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PubMed1993

Gastrointestinal responses of rats fed on white and wholemeal breads: complex carbohydrate digestibility and the influence of dietary fat content.

To obtain quantitative information on the digestibility of the non-starch polysaccharides (NSP) fraction of white and wholemeal breads, rats were fed on diets in which freeze-dried bread (white, wholemeal or mixtures of the two) provided all the complex carbohydrates. In a second experiment the possibility that dietary fat concentration might influence NSP digestibility was tested by feeding diets containing 30 or 170 g maize oil/kg and either white or wholemeal bread. Multiple linear regression analysis provided little evidence of associative effects of dietary components on NSP digestibility and in the two experiments digestibilities of NSP for white and wholemeal breads were 0.77-0.82 and 0.47-0.52 respectively. Xylose- and arabinose-containing polymers were better digested than was cellulose for both breads. Replacing white by wholemeal bread markedly increased the molar proportion of butyrate in caecal volatile fatty acids at the expense of acetate. This was associated with greater flows of organic matter to the large bowel (LB) and a reduction in caecal transit time (Expt 2). There was little detectable effect of dietary maize oil concentration on NSP digestibility or on LB fermentation. All breads contained some starch resistant to pancreatic alpha-amylase (EC 3.2.1.1) without previous treatment with dimethyl sulphoxide. The digestibility of this starch fraction was not significantly different from 1.0 for all diets except that containing wholemeal bread and the higher maize oil concentration where the apparent digestibility was 0.89.

Acetates↗
PubMed2004

Posthatch growth of the digestive system in wild and domesticated ducks.

1. Our study was designed to test the hypothesis that domestication and artificial selection have influenced the posthatch growth and functioning of the gastrointestinal (GI) tract of ducks. The mass and length of the GI tract organs, the growth of intestinal villi, the intestinal surface area and the activities of brush border digestive enzymes were measured in a commercial strain of Pekin duck and its wild ancestor, the mallard (Anas platyrhynchos), at regular intervals between hatch and 16 weeks of age. 2. The growth of the digestive organs, with respect to body mass, was described using allometry. Allometric mass exponents were then used to calculate body 'mass-corrected', or 'relative' organ masses, relative surface areas and relative enzyme activities. There were appreciable differences between data presented on a mass-specific (g/kg) and a mass-corrected (g/kg(b)) basis, which highlighted the importance of correcting for the complete effects of body mass when comparing the growth and function of the digestive system between strains. 3. While the process of domestication has induced major changes in the absolute characteristics of the GI tract, it has failed to have the same effect on the relative characteristics. During the first 2 weeks posthatch, the relative masses of the majority of digestive organs, and the GI tract as a whole, were the same in both strains. During weeks 3 to 5, domesticated ducks maintained higher absolute growth rates of the body and the GI tract, with the support of relatively smaller digestive organs. The relative masses of the small intestine and the GI tract as a whole were 45 and 66% higher respectively in mallards than in Pekin ducks during this period. 4. Domesticated ducks had elevated digestive enzyme activity and a greater absorptive surface area than mallards throughout development, both in absolute and relative terms. This appears to compensate for the failure of the relative masses of digestive organs in domesticated ducks to accompany the increased body mass and growth rate. 5. At 5 weeks posthatch, the absolute mass of the small intestine in domesticated ducks declined by 38%. There is no obvious explanation for this decline because the masses of other digestive organs, daily feed intake and body mass continued to rise.

Aging↗
PubMedDate not supplied

Developmental changes in digestive physiology of nestling house sparrows, Passer domesticus.

