Low Trypsin Inhibitor Research Articles

Effects of heat treatment on the nutritional value of raw soybean selected for low trypsin inhibitor activity

1. Two broiler experimentss and a layer experiments were conducted on Kunitz trypsin inhibitor (Kti) soybeans (SB) of low trypsin inhibitor (TI) activity to determine their nutritive value when included as mash in least-cost poultry diets. 2. Experiment 1 compared chick performance on the Kti or raw SB using a commercial full-fat SB meal (FFSBM) and a solvent extracted SB meal (SBM) as controls during a 20 d experimental period. Broiler experiment 2 compared Kti and raw SB, non-steamed, or steam-pelleted with and without DL-methionine supplementation added to every treatment containing 170 g SB/kg. For each broiler experiment the levels of each SB were 70, 120 and 170 g/kg with the control birds fed only 170 g SB/kg. 3. The layer experiment, compared steam-pelleted Kti and raw SB against a non-steamed Kti and raw SB each fed at two levels (70 and 110 g/kg) × 30 replicates from 29 weeks of age for 19 weeks in a completely randomised design. Production parameters were measured when diets were formulated to contain minimum required specifications and calculated apparent metabolisable energy (AME). At the completion of each trial, 2 broiler birds from each cage and 5 layer birds per treatment were killed, weighed, and their liver and pancreas weighed. 4. Both broiler experiments indicated that production parameters on the Kti SB treatments were significantly lower (P < 0·05) than on the two commercial control SB treatments. However, the Kti treatments were superior to the raw SB treatments. 5. Pancreas weight increased with increasing inclusion of both raw and Kti SB, suggesting that a TI was causing the depression in performance. The AME of the Kti SB was similar to that of commercial FFSB meal. After steam conditioning, the raw SB meal AME value of 9·5 MJ/kg dry matter (DM) was improved to 14·1 MJ/kg DM by reduced TI activity, but this AME improvement with TI activity reduction, plus the supplementation with dl-methionine on birds fed the raw SB had no effect (P > 0·05) on any parameter evaluated in experiment 2. 6. The layer experiment showed that hens on the Kti SB treatments had significantly greater live weight gain (LWG), egg weight and daily egg mass than birds given raw SB. A reduced food intake (FI) was observed in the Kti treatments but egg mass was generally similar to that on the FFSB control diet, indicating that Kti SB supported excellent egg production at an inclusion of 110 g/kg. The depressed performance observed for broiler chicks suggest that younger birds are more susceptible to the effects of SB TI.

Degradabilidade ruminal in situ da matéria seca e proteína bruta de duas variedades de grão de soja com diferentes teores de inibidor de tripsina, em bovinos

Foram utilizados quatro bovinos da raça holandesa canulados no rúmen, distribuídos em blocos, ao acaso, alimentados a pasto de coast-cross (Cynodon dactylon). Os animais foram suplementados com ração concentrada contendo grãos de soja moídos colocados no rúmen, às sete e às dezoito horas. Em todos os animais foram incubados sacos de náilon com amostras de cada tratamento: grãos de soja comercial moídos (S), grãos de soja comercial moídos e parcialmente desengordurados (SD), grãos de soja com baixo inibidor de tripsina moídos (SBIT); grãos de soja com baixo inibidor de tripsina moídos e parcialmente desengordurados (SBITD); e farelo de soja (FS). Determinaram-se os desaparecimentos no rúmen da matéria seca (MS), matéria orgânica (MO) e proteína bruta (PB) nos tempos de 6, 24 e 48 horas. As solubilidades da MS, MO e da PB do S foram superiores às determinadas para o SBIT. A degradabilidade potencial (DP) apresentou valores semelhantes entre os alimentos. A degradabilidade efetiva (DE) da MS e MO dos SBS foi 9% menor que os valores observados para S e a DE da PB do SBIT foi aproximadamente 6% menor. Todos os alimentos apresentaram altas velocidades de degradação dos componentes estudados, variando de 5%/hora para o FS a 15%/hora para SBITD, enquanto os SBIT apresentaram menor taxa de degradação. Estes valores sugerem que estes alimentos devem ser associados a outros com menores velocidades de fermentação nas rações de ruminantes, para que haja melhor sincronismo entre liberação de amônia, aminoácido, peptídeos e cetoácidos no rúmen, quando for necessário maximizar a produção de proteína microbiana e/ou aumentar a quantidade de proteína bypass.

