Male porcine stifle joint: Insights into osteology and meniscus anatomy for orthopaedic research.

INTRODUCTION: Utilizing large animal model like male pig for biomechanical studies offers a cost-effective approach to understanding human joint and tissue mechanics. Our study explores the osteology and meniscus anatomy of the male porcine stifle joint and compares it to human knee joint parameters, aiming to provide a valuable reference for orthopaedic research and surgical training. METHODS: We examined 60 male porcine stifle joints and analyzed their menisci and bones. Dissections were meticulously performed, with measurements taken using digital Vernier calipers and ImageJ software. These dimensions included bone morphology and meniscal width, height, and volume, followed by statistical analysis using unpaired Student's t-tests. RESULTS: The various measurements of bones and menisci indicated a high degree of anatomical similarity to human knees. The anterior width of the medial meniscus was 12.545 ± 1.763 mm, while the lateral meniscus was 14.99 ± 1.720 mm. The middle width of the medial meniscus was 12.065 ± 1.691 mm, compared to the lateral meniscus at 14.375 ± 1.732 mm. The posterior width was 15.25 ± 1.741 mm for the medial meniscus and 16.39 ± 1.662 mm for the lateral meniscus. The femoral intercondylar notch dimensions widened and became shallower with age, resembling the maturation patterns seen in human knee development. The average volume of the medial meniscus was 4.30 ± 0.13 ml, while the lateral meniscus was 5.9 ± 0.29 ml. The aspect ratio of the femoral condyles was 1.04 ± 0.04 (0.95-1.11), while the aspect ratio of the tibial condyles was 0.65 ± 0.02 (0.61-0.70), measured via digital Vernier calipers. These findings were statistically significant, showcasing the male porcine model's relevance in replicating human knee mechanics (p < 0.05). CONCLUSION: Male porcine stifle joints present a valid and accessible model for knee anatomy research. Our study underscores the value of the male porcine model in understanding human knee joint biomechanics and supports its continued use in orthopaedic research and training. These findings have significant implications for advancing orthopaedic research methodologies and enhancing surgical training practices by providing a reliable and anatomically comparable model.

Identifying therapeutic monoclonal antibodies using target protein collision electrophoresis reflex assay to separate the wheat from the chaff.

Monoclonal gammopathies are characterized by the presence of monoclonal immunoglobulins, also known as M-proteins. Therapeutic monoclonal antibodies (t-mAbs) can interfere in laboratory assays used to monitor the state of disease, such as serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE). To establish a correct interpretation of IFE, Target protein-Collision Immunofixation Electrophoresis Reflex Assay (T-CIERA) was developed to identify t-mAbs in IFE. Here we demonstrate that T-CIERA is applicable to a wide variety of t-mAbs for which the target protein is commercially available. Moreover, the shift observed was characteristic for each t-mAb, and T-CIERA enabled the identification of multiple t-mAbs sharing a common target protein. Additionally, the lower limit of detection (LLOD) was determined objectively, and T-CIERA demonstrated an adequate LLOD for all tested t-mAbs. Furthermore, T-CIERA was also successfully applied to serum samples obtained from patients receiving daratumumab, isatuximab, elotuzumab, and durvalumab treatment. In conclusion, T-CIERA is a suitable reflex assay for identifying a wide variety of t-mAbs, including those for which no commercial assay is available to deal with their interference. Moreover, CD38-CIERA could serve as an alternative or complementary test to the commercially available Hydrashift assay kits. T-CIERA would enable laboratories without mass spectrometry equipment and expertise in this area to distinguish between drug and disease to improve clinical response monitoring and diagnosis of monoclonal gammopathies.

Treatment of decentered developmental dysplasia of the hip under the age of 1 year: an evidence-based clinical practice guideline - Part 2.

