赤腹松鼠能量代谢和营养需要的初步研究

在饲养条件下,赤腹松鼠(Callosciurus erythraeus)每天摄入干物质为7.06—9.91克/只,摄入能最为525.4—562.2千焦耳/千克~0.75每天每只摄入蛋白质:1.26—2.00克,脂肪0.69—2.79克。松鼠对能量、干物质、蛋白质和脂肪的消化率分别为85.7％—89.3％;84.7％—87.0％;75.9％—82.7％和79.1％—94.0％。赤腹松鼠喜食含脂量高的食物,对脂肪的消化能力高于蛋白质。营造种子含脂量高的多种树种混交林,提供松鼠足够的食物,是防止松鼠危害的有效途径。     

Heat increment of feeding and thermal substitution in mallard ducks feeding voluntarily on grain

The heat increment of feeding (HIF), including heat from digestion, assimilation, and nutrient interconversion, may substitute for thermogenesis and reduce thermoregulation costs. HIF and its substitution have been measured mainly in animals fed single large meals with high protein content, but many species such as some dabbling ducks (Anatini) feed more continuously in intermittent small meals with low protein content. We measured HIF in seven mallard ducks (Anas platyrhynchos) eating mixed grain (corn, wheat, milo) ad libitum while floating on water at 23 degrees C (thermoneutral) and 8 degrees C. HIF was calculated as the difference in oxygen consumption between fed and fasted birds, correcting for costs of behavior, heat storage (change in body temperature), and heating food. Substitution occurred if HIF was lower at 8 degrees C than at 23 degrees C. Food intake of mallards averaged 83% of that required for maintenance (zero energy balance) at 23 degrees C, and 68% of maintenance at 8 degrees C. Mean HIF (+/-1 SE) was 1.59+/-0.61 l O(2) at 23 degrees C and 1.48+/-0.68 l O(2) at 8 degrees C. These values were 4.9% and 3.9% of metabolizable energy intake, consistent with values expected for grain. HIF did not differ between temperatures (ANCOVA, birds as blocks, intake as covariate, P=0.51), indicating no measurable substitution at these intake levels in intermittent meals. For these large birds that feed on low-protein foods in intermittent small meals, the ecological importance of HIF substitution appears negligible during periods when food intake is below that required for energy balance.     

Clonidine increases food and protein consumption in rats

Rats were given clonidine or its diluent, and allowed to eat freely from two isocaloric diets that differred in protein or carbohydrate content. Low clonidine doses (25–50 μg/kg) significantly increased total food and protein intake by rats given access to a high and a low protein diet. Several pairs of diets, differing in protein contents, were tested; clonidine's effect was greatest when a diet containing 30–45% protein was paired with one that was very low (5%) in protein. Higher clonidine doses (200 μg/kg) failed to modify either total food or protein intake. Clonidine had no effects on food or nutrient intake among animals given access to diets that differed in carbohydrate content (25 or 70% carbohydrate, plus 25% protein). In rats given access to only one diet, clonidine administration decreased food consumption when the diet was low in protein (5%), but increased consumption when the diet contained 25 or 50% protein. These data suggest that central noradrenergic synapses participate in the mechanisms controlling appetites for proteins. Clonidine may enhance protein intake by stimulating presynaptic alpha receptors, thus diminishing central noradrenergic tone. This effect on noradrenergic transmission is probably partly overcome by protein consumption, which increases brain tyrosine levels and thus can accelerate norepinephrine synthesis. Clonidine or related drugs may be useful clinically in treating diseases characterized by impaired appetite or increased need for protein.     