Six decades of studies have speculated that digestive capacity might limit avian growth rate or that developmental changes in the gut might determine developmental changes in digestive efficiency. However, there are no studies on digestive enzymes during avian development, except for studies on mainly domestic birds that exhibit the precocial mode of development. We studied alimentary organ masses, intestinal enzyme activities (sucrase, maltase, isomaltase, aminopeptidase-N), and pancreatic enzyme activities (amylase, trypsin, chymotrypsin) during development of a wild passerine bird exhibiting the altricial mode of development. Wild nestling house sparrows were studied immediately after removal from the nest (days 0, 3, 6 of age; day 0=hatch), whereas captives were raised in the laboratory beginning day 3 on a formulated casein/starch-based diet until fledging age (after day 12). Digestive biochemistry was dynamic. Tissue-specific activities of some digestive enzymes continued to increase through fledging, by >10 times in some cases (e.g., sucrase and maltase in midintestine). Total pancreatic amylase activity increased 100 times between hatch and day 12 through a combination of increases in tissue-specific activity and pancreas mass. House sparrows differ from poultry, in whom after about 2 wk of age the specific activity of intestinal and pancreatic digestive enzymes is generally constant or declines during development. The data on intestinal and pancreatic enzymes help explain why digestive efficiency of nestling house sparrows improves with age, and the data seem consistent with the idea that digestive capacity might limit feeding rate and hence growth rate.

Animals↗
PubMed2001

Novel methodology allows simultaneous measurement of true phosphorus digestibility and the gastrointestinal endogenous phosphorus outputs in studies with pigs.

Methodology was developed for measuring the gastrointestinal endogenous phosphorus (P) outputs and true P digestibility values in studies with piglets. Four barrows, average initial body weight 6.8 kg, were fitted with a simple T-cannula at the distal ileum and fed four diets according to a 4 x 4 Latin square design. Four cornstarch-based diets containing four levels of P (1.1, 2.1, 3.2 and 4.3 g/kg diet) on a dry matter (DM) basis were formulated from soybean meal (SBM). Each experimental period comprised 8 d with a 4-d adaptation and 4-d collection of ileal digesta and feces. The apparent ileal and fecal P digestibility values in SBM were affected (P < 0.05) by P levels in the assay diets. The ileal and fecal P digestibility values increased from -24.8 to 37.1% and from 18.8 to 42.5%, respectively, as P contents increased from 1.1 to 4.3 g/kg DM diet. Linear relationships (P < 0.05), expressed as g/kg DM diet intake, between ileal and fecal outputs and dietary inputs of P, suggested that the endogenous P outputs can be determined by linear regression analysis. The endogenous P output was higher (P < 0.05) in ileal digesta than in feces (0.86 +/- 0.09 vs. 0.31 +/- 0.06 g/kg DM diet intake). There was no difference (P > 0.05) between the true ileal (50.7 +/- 7.1%) and fecal (48.5 +/- 5.4%) P digestibility values in SBM. These results suggest that differences in P contents between assay diets are primarily responsible for the large variability in apparent P digestibility values reported within the same ingredient. Apparent digestibility values underestimate the true digestive utilization of P by approximately 25%. True rather than apparent P digestibility values should be determined and used in diet formulation for pigs. In addition, this study shows that the gastrointestinal endogenous P output is important in whole-body P requirement and homeostasis.

Absorption↗
PubMed1995

Interaction of feed intake level on comparative ruminal and total tract digestion of dry-rolled and steam-flaked corn.

Four Holstein steers (208 kg) with "T" cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square design experiment to evaluate the interaction of feed intake level on comparative ruminal and total tract digestion of dry-rolled and steam-flaked corn. The basal diet contained (DM basis) 6% alfalfa hay, 6% sudangrass hay, 75% corn, 2% yellow grease, 5% cottonseed meal, 3% cane molasses, and 3% supplement. The corn portion of the diet was provided as either dry-rolled (density = .54 kg/L) or steam-flaked (density = .36 kg/L). Dry matter intake was restricted to allow for .64 vs 1.28 kg/d of weight gain (1.6 vs 2.4% of BW). Ruminal digestibility of OM, starch, and feed N were not affected (P > .10) by DMI. Postruminal digestion of OM and N and total tract digestibility of OM and DE decreased (P < .05) as DMI was increased. Total tract starch digestibility was not influenced (P > .10) by DMI. Steam flaking corn increased (P < .05) ruminal digestibility of OM and starch and postruminal and total tract digestibility of OM, starch, N, DE, and ME. Increasing DMI and steam flaking decreased (P < .05) ruminal pH and molar proportion of acetate. It is concluded that corn processing is the primary factor influencing site and extent of starch digestion. Decreasing DMI increases DE value of the diet; however, ME value is not affected because of increased energy loss as methane.