Background and purpose: Diagnostics and treatment of developmental dysplasia of the hip (DDH) are highly variable in clinical practice. To obtain more uniform and evidence-based treatment pathways, we developed the 'Dutch guideline for DDH in children < 1 year'. This study describes recommendations for unstable and decentered hips. Materials and methods: The Appraisal of Guidelines for Research and Evaluation criteria (AGREE II) were applied. A systematic literature review was performed for six predefined guideline questions. Recommendations were developed, based on literature findings, as well as harms/benefits, patient/parent preferences, and costs (GRADE). Results: The systematic literature search resulted in 843 articles and 11 were included. Final guideline recommendations are (i) Pavlik harness is the preferred first step in the treatment of (sub) luxated hips; (ii) follow-up with ultrasound at 3-4 and 6-8 weeks; (iii) if no centered and stable hip after 6-8 weeks is present, closed reduction is indicated; (iv) if reduction is restricted by limited hip abduction, adductor tenotomy is indicated; (v) in case of open reduction, the anterior, anterolateral, or medial approach is advised, with the choice based on surgical preference and experience; (vi) after reduction (closed/open), a spica cast is advised for 12 weeks, followed by an abduction device in case of residual dysplasia. Interpretation: This study presents recommendations on the treatment of decentered DDH, based on the available literature and expert consensus, as Part 2 of the first official and national evidence-based 'Guideline for DDH in children < 1 year'. Part 1 describes the guideline sections on centered DDH in a separate article.

Treatment of centered developmental dysplasia of the hip under the age of 1 year: an evidence-based clinical practice guideline - Part 1.

Despite the high incidence of developmental dysplasia of the hip (DDH), treatment is very diverse. Therefore, the Dutch Orthopedic Society developed a clinical practice guideline with recommendations for optimal and uniform treatment of DDH. This article summarizes the guideline on centered DDH (i.e. Graf types 2A-C). The guideline development followed the criteria of Appraisal of Guidelines for Research and Evaluation II. A systematic literature review was performed to identify randomized controlled trials and comparative cohort studies including children <1 year with centered DDH. Articles were included that compared (1) treatment with observation, (2) different abduction devices, (3) follow-up frequencies, and (4) discontinuation methods. Recommendations were based on Grading Recommendations Assessment, Development, and Evaluation, which included the literature, clinical experience and consensus, patient and parent comfort, and costs. Out of 430 potentially relevant articles, 5 comparative studies were included. Final guideline recommendations were (1) initially observe 3-month-old patients with centered DDH, start abduction treatment if the hip does not normalize after 6-12 weeks; (2) prescribe a Pavlik harness to children <6 months with persisting DDH on repeated ultrasonography, consider alternative abduction devices for children >6 months; (3) assess patients every 6 weeks; and (4) discontinue the abduction device when the hip has normalized or when the child is 12 months. This paper presents a summary of part 1 of the first evidence-based guideline for treatment of centered DDH in children <1 year. Part 2 presents the guideline on decentered DDH in a separate article.

Which patient-specific and surgical characteristics influence postoperative pain after THA in a fast-track setting?

BACKGROUND: In our hospital a fast-track setting including a multimodal pain protocol is used for total hip arthroplasty (THA). Despite this multimodal pain protocol there is still a large range in reported postoperative pain between patients, which hinders mobilization and rehabilitation postoperatively. The goal of this study was to identify which patient-specific and surgical characteristics influence postoperative pain after THA in a fast-track setting. METHODS: All 74 patients with osteoarthritis of the hip who underwent primary THA procedure by anterior supine intermuscular approach between November 2012 and January 2014 were included in this prospective cohort study. The protocol for pain medication was standardized. Postoperative pain determined with the Numeric Rating Score was collected at 17 standardized moments. Linear mixed models were used to examine potential patient-specific and surgical factors associated with increased postoperative pain. RESULTS: Pain patterns differed substantially across individuals. Adjusted for other variables in the model, preoperative use of pain medication (regression coefficient 0.78 (95% CI 0.28-1.26); p = 0.005) and preoperative neuropathic pain scored by DN4 (regression coefficient 0.68 (95% CI 0.15-1.20); p = 0.02) were the only factors significantly associated with higher postoperative pain scores. CONCLUSIONS: The knowledge of which factors are associated with higher postoperative pain scores after THA in a fast-track setting may help optimizing perioperative postoperative pain management and preoperative education of these patients. TRIAL REGISTRATION: The study was retrospectively registered in the ISRCTN registry under identifier ISRCTN15422220 (date of registration: July 25, 2017).

The less invasive anterior approach for total hip arthroplasty: a comparison to other approaches and an evaluation of the learning curve - a systematic review.

