intestinal digestibility of amino acids.     

Optimizing the protein nutrition of growing-finishing pigs

Growing-finishing pigs should consume each day the minimum amounts of energy and amino acids needed for maximum lean deposition. This should optimize performance traits, carcass leanness, and N excretion. These ideal conditions are difficult to achieve under experimental or farm conditions due to the factors affecting amino acid requirements and feed intake on a daily basis. Lean deposition rate and sex are two of the major factors affecting amino acid needs. If possible, maximum lean deposition rates should be determined for each herd in order to customize feeding programs, and split-sex feeding will improve N utilization.

Amino acid requirements have been determined empirically and by the factorial method. The latter is preferred if the efficiency of use of absorbed amino acids can be accurately determined. Development of computer models will likely be needed to accomplish this. Apparent ileal digestibility of amino acids is the most practical means of estimating amino acid absorption at present, although it likely overestimates amino acid availability for some amino acids.

Crystalline amino acids can be used to improve amino acid balance and reduce excessive intake of protein which should improve feed efficiency. A portion of the high-quality protein feeds in pig diets can be replaced by synthetic amino acids without sacrificing performance, but the effects of these substitutions on carcass merit is uncertain.

Excretion of N, and the concomitant reduction of N in manure that has to be disposed of, can be manipulated nutritionally by increased use of crystalline amino acids to lower dietary protein, by use of highly digestible feedstuffs and by precise matching of amino acid needs to amino acid supply. Use of these factors could lead to a reduction in total N wastes of 20–30%.     

Feed formulations to reduce N excretion and ammonia emission from poultry manure

This summary focuses on reducing nitrogen (N) and ammonia emissions from poultry manure through the use of improved amino acid digestibilities and enzyme supplementation. Proper feed processing techniques, phase feeding, and the minimization of feed and water waste can contribute to additional minor reductions in these emissions. Reductions in environmental pollution can be achieved through improved diet formulation based on available nutrients in the ingredients, reducing crude protein (CP) levels and adding synthetic amino acids. Use of amino acid and CP digestibilities can reduce N excretion up to 40% and a 25% increase in N digestibility can be achieved with enzyme supplementation in broiler diets. Digestibilities can be measured by two methods: the excreta and ileal amino acid digestibilities. Both methods allow amino acid levels to be reduced by 10% or more. Enzyme supplementation decreases intestinal viscosity, improves metabolizable energy levels, and increases amino acid digestibilities. Many feed manufacturers still use total amino acid content to formulate feeds. To meet amino acid requirements, crystalline amino acids are needed. The use of feather, meat and bone meal must not be overestimated or underestimated and the limiting amino acids such as cystine, tryptophan, and threonine must be carefully analyzed.     

Identification of a Low Digestibility δ-Conglutin in Yellow Lupin (Lupinus luteus L.) Seed Meal for Atlantic Salmon (Salmo salar L.) by Coupling 2D-PAGE and Mass Spectrometry

The need of quality protein in the aquaculture sector has forced the incorporation of alternative plant proteins into feeding diets. However, most plant proteins show lower digestibility levels than fish meal proteins, especially in carnivorous fishes. Manipulation of protein content by plant breeding can improve the digestibility rate of plant proteins in fish, but the identification of low digestibility proteins is essential. A reduction of low digestibility proteins will not only increase feed efficiency, but also reduce water pollution. Little is known about specific digestible protein profiles and/or molecular identification of more bioavailable plant proteins in fish diets. In this study, we identified low digestibility L. luteus seed proteins using Atlantic salmon (Salmo salar) crude digestive enzymes in an in vitro assay. Low digestibility proteins were identified by comparing SDS-PAGE banding profiles of digested and non-digested lupin seed proteins. Gel image analysis detected a major 12 kDa protein band in both lupin meal and protein isolate digested products. The 12 kDa was confirmed by 2D-PAGE gels and the extracted protein was analyzed with an ion trap mass spectrometer in tandem mass mode. The MS/MS data showed that the 12 kDa low digestibility protein was a large chain δconglutin, a common seed storage protein of yellow lupin. Comparison of the protein band profiles between lupin meal and protein isolates showed that the isolatation process did not affect the low digestibility of the 12 kDa protein.     

