Relationships between dietary sodium chloride, food intake and food conversion in the rainbow trout

The addition of up to 8.5 % sodium chloride to the diet of rainbow trout Salmo gairdneri had no significant effect on either food intake or food conversion efficiency. Over a range of rations from 4 % to 38 % of dry weight per week, there was a rectilinear relationship between ration and growth rate. The weight maintenance requirement and rate of weight loss during fasting were estimated from this relationship. Food conversion efficiency ( K ) increased from 0.00 at 4% dry weight per week food intake ( x ) to 0.19 at 38%, according to the equation K =0.21-0.77/x.     

Age differences in food intake and dietary selection of wild male Japanese macaques

Age differences in food intake and dietary selection were studied for 8 months among wild male Japanese macaques (Macaca fuscata) under non-predatory situations. Juveniles' feeding time was longer than adult males' in some months, in particular in mating seasons, but did not differ in the other months. Juveniles' feeding speed was slower than that of adult males. However, the age difference in average feeding speed was smaller (90%) than that in expected daily energy expenditure (62–58%). The extent of age difference in feeding speed varied with the food type: the difference was large for fibrous foods, but small for fruits or seeds. As a consequence of the age differences in time spent feeding and feeding speed, the age difference in daily food intake was smaller than expected from metabolic demands. Thus, the hypothesis that juveniles are more vulnerable to starvation than adults was not supported among male Japanese macaques in predator-free Yakushima. Juveniles ate more animal matter, while adult males ate more fibrous foods.     

Simultaneously correcting for population stratification and for genotyping error in case-control association studies

In population-based case-control association studies, the regular chi (2) test is often used to investigate association between a candidate locus and disease. However, it is well known that this test may be biased in the presence of population stratification and/or genotyping error. Unlike some other biases, this bias will not go away with increasing sample size. On the contrary, the false-positive rate will be much larger when the sample size is increased. The usual family-based designs are robust against population stratification, but they are sensitive to genotype error. In this article, we propose a novel method of simultaneously correcting for the bias arising from population stratification and/or for the genotyping error in case-control studies. The appropriate corrections depend on sample odds ratios of the standard 2x3 tables of genotype by case and control from null loci. Therefore, the test is simple to apply. The corrected test is robust against misspecification of the genetic model. If the null hypothesis of no association is rejected, the corrections can be further used to estimate the effect of the genetic factor. We considered a simulation study to investigate the performance of the new method, using parameter values similar to those found in real-data examples. The results show that the corrected test approximately maintains the expected type I error rate under various simulation conditions. It also improves the power of the association test in the presence of population stratification and/or genotyping error. The discrepancy in power between the tests with correction and those without correction tends to be more extreme as the magnitude of the bias becomes larger. Therefore, the bias-correction method proposed in this article should be useful for the genetic analysis of complex traits.     

Mu-opioid receptors and dietary protein stimulate a gut-brain neural circuitry limiting food intake

Intestinal gluconeogenesis is involved in the control of food intake. We show that mu-opioid receptors (MORs) present in nerves in the portal vein walls respond to peptides to regulate a gut-brain neural circuit that controls intestinal gluconeogenesis and satiety. In vitro, peptides and protein digests behave as MOR antagonists in competition experiments. In vivo, they stimulate MOR-dependent induction of intestinal gluconeogenesis via activation of brain areas receiving inputs from gastrointestinal ascending nerves. MOR-knockout mice do not carry out intestinal gluconeogenesis in response to peptides and are insensitive to the satiety effect induced by protein-enriched diets. Portal infusions of MOR modulators have no effect on food intake in mice deficient for intestinal gluconeogenesis. Thus, the regulation of portal MORs by peptides triggering signals to and from the brain to induce intestinal gluconeogenesis are links in the satiety phenomenon associated with alimentary protein assimilation.     

