An excitatory state generated during feeding in the locust, Chortoicetes terminifera

Various sequences of 2 μl drops of 1·0 M sucrose and water were applied directly to the mouthparts of restrained adults of the locust Chortoicetes terminifera which had been deprived of all food for 24 hr, and the number of drops consumed was recorded. Locusts fed either single drops of sucrose solution and water in alternation or single drops of sucrose solution alternated with groups of four consecutive drops of water, consumed larger total volumes than locusts fed only drops of water or locusts offered water after having been fed partially or wholly to repletion with 1·0 M sucrose. Towards the end of meals consisting of repeated cycles of one drop of sucrose solution and four drops of water, locusts consumed the one or two drops of water which followed a sucrose drop more quickly than the drop which preceded it. Furthermore, a few locusts which received this treatment terminated their meal while either a drop of sucrose solution or the water drop which immediately followed the sucrose drop was in contact with their mouthparts. The findings provide strong evidence that stimulation received during ingestion of sucrose induces, in addition to an immediate excitatory effect on the feeding system, a perseverating state of neural excitation which, for a short time afterward, increases the chance that the insect will ingest water.     

Sensory adaptation and the regulation of meal size in the Australian plague locust, Chortoicetes terminifera

Adults of Chortoicetes terminifera consumed larger meals of sucrose solution, applied as drops directly to their mouthparts, than of water. Meal size increased with increasing sucrose concentration up to 0·5 M but meals of 1·0 M sucrose were of lower volume. Locusts fed so that there was a short interval between each successive drop of sugar solution consumed greater volumes than those fed continuously, which indicates that sensory adaptation plays a part in bringing about the termination of meals of sugar solutions. Meals of water were not increased in size by discontinuous application.     

Evaluating the Impact of Inadequate Meal Consumption on Insulin-Related Hypoglycemia in Hospitalized Patients

ObjectiveMeal intake is sometimes reduced in hospitalized patients. Meal-time insulin administration can cause hypoglycemia when a meal is not consumed. Inpatient providers may avoid ordering meal-time insulin due to hypoglycemia concerns, which can result in hyperglycemia. The frequency of reduced meal intake in hospitalized patients remains inadequately determined. This quality improvement project evaluates the percentage of meals consumed by hospitalized patients with insulin orders and the resulting risk of postmeal hypoglycemia (blood glucose [BG] <70 mg/dL, <3.9 mmol/L).MethodsThis was a retrospective quality improvement project evaluating patients with any subcutaneous insulin orders hospitalized at a regional academic medical center between 2015 and 2017. BG, laboratory values, point of care, insulin administration, diet orders, and percentage of meal consumed documented by registered nurses were abstracted from electronic health records.ResultsMeal consumption ≥50% was observed for 85% of meals with insulin orders, and bedside registered nurses were accurate at estimating this percentage. Age ≥65 years was a risk factor for reduced meal consumption (21% of meals 0%-49% consumed, P < .05 vs age < 65 years [12%]). Receiving meal-time insulin and then consuming only 0% to 49% of a meal (defined here as a mismatch) was not rare (6% of meals) and increased postmeal hypoglycemia risk. However, the attributable risk of postmeal hypoglycemia due to this mismatch was low (4 events per 1000) in patients with premeal BG between 70 and 180 mg/dL.ConclusionThis project demonstrates that hospitalized patients treated with subcutaneous insulin have a low attributable risk of postmeal hypoglycemia related to inadequate meal intake.     

Regulation of water ingestion by the locust, Chortoicetes terminifera: the effect of injections into the haemolymph

Adults of the locust Chortoicetes terminifera which had been deprived of water for 24 h took larger 'meals' of water than insects which had been deprived for 2 h. Water or dilute solutions of NaCl injected into the kaemcoel reduced the amount of water ingested by 24-h, deprived locusts. Injections of more concentrated solutions of NaCl (0.5 m) or glycerol (1.0m) increased the water intake of 2-h deprived locusts. Water injections into 24-h deprived locusts did not reduce their responsiveness to sucrose and it is concluded that haemolymph osmotic pressure plays an important role in determining the specific responsiveness of C. terminifera to water. The time course of the effects of injection indicates that the effects of haemolymph osmotic pressure on water responsiveness are mediated neurally. Injections of water into 24-h deprived insects caused a marked reduction in the sizes of their meals of seedling wheat. It is suggested that the mechanisms responsible for the regulation of water intake might limit total intake when locusts have access only to fresh vegetation of high water content.     