Animal Feed↗
PubMed2001

Comparative total tract digestibility of dietary energy and nutrients in growing pigs and adult sows.

Seventy-seven diets were fed to 61-kg growing pigs at a feeding level close to their ad libitum intake and to nonlactating, nonpregnant sows slightly above their maintenance energy level (2.4 kg/d). The main objectives of this study were to compare the total tract digestibility of dietary energy or nutrients of the 77 diets in growing pigs and adult sows and to analyze the effect of diet chemical composition on total tract digestibility in both groups of pigs. Diets were formulated to represent a range of chemical compositions as large as those found in most practical situations. The DE and ME values and total tract digestible nutrient contents of diets were measured for each group of animals; each diet was measured in four to five animals per group, and collection of urine and feces lasted 10 d. The results were used to establish equations for predicting DE and ME values, total tract digestible nutrient contents, and total tract digestibility coefficients of energy from chemical characteristics for each group of animals. The results show that the total tract digestibility of energy or nutrients was higher (P < 0.01) in adult sows than in growing pigs; the total tract digestibility coefficients of energy, crude protein, ether extract, and NDF averaged 85.2, 85.1, 37.1, and 64.4%, respectively, for sows and 82.1, 80.3, 31.6, and 56.3%, respectively, for growing pigs. The ME/DE ratio was lower (P < 0.01) in sows (94.8%) than in growing pigs (96.5%), as a result of higher urinary energy losses in sows. The difference in DE values (on average, 0.6 MJ/kg of DM) between adult sows and growing pigs was not constant (P < 0.01) but increased with dietary fiber content (3.3, 8.6, and 10.1 kJ for each gram of NDF, ADF, and crude fiber increase in the diet, respectively), which suggests that the origin of the difference between the two physiological stages is mainly due to a higher rate of degradation of dietary fiber in the hindgut of sows. The DE and ME values could be accurately predicted from total tract digestible nutrients or from chemical characteristics for each physiological stage. Equations for predicting urinary energy loss from urinary N are also proposed. From a practical point of view, it is suggested to use two energy values for pig feeds: one applicable to growing-finishing pigs and one to adult sows. Equations for predicting DE in adult sows from energy values obtained in growing pigs are proposed.

Age Factors↗
PubMed1991

Site of digestion of starch in the gastrointestinal tract of dairy cows and its effect on milk yield and composition.

Physical and chemical processing of feed ingredients and feeding management strategies are major instruments of manipulating amount and site of starch digestion in the gastrointestinal tract. Generally, as rumen escape of starch increases, postruminal starch digestion increases, and there does not appear to be a limitation to intestinal starch digestion. However, the efficiency with which postruminal starch is digested decreases, which represents a limitation that warrants investigation. Even though digestible dietary starch is presented to the intestine, there is no net glucose absorption at the portal vein, and plasma glucose levels remain relatively unaffected. This result may be associated with the large metabolic requirement for postruminally absorbed glucose, which is preferentially used for oxidative metabolism at the visceral tissue level. In addition, peripheral glucose concentration is highly regulated. A possible implication is that the exogenous glucose supply may spare endogenously synthesized glucose for gut metabolism, allowing more to be directed to the mammary gland. Amino acids also may be spared (less metabolism of dietary and tissue amino acids in the gut). Current production studies yield no clear evidence as to the benefits of postruminal digestion of starch to enhance milk yield or to change its composition. However, studies suggest that starch digested postruminally is used more efficiently for milk synthesis than that digested in the rumen.

Animals↗
PubMed2003

In vitro study on digestion of peptides in Emmental cheese: analytical evaluation and influence on angiotensin I converting enzyme inhibitory peptides.

