SEARCH · Search PubMed

Results for “DIGESTION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources

PubMed1980

Effect of refined cellulose on apparent energy, fat and nitrogen digestibilities.

Seven young women consumed a low cellulose diet for about 1 month and then the same diet for an additional month except that 16 g/day Solka Floc was added to the diet. Apparent digestibilities of energy, fat and nitrogen were measured for each subject during each diet. Digestibilities of fat and nitrogen were not affected by refined cellulose ingestion. Digestibility of nitrogen was 93.2% without and 92.9% with the Solka Floc, while fat digestibility was 96.3% during the control diet and 95.4% during the high cellulose diet. Mean digestibility of gross energy decreased significantly when cellulose was added to the diet, from 95.4% to 92.0% (P < 0.01). Undigested fecal fiber was the major source of the increased fecal energy. When fecal fiber energy was subtracted from total fecal energy and apparent energy digestibility recalculated, there was no difference in apparent energy digestibility during the 2 diets, 96.1% without and 95.6% with the Solka Floc supplement. Thus, ingestion of 16 g/day Solka Floc had no detrimental effect on the utilization of nitrogen and fat and increases in fecal energy could be explained by undigested refined cellulose.

Adult↗

PubMed1981

Neutral detergent fiber, hemicellulose and cellulose digestibility in human subjects.

The fate of dietary fiber and its components was examined in seven women consuming low cellulose (LC) and high cellulose (HC) diets, each for about 1 month. The diets were of constant daily composition and differed only in that the HC diet contained an additional 16 g/day non-nutritive fiber (Solka Floc), which increased the neutral detergent fiber (NDF) of the diet from 9.5 to 23.5 g/day and Crampton and Maynard cellulose from 5.4 to 19.3 g/day. When apparent fiber digestibilities during 5-day periods were determined, both NDF and cellulose digestibilities varied greatly and inconsistently in each subject throughout both diet periods. Therefore, samples were pooled to form a single 20-30 day composite for each subject during each diet. Mean apparent NDF digestibility, after correcting for protein contamination in fecal NDF, was 70.4 +/- 7.3% during the LC diet and decreased to 23.0 +/- 15.0% during the HC diet. Cellulose digestibility was 69.7 +/- 10.7% without and 15.7 +2- 17.4% with the added cellulose. Hemicellulose was calculated as NDF minus cellulose. When the fecal NDF was corrected for protein contamination, hemicellulose digestibility averaged 71.7 +/- 5.4% during the LC diet and 51.0 +/- 7.9% during the HC diet. In a separate experiment, 16 g/day Solka Floc was ingested with a semi-purified liquid diet and only 8% of the cellulose was digested. These results suggest that more than half of the fiber in a LC diet containing fruits, vegetables and refined grains is degraded, while the apparent digestibility of refined cellulose is minimal.

Adult↗

PubMed1982

Assessment of protein digestibility by in vitro enzymatic hydrolysis with simultaneous dialysis.

An in vitro digestion method to assess the quality of proteins based on enzymatic hydrolysis is presented. The method consists of a two-step proteolysis at 37 degrees, a 30-minute incubation of the protein with pepsin at pH 1.9, followed by pancreatin digestion at pH 8 for 24 hours in a dialysis bag with a 1000 molecular weight cutoff for the continuous elimination of the digested products into a replaceable buffer. Three types of buffer replacement were tried. These were, in increasing order of efficiency: intermittent with either six changes (infrequent buffer replacement) or eleven changes (frequent buffer replacement) or continuously circulated at the rate of 212 ml/hour (continuous buffer replacement). By using three protein sources, i.e., casein, soybean and rapeseed proteins, it was found that the degree of digestion (dialyzed N) as well as the regularity of the process were markedly improved by increasing the frequency of buffer replacement. In spite of different pepsin digestibilities, as determined from the production of trichloroacetic acid-soluble N, the digestion of the three proteins gave equivalent results when the best procedure of buffer replacement was used (continuous buffer replacement). The deleterious effect of heat and alkali treatment on protein digestion was readily shown by this procedure and indicated casein to be a very heat-sensitive protein as compared to the others.

