First Hour Of Feeding Research Articles

Are Yeast Autolysate Attractants for Ceratitis Species (Diptera: Tephritidae) in South Africa More Attractive and Palatable Than a Currently Used Protein Attractant?

Due to increasing usage of copper fungicides in citrus orchards shortly before the application of protein baits for fruit fly control and the risk of this combination causing fruit phytotoxicity, an investigation of attractants containing higher amounts of yeast autolysate rather than protein hydrolysate was conducted. A commercial yeast autolysate from Australia was less attractive than a South African product HymLure (with a mixture of autolysate and hydrolysate) to three Ceratitis species: Ceratitis capitata (Wiedemann), Ceratitis rosa s.s. Karsch, and Ceratitis cosyra (Walker). Other custom-formulated autolysates were also inferior to HymLure for these species. Consumption of autolysates during the first hour of feeding was similar to that of HymLure. The inferior attraction of these three species of fruit flies to autolysates, relative to one containing hydrolysate, did not warrant further investigation of autolysates for use in baits to control these quarantine pests.

Re-examination of Dietary Amino Acid Sensing Reveals a GCN2-Independent Mechanism.

SUMMARYAnimals cannot synthesize nine essential amino acids (EAAs) and must therefore obtain them from food. Mice reportedly reject food lacking a single EAA within the first hour of feeding. This remarkable phenomenon is proposed to involve post-ingestive sensing of amino acid imbalance by the protein kinase GCN2 in the brain. Here, we systematically re-examine dietary amino acid sensing in mice. In contrast to previous results, we find that mice cannot rapidly identify threonine- or leucine-deficient food in common feeding paradigms. However, mice attain the ability to identify EAA-deficient food following 2 days of EAA deprivation, suggesting a requirement for physiologic need. In addition, we report that mice can rapidly identify lysine-deficient food without prior EAA deficit, revealing a distinct sensing mechanism for this amino acid. These behaviors are independent of the proposed amino acid sensor GCN2, pointing to the existence of an undescribed mechanism for rapid sensing of dietary EAAs.

A Physiological Stimulating Factor of Water Intake during and after Dry Forage Feeding in Large-type Goats.

When ruminants consume dry forage, they also drink large volumes of water. The objective of this study was to clarify which factor produced when feed boluses enter the rumen is mainly responsible for the marked increase in water intake in the second hour of the 2 h feeding period in large-type goats fed on dry forage for 2 h twice daily. Six large-type male esophageal- and ruminal-fistulated goats (crossbred Japanese Saanen/Nubian, aged 2 to 6 years, weighing 85.1±4.89 kg) were used in two experiments. In experiment 1, the water deprivation (WD) control and the water availability (WA) treatment were conducted to compare changes in water intake during and after dry forage feeding. In experiment 2, a normal feeding conditions (NFC) control and a feed bolus removal (FBR) treatment were carried out to investigate whether decrease in circulating plasma volume or increase in plasma osmolality is mainly responsible for the marked increase in water intake in the second hour of the 2 h feeding period. The results of experiment 1 showed that in the WA treatment, small amounts of water were consumed during the first hour of feeding while the majority of water intake was observed during the second hour of the 2 h feeding period. Therefore, the amounts of water consumed in the second hour of the 2 h feeding period accounted for 82.8% of the total water intake. The results of experiment 2 indicated that in comparison with the NFC control, decrease in plasma volume in the FBR treatment, which was indicated by increase in hematocrit and plasma total protein concentrations, was higher (p<0.05) in the second hour of the 2 h feeding period. However, plasma osmolality in the FBR treatment was lower (p<0.05) than compared to the NFC control from 30 min after the start of feeding. Therefore, thirst level in the FBR treatment was 82.7% less (p<0.01) compared with that in the NFC control upon conclusion of the 30 min drinking period. The results of the study indicate that the increased plasma osmolality in the second hour of the 2 h feeding period is the main physiological stimulating factor of water intake during and after dry forage feeding in large-type goats.