A study of the food and feeding of perch, Perca fluviatilis L., in Windermere

SUMMARY. Perch were sampled for their stomach contents at regular intervals throughout 24 h from June until October in 1973 and from February 1975 until January 1976. They were found to feed on benthic organisms from November until April, on benthos and plankton during May and June and on perch fry and zooplankton from July until October. Perch over a wide size range feed on similar prey. Fish showed great variability in the weight of their stomach contents. A method based on a points system was developed to estimate the weight of food in the stomach for a given weight of fish at a known time. A diel feeding pattern which varied with the season was apparent from these data. Rates of gastric evacuation were assumed to be exponential and were calculated from the drop in night-time stomach content weights when food intake was assumed to be zero. The rates ranged from 0.18 mg h⁻¹ at a mean water temperature of 11°C in May to 0.35 mg h⁻¹ at a mean water temperature of 17°C in July. Assuming that food consumption followed a linear rate of intake, the standard Bajkov method was considered an adequate model to calculate daily food consumption. Daily food consumption (mg dry weight) was calculated for 150 g perch for all months of the year (November to April and September and October being combined). A second series of values was calculated making corrections for the time spent in the fishing gears when food intake was zero but gastric evacuation continued. Daily food consumption figures for 150g male perch based on Winberg's hypotheses (1956) and growth data showed no significant differences from this second series of values, when both were expressed in energy terms. When certain assumptions have been tested, growth data and Winberg's equations together may be a suitable method for calculating an energy budget for the Windermere perch population.     

Determinants of the dramatic seasonal changes in the intake of energy and protein by Japanese monkeys in a cool temperate forest

Daily intake of gross energy (DGEI) and protein (DGPI) of Japanese monkeys in a cool temperature forest were investigated in different four seasons. As a result, dramatic seasonal differences in DGEI and DGPI were found: DGEI and DGPI in winter were significantly lower than those in spring and autumn, being only about 17–42% of those in the two seasons. DGEI and DGPI in summer were also lower than those in autumn and spring, being only about 29–52% of those in the two latter seasons. Seasonal comparisons of some variables on food qualities revealed that much lower values of DGEI and DGPI in winter and summer were influenced srongly not so much by the lower calorie and protein content of food as by the lower speed of dry weight intake. Multiple regression analyses for each food item revealed that the unit weight was a more important factor in determining the speed of dry weight intake than was the speed of unit intake. In addition, the speed of dry weight intake contributed much more to the speed of calorie and protein intake than did the content of calorie and protein. Multiple regression analyses, employing DGEI and DGPI (as dependent variables) and daily mean values of some variables related to food quality (as independent variables), revealed that the mean values of speed of calorie and protein intake on food items eaten in a day could explain 79.0% and 85.9% of the variance in DGEI and DGPI, respectively. In addition, the mean value of the speed of dry weight intake of food items eaten in a day can be used to explain 74.3% and 52.8% of the variance in DGEI and DGPI, respectively. These findings suggested that not only nutritional content of food but also the speed of dry weight intake strongly determined the nutritional condition of nonhuman primates. Am. J. Primatol. 41:267–288, 1997. © 1997 Wiley-Liss, Inc.     

Patterns in food intake correlate with body mass index

Quantifying eating behavior may give clues to both the physiological and behavioral mechanisms behind weight regulation. We analyzed year-long dietary records of 29 stable-weight subjects. The records showed wide daily variations of food intake. We computed the temporal autocorrelation and skewness of food intake mass, energy, carbohydrate, fat, and protein. We also computed the cross-correlation coefficient between intake mass and intake energy. The mass of the food intake exhibited long-term trends that were positively skewed, with wide variability among individuals. The average duration of the trends (P = 0.003) and the skewness (P = 0.006) of the food intake mass were significantly correlated with mean body mass index (BMI). We also found that the lower the correlation coefficient between the energy content and the mass of food intake, the higher the BMI. Our results imply that humans in neutral energy balance eating ad libitum exhibit a long-term positive bias in the food intake that operates partially through the mass of food eaten to defend against eating too little more vigorously than eating too much.     