Brassica↗

PubMed1999

The influence of cecectomy on metabolizable energy and amino acid digestibility of select feedstuffs for white Pekin ducks.

Twenty-four cecectomized and 24 intact White Pekin ducks were used in two experiments to assess the influence of cecectomy on ME and amino acid digestibility of several feed ingredients for ducks. Corn and soybean meal (SBM) were evaluated in Experiment 1, and bakery meal (BM), red dog (RD), and wheat middlings (WM) were evaluated in Experiment 2. Nitrogen-corrected true metabolizable energy and amino acid digestibility of the ingredients were assayed concurrently. In Experiment 1, TME of corn was higher (P < or = 0.05) in cecectomized ducks, and intact ducks demonstrated greater (P < or = 0.05) ability to utilize the energy in SBM. Intact ducks exhibited higher (P < or = 0.05) true digestibilities of lysine and methionine. True digestibility of tryptophan was higher (P < or = 0.05) for cecectomized ducks. True digestibility of indispensable amino acids in SBM did not differ (P > or = 0.05) between cecectomized and intact ducks. In Experiment 2, cecectomized ducks exhibited greater (P < or = 0.05) ability to utilize the energy in RD. Intact ducks exhibited greater (P < or = 0.05) ability to utilize the energy in WM. True digestibility of indispensable amino acids in BM, RD, and WM was variable. Results of the present study suggest that the effect of cecectomy on nutrient digestibility in ducks is dependent on the feedstuff assayed.

Amino Acids↗

PubMed2003

The relation between starch digestion rate and amino acid level for broiler chickens.

Digestion coefficients of nutrients give information about the amount of nutrients available to the animal but not about the rate or site of absorption. Gradual digestion of starch may have an amino acid sparing effect and therefore enhance growth efficiency of broiler chickens. A growth trial was performed with 6,800 broiler chickens from 9 to 30 d of age to investigate interactions between starch digestion rate and amino acid level. Birds were fed either a pea-corn-based diet (slowly digestible starch) or a tapioca-corn-based diet (rapidly digestible starch). Both diets were formulated with five levels of digestible lysine, varying from 8.5 to 11.0 g/kg. The minimal levels of other amino acids varied accordingly. Starch source did not affect feed intake (2,213 g), but weight gain was consistently higher for birds on pea-corn diets than for those on tapioca-corn diets (1,426 vs. 1,400 g; P < 0.01). Feed conversion was better (P < 0.01) for birds on pea-corn diets (1.55) than for birds on tapioca-corn diets (1.58). The difference in feed conversion between birds on pea-corn and tapioca-corn diets was greater with lower amino acid levels (0.043) than with higher amino acid levels (0.019) in the diet (P = 0.11). This interaction was more pronounced during the first 9 d of the experiment (P < 0.05). It was concluded that feeding slowly digestible starch improved protein and energy utilization in broiler chickens.

Amino Acids↗

PubMed2004

Effect of microbial phytase on ileal digestibility of phytate phosphorus, total phosphorus, and amino acids in a low-phosphorus diet for broilers.

The study aimed to assess the effect of a commercially available microbial phytase added to a corn-soybean meal diet on phytate P and total P in terminal ileal digesta as well as on true ileal amino acid digestibility. Three low-P diets containing 0, 500, or 750 U/kg of microbial phytase were fed to 21-d-old broiler chickens. Titanium dioxide was used as an indigestible marker. Ileal contents were collected from euthanized birds and analyzed, along with the diets, for total P, phytate P, and amino acids. Endogenous P determined at the terminal ileum was 446 +/- 59 mg/kg food dry matter (mean +/- SE). Endogenous ileal amino acids ranged from 219 +/- 33 mg/kg food dry matter for tryptophan to 1,255 +/- 166 mg/kg food dry matter for glutamic acid. Supplementation with microbial phytase resulted in a significantly (P < or = 0.05) greater phytate P disappearance (11% greater disappearance vs. unsupplemented control) from the terminal ileum. Similarly, true ileal total P digestibility was (P < or = 0.05) higher (10 to 12%) when microbial phytase was added. True ileal amino acid digestibility was significantly (P < or = 0.05) greater in the presence of microbial phytase for all the amino acids examined with the exception of methionine, tyrosine, histidine, and tryptophan. The mean increase in true ileal amino acid digestibility was 3.4%. The effect of phytase on true ileal phytate P, total P, and amino acid digestibility was similar for the 2 phytase inclusion levels tested. Microbial phytase improved phytate P and total P digestibility, as well as true ileal amino acid digestibility, for a corn-soybean diet.

