This study evaluated the importance of a correction for amino acids (AA) released into the hindgut on a measure of AA absorption kinetics and tested whether AA absorption kinetics are related to the extent of AA absorption using the growing pig as a model for humans. Thirty-six nine-week-old pigs (22·3 kg) received a diet containing whey protein as the sole protein source for 8 d. Pigs received their last meal containing the indigestible marker titanium dioxide before being euthanised at 1, 2, 3, 4, 6 and 12 h post-feeding. The entire content of each gastrointestinal tract (GIT) region was collected to determine AA released into the hindgut, and the kinetics and extent of AA absorption (uncorrected and corrected for AA entering the hindgut). Amounts of AA released into the hindgut increased over time (e.g. 33 and 180 mg of Glu for 4 and 6 h post-feeding). The corrected apparent amount of each AA absorbed from the GIT lumen after 4 h post-feeding was generally lower (P ≤ 0·05) than the uncorrected counterpart. Differences in both the kinetics and extent of AA absorption were observed across AA. For example, the time to reach half of the apparent AA absorption (T50) was 1·5 and 3·4 h for Met and Arg, respectively, whereas their extent of apparent absorption was 93 and 73 %. Negative correlations between parameters related to kinetics and the extent of apparent absorption were observed (e.g. for T50 r = −0·81; P < 0·001). The kinetics of AA absorption is related to the extent of AA absorption.

Open conjectures state that, for every $x\in [0,1]$, the orbit $(x_n)_{n=1}^\infty $ of the mean-median recursion

$$ \begin{align*}x_{n+1}=(n+1)\cdot\operatorname{\mathrm{median}}(x_1,\ldots,x_{n})-(x_1+\cdots+x_n),\quad n\geqslant 3,\end{align*} $$

with initial data $(x_1,x_2,x_3)=(0,x,1)$, is eventually constant, and that its transit time and limit functions (of x) are unbounded and continuous, respectively. In this paper, we prove that for the slightly modified recursion

$$ \begin{align*}x_{n+1}=n\cdot\operatorname{\mathrm{median}}(x_1,\ldots,x_{n})-(x_1+\cdots+x_n),\quad n\geqslant 3,\end{align*} $$

first suggested by Akiyama, the transit time function is unbounded but the limit function is discontinuous.

Piloting in the Panama Canal is exceptional as, due to its importance, the functions of the captains of vessels are taken over by pilots. Hence, prior to inauguration of the expanded canal, a limited number of pilots experienced on the existing canal were certified for the transit of Neopanamax vessels by means of planned and innovative individual learning. After this organisational training through operative training, with the implementation of the expanded canal in June 2016, the routine training started. Hence the learning curve in the performance of these manoeuvres will represent the growing skill acquired by both the pilots and the organisation. Given that the learning effect is measurable, this paper has the dual objective of determining two curve models: the organisation operative learning curve model and the routine learning curve model for pilots performing transit manoeuvres in the expanded Panama Canal waterways and the Cocolí and Agua Clara locks. Manoeuvre times in locks and transit in the whole of the canal were followed up continuously in the first 42 months of operation.

Microbiome research in the last two decades has delivered as a key finding that the human intestine hosts a unique and complex ecosystem with many variables affecting the composition of the microbiota and in turn its function in metabolism and immune defence. Hundreds of external (environmental) factors have meanwhile been identified as significantly associated with bacterial biomass and diversity and, amongst these, diet is considered as a key determinant of microbial populations. However, dietary intervention studies, including those with fermentable substrates that have bulk effects on bowel functions, have revealed only very minor effects on overall microbiome composition and usually show only a very few species changing in population size. What that means in the context of hundreds of different species coexisting in competition or mutualism in the human colon is far from understood. This review addresses some of the current limits in research on diet effects by taking anatomical and physiological features of the intestine into consideration. It also provides some recommendations on future human studies needed to assess how the diet influences the microbiome and associated effects on metabolic health.