The importance of ingestion rates for estimating food quality and energy intake

Testing ecological or socioecological models in primatology often requires estimates of individual energy intake. It is a well established fact that the nutrient content (and hence the energy content) of primate food items is highly variable. The second variable in determining primate energy intake, i.e., the ingestion rate, has often been ignored, and few studies have attempted to estimate the relative importance of the two predictors. In the present study individual ingestion rates were measured in two ecologically very different populations of Hanuman langurs (Semnopithecus entellus) at Jodhpur, India, and Ramnagar, Nepal. Protein and soluble sugar concentrations in 50 and 100 food items. respectively, were measured using standardized methods. Variation in ingestion rates (gram of dry matter per minute) was markedly greater among food items than among langur individuals in both populations, but did not differ systematically among food item categories defined according to plant part and age. General linear models (GLMs) with ingestion rate, protein, and soluble sugar content explained 40-80% of the variation in energy intake rates (kJ/min). The relative importance of ingestion rates was either similar (Ramnagar) or much greater (Jodhpur) than the role of sugar and/or protein content in determining the energy intake rates of different items. These results may impact socioecological studies of variation in individual energy budgets, investigations of food choice in relation to chemical composition or sensory characteristics, and research into habitat preferences that measures habitat quality in terms of abundance of important food sources. We suggest a definition of food quality that includes not only the amount of valuable food contents (energy, vitamins, and minerals) and the digestibility of different foods, but also the rate at which the food can be harvested and processed. Such an extended definition seems necessary because time may constrain primates when feeding competition is intense and foraging is risk-prone.     

Food Consumption and Subsistence in Three Caboclo Populations on Marajó Island, Amazonia, Brazil

In this article data on household food consumption is used to further understanding of subsistence strategies in three Caboclo populations on Marajó Island, Amazonia, Brazil. Data were collected using participant observation and 24-hour food recalls in 16 households for 7 consecutive days during the rainy (March) and dry (July) seasons. Marajó-Açu households (n = 6) had the highest levels of energy and protein intake relative to recommendations. This was probably related to their successful integration into the prosperous acai (a palm fruit) market of the riverine area. Praia Grande households (n = 6) had the lowest values for energy intake (rainy season), which supports the authors' ethnographic observations of some instability in the subsistence system of this population. Paricatuba households (n = 4) exhibited intermediate values of energy and protein intakes, but less seasonal variation in consumption than the other two populations. Despite the differences observed, food consumption does not appear to be a major limitation for any of the three populations. The data support recent hypotheses concerning the concomitant and multiple use of várzea (floodplain) and terra firme (upland) environments by the Caboclos and integration into the local market economy as the central strategies in dealing with the so-called socioenvironmental constraints of the Amazonian floodplain.     

Evaluation of iodine levels in daily dietary intake and urine of persons participating in epidemiological studies in the Krakow macro-region after the disaster in Czernobyl and level of iodine in drinking water of that region]

Following the Czernobyl accident, an epidemiologic study was undertaken in which the daily iodine intake was estimated in 15% of the population studied. Iodine excretion was measured in single morning urine specimens. The iodine content was also assessed in the water form wells and in cow-milk at farms in randomly chosen villages in the region of Krynica and Nowy Sacz. On the basis of a 24-hour diet recall, the mass of each food product consumed daily was estimated for 483 persons in the Kraków voivodship (14.4% of the total population) and for 397 persons in the Nowy Sacz voivodship (15.8% of the total population). Using this data, the nutrient content of the daily diet was calculated for each studied individual. Measurements of iodine content in water and cow-milk show relatively lower iodine levels in the Nowy Sacz voivodship. The estimated value of the iodine content in milk (5.5 micrograms/100 g of milk) was considered in the estimates of the chemical composition of the daily diet of the inhabitants of this region. The mean values of the daily energy as well as the protein and calcium consumption in all subpopulations grouped with respect to domicile, age and sex, fell within the recommended daily allowances for these groups. The iodine content, while widely scattered, concentrated around low values. The median values of the iodine content in children of age 3-10 years, age 10-16 years and in adults, were 66%, 48% and 25-40% of the recommended daily allowances, respectively. No particular differences in the food intakes were observed between inhabitants of Kraków and Nowy Sacz voivodships. Nor were significant differences found in the urine iodine excretion in groups of these regions. The low iodine content in the daily food intake may be an essential factor in the ethiology of the increasing number of thyroid goiter.     

Nutrient intake,adiposity, and diabetes.

