Differences In Protein Digestibility Research Articles

In vitro protein digestion and carbohydrate colon fermentation of microbial biomass samples from bacterial, filamentous fungus and yeast sources

This study evaluated the nutritional quality of different microbial biomass samples by assessing their protein digestibility and carbohydrate fermentability in the colon using in vitro methods. Four microbial samples were produced: one hydrogen-oxidizing bacterial strain (Nocardioides nitrophenolicus KGS-27), two strains of filamentous fungi (Rhizopus oligosporus and Paecilomyces variotii), and one yeast strain (Rhodotorula babjevae). The microorganisms were grown in bioreactors, harvested and dried before analysis. The commercial fungal product Quorn was used as a reference. The protein digestibility of the microbial samples was analysed using the INFOGEST in vitro model, followed by quantification of N-terminal amine groups. An in vitro faecal fermentation experiment was also performed to evaluate the degradation of carbohydrates in microbial biomass samples and formation of short-chain fatty acids (SCFA). The fungal biomass samples had higher protein hydrolysis (60–75 %) than the bacterial sample (12 %) and Quorn (45 %), while the yeast biomass had the highest protein digestibility (85 %). Heat-treatment of the biomass significantly reduced its protein digestibility. Total dietary fibre (DF) content of fungal biomass was 31 – 43 %(DW), mostly insoluble, whereas the bacterial biomass contained mainly soluble DF (total DF: 25.7 %, of which 23.5 % were soluble and 2.2 % insoluble). After 24 h of colonic in vitro fermentation, SCFA production from the biomass of Paecilomyces, Quorn and Rhodotorula was similar to that of wheat bran, while 17 % and 32 % less SCFA were produced from the biomass of Rhizopus and the bacterial strain, respectively. Further studies are needed to clarify the reasons for the observed differences in protein digestibility and DF fermentability, especially regarding the cell wall structures and role of post-processing.

Investigation of the effects and mechanism of incorporation of cross-linked/acetylated tapioca starches on the gel properties and in vitro digestibility of kung-wan

The effects and mechanism of incorporation of cross-linked tapioca starch (CTS) or acetylated tapioca starch (ATS) on the gel properties and in vitro digestibility of kung-wan (a Chinese-style meatball) were evaluated. The results indicated that incorporation of either CTS or ATS significantly enhanced the gel properties of kung-wan in a dose-dependent manner (P < 0.05), as well as the rheological properties of meat batter. Moreover, hydrogen bonds and electrostatic interaction were the major intermolecular forces in kung-wan when incorporated with CTS or ATS. Meanwhile, CTS and ATS acted as fillers in the meat protein gel matrix, which was further verified by the microstructure of kung-wan. However, CTS produced a more uniform and dense meat protein gel network than ATS, which was mainly due to its limited swelling characteristics. In addition, the incorporation of CTS or ATS significantly increased the in vitro digestibility of protein in kung-wan with increasing level of addition (P < 0.05). However, no significant differences in protein digestibility were detected between the CTS and ATS groups at the same addition level (P > 0.05). Our results provided some critical points for the actual application of modified tapioca starch to promote the quality profiles of kung-wan.

Comparative effects of high pressure processing and heat treatment on in vitro digestibility of pea protein and starch

The effects of high-pressure processing (HPP) and heat treatment on the digestibility of protein and starch in pea protein concentrate (PPC) were investigated. Samples of PPC with 5% (5 P) and 15% (15 P) protein were treated by HPP (600 MPa/5 °C/4 min) or heat (95 °C/15 min) and their in vitro static and dynamic digestibility were compared to untreated controls. HPP-treated PPC underwent a greater degree of proteolysis and showed different peptide patterns after static gastric digestion compared to untreated and heat-treated PPC. Differences in protein digestibility among treatments during dynamic digestion were only significant (p < 0.05) during the first 20 min of jejunal, ileal, and total digestion for 5 P, and during the first 60 min of ileal digestion for 15 P. Neither static nor dynamic starch digestibility were dependent on treatment. HPP did not reduce trypsin inhibitor activity, whereas heat treatment reduced it by ~70%. HPP-induced structural modifications of proteins and starch did not affect their overall in vitro digestibility but enhanced gastric proteolysis.