Increased availability of leucine with leucine-rich whey proteins improves postprandial muscle protein synthesis in aging rats

Objective We previously found that aging was characterized by a decreased sensitivity of muscle protein synthesis to leucine and that a free leucine-supplemented diet corrected this defect in old rats and elderly humans. The present experiment was undertaken to evaluate the efficiency of selected leucine-rich proteins to stimulate postprandial muscle protein synthesis in old rats to optimize nutritional protein support in the elderly. Methods Sixty rats (22 mo old) received an experimental meal for the first hour of feeding and a standard diet for the rest of the day for 30 d. Experimental meals contained milk proteins that differed in leucine content: β-lactoglobulin (14.5% leucine), Prolacta (13.4%), α-lactalbumin (10.9%), and casein (10%). As a control, a fifth group was added that received herring flour protein (7.3% leucine). Muscle protein synthesis was determined in vivo in the postprandial state at the end of the 30-d nutritional period using the flooding dose method (1- 13C phenylalanine). Results Leucine intake and plasma leucine concentrations were significantly increased in rats fed meals containing the leucine-rich proteins (i.e., β-lactoglobulin and Prolacta). As previously observed with free leucine-supplemented meals, postprandial muscle protein synthesis was significantly improved in rats fed the meals containing the leucine-rich proteins. Interestingly, the beneficial effect was maintained after the 30-d supplementation. Conclusion The results indicated that leucine-rich proteins were efficient in improving muscle protein synthesis in old rats. Thus, nutritional supplements containing such proteins may be efficient in preventing sarcopenia in the elderly and would represent a safe and optimized nutritional strategy. However, further experiments are necessary to determine the duration of such nutritional support to obtain a significant protein gain in muscle.

Effect of synchronizing the rate of dietary energy and nitrogen release on rumen fermentation and microbial protein synthesis in sheep

SUMMARYThe effects of two diets formulated to be either synchronous or asynchronous with respect to the hourly supply of energy and nitrogen on rumen fermentation and microbial protein synthesis were studied in sheep.In Expt 1, the insitudegradation characteristics of nitrogen (N), organic matter (OM) and carbohydrate (CHO) fractions were determined in winter wheat straw, winter barley, malt distillers dark grains rapeseed meal and fishmeal. The feeds exhibited a large range in degradability characteristics of the nitrogen and energy-yielding fractions.A computer program was developed based upon the raw material degradation characteristics obtained from the above studies. The program was used to formulate two diets with similar metabolizable energy (9·5 MJ/kg DM) and rumen degradable protein contents (96 g/kg DM) but to be either synchronous (diet A) or asynchronous (diet B) with respect to the hourly rate of release of N and energy. The program was used to predict the hourly release of N, OM and CHO and the molar production of volatile fatty acids (VFA).In Expt 2, the two diets were fed to four cannulated sheep at the rate of 1 kg/day in four equal portions, in two periods, using a change-over design. Rumen ammonia concentrations followed the predicted rate of N degradation. A maximum concentration of 10·5 and 7 mM for diets A and B respectively was achieved within the first hour of feeding which then fell to 7 and 3 mM respectively. Rumen VFA proportions were more stable for the synchronous diet (A) than the asynchronous diet (B) and were more stable than predicted for both diets. True ruminal degradation of OM and CHO was similar for both diets and close to that predicted, although fibre degradability in diet A was 30% lower than predicted due to a reduction in both cellulose and hemicellulose digested. Microbial protein production was estimated simultaneously with L-[4,5–3H]leucine and a technique based on cytosine. Estimates varied with marker but mean values indicated a 27% greater production of microbial N (g N/kg DM I) with the synchronous diet (A) and an average improvement in microbial protein efficiency (g N/kg OM truly degraded or CHO apparently degraded) of 13%, although neither difference was significant. There was evidence of a greater recycling of N in the animals and a significantly lower content of rumen degradable protein when the sheep were fed the asynchronous diet (B).The results are consistent with the view that synchronizing the rate of supply of N and energyyielding substrates to the rumen micro-organisms based upon ingredientin situdegradation data can improve microbial protein flow at the duodenum and the efficiency of microbial protein synthesis.

Food intake and selection pattern of rats treated with dexfenfluramine, fluoxetine and RU 24969

The effects of two indirect (dexfenfluramine and fluoxetine) and one direct (RU 24969) serotonergic agonists on diet selection over a 12-hr period were examined. Rats were habituated to eat, during the dark period, from two isoenergetic diets that differed in carbohydrate and protein content. Drugs were injected intraperitoneally at 1845 hr, 15 min prior to food access. The drugs exerted their effects mainly during the first hour of feeding (1900–2000 hr). At this time, a selective suppression in intake of the high carbohydrate-low protein diet was the most prominent characteristic of all three serotonergic agonists. This macronutrient specific effect was particularly strong at low dosages (dexfenfluramine, fluoxetine and RU 24969: 0.5 2.0 and 1.0 mg/kg, respectively). With time, as the effect of drugs wore off, diet selection pattern became more variable. The fact that both indirect 5-HT agonists and a direct selective 5-HT receptor agonist share a specific behavioral effect provides additional support for the role of serotonin in the control of macronutrient specific appetites.

