HE Diet Research Articles

Low dietary protein intake during pregnancy differentially affects mitochondrial copy number in stromal vascular cells from subcutaneous versus visceral adipose tissue in the offspring

The present study examined the influence of protein intake during pregnancy on mitochondrial metabolism in stromal vascular cells from subcutaneous (SVSu) and visceral (SVVi) adipose tissue of offspring fed a high fat diet. Obese‐prone Sprague‐Dawley rats were fed diets containing either 8% or 20% protein throughout pregnancy and lactation. Male weanling offspring were fed diets with 20% protein and and either 10% fat (NF) or 45% fat (HF) for 12 wks. The mitochondrial copy number showed a 5X increase in SVCu in offspring fed HE whose dams were fed normal protein compared to a 1.5X increase in offspring in offspring fed HE but whose dams were fed low protein. Neither pre‐ nor postnatal diets influenced mitochondrial number in SVVi. This finding suggests that prenatal protein intake and postnatal fat intake may differentially affect mitochondrial metabolism in SVSu versus SVVi. Although dietary treatments did not affect cellular respiration as measured with a Seahorse XF24 Analyzer with 5 mM glucose and 1mM pyruvate using cultured cells, SVSu exhibited lower maximum O2 consumption and lower reserve respiratory capacity than SVVi. Lower reserve capacity suggests that SVSu in offspring may not be able to sufficiently respond metabolically to HE diets and adapt by increasing mitochondrial biogenesis. Low prenatal protein intake during pregnancy may impair this adaptation in the offspring.

Daily feed intake, energy intake, growth rate and measures of dietary energy efficiency of pigs from four sire lines fed diets with high or low metabolizable and net energy concentrations.

A trial was conducted to: i) evaluate the BW growth, energy intakes and energetic efficiency of pigs fed high and low density diets from 27 to 141 kg BW, ii) evaluate sire line and sex differences when fed both diets, and iii) to compare ME to NE as predictor of pig performance. The experiment had a replicated factorial arrangement of treatments including four sire lines, two sexes (2,192 barrows and 2,280 gilts), two dietary energy densities and a light or heavy target BW, 118 and 131.5 kg in replicates 1 to 6 and 127 and 140.6 kg in replicates 7 to 10. Pigs were allocated to a series of low energy (LE, 3.27 Mcal ME/kg) corn-soybean meal based diets with 16% wheat midds or high energy diets (HE, 3.53 to 3.55 Mcal ME/kg) with 4.5 to 4.95% choice white grease. All diets contained 6% DDGS. The HE and LE diets of each of the four phases were formulated to have equal lysine:Mcal ME ratios. Pigs were weighed and pen feed intake (11 or 12 pigs/pen) recorded at 28-d intervals. The barrow and gilt daily feed (DFI), ME (MEI) and NE (NEI) intake data were fitted to a Bridges function of BW. The BW data of each sex were fitted to a generalized Michaelis-Menten function of days of age. ME and NE required for maintenance (Mcal/d) were predicted using functions of BW (0.255 and 0.179 BW^0.60 respectively). Pigs fed LE diets had decreased ADG (915 vs. 945 g/d, p<0.001) than pigs fed HE diets. Overall, DFI was greater (p<0.001) for pigs fed the LE diets (2.62 vs. 2.45 kg/d). However, no diet differences were observed for MEI (8.76 vs. 8.78 Mcal/d, p = 0.49) or NEI (6.39 vs. 6.44 Mcal/d, p = 0.13), thereby indicating that the pigs compensated for the decreased energy content of the diet. Overall ADG:DFI (0.362 vs. 0.377) and ADG:Mcal MEI (0.109 vs. 0.113) was less (p<0.001) for pigs fed LE compared to HE diets. Pigs fed HE diets had 3.6% greater ADG:Mcal MEI above maintenance and only 1.3% greater ADG:Mcal NEI (0.152 versus 0.150), therefore NEI is a more accurate predictor of growth and G:F than MEI. Pigs fed HE diets had 3.4% greater ADG:Mcal MEI and 0.11% greater ADG:NEI above maintenance than pigs fed LE diets, again demonstrating that NEI is a better predictor of pig performance than MEI. Pigs fed LE diets had similar daily NEI and MEI but grew slower and less efficiently on both ME and NE basis than pigs fed HE diets. The data suggest that the midds NE value (2.132 Mcal/kg) was too high for this source or that maintenance was increased for pigs fed LE diets.