Syngenta Enogen Corn Fed as Corn Grain and Corn Silage in Diets Containing Corn Coproducts Did Not Enhance Diet Digestibility in Growing Heifers

Objective: Evaluate the effect of feeding corn grain and corn silage from Enogen corn (EC; Syngenta Seeds, LLC., Downers Grove, IL) or conventional corn (CON) in diets containing either wet distillers grain (WDG; ICM Biofuels, St. Joseph, MO) or Sweet Bran [proprietary wet corn gluten feed (WCGF); Cargill Animal Nutrition, Blair, NE] on intake and digestibility in growing cattle. Study Description: Eight ruminally cannulated crossbred heifers (initial body weight = 816 ± 94 lb) were used in an intake and digestibility study designed as a replicated 4 × 4 Latin square. Four consecutive, 15-day periods consisted of 10 days for diet adaptation, 4 days of fecal sampling, and 1 day of ruminal sampling. Heifers were fed once daily at 10:00 a.m. Chromic oxide (Cr2O3) was used as an external digestion marker to calculate apparent total-tract diet digestibility. Results: Heifers eating EC tended to have greater starch digestibility (P = 0.07) than heifers eating CON. No differences (P > 0.34) in dry matter or fiber digestibilities were observed between corn sources. There were coproduct × hour interactions for concentration of ruminal ammonia (P < 0.01) and two branched chain fatty acids, isobutyrate (P < 0.01) and isovalerate (P < 0.01). In heifers fed WCGF, isobutyrate and isovalerate concentrations reached a peak at 2 hours after feeding, then declined between 2 and 24 hours after feeding. Heifers fed WDG isobutyrate and isovalerate concentrations were greatest at 0 hours after feeding. Differences between concentrations of isobutyrate and isovalerate can be explained by differences in protein digestibility of WCGF and WDG. The Bottom Line: Enogen corn hybrids fed as dry rolled corn and corn silage in diets containing corn coproducts did not result in better diet digestibility compared to conventional corn hybrids, but diets containing WDG may offer better growth performance (Scilacci et al., 2022) for growing cattle due to more ruminally undegradable protein compared to diets containing WCGF.

In Vitro Protein Digestibility of Brown Rice after High-Pressure Freeze-Thaw Cycles and Germination-Parboiling Treatments

HighlightsFTC-4 treated brown rice showed better protein digestibility.BR-AAS was used to evaluate the nutritive value of released free amino acids.G24P treated brown rice is recommended to supplement amino acid intake in a daily diet.Abstract. The objective of this study was to evaluate the in vitro protein digestibility of brown rice (BR) after high-pressure (HP), freeze-thaw cycle (FTC), and germination-parboiling (GP) treatments. Four-cycle freeze-thaw (FTC-4) treatment enhanced digestibility, and all treated BR released more essential and total amino acids after digestion. To evaluate the nutritive value of free amino acids released after digestion (on the premise of the same intake of BR products), a BR amino acid score (BR-AAS) was used, based on the patterns of protein digestibility-corrected amino acid scores with modifications. Results suggested that BR treated with 24 h of germination followed by 10 min of parboiling (G24P) was a better choice for supplementing amino acid intake in a daily diet. All treatments resulted in decreased protein solubility, which was negatively correlated with surface hydrophobicity and disulfide bond contents. The HP, FTC, and GP treatments affected certain protein properties, which was helpful in explaining the differences in protein digestibility of BR. Changes in other constituents were considered important with respect to the treatment influence on protein digestibility. Keywords: Brown rice, Freeze-thaw cycles, Germination-parboiling, High-pressure, Protein in vitro digestibility.

Postprandial Amino Acid Kinetics of Milk Protein Mixtures are Affected by Composition, But Not Denaturation, in Neonatal Piglets