There is still discussion about possible advantages and disadvantages of the less invasive anterior approach for total hip arthroplasty (THA). The purpose of our systematic review was to evaluate literature regarding the anterior approach in comparison to other approaches. Furthermore, we investigated if there is a description of a learning curve for the anterior approach.Data were obtained from EMBASE, Cochrane, PsycINFO, CINAHL, Web-of-Science, Scopus, Google scholar, and PubMed since their inception up to June 2015. 2 reviewers independently selected the studies and independently conducted the quality assessment. Because studies were considered heterogeneous regarding outcome measures, determinants studied, and methodological quality, we decided to perform a "best evidence synthesis". A total of 64 studies met the inclusion criteria.Strong evidence for no difference in component placement between the anterior approach and other approaches was found. Also, strong evidence for faster postoperative recovery and less need for assistive devices after the anterior approach were found. All other studied parameters only demonstrated conflicting evidence. Although the learning curve for the anterior approach is not yet clear, this learning curve should not to be neglected.In conclusion, the less invasive anterior approach provides benefits in the early postoperative period only, when compared to other approaches.

Total hip arthroplasty in an outpatient setting in 27 selected patients.

BACKGROUND AND PURPOSE: As a result of introduction of a fast-track program, length of hospital stay after total hip arthroplasty (THA) decreased in our hospital. We therefore wondered whether THA in an outpatient setting would be feasible. We report our experience with THA in an outpatient setting. PATIENTS AND METHODS: In this prospective cohort study, we included 27 patients who were selected to receive primary THA in an outpatient setting between April and July 2014. Different patient-reported outcome measures (PROMs) were recorded preoperatively and at 6 weeks and 3 months postoperatively. Furthermore, anchor questions on how patients functioned in daily living were scored at 6 weeks and 3 months postoperatively. RESULTS: 3 of the 27 patients did not go home on the day of surgery because of nausea and/or dizziness. The remaining 24 patients all went home on the day of surgery. PROMs improved substantially in these patients. Moreover, anchor questions on how patients functioned in their daily living indicated that the patients were satisfied with the postoperative results. 1 re-admission occurred at 11 days after surgery because of seroma formation. There were no other complications or reoperations. INTERPRETATION: At our hospital, with a fast-track protocol, outpatient THA was found to be feasible in selected patients with satisfying results up to 3 months postoperatively, without any outpatient procedure-specific complications or re-admissions.

The anterior supine intermuscular approach for total hip arthroplasty: reducing the complication rate by improving the procedure.

This study describes specific complications noticed during the first unselected cases operated by anterior approach for THA in our hospital and specific adjustments that were applied on the procedure to prevent these complications. We retrospectively analysed the differences between 202 patients who were operated by a standardised approach and 248 patients who were operated after adjustments were implemented with the procedure. Injury to the lateral femoral cutaneous nerve (LFCN), fractures of the greater trochanter and dislocation were specific complications that were noticed with the initial technique.Prevalence of injury to the LFCN decreased from 7.9% to 0.8% (p<0.001), fractures of the greater trochanter decreased from 5.4% to 0.8% (p = 0.004) and the incidence of dislocation decreased from 4.5% to 1.6% (p = 0.074).

Reduced length of hospital stay after the introduction of a rapid recovery protocol for primary THA procedures.

BACKGROUND AND PURPOSE: Rapid recovery protocols after total hip arthroplasty (THA) have been introduced worldwide in the last few years and they have reduced the length of hospital stay. We show the results of the introduction of a rapid recovery protocol for primary THA for unselected patients in our large teaching hospital. PATIENTS AND METHODS: In a retrospective cohort study, we included all 1,180 patients who underwent a primary THA between July 1, 2008 and June 30, 2012. These patients were divided into 3 groups: patients operated before, during, and after the introduction of the rapid recovery protocol. There were no exclusion criteria. All complications, re-admissions, and reoperations were registered and analyzed. RESULTS: The mean length of hospital stay decreased from 4.6 to 2.9 nights after the introduction of the rapid recovery protocol. There were no statistically significant differences in the rate of complications, re-admissions, or reoperations between the 3 groups. INTERPRETATION: In a large teaching hospital, the length of hospital stay decreased after introduction of our protocol for rapid recovery after THA in unselected patients, without any increase in complications, re-admissions, or reoperation rate.

Formation of diacetyl and acetoin by Lactococcus lactis via aspartate catabolism.

