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.     

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.     

Nitrogen partitioning and blood meal utilization by Aedes aegypti (Diptera Culicidae)

The utilization of the blood meal by mosquitoes was investigated by first feeding females quantities of blood ranging from 1 to 5 mg, and then analyzing the faeces for the various by-products of protein catabolism that were subsequently eliminated. The nitrogeneous waste products in order of importance were uric acid, histidine, ammonia and arginine. Only traces of the other amino acids were excreted.The total amount of each faecal substance varied linearly with the quantity of blood ingested, however their relative proportions did not change. Regardless of blood meal size the quantily of uric acid and ammonia produced indicates that about 80% of the non-histidine and arginine amino acids are deaminated and utilized for metabolic purposes other than egg protein synthesis.Most of the histidine and about one half of the arginine content of the blood were excreted as free amino acids, but the other amino acids were lost in trace amounts.Nineteen per cent of the total ingested amino acids was incorporated into soluble yolk proteins and this proportion was constant even for small blood meals that result in a reduction in the numbers of eggs produced.The comparative aspects of nitrogen partitioning and blood meal utilization by haematophagous insects, as well as the factors that affect blood meal utilization and fecundity in A. aegypti are discussed.     

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.     

Development of an artificial diet for the western corn rootworm

Toxicants may cause insects to avoid a bait, and yet bait efficacy is dependent upon insects ingesting it in adequate quantities. Amounts ingested are, in turn, determined by meal frequency, meal durations and ingestion rate within meals, but to date no report has been made of these variables for domestic cockroaches. We report an experiment in which sixth instar German cockroach, Blattella germanica, nymphs were initially able to self-select their protein and carbohydrate intake independently, then daily at the start of the scotophase some insects had their choice of foods replaced by a single treatment food, which varied through the presence or absence of protein, carbohydrate, and insecticide. Insect behaviour was recorded for the following 5 h, and the data were subsequently subjected to bout analysis in order to identify discrete meals. The age of insects in days on first exposure to a treatment food (`age') and the amount of food eaten in the observation period were both recorded and included in the analysis. Amounts eaten were affected by insect age and food nutrient content, but not by the presence of insecticide. Toxicant effects were, however, seen on average meal duration and meal frequency, in interactions with age and food nutrient effects. These results suggest ways in which direct observations of behaviours may lead to improved bait design.     

Lipid metabolism during sequential gonotrophic cycles in large and small female Aedes aegypti

The lipid metabolism was investigated during six gonotrophic cycles of Aedes aegypti. Females of constant body size were analyzed for their total lipid content: large females with a body size of 41.06 (wing length cubed) and small females with 15.63. Their lipid contents at eclosion were compared to lipid values after two days of sugar-feeding, shortly before a blood meal, after oviposition, of their total egg batches, and again before the next blood meal, with intermittent access to sugar for two days for six gonotrophic cycles.Large females transferred most of their pre-blood meal lipid into the ovaries. Their low lipid content after oviposition was restored by synthesis from intermittent sugar meals. After the third gonotrophic cycle, they withheld more and more of the resynthesized lipid in their fat body, thus gradually reducing their fecundity. Since blood consumption was not altered significantly during these six cycles, age-related reduction of fecundity was clearly caused by limitations of yolk lipid.Small females transferred a considerably smaller, but constant segment of sugar-derived lipids to the ovaries. In both size classes, lipid content per oocyte was constant throughout all cycles with 9 mcal/oocyte in large and 7 mcal/oocyte in small females. Total fecundity reached 450 eggs in large and 280 eggs in small females. Large females that were maintained on water without sucrose took large blood meals from which part of the yolk lipid was synthesized. Extrapolations suggest that only one or two additional gonotrophic cycles would be possible without additional carbohydrate sources, despite lipogenesis from blood protein.     