Multiple studies have indicated that formula-fed infants show a different growth trajectory compared with breastfed infants. The observed growth rates are suggested to be linked to higher postprandial levels of branched chain amino acids (BCAAs) and insulin related to differences in protein quality. We evaluated the effects of milk protein denaturation and milk protein composition on postprandial plasma and hormone concentrations. Neonatal piglets were bolus-fed randomly, in an incomplete crossover design, 2 of 3 milk protein solutions: native whey protein isolate (NWPI), denatured whey protein isolate (DWPI), or protein base ingredient, comprising whey and casein (PBI). Postprandial plasma amino acids (AAs), insulin, glucagon-like peptide 1, glucose, and paracetamol concentrations were assayed. Plasma responses were fitted with a model of first-order absorption with linear elimination. DWPI (91% denatured protein) compared with NWPI (91% native protein) showed lower essential amino acids (EAAs) (∼10%) and BCAA (13-19%) concentrations in the first 30-60 min. However, total amino acid (TAA) concentration per time-point and area under the curve (AUC), as well as EAA and BCAA AUC were not different. PBI induced a ∼30% lower postprandial insulin spike than NWPI, yet plasma TAA concentration at several time-points and AUC was higher in PBI than in NWPI. The TAA rate constant for absorption (k a) was twofold higher in PBI than in NWPI. Plasma BCAA levels from 60 to 180 min and AUC were higher in PBI than in NWPI. Plasma EAA concentrations and AUCs in PBI and NWPI were not different. Denaturation of WPI had a minimal effect on postprandial plasma AA concentration. The differences between PBI and NWPI were partly explained by the difference in AA composition, but more likely differences in protein digestion and absorption kinetics. We conclude that modifying protein composition, but not denaturation, of milk protein solutions impacts the postprandial amino acid availability in neonatal piglets.

Differences in nutritional characteristics of three varieties of sorghum grain determine their in vitro rumen fermentation

The effect of phenolic compounds and protein matrix on microbial fermentation of three sorghum grains (S1, S2 and S3) were studied in vitro. Total phenolics and total tannins concentration (g/kg dry matter, DM) were 1.5 and 0.2 for S1, 19.3 and 8.1 for S2 and 2.6 and 1.3 for S3. Protein enzymatic digestibility was 0.614, 0.226 and 0.454, respectively. Trial 1 was conducted for 24 h, without or with polyethylene glycol (PEG) to determine the effect of phenolic compounds on fermentation. Without PEG, gas production for S1 was the highest after 24 h (257, 237 and 238 mL/g organic matter, for S1, S2 and S3; p&lt;0.05), and higher proportion of propionate at the expense of acetate was recorded with S3 after 6 h. Gas produced with S1 and S3 remained unaffected (p&gt;0.10), but increased in S2 by 0.21 to 0.30 with vs. without PEG. No differences in gas production between S1 and S2 were observed with PEG, S3 recording the lowest (p&lt;0.05) values from 8 h onwards. Addition of PEG reduced proportion of butyrate (p&lt;0.05) and increased three-fold lactate (1.62 vs. 4.98 mM; p&lt;0.001). In Trial 2 (12 h) gas production followed a similar pattern. Without PEG, starch disappearance was the highest in S1 (0.356, 0.231 and 0.216, respectively), but no differences were recorded with PEG. Considering differences in protein digestibility and the effect of phenolic compounds, the effect of starch nature and structure on fermentation is apparently minor. Colour of grain is not necessarily related to phenolic compounds proportion or rumen utilization.

Butyrate presence in distinct gastrointestinal tract segments modifies differentially digestive processes and amino acid bioavailability in young broiler chickens.

The hypothesis was tested that butyrate presence in the digesta of distinct gastrointestinal tract (GIT) segments of broilers leads to differential effects on digesta retention time, gut morphology, and proteolytic enzymatic activities, ultimately resulting in differences in protein digestibility. A total of 320 male day-old Ross 308 broilers were randomly assigned to 5 dietary treatments: 1) control (no butyrate), 2) unprotected butyrate (main activity in the crop and gastric regions), 3) tributyrin (main activity in the small intestine), 4) fat-coated butyrate (activity in the whole GIT) and 5) unprotected butyrate combined with tributyrin, each replicated 8 times. Rapeseed meal was used in combination with a fine dietary particle size in order to challenge the digestive capacity of young broilers. Birds were dissected at 22, 23, and 24 d of age and samples of digesta at various GIT locations as well as tissues were collected. Butyrate concentration varied significantly across GIT segments depending on treatment, indicating that the dietary contrasts were successful. The apparent ileal digestibility of methionine tended to increase when butyrate and/or propionate was present in colonic and cecal contents, possibly due to modifications of GIT development and digesta transit time. Butyrate presence in the digesta of the crop, proventriculus and gizzard, on the contrary, decreased the apparent ileal digestibility of several amino acids (AA). In addition, butyrate presence beyond the gizzard elicited anorexic effect that might be attributable to changes in intestinal enteroendocrine L-cells secretory activities. The present study demonstrates that, in broilers, effects of butyrate on digestive processes are conditioned by the GIT segment wherein the molecule is present and indicates its influence on digestive function and bioavailability of AA.