Patterns of food intake and self-selection of macronutrients in rats during short-term deprivation of dietary zinc

Although it has been known for more than 50 years that zinc (Zn) deficiency regularly and consistently causes anorexia in many animal species, the basic mechanism(s) that cause this phenomenon still remain(s) an enigma. The following studies describe feeding behavior in the early stages of zinc deficiency in the rat model. In one experiment, we used computerized feeding monitors that measured the intake of individual rats at 10-min intervals over 24-hr periods. Male rats were acclimated to the cages and fed a Zn-adequate egg-white-based diet, or a similar diet with <1.0 mg Zn/kg. Food intake was monitored for seven, consecutive 24-hr periods. The 24-hr food intake pattern of the Zn-deprived rats did not differ from the controls; they simply ate less food, mainly during the night hours, with no differences between groups during the day. Although Zn-deprived rats ate less food than controls, the percentage of total diet consumed during night and day did not differ between groups. In another experiment, we simultaneously offered male rats three isocaloric diets with different macronutrient compositions and with or without adequate Zn, and measured the amount of each diet selected during seven, 24-hr periods. The three diets contained either 57% protein from egg white, 30% fat from soybean oil, or 80% carbohydrate from a combination of starch, hydrolyzed starch, and sucrose. For the first four days on experiment, rats selected similar amounts of each diet. Then the Zn-deprived rats began to select only 50% as much of the protein diet as the controls. Similar results were obtained when the data were expressed on the basis of each macronutrient as a percentage of the total diet selected. Zn-deprived rats selected a diet that contained 8% protein, 73% carbohydrate, and 6% fat while the Zn-adequate rats selected 12% protein, 69% carbohydrate, and 6% fat. Fat intake was not affected by Zn-deprivation. The results confirm our previous findings, and are discussed in terms of Zn-deprivation blunting the pathways of signal transduction that involve the peptide hormones known to affect food intake regulation.     

Continuous intraventricular infusion of neuropeptide Y evokes episodic food intake in satiated female rats: effects of adrenalectomy and cholecystokinin

In these studies the pattern of feeding behavior during continuous intraventricular (IVT) infusion of NPY for 4 hr in the satiated female rat was monitored. Whereas saline infusion was ineffective, each of the three doses of NPY (117, 470 or 1175 pmol/hr) increased feeding during the entire 4 hr infusion and 2 hr postinfusion period. The cumulative food intake at the end of 4 hr of NPY infusion was enhanced in a dose-related fashion between 0, 117 and 470 pmol/hr; at 1175 pmol/hr food intake plateaued. In addition, the latency to initiate feeding response decreased in a dose-related fashion and feeding occurred in discrete (35-45) episodes during the 4 hr infusion period. Further, the total time feeding and local eating rate (g/min) increased significantly in response to the higher rates of NPY infusion. Concurrent infusion of cholecystokinin (CCK) at either equimolar or 2.5 x NPY dose, affected neither the NPY-induced cumulative food intake nor any other parameter of feeding behavior. On the other hand, cumulative food intake was significantly decreased in adrenalectomized rats in response to NPY infusion (470 pmol/hr); a response due primarily to a marked suppression in some, and almost complete cessation of food consumption in other rats during the second 2 hr period of NPY infusion. These studies show that continuous central infusion of NPY can produce sustained, intermittent feeding behavior and adrenalectomy significantly curtailed the duration of NPY effectiveness.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of growth, food intake, and dietary zinc on diadenosine tetraphosphate concentrations in rats

The nucleotide diadenosine tetraphosphate has been suggested to function as a signal molecule for the initiation of DNA replication. Previous studies have indicated that diadenosine tetraphosphate is synthesized by certain aminoacyl tRNA synthetases and that diversion of AMP from the amino acid-enzyme complex to ATP to form diadenosine tetraphosphate is facilitated by zinc ions. The growth retardation of zinc-deficient rats is associated with specific reduction in DNA replication and also with a potentially growth-limiting decrease in food intake. The possibility has been investigated that in zinc-deficient rats, lack of Zn(2+) restricts diadenosine tetraphosphate synthesis, resulting in a failure to synthesize DNA and in a reduction in growth. The results indicate that the depressed growth potential caused by the reduction in food intake associated with the deficiency was sufficient to lower diadenosine tetraphosphate concentrations significantly in the liver and spleen. However, there was no indication of a specific effect of zinc deficiency on diadenosine tetraphosphate values.     