Proteinase inhibitor polymorphism in the genus Vigna subgenus Ceratotropis and its biosystematic implications

The diversity of components for fourproteinase inhibitors found in species ofthe genus Vigna subgenus Ceratotropis are described. Trypsin,chymotrypsin, subtilisin and cysteineproteinase inhibitors were analyzedby isoelectric focusing followed by thegelatin replica method. Of these proteinaseinhibitors, trypsin inhibitors showedmost polymorphism both within and betweenspecies. Many trypsin inhibitor componentswere also active to chymotrypsin. Severalaccessions had very low levels or absenceof some inhibitors, such as very low levelsof trypsin inhibitor in two accessions ofthe V. tenuicaulis and absence ofchymotrypsin inhibitors in V.grandiflora and V. subramaniana.Proteinase inhibitor polymorphism broadlyagreed with the taxonomic system for thesubgenus Ceratotropis. Based oninhibitor variation species analyzed couldbe divided into three groups whichcorresponding to sections Aconitifoliae, Angulares and Ceratotropis. Some species have verylittle variation in trypsin inhibitorsdespite wide distribution, such as, V.radiata and V. reflexo-pilosa.Accessions of other species showedconsiderable intraspecific variation fortrypsin inhibitors, such as, V.grandiflora, V. aconitifolia andV. stipulacea. Proteinase inhibitorpolymorphism provides an indication of thespecies that may have contributed a genometo the tetraploid species, V. reflexo-pilosa.

Avaliação biológica de linhagem de soja com baixa atividade de inibidores de tripsina

Cultivar de soja BR 36 com atividades de inibidores de tripsina convencional e linhagem de soja BRM 95-5262 geneticamente modificadas para conter baixas atividades de inibidores de tripsina foram utilizados em ensaios biológicos com aves contendo 40 e 20% e 30 e 20% de atividades residuais relativa de inibidores de tripsina, respectivamente. Os valores médios de PER, NPR e CA indicaram que os tratamentos de soja crua foram inferiores aos tratamentos de soja processados termicamente. Entretanto, tratamentos de soja processados termicamente com inativação de 20% de atividades residuais relativa de inibidores de tripsina não apresentaram diferenças significativas entre si e em relação ao padrão farelo de soja. Porém, quando as atividades de inibidores de tripsina final foram de 8,61 e 8,44 UIT/mg de amostra ou 20 e 30% de atividades residuais relativa dos respectivos cultivar BR 36 e linhagem BRM 95-5262, observou-se que os valores médios de PER, NPR e CA não foram significativos. Concluiu-se que os valores de PER, NPR e CA obtidos com a proteína de soja foram dependentes das atividades iniciais de inibidores de tripsina e do seu respectivo tratamento térmico e que há vantagem na utilização da soja BRM 95-5262 com baixas atividades de inibidores de tripsina.

Diversity in seed quality traits of common bean populations from Basilicata (Southern Italy)

AbstractThe diversity of nutritional and culinary traits in 21 populations of common bean from the Basilicata region was studied for three consecutive harvests (1995‐97). The results were compared with the six commercial cultivars widely grown in the region. Some populations deserve particular attention since they had large seeds, high protein content, low trypsin inhibitor levels and short cooking time. The cluster analysis showed that 18 populations clustered in two main groups and that the bush populations were clearly distinguishable from the climbing ones. When phaseolin type and some plant morphological traits were added to the nutritional and culinary traits to classify these populations, it was observed that they resembled the race Peru (Andean gene pool).