A simple in vitro protocol simulating gastrointestinal digestion of proteins and peptides to investigate the effect of digestive enzymes on the biological activity of peptides present in dairy products was developed. This protocol consisted in a 30 min incubation with pepsin followed by a 4 h incubation with trypsin or pancreatin. It was applied to an Emmental cheese water-soluble extract (WSE) and to a casein solution (as a control). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) allowed to monitor the digestion of proteins. Reversed-phase high-performance liquid chromatography (RP-HPLC) allowed to monitor the conversion of proteins and peptides into peptides and amino acids: it is proposed to use the mean retention time corresponding to the overall retention time distribution of molecules to assess the effect of digestive enzymes. The biological activity focused in this study was the angiotensin I converting enzyme (ACE) inhibitory activity. Digestion of Emmental WSE induced an increase of the ACE inhibition as compared to undigested WSE while a 10 kDa ultrafiltered WSE lost a part of its ACE inhibitory activity after digestion process. These results strongly suggest that digestive enzymes diminished the ACE inhibition by the peptides present in Emmental cheese WSE, while the digestion of peptides of high molecular weight would generate new ACE inhibitory peptides.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2003

Improvement of the digestibility of the proteins of the red alga Palmaria palmata by physical processes and fermentation.

Palmaria palmata (dulse) is an edible red alga constituting a potential protein source in human diet. However, previous studies showed that the digestibility of dulse proteins is bad because of the cell-wall encapsulating cytoplasmic proteins and the presence of fibers. The water-soluble xylan, present in high proportions in dulse, could be involved to explain the weak digestibility of proteins. To limit the influence of fibers and to improve the nutritional quality of these proteins, we have treated dulse by physical processes or by fermentation by moulds. After a 30 min predigestion by pepsin followed by a 6 h digestion into a cell dialysis containing porcine pancreatin, the corrected in vitro digestibility of crude dulse was very low (about 1.5% after correction by digestibility blank). The in vitro protein digestibility was estimated to 58% of that of casein for dulse samples obtained after washing in demineralized water and grinding in liquid nitrogen. The in vitro protein digestibility of fermented samples was 45%-65% of that of casein. After physical treatment, the digestibility improvement was related to the elimination of soluble molecules such as xylan and mineral salts. The improvement observed after fermentations seemed due to the degradation of insoluble fibers.

Aspergillus↗
PubMed1994

Seasonal variation of trace metal concentrations in the digestive gland of the Mediterranean mussel Mytilus galloprovincialis: comparison between a polluted and a non-polluted site.

Seasonal changes in metal (Cu, Fe, Mn, Pb, and Zn) concentrations were observed in the digestive gland of the Mediterranean mussel, Mytilus galloprovincialis, from both a polluted and a non-polluted population. Digestive gland of mussels from the polluted site showed metal concentrations appreciably higher than in non-polluted organisms, especially for Pb (up to 160 micrograms/g d.w.), Mn (up to 300 micrograms/g d.w.), and Fe (up to 8,500 micrograms/g d.w.), whereas the two populations showed maximum mean values, respectively, of 34 and 20 micrograms/g d.w. for Cu and 170 and 120 micrograms/g d.w. for Zn. Over 1 year (1991), differences between maximum and minimum values were moderate only in the unpolluted organisms. During gametogenesis, while the metal concentrations (expressed as microgram/g dry weight) decreased in the digestive gland, the tissue burden (as microgram) in that organ remained nearly constant or increased slightly. The apparent decrease in metal concentrations was probably due to the penetration of gonadic tissues into the digestive gland during gametogenesis, which biologically diluted metal concentrations in mussels from both the polluted and unpolluted populations. The effect of mussel size on trace metal concentrations in the digestive gland was demonstrated during different stages of the reproductive cycle. Higher concentrations were found in smaller organisms; however, during the spawning period, due to the fact that this is not a synchronous process within a population, the organisms exhibit a high variability in digestive gland weight which can mask this relationship when digestive gland weight is used as a size-index and as a parameter of the trace metal digestive gland burden.