Behavioural contributions to the regulated intake of plant secondary metabolites in koalas

In a given period of time, herbivores often eat less as dietary plant secondary metabolite (PSM) concentrations increase. This reduction in total food intake is interpreted as a need for the herbivore to regulate PSM ingestion in order to avoid toxication. However, regulation of PSM ingestion involves more than the reduction of total intake; it involves an alteration of meal patterns, through a reduction in the number and/or the size of the meals eaten. Despite this, studies of how herbivores alter their meal patterns when offered varying concentrations of PSMs are rare. We investigated whether koalas adjust the number and/or the size of their meals when offered eucalypt foliage varying naturally in concentrations of formylated phloroglucinol compounds (FPCs), a group of PSMs that have previously been shown to inhibit total food intake. High FPC concentrations caused koalas to eat more slowly, eat shorter meals and eat less per meal, which resulted in a reduced total intake. Because increasing FPC concentrations did not cause koalas to alter the number of meals that they ate, clear individual differences between koalas were observed, where some consistently ate fewer larger meals and others ate many smaller meals. Thus, different feeding strategies may still achieve the same outcome of a regulated intake of PSMs. The changes observed match the meal patterns of other herbivores ingesting PSMs known to stimulate nausea and emetic pathways, supporting the idea that feedback signals from nausea are an important way that koalas avoid toxication when eating eucalypt foliage.     

Exogenous amino acids stimulate human muscle anabolism without interfering with the response to mixed meal ingestion

We sought to determine whether ingestion of a between-meal supplement containing 30 g of carbohydrate and 15 g of essential amino acids (CAA) altered the metabolic response to a nutritionally mixed meal in healthy, recreationally active male volunteers. A control group (CON; n = 6, 38 +/- 8 yr, 86 +/- 10 kg, 179 +/- 3 cm) received a liquid mixed meal [protein, 23.4 +/- 1.0 g (essential amino acids, 14.7 +/- 0.7 g); carbohydrate, 126.6 +/- 4.0 g; fat, 30.3 +/- 2.8 g] every 5 h (0830, 1330, 1830). The experimental group (SUP; n = 7, 36 +/- 10 yr, 87 +/- 12 kg, 180 +/- 3 cm) consumed the same meals but, in addition, were given CAA supplements (1100, 1600, 2100). Net phenylalanine balance (NB) and fractional synthetic rate (FSR) were calculated during a 16-h primed constant infusion of L-[ring-2H5]phenylalanine. Ingestion of a combination of CAA supplements and meals resulted in a greater mixed muscle FSR than ingestion of the meals alone (SUP, 0.099 +/- 0.008; CON, 0.076 +/- 0.005%/h; P < 0.05). Both groups experienced an improvement in NB after the morning (SUP, -2.2 +/- 3.3; CON, -1.5 +/- 3.5 nmol x min(-1) x 100 ml leg volume(-1)) and evening meals (SUP, -9.7 +/- 4.3; CON, -6.7 +/- 4.1 nmol x min(-1) x 100 ml leg volume(-1)). NB after CAA ingestion was significantly greater than after the meals, with values of 40.2 +/- 8.5 nmol x min(-1) x 100 ml leg volume(-1). These data indicate that CAA supplementation produces a greater anabolic effect than ingestion of intact protein but does not interfere with the normal metabolic response to a meal.     

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.     

Extent of digestion affects the success of amplifying human DNA from blood meals of Anopheles gambiae (Diptera: Culicidae)

The success of distinguishing blood meal sources of Anopheles gambiae Giles through deoxyribonucleic acid (DNA) profiling was investigated by polymerase chain reaction (PCR) amplification at the TC-11 and VWA human short tandem repeats (STR) loci. Blood meal size and locus had no significant effect on the success of amplifying human DNA from blood meals digested for 0, 8, 16, 24 and 32 h (P = 0.85 and 0.26 respectively). However, logistic regression found a significant negative relationship between time since ingestion and the success probability of obtaining positive PCR products among meals digested for between 8 and 32 h (P = 0.001). Approximately 80% of fresh blood meals were successfully profiled. After 8 h, the proportion of blood meals that could be successfully profiled decreased slowly with time after ingestion, dropping to below 50% after approximately 15 h. There was no significant difference in the success of amplifying human DNA from blood meals of mosquitoes killed at time 0 and 8 h after ingestion (P = 0.272).     