AIMS: To verify whether diacetyl can be produced by Lactococcus lactis via amino acid catabolism, and to investigate the impact of the pH on the conversion. METHODS AND RESULTS: Resting cells of L. lactis were incubated in reaction media at different pH values, containing L-aspartic acid or L-alanine as a substrate. After incubation, the amino acid and metabolites were analysed by HPLC and GC/MS. At pH 5 about 75% of aspartic acid and only 40% of alanine was degraded to pyruvate via a transamination step that requires the presence of alpha-ketoglutarate in the medium, but diacetyl was only produced from aspartic acid. Three per cent of pyruvate was transformed to acetolactate of which 50% was converted into diacetyl. At pH 5 x 5 and above the pyruvate conversion into acetolactate was less efficient than at pH 5, and acetolactate was mainly decarboxylated to acetoin. CONCLUSIONS: Acetoin and diacetyl can be formed as a result of aspartate or alanine catabolism by L. lactis in the presence of alpha-ketoglutarate in the medium. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactic acid bacteria exhibiting both glutamate dehydrogenase activity and high aspartate aminotransferase activity are expected to be good diacetyl producers during cheese ripening at pH close to 5.

Addition of oxidizing or reducing agents to the reaction medium influences amino acid conversion to aroma compounds by Lactococcus lactis.

AIMS: The aim of this research was to investigate the impact of extracellular redox potential (Eh) on amino acid conversion to aroma compounds by Lactococcus lactis that is commonly used as a starter in the cheese industry. METHODS AND RESULTS: The study was realized in vitro by incubating resting cells of L. lactis in reaction media in which E(h) was modified by the addition of oxidizing or reducing agents. Oxidative condition (+300 mV) favoured the production of aldehydes and volatile sulfur compounds responsible for malty, floral, fruity, almond and cabbage aroma. This production was mainly the result of a chemical oxidation of the alpha-keto acids produced by amino acid transamination. In contrast, reducing condition (-200 mV) stimulated the production of carboxylic acids such as phenylacetic, methylthiopropionic and isovaleric acids, which contribute to the very-ripened-cheese aroma as well as the production of hydroxy acids. CONCLUSIONS: Eh of the medium highly influences the nature of aroma compounds produced from amino acid catabolism by the resting cells of L. lactis. SIGNIFICANCE AND IMPACT OF THE STUDY: E(h) is a parameter that is not controlled during cheese production. Its control throughout cheese making and ripening could permit control of aroma formation in cheese.

Sulfur compound production by Geotrichum candidum from L-methionine: importance of the transamination step.

L-methionine degradation products and catabolic enzymatic activities involved in methanethiol generation were investigated in Geotrichum candidum GcG. L-methionine was easily degraded by G. candidum and the transamination product, 4-methylthio-2-oxobutyric acid (KMBA), was found to transiently accumulate. In parallel, considerable L-methionine aminotransferase activity was found in this microorganism. L-methionine and KMBA demethiolating activities were also detected. The degradation of KMBA corresponded to an overall increase in the production of volatile sulfur compounds. These results show that the transamination pathway is of major importance in the initial breakdown of L-methionine by this cheese-ripening microorganism.

L-methionine degradation potentialities of cheese-ripening microorganisms.

Volatile sulphur compounds are major flavouring compounds in many traditional fermented foods including cheeses. These compounds are products of the catabolism of L-methionine by cheese-ripening microorganisms. The diversity of L-methionine degradation by such microorganisms, however, remains to be characterized. The objective of this work was to compare the capacities to produce volatile sulphur compounds by five yeasts, Geotrichum candidum, Yarrowia lipolytica, Kluyveromyces lactis, Debaryomyces hansenii, Saccharomyces cerevisiae and five bacteria, Brevibacterium linens, Corynebacterium glutamicum, Arthrobacter sp., Micrococcus lutens and Staphylococcus equorum of technological interest for cheese-ripening. The ability of whole cells of these microorganisms to generate volatile sulphur compounds from L-methionine was compared. The microorganisms produced a wide spectrum of sulphur compounds including methanethiol, dimethylsulfide, dimethyldisulfide, dimethyltrisulfide and also S-methylthioesters, which varied in amount and type according to strain. Most of the yeasts produced methanethiol, dimethylsulfide, dimethyldisulfide and dimethyltrisulfide but did not produce S-methylthioesters, apart from G. candidum that produced S-methyl thioacetate. Bacteria, especially Arth. sp. and Brevi. linens, produced the highest amounts and the greatest variety of volatile sulphur compounds includling methanethiol, sulfides and S-methylthioesters, e.g. S-methyl thioacetate, S-methyl thiobutyrate, S-methyl thiopropionate and S-methyl thioisovalerate. Cell-free extracts of all the yeasts and bacteria were examined for the activity of enzymes possibly involved in L-methionine catabolism, i.e. L-methionine demethiolase, L-methionine aminotransferase and L-methionine deaminase. They all possessed L-methionine demethiolase activity, while some (K. lactis, Deb. hansenii, Arth. sp., Staph. equorum) were deficient in L-methionine aminotransferase, and none produced L-methionine deaminase. The catabolism of L-methionine in these microorganisms is discussed.