Untersuchungen Zur Anwendung Der Mobilen Beuteltechnik Bei Schweinen

Abstract

Für die Durchführung der mobilen Beuteltechnik (MBT), die zur Ermittlung der präzäkalen und Gesamt-Rohproteinverdaulichkeit und Aminosäurenresorption (Lysin, Methionin, Zystin, Threonin, Tryptophan) bei 10 Einzelfuttermitteln (Ackerbohne, Lupine, Rapsextraktionsschrot, Fischmehl, Gerste, Weizen) und 3 Rationen zur Anwendung kam, wurden jeweils 2 weibliche ileorektostomierte sowie intakte Schweine mit einfachen Duodenalkanülen benutzt. Je Versuchsfutter und Tier kamen 36 Polyamidbeutel zum Einsatz. Nach peptischer Vorverdauung in vitro, Applikation durch die Duodenalkanüle und Passage durch den Darmtrakt wurden die im Beutel verbliebenen Rückstände für jedes Tier und Futtermittel zu einer Sammelprobe vereinigt und diese wie das Ausgangsmaterial auf Trockensubstanz, Stickstoff und Aminosäuren analysiert. Die direkt ermittelten Verdaulichkeiten (BV) und über regressive Berechnung erhaltenen Werte (BVb) wurden mit den in konventionellen Verdauungsversuchen bestimmten scheinbaren Verdaulichkeiten (sV) verglichen.

74% aller BV-Daten waren höher als die entsprechenden scheinbaren Verdaulichkeiten. Die Gegenüberstellung von BV und sV ergab bei 58%, die von BVb und sV nur noch bei 17% Abweichungen von > ± 4 Verdaulichkeitseinheiten.

Mit Additivitätsrechnung wurde bei Rationen überprüft, ob die über die BV der Einzelkompo-nenten berechnete BV einer Ration zum gleichen Ergebnis führt, wie die direkt für die Mischung bestimmte. Dabei traten teilweise gegenläufige Resultate auf. Daraus wird die Schlußfolgerung gezogen, daß die Anwendung der MBT bei Mischfutterrationen durch weitere Untersuchungen überprüft werden muß; bei Einzelfuttermitteln kann sie jedoch nach regressiver Verrechnung der Ergebnisse zur schnellen und vereinfachten Verdaulichkeitsermittlung genutzt werden.

INVESTIGATIONS INTO THE USE OF THE MOBILE BAG TECHNIQUE IN PIGS

1. Estimation of the apparent crude protein digestibility and amino acid absorption of feedstuffs and diets

The mobile bag technique (MBT) was used in two ileorectostomized and two intact pigs with duodenal cannulae, in order to estimate the precaecal and total crude protein digestibility and amino acid (lysine, methionine, cystine, threonine, tryptophan) absorption of ten single feedstuffs (field bean, lupin, rapeseed meal, fish meal, barley, wheat) and three diets. For each feed 36 bags were applied per animal. After a peptic predigestion in vitro, application of the bags through the duodenal cannula into the intestine and their passage through the gut, the residues remaining in the bags were pooled to collective samples and just as the original feed material analysed on dry matter, nitrogen and amino acids. The directly determined MBT-digestibilities (BV) and the values obtained by regressive calculations (BVb) have been compared with apparent digestibilities (sV) conducted from conventional digestion experiments.

74 per cent of all BV data was higher than the corresponding sV values. Similarities of BV with sV showed in 58 per cent, those of BVb with sV only in 17 per cent. In all cases differences of > ± 4 digestibility units showed.

Checking additivity of diet-BV by means of calculations from the BV of their single ingredients did not generally lead to the same results as the directly estimated diet-BV; in some cases the results were contrary. Therefore the use of MBT for mixed feed diets has to be further investigated. For single feedstuffs the MBT can be used successfully as a rapid and simple technique when regressive calculations are employed.     