To study the role of nutritional factors in the genesis of diabetes, estimations of blood sugar concentration, food intake, and adiposity (as body mass index; BMI) were carried out on three normal population samples--namely, 961 employees of Beecham Ltd, 1005 employees of the Greater London Council, and 1488 middle-aged male civil servants (Whitehall study). Blood sugar concentrations and indices of glucose tolerance correlated positively with the degree of adiposity but tended to be negatively correlated with total food energy intake and its component nutrients (total carbohydrate, sucrose, and fat). This inverse trend was largely accounted for by highly significant inverse correlations between food energy intake and adiposity, a relation found in both sexes and in all three population samples and which extended across the whole range of nutrient intake and BMI. These findings suggest that greater degrees of adiposity are associated with lower than average food energy intakes and hence lower total energy expenditures. The association of increased adiposity with low food energy consumption may indicate an underlying "low energy throughput" state, and it may be the mechanisms of this, as well as the obesity, that are responsible for disease.     

Effect of reproductive state and body size on food consumption in captive Galago senegalensis braccatus

Measurements of food consumption for different types of foods were made for seven Galago senegalensis braccatus. Differences because of reproductive state in females and body size were found. Lactating females consumed more food in total and had greater energy and protein intake than they did during other reproductive states. Near-term pregnant females consumed less food, energy, and protein than they did during other reproductive states. Body size affected food intake, with smaller animals ingesting more per unit metabolic weight than larger subjects.     

Naltrexone administered to central nucleus of amygdala or PVN: neural dissociation of diet and energy

There is evidence that opioids may affect food consumption through mechanisms as diverse as reward or energy metabolism. However, these hypotheses are derived from studies employing peripheral or, more rarely, intracerebroventricular administration of drugs. Opioid receptors have a wide distribution in the central nervous system and include a number of regions implicated in food intake such as the hypothalamic paraventricular nucleus (PVN) and the central nucleus of the amygdala (ACe). It is not known whether local opioid receptor blockade in either of these regions will produce similar effects on food intake. To examine this issue, a chronic cannula was aimed at either the PVN or ACe of rats that were fed a choice of a high-fat and high-carbohydrate diet, which allows for the measurement of both preference and total energy consumption. Naltrexone influenced preferred and nonpreferred food consumption, depending on the site of administration. Consumption of both preferred and nonpreferred diets was suppressed after PVN naltrexone administration, whereas only preferred diet intake was reduced after ACe injection of naltrexone. The present evidence indicates that direct stimulation of different brain regions with naltrexone may be associated with diverse effects on diet selection, which may be accounted for by manipulation of specific functional neural circuitry.     

The Potential Role of Protein Leverage in the US Obesity Epidemic

The protein leverage model of obesity posits that decreasing the protein fraction of the diet leads to compensatory increases in total energy intake in an attempt to maintain a target amount of absolute protein consumed. The resulting increased energy intake thereby causes weight gain. According to food balance sheets published by the Food and Agriculture Organization of the United Nations, while the absolute protein content of the US food supply has increased since the early 1970s, the fraction of available calories from protein has decreased by ~1% because of greater increases in available carbohydrate and fat. Counterintuitively, even such a small decrease in the protein fraction of the food supply has the potential to result in relatively large increases in energy intake according to the protein leverage model. Therefore, while the protein leverage effect is unlikely to fully explain the obesity epidemic, its potential contribution should not be ignored.     

Regulatory alterations of daily energy expenditure induced by fasting or overfeeding in unrestrained rats