Effect of cell wall characteristics on algae nutrient digestibility in Nile tilapia (Oreochromis niloticus) and African catfish (Clarus gariepinus)

This study aimed to assess the effect of cell wall hardness and fish species on digestibility of unicellular sources. The gross composition, and the composition and cell wall hardness of the sources were determined for four sources. These were 3 microalgae species (Chlorella vulgaris, Scenedesmus dimorphus and Nannochloropsis gaditana) and a cyanobacterium (Arthrospira maxima). Apparent digestibility coefficients (ADCs) of their nutrients were determined in Nile tilapia and African catfish, at a 30% diet inclusion level. It was hypothesized that herbivores can access and thus digest unicellular proteins better than omnivores, and that the differences in protein digestion between the fish species increase with the robustness of the cell walls. Differences in cell wall hardness were quantified as the cells' resistance to mechanical shear. A. maxima was least resistant to shear: the time needed to disrupt 50% of the cells was 2min compared to 24–33min for the other sources. Differences were also measured in nutrient digestibility between the sources in both fish species. Contrary to the basal diet, which was digested differently between the fish species, there was no fish species effect on nutrient ADCs of the unicellular sources. A. maxima had the highest protein ADCs in both fish species (81.4–82.5%), followed by C. vulgaris (80.7–80.9%), N. gaditana (72.4–74.7%) and S. dimorphus (67.0–68.3%). Ingredient fat ADCs ranged between 65.1 and 89.1%. Unicellular non-starch polysaccharides (NSP), comprising the unicellular cell wall fraction, was not inert in both fish species (ADC >46.0%), which was attributed to fermentation. The digestibility data suggest that the differences in nutrient accessibility of unicellular sources are dominant over the differences in digestive systems between herbivorous and omnivorous fish. Nevertheless, nutrient digestibility of the unicellular sources did not relate to the mechanical cell wall hardness.

Acute Effect of Whey Protein Microgels on Whole Body Protein Turnover in Overweight Adults

Differences in protein digestion and absorption are hypothesized to translate into differences in whole body protein synthesis. Whey protein is qualified as a “fast protein” in relation to its speed of digestion and ensuing aminoacidemia in comparison to casein, the “slow protein”. WP has previously been reported to incur a higher muscle protein synthesis as compared to casein; however results are inconsistent at the whole body level.Whey protein microgels (WPM) are aggregates of whey protein allowing the inclusion of high concentrations of whey protein in liquid matrices. Given that WPM have been shown to result in a delayed appearance of amino acids in the plasma as compared to native WP, we investigated the acute effect of WPM on whole body protein turnover using stable isotope methodology, as compared to micellar casein (MC) in a crossover trial on 7 overweight subjects consuming 4 different isocaloric meals: 1) carbohydrate control 2) 30g of WPM, 3) 50g of WPM (WPM50) and 4) 50g of MC (MC50).WPM50 resulted in higher (p&lt;0.0001) plasma levels of leucine, branched chain, and total amino acids as compared to MC50. We observed no significant difference in non‐oxidative leucine disposal whereas protein oxidation was significantly different (p&lt;0.05) between groups, 170.3 ± 5.4, and 334.9 ± 39 for MC50 and WPM50, respectively. Postprandial Leu balance was similar for WPM50 and MC50.We conclude that at a dose of 50g, the effect of WPM on whole body protein synthesis is not significantly different from that of MC, whereas the resulting Leu protein oxidation and plasma amino acids are higher. The lack of effect could be partly explained by the high dose of protein administered potentially reaching a plateau in whole body protein synthesis, as was previously shown on skeletal muscle.

The effect of caralluma fimbriata extract on metabolic parameters in high-fat fed wistar rats

The effect of caralluma fimbriata extract on metabolic parameters in high-fat fed wistar rats

Digestion of protein of two pollen types in China by the honeybee (Apis mellifera L)

Different pollens have varying nutritional value for the honeybee. However, the digestion of the protein in the pollen is still not well understood. Here, we investigated this issue using a rectum-testing method. The results indicated that a higher proportion of the protein in camellia pollen is digested compared with the protein in rape pollen. Chemical and histochemical analyses indicated that protein digestion is closely associated with the diet that a worker bee consumes. Our results demonstrate that camellia pollen has a higher nutritive value than rape pollen for honeybees. By influencing midgut development, different bee diets cause discrepancies in digestive and absorptive functions, which are ultimately reflected by differences in protein digestion.