6-Phytase↗

PubMed2006

Chemical treatments to reduce antinutritional factors in salseed (Shorea robusta) meal: effect on nutrient digestibility in colostomized hens and intact broilers.

This study investigated the effects of chemical treatments of salseed meal (SSM) on nutrient digestibility and digestive enzymes in colostomized hens and intact broilers. Finely ground SSM was treated (820 mL/ kg of SSM DM) with distilled water (pH 5.3), 0.67 M acetic acid (pH 2.4), or 0.67 M sodium hydrogen carbonate (pH 8.2), and incubated for 12 h at 37 degrees C. Five isonitrogenous and isocaloric diets each for colostomized hens (25.6 g of N/kg of DM and 12.5 MJ/kg of DM) and for broilers (33.6 g of N/kg of DM and 12.3 MJ/kg of DM) were formulated. For each group, 1 of these diets was wheat-based (control) whereas the other 4 were SSM-based diets (untreated SSM or SSM treated with water, acetic acid, and sodium bicarbonate). Inclusion of SSM in diets markedly reduced apparent protein and starch digestibility in hens and broilers. Chemical treatments of SSM improved the protein and starch digestibilities in colostomized hens and broilers. Treatment of SSM with alkali reduced the pancreatic hypertrophy in broilers that was observed when SSM was included in the diet. Inclusion of SSM in broiler diets did not affect pancreatic trypsinogen activity; however, chymotrypsinogen and alpha-amylase activities were depressed with its inclusion. Activities of these enzymes were improved by all chemical treatments of SSM. Dietary inclusion of SSM in broiler diets depressed the activities of trypsin, chymotrypsin, and alpha-amylase in the jejunal digesta. Alkali treatment proved to be the most effective in reducing the adverse effects of SSM upon trypsin and chymotrypsin activities. The hens receiving SSM in their diets produced eggs with discolored yolks (dirty greenish-yellow). In conclusion, nutrient digestibility, and pancreatic and intestinal enzymes were markedly depressed with the inclusion of SSM in the diets of the fowl. Bicarbonate was the most effective treatment to improve nutrient digestibility and mitigate, to some extent, the poor digestion of SSM.

Animal Feed↗

PubMed2006

Comparison of apparent ileal amino acid digestibility of feed ingredients measured with broilers, layers, and roosters.

The apparent ileal digestibility of amino acids in 7 feed ingredients was determined using broilers, layers, and roosters. The ingredients included 3 cereals (wheat, sorghum, and corn), 3 oilseed meals (canola, cottonseed, and soybean meals), and 1 animal protein meal (meat and bone meal). Dietary protein in the assay diets was supplied solely by the test ingredient. All diets contained 20 g/kg of acid-insoluble ash as an indigestible marker, and each diet was offered ad libitum in mash form to 5 replicate pens of broilers and layers, and 4 replicate pens of roosters. The digestibility coefficients of individual amino acids for wheat, corn, and sorghum were higher (P < 0.05) in broilers than in layers and roosters. The digestibility of most amino acids for corn and sorghum was higher (P < 0.05) in roosters compared with those in layers, whereas the digestibility for wheat in layers and roosters was similar. In general, the digestibility of amino acids in canola meal, cottonseed meal, and meat and bone meal was similar among the 3 classes of chickens. The digestibility of amino acids in soybean meal was higher (P < 0.05) for layers compared with those for broilers and roosters but similar between broilers and roosters. These results suggest that the class of chickens significantly influenced the apparent ileal digestibility of amino acids in some feed ingredients.