The consequences of fasting or overfeeding during 2 days on energy expenditure were investigated by continuously monitoring O2 consumption in unrestrained, unanesthetized rats. O2 consumption decreased by 15% on the 1st day of fasting and then by an additional 15% on the 2nd day. On the 3rd day, when rats were fed again, energy intake increased by 30% above control (prefasting) values, whereas energy expenditure rapidly increased but no more than control values. On the other hand, when ad libitum fed animals were offered a sucrose solution (32%) for 2 days, energy intake increased by 30% and energy expenditure by 9-12%. On the 3rd day, when the rats were fed with their normal diet, energy intake significantly decreased under control (preoverfeeding) values during one day, but energy expenditure rapidly returned to normal values. The results show that fasting decreases, whereas hyperphagia increases 24-h energy expenditure during the treatments. When the treatments are terminated, energy expenditure rapidly returns to normal values, but fasting induces a postfasting increase of energy intake (during 2 days), whereas hyperphagia, on the contrary, results in a transient decrease of appetite. This indicates that alterations of food intake induce compensatory changes of energy expenditure during the treatments, but that after the treatments, energy balance is normalized via regulatory adjustments in the ratio of energy expenditure over energy intake.     

Effects of Reproductive Status on Energy Intake,Ingestion Rates,and Dietary Composition of Female <Emphasis Type="BoldItalic">Cebus capucinus</Emphasis> at Santa Rosa,Costa Rica

The limiting factor for fitness in female primates is the acquisition of high-quality food, i.e., food that is high in energy and nutrients, such as protein, fat, and carbohydrates. Reproductive status can influence female feeding patterns, e.g., lactating females in some primate species consume greater quantities of food and specific nutrients than do nonlactating females. We examined the energy intake, ingestion rate, and composition of the diet in female white-faced capuchins in 3 reproductive states: lactating, gestating, and cycling. We observed 12 reproductively active females for 7 mo and compared their energy intake, ingestion rates, and intake rates of nutrients: protein, fat, sugar, and fiber. Lactating females took in significantly more energy per hour while feeding than pregnant and cycling females did. Lactating females also ingested significantly more food items per hour, but they did not spend more time eating than other females did, and they did not differ in the composition of their diet as measured by insect consumption and proportion of protein. Pregnant and cycling females did not differ from each other in any of the measures. We predicted that as the infants aged and began to move independently to forage and play, their mothers’ energy intake rates would decrease in concert with decreased energy demands by the infant. We found a statistically significant relationship between these 2 factors, with infant age explaining 75.4% of variation in mothers’ energy intake, supporting previous studies that found lactation to be the most energetically expensive reproductive state.     

Quantitative Genetics of Food Intake in Drosophila melanogaster

Food intake is an essential animal activity, regulated by neural circuits that motivate food localization, evaluate nutritional content and acceptance or rejection responses through the gustatory system, and regulate neuroendocrine feedback loops that maintain energy homeostasis. Excess food consumption in people is associated with obesity and metabolic and cardiovascular disorders. However, little is known about the genetic basis of natural variation in food consumption. To gain insights in evolutionarily conserved genetic principles that regulate food intake, we took advantage of a model system, Drosophila melanogaster, in which food intake, environmental conditions and genetic background can be controlled precisely. We quantified variation in food intake among 182 inbred, sequenced lines of the Drosophila melanogaster Genetic Reference Panel (DGRP). We found significant genetic variation in the mean and within-line environmental variance of food consumption and observed sexual dimorphism and genetic variation in sexual dimorphism for both food intake traits (mean and variance). We performed genome wide association (GWA) analyses for mean food intake and environmental variance of food intake (using the coefficient of environmental variation, CV _E, as the metric for environmental variance) and identified molecular polymorphisms associated with both traits. Validation experiments using RNAi-knockdown confirmed 24 of 31 (77%) candidate genes affecting food intake and/or variance of food intake, and a test cross between selected DGRP lines confirmed a SNP affecting mean food intake identified in the GWA analysis. The majority of the validated candidate genes were novel with respect to feeding behavior, and many had mammalian orthologs implicated in metabolic diseases.     

The relationship between specific dynamic action and growth in grass carp, Ctenophavyngodon idella (Val.)