Digestibility of extruded proteins and metabolic transit of N ε -carboxymethyllysine in rats

Milk proteins are frequently used as supplements in fortified foods. However, processing produces chemical changes which likely affect the nutritional advantage. This study was intended to explore the possible difference in digestibility between extruded and non-extruded caseins and how the dietary N (ε) -carboxymethyllysine (CML) is metabolised. Normal rats were randomized into either an extruded protein diet (EP) or the same with unextruded proteins (UEP), for two periods of 2 weeks at 7 to 9 and 11 to 13 weeks of age. However, no difference in protein digestibility was detected between the two diets, either in young or in adult animals, despite a 9.4-fold higher level of CML and an 8.5-fold higher level of lysinoalanine in the EP than in the UEP. No diet-related changes were observed in plasma CML, either protein bound or free. Amounts of 38 and 48 % of the orally absorbed CML were excreted in urine and faeces, respectively, in UEP-fed rats. Lower rates of excretion were found in the EP-fed rats (23 and 37 %, respectively). A second animal study using a single oral dose of free CML (400 μg/rat) was set up to measure the systemic concentration of CML every hour from 0 to 4 h. It revealed that protein-bound CML was not affected by the oral dose of CML, and the highest free CML level found in the circulation was 600 ng/mL. Extruded proteins, therefore, appear to be well digested, and CML rapidly eliminated. Since its elimination is, however, incomplete, the question of its biodistribution and metabolism remains open.

In vitro digestion of protein sources by crude enzyme extracts of the spiny lobster Panulirus argus (Latreille, 1804) hepatopancreas with different trypsin isoenzyme patterns

The development of cost-effective and nutritionally adequate formulated diets is a key step in the sustainable expansion of spiny lobster aquaculture. Despite proteins are the major and most expensive component of diets, few studies are available on protein digestibility in spiny lobsters and such assessments have never been performed by in vitro methods. Two techniques were used for studying in vitro protein digestion of some common aquafeed ingredients by the spiny lobster Panulirus argus: i) the digestion cell in which the digestion products are removed by dialysis, and ii) electrophoresis which allows the visualization of the different protein fractions in the tested meals. Since three main trypsin isozyme patterns or phenotypes have been recently described in P. argus, the potential differences in protein digestion between individuals with different trypsin isozyme patterns were assessed. Results herein presented demonstrate for the first time in a crustacean species that the different trypsin phenotypes differ in protein digestion efficiency. Also, the digestion cell method was applied for the first time to a crustacea, proving to be sensitive to small changes in digestion efficiency. This method could be used in further in vitro studies for examining other aspects of spiny lobsters digestive process.

Weaned piglets display low gastrointestinal digestion of pea (Pisum sativum L.) lectin and pea albumin 2.

A study was conducted to investigate the biochemistry of digestion of field pea (Pisum sativum L.) albumins and globulins in the stomach and along the small intestine of weaned piglets with a particular emphasis on the respective roles of these compartments in pea protein digestion. Twenty-four piglets were weaned at 28 d of age. They were allocated to 2 diets (control and pea) and 3 slaughter times (3, 6, or 9 h after the last meal) in a 2 x3 factorial arrangement of treatments in a randomized complete block design. Pea flour provided 30% of total dietary protein in the pea diet. The diets were fed for 2 wk after weaning. After slaughter, gastrointestinal tract (GIT) compartments were weighed, digesta were collected, and pH was measured. Digesta from the stomach and cranial, middle, and caudal small intestine (SI) were extracted for soluble proteins and analyzed for specific pea proteins using SDS-PAGE, immunoblotting, and mass spectrometry. Tissue weight of the whole GIT (P = 0.015), cecum (P <0.001), and colon (P <0.001) was greater in the pea diet. Digesta pH in the stomach and caudal SI was lower (P = 0.02) in the pea diet than the control diet. In the stomach, vicilin, lectin, and pea albumin 2 were not digested, whereas legumin was only partly digested. Legumin and vicilin were totally digested in the SI in less than 3 h. A resistant peptide of 15 kDa located at the N-terminus of pea albumin 2 was transiently detected at 3 h. A protein band at 20 kDa was consistently identified as lectin. It was present in high intensity in intestinal digesta of pea-fed piglets at all times after the meal compared with those fed the control diet (P <0.001). Various proteins of, presumably, endogenous origin displayed differential digestion patterns between the control and the pea-fed piglets (P<0.05). In conclusion, differences in digestion between specific pea proteins were observed along the GIT of piglets. They could be partly explained by differences in protein digestion in the stomach.