Effects of feed, feeding regime and growth rate on flesh quality, connective tissue and plasma hormones in farmed Atlantic salmon ( Salmo salar L.)

Maintaining control of the harvest quality of the edible product is becoming increasingly important for successful fish farming operations. The present experiment was designed to investigate interrelations, and possible conflicts, between high rearing intensity and maintaining desired quality of the end product, and to explore the mechanism underpinning quantitative and qualitative aspects of Atlantic salmon ( Salmo salar L.) farming. Two isonitrogenous feeds (340 g protein kg −1 feed) comprising either high energy (HE; 22.1 MJ kg −1) or low energy (LE; 19.3 MJ kg −1) were fed to 2.4 kg fish differing in whole body energy status until harvest. Over this period both HE and LE feeds were fed to satiation (Sat) or by moderately reduced (Res) ration to create four dietary treatments; HE-Sat, HE-Res, LE-Sat, and LE-Res. Satiation feeding induced higher energy intake, faster growth rates, elevated red colour intensity (a*-value), softer flesh, and higher liquid loss compared to restricted feeding. At satiation feeding, increased digestible feed energy lowered the feed intake without compromising growth. LE diet resulted in reduced fat accumulation without compromising growth, and feeding LE feed restrictively had the largest effect (~ 2% unit) on fat accumulation. Individual growth rates (TGC 3) correlated positively to fat deposition (r 2 = 0.38), but less evident to fillet firmness (r 2 = 0.16). There was a significant positive correlation between the hydroxylysyl pyridinoline (PYD) cross-link concentration and fillet firmness, where PYD explained 28% of the total variation. A multiple linear regression (MLR) analysis revealed PYD as the only factor influencing fillet firmness significantly, whilst TGC 3, pre-rigor muscle pH, fillet fat, alkaline-soluble and -insoluble hydroxyproline (HYP), and plasma leptin and ghrelin had no significant effect on fillet firmness. The incidence of gaping was low across feed treatments, and gaping scores were not correlated to fillet firmness nor influenced by the applied feed or feeding regime over the experiment. The decrease in plasma leptin levels following long-term HE diet suggests that leptin is linked to energy balance in salmon, but may not act as an adiposity signal. From the present experiment it is concluded that both feed energy and feeding regime can be used to manage important quality attributes of Atlantic salmon, and that cross-linking of collagen fibres is an important factor to maintain desired fillet firmness.

Growth, metabolic status and ovarian function in buffalo ( Bubalus bubalis) heifers fed a low energy or high energy diet

The aim was to establish the capacity of buffalo heifers to adapt their metabolic requirements to a low energy diet. Murrah buffalo ( Bubalus bubalis) heifers undergoing regular estrous cycles were randomly assigned by age, live weight (LW) and body condition score (BCS) to a high energy group (HE, 5.8 milk forage units (MFU)/day, n = 6) or low energy group (LE, 3.6 MFU/day, n = 6). Circulating concentrations of metabolic substrates, metabolic hormones and reproductive hormones were determined weekly for 19 weeks. Ovarian follicular characteristics and oocyte parameters were also ascertained weekly. Heifers fed the LE diet had a better dry matter conversion than heifers fed the HE diet and the calculated daily energy provision was negative for heifers fed the LE diet (−0.248 MFU) and positive for heifers fed the HE diet (5.4 MFU). Heifers fed the HE diet had an increase in 50 kg LW over the duration of the study whereas LW remained constant for heifers fed the LE diet. The BCS of heifers fed the HE diet (4.2) was greater ( P < 0.05) than the BCS for heifers fed the LE diet (3.4). Heifers fed the HE diet had greater ( P < 0.05) circulating concentrations of metabolic substrates (glucose, total cholesterol and HDL cholesterol) and metabolic hormones (insulin, glucagon, leptin and T3) compared with heifers fed the LE diet. There were no significant differences in circulating reproductive hormones between the two groups of heifers. Ovarian follicular characteristics were similar for the two groups of heifers while heifers fed the LE diet tended to have oocytes of reduced quality compared with heifers fed the HE diet. The most notable finding was that heifers fed the LE diet had a negative calculated daily energy provision but were able to maintain LW and reproductive activity. It was concluded that buffalo heifers may potentially have the capacity to undergo metabolic adjustment and reduce their energy requirements when dietary energy is limiting. This adaptive capacity would explain why buffaloes remain productive in environments that are limiting to other ruminants.