Individual grass carp, Ctenopharyngodon idellu , were maintained in a respirometer for a month and fed pelleted diets containing various proportions of carbohydrate, fat and protein at different ration levels. Oxygen consumption was measured continuously, allowing the effects of consecutive daily feeding on respiration to be studied. The relationships established between daily food intake and oxygen consumption showed that, on average, 23.3% (high protein diet), 15.3% (high carbohydrate diet), 20.7% (high lipid diet) and 7.0% ( Lemnu diet ) of the absorbed energy was partitioned into specific dynamic action (SDA). (Here the term SDA is used to describe the oxygen consumption of a feeding fish in excess of the routine metabolic rate.) In terms of the overall energy budgets of growing fish, SDA represented between 12 and 58% of the total heat lost over the experimental period and was equivalent to between 14 and 33% of the consumed energy. Ration was positively correlated with heat loss due to total respiration ( r = 0.881) and with heat loss due to SDA ( r = 0.762). As ration increased, the size of SDA relative to total respiration increased. Significant positive correlations were found between oxygen consumption (total or due to SDA) and specific growth rate, and between oxygen consumption and the deposition of protein and energy. However, growth rate had a minimal influence on daily oxygen consumption when compared with food intake.     

高纤维食物对黄毛鼠摄食和消化的影响

动物的消化生理特征和消化对策可决定其营养生态位。为揭示黄毛鼠适应高纤维食物的消化对策,在高纤维食物饲喂10 d和20 d时,以食物平衡法测定摄食量、粪便量及相应的能量学参数。在取食高纤维食物10 d时,摄食量无显著变化,但粪便量显著增加,消化率显著下降;至20 d时,摄食量显著增加,消化率仍低于对照组,但消化能与对照组无差异。高纤维组动物的体重在第10 d时显著下降,但在第20 d时未进一步下降。该结果表明,黄毛鼠能够通过增加摄食量和降低消化率的消化对策适应高纤维食物,此外,降低体重使总能量需求减少,也是其适应低质量食物的对策之一。     

Reward mechanisms in obesity: new insights and future directions

Food is consumed in order to maintain energy balance at homeostatic levels. In addition, palatable food is also consumed for its hedonic properties independent of energy status. Such reward-related consumption can result in caloric intake exceeding requirements and is considered a major culprit in the rapidly increasing rates of obesity in developed countries. Compared with homeostatic mechanisms of feeding, much less is known about how hedonic systems in brain influence food intake. Intriguingly, excessive consumption of palatable food can trigger neuroadaptive responses in brain reward circuitries similar to drugs of abuse. Furthermore, similar genetic vulnerabilities in brain reward systems can increase predisposition to drug addiction and obesity. Here, recent advances in our understanding of the brain circuitries that regulate hedonic aspects of feeding behavior will be reviewed. Also, emerging evidence suggesting that obesity and drug addiction may share common hedonic mechanisms will also be considered.     

Serum leptin, energy budget, and thermogenesis in striped hamsters exposed to consecutive decreases in ambient temperatures

Leptin has been found to be a direct participant in the regulation of both energy intake and energy expenditure in small mammals showing seasonal declines in body mass (M(b)) and fat mass, but its roles in an animal exhibiting seasonally increased thermogenesis and unchanged M(b) remain unclear. Serum leptin levels, energy budget, and thermogenesis were measured in striped hamsters exposed to consecutive decreases in ambient temperatures ranging from 23° to -23°C. Cold-exposed hamsters had significant increases in gross energy intake (GEI), the rate of basal metabolism, nonshivering thermogenesis, and activity of cytochrome c oxidase (COX) in brown adipose tissue (BAT), compared with control hamsters, indicating a cold-induced elevation of thermogenesis. Body mass and fat content were decreased in cold-exposed animals, and serum leptin levels were increased in hamsters exposed to temperatures of -8°C and below in inverse proportion to body fat content. Serum leptin levels were positively correlated with GEI and BAT COX activity in cold-exposed hamsters, but no such relationships were observed in control animals. These findings suggest that cold-exposed hamsters increase food consumption to meet the energy requirements for increased BAT thermogenesis. The increases in serum leptin levels are likely involved in increased thermogenesis in hamsters under cold stress. Cold-exposed hamsters may become leptin resistant, which is associated with impaired regulation of food intake. This new natural model of leptin resistance may also provide insight into the dynamic long-term control of energy homeostasis for animals that do not exhibit seasonal decline in M(b).