Gastrointestinal motility in relation to spontaneous meal occurrence in domestic fowls

Adjustments of gastric pH, motility and temperature during long-term preservation of stomach contents in free-ranging incubating king penguins

Male king penguins are able to store undigested food in their stomach for up to 3 weeks during their incubation fast, which evidently implies some modification of their digestive process. Using small electronic recorders, we studied the change in gastric pH, motility and temperature during the first week of food storage. The pH could be maintained at values as high as 6 throughout the incubation fast, a pH that is unfavourable for avian gastric proteinase activity. Gastric motility was never completely inhibited but could be markedly reduced. Stomach temperature was maintained at around 38 degrees C. The fact that stomach temperature of incubating birds did not show a daily rhythmic fluctuation as seen in non-breeding birds could be due to temperature constraints on embryo development. Thus the present study demonstrates substantial adjustments of pH and gastric motility in incubating king penguins, which may contribute to the inhibition of digestive gastric processes.

Temporal control of feeding behaviour and its association with gastrointestinal function

This paper summarises knowledge about temporal control of ad libitum feeding in poultry, from minute to minute, hour to hour and day to day, and about how it relates to aspects of gastrointestinal function. Evidence is presented of only loose control over initiation and termination of spontaneous meals, and it is proposed that degrees of hunger and satiety determine probabilities of feeding starting and stopping. Voluntary regulation of food intake can be considered in terms of adjustments in mean meal size, meal frequency or both. Short-term variation is associated more with meal frequency and longer-term changes more with meal size. Short-term adjustments appear to depend more on alimentary control and longer-term adjustments more on metabolic control (not considered here). Long-term changes affecting meal size are associated with changes in capacity of parts of the alimentary tract. Food can accumulate in the crop and gizzard, and meal initiation and termination are associated with varying degrees of emptying and filling of these diverticula during most of the day. Later in the day there is usually a conditioned change to cumulative filling of the crop (and gizzard) with food that is digested overnight. Possible roles of osmo-/chemoreceptors and gut peptides are discussed.

Application of artificial neural networks for prokaryotic transcription terminator prediction

Artificial neural networks (ANN) to predict terminator sequences, based on a feed-forward architecture and trained using the error back propagation technique, have been developed. The network uses two different methods for coding nucleotide sequences. In one the nucleotide bases are coded in binary while the other uses the electron-ion interaction potential values (EIIP) of the nucleotide bases. The latter strategy is new, property based and substantially reduces the network size. The prediction capacity of the artificial neural network using both coding strategies is more than 95%.

Responses of fowls to an operant feeding procedure and its potential use for reducing randomness in meal occurrence

Adult laying hens were tested with increasing and decreasing procurement costs (pecks at a disc) which allowed access to food for unlimited periods. This was done to observe changes in feeding behaviour, to see whether apparent randomness in meal occurrence can be reduced, and, if so, to identify an appropriate fixed ratio (FR) for incorporating in investigations of physiological correlates of hunger and satiety. Daily food intake stayed the same at all but the highest (160 pecks) FR. FR sizes were related negatively to total time feeding and meal frequency, and positively to intermeal interval length, meal size and rate of eating within meals. They were also related positively to meal length, but only weakly so. Frequency distributions of meal and interval lengths, and postprandial correlation coefficients, indicated that randomness in feeding did decline at higher FRs, and FR20 seems the most appropriate schedule for potential use in physiological experiments.

Rates of eating by domestic fowls in relation to changing food deficits

Rates of eating by immature female fowls declined in a curvilinear way in the 30 min after return of food after 0-4 h deprivation. Amounts eaten in the first 5-10 min were related positively to the length of deprivation and were greater with pelleted food than with mash. Times taken by birds to reach a presumed equilibrium between probabilities of feeding starting and stopping, at two consecutive minutes with less than 0.2 g eaten, were related positively to the deprivation period and were greater with mash than with pellets. At these times, however, more had been eaten with pellets than with mash, and none of the deprived birds had eliminated their estimated food deficits. Furthermore, in only one out of ten treatments did birds compensate imbalances completely by the end of the 90 min test. It is proposed that the observed changes in eating rate may reflect interactions between pecking success, increasing fatigue and decreasing hunger. It is also concluded that, while short-term adjustments in feeding may be limited by preabsorptive factors, eventual compensation of imbalances depends on postabsorptive control.