The influence of nymphal and adult dietary protein on food intake and reproduction in female brown-banded cockroaches

Female brown-banded cockroaches, Supella longipalpa (F.) (Dictyoptera: Blattellidae), failed to elevate consumption rates when fed a 5% protein diet compared with females fed either 25% protein or commercial rat food. Adult performance was directly influenced by dietary protein level: Females fed 65% protein died rapidly, while in females fed 5% protein feeding and reproductive rates were reduced after production of three oothecae. In females fed a low protein diet as both late instar nymphs and as adults, mating was delayed and they required more time to form oothecae than females switched to 25% protein as adults. The role of nymphal reserves in adult reproduction is discussed.

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Résumé La consommation et la reproduction de S. longipalpa ont été examinées lors de la consommation d'aliment standard pour rat et de régimes artificiels contenant 5, 25 et 65% de protéines. Les femelles élevées sur régime à 5% de protéines ne consomment pas plus et leur reproduction est significativement inférieure à celle de femelles élevées sur aliment standard ou à 25% de protéines; après la production de 3 oothèques, la reproduction de ces femelles se ralentit, leur consommation diminue et les oothèques deviennent plus petites que celles des femelles élevées sur un régime à 25% de protéines. Nous supposons que les premiers cycles reproductifs de ces femelles ont été assurés avec les réserves accumulées pendant la vie larvaire. Les femelles alimentées sur régime à 5% de protéines à la fois pendant le dernier stade larvaire et pendant la vie imaginale ont besoin de beaucoup plus de temps pour s'accoupler et pour produire des oothèques que les femelles alimentées sur régime à 5% pendant le dernier stade larvaire et transférées adultes sur un régime à 25% de protéines. Ainsi, les réserves larvaires sont une ressource importante améliorant la reproduction des adultes ayant un régime pauvre en protéines. Cependant, le passé alimentaire larvaire a peu d'effet sur la reproduction des adultes alimentés convenablement.

     

Effect of disrupted episodic memory on food consumption: no impact of neuronal loss of endophilin A1 on food intake and energy balance

Food intake is generally assumed to reflect a regulatory tension between homeostatic and hedonic drivers. Information from individuals with memory dysfunction suggests that episodic memory may also play a significant role. We reasoned that if memory influences food intake, then disrupting a genetic factor that is important in episodic memory formation should affect food intake and energy balance. We performed spatial learning tests on neuronal specific endophilin A1 (EENA1) KO mice using the four-arm baited version of the radial arms maze (RAM). Energy regulation has also been evaluated. As anticipated neuronal EENA1 KO mice had impaired spatial memory. However, loss of endophilin A1 did not result in greater food intake, or altered energy absorption efficiency, relative to wild-type (WT) mice, when fed either low or high fat diets. Moreover, loss of EENA1 did not significantly affect other features of energy balance—physical activity and energy expenditure. No statistically significant changes were observed in the expression of hypothalamic neuropeptides related to food intake regulation, or circulating levels of leptin. We conclude that food intake and energy balance are largely governed by homeostatic and hedonic processes, and when these processes are intact memory probably plays a relatively minor role in food intake regulation.     

Effect of dietary fatty acid composition on food intake, triglycerides, and hypothalamic peptides

While a high-fat diet when compared to low-fat diet is known to produce overeating and health complications, less is known about the effects produced by fat-rich diets differing in their specific composition of fat. This study examined the effects of a high-fat diet containing relatively high levels of saturated compared to unsaturated fatty acids (HiSat) to a high-fat diet with higher levels of unsaturated fatty acids (USat). A HiSat compared to USat meal caused rats to consume more calories in a subsequent chow test meal. The HiSat meal also increased circulating levels of triglycerides (TG) and expression of the orexigenic peptides, galanin (GAL) in the hypothalamic paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH). A similar increase in TG levels and PVN GAL and PFLH OX was also seen in rats given chronic access to the HiSat compared to USat diet, while neuropeptide Y (NPY) and agouti-related protein (AgRP) in the arcuate nucleus showed decreased expression. The importance of TG in producing these changes was supported by the finding that the TG-lowering medication gemfibrozil as compared to vehicle, when peripherally administered before consumption of a HiSat meal, significantly decreased the expression of OX, while increasing the expression of NPY and AgRP. These findings substantiate the importance of the fat composition in a diet, indicating that those rich in saturated compared to unsaturated fatty acids may promote overeating by increasing circulating lipids and specific hypothalamic peptides, GAL and OX, known to preferentially stimulate the consumption of a fat-rich diet.     