Animals↗
PubMed1976

Studies on the ultrastructure, histochemistry and cytochemistry of the uninfected digestive gland of Bithynia tentaculata (Mollusca: Gastropoda) and on the ultrastructure of this host organ in snails infected with larval digeneans.

The structure and function of the digestive gland of the gastropod mollusc, Bithynia tentaculata, was investigated using ultrastructural, histochemical, and cytochemical techniques. The digestive gland was shown to be composed of two main cell types, the "digestive" cells and "secretory" cells. The digestive cells appeared to be concerned with the absorption and digestion of nutrients, while secretory cells produced digestive enzymes and calcareous concretions. Undifferentiated cells were scattered between these two main cell types. The pathological effects of larval digeneans on the digestive gland were also investigated, at the ultrastructural level. In such infected snails the digestive gland appeared to be degenerating. The significance of this tissue destruction was briefly discussed.

Acid Phosphatase↗
PubMed2000

Influence of heat treatment of casein in presence of reducing sugars on Zn solubility and Zn uptake by Caco-2 cells after in vitro digestion.

The effect of the heat treatment of casein in presence of reducing sugars on some aspects of Zn availability was investigated. Samples were prepared by mixing casein with glucose-fructose, and were used unprocessed (C) or heated (HC). Changes in Zn speciation after the in vitro digestion of the samples, both as part of a diet and in isolation, were studied. The uptake of soluble Zn from the digested samples was investigated in Caco-2 cells. After in vitro digestion, the percentage of precipitated Zn was significantly higher with the HC sample, both when digested alone and as a part of the diet. In assays with Caco-2 cells, a significant decrease in Zn uptake was observed when the uptake buffer contained the sample C digest, by comparison with the control buffer, without casein digest. When the digested heated mixture was added, Zn uptake by the cells was significantly lower than in either of the two other cases. It may be concluded that the heat treatment of casein in the presence of glucose-fructose has a negative effect on Zn availability because, after in vitro digestion, Zn insolubilization was enhanced and Zn uptake by the enterocyte was impaired, compared with the unheated mixture. In addition, the usefulness of Caco-2 cells in this kind of research has been shown.

Caco-2 Cells↗
PubMed2004

Three digestive movements in Hydra regulated by the diffuse nerve net in the body column.

The mammalian digestive tract undergoes various digestive movements such as peristalsis and segmentation movement. How those digestive movements and the underlying mechanisms appeared in evolution remains unraveled. A widely accepted view has been that, early in evolution, the digestive process was static based upon diffusion, and later it became dynamic involving digestive movements. Here, we report digestive movements which occur in Hydra, a member of the phylum Cnidaria. We find that the body column of Hydra undergoes a series of movements when fed with Artemia. Comparison of the movements to those in mammals showed similarities in appearance to esophageal reflex, segmentation movement, and defecation reflex. When nerve cells were eliminated, polyps showed only a weak segmentation movement, demonstrating that the diffuse nerve net in the body column of Hydra primarily regulates the movements just as the netlike enteric nervous system does in mammals. Elimination of both secretory gland cells and nerve cells resulted in the complete loss of movement, suggesting that the gland cells are involved in the weak movement. Overall, these observations suggest that the digestive process in Hydra is dynamic and that the diffuse nerve net regulates the digestive movements as a primitive form of enteric nervous system.

Animals↗
PubMed2004

Dynamic digestive responses to increased energy demands in the leaf-eared mouse (Phyllotis darwini).

A major area of interest in comparative physiology has been to understand how animals cope with changing environmental demands in time and space. The digestive system has been identified as one of the more sensitive systems to changes in environmental conditions. However, most research on this topic has evaluated these effects during peak energetic demands, which do not allow for evaluation of the dynamics of the digestive response along a more natural continuous gradient of environmental conditions. We examined phenotypic flexibility in digestive responses of the leaf-eared mouse Phyllotis darwini to increments in total energy demands (via sequential exposure to 26, 12 and 0 degrees C). Additionally, we evaluated the effect of a moderate energy demand (12 degrees C) over three different time periods (7, 17 and 27 days) on digestive traits. Moderate increases in energy demand were associated with changes in the distribution of digesta in the gut, whereas higher increases in energy demand involved increases in the tissue mass of digestive organs. Time-course analysis showed that at 12 degrees C practically all digestive variables reached stable values within 7 days, which is in agreement with empirical data and theoretical deductions from cellular turnover rates. We conclude that although the input of energy and nutrients into the digestive tract is typically periodic, many aspects of digestive physiology are likely to be flexible in response to environmental variability over both short-term (daily) and long-term (seasonal) time scales.