D+ (high digestion efficiency) and D− (low digestion efficiency) genetic chicken lines selected for divergent digestion efficiency were compared in this experiment. Gizzard functions were tested in terms of digesta mean retention time and reactions to high dilution of a corn diet with 15% coarse sunflower hulls. The corn standard (S) and high fibre (F) experimental diets were given from 9 days of age to chickens from both lines. Besides the measurements of growth efficiencies (9 to 20 days), digestibilities (20 to 23 days) and gut anatomy (0, 9, 29, 42 and 63 days), two digestive transit studies were performed at 9 and 29 days of age. For the transit studies, the S and F diets were labelled with 0.5% TiO2 and 1% Cr-mordanted sunflower hulls. These diets were fed ad libitum during 3 days, and then the birds were euthanized. The digestive contents were analysed for the determination of marker concentrations and mean retention times (MRTs) in digestive compartments (crop + oesophagus, proventriculus + gizzard, duodenum + jejunum, ileum, rectum + cloaca and caeca) were determined. D+ birds were confirmed as better digesters than D− birds during the growth period, in association with larger gizzard and pancreas, and lighter small intestine in D+ than in D−birds. The MRT in the proventriculus-gizzard system, higher in D+ than in D− birds, was a major factor associated with differences between D+ and D− birds regarding digestion efficiencies and gut anatomy. Diet dilution with fibres reduced differences in digestion efficiencies and proventriculus-gizzard MRT between lines. Differences in gut anatomy between lines tended to disappear after 8 weeks of age. In conclusion, this study showed that MRT in the proventriculus-gizzard system was a major factor associated with genotype differences between the D+ and D− genetic chicken lines selected for divergent digestion efficiency, with longer MRT found in D+ than in D− birds.

Nutrient use by the red panda Ailurus fulgens was measured in animals fed only on their natural bamboo Bashania spanostachya diet. The project was carried out at the field observation station of Yele Natural Reserve in Sichuan, China. Two-week long trials were conducted at monthly intervals from May to November 1995. Results showed that dry matter digestibility differed significantly among seasons and between diets. Digestibilities of dry matter and key nutrients were high in summer–autumn, intermediate in spring and low in winter. Shoots were more easily digested than leaves and exhibited the highest digestibility. These variations were positively correlated with nutrient contents in bamboo. The results also indicated that the red panda poorly processed its bamboo food. This was demonstrated by the lower digestion coefficients of dry matter and nutrients, especially that of cell wall constituents. This implied that microbial digestion only played a minor role in its digestive strategy, similar to the giant panda Ailuropoda melanoleuca, another herbivorous carnivore. In addition, the transit of bamboo through the red panda gut was very rapid (2–4 h). In order to survive on this poor-quality diet, it seems that the red panda has to select high-quality items of bamboo such as tender leaves and shoots. These are ingested in large quantities (over 1.5 kg of fresh leaves and 4 kg of fresh shoots daily) that pass through the digestive tract fairly rapidly so as to maximize nutrient intake.

Five mathematical models were compared to select the most satisfactory model to describe digesta kinetics of solids and fluids in the gastrointestinal tract of buffaloes (Mediterranean bulls), cattle (Friesian bulls) and sheep (Delle Langhe rams) given food at maintenance level, according to a Latin-square arrangement for four consecutive periods of 21 days. Chromium mordanted alfalfa hay and cobalt-ethylenediamine tetraacetic acid were used as nonabsorbable markers and were administered through the rumen cannula in a single dose. Four different isonitrogenous diets (N × 6·25 = 140 g/kg dry matter) with different concentrate:forage ratios (12·5:87·5, 25:75, 37·5:62·5, 50:50) were used.

Faecal chromium and cobalt concentration curves were fitted with five non-linear models: three gamma (G2, G3, G4) age-dependent one-compartment, one gamma age-dependent/age-independent two-compartment (G2G1) and one multicompartment (MC).

Wilcoxon tests on residual sums of squares of the different models for solids showed that MC and G4 gave a better fit than G2G1, G2, G3 for all the data and within the species. The comparison of MC v. G4 did not show any significant difference (P > 0·05) for all the data computed together or within each species. Nevertheless, MC had a higher number of curves with lower residual sums of squares in comparison with G4 and was also able to produce estimates of digesta kinetics in the second compartment.

The cobalt excretion curves for fluids, considering all the data, and only within sheep, showed G4 as the best fitting model. When G4 was compared with other models no significant differences were recorded either for cattle: G4 v. G2 (F = 0·6645), G4 v. G2G1 (P = 0·0620) and for buffalo: G4 v. G2 (P = 0·1575), G4 v.G3(P = 0·0796) and G4 v. G2G1 (P = 0·1641).

It is concluded that the multicompartment model (MC) and G4 model were the best fits for solids and for fluids respectively.

The physiological effects of dietary fibres in humans are due to their physico-chemical properties. However, it is difficult to predict these effects simply by measuring certain characteristics in vitro. Studies in human subjects are still required to assess the effectiveness of new substrates. The aim of the present study in healthy human subjects was to evaluate the effects of two novel fibres, potato (PF) and maize (MF), on fasting and postprandial blood concentrations of carbohydrate and lipid metabolites as well as on stool ouput and transit time. The chemical composition, water-binding capacity (WBC) and fermentative properties of the fibres were also characterized in order to determine their possible involvement in digestive and metabolic effects. Stools, as well as breath and blood samples, were collected after consumption for 1 month of either a basal diet (control) or a basal diet supplemented with fibre (15 g/d). MF resisted fermentation better than PF and had lower digestibility. However, both fibres increased faecal output of dry matter, neutral sugars and water. There was an inverse relationship between stool weight and orofaecal transit time, although only MF significantly reduced transit time. Orocaecal transit was lengthened by PF, probably because of its high WBC. PF ingestion also decreased postprandial plasma levels of total and esterified cholesterol but had no effect on fasting concentrations. In contrast, MF lowered fasting cholesterolaemia and increased free:esterified cholesterol. These particular physiological and fermentative properties suggest that PF and MF would be suitable ingredients in a healthy diet.