Amino Acids↗

PubMed2007

A comparison of methods to determine amino acid digestibility of feed ingredients for chickens.

Two experiments were conducted to compare standardized ileal amino acid (AA) digestibility in 7- and 21-d-old chicks and true AA digestibility as determined by the precision-fed cecectomized rooster assay for several ingredients used in poultry feeds. Diets were formulated to contain soybean meal, cottonseed meal, poultry by-product meal, and fish meal in experiment 1 and corn, wheat, soybean meal, poultry by-product meal, feather meal, and fish meal in experiment 2 as the sole sources of protein. Celite, used as an indigestible marker, was added at 1.5% of the diet. The test diets were fed ad libitum to broiler chicks from 0 to 7 d of age in experiment 1 and from 4 to 7 and 17 to 21 d of age in experiment 2. Ileal digesta samples were collected after euthanizing the birds at 7 d of age in experiment 1 and at 7 and 21 d of age in experiment 2. Additionally, cecectomized, Single-Comb White Leghorn roosters were used for crop intubation of the test diets for determination of true AA digestibility. In experiment 1, AA digestibility of all ingredients tested was significantly lower at 7 d of age than when determined by the rooster assay. In experiment 2, no differences were detected between AA digestibility at 7 or 21 d of age in the chick assay for the majority of the indispensable AA. However, the AA digestibility coefficients obtained by the chick assay at 7 d and, in some cases, at 21 d of age, were significantly lower than those obtained by the rooster assay. In conclusion, there were differences in the AA digestibility coefficients obtained through the chick and the rooster assays. Such discrepancies could be associated with an age effect or the methodological differences between both methods.

Amino Acids↗

PubMed1998

In vitro digestion of proteins in human milk fortifiers and in preterm formula.

BACKGROUND: Knowledge about the digestibility of the proteins in new products designed for feeding preterm infants is limited. The purpose of this study was to observe in vitro the hydrolysis of the bovine and human whey proteins in such products. METHODS: Proteins in human milk, in human milk fortifiers (Presemp [Semper AB, Stockholm, Sweden] and Enfamil [Mead Johnson, Evansville, IN, U.S.A.] human milk fortifiers), in preterm formulas (Similac Special Care [Ross, Columbus, OH, U.S.A.] and Enfalac [Mead Johnson]), and whey protein concentrates with varying degrees of denaturation were digested by duodenal juice from healthy preterm infants, from a 3-year-old child, and from adults. Digestion was studied in vitro using polyacrylamide gradient gel electrophoresis, electroimmunoassay, and nonprotein nitrogen analysis. RESULTS: Casein was the protein most rapidly degraded in all products. Human and bovine whey proteins were more slowly digested; as much as 68% of human lactoferrin was still immunoreactive after 40 minutes of digestion. The corresponding figure for bovine serum albumin was 24-69%; for B-lactoglobulin, 20-40%; for bovine alpha-lactalbumin, 20-51%; and for human alpha-lactalbumin, 41%. Contrary to common belief, digestibility of bovine whey proteins decreased with a high degree of denaturation of the proteins. CONCLUSIONS: Bovine whey proteins in human milk fortifiers and in preterm formulas are relatively slowly digested in vitro by normal duodenal juice. The results may have implications for the design of products for feeding preterm infants.

Adult↗

PubMed2004

The evolution of phylogenetic differences in the efficiency of digestion in ruminants.