Digestibility of amino acids in organically cultivated white-flowering faba bean and cake from cold-pressed rapeseed, linseed and hemp seed in growing pigs

The study aimed at determining the ileal apparent (IAD) and standardised ileal (SID) digestibility of crude protein (CP) and amino acids (AA) in organically cultivated white-flowering faba beans (Vicia faba), and cakes from hemp seed (Cannabis sativa), linseed (Linum usitatissimum) and rapeseed (Brassica napus). The experiment was designed as a four period cross-over trial with six castrated male Yorkshire pigs fitted with post valve T-caecum (PVTC) cannulas. The IAD and SID of CP for the feed ingredients ranged from 79.2-85.9% and were affected by dietary treatment, with significantly lower values in rapeseed cake. The IAD and SID of most AA in the feed ingredients were also significantly affected by dietary treatment, but without any consistent trend. However, the overall digestibilities were in general comparable with conventional protein feed ingredients. Thus, these alternative protein feed ingredients have the potential to be used to a greater extent when formulating organic pig diets.     

Bacterial protein meal produced on natural gas replacing soybean meal or fish meal in broiler chicken diets

The effects of replacing soybean meal or fish meal with 2, 4 or 6% bacterial protein meal (BPM) on growth performance, ileal digestibility of amino acids and sensory quality of meat, were examined using 630 broiler chickens. Weight gain from 7-32 days of age did not differ significantly among the treatments. Efficiency of feed conversion was increased when BPM replaced soybean meal, and abdominal fat deposition tended to decline. Feed conversion was not affected when BPM replaced fish meal. Amino acid digestibility was unaffected or improved when BPM replaced soybean meal, whereas replacement of fishmeal with BPM resulted in similar digestibility. Sensory quality of fresh thigh meat was similar among treatments, but for freeze-stored chest meat replacement of fish meal with BPM reduced off-odour and off-flavour and increased juiciness. It was concluded that 6% BPM can replace soybean meal or fish meal protein in broiler chicken diets.     

Feed selection and digestibility by captive giraffe

A digestion trial with subsequent examination of feed selection was conducted using two captive giraffe fed four feedstuffs. Apparent digestibility coefficients were relatively high, indicating that the animals were efficiently utilizing the feedstuffs. However, values could be affected by the possible ingestion of soil containing acid-insoluble ash. A high fiber pelleted feed was eaten in a greater quantity than a low fiber feed, even though the constituents in each feed were the same. Gross energy content of residual hay was higher than gross energy content of the offered hay. whereas neutral detergent fiber and acid detergent fiber content were lower in the residual than in the offered hay. The animals did not appear to be selecting for a diet high in energy or low in fiber. Based on these results and other information, re-classification of giraffe as a facultative concentrate selector or as an intermediate feeder may be appropriate.     

Evaluating standardized ileal digestibility of amino acids in growing pigs

The ileal digestibility coefficient (CSID) of amino acids (AA) and crude protein (CP) in 40 feedstuffs for growing pigs were determined with the protein-free (PF) and enzyme-hydrolyzed casein (EHC) methods. The 40 feedstuffs that were used earlier were 10 samples of cereals and cereal by-products, 12 samples of legumes, 6 samples of animal protein feedstuff and 12 samples of oil seed meals. Six growing pigs (initial body weight of 35 ± 1.5 kg), fitted with T-cannula at the terminal ileum, were randomly allocated to either a PF or a EHC diet according to a crossover design during two ileal digesta collection periods. In each period, pigs were adjusted to the experimental diets for 5 days. On days 6 and 8, ileal digesta were collected continuously for 24 h to determine ileal endogenous AA and CP losses. Pigs fed the EHC diet had a higher ileal flow of endogenous CP and of most of AA (P<0.05) than pigs fed the PF diet. Among the ileal endogenous AA flows (g/kg dry matter intake for pigs), methionine excretion was the lowest in pigs (0.09 and 0.25 g/kg dry matter intake) fed the PF and EHC diet, respectively, whereas glutamate (1.83 g/kg dry matter intake) and proline (1.22 g/kg dry material intake) excretion were the highest in pigs fed the EHC and the PF diet, respectively. Endogenous losses of CP and AA determined in the current study and previously published data on apparent ileal digestibility [Yin, Y.L., Huang, R.L., Zhong, H.Y., Chen, C.M., Li, T.J., Pan, Y.F., 1993. Nutritive value of feedstuffs and diets for pigs: 1. Chemical composition, apparent ileal and fecal digestibilities. Anim. Feed Sci. Technol. 44, 1–27] were used to calculate CSID coefficients. For most cereals and cereal by-products, the CSID coefficients of CP determined by the EHC method were higher than those determined by the PF method. Arginine, lysine, methionine, threonine, valine, alanine, aspartate, glutamate, glycine, proline and serine in some cereals and cereal by-products; methionine, valine, alanine and proline in some legumes; and methionine, alaline and proline in some oilseed meals had higher CSID determined by the EHC method than the PF method indicating that there are methodological differences when evaluating the CSID of feed ingredients.     