Effect of meal type on specific dynamic action in the green shore crab,Carcinus maenas

The effect of meal type on specific dynamic action was investigated in the green shore crab, Carcinus maenas. When the crabs were offered a meal of fish, shrimp, or mussel of 3 % of their body mass the duration of the SDA response and thus the resultant SDA was lower for the mussel, compared with the shrimp or fish meals. In feeding behaviour experiments the crabs consumed almost twice as much mussel compared with fish or shrimp. When the animals were allowed to feed on each meal until satiated, the differences in the SDA response were abolished. The mussel was much softer (compression test) than the fish or shrimp meal, and meal texture is known to affect the SDA response in amphibians and reptiles. When the crabs were offered a meal of homogenized fish muscle or whole fish muscle, the SDA for the homogenized meal was approximately 35 % lower. This suggested that a significant portion of the SDA budget in decapod crustaceans may be related to mechanical digestion. This is not unexpected since the foregut is supplied by over forty muscles which control the cutting and grinding movements of the gastric mill apparatus. There were slight, but significant differences in protein, lipid, moisture and total energy content of each meal type. Three prepared meals that were high in either protein, lipid or carbohydrate were offered to the crabs to determine if the nutrient content was also a contributing factor to the observed differences in the SDA. The crabs did not eat the prepared meals as readily as the natural food items and as they are messy feeders there was a large variation in the amount of food eaten. The lack of significant differences in the SDA response as a function of nutrient content was likely due to differences in amount of food eaten, which is a major factor determining the SDA response. The differences in SDA when consuming natural food items were likely due to a combination of the costs of mechanical digestion, variation in nutrient content and food preference: determining how each of these factors contributes to the overall SDA budget remains a pressing question for comparative physiologists.     

Polymer-protomer transition of acetyl-CoA carboxylase as a regulator of lipogenesis in rat liver

Data are presented which indicate that the transition of acetyl-CoA carboxylase between the active polymeric and inactive protomeric conformations defined for the purified enzyme also occurs with the enzyme in vivo, depends upon the nutritional state of the animal, and is an important physiological phenomenon in the acute regulation of liver fatty acid synthesis. This conclusion utilized the observation that the protomeric form of purified acetyl-CoA carboxylase is inactivated by the binding of avidin to the biotinyl prosthetic group; the catalytically active filamentous form of the enzyme is resistant to avidin. Acetyl-CoA carboxylase activity was 75% avidin-resistant (polymeric) in the liver of meal-fed rats that had completed the consumption of a high glucose meal. This avidin resistance gradually decreased to 20% during the 21-h interval between meals. Peak resistance to avidin of liver carboxylase was attained within 30 min of initiating meal ingestion. The rise in carboxylase resistance to avidin could not be mimicked by insulin injection alone, but could be greatly attenuated by the addition of fat to the glucose meal. The amount of avidin-resistant acetyl-CoA carboxylase was closely associated with the concentration of hepatic malonyl-CoA and the subsequent rate of fatty acid synthesis.     

Factors Associated with Food Intake in Passengers on LONG-HAUL FLIGHTS

To understand better how disruption to daily routines and circadian factors affect food intake, some aspects of 361 passengers' eating habits during long‐haul flights across eight time zones were investigated. Two meals were provided during each flight. Passengers stated whether or not they had eaten part or all of each meal and the reasons for this decision. They were also asked to give their responses to it (appetite beforehand, enjoyment during the meal, and satiety afterwards), and the type of meal they would prefer to have eaten, given an unrestricted choice. There were few occasions (<6%) when a meal was refused altogether, and no single reason was dominant. Subjective responses to food intake were more positive when larger meals were eaten and “appetite” rather than “no choice” was given as the reason for eating. Subjective responses were also more positive in those who thought the size of the meal offered was neither too small nor too large. When the two meals were considered separately, the first meal was well received by the passengers, and their enjoyment of it was not significantly different from “normal.” The second meal (offered soon before landing in the new time zone) was less well received, and many passengers would have preferred a smaller meal. The findings contribute to an understanding of the factors determining the decision to eat a meal and the subjective responses to the food that is eaten. They also have implications for airlines wishing to provide food that is acceptable to passengers and for those providing meals for night workers.     