A series of 4 × 4 Latin-square digestibility trials was carried out to determine whether there were any differences between different types of equid in their ability to digest diets containing different levels of fibre and protein. The equids (Thoroughbreds, Highland ponies, Shetland ponies and donkeys) were offered one of four molassed diets in turn and these contained different proportions of alfalfa and oat straw: 1·0:0, 0·67:0·33, 0·33:0·67, 0:1, respectively. The apparent digestibility of dry matter (DM), organic matter (OM), gross energy (GE), crude protein (CP), acid-detergent fibre (ADF) and neutral-detergent fibre (NDF) were estimated. The rate of passage of the different diets was measured using Cr-mordanted fibre (Cr-fibre) and Co-ethylene diamine tetra acetic acid.

All animals digested the components of the high-fibre diets less well than those of the low-fibre diets (P < 0·001 for DM, OM, GE, CP and ADF). Donkeys digested fibre more effectively than the other equids (F < 0·01 for ADF and NDF). The gastro-intestinal transit time of the high fibre diets was significantly less than that for the low fibre diets (P < 0·001) and donkeys retained food residues longer than the other equids (P < 0·01).

To investigate diurnal changes in large-bowel metabolism rats were fed once daily on a cooked maize-based diet without or with 200 g wLeat bran/kg diet and containing Cr2O3 as an indigestible marker. After 17 d four rats on each diet were killed at 4, 10, 16 and 22 h postfeeding. Emptying of dry matter (DM) from the stomach occurred by an apparently zero-order process at about 0·5 g/h in both diet groups. Feeding wheat bran had little effect on caecal pH or total short-chain fatty acid (SCFA) concentration but was associated with a marked increase in molar proportion of butyrate and a fall in propionate. There were substantial changes in caecal total SCFA concentration and in the molar proportions of individual SCFA throughout the day but no evidence of an interaction between diet and time interval after feeding. Caecal transit time (TT) was significantly reduced by feeding wheat bran whilst colonic TT was unaffected. Although when averaged across both diets there were no significant time effects on caecal or colonic TT, there was a significant diet × time interaction for caecal TT. The extent of coprophagy was measured. The proportion of stomach DM derived from ingested faeces increased with time interval after feeding but it was always a minor contribution so that in these circumstances coprophagy is unlikely to result in significant bias in estimates of digesta flow-rates or TT.

Rumen degradability of dry matter (DM), organic matter (OM), nitrogen (N), neutral-detergent fibre (NDF), hemicellulose, cellulose and lignin was evaluated with the in situ technique for maize silage and cocksfoot, timothy, fescue, lucerne and meadow hays. The degradability of each of the six forages was studied separately, each forage being used in turn as the main component of the diet offered to four fistulated cows. For each forage 300 g were mordanted with sodium dichromate and placed in the rumen when the same forage was studied. Faecal grab samples were collected to measure the forage transit time. Digestibility was evaluated using both lignin as an indicator and by an in vitro method.

Rumen outflow rate was higher for cocksfoot and lucerne hays than for maize silage and the meadow, timothy and fescue hays (P < 0·01). The effective degradabilities of DM and OM were higher in maize silage, fescue and lucerne than in cocksfoot, timothy or meadow hay (P < 0·01). Effective degradability of N was highest in lucerne and lowest in timothy and meadow hay (P < 0·01). The degradability of NDF, hemicellulose and cellulose for fescue was always the highest of the six forages (P < 0·01; P < 0·05; F < 0·01 respectively).

Rumen outflow rate was statistically correlated with the c value of DM (r = 0·47), N (r = 0·54), NDF (r = 0·43) and hemicellulose (r = 0·43). High correlations were observed between rate constants of degradation of NDF and hemicellulose, cellulose or lignin (0·93, 0·75 and 0·79 respectively). The regression between in vitro and lignin-derived digestibility was highly significant (P < 0·001, r2 = 0·902 residual s.e. 0·017). The multiple regression analysis between lignin-based digestibility and degradability coefficients, effective degradability and coefficients of faecal chromium excretion was highly significant (r = 0·748; residual s.e. = 0·03).