Developments in plant breeding for improved nutritional quality of soya beans II. Anti-nutritional factors

Nutritional value of most plant materials is limited by the presence of numerous naturally occurring compounds which interfere with nutrient digestion and absorption. Although processing is employed widely in removal of these factors, selection of cultivars of soya beans with inherently low levels would have a considerable impact on efficiency of non-ruminant livestock production. The review considers the role of plant breeding in achieving this objective. The most abundant trypsin inhibitors are the Kunitz and the Bowman–Birk inhibitors, containing 181 and 71 amino acids respectively. The Kunitz inhibitor is present at a concentration of 1·4 g/kg of total seed contents and the Bowman–Birk inhibitor 1·6 g/kg. A large number of isoforms of the Bowman–Birk inhibitor have been described in soya bean cultivars and it has been shown that the general properties of the inhibitor are, in fact, attributable to different isoforms. Nulls for both Bowman–Birk and Kunitz trypsin inhibitors have been identified, allowing new low trypsin inhibitor cultivars to be produced. However, research into breeding for low trypsin inhibitor cultivars currently has limited application as trypsin inhibitors contribute a major proportion of the methionine content of soya beans. Trypsin inhibitors are thought to be involved in the regulation of and protection against unwanted proteolysis in plant tissues and also act as a defence mechanism against attack from diseases, insects and animals. Hence, in breeding programmes for low trypsin inhibitor cultivars, alternative protection for growing plants must be considered. Use of soya beans in non-ruminant animal feeds is limited by the flatulence associated with their consumption. The principal causes appear to be the low molecular weight oligosaccharides containing α-galactosidic and β-fructosidic linkages; raffinose and stachyose. Non-ruminants do not have the α-galactosidase enzyme necessary for hydrolysing the α-galactosidic linkages of raffinose and stachyose to yield readily absorbable sugars. Soya beans contain between 6·8 and 17·5 g of phytic acid/kg; a ring form of phosphorus (P) which chelates with proteins and minerals to form phytates not readily digested within the gut of non-ruminants. One approach for over-coming the effects of phytic acid is through synthesis of phytase in the seeds of transgenic plants. Currently, recombinant phytase produced in soya beans is not able to withstand the processing temperatures necessary to inactivate proteinaceous anti-nutritional factors present. Soya bean lectins have the ability to bind with certain carbohydrate molecules (N-acetyl-D-galactosamine and galactose) without altering the covalent structure. Lectins are present in raw soya bean at a concentration of between 10 and 20 g/kg. Purified soya bean agglutinin is easily inactivated by hydrothermal treatment but in complex diets binding with haptenic carbohydrates may confer protection against denaturation. The majority of research into soya bean lectins is carried out using laboratory animals so very limited information is available on their in vivo effects in farm animals. This review is concerned specifically with breeding but there are other means of improving nutritive value, for example processing which may alter protein structure and therefore functionality of proteinaceous anti-nutritional factors present.

Effects of ileal endogenous nitrogen losses and dietary amino acid supplementation on nitrogen retention in growing pigs

The relationship between ileal endogenous nitrogen (N) losses and N retention was studied in two experiments with growing pigs of 40 to 60 kg. In Experiment 1, 13 ileal cannulated castrated males were fed diets based on maize starch, containing either soyabean meal (SBM) with a low trypsin inhibitor activity (TIA), a mixture of toasted and untoasted soyabean meal with a high TIA (mSBM), a commercial batch of peas, or rapeseed expeller cake (RC). Ileal endogenous N recovery was measured using the 15N-isotope dilution technique. Apparent ileal digestibility of crude protein (CP) for the SBM, mSBM, pea and RC diets were 82.8, 72.0, 76.7 and 68.7% ( P < 0.05). True ileal CP digestibility for the diets was 96.5, 93.0, 94.0 and 87.5% ( P < 0.05), and the recovery of ileal endogenous N was 3.08, 6.01, 4.55 and 5.36 g/kg DMI ( P < 0.05). In Experiment 2, sixteen castrated males were used to determine N retention, using almost similar diets as in Experiment 1. The diets contained either SBM, mSBM or peas and were balanced for the contents of apparent ileal digestible (ID) CP (96 g/kg) and ID essential amino acids (EAA; at least 85% of requirement values). The fourth treatment was a diet with mSBM as protein source, but supplemented with EAA to the level of 95% of the requirement values (diet mSBMs). Apparent faecal CP digestibility for the SBM, mSBM, pea and mSBMs diets was 88.6, 87.2, 86.1 and 86.0% ( P < 0.05). Urinary N excretion and N retention for these treatments were 0.39, 0.59, 0.40, 0.53 ( P < 0.05) and 0.87, 0.80, 0.85, 0.84 g/kg 0.75/day ( P < 0.05), respectively. Utilization of dietary ID N for N retention were 79.8, 73.3, 78.2 and 77.6% ( P < 0.05), respectively. The study showed that increased ileal endogenous N losses are associated with higher losses of urinary N and with a lower N retention. Supplementation of extra essential AA to a diet causing a relatively high flow of ileal endogenous N, may compensate for the lower N utilization under these conditions, and thus limit effects on N retention.

