Passage Rate (passage + rate)

Distribution by Scientific Domains


Selected Abstracts


Denil fishway utilization patterns and passage of several warmwater species relative to seasonal, thermal and hydraulic dynamics

ECOLOGY OF FRESHWATER FISH, Issue 4 2001
C. M. Bunt
Abstract , Two different Denil fishways on the Grand River, Ontario, were used as check-points to evaluate the upstream movement of fishes past a low-head weir and to examine the proportions and inferred swimming performance of non-salmonid warmwater fishes that used each fishway type. Traps installed at fishway exits were used to collect fish during 24-hour sampling periods, over 40,51 days each year, from 1995 to 1997. Passage rates, size selectivity, water temperature, water velocity and turbidity for the periods of maximum passage for each year were examined. General species composition from trap samples shifted from catostomids to cyprinids to ictalurids to percids and centrarchids, with some overlap, as water temperatures increased from 8 °C to 25 °C in the spring and early summer. Water depths, and therefore water velocities in each fishway, were independent of river discharge due to variable accumulations of debris on upstream trash-racks. Relationships between the water velocity and the swimming and position-holding abilities of several species emerged. Turbidity was directly related to river discharge and precipitation events, and many species demonstrated maximum fishway use during periods of increased turbidity. This study 1) provided evidence of strongly directional upstream movements among several species that were previously considered non-migratory and 2) describes physical and hydraulic conditions during fishway use for 29 non-salmonid fish species., [source]


Racial Fractionalization and School Performance

AMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 2 2010
Joshua C. Hall
The literature on racial "peer effects" suggests that diversity improves at least some students' school performance. However, a literature in economic development posits that diversity may negatively affect school performance by undermining the efficient provision of education. This article empirically tests this claim, which we call the "public goods channel," by examining the relationship between racial diversity and student performance in Ohio's school districts. We find that moving from a completely homogenous school district to one in which two racial groups have equal population shares is associated with a 7,17.5 percentage point decline in the passage rate on the state math exam, holding per pupil spending across districts constant. These results suggest that racial diversity is negatively associated with school performance but that the public goods channel is not responsible for this relationship. [source]


The effect of dietary ratios of corn silage and alfalfa hay on carbohydrate digestion and retention time of feed particles in the gastrointestinal tract of steers

ANIMAL SCIENCE JOURNAL, Issue 5 2009
Taketo OBITSU
ABSTRACT Four Holstein steers fitted with duodenal cannula were used in a 4 × 4 Latin square design to investigate the effect of the combination of corn silage (CS) and alfalfa hay (AH) in different ratios on the ruminal and intestinal digestion of carbohydrates and feed particle passage rate. Steers were fed mixed diets containing both CS and AH in ratios of 80:20, 60:40, 40:60 and 20:80 on a dry matter basis at 95% of ad libitum feed intake. The increase of AH proportion in diets increased dry matter intake and ruminal digestion of dry matter, non-fiber carbohydrate, neutral and acid detergent fiber linearly. Ruminal digestibility of neutral detergent fiber showed a quadratic response, and total digestibility increased linearly with increasing AH proportion. Digestibility of acid detergent fiber in the rumen was not affected by the dietary treatments, but the total tract digestibility increased as the AH proportion increased. Mean retention time of feed particles in total compartment increased when the AH proportion increased from 20% to 60%, but decreased with further increase of the AH proportion. These results indicate that moderate combinations of CS and AH have an associative effect on ruminal fiber digestion, modifying particle movement in the rumen. [source]


Avian fruit consumption and seed dispersal in a temperate Australian woodland

AUSTRAL ECOLOGY, Issue 2 2002
Margaret C. Stanley
Abstract The effectiveness of avian fruit consumers as seed dispersers of fleshy-fruited plants was studied in a temperate woodland community. As a consequence of the short and overlapping fruiting phenologies of fleshy-fruited plant species in temperate regions of Australia, there are very few avian species that are true specialist frugivores. The relative importance of bird species as fruit consumers was investigated, and how their foraging activities, movements and gut treatment of seeds affected dispersal of viable seeds away from the parent plant was examined. Fruit consumption and consumer seed dispersal capacity were assessed in this study through faecal analyses and by testing the viability of seeds that had passed through the gut of avian consumers. Behavioural observations enabled us to determine the consumption rates of, and quantities of fruit consumed by, various bird species and the amount of time spent feeding. Silvereyes (Zosterops lateralis) were the dominant fruit consumers in the community, although 19 bird species were either observed consuming fruit or provided faecal samples that contained fruit. Silvereyes had a high local abundance at the site and more than 90% of silvereyes'faecal samples contained the seeds of fruiting plants (n = 409). Large numbers of fruit were consumed per visit by silvereyes, particularly for Rhagodia parabolica (fragrant saltbush). Silvereyes consumed an average of four R. parabolica fruit per 5 s and up to a maximum 40 fruit per visit. Viability was high for seeds recovered from silvereyes'faeces (R. parabolica, 94.4% viable; Hymenanthera dentata, 100% viable). However, the number of seeds per faecal sample was high for R. parabolica, which may result in density-dependent seed mortality. Gut passage rate for silvereyes fed R. parabolica fruit in captivity was 31.5 ± 1.9 min. Silvereyes remained at fruiting plants for very short periods (average 50-60 s) and in most cases moved away from the parent plant, primarily toward canopy trees. Given the short visit duration of silvereyes, individuals would have left the parent plant well before seeds passed through the gut. Rhagodia parabolica fruit was consumed by a large number of bird species in the community, including species often thought of as exclusively insectivorous or nectarivorous. These species are likely to disperse viable R. parabolica seeds into microhabitats different from those visited by silvereyes. [source]