Food Intake and Choice in Lean and Obese Zucker Rats after Intragastric Carbohydrate Preloads

Feeding behavior in response to a carbohydrate preload was determined in lean and obese Zucker rats. Rats were adapted to a schedule of feeding during a 12-h daily dark period. Carbohydrate preloads (cornstarch in water) were given by intragastric intubation 30 min before rats had access to a choice of two diets that differed in their protein and carbohydrate contents. Behavioral responses of lean rats to carbohydrate preloads were prompt and selective. In the first hour of feeding, reduction in intake, mainly of the high carbohydrate-low protein diet, more than compensated for the energy content of the preload. In contrast, obese rats failed to achieve a similar degree of compensation to the energy surplus from the carbohydrate preload during the first hour of feeding. Also, their decreases in food intake were nonselective. In general, it took obese rats two or more hours to adjust their feeding behavior in response to a carbohydrate preload. Increasing the size of the preload did not improve the overall response of obese rats, but an extra 30-min lapse between preload and food access led to selective suppression in first-hour intake from the high carbohydrate-low protein diet. These findings suggest that altered food intake and selection behavior of the obese Zucker rat may be, in part, due to a delay in response to physiologic and metabolic changes arising from carbohydrate ingestion.

Influence of regimen and insulinemia on orexigenic effects of GRF 1–44 in sheep

The effects of intracerebroventricular (ICV) and intravenous (IV) administration of human GRF 1–44 on feeding behavior were tested in hay- and concentrate-fed non lactating ewes. Administered ICV 5 min prior to hay disposal in 16 hr fasted ewes, GRF 1–44 increased the first 3 hr and daily (8 hr) food intake by 25.3 and 24.5% respectively; this corresponded to a higher rate of ingestion during the first 3 hr. Similar effects on feeding behavior were observed after IV administration of a 10-times greater dose of GRF 1–44 (1 μg·kg −1), with daily hay consumption increasing from 1125±44 g (control) to 1407±91 g. In contrast, food intake of concentrates was significantly ( p<0.05) higher only during the first hour of feeding and the daily food intake was unchanged. Both ICV (40 mU·kg −1) and IV (400 mU·kg −1) administrations of insulin did not affect feeding behavior per se, but suppressed the increased food intake of hay induced by IV GRF 1–44. It is concluded that the orexigenic effects of GRF 1–44 are probably centrally mediated and depend on regimen and digestive status. It is suggested that the insulin response to a meal of concentrates may be responsible for the early blockade of the orexigenic effects of GRF.

Food intake and selection after peripheral tryptophan

Two studies investigated the effects of peripheral (IP) administration of the dietary indispensible amino acid tryptophan, on food intake and macronutrient selection in rats adapted to a 12 hr nocturnal feeding period and a choice of 10% and 60% casein diets. In a dose-response study (35, 55, 75, 95, 115 mg/kg), the threshold dose of 75 mg/kg produced a significant reduction in total food intake (3.6 to 2.3 g, p<0.05) during the first hour of feeding. The reduction in carbohydrate intake (2.1 vs. 1.2 g, p<0.05) was greater than that for protein intake (1.6 vs. 1.1 g, p<0.05). Twelve hr total food intake was also decreased (20.9 to 19.5 g, p<0.05) and this was attributable to decreased carbohydrate intake (13.2 to 11.8 g, p<0.05). In a second study designed to determine if tryptophan's effects were mediated by the central nervous system, brain tryptophan uptake was blocked by co-injecting valine with tryptophan. The significant reduction in first hour total food intake by tryptophan was not prevented by co-injection of an equal quantity of valine (3.5 to 1.8 g, p<0.05). Again the suppression of carbohydrate intake (2.0 to 0.9 g p<0.05) was greater than that for protein intake (1.5 to 0.9 g, p<0.05). This dose of valine significantly reduced brain tryptophan uptake by 16% (21.3 to 17.8 μg/g, p<0.05) and when administered alone did not affect first hour total food intake (3.1 vs 3.2 g). A higher dose of valine (300 mg/kg) produced a larger decrease in brain tryptophan (15.9 to 11.7 μg/g, p<0.05), but when administered alone also significantly decreased food intake (2.9 to 0.7 g, p<0.05). Thus the site and mechanism of action for tryptophan's effects could not be elucidated. It was concluded that intraperitoneal administration of tryptophan suppresses total food intake, with a small but significantly greater effect on carbohydrate intake compared to protein intake.