The control of meal termination in the locust

The relationship between the amount eaten during a meal, meal duration and ingestion rate was investigated in the locust, Locusta migratoria (L.). The results suggested a relatively simple model for the control of meal termination whereby a variety of exogenous and endogenous factors, including chemosensory stimuli provided by the food, the presence of other locusts nearby, age and deprivation-related factors, are integrated within the central nervous system and together contribute to the level of excitation present at the start of a meal. The amount of excitation determines both the mean rate of ingestion during the meal and the amount of inhibition needed to end the meal. Since much of the inhibitory feedback comes from gut stretch, meal size and mean ingestion rate are positively correlated, in fact increasing proportionally, and, hence, meal duration remains constant. At high levels of excitation, however, ingestion becomes rate limited and meal duration subsequently increases proportionally with meal size. Changes in the rate of ingestion throughout a meal were also investigated. The rate declined exponentially but, unlike in the rat, the initial ingestion rate remained constant with changes in excitation and the decay function varied such that small meals began at the same ingestion rate as large meals but the rate of decline was subsequently faster.     

Feeding behaviour of artificially reared Romane lambs

A consequence of increasing litter size in sheep is that a portion of the lambs have to be reared artificially. Detailed information about the pattern of milk consumption of artificially reared lambs would help improve their management. The purpose of this study is to describe the individual and group feeding behaviour of 94 Romane artificially reared lambs from 5 to 28 days of age using an electronic automatic lamb feeder. Animals were located in four pens of 8 to 15 lambs of similar age with one teat per pen. They were fed ad libitum. In our experimental situation (group rearing, continuous lightning) on average a lamb made 1.4±0.7 visits to the teat per meal and 9.5±3 meals per day. Mean meal duration was 247±158 s and the mean daily time spent feeding was 38±25 min. The mean quantity of milk intake was 176±132 ml per meal and 1.68±0.8 l per day. With age, the number of daily meals and their duration decreased while the quantity of milk consumed per meal and per day increased. Females tended to make more visits to the teat per meal and perform more meals per day but their milk consumption per meal was lower. The feed conversion ratio was 1.36±0.2. Synchrony in feeding (group meal) was estimated as the percentage of lambs that wanted to access the teat within the same short period (relative group meal size). On average 65% of lambs in the pen wanted to access the teat within the same period, but for 35% of group meals the relative group meal size was >90%. There was no consistency in the order in which lambs accessed the teat during a group meal. Our evaluation suggested that electronic automatic lamb feeders are tools that can provide, on a large scale, data describing the feeding behaviour of artificially reared lambs. It is then possible to study factors influencing these traits in order to improve the outcome of artificially reared lambs.     

Pre-meal water consumption reduces meal energy intake in older but not younger subjects

Objective: To determine whether the consumption of water 30 minutes before an ad libitum meal reduces meal energy intake in young and older adults. Research Methods and Procedures: Healthy, non‐obese young (n = 29; age, 21 to 35 years) and older (n = 21; age, 60 to 80 years) individuals were provided with an ad libitum lunch meal on two occasions. Thirty minutes before the lunch meals, subjects were given either a water preload (WP: 375 mL, women; 500 mL, men) or no preload (NP). Energy intake at the two lunch meals was measured. Visual analog scales were used to assess changes in hunger, fullness, and thirst during the meal studies. Results: There was no significant difference in meal energy intake between conditions in the young subjects (892 + 51 vs. 913 ± 54 kcal for NP and WP, respectively; p = 0.65). However, meal energy intake after the WP was significantly reduced relative to the NP condition in the older subjects (682 + 53 vs. 624 ± 56 kcal for NP and WP, respectively; p = 0.02). This effect was caused primarily by the reduction in meal energy intake after water consumption in older men. Hunger ratings were lower and fullness ratings were higher in older compared with younger adults (p < 0.01). Fullness ratings were higher in the WP condition compared with the NP condition for all subjects (p = 0.01). No age differences in thirst were detected during the test meals. Discussion: Under acute test meal conditions, pre‐meal water consumption reduces meal energy intake in older but not younger adults. Because older adults are at increased risk for overweight and obesity, intervention studies are needed to determine whether pre‐meal water consumption is an effective long‐term weight management strategy for the aging population.     