Three weeks of post-weaning exercise in DIO rats fed HE diet increases central leptin sensitivity and hypothalamic 125leptin receptor binding

Three weeks of post-weaning exercise in DIO rats fed HE diet increases central leptin sensitivity and hypothalamic 125leptin receptor binding

Effects of Temperature and Feed Energy on the Performance of Juvenile Red Drum

AbstractWe tested the hypothesis that the growth of fish exposed to high temperatures can be limited by available food energy whereas that of fish exposed to low temperatures can be limited by their metabolic capacity to exploit the available food energy. Under laboratory conditions we evaluated growth (%/d) and marginal metabolic scope (MMS; L·g−1·h−1) of juvenile red drum Sciaenops ocellatus exposed to two levels of dietary energy, low (LE; ∼4.1 kJ/g) and high (HE; ∼15.9 kJ/g), and to three temperatures, approximately 19, 25, and 29°C, for a period of 6 weeks. Growth rate and MMS increased with temperature, but only growth rate increased with dietary energy and then only at the higher two temperatures. The simulation model Ecophys. Fish was employed to elucidate experimental results potentially confounded by interactions between fish weight and the controlling effects of temperature on metabolism. The simulated and observed results both showed that performance is enhanced at higher temperatures, especially for fish consuming the HE diet. A subsequent 6‐week‐long experiment confirmed results for fish fed the two diets at ambient temperature (∼26°C) and sought to further resolve responses by examining body condition indices and proximate composition. Additionally, these fish were assayed for differential cortisol response to 15 min of confinement stress. The feed efficiency, hepatosomatic index, intraperitoneal fat ratio, and whole‐body fat of fish fed the LE diet were significantly lower than those of fish fed the HE diet, indicating relative energy malnutrition in the LE group. As with MMS, no apparent differential effect of feed energy on the pre‐ or poststress values of plasma cortisol was observed. These findings support the ideas that red drum obtain greater metabolic capacity when they are exposed to a near‐optimal temperature and that their ability to transform that capacity into growth is maximized only when they are provided a nutritious, high‐energy diet.

Energy and nutrient utilization of Atlantic cod, Atlantic salmon and rainbow trout fed diets differing in energy content

The growth and feed utilization of Atlantic cod (Gadus morhua) (437 g), Atlantic salmon (Salmo salar) (485 g) and rainbow trout (Oncorhynchus mykiss) (413 g) fed a diet (170 g kg−1 fat, 600 g kg−1 crude protein; LE) similar to that used in commercial cod production or one that was top dressed with additional fat (280 g kg−1 fat, 530 g kg−1 crude protein; HE), were compared in an 11-week trial. In the cod, relative feed intake was 41–58% and thermal growth coefficient 63% of that in the salmonids, but the feed efficiency ratio (FER) was 38% better (P ≤ 0.05). In contrast to the cod where there was no effect of diet on feed intake, growth or FER, both the salmon and trout fed the HE diet had greater feed intake than those fed the LE diet, but the effect of this was only positive for growth in the salmon. The cod retained more of the digested nitrogen (44.9 ± 2.7%) than the salmon (39.4 ± 0.8%), and both of these species retained more than the trout (33.6 ± 1.1%) (P ≤ 0.05). The retention of digested energy was significantly higher in the salmon (52.2 ± 0.9%) than in the trout (44.8 ± 1.1%), with the cod (44.9 ± 4.9%) not different from either of the other species. There were no differences between the species in the retention of absorbed phosphorus (65.9 ± 3.6%). There were very few dietary effects on nutrient utilization in this trial and, for the cod, this indicates that higher energy diets may be feasible for use in production.