Metabolic response to feeding in the Chinese striped-necked turtle, Ocadia sinensis

We measured oxygen consumption in juvenile Chinese striped-necked turtles (Ocadia sinensis) after they ingested food, either as a single meal or as double meals, to examine the influence of meal type and feeding frequency on specific dynamic action (SDA). Temporal variation in oxygen consumption after feeding was evident in the ingesting turtles but not in the unfed control turtles. In the single-meal experiment, the peak metabolic rate and the integrated SDA response (the whole energetic cost for the processes of digestion) both did not differ between turtles ingesting mealworms and shrimps when the influence of variation in ingested energy was removed, and the time to reach peak metabolic rate was not affected by meal type and the amount of food ingested. Turtles in the double-meal experiment ingested more energy and hence had a prolonged duration of SDA response than did those in the single-meal experiment, but the integrated SDA response did not differ between both experimental treatments when the influence of variation in ingested energy was removed. Our results show that meal type and feeding frequency have important consequences on the SDA response of juvenile O. sinensis. As the integrated SDA response remained remarkably constant either between turtles ingesting different food or between turtles ingesting the same food but at different frequencies when the influence of variation in ingested energy was removed, we therefore conclude that the energetic cost associated with ingestion is primarily determined by energy content of food ingested in juvenile O. sinensis.     

Diuresis after a bloodmeal in female Anopheles freeborni

Female Anopheles freeborni discharge urine rapidly and copiously for a brief time after taking a meal of blood. This diuresis begins immediately upon cessation of feeding and continues for about 30 min at a constant rate. A decline in this rate follows and diuresis is completed by 50 min after feeding. This time-course of diuresis is independent of the size of the meal; diuresis after large meals occures at a higher rate, not over a longer time, than diuresis after small meals. Heat-stable and saline-soluble substances that induce rapid excretion by isolated Malpighian tubules can be extracted from the head and thoracic nervous system, suggesting the presence of a neurosecretory diuretic hormone similar to that found in other blood-sucking insects. Decapitation or section of the ventral nerve cord abolishes the rapid phase of diuresis after a bloodmeal. Therefore, in analogy to the situation in the tsetse fly, the head is required either as the source of a diuretic hormone or as link in the pathway that stimulates its release.     

Effect of solid meal on gastric emptying of,and glycemic and cardiovascular responses to,liquid glucose in older subjects

Gastric emptying is a determinant of the postprandial glycemic and cardiovascular responses to oral carbohydrate. We evaluated the effects of a solid meal on gastric emptying and the glycemic and cardiovascular responses to oral glucose in healthy older subjects. Ten subjects aged 72.1 +/- 1.9 yr were studied. Each subject had measurements of gastric emptying, blood glucose, serum insulin, blood pressure, and heart rate after ingestion of a 50-g glucose drink (300 ml) with (mixed meal) or without (liquid only) a solid meal (300 g ground beef). Gastric emptying of liquid was initially slightly more rapid (P < 0.05) after the mixed meal compared with liquid only at 5 min (92.0 +/- 1.5 vs. 96.0 +/- 1.3%) and much slower (P < 0.05) after 120 min. The time to peak blood glucose was less (39.0 +/- 4.0 vs. 67.5 +/- 10.3 min; P < 0.01) and blood glucose subsequently lower (P < 0.01) after the mixed meal. The increase in serum insulin was greater (P < 0.001) after the mixed meal. Blood pressure fell (P < 0.05) in the first 30 min, with no difference between the two meals. Increase in heart rate after both meals (P < 0.005), was greater (P < 0.05) after the mixed meal. The presence of a noncarbohydrate solid meal had discrepant effects on early and subsequent emptying of a nutrient liquid, which affects postprandial glycemia and increased heart rate.     