This study investigates, for the first time (to our knowledge) for any animal group, the evolution of phylogenetic differences in fibre digestibility across a wide range of feeds that differ in potential fibre digestibility (fibre to lignin ratio) in ruminants. Data, collated from the literature, were analysed using a linear mixed model that allows for different sources of random variability, covariates and fixed effects, as well as controlling for phylogenetic relatedness. This approach overcomes the problem of defining boundaries to separate different ruminant feeding styles (browsers, mixed feeders and grazers) by using two covariates that describe the browser-grazer continuum (proportion of grass and proportion of browse in the natural diet of a species). The results indicate that closely related species are more likely to have similar values of fibre digestibility than species that are more distant in the phylogenetic tree. Body mass did not have any significant effect on fibre digestibility. Fibre digestibility is estimated to increase with the proportion of grass and to decrease with the proportion of browse in the natural diet that characterizes the species. We applied an evolutionary model to infer rates of evolution and ancestral states of fibre digestibility; the model indicates that the rate of evolution of fibre digestibility accelerated across time. We suggest that this could be caused by a combination of increasing competition among ruminant species and adaptation to diets rich in fibre, both related to climatically driven environmental changes in the past few million years.

Animals↗

PubMed1995

Investigations on preileal digestion of starch from grain, potato and manioc in horses.

In this study preileal starch digestibility of starchy feeds (oats, corn, barley, potatoes, manioc) was determined in seven jejunofistulated horses. The grains were fed whole (oats, corn), rolled (oats, barley), crushed, ground and expanded (corn); the potatoes were fresh, the manioc rolled. Ground corn was also fed in combination with amylase. The feeds were fed partly isolated or in combination with alfalfa meal or hay (Table 1). At least four horses with a cannula in the terminal jejunum were used for each diet. Two meals per day were offered at 12 h intervals. The starch intake was mostly about 2 g/kg bw/meal, except one period with oats (3.9 g starch/kg bw) and with expanded corn (1.4 g/kg bw). Jejunal chyme was postprandially collected 11 times (from 1st to the 11th h after the morning meal for 15 min). Starch was determined polarimetrically. The preileal digestibility of starch was calculated by the marker method (chronic oxide 0.25% DM) and by estimating the total jejunoileal chyme flow during 12 h postprandially extrapolating the sample volume from the 15 min sampling periods. The results of both methods agreed quite well. Preileal digestibility of oat starch (80-90%) was (independent of doses or preparation or of the combination with hay, Table 4) significantly higher than that of whole or crushed corn (30%) or barley (26%). Grinding of corn significantly increased preileal digestibility to 51%, expanding to 90%. The addition of amylase improved digestion of ground corn by 10% (absolute). The preileal digestibility of potato or manioc was less than 10%. Individual factors in the horse (chewing intensity, amylase activity) had also considerable influence on preileal starch digestibility.

Animals↗

PubMed2005

Stability of the major allergen Brazil nut 2S albumin (Ber e 1) to physiologically relevant in vitro gastrointestinal digestion.

The major 2S albumin allergen from Brazil nuts, Ber e 1, was subjected to gastrointestinal digestion using a physiologically relevant in vitro model system either before or after heating (100 degrees C for 20 min). Whilst the albumin was cleaved into peptides, these were held together in a much larger structure even when digested by using a simulated phase 1 (gastric) followed by a phase 2 (duodenal) digestion system. Neither prior heating of Ber e 1 nor the presence of the physiological surfactant phosphatidylcholine affected the pattern of proteolysis. After 2 h of gastric digestion, approximately 25% of the allergen remained intact, approximately 50% corresponded to a large fragment of M(r) 6400, and the remainder comprised smaller peptides. During duodenal digestion, residual intact 2S albumin disappeared quickly, but a modified form of the 'large fragment' remained, even after 2 h of digestion, with a mass of approximately 5000 Da. The 'large fragment' comprised several smaller peptides that were identified, by using different MS techniques, as deriving from the large subunit. In particular, sequences corresponding to the hypervariable region (Q37-M47) and to another peptide (P42-P69), spanning the main immunoglobulin E epitope region of 2S albumin allergens, were found to be largely intact following phase 1 (gastric) digestion. They also contained previously identified putative T-cell epitopes. These findings indicate that the characteristic conserved skeleton of cysteine residues of 2S albumin family and, particularly, the intrachain disulphide bond pattern of the large subunit, play a critical role in holding the core protein structure together even after extensive proteolysis, and the resulting structures still contain potentially active B- and T-cell epitopes.