Altered Hypothalamic Leptin, Insulin, and Melanocortin Binding Associated with Moderate-Fat Diet and Predisposition to Obesity

Rats with a genetic predisposition to develop diet-induced obesity (DIO) have a preexisting reduction in central leptin and insulin sensitivity. High-fat diets also reduce sensitivity to leptin, insulin, and melanocortin agonists. We postulated that such reduced sensitivities would be associated with decreased binding to the hypothalamic leptin, insulin, and melanocortin receptors in selectively bred DIO rats and in rats fed a high-energy (HE; 31% fat) diet for 7 wk. On HE diet, DIO rats gained 15% more weight and had 121% heavier fat pads and 70% higher leptin levels than low fat chow-fed DIO rats. Diet-resistant (DR) rats gained no more weight on HE diet but had 48% heavier fat pads and 70% higher leptin levels than chow-fed DR rats. Compared with DR rats, DIO (125)I-leptin binding was 41, 36, and 40% lower in the hypothalamic dorsomedial, arcuate, and dorsomedial portion of the ventromedial nuclei, respectively, and arcuate (125)I-insulin binding was 31% lower independent of diet. In contrast, hypothalamic melanocortin binding did not differ between DIO and DR rats. However, HE diet intake lowered lateral hypothalamic melanocortin-3 and melanocortin-4 receptor and hippocampal insulin binding of both DIO and DR rats and hypothalamic paraventricular nucleus melanocortin-4 receptor binding only in DR rats. Neither genotype nor diet affected substantia nigra or ventral tegmental area binding. These results corroborate our previous findings demonstrating a preexisting decrease in DIO hypothalamic leptin and insulin signaling and demonstrate that HE diet intake reduces hypothalamic melanocortin and hippocampal insulin binding.

Differential effects of exercise on body weight gain and adiposity in obesity-prone and -resistant rats

To determine the effect of exercise on weight gain and adiposity in obesity-prone and -resistant rats. Body weight gain, fat pad weights, food intake, plasma leptin and insulin levels were assessed in outbred male Sprague-Dawley rats, which remained sedentary or were given unrestricted access to running wheels either before or after they developed diet-induced obesity (DIO) or diet-resistance (DR) on a high energy (HE; 31% fat) diet. When fed a low fat (4.5%) chow diet, rats which would later develop DIO (n=6) after 3 weeks on HE diet ran the same amount as DR rats (n=6). Other rats were first made DIO (n=12) or DR (n=12) after 10 weeks on HE diet and then either kept sedentary or given running wheels for 4 weeks on HE diet. DIO and DR rats ran comparable amounts but only the DIO rats reduced their body weight gain, fat pad relative to body weights and plasma leptin levels significantly, compared to their sedentary controls. Exercise had no effect on food intake in either DIO or DR rats but reduced feed efficiency (weight gain/caloric intake) in both. Although DIO and DR rats ran similar amounts, the greater reduction in body weight gain and adiposity of exercising DIO rats suggests that they are more sensitive to some metabolic or physiologic system that prevents them from increasing their intake sufficiently to compensate for their net reduction in energy stores.