Adaptation, Physiological↗
PubMed2004

In vitro starch digestibility and in vivo glucose response of gluten-free foods and their gluten counterparts.

BACKGROUND: Recently there has been increasing interest in the production of gluten-free (GF) foods and studies on minor cereals and pseudocereals without celiac activity in order to fulfill the specific needs of people affected by celiac disease. GF bread, pasta, biscuits are usually manufactured using different combinations of thickenings and particular food processing procedures that could affect starch digestibility. Carbohydrates, mainly starch from cereals, play an important part in a balanced diet, and dietary guidelines suggest a diet with low glycemic index foods, that is to say rich in slowly digested carbohydrates. AIM: The present study was aimed at evaluating: 1) the importance of some GF food characteristics in relation to their effects on in vitro starch accessibility to digestion, in comparison with traditional gluten products; 2) the in vivo metabolic responses to GF foods. METHODS: Firstly, starch digestibility of several products was evaluated in vitro. Then, an in vivo study was performed on a group of healthy volunteers. Postprandial glucose and insulin responses were evaluated after administration of three GF foods and traditional bread. Triglycerides and free fatty acids (FFA) were also evaluated. Attempts were also made to explore differences in metabolic responses to GF foods in healthy subjects with respect to celiac subjects. RESULTS: The area under the curve (AUC) of digested starch of GF bread was slightly higher than that of the traditional counterpart. No significant difference was observed in AUCs of digested starch between GF pasta and the traditional pasta. The AUCs of digested starch of quinoa and the two samples of pasta were not statistically different. Significant differences were observed between GF bread and bread-like products. Statistic differences in glucose responses to GF pasta were observed between healthy and celiac subjects. In healthy subjects, the AUCs of glucose response after GF bread were higher than those after bread with gluten. No significant differences were observed between the AUCs of insulin responses to all products tested. Glycemic index (GI) for GF pasta was similar to GI for GF bread while GI for quinoa was slightly lower than that of GF pasta and bread. Two-way ANOVA revealed that quinoa induced lower FFA levels with respect to GF pasta. In addition, triglyceride concentrations were significantly reduced for quinoa with respect to GF bread and bread. CONCLUSIONS: Our results indicate that the different formulations and the food processing procedures used in the manufacturing of GF products may affect the rate of starch digestion both in vitro and in vivo. It may be worthwhile improving the formulation of these products. Furthermore, quinoa seems to represent a potential alternative to traditional foods, even if further and larger studies are required to demonstrate its hypoglycemic effects.

Adult↗
PubMed2006

Immunocytochemical localization of scorpion digestive lipase.

The scorpion hepatopancreas consists of digestive diverticula and interstitial tissue. A digestive diverticulum is composed of two differentiated cell types: the secretory zymogene-like cells and the digestive cells which are the most abundant. The scorpion digestive lipase (SDL) has been previously purified from scorpion hepatopancreas, but its cellular localization has not yet been established. Polyclonal antibodies specific to SDL were prepared and used in immunofluorescence and immunogold techniques to determine the cellular location of SDL. Our results clearly established that SDL was detected intracellularly in specific vesicles tentatively named (SDL+) granules of the digestive cells. No immunolabelling was observed in secretory zymogene-like cells. This immunocytolocalization indicates that lipid digestion might occur in specific granules inside the digestive cells, as suggested by previous studies on the scorpion digestive process.

Animals↗
PubMed2005

Processing cotton gin trash to enhance in vitro dry matter digestibility in reduced time.