Experimental dissociation of food intake and plasma β-endorphin following 2-deoxy-D-glucose in rats

The present studies were undertaken to further assess the role of plasma β-endorphin (β-EP) in the hyperphagia induced by the glucose antimetabolite, 2-deoxy-D-glucose (2-DG). Plasma concentrations of immunoreactive β-EP (ir-β-EP) were measured at the end of the first hour of feeding in all animals treated with 400 mg/kg 2-DG. Previous studies had shown a consistent, positive association between 2-DG hyperphagia and plasma ir-β-EP concentrations, but the present data revealed dissociations between hyperphagia and plasma ir-β-EP. Dexamethasone administration blocked the 2-DG-induced rise in plasma ir-β-EP, but had no effect on the 2-DG hyperphagia measured at 1 hour. Forced drinking of a 2% NaCl solution decreased 2-DG hyperphagia, but not the 2-DG induced rise in plasma ir-β-EP. Thus, elevations in plasma ir-β-EP are not necessary for the full expression of 2-DG-induced hyperphagia in dexamethasone-treated rats. Furthermore, decreased feeding responses to 2-DG could coexist with increased levels of plasma ir-β-EP in NaCl-treated normal rats. Elevations in plasma ir-β-EP do not appear to be the critical opiate link in 2-DG induced hyperphagia.

Food intake after intragastric meals of short-, medium-, or long-chain triglyceride

Food-deprived Sprague-Dawley rats were given equicaloric intragastric infusions of mixed meals consisting largely of short- (SCT), medium- (MCT), or long-chain triglyceride (LCT). When animals were allowed to feed 20 min after infusion, there was an immediate reduction of food intake that was sustained over the 2 hr feeding period. During the first hour of feeding, the SCT, which is digested and absorbed more rapidly than the MCT or the LCT, was more effective per calorie in reducing food intake than these longer-chain triglycerides. However, during the second hour, cumulative intakes after the different triglyceride infusions were not significantly different. Equicaloric infusions of the MCT and the LCT resulted in equivalent reductions of food intake at all times. The satiety effects of these two triglycerides appear to be related to their caloric properties rather than to chain length. Since the LCT reduced food intake before the absorbed fat could have entered the blood to stimulate satiety·signals, this satiety effect may be mediated by a gastroenteric signal. None of the triglyceride infusions resulted in a conditioned taste aversion suggesting that food intake was reduced through normal satiety rather than through discomfort.

Motor events in equine large colon.

The equine large colon is the major cellulose-fermentation locus of these species. The area of juncture of the ventral and dorsal divisions of the equine large colon was characterized, in 13 chronic unanesthetized animals and in 25 in vitro preparations, as an area of resistance to aboral flow. This is a probable pacemaker area. The reservoir function of this part of the colon is apparently facilitated by the presence of a pacemaker at this level. There was a general rise in recorded intraluminal pressure peaks during the first hour of feeding. This characteristic was not altered after resection of the extrinsic nerve supply. Electrical stimulation of the extrinsic nerve net in conscious animals at times mimicked the groups of intraluminal pressure peaks seen at the beginning of feeding.

Kinetic studies of food intake and sucrose solution preference by rats treated with low doses of Δ 9-tetrahydrocannabinol

The experiments to be described were undertaken to determine time-related effects of single low-dose levels of Δ9-tetrahydrocannabinol on food and sucrose solution consumption of rats. One hour after receiving oral doses of 0.00, 0.25, and 0.40 mg/kg, rats were offered free access to wet and dry chow and one of five concentrations of sucrose solution and water. Intakes were recorded after various time intervals during the 24 hr following treatment. Rats treated with Δ9-tetrahydrocannabinol consumed dry chow at significantly higher rates, during the first hour of feeding, and the strongest sucrose solution, at significantly higher rates during the first half-hour of drinking, than controls. Treatment group differences in food and sucrose solution intakes existed throughout the 24-hr period. In both studies, rats treated with the drug initially consumed kilocalories from food and sucrose at higher rates than controls. Rats compensated for early large kilocalorie intakes by decreasing consumption rates later to yield a total 24-hr intake which nearly matched control values. The findings suggest that low doses of Δ9-tetrahydrocannabinol produce dose- and time-dependent effects on food and sucrose solution intake and preference and on kilocalorie consumption rates in rats during the 24-hr period following administration of the drug.