Gastric evacuation of single and multiple meals by piscivorous coho salmon,Oncorhynchus kisutch

Synopsis Gastric evacuation of multiple meals of recently emerged sockeye salmon, Oncorhynchus nerka, consumed by juvenile coho salmon, O. kisutch, were compared with that expected from a single meal evacuation rate model developed for the estimation of food consumption by coho in the field. Significant interaction occurred between meals consumed two hours apart (p<0.001). Evacuation of the first of two meals (29.9% of initial weight remaining) was significantly faster (p<0.05) than that of a single meal (36.1% of initial weight remaining) after four hours, whereas evacuation of the second meal (72.2% of initial weight remaining) was significantly slower (p<0.001) than that of single meals (50.6% of initial weight remaining) after two hours. The total weight of the multiple meal remaining after four (0.191 g), six (0.138 g) and eight (0.070 g) hours averaged within 6% of that predicted by the single meal evacuation model (0.186 g, 0.115 g and 0.073 g, respectively). These data suggest that the stomach evacuation model based on single meals is adequate for estimating the evacuation of prey consumed by continuously feeding coho salmon.     

Influence of sex and immunocastration on feed intake behavior,skatole and indole concentrations in adipose tissue of pigs

Feed intake behavior was studied between 9 weeks of age and slaughter in a total of 36 gilts, 32 immunocastrates, 33 surgically castrated barrows and 33 boars from 36 litters. Consequences for the concentration of substances contributing to off odor of pork (skatole, indole) were evaluated. Animals were kept in groups of 12 pigs of the same sex and treatment and fed ad libitum (13.4 MJ ME, 17% CP, 1.1% lysine). Individual feed intake behavior was recorded continuously by an electronic feeder. Immunocastration was carried out with two injections of Improvac with at least 4 weeks between both injections (1st: 12 to 17 weeks of age, 2nd: 19 to 21 weeks of age). Feed intake/day increased from an average of 0.91 ± 0.02 kg/day up to 3.15 ± 0.04 kg/day before slaughter. This increase was associated with a 50% reduction in the number of meals/day (from 15.8 ± 0.44 to 7.2 ± 0.29 meals/day). The larger meal sizes resulted from an increase in both, the duration of feed intake/meal and the feed intake rate (g/min). In addition, sex and treatment differences were observed: Feed intake in boars was lower than in all other groups due to a reduction in the number of meals/day and in the time spent feeding/day. In females, time spent feeding/day was quite similar to boars, but resulted from a higher number of meals of shorter duration. Barrows had a significantly higher feed intake because of a higher number of meals/day resulting in more time spent feeding/day. The feed intake rate was similar in boars, gilts and barrows and showed an increasing trend during the study, starting from about 15 g/min up to four times the amount. Immunocastration affected feed intake behavior severely, especially the meal size increased dramatically because of higher feed intake rate, which exceeded that of all other groups by 25% at the end of the study. The number of meals/day was not influenced by immunocastration and was almost identical to that of boars. Highest skatole concentrations were measured in fat of boars, whereas indole concentrations were higher in immunocastrates than in all other groups. In gilts and barrows, skatole concentrations were related to growth rate. Additionally, the feeding rate was an important factor explaining the variability in skatole/indole concentrations in adipose tissue. The physiological mechanisms however need further clarification.     

Volume of Protein meals taken by females of the blowfly, Lucilia cuprina: ovarian development-related and direct effects of protein ingestion

Abstract. The effect of the stage of ovarian development on the volumes of meals of the protein-rich material, liver exudate, taken by females of the blowfly, L. cuprina (Wiedemann), was examined using an experimental regime which was designed to isolate the effects of ovarian development from any other more direct effects of protein feeding or deprivation. It was found that volumes of meals taken by females with developing ovaries were little, if any, smaller than the volumes taken by protein-deprived females until quite late in vitellogenesis, at which stage meal size fell abruptly to that of meals taken by gravid females. A direct effect of protein-feeding was also demonstrated, with females that had consumed exudate during the previous few hours taking substantially smaller meals than those that had not done so. This effect was, however, shown to be non-specific in that the recent consumption of an equal volume of concentrated sucrose solution caused a similar reduction in the volume of exudate taken.     