From feeding station to patch: scaling up food intake measurements in grazing cattle

The technique of grazing cut sods was used in combination with sound and video recording to examine the feasibility of using small-scale depletion curves derived from stall trials to estimate forage intake of cattle at the pasture. Setaria lutescens sods were grazed for a variable number of bites to generate patch depletion curves. Depletion curves characterize forage intake as a function of the number of bites taken at a single feeding station. Thus, the method agrees with a hierarchical approach to foraging and it could be used as a basis for scaling up food intake measurements to larger spatial scales. Two sod experiments were carried out, with the second experiment as a validation for predictions of intake. A field experiment was carried out to validate the predictions from the sod experiments with respect to both the amount and the rate of intake. Bite weight was largely determined by initial sward height and depletion level. Cumulative dry matter intake from the sods was well described by a rectangular hyperbola including the variables of number of bites and sward height. Bulk density added little to the explained variation, but was an important factor to account for the dry matter intake on short, dense sods from the second experiment. Feeding time could be explained to a great extent by the number of bites and chews taken, both in the sod and in the field experiments. However, the animals were substantially faster when grazing in the field than on the sods due to a relatively smaller chewing effort. The estimate of bite weight in the field based on the sod depletion curves was validated by an independent estimate derived from the chew to bite ratio. Bite weight estimates that ignored feeding station depletion were significantly greater than the independent estimates. We conclude that the sod grazing technique is an adequate tool to investigate food intake and forage depletion by grazing. It shows promise as a tool to explicitly scale up of foraging behaviour from the level of the feeding station to that of larger patches.     

Dietary intake of nickel and zinc by young children – Results from food duplicate portion measurements in comparison to data calculated from dietary records and available data on levels in food groups

The daily dietary intake of nickel (Ni) and zinc (Zn) by 42 young children, 21 boys and 21 girls, from 4 to 7 years of age, living in urban and rural areas of Germany and having different food consumption behaviour, was determined by the duplicate method with a 7-day sampling period. Dietary records were also kept by the children's parents for the 7-day sampling period. Individual reported food items were identified, assigned to food groups and, together with known Ni and Zn concentrations of foodstuffs, daily intake rates were calculated. The same method was used for calculations of the energy, fat, protein and carbohydrate intake rates.The levels in the food duplicates, determined by atomic absorption spectrometry, were in the range of 69–2000 μg Ni/kg_{dry weight} (geometric mean (GM): 348) and 7.1–43 mg Zn/kg_{dry weight} (GM: 17.5). Daily intake rates based on the 294 individual food duplicate analyses were 12–560 μg Ni/d (GM: 92.3) and 1.5–11 mg Zn/d (GM: 4.63). The results from the dietary records were 35–1050 μg Ni/d (GM: 123) and 1.7–15 mg Zn/d (GM: 5.35).The results of the daily intake rates from both methods showed a correlation with regard to Zn (r=0.56), but no correlation was found between either the Ni intake rates determined with both methods or between the Ni intake rates measured by the duplicate method and calculated intake rates from the dietary records of energy, fat, protein, carbohydrates or drinking water. In the case of nickel, the discrepancies between the methods lead one to suppose that the main factors influencing Ni intake by food are not directly caused by easily assessable food ingredients themselves. It is possible that other factors, such as contaminated drinking water or the transition of Ni from kettles or other household utensils made from stainless steel into the food, may be more relevant. In addition there are some foodstuffs with great variations in concentrations, often influenced by the growing area and environmental factors. Further, some food groups naturally high in Nickel like nuts, cocoa or teas might not have been kept sufficient within the records. In summary, the dietary record method gave sufficient results for Zn, but is insufficient for Ni.Based on the food duplicate analysis, children living in urban areas with consumption of food products from a family-owned garden or the surrounding area and/or products from domestic animals of the surrounding area had about one-third higher Ni levels in their food than children either living in an urban area or children consuming products exclusively from the supermarket. Only slight differences were found with regard to Zn.Compared to the recommendations of the German Society of Nutrition (DGE) (25–30 μg Ni/d and 5.0 mg Zn/d), the participants of the study had a clearly increased Ni and, in view of the geometric mean value, a nearly adequate Zn intake. Health risks are especially given with regard to the influence of nickel intake by food on dermatitis for nickel-sensitive individuals.     