2S Albumins, Plant↗

PubMed1989

Factors determining the digestive efficiency of the domesticated donkey (Equus asinus asinus).

Factors determining the digestive efficiency of donkeys were studied in animals fed either a low quality roughage (wheat straw: 77.1% neutral detergent fibre, 2.8% crude protein) or a high quality forage (alfalfa hay: 47.5% neutral detergent fibre, 22.7% crude protein). The neutral detergent fibre (NDF) intake when fed wheat straw was 1693 +/- 268 g animal-1 day-1, 10% higher than when fed alfalfa hay. Digestive coefficient of NDF and acid detergent fibre (ADF) when fed wheat straw amounted to 50.9 +/- 4.9 and 42.0 +/- 4.1% respectively. NDF and ADF apparent digestibilities and mean retention times (37.7 +/- 1.7 and 36.4 +/- 3.2 h respectively) were not significantly different (P greater than 0.05) between the two diets. The donkey appears to digest cell wall constituents as efficiently as the Bedouin goat when on low quality roughage, but less efficiently when fed alfalfa hay. Its energy digestibility is, however, as high as that reported for the Bedouin goat. The donkey's high energy digestibility is related to its capacity to digest soluble food components more efficiently than the ruminant. The mean retention time in the donkey is shorter than in the Bedouin goat and is consistent with its capacity to compensate for a lower quality diet by increasing its intake rate. Recycling of urea in donkeys maintained on wheat straw amounted to 75.5 +/- 13.0% of the entry rate. A decrease in the rate of renal urea filtration, coupled with an increase in the fraction reabsorbed, increased the retention of nitrogenous waste and permitted recycling of nitrogen into the gut.

Animal Feed↗

PubMed1999

Symbiosis of Aeromonas veronii biovar sobria and Hirudo medicinalis, the medicinal leech: a novel model for digestive tract associations.

Hirudo medicinalis, the medicinal leech, is applied postoperatively in modern medicine. Infections by Aeromonas occur in up to 20% of patients unless a preemptive antibiotic treatment is administered. The associated infections demonstrate the need for a better understanding of the digestive tract flora of H. medicinalis. Early studies reported the presence of a single bacterial species in the digestive tract and suggested that these bacteria were endosymbionts contributing to the digestion of blood. In this study, we cultivated bacteria from the digestive tract and characterized them biochemically. The biochemical test results identified the isolates as Aeromonas veronii biovar sobria. This species identification was supported by sequence comparison of a variable region of the genes coding for 16S rRNA. In a colonization assay, a rifampin-resistant derivative of a symbiotic isolate was fed in a blood meal to H. medicinalis. The strain colonized the digestive tract rapidly and reached a concentration similar to that of the native bacterial flora. For the first 12 h, the in vivo doubling time was 1.2 h at 23 degreesC. After 12 h, at a density of 5 x 10(7) CFU/ml, the increase in viable counts ceased, suggesting a dramatic reduction in the bacterial growth rate. Two human fecal isolates, identified as Aeromonas hydrophila and A. veronii biovar sobria, were also able to colonize the digestive tract. These data demonstrate that the main culturable bacterium in the crop of H. medicinalis is A. veronii biovar sobria and that the medicinal leech can be used as a model for digestive tract association of Aeromonas species.

Aeromonas↗

PubMed2005

Energy costs of blood digestion in a host-specific haematophagous parasite.