Expression of a heterologous glutamate dehydrogenase gene in Lactococcus lactis highly improves the conversion of amino acids to aroma compounds.

The first step of amino acid degradation in lactococci is a transamination, which requires an alpha-keto acid as the amino group acceptor. We have previously shown that the level of available alpha-keto acid in semihard cheese is the first limiting factor for conversion of amino acids to aroma compounds, since aroma formation is greatly enhanced by adding alpha-ketoglutarate to cheese curd. In this study we introduced a heterologous catabolic glutamate dehydrogenase (GDH) gene into Lactococcus lactis so that this organism could produce alpha-ketoglutarate from glutamate, which is present at high levels in cheese. Then we evaluated the impact of GDH activity on amino acid conversion in in vitro tests and in a cheese model by using radiolabeled amino acids as tracers. The GDH-producing lactococcal strain degraded amino acids without added alpha-ketoglutarate to the same extent that the wild-type strain degraded amino acids with added alpha-ketoglutarate. Interestingly, the GDH-producing lactococcal strain produced a higher proportion of carboxylic acids, which are major aroma compounds. Our results demonstrated that a GDH-producing lactococcal strain could be used instead of adding alpha-ketoglutarate to improve aroma development in cheese.

Characterization and role of the branched-chain aminotransferase (BcaT) isolated from Lactococcus lactis subsp. cremoris NCDO 763.

In Lactococcus lactis, which is widely used as a starter in the cheese industry, the first step of aromatic and branched-chain amino acid degradation is a transamination which is catalyzed by two major aminotransferases. We have previously purified and characterized biochemically and genetically the aromatic aminotransferase, AraT. In the present study, we purified and studied the second enzyme, the branched-chain aminotransferase, BcaT. We cloned and sequenced the corresponding gene and used a mutant, along with the luciferase gene as the reporter, to study the role of the enzyme in amino acid metabolism and to reveal the regulation of gene transcription. BcaT catalyzes transamination of the three branched-chain amino acids and methionine and belongs to class IV of the pyridoxal 5'-phosphate-dependent aminotransferases. In contrast to most of the previously described bacterial BcaTs, which are hexameric, this enzyme is homodimeric. It is responsible for 90% of the total isoleucine and valine aminotransferase activity of the cell and for 50 and 40% of the activity towards leucine and methionine, respectively. The original role of BcaT was probably biosynthetic since expression of its gene was repressed by free amino acids and especially by isoleucine. However, in dairy strains, which are auxotrophic for branched-chain amino acids, BcaT functions only as a catabolic enzyme that initiates the conversion of major aroma precursors. Since this enzyme is still active under cheese-ripening conditions, it certainly plays a major role in cheese flavor development.

Genetic characterization of the major lactococcal aromatic aminotransferase and its involvement in conversion of amino acids to aroma compounds.

In lactococci, transamination is the first step of the enzymatic conversion of aromatic and branched-chain amino acids to aroma compounds. In previous work we purified and biochemically characterized the major aromatic aminotransferase (AraT) of a Lactococcus lactis subsp. cremoris strain. Here we characterized the corresponding gene and evaluated the role of AraT in the biosynthesis of amino acids and in the conversion of amino acids to aroma compounds. Amino acid sequence homologies with other aminotransferases showed that the enzyme belongs to a new subclass of the aminotransferase I subfamily gamma; AraT is the best-characterized representative of this new aromatic-amino-acid-specific subclass. We demonstrated that AraT plays a major role in the conversion of aromatic amino acids to aroma compounds, since gene inactivation almost completely prevented the degradation of these amino acids. It is also highly involved in methionine and leucine conversion. AraT also has a major physiological role in the biosynthesis of phenylalanine and tyrosine, since gene inactivation weakly slowed down growth on medium without phenylalanine and highly affected growth on every medium without tyrosine. However, another biosynthesis aromatic aminotransferase is induced in the absence of phenylalanine in the culture medium.