Cotton gin trash (CGT) in the raw form is poorly digested by ruminants due to lignocellulosic complexes. These structures must be broken down before adequate digestion can occur. This may be performed by physical and/or chemical means. Two methods for improving digestibility are particle size reduction and/or treatment with sodium hydroxide (NaOH). To evaluate the effectiveness of each method, three experiments were performed in which different CGT types were tested. Each type represented trash from a particular cleaning stage in the cotton ginning process. First, each type was ground with a knife-type grinding mill using screen sizes 0.5, 1.0, and 2.0 mm. For the second experiment, particle size was held constant at 2 mm, and all CGT types were treated with 4% and 6% NaOH (w/w) at room temperature. An agitation cycle of 5 min on and 10 min off was used, with the total mixing time being 4 h. Lastly, particle size and NaOH concentration were held constant, and treatments were performed at room temperature, 40 degrees C, and 50 degrees C. The total mixing times were 2 and 3 h for 50 and 40 degrees C, respectively. For all experiments two subsamples of each treatment were tested for in vitro dry matter digestibility (IVDMD). From grinding alone, digestibility increased as particle size decreased. Grinding to 0.5 mm resulted in an average IVDMD of 47.8% while grinding to 2.0 mm resulted in an average IVDMD of only 33.8%. Digestibility also improved with a greater NaOH concentration. An average in vitro digestibility of 70.5% was achieved with 6% NaOH (w/w) treatment, essentially doubling that of the raw CGT. Increasing the reaction temperature did not result in increased digestibility because the mixture dried out, with a consequent reduction in chemical distribution and uniformity in heat transfer. There are still chemical residues in the CGT, and elimination/reduction of these is an issue that needs to be addressed in further research.

Animal Feed↗
PubMed2005

Arterial acid-base status during digestion and following vascular infusion of NaHCO(3) and HCl in the South American rattlesnake, Crotalus durissus.

Digestion is associated with gastric secretion that leads to an alkalinisation of the blood, termed the "alkaline tide". Numerous studies on different reptiles and amphibians show that while plasma bicarbonate concentration ([HCO(3)(-)](pl)) increases substantially during digestion, arterial pH (pHa) remains virtually unchanged, due to a concurrent rise in arterial PCO(2) (PaCO(2)) caused by a relative hypoventilation. This has led to the suggestion that postprandial amphibians and reptiles regulate pHa rather than PaCO(2). Here we characterize blood gases in the South American rattlesnake (Crotalus durissus) during digestion and following systemic infusions of NaHCO(3) and HCl in fasting animals to induce a metabolic alkalosis or acidosis in fasting animals. The magnitude of these acid-base disturbances were similar in magnitude to that mediated by digestion and exercise. Plasma [HCO(3)(-)] increased from 18.4+/-1.5 to 23.7+/-1.0 mmol L(-1) during digestion and was accompanied by a respiratory compensation where PaCO(2) increased from 13.0+/-0.7 to 19.1+/-1.4 mm Hg at 24 h. As a result, pHa decreased slightly, but were significantly below fasting levels 36 h into digestion. Infusion of NaHCO(3) (7 mmol kg(-1)) resulted in a 10 mmol L(-1) increase in plasma [HCO(3)(-)] within 1 h and was accompanied by a rapid elevation of pHa (from 7.58+/-0.01 to 7.78+/-0.02). PaCO(2), however, did not change following HCO(3)(-) infusion, which indicates a lack of respiratory compensation. Following infusion of HCl (4 mmol kg(-1)), plasma pHa decreased by 0.07 units and [HCO(3)(-)](pl) was reduced by 4.6 mmol L(-1) within the first 3 h. PaCO(2), however, was not affected and there was no evidence for respiratory compensation. Our data show that digesting rattlesnakes exhibit respiratory compensations to the alkaline tide, whereas artificially induced metabolic acid-base disturbances of same magnitude remain uncompensated. It seems difficult to envision that the central and peripheral chemoreceptors would experience different stimuli during these conditions. One explanation for the different ventilatory responses could be that digestion induces a more relaxed state with low responsiveness to ventilatory stimuli.

Acidosis↗