Partial compensatory growth in hybrid tilapia Oreochromis mossambicus x O. niloticus following food deprivation

The capacity of hybrid tilapia Oreochromis mossambicus x O. niloticus [23.2 +/- 0.2 g (mean +/- SE)] to show compensatory growth was assessed in an 8-week experiment. Fish were deprived of feed for 1, 2 and 4 weeks, and then fed to satiation for 4 weeks; fish fed to satiation during the experiment served as control. Water temperature gradually declined from 28.1 to 25.5 degrees C throughout the experiment. Specific growth rate (SGR) decreased with progressive food deprivation. At the end of deprivation, body weight was lower in the deprived fish than in the control. Fish deprived for 4 weeks exhibited lower contents of lipids and energy in whole body, and higher moisture content and ratio of protein to energy (P/E) than those of the control; they also consumed feed faster than the control when normal feeding was resumed. All deprived fish showed higher food intake (FI) than that of the control during re-alimentation; however, enhanced SGR was only observed in the fish deprived for 4 weeks. There were no significant differences in digestibility of protein and energy, food efficiency (FE) or energy retention efficiency between the control and deprived fish. At the end of re-alimentation, deprived fish failed to catch up in body weight with the control, while content of moisture, lipids and energy, and P/E in whole body of the deprived fish did not significantly differ from that of the control. The results of the experiment revealed that the hybrid tilapia reared in freshwater showed partial capacity for compensatory growth following food deprivation of 4 weeks, and that growth compensation was due mainly to increased FI, rather than to improved FE.

The Protein Digestibility-Corrected Amino Acid Score (PDCAAS)—A Concept for Describing Protein Quality in Foods and Food Ingredients: A Critical Review

Protein Digestibility-Corrected Amino Score (PDCAAS) is discussed. PDCAAS is now widely used as a routine assay for protein quality evaluation, replacing the more traditional biological methods [e.g., measurement of the Protein Efficiency Ratio (PER) in rats]. PDCAAS is based on comparison of the essential amino acid content of a test protein with that of a reference essential amino acid pattern and a correction for differences in protein digestibility as determined using a rat assay. Although PDCAAS is a rapid and useful method, it often shows discrepancies when compared to PER values. These discrepancies relate to the following issues: uncertainty about the validity of reference patterns, invalidity of correction for fecal (versus ileal) digestibility, truncation of PDCAAS values to 100%, failure to obtain full biological response after supplementation of the limiting essential amino acid, discrepancies between protein and amino acid digestibility, effects of processing on protein quality, and effects of the presence of antinutritional factors in the matrix containing the protein. Part of the discrepancy between PDCAAS and PER can be overcome by modifications of PDCAAS. This article describes some proposed modifications and puts forward the suggestion that the rat protein fecal digestibility assay be replaced by an in vitro ileal amino acid digestibility assay based on a computer-controlled gastrointestinal model.

A comparison of the digestibility of a range of lupin and soybean protein products when fed to either Atlantic salmon ( Salmo salar) or rainbow trout ( Oncorhynchus mykiss)