Factors associated with food intake in passengers on long-haul flights

To understand better how disruption to daily routines and circadian factors affect food intake, some aspects of 361 passengers' eating habits during long-haul flights across eight time zones were investigated. Two meals were provided during each flight. Passengers stated whether or not they had eaten part or all of each meal and the reasons for this decision. They were also asked to give their responses to it (appetite beforehand, enjoyment during the meal, and satiety afterwards), and the type of meal they would prefer to have eaten, given an unrestricted choice. There were few occasions (<6%) when a meal was refused altogether, and no single reason was dominant. Subjective responses to food intake were more positive when larger meals were eaten and "appetite" rather than "no choice" was given as the reason for eating. Subjective responses were also more positive in those who thought the size of the meal offered was neither too small nor too large. When the two meals were considered separately, the first meal was well received by the passengers, and their enjoyment of it was not significantly different from "normal." The second meal (offered soon before landing in the new time zone) was less well received, and many passengers would have preferred a smaller meal. The findings contribute to an understanding of the factors determining the decision to eat a meal and the subjective responses to the food that is eaten. They also have implications for airlines wishing to provide food that is acceptable to passengers and for those providing meals for night workers.     

Distention-mediated egg maturation in the mosquito,Aedes aegypti

Abdominal distention accelerates the release of a factor from the head of blood-fed Aedes aegypti mosquitoes. The critical period during which the head is required for oögenesis following blood ingestion is approx 6 h with a 5 μl meal, but small blood meals of 1 μl require the head to be present for significantly longer. Increasing the abdominal distention by supplementing the 1 μl meal with saline results in a critical period similar to that with 5 μl of blood. The information from the distended abdomen appears to travel via the ventral nerve cord. Transection of the ventral nerve cord prevents oögenesis from occurring after small blood meals, but not with larger blood volumes. Topical application of 100 pg of juvenile hormone III can substitute for the distention message.     

The effect of feeding regime on growth, locomotor activity pattern and the development of food anticipatory activity in greenback flounder

The mean final weight of juvenile greenback flounder Rhombosolea tapirina fed a single daily meal during the scotophase was lower than that of groups fed continuously or fed twelve, six, three or one meal during the photophase. Final weight did not differ among the latter five groups. Size variation in all groups of fish decreased during the course of the trial over 120 days. Groups assigned to a higher frequency (and hence a longer total daily meal duration) of daily meals were less active during mealtime. A distinct food anticipatory effect was observed in the groups of fish receiving a single daily meal during either photophase or scotophase, and also developed before at least one meal in the group of fish fed three meals per day.     

The pattern of feeding of first instar nymphs of Schistocerca americana

ABSTRACT The feeding behaviour of nymphs Schistocerca americana (Drury) was recorded throughout the light phases of the first stadium using a behavioural event recording program on a microcomputer. Most food was ingested on day 4 of the stadium, very little on day 1 and none on day 6, the final day of the stadium. Only 26–45% of the total food intake over the stadium occurred during the dark periods and more food was eaten in the last 4 h of each light period than earlier. Feeding occupied only about 5% of the total time. Variation in food intake was a consequence primarily of changes in the numbers of meals. After day 1, the average meal size did not change significantly. Meal length increased relatively slightly compared with meal size as a consequence of an increase in the proportion of time spent feeding in each meal as meal size increased. Meal size was correlated with the length of the previous interfeed suggesting a volumetric regulation. The distribution of pauses within meals was also consistent with the thesis that meal size is governed by the level of excitation in the central nervous system at the start of the meal.