Feeding value of pea (Pisum sativum, L.) 2. Nutritional value in the pig

AbstractNineteen round white-feed peas (FP) varieties, six coloured-flowered peas (CP) varieties and four wrinkled white-flowered peas (WP) varieties were given to growing pigs in order to measure their feeding value. Mean values of energy apparent digestibility measured at the faecal level of FP, CP and WP were respectively 0·886, 0·812 and 0·823. Mean values for digestible energy were 16·34, 1506 and 15·60 M]l kg dry matter. Mean values of faecal apparent digestibility of protein were 0·840, 0·760 and 0·828. The lower energy and crude protein (CP) apparent digestibility of CP relative to FP can be explained by their higher fibre content and by the presence of condensed tannins whilst the lower energy and CP apparent digestibility in WP relative to FP can be explained by their higher fibre content, their lower starch content and their higher amylosel amylopectine ratio. Among the feed peas, there was no difference between peas with low trypsin inhibitor activity and peas with medium trypsin inhibitor activity.

Influence of enzymatic treatment on the nutritional and functional properties of pea flour

The effect of enzymatic treatment on the nutritional value and functional properties of pea flour was investigated. Pea flour was hydrolyzed with acid protease from Aspergillus saitoi, to give two different hydrolyzed pea flours. This enzymatic treatment led to a significant ( p < 0.05) decrease in crude and true protein and to an increase of free amino acids and non-protein nitrogen. The nutritional value decreased, but an increase in the avilability of protein was expected as result of lower trypsin inhibitor activity and phytic acid content in hydrolyzed pea flours. The amino acid profile of unhydrolyzed pea flour was slightly modified after enzymatic hydrolysis, increasing (significantly) the isoleucine, leucine, lysine, cystine, phenylalanine, threonine, alanine, arginine and aspartic acid contents as a result of the added enzyme. In addition, enzymatic treatment released hydrophobic amino acids, which significantly improved the protein solubility at acid pH, the oil absorption capacity and the emulsification capacity of pea flours. Protein solubility, foaming capacity, foam stability, water absorption capacity, gelation capacity and green colour decreased. It was thus confirmed that treatment with acid protease improves some functional properties of pea flour, but the effect on nutritional properties was unclear.

Low Trypsin and Chymotrypsin Inhibitor Mutants in Winged Bean(Psophocarpus tetragonolobus (L) DC)

Low trypsin inhibitor (LTI) and chymotrypsin inhibitor (LCTI) mutants have been identified and isolated from the M5 mutant lines of winged bean. The LTI and LCTI lines demonstrated a true breeding feature in the subsequent generations. Three to five isoinhibitor bands of trypsin and chymotrypsin were absent in different mutants, indicating mutations in the respective gene loci. The LTI and LCTI mutants inhibited insect gut proteases as efficiently as their control counterparts. This could be attributed to a specific group of inhibitors present in all the mutant types.

Effects of a concentrate of pea antinutritional factors on pea protein digestibility in piglets

Four experiments were designed to investigate the apparent ileal digestibility of raw pea (Pisum sativum) and two of its components - an isolate of its proteins and a concentrate of its proteinaceous antinutritional factors (ANFs). Three varieties of peas were used: spring varieties Finale and Solara, and winter variety Frijaune. Pea protein isolates, devoided of pea carbohydrates and characterized by low trypsin inhibitor activities, were produced from Finale and from Frijaune. Two concentrates of ANFs were used; one from Finale and Frijaune (1:1) (batch a), one from Frijaune (batch b). The trypsin inhibitor activity was three times higher in batch b than in batch a. Eleven semi-synthetic diets containing the pea protein isolate, the pea ANF concentrates or raw peas were fed to piglets (10-15 kg live weight) fitted with post-valvular T-caecum cannula. For the raw pea diets, the apparent ileal N digestibility coefficients were 69.1% (Finale) and 69.5% (Frijaune). For the diets based on pea protein isolate, they were 83.7% (Finale) and 85.4% (Frijaune). Incorporation of 2.9% ANF concentrate (batch a) reduced the N digestibility coefficient of the diet based on Finale pea protein isolate from 83.7% to 79%. Addition of 0.6% of the other ANF concentrate (batch b) reduced the N digestibility coefficient when the diet was based on Solara raw pea (- 3 units) and not when based on pea protein isolate. © 1995.