Variation in nutrient intake of infants and its implications for collecting reliable dietary intake data

Sources of variance in dietary intake data for infants in the fourth to sixth months of life were examined. Twenty-eight mothers of infants in the Special Supplemental Food Program for Women, Infants, and Children gave 24-hr recall information on their infants' diets on 4 random days over approximately 1 month. ANOVA found no day of the week or sequence effects on nutrient variation. Variance was partitioned into between- and within-subject (residual) components. Interindividual variation exceeded intraindividual variation for all nutrients except vitamin C. Variance ratios ranged from 0.3 to 1.3. Calculations of 95% confidence limits for group and individual mean intakes indicated that, whereas a single recall would estimate the group mean within 20% for most nutrients, five recalls would be necessary for the same accuracy in individual means. Magnitude and patterning of variance components differ substantially from those found in studies of adults, suggesting that infant data collection strategies should be tailored to the unique nature of the infant diet.     

Predicting and correcting bias caused by measurement error in line transect sampling using multiplicative error models

Line transect sampling is one of the most widely used methods for animal abundance assessment. Standard estimation methods assume certain detection on the transect, no animal movement, and no measurement errors. Failure of the assumptions can cause substantial bias. In this work, the effect of error measurement on line transect estimators is investigated. Based on considerations of the process generating the errors, a multiplicative error model is presented and a simple way of correcting estimates based on knowledge of the error distribution is proposed. Using beta models for the error distribution, the effect of errors and of the proposed correction is assessed by simulation. Adequate confidence intervals for the corrected estimates are obtained using a bootstrap variance estimate for the correction and the delta method. As noted by Chen (1998, Biometrics 54, 899-908), even unbiased estimators of the distances might lead to biased density estimators, depending on the actual error distribution. In contrast with the findings of Chen, who used an additive model, unbiased estimation of distances, given a multiplicative model, lead to overestimation of density. Some error distributions result in observed distance distributions that make efficient estimation impossible, by removing the shoulder present in the original detection function. This indicates the need to improve field methods to reduce measurement error. An application of the new methods to a real data set is presented.     

Modelling interactions of food quality and quantity in homeostatic consumers

1. Boundaries between growth limitation by carbon (C) and phosphorus (P) in homeostatic heterotrophic consumers such as zooplankton will vary as demands on these two elements vary, as they should at different food quantities. At very low food quantity when production is close to zero, metabolic requirements (for carbon) become more important than growth requirements (for carbon and phosphorus in fixed proportion). Thus, the boundary separating C-and P-limited growth should be at a higher C : P ratio at low food quantity than at high food quantity.
2. A model including both metabolism and growth indicates that consumer growth should differ between foods of high vs. low phosphorus concentration only when food quantity is above a certain level. Thus, two foods might give identical consumer growth rates at low food quantity but give different consumer growth at higher quantity.
3. Solution of the model using parameters based on 2 mm Daphnia compared with a survey of C and P in seston of marine and freshwater sites supports earlier conclusions of the potential importance of food quality constraints on Daphnia growth.     

Bombesin reduces food intake of normal and hypothalamically obese rats and lowers body weight when given chronically

Bombesin is a peptide hormone reported to reduce meal size when administered in rats. In the first experiment, synthetic bombesin was injected subcutaneously into normal rats and obese rats with lesions of the ventromedial hypothalamus just prior to the presentation of food. A dose-dependent suppression of meal size occurred for both groups, showing that the peptide has this action in obese as well as normal animals. In a second experiment, a conditioned taste aversion was not formed with a dose of bombesin which suppressed meal size by approximately 50% while the animals did develop an aversion with a dose of LiCl reported to reduce meal size equivalently. In a third experiment, rats were placed on a feeding schedule where they received three 30-min meals each day. After weights had stabilized under this paradigm, bombesin was administered just prior to each meal for six days. The bombesin caused a consistent suppression of meal size when the animals were allowed 30-min meals such that the rats lost weight over the six-day period. When this experiment was repeated with 60-min meals apparent tolerance developed to these actions of bombesin.