Obese Adolescents Show Impaired Meal Responses of the Appetite‐Regulating Hormones Ghrelin and PYY

Ghrelin and peptide YY (PYY) stimulate hunger and satiety, respectively. The physiology of these hormones during normal meal intake remains unclear. This study was designed to compare the responses of these two hormones to meal intake between lean and obese Hispanic adolescents. A total of 10 obese and 7 lean Hispanic youth, aged 11–14 years, consumed two mixed meals, one small and one large, during which plasma measurements of active and total ghrelin and total PYY were obtained. Obese subjects tended to consume more calories during the small meal than lean subjects, although this did not reach statistical significance. Intake of the small meal significantly suppressed active ghrelin and stimulated PYY levels in the lean subjects, and these changes were further accentuated by the large meals. In obese subjects, the suppression of active ghrelin and stimulation of PYY by caloric intake were blunted. Interestingly, a paradoxical stimulation of active ghrelin levels was noted during the small meals in both lean and obese subjects. This stimulation was not seen during the larger meals in lean subjects, but remained present in the obese subjects. Thus, meal‐related changes in active ghrelin and PYY are blunted in obese as compared to lean Hispanic subjects. This blunting could contribute to the development or worsening of obesity.     

Effects of sucrose concentrations and fly age on feeding responses and survival of female and male western cherry fruit flies, Rhagoletis indifferens

Abstract. The effects of single meals of different sucrose concentrations on feeding responses and survival of 8–24-h-old, 1–2-, 10–12- and 31–36-day-old female and male western cherry fruit flies, Rhagoletis indifferens Curran, were determined. Feeding time and food consumption response patterns in both sexes within age groups were curvilinear. Feeding times increased as sucrose concentrations increased, and were longest when the sucrose concentration was 100% (dry). Consumption of dilute wet sucrose was low, whereas consumption of concentrated wet sucrose was high. However, consumption of dry, 100% sucrose was also low. One to 2-day-old flies of both sexes that had not previously fed consumed more sucrose foods than unfed 8–24-h-old flies and 10–12- and 31–36-day-old flies that had been starved for 16–24 h. Females consumed more than males, but they consumed the same amount as males per mg bodyweight. When fed single 20% and 60% sucrose meals, 1–2-day-old flies survived longer compared to flies in all other age groups, with 31–36-day-old flies surviving shortest. Despite age-related differences in survival, in general, no sex differences in survival were seen in flies fed sucrose within any age groups, or in flies fed sucrose-yeast, cherry juice and honeydew foods. The results suggest that sugar-feeding behaviours and the energy invested in sugar 'seeking' by both sexes of R. indifferens should be the same throughout life.     

Measuring meals: structure of prandial food and water intake of rats

Attempts to understand ingestion have sought to understand the control of meals. The present study evaluated a meal definition that included prandial drinking (drinking-explicit meals). The spontaneous nocturnal intake of male Wistar rats was studied. The meal breakpoint was defined as the interval between feeding or drinking events providing the most stable estimate of meal structure. Alternative breakpoints derived from prevailing methodology, log-survivorship, or frequency histogram analysis of interfeeding intervals without respect to drinking were compared (drinking-naive meals). Threshold interfeeding intervals that accounted for drinking indirectly were evaluated as surrogate breakpoints (drinking-implicit meals). Definitions were compared by determining which criterion better conformed to predictions of satiety. Microstructural differences resulting from the definitions were also studied. Under the drinking-explicit definition, rats averaged nine or ten 13-min meals/night, during which they consumed food and water equally in duration (5-6 min) and quantity (2.3 g). Individual differences were observed in microstructure measures. Meals defined by drinking-informed, but not drinking-naive, methods were followed by the behavioral satiety sequence and by an initially low likelihood of resuming feeding that monotonically increased with time. The drinking-explicit definition uniquely revealed preprandial and postprandial correlations of similar magnitude. Under drinking-informed definitions, food restriction increased meal size, whereas drinking-naive definitions increased meal frequency. Drinking-implicit definitions provided workable approximations of meal frequency and size but inferior estimates of feeding duration, eating rate, and the preprandial correlation. Thus log-survivorship analysis is not appropriate for identifying meal breakpoints, and the consideration of drinking in meal definitions can provide a better estimate of meal structure.     