Fertility response of yearling beef heifers after prebreeding energy manipulation, estrous synchronization and timed artificial insemination

The effect of dietary energy and weight class on the fertility of yearling beef heifers (Angus, Hereford, and Angus × Hereford) was investigated over 2 years. In year 1, heifers ( n = 58) were classed as heavy (HW; ≥340 kg) or light weight (LW; <340 kg) and then assigned to receive either a low (LE; 0.23 kg/day) or high energy (HE; 0.68 kg/day) diet. In year 2, heifers ( n = 60) were also classified as heavy (≥335 kg) or light weight (<335 kg), but the energy content of the diet was raised so that heifers on the LE and HE were targeted to gain 0.46 and 0.79 kg/day, respectively. Heifers in the four groups, LELW ( n = 14 and 12), LEHW ( n = 16 and 17), HELW ( n = 13 and 15), and HEHW ( n = 15 and 16) received restricted amounts of concentrate (HE > LE) and free choice hay over 47 or 42 days (year 1 and year 2, respectively). To synchronize estrus, heifers were fed capsules containing MGA (0.5 mg/animal each day) beginning 11 days before the end of the feeding trial (day 0), PGF 2α (25 mg i.m.) and estradiol benzoate (Eβ; 400 μg i.m.) was given on days 8 and 10, respectively. Estrous behavior was observed (days 10 and 11) and all heifers were inseminated on day 11. Following AI, heifers were re-grouped and a bull was introduced (days 27–39) for the second service in both years. Pregnancy diagnosis for the first (days 41–42) and second services (days 69–97) was performed by transrectal ultrasonography. Transrectal ultrasonic observations of ovarian follicle number and size were completed for a subset of heifers ( n = 5–8) from each experimental group at the end of the feeding trial. The effect of year was not significant for any of the reproductive performance variables measured. The mean ADG was (0.72 ± 0.04 kg/day) and was greater in LW than HW heifers and in heifers in the HE than LE treatment groups ( P < 0.05). In heifers receiving the LE diet, ADG was lower in HW than LW heifers (weight × diet; P = 0.02; 0.54 ± 0.04 and 0.62 ± 0.03 kg/day for HW and LW heifers, respectively). The diameter of the largest follicle was greater in heifers receiving the HE diet ( P < 0.05; 11.3 ± 0.4 mm) than those on the LE diet (10.3 ± 0.3), and in LW ( P < 0.05) compared to HW heifers. The HE diet increased the size of the largest follicle in LW but not HW heifers (diet × weight, P < 0.05). The percentage of pubertal heifers at the end of the feeding period (59.3%), estrous response (56.4%), conception rate (47.7%), ovulation rate (88.9%), and first service pregnancy rate (36.2%) were not significantly affected by initial weight or diet. There was a tendency for first service pregnancy rates to be greater in LW than HW heifers consuming the LE diet (diet × weight, P < 0.1; 54.2 ± 15 and 30.3 ± 10% for LELW and LEHW heifers, respectively). Pregnancy rate after two services was greater ( P = 0.01) in LW (82 ± 10%) than in HW (64.5 ± 10%). The LE diet achieved moderate rates of gain and allowed high level of reproductive performance in LW but not HW heifers.

Abnormalities of leptin and ghrelin regulation in obesity-prone juvenile rats.

Rats selectively bred to develop diet-induced obesity (DIO) spontaneously gain more body weight between 5 and 7 wk of age than do those bred to be diet resistant (DR). Here, chow-fed DIO rats ate 9% more and gained 19% more body weight from 5 to 6 wk of age than did DR rats but had comparable leptin and insulin levels. However, 6-wk-old DIO rats had 29% lower plasma ghrelin levels at dark onset but equivalent levels 6 h later compared with DR rats. When subsequently fed a high-energy (HE; 31% fat) diet for 10 days, DIO rats ate 70% more, gained more body and adipose depot weight, had higher leptin and insulin levels, and had 22% lower feed efficiency than DR rats fed HE diet. In DIO rats on HE diet, leptin levels increased significantly at 3 days followed by increased insulin levels at 7 days. These altered DIO leptin and ghrelin responses were associated with 10% lower leptin receptor mRNA expression in the arcuate (ARC), dorsomedial (DMN), and ventromedial hypothalamic nuclei and 13 and 15% lower ghrelin receptor (GHS-R) mRNA expression in the ARC and DMN than in the DR rats. These data suggest that increased ghrelin signaling is not a proximate cause of DIO, whereas reduced leptin sensitivity might play a causal role.