Bacterial protein meal produced on natural gas replacing soybean meal or fish meal in broiler chicken diets

Abstract

The effects of replacing soybean meal or fish meal with 2, 4 or 6% bacterial protein meal (BPM) on growth performance, ileal digestibility of amino acids and sensory quality of meat, were examined using 630 broiler chickens. Weight gain from 7 – 32 days of age did not differ significantly among the treatments. Efficiency of feed conversion was increased when BPM replaced soybean meal, and abdominal fat deposition tended to decline. Feed conversion was not affected when BPM replaced fish meal. Amino acid digestibility was unaffected or improved when BPM replaced soybean meal, whereas replacement of fishmeal with BPM resulted in similar digestibility. Sensory quality of fresh thigh meat was similar among treatments, but for freeze-stored chest meat replacement of fish meal with BPM reduced off-odour and off-flavour and increased juiciness. It was concluded that 6% BPM can replace soybean meal or fish meal protein in broiler chicken diets.     

Effects of exogenous enzymes on apparent nutrient digestibility in rainbow trout (Oncorhynchus mykiss) fed diets with high inclusion of plant-based protein

Plant-based protein ingredients are increasingly used in feed for carnivorous fish as replacement for fish meal. This study investigated if supplementing diets with high inclusion levels of plant-based protein with three different enzymes could improve the apparent nutrient digestibility in juvenile rainbow trout (Oncorhynchus mykiss). Three diets with high inclusion levels of either de-hulled, solvent extracted soybean meal (344 g/kg), sunflower meal (246 g/kg), or rapeseed meal (264 g/kg) were produced and feed batches were coated post-extrusion with the different enzymes: β-glucanase at 67 mg/kg, xylanase at 208 mg/kg, protease at 228 mg/kg, or a combination of the three enzymes at the same doses. Three consecutive digestibility trials were carried out using a flow-through, modified Guelph System. Each trial was designed to include five dietary treatment groups: a non-supplemented control diet and 4 diets supplemented with either β-glucanase, xylanase, protease or a combination of the three enzymes. Diets were fed to triplicate tanks and two faecal sampling periods for digestibility measurements for each tank were scheduled. Each experiment comprised a 10-day digestibility trial succeeded by a water sampling period for measuring the dissolved nitrogen (N) output. Each experiment lasted 17–19 days in total.Apparent digestibility coefficients (ADCs) of protein, fat, ash, phosphorus and dry matter (DM) were derived from the three digestibility trials, along with calculations of the specific growth rate (SGR, %/d) and feed conversion ratio (FCR). Nitrogen mass-balance and energy retention were evaluated for each dietary treatment group to elucidate on the utilization of digested nutrients and energy.Enzyme supplementation had only moderate effect on apparent nutrient digestibility in the sunflower and rapeseed experiments, while β-glucanase and protease improved the apparent digestibility of all dietary nutrients in the soybean experiment (P<0.05). The effect was more pronounced for lipid than for other nutrients. β-Glucanase had a positive effect on energy retention in the soybean experiment (P<0.05), while there were no effects on nitrogen retention or fish performance in any of the three experiments (P>0.05) during the short feeding periods. The study thus provides preliminary results on the potential of β-glucanase and protease to increase apparent nutrient digestibility of soybean meal in fish feed.     

Apparent digestibility of wheat bran and extruded flax in horses determined from the total collection of feces and acid-insoluble ash as an internal marker