Patterns of respiration in Locusta migratoria nymphs when feeding

Flow‐through respirometry was used to investigate patterns of respiration of fifth‐instar Locusta migratoria L. nymphs fed a chemically defined, synthetic food. Each animal was recorded for up to 2.7 h, during which they had access to food and water ad libitum, and at least one meal was taken. The start of feeding was coincident with a sudden and rapid rise in respiration. Both carbon dioxide (CO₂) production and oxygen (O₂) consumption rose, the traces for the two gasses showing a high degree of alignment. The end of a meal correlated with a sudden and rapid decrease in respiratory rate towards resting levels. When feeding was interrupted by an intra‐meal pause, respiratory rate tended to drop marginally and then stabilize, before rising rapidly upon the resumption of feeding within the meal. Maximal rates of respiration during feeding represented a 3–4‐fold increase over those at rest. Walking and climbing within the chamber were not associated with any noticeable change in respiratory rate above baseline. When locusts were quiescent between feeding episodes, respiration was steady and continuous, rather than discontinuous. Possible causes for large changes in respiration during feeding are discussed.     

The effect of feeding hierarchy on individual variability in daily feeding of rainbow trout, Oncorhynchus mykiss (Walbaum)

Three groups of rainbow trout, Oncorhynchus mykiss , (initial weight 40 g) were fed one of three rations (low, medium or high) for 73 days. Consumption by individual fish within the three ration groups was measured on four occasions (days 27, 55, 64 and 72) using radiography. Food intake by individual fish varied between days and this variability was expressed using the coefficient of variation (CV). Dominant fish within each ration group were defined as individuals with the greater share of the group meal and these fish had low CVs for food intake indicating relatively little variation in daily consumption. By contrast, the fish which had consumed a low mean proportion of the group meal displayed high CVs for food intake, indicating considerable variability in the sizes of individual meals consumed by these fish. As group ration increased, the range of meal sizes and individual CVs in daily feeding decreased, suggesting that the strength of the feeding hierarchy and the variability in individual consumption decreased as food availability increased. It is suggested that radiography can be used to assess social relationships within groups of fish allowing the assessment of feeding hierarchies in larger groups of fish than would be possible by observational techniques.     

Temporal patterning of feeding by hummingbirds

For five species of hummingbirds in the laboratory, time between meals was related to energy intake on the first meal and rate of energy expenditure between meals. Field observations gave similar results. Average meal sizes were similar at one intake rate independent of food caloric density; females averaged longer bouts than males. When rate of intake was approximately halved, meal duration approximately doubled and volume intake remained similar. We postulate that feeding is initiated when crop contents reach a lower threshold and that feeding is terminated after ingestion of an optimal volume determined by the added weight of the meal.     

Rates of gastric evacuation in piscivorous brown trout, Salmo trutta

SUMMARY. 1. The dry weight of food remaining in the stomachs of piscivorous trout decreased exponentially with time. Gastric evacuation rates increased exponentially with increasing temperature but were unaffected by predator size, meal size or type of fish prey.
2. Mathematical models were developed to estimate both the rate and time for the gastric evacuation of different meal sizes (expressed as dry weight), and were applicable to piscivorous trout of different sizes (length range 10–32 cm) feeding on trout fry or sticklebacks at different temperatures (range 5–18°C).
3. The wet weight of food in the stomachs also decreased exponentially with time, but evacuation rates both increased with temperature and decreased with increasing meal size; the latter relationship occurred because relative rates of water loss from a meal also decreased with increasing meal size. Use of wet or dry weights can therefore lead to different conclusions about the effect of meal size on evacuation rates.
4. When piscivorous trout were fed three consecutive meals of varying size, the models predicted the total dry weight of food left in the stomach, but not the weight remaining for each individual meal. Interactions between meals led to an increase in evacuation rates for meals consumed early in the series and a decrease in evacuation rates for later meals.
5. Evacuation rates for piscivorous trout were compared with those for trout feeding on invertebrates in an earlier study, and were close to those for caddis larvae as prey, higher than those for mealworms and lower than those for a variety of invertebrate prey. Although a great deal is now known about the daily food intake and growth rates of trout feeding on invertebrates, there is little comparable information for piscivorous trout.     