Purification, inhibitory properties, amino acid sequence and identification of the reactive site of a new serine proteinase inhibitor from oil-rape (itBrassica napus) seed

A new serine proteinase inhibitor, rapeseed trypsin inhibitor (RTI), has been isolated from rapeseed ( Brassica napus var. oleifera) seed. The protein inhibits the catalytic activity of bovine β-trypsin and bovine α-chymotrypsin with apparent dissociation constants of 3.0 × 10 −10 M and 4.1 × 10 −7 M, at pH 8.0 and 21°C, respectively. The stoichiometry of both proteinase-inhibitor complexes is 1:1. The amino acid sequence of RTI consists of 60 amino acid residues, corresponding to an M r, of about 6.7 kDa. The p 1-p i, reactive site bond has been tentatively identified at position Arg 20-Ile 21. RTI shows no similarity to other serine proteinase inhibitors except the low molecular weight mustard trypsin inhibitor (MTI-2). RTI and MTI-2 could be members of a new class of plant serine proteinase inhibitors.

Pancreatic Enlargement Is Evident in Rats Fed Diets Containing Raw Soybeans (Glycine max) or Cowpeas (Vigna unguiculata) for 800 Days but Not in Those Fed Diets Based on Kidney Beans (Phaseolus vulgaris) or Lupinseed (Lupinus angustifolius)

Pancreatic weights and composition were studied with rats fed diets containing raw legume seeds for up to 800 d. Rapid pancreatic enlargement was induced by dietary soybeans (Glycine max) (high Kunitz and Bowman-Birk trypsin inhibitor contents, moderate lectin content) during the initial 150 d. Over the next 200 d the rate of pancreatic growth was similar to that in controls. After 350 d a second period of rapid pancreatic growth occurred. Macroscopic pancreatic nodules were evident in a number of rats fed soybeans for 500 d or more. A similar pattern of pancreatic growth was observed in rats fed dietary cowpeas (Vigna unguiculata) (high Bowman-Birk inhibitor content, low lectin content). Extensive pancreatic growth was also found in young rats fed moderate dietary levels of kidney beans (Phaseolus vulgaris) (low Bowman-Birk inhibitor content, high lectin content). However, the trophic effects diminished with time, and from 100 d onwards, little enlargement was evident. Consumption of a lupinseed (Lupinus angustifolius) diet (low trypsin inhibitor, low lectin content) did not cause pancreatic enlargement. The initial pancreatic growth induced by dietary soybeans seemed to be due to the lectins and trypsin inhibitors, whereas the second period of pancreatic growth was possibly due primarily to the trypsin inhibitors.

Predigestion of soybean proteins with immobilized trypsin for infant formula.

Soybean protein isolates of low soybean trypsin inhibitor (STI) residue were prepared by acidic precipitation of soybean flour water extracts (0.8-1.2%) at pH 5.0, followed by acidic washing at this pH and affinity adsorption of residual STI with immobilized trypsin on polystyrene anion-exchange resin GM 201. After heat treatment, soybean protein isolates were subjected to controlled hydrolysis with the immobilized trypsin. Then, the predigested soybean protein was prepared. The predigested soybean protein was free of STI activity, and its solubility at acidic pH range was greatly increased. Sedimentation test showed that it formed a much finer clot at pH 4.5 than that of untreated soybean protein. The pepsin digestibility index at pH 4.0 and chymotrypsin digestibility index at pH 8.0 were obviously improved. These results suggested that the predigested soybean protein prepared by this method may be used in infant formulas.