Fleas consume and digest blood from their hosts. We hypothesized that the energy costs of digestion of blood by fleas is dependent on the host species. To test this hypothesis, we studied CO2 emission, a measure of energy expenditure, during digestion of a blood meal taken by Parapulex chephrenis from a preferred (Acomys cahirinus) and a non-preferred (Gerbillus dasyurus) host. We predicted that the energy cost of digestion would be lower for A. cahirinus blood than that for G. dasyurus. Male and female fleas consumed similar amounts of blood per unit body mass, independent of host species. Our prediction was supported in that fleas expended significantly more energy digesting blood of G. dasyurus than blood of A. cahirinus. We also found CO2 emission rates of fed fleas were higher than those of unfed fleas and differed significantly among stages of blood digestion when a flea fed on G. dasyurus but not when it fed on A. cahirinus. When fed on G. dasyurus, fleas spent less energy during earlier than later stages of digestion.

Analysis of Variance↗

PubMed2006

Sex differences in food intake and digestive constraints in a nectarivorous bird.

Sex-specific foraging behaviour might be influenced by digestive constraints. However, evidence for sex differences in digestive performance is limited. Various physiological traits are known to be body size dependent. Therefore, we hypothesized that body size differences between male and female birds may lead to differences in their digestive characteristics. We predicted that if food intake and digestive functions are only governed by body mass, then males that are heavier than females would have higher food intake, food assimilation efficiency and gut transit time, but not after controlling for the effect of body mass. We fed a diet of equicaloric solutions of sucrose and a 1:1 mixture of glucose and fructose (hexose mixture) solutions to Palestine sunbirds (Nectarinia osea). When fed sucrose solutions, males had longer transit times but similar absorption efficiencies as females. Transit times, corrected for differences in body mass and food intake, were still longer in males than in females when fed on sucrose solutions. The sex-specific differences in transit time disappeared when the birds were fed the hexose mixture. Our results suggest that males take longer to digest than females when fed on sucrose-rich nectars as opposed to hexose-rich nectars, and therefore can allow themselves a relatively lower digestive capacity. This may suggest sex-specific co-evolution of sunbirds within mixed plant communities, which have both sucrose- and hexose-rich nectar-producing plants. Furthermore, future studies on digestion in birds may pay attention to sex-specific differences.

Animals↗

PubMed2002

Increased blood oxygen affinity during digestion in the snake Python molurus.

Many snakes exhibit large increases in metabolic rate during digestion that place extensive demands on efficient oxygen transport. In the present study, we describe blood oxygen affinity following three weeks of fasting and 48 h after feeding in the Burmese python (Python molurus). We also report simultaneous measurements of arterial blood gases and haematological parameters. Arterial blood was obtained from chronically implanted catheters, and blood oxygen-dissociation curves were constructed from oxygen content measurements at known oxygen partial pressure (P(O(2))) values at 2% and 5% CO(2). Arterial pH remained constant at approximately 7.6 after feeding, but digestion was associated with an approximately 6 mmol l(-1) increase in [HCO(3)(-)], while CO(2) partial pressure (P(CO(2))) increased from 2.21+/-0.13 kPa in fasted animals to 2.89+/-0.17 kPa at 48 h after feeding. Blood oxygen affinity in vivo was predicted on the basis of pH in vivo and the blood oxygen-dissociation curves obtained in vitro. The blood oxygen affinity in vivo increased during digestion, with P(50) values decreasing from 4.58+/-0.11 kPa to 3.53+/-0.24 kPa. This increase was associated with a significant decrease in the red blood cell [NTP]/[Hb(4)] ratio (relationship between the concentrations of organic phosphates and total haemoglobin) and a significant decrease in mean cellular haemoglobin content, which is indicative of swelling of the red blood cells. Our data for blood oxygen affinity and arterial oxygen levels, together with previously published values of oxygen uptake and blood flows, allow for a quantitative evaluation of oxygen transport during digestion. This analysis shows that a large part of the increased metabolism during digestion is supported by an increased venous extraction, while arterial P(O(2)) (Pa(O(2))) and haemoglobin saturation do not vary with digestive status. Thus, we predict that venous P(O(2)) (Pv(O(2))) is reduced from a fasting value of 5.2 kPa to 1.6 kPa during digestion.

Animals↗