The effect of feeding with a tryptophan-free amino acid mixture on rat liver magnesium ion-activated deoxyribonucleic acid-dependent ribonucleic acid polymerase.

1. The Widnell & Tata (1966) assay method for Mg(2+)-activated DNA-dependent RNA polymerase was used for initial-velocity determinations of rat liver nuclear RNA polymerase. One unit (U) of RNA polymerase was defined as that amount of enzyme required for 1 mmol of [(3)H]GMP incorporation/min at 37 degrees C. 2. Colony fed rats were found to have a mean RNA polymerase activity of 65.9muU/mg of DNA and 18h-starved rats had a mean activity of 53.2muU/mg of DNA. Longer periods of starvation did not significantly decrease RNA polymerase activity further. 3. Rats that had been starved for 18h were used for all feeding experiments. Complete and tryptophan-deficient amino acid mixtures were given by stomach tube and the animals were killed 15-120min later. The response of RNA polymerase to the feeding with the complete amino acid mixture was rapid and almost linear over the first hour of feeding, resulting in a doubling of activity. The activity was still elevated above the starvation value at 120min after feeding. The tryptophan-deficient amino acid mixture produced a much less vigorous response about 45min after the feeding, and the activity had returned to the starvation value by 120min after the feeding. 4. The response of RNA polymerase to the feeding with the complete amino acid mixture was shown to occur within a period of less than 5min to about 10min after the feeding. 5. Pretreatment of the animals with puromycin or cycloheximide was found to abolish the 15min RNA polymerase response to the feeding with the complete amino acid mixture, but the activity of the controls was unaffected. 6. The characteristics of the RNA polymerase from 18h-starved animals and animals fed with the complete or incomplete amino acid mixtures for 1h were examined. The effects of Mg(2+) ions, pH, actinomycin D and nucleoside triphosphate omissions were determined. The [Mg(2+)]- and pH-activity profiles of the RNA polymerase from the animal fed with the complete mixture appeared to differ from those of the enzyme from the other groups, but this difference is probably not significant. 7. [5-(3)H]Orotic acid incorporation by rat liver nuclei in vivo was shown to be affected by the amino acid mixtures in a similar manner to the RNA polymerase. 8. The tryptophan concentrations of plasma and liver were determined up to 120 min after feeding with the amino acid mixtures. Feeding with the complete mixture produced a rapid increase in free tryptophan concentrations in both plasma and liver, but feeding with the incomplete mixture did not alter the plasma concentration. The liver tryptophan concentration increased at about 45min after feeding with the tryptophan-deficient diet. 9. There was a good correlation between the liver tryptophan concentration and RNA polymerase activity in all groups of animals. 10. It was concluded that the rat liver nucleus responded to an increase in amino acid supply by increased synthesis of RNA as a result of synthesis of RNA polymerase de novo. The correlation of tryptophan concentration and RNA polymerase activity appears to reflect the general amino acid concentration required to support hepatic protein synthesis and to produce new RNA polymerase. This new polymerase appears to differ from the basal RNA polymerase by its rapid synthesis and destruction, which may be a means of regulating RNA synthesis by the amino acid concentration in the liver.

STUDIES ON THE FEEDING OF MYZUS PERSICAE (SULZ.) ON RADIOACTIVE PLANTS

Adult apterae of Myzus persicae (Sulz.), were fed, after a period of fasting, on leaves containing radioactive phosphorus. The weight of sap imbibed by the aphids after varying feeding times was estimated by relating their radioactivity, at the end of each feeding period, to the activity per unit fresh weight of the leaf lamina on which they fed. The calculations were made on the assumption that 32P is uniformly distributed in the leaf tissues.The mean rates of uptake so estimated were about 10 μg. of sap for the first hour of feeding; 40 μg/hr. between 1 and 4 hr. feeding, and 17 μg./hr. between 6 and 24 hr. feeding. The decrease in apparent rate of uptake with the longer feeding times is attributed to loss of 32P in nymphs born during the feeding period.When aphids were fed on seedlings raised in water culture solution containing 32P no activity was detected after 5 min. feeding and an insignificant fraction after 15 min., but when the isotope was introduced by immersing the leaves for several days in the culture solution, aphids fed for 5 and 15 min. became appreciably active.The increase in rate of uptake after 1 hr. of feeding indicates that aphids do not start to feed normally until they reach the phloem, but the activity after short feeding times suggests that previously starved aphids feed to some extent on other tissues, possibly only on the epidermis.