Behavioral components of high-fat diet hyperphagia: meal size and postprandial satiety

Previously, rats fed a high-fat liquid diet (HF) ad libitum consumed more kilocalories and had greater weight gain than rats fed a liquid high-carbohydrate diet (HC) of equivalent energy density (Warwick, Z. S., and H. P. Weingarten. Am. J. Physiol. Regulatory Integrative Comp. Physiol. 269: R30-R37, 1995). The present series of experiments sought to clarify the behavioral expression of HF hyperphagia by comparing HF and HC with regard to meal size and magnitude of postingestive satiety effect. Meal size of HF was greater than HC at 2.3 kcal/ml and also when diets were formulated at 1.15 kcal/ml. In a preload-test meal paradigm, an orally consumed HF preload was less satiating than a calorically equivalent HC preload across a range of preload volumes and intermeal intervals. Sensory-specific satiety was ruled out as an explanation of the relatively greater intake of test meal after an HF preload meal; an intragastrically delivered HF preload was less satiating than intragastric HC. Furthermore, a fat (corn oil emulsion) preload was less satiating than a carbohydrate (sucrose) preload when an evaporated milk test meal was used. These findings indicate that hyperphagia on an HF diet is expressed in increased meal size and decreased intermeal interval.     

Mechanisms regulating salt intake in fifth-instar nymphs of Locusta migratoria

Abstract. Investigations were undertaken into the mechanisms controlling regulation of salt intake in fifth-instar nymphs of Locusta migratoria L. Initially, the pattern of feeding was recorded for 24 h in locusts fed a chemically-defined food either with or without salt. Differences were apparent from the first meal, with smaller meals being eaten more frequently on the salt-free food over the next 8h. As a result, total food intake over the first 8h was similar on the two foods. By 24 h, however, intake of the salt-free food was considerably reduced and the rate of prefeeding rejections was high. Next, following a period of pretreatment (24 or 48 h) on one of these two foods, responses were recorded to glass-fibre discs impregnated with salts, artificial foods differing in salt content, and wheat germ. Haemolymph amino acid titres were also recorded in locusts feeding ad libitum on salt-free or salt-containing food to test the 'metabolic bottleneck' hypothesis for explaining rejection of a salt-free food after a period of feeding on it. Finally, the role of learning was investigated in experiments in which distinctive plant odours and flavours were paired with foods lacking or containing salt. Results across all the experiments indicate that regulation of mineral intake in locust nymphs involves a number of mechanisms, including modulation of locomotory behaviour, innate taste responses and learning. Additionally, there was evidence of a sex difference in salt appetite.     

Nutrient modulation of intestinal gas dynamics in healthy humans: dependence on caloric content and meal consistency

The actions of nutrients on gut transit of liquids and solids have been extensively studied, but the effects of meal ingestion on intestinal gas flow are unexplored. We hypothesized that meals of varying caloric content and consistency modulate gas transit to different degrees. Nine healthy volunteers underwent jejunal perfusion of physiological gas mixtures at 12 ml.min(-1).3 h, with ingestion of nothing (control), water (240 ml), 240-kcal liquid meals, and 240-kcal solid meals at the end of the second hour in separate studies. Gas was quantified from an intrarectal catheter. After an initial lag phase, gas evacuation approached steady state by the end of the fasting period. Solid and liquid caloric meals increased total gas volumes evacuated from 5-40 min after ingestion vs. control studies (P < 0.05). These increases resulted from increased numbers of bolus gas evacuations (P < 0.05), whereas bolus volumes, pressures, and flow rates were similar for all test conditions. Solid and liquid caloric meals elicited similar effects on bolus gas dynamic parameters, whereas water did not affect these measures vs. control (NS, not significant). Both caloric meals and the noncaloric liquid meal increased continuous gas flow, which represented <2% of total gas expulsion. In conclusion, caloric meals promote bolus gas transit in healthy humans, whereas noncaloric liquids have no effect. Solids stimulate early postprandial gas dynamics to the same extent as liquid meals of similar caloric content. Thus modulatory effects of meals on intestinal gas transit depend on their caloric content but not their consistency.