Allergy to bovine beta-lactoglobulin: specificity of human IgE using cyanogen bromide-derived peptides.

BACKGROUND: Bovine beta-Lactoglobulin (Blg) is a major allergen involved in allergy to cow's milk proteins. Hydrolyzing Blg did not totally suppress its allergenicity; moreover its immunoreactivity may be increased. The aim of this work was to evaluate the specificity of serum IgE to different fragments of Blg in a group of 19 individuals allergic to cow's milk. METHODS: This study was performed using both direct and competitive inhibition ELISA involving immobilized native protein or peptides derived from Blg cyanogen bromide cleavage. RESULTS: Analyses of responses to each peptide revealed a large number of epitopes recognized by specific IgE of human allergic sera. However, there were differences in the specific determinants recognized, depending on the serum. Generally, peptides (25-107) and (108-145) retained substantial proportions of the immunoreactivity of the whole protein. Two other peptides, i.e. (8-24) and (146-162), were less recognized but were not inert. CONCLUSION: The main conclusion is that many epitopes were identified all along the Blg sequence by specific anti-Blg IgE from allergic humans.

Specificity of the human IgE response to the different purified caseins in allergy to cow's milk proteins.

BACKGROUND: Cow's milk is one of the most frequent food allergens. Whole casein appears to be highly allergenic. It corresponds to an association of four different proteins, alpha(s1)-, alpha(s2)-, beta- and kappa-caseins in approximate proportions of 40, 10, 40, and 10%, respectively. METHODS: These different components were thus purified and used as immobilized antigens in an original enzyme immunoassay to measure specific serum IgE response in a population of 58 children (median age 11 months) allergic to cow's milk who were sensitive to whole casein. RESULTS: A great variability was observed in the affinity and specificity of specific IgE responses in milk-allergic patients' sera. 85% of the patients presented IgE against each of the four caseins. Statistically higher amounts of specific IgE were found to be directed against the most abundant fractions (alpha[s1]- and beta-casein). Co- and/or cross-sensitization to the different caseins were seen in most of the patients sensitive to whole casein. CONCLUSION: These results suggest that both distinct and common epitopes may occur on these different caseins. The major site of phosphorylation which is the most conserved domain in three caseins could be involved in the IgE response to casein and in immunocross-reactivity between these proteins.

An aminotransferase from Lactococcus lactis initiates conversion of amino acids to cheese flavor compounds.

The enzymatic degradation of amino acids in cheese is believed to generate aroma compounds and therefore to be involved in the complex process of cheese flavor development. In lactococci, transamination is the first step in the degradation of aromatic and branched-chain amino acids which are precursors of aroma compounds. Here, the major aromatic amino acid aminotransferase of a Lactococcus lactis subsp. cremoris strain was purified and characterized. The enzyme transaminates the aromatic amino acids, leucine, and methionine. It uses the ketoacids corresponding to these amino acids and alpha-ketoglutarate as amino group acceptors. In contrast to most bacterial aromatic aminotransferases, it does not act on aspartate and does not use oxaloacetate as second substrate. It is essential for the transformation of aromatic amino acids to flavor compounds. It is a pyridoxal 5'-phosphate-dependent enzyme and is composed of two identical subunits of 43.5 kDa. The activity of the enzyme is optimal between pH 6.5 and 8 and between 35 and 45 degrees C, but it is still active under cheese-ripening conditions.

In vivo and in vitro gastric emptying of milk replacers containing soybean proteins.

Gastric digestion of three milk replacers for which protein was provided either exclusively by milk powder or partially (50%) by heated soybean flour or soybean protein concentrate was studied in vivo and in vitro. In vivo gastric emptying of protein fractions of the diets was measured in six preruminant calves fitted with reentrant duodenal cannulas and used in a double 3 x 3 Latin square design. In vitro gastric emptying was studied after hydrochloric acid and rennet digestion in an artificial stomach. In vivo and in vitro flow rates of 12% TCA-insoluble N and total N were higher for the soybean diets than for the milk protein diet, indicating that the incorporation of soybean protein prevented casein from clotting. Because of this faster gastric emptying, proteolysis in the stomach was reduced. However, gastric emptying of NPN (12% TCA-soluble N) was significantly decreased only in vitro. No difference existed between the two milk replacers containing either soybean flour or soybean protein concentrate. In vivo and in vitro results were correlated, suggesting that the in vitro method could be used to predict gastric digestion of protein fractions in vivo.