Several studies have reported data on comparisons between two methods: the total collection of feces and the internal markers method. The aim of this study was to assess the apparent digestibility of two concentrates and to compare the apparent digestion coefficients using the total collection of feces and acid-insoluble ash (AIA) as the internal marker method. In 2009, six adult geldings aged between 3 and 11 years, with an average weight per trial of 543, 540 and 542 kg, respectively, were used to determine the apparent digestibility by means of three in vivo digestibility trials on hay, hay plus wheat bran (60 : 40) and hay plus extruded flax (80 : 20). Feces were collected over a 6-day period with a previous 14-day adaptation period. The three digestibility trials were carried out to determine the digestion coefficients of the three diets and, indirectly, of the two concentrates. The digestion coefficients of the diets were determined for the dry matter, organic matter, crude protein and gross energy, whereas the apparent digestion coefficients of the same parameters were calculated for wheat bran and extruded flax, by calculating the difference from the previous results. The data were analyzed using the Student t-test for paired samples. The digestion coefficients obtained were similar when the total collection of feces and the AIA method were used. Higher data variability, confirmed by a greater standard deviation, was observed using the AIA method to estimate the apparent digestion coefficients. It can be concluded that the use of AIA as an internal marker in digestibility trials on average leads to values similar to those obtained with the total collection of feces and can therefore be considered a less-expensive method to determine apparent digestion coefficients. Nevertheless, the total collection of feces should still be considered the best choice to determine the digestibility of some specific feedstuffs.     

Influence of added microbial enzymes on energy and protein availability of selected feed ingredients

Addition of enzymes to feed ingredients results in an improved energy availability that reduces the difference between gross and metabolisable energy of the raw material. The level of improvement seen is related to enzyme type and to dosage, and correlates well with the substrate specificity of the various enzymes present. Thus the values found in this study are specific for the enzymes and dosages used. Nitrogen retention is also improved by enzyme addition but this did not show a clear dosage response with all materials. An improved nitrogen retention cannot be directly correlated with protein digestibility but an improved retention of protein may offer the possibility to reduce protein levels in the diet.     

Dietary protein source affects lipid metabolism in the European seabass (Dicentrarchus labrax)

The study was undertaken to evaluate the effects of dietary protein sources on lipogenesis and fat deposition in a marine teleost, the European seabass (Dicentrarchus labrax). Four isonitrogenous (crude protein (CP, Nx6.25), 44% DM) and isoenergetic (22-23 kJ/g DM) diets were formulated to contain one of the following as the major protein source: fish meal (FM), one of two soy protein concentrates (SPC) and corn gluten meal (CGM). Apparent digestibility coefficients of the diets and raw ingredients, as well as soluble nitrogen (ammonia and urea) and phosphorus excretion were measured. Growth rates of seabass fed plant protein-based diets were significantly lower than those fed fish meal based diet. The protein utilisation was strongly correlated to the dietary essential amino acids index. Measurements of N excretion (ammonia and urea nitrogen) confirmed these data. Daily fat gain at the whole body level ranged between 1.1 to 1.7 g/kg BW, with the highest values being recorded in fish fed the fish meal based diet. Levels of plasma triglycerides and cholesterol were lower in fish fed soy protein diets than in those fed the diet solely based on fish meal. Soy protein rich diets decreased the activities of selected hepatic lipogenic enzymes (glucose 6-phosphate dehydrogenase, malic enzyme, ATP-citrate lysase, acetylcoenzyme A carboxylase and fatty acid synthetase). Highest lipogenic enzyme activities where found in fish fed the fish meal diet, except for fatty acid synthetase which was increased in seabass fed the corn-gluten meal based diets. Overall data suggest that dietary protein sources affects fat deposition and the lipogenic potential in European seabass.     

The digestibility of raw and processed soybeans by Helmeted Guineafowl,Numida meleagris

Helmeted Guineafowl, Numida meleagris, populations have declined significantly within the Midlands of KwaZulu-Natal since the early 1980s. Because guineafowl have been observed feeding on harvested soybean lands and because raw soybeans are known to contain anti-nutritional factors, research into the digestibility of raw soybeans was conducted to investigate possible localized factors in suppressing populations of these birds. A digestibility study was carried out on the apparent metabolizable energy (AME) and the amino acids of both raw and processed soybeans, as well as a number of other feed ingredients, using Helmeted Guineafowl and adult roosters, Gallus gallus, as a control. The results of the energy balance studies were similar for both the guineafowl and the roosters. Soybean, both raw and processed, was found to be comparable with the other feed ingredients in terms of the digestibility of gross energy, but the amino acid digestibility of raw soybeans was considerably lower than that of processed soybean oilcake meal. The availability of raw soybean may thus only be contributing to localized dietary constraints within guineafowl populations.