Receptor-mediated transcytosis of botulinum neurotoxin A through intestinal cell monolayers

CELLULAR MICROBIOLOGY, Issue 2 2008
Aurélie Couesnon
Summary Botulism is mainly acquired by the oral route, and botulinum neurotoxin (BoNT) escapes the gastrointestinal tract by crossing the digestive epithelial barrier prior to gaining access to the nerve endings. Here, we show that biologically active BoNT/A crosses intestinal cell monolayers via a receptor-mediated transcytosis, including a transport inhibition at 4°C and a passage at 37°C in a saturable manner within 30,60 min. BoNT/A passage rate was about 10-fold more efficient through the intestinal crypt cell line m-ICcl2, than through the carcinoma Caco-2 or T84 cells, and was not increased when BoNT/A was associated with the non-toxic proteins (botulinum complex). Like for neuronal cells, BoNT/A binding to intestinal cells was mediated by the half C-terminal domain as tested by fluorescence-activated cytometry and by transcytosis competition assay. A ,double receptor model' has been proposed in which BoNT/A interacts with gangliosides of GD1b and GT1b series as well as SV2 protein. Gangliosides of GD1b and GT1b series and recombinant intravesicular SV2-C domain partially impaired BoNT/A transcytosis, suggesting a putative role of gangliosides and SV2 or a related protein in BoNT/A transcytosis through Caco-2 and m-ICcl2 cells. [source]


Digestive plasticity in Mallard ducks modulates dispersal probabilities of aquatic plants and crustaceans

FUNCTIONAL ECOLOGY, Issue 3 2005
I. CHARALAMBIDOU
Summary 1The consequences of plastic responses of the avian digestive tract for the potential of birds to disperse other organisms remain largely uninvestigated. 2To explore how a seasonal diet switch in Mallard (Anas platyrhynchos L.) influences their potential to disperse plants and invertebrates, we recorded the retention time of markers, following exposure to two diets of contrasting digestibility (trout chow vs seeds). 3We then recorded the retrieval and germination of Fennel Pondweed (Potamogeton pectinatus L.) seeds and Brine Shrimp (Artemia franciscana Kellogg) cysts ingested by the same birds. 4Gut passage rates of markers were increasingly longer in birds on the seed-based, high-fibre diet and shorter in birds on the animal-based, low-fibre one. 5Propagule digestibility, and thus survival to gut passage, differed between diet groups, with more seeds and fewer cysts retrieved from ducks on the animal-based diet. Germination decreased with retention time, but was not affected by diet. 6Differences in passage rates of markers but not of seeds and cysts suggest no change in dispersal distances of plants and invertebrates between seasons, while differences in digestibility would affect the numbers of propagules dispersed. [source]


Studies on feed digestibilities in captive Asian elephants (Elephas maximus)

JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 3-4 2003
M. Clauss
Summary In order to test the suitability of the horse as a nutritional model for elephants, digestibility studies were performed with six captive Asian elephants on six different dietary regimes, using the double marker method with acid detergent lignin as an internal and chromium oxide as an external digestibility marker. Elephants resembled horses in the way dietary supplements and dietary crude fibre content influenced digestibility, in calcium absorption parameters and in faecal volatile fatty acid composition. However, the absolute digestibility coefficients achieved for all nutrients are distinctively lower in elephants. This is because of much faster ingesta passage rates reported for elephants. No answer is given to why elephants do not make use of their high digestive potential theoretically provided by their immense body weight. Differences in volatile fatty acid concentrations between these captive elephants and those reported from elephants from the wild are in accord with a reported high dependence of free-ranging elephants on browse forage. Zusammenfassung Untersuchungen zur Verdaulichkeit von Futtermitteln bei Asiatischen Elefanten (Elephas maximus) Um zu überprüfen, ob das Pferd als ernährungsphysiolgisches Modelltier für Elefanten herangezogen werden kann, wurden Verdaulichkeitsstudien an sechs im Zoo gehaltenen Indischen Elefanten mit sechs verschiedenen Futterrationen durchgeführt. Dabei wurde die Doppelindikatormethode mit Lignin als internem und Chromoxid als externem Marker verwendet. Elefanten ähnelten Pferden hinsichtlich der Art und Weise, wie sich Ergänzungsfuttermittel und der Rohfasergehalt der Ration auf die Verdaulichkeit auswirkten, hinsichtlich der Kalziumabsorption, und hinsichtlich der Zusammensetzung der flüchtigen Fettsäuren im Kot. Die von Elefanten erzielten absoluten Verdaulich-keitswerte sind jedoch für alle Nährstoffe deutlich niedriger als bei Pferden, was auf die schnellere Passage der Ingesta durch den Verdauungstrakt der Elefanten zurückzuführen ist. Die Frage, warum Elefanten ihr großes Potential zu hohen Verdauungleistungen nicht ausnutzen, das ihnen theoretisch aufgrund ihrer immensen Körpermasse gegeben ist, ist noch nicht beantwortet. Unterschiede in den Konzentrationen von flüchtigen Fettsäuren im Kot zwischen diesen Zoo-Elefanten und Elefanten aus freier Wildbahn spiegeln den hohen Laubanteil in der Nahrung freilebender Tiere wieder. [source]