Effects of Heat Treatment on the Nutritional Value of Conventional and Low Trypsin Inhibitor Soybeans for Chicks

Two experiments were conducted to assess the nutritional value of conventional and low trypsin inhibitor (TI) soybeans when fed in raw or heated form for chicks. In Experiment 1, four replicates of eight chicks per pen were fed corn-based diets (19% CP, 3,158 kcal ME/kg) containing raw or heated conventional soybeans, raw or heated low TI soybeans, or conventional soybean meal (44% CP) plus oil. Heating was achieved by autoclaving the soybeans for 20 min at 110 C. Treatments were the same in Experiment 2 except that the soybeans were heated for 20 or 40 min. The TI activity of the low TI soybeans was approximately one-half that of the raw conventional soybeans (9.6 versus 22.1 mg/g). Heating reduced the TI activity of both types of soybeans. Chick growth, feed utilization, and apparent retention of dietary DM and N were markedly depressed and pancreatic hypertrophy occurred when the raw conventional soybeans were fed. Depressions in performance and N retention and increases in pancreatic weights also occurred when chicks were fed raw low TI soybeans, but the responses were not as pronounced as when raw conventional soybeans were fed. Heat treatment reduced the TI activity of both types of soybeans and resulted in improved chick weight gain, feed:gain, and dietary DM and N retention, and reduced pancreatic weights (P < .01). In Experiment 1, chicks fed low TT soybeans heated for 20 min performed as well and had equivalent pancreas weights as those fed soybean meal. In Experiment 2, chicks fed either type of soybean heated for 40 min did not perform as well as those fed soybean meal. The results indicate that low TI soybeans are nutritionally superior to conventional soybeans, but some heating is required to maximize their nutritional value.

High protein and low trypsin inhibitor varieties of full-fat soybeans in broiler chicken starter diets

Two broiler growth trials of randomized block design were conducted to evaluate the nutritional quality of two new varieties of full-fat soybeans (SB) in starter diets. Use of the high protein (HP) SB (44% CP) has the potential to replace conventional soybeans in poultry rations and reduce the amount of SB needed. Use of the low-trypsin inhibitor (LTI) SB may eliminate the cost of heat treatment before feeding to poultry. The protein sources were raw SB (39% CP, 70 Trypsin Inhibitor Units (TIU) g−1 DM), autoclaved SB, autoclaved HP SB, LTI (42 TIU g−1 DM) and commercially roasted SB. Diets were formulated to be isonitrogenous and isoenergetic. Supplementation of diets with 0.3% DL-methionine was also studied, as the antiproteolytic activity of the TI makes sulphur amino acids less available for growth. Mean body weight gains, feed efficiency, dry matter and crude protein digestibilities and total carcass protein and energy content of the chickens fed HP, autoclaved or roasted SB were superior (P &lt; 0.05) to those fed the raw SB diet. Performance of the chickens fed the HP SB diet was similar to those on the roasted SB diet. Growth and feed conversion of chicks fed the LTI diet were similar to those fed the raw SB diet. However, mean pancreas weights of the chicks fed LTI were lower (P &lt; 0.001) than those fed raw SB which could be due to the lower trypsin inhibitor activity of the LTI beans. Chickens given the methionine supplemented LTI diet made greater weight gains (P &lt; 0.05) than those on the nonsupplemented diet. Heat treatment is required for the LTI beans. Full-fat HP soybeans may replace conventional soybean meal in broiler chicken starter diets if the formulation is adjusted for the differences in their protein and fat contents. Key words: Soybeans, trypsin inhibitor, broiler, chicken growth

Biochemical Characterization of a Low Trypsin Inhibitor Soybean

ABSTRACTA low trypsin inhibitor soybean (LTI) was characterized using electrophoresis, enzyme activity measurements, and gel exclusion chromatography. The protein profiles were similar to a control soybean. Gel exclusion chromatography resulted in two peaks of trypsin inhibitor activity in the control. The first peak, absent in LTI, proved to be Kunitz trypsin inhibitor and was electrophoretically isomorphic. The second inhibitor consisted of at least five isotypes and co‐eluted with Bowman‐Birk trypsin inhibitor. Shorter heating times were required to inactivate both trypsin and chymotrypsin inhibitor activity in LTI compared to control soybeans. The use of LTI may increase the economic viability of soybeans as protein supplements for humans.

Effect of soybean flour on exocrine function in rat pancreas transplant with bladder drainage.