This study compares the digestibility of a series of lupin and soybean protein products when fed to either rainbow trout or Atlantic salmon. The test ingredients in the study, from one of two key grain resources (lupins: Lupinus angustifolius and soybeans), represented various levels of processing of each grain in order to increase the protein content of the meals. A reference ingredient of enzymatically hydrolyzed casein (EHC) was also included in the study. The rainbow trout (266±18 g) were housed in freshwater tanks (250 l, salinity <1‰, 22.1±1.8 °C) and acclimated to the diets for 6 days before faecal collection commenced. The Atlantic salmon (66±10 g) were housed in similar freshwater tanks (250 l, salinity <1‰, 15 °C) and acclimated to the diets for at least 6 days before faecal collection commenced. Faeces were collected from each fish species using settlement collection methods. The digestibility of organic matter, phosphorus, energy and nitrogen was assessed using the diet-substitution method, with each test ingredient included in the diet at 30%. Several differences were observed between the two fish species in their capacity to digest nutrients and energy from each of the products. Organic matter and energy digestibility of each of the ingredients was largely reflective of the protein content of each ingredient. Protein digestibilities were generally consistent between the two fish species with only lupin kernel meal having a significantly higher digestibility when fed to Atlantic salmon than rainbow trout and the soybean protein concentrate a significantly lower digestibility. Although limited differences in protein digestibility were noted among the ingredients when fed to rainbow trout, more substantial differences were noted when the same ingredients were fed to Atlantic salmon. The digestible energy value of the range of products examined was generally higher in Atlantic salmon than rainbow trout. A clear difference between the two fish species was their capacity to digest phosphorus from the ingredients, with several of the plant protein ingredients showing differences in phosphorus digestibility between the two fish species. Generally, both series of grain products have excellent potential as feed ingredients for either of these species. However, the digestive capacity of Atlantic salmon appears to more positively respond to the absence of dietary non-starch polysaccharide content than that of rainbow trout.

Diet Modulates Proteinuria in Heterozygous Female Dogs with X‐Linked Hereditary Nephropathy

Young adult heterozygous (carrier) female dogs with X‐linked hereditary nephropathy (XLHN) have glomerular proteinuria but are otherwise healthy. Because data regarding dietary influences on the magnitude of proteinuria in dogs with spontaneous glomerular disease are not available, 12 such dogs were studied in a double crossover experiment intended to determine effects of altering dietary protein intake for up to 6 weeks. Dogs were blocked by urine protein: creatinine ratio (UPC) and randomly assigned to receive 2 diets: high protein (34.6% dry matter [DM], HP) or low protein (14.1% DM, LP) fed in HP‐LP‐HP or LP‐HP‐LP sequence. Food intake was measured daily, body weight (BW) was measured twice weekly, and UPC, plasma creatinine, blood urea nitrogen, phosphorus, albumin, and protein concentrations were measured at 2‐week intervals. Nutrient digestibility was measured during the third treatment period. Diet had a significant effect (P &lt; .0001) on all measured variables except plasma phosphorus (P &gt; .5), but unintended differences in digestibility of protein and energy (P≤ .01) prevented assignment of the diet effect exclusively to protein. Proteinuria was greater (UPC 4.7 ± 2.2 versus 1.8 ± 1.1, P &lt; .0001) when the HP diet was fed, but the LP diet did not maintain starting BW or plasma albumin concentration within the normal reference range. Diet greatly affects the magnitude of proteinuria in XLHN carrier females. Dietary protein restriction can reduce proteinuria in dogs with glomerular disease, but BW and blood protein concentrations may not be maintained if the restriction is too severe.

Evaluation of Three In Vitro Enzyme Assays for Estimating Protein Digestibility in the Pacific White Shrimp Penaeus vannamei

Abstract— In vitro enzyme assays are rapid, inexpensive techniques for estimating protein digestibility of feed ingredients. Three assays—the Lazo single-enzyme assay with porcine trypsin; the Hsu multi-enzyme assay with porcine trypsin, α-chymotrypsin, and peptidase; and the Satterlee multi-enzyme assay with porcine trypsin, α-chymotrypsin, peptidase, and bacterial protease—were used to estimate relative protein digestibility (RPD) of selected feed ingredients used in diets for the Pacific white shrimp Penaeus vannamei. Ingredients tested were casein, gelatin, rice bran, shrimp meal, soybean meal, wheat gluten, and six varieties of fish meal. A highly significant, inverse, linear relationship existed between final pH in each of the enzyme assays and in vivo apparent protein digestibility of the ingredient in P. vannamei feeding trials. Ranking of RPD coefficients obtained in the Lazo single-enzyme assay followed closely the ranking of published in vivo apparent protein digestibility coefficients for the same ingredients in P. vannamei digestibility trials. Results indicated that a single-enzyme assay with porcine trypsin identified differences in protein digestibility of feedstuffs in vitro as well as the two multi-enzyme assays tested. The porcine-trypsin, single-enzyme assay appears to be a potentially useful tool for evaluating protein quality and relative protein digestibility of feedstuffs for P. vannamei.