The urinary output of trypsin, chymotrypsin, elastase, and amylase by rats with a pancreas transplant and bladder drainage was determined after injection with cholecystokinin (CCK) or by feeding diets containing high (raw soy flour) or low (heated soy flour) trypsin inhibitor activity. The injection of CCK produced a significant increase in the urinary output of all four enzymes. Rats were fed heated or raw soy flour in three consecutive 10-day periods in the following sequence: period 1, heated soy flour; period 2, raw soy flour; period 3, heated soy flour. Replacing heated soy flour in period 1 with raw soy flour in period 2 caused a significant increase in the output of the four enzymes. Subsequent feeding with heated soy flour in period 3 resulted in a reduction in the output of trypsin, chymotrypsin, and elastase to levels that were not significantly different from that observed in period 1. Although amylase output was also reduced in period 3, it did not return to the level noted in period 1. These results are consistent with the roles that CCK and trypsin inhibitors are believed to play in the negative feedback control of pancreatic exocrine function. A similar approach might be employed with humans who have undergone a pancreas transplant with bladder drainage.

Effect of feeding soy products with varying trypsin inhibitor activities on growth of shrimp

Six isonitrogenous, isocaloric diets containing commercially defatted, toasted and lightly toasted soy flours (SF) (diets 1 and 2) and four soy protein concentrates (SPC) (diets 3–6) as replacements for 40% of animal protein were fed to satiation to juvenile shrimp (Penaeus vannamei) for 10 weeks. The SPCs used in diets 3 and 5 were chemically modified products with reduced trypsin inhibitor (TI) content. The chemical modification of SF in diet 2, which resulted in an SPC for diet 3, and of SPC in diet 4 consisted of heating at 70°C for 1 hr with 50 mM Na2S2O5, followed by dialysis to remove salt residues. To keep all diets isocaloric, cornstarch was added to replace the oli‐gosaccharides lost during processing to an SPC. The TI contents, in mg TI/g diet, were 0.77, 6.14, 0.64, 1.40, 0.92 and 1.72 for diets 1–6, respectively. Shrimp fed lightly toasted SF had the highest weight gain, which was significantly higher than shrimp fed SPC diets 4, 5 and 6, but not significantly higher than shrimp fed diets 1 and 3. No significant difference was observed in survival rates. Shrimp fed diet 3 (with lowest TI) had the highest body percentages of crude protein, while toasted soy flour diet 1, also with low TI, had the lowest content of this constituent. In general, a high body protein reflects good health of the animal and excellent utilization of the feed. At the replacement levels of soy evaluated, TI content did not affect overall weight gain.

Apparent digestibility of amino acids in raw and heated conventional and low-trypsin-inhibitor soybeans for pigs.

An experiment was conducted with ileally cannulated pigs to determine the apparent digestibility of amino acids and N in raw or heated conventional or low-trypsin-inhibitor soybeans. Six littermate barrows initially averaging 24 kg were fed cornstarch-based diets (10.5% CP, .68% lysine, 3,558 kcal of ME/kg) supplemented with raw (unheated), conventional soybeans; raw, low-trypsin-inhibitor soybeans; heated, conventional soybeans; heated, low-trypsin-inhibitor soybeans; or solvent-extracted soybean meal. Heating was achieved by autoclaving soybeans (after grinding) for 20 min at 110 degrees C. The urease activities of the two raw soybean sources were similar, but the trypsin inhibitor activity of the raw, low-trypsin-inhibitor soybeans was about one-half that of the raw, conventional soybeans. The lower trypsin inhibitor activity of the raw, low-trypsin-inhibitor soybeans was associated with an improvement in the apparent digestibility of amino acids and N compared with the raw, conventional soybeans (P less than .05). Heating reduced the urease and trypsin inhibitor activities and improved (P less than .05) the apparent digestibility of amino acids and N in both types of soybeans. However, the heated, conventional soybeans contained more trypsin inhibitor activity than the heated, low-trypsin-inhibitor soybeans and the digestibilities of the amino acids were lower (P less than .05). Although the urease and trypsin inhibitor activities of the two heated soybean sources were similar to or less than those of soybean meal, the digestibilities of amino acids were not as great (P less than .05) in the heated soybeans as in soybean meal.(ABSTRACT TRUNCATED AT 250 WORDS)