Ontogeny of diet-induced obesity in selectively bred Sprague-Dawley rats.

Outbred Sprague-Dawley rats selectively bred for their propensity to develop diet-induced obesity (DIO) become heavier on low-fat diet than those bred to be diet resistant (DR) beginning at approximately 5 wk of age. Here we assessed the development of metabolic and neural functions for insights into the origins of their greater weight gain. From week 5 to week 10, chow-fed DIO rats gained 15% more body weight and ate approximately 14% more calories but had only slightly greater adiposity and plasma leptin than DR rats. From day 3 through week 10, DIO and DR rats had similar mRNA expression of arcuate nucleus neuropeptide Y, proopiomelanocortin, agouti-related peptide, and all splice variants of the leptin receptor (OB-R). When fed a high-energy (HE; 31% fat) diet, 7-wk-old DIO rats had a 240% increase in plasma leptin levels after only 3 days. Despite this early leptin rise, they maintained a persistent hyperphagia and became more obese than chow-fed DIO rats and DR rats fed chow or HE diet. Their failure to reduce caloric intake, despite high levels of leptin, suggests that selectively bred DIO rats might have reduced leptin sensitivity similar to that seen in the outbred DIO parent strain.

Effect of Dietary Modifications Designed to Reduce Early Growth Rate on Live Performance and on Incidence and Severity of Ascites in Two Commercial Broiler Strains When Maintained Under Low Ventilation or Low Temperature Models

Two studies were conducted in environmental chambers to evaluate different dietary modifications on the incidence or severity of ascites, leg disorders, and sudden death syndrome in males of tw o commercial broiler strains and their reciprocal crosses. A high energy-high nutrient density diet (HE) series served as the positive control. Two other diet series consisted of a high fiber (HF) diet fed 7 to 21 days of age, followed by the HE series, and a low energy-low nutrient density diet during the early growth phase, as suggested by a major breeder. All diets were pelleted. In one study, a low ventilation model was used while in the second study a low temperature model was used. However, due to limitations of the system we were unable to attain the desired low temperatures. In both studies, however, atmospheric levels of CO and 2 ammonia were greatly elevated. There were no differences in incidence or severity of ascites, leg disorders, or sudden death syndrome among broilers fed the different dietary regimes to 49 days of age. Broilers fed diets designed to reduce early growth rate were significantly lighter than those fed the HE diets at 21 days of age. At 49 days of age body weights were not always significantly different but quantitative weight differences were equal or greater than those observed at 21 days of age. It is possible that under environmental conditions more favorable to the development of ascites that dietary modification may prove beneficial. In these studies, however, live performance was reduced by the dietary modifications with no beneficial effects on reduction of ascites.

Effects of Dietary Energy Level and Number of Meals on Growth and Body Composition of Nile Tilapia Oreochromis niloticus (L.) During Summer and Winter Seasons

AbstractTwo feeding trials (experiments 1 and 2) were conducted to determine the combined effect of dietary energy levels (low energy, LE and high energy, HE) and number of daily meals (one meal with the entire daily amount, two meals with half of the daily amount, and three meals with one‐third of the daily amount) on the growth and body composition of Nile tilapia Oreochromis niloticus in a recirculating system at different water temperatures, representing winter and summer seasons. In experiment 1 (winter), weight gain and specific growth rate (SGR) were significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. Weight gain and SGR for fish fed the LE diet one daily meal were significantly (P &lt; 0.05) higher than for fish fed the HE diet in one daily meal. Feed efficiency ratio (FER) and energy efficiency ratio (EER) were significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. Protein efficiency ratio (PER) was not significantly (P &gt; 0.05) affected by either dietary energy levels or number of meals. However, protein retention was significantly (P &lt; 0.05) affected by both dietary energy levels and number of meals. The chemical composition (moisture, protein, lipid, and ash) of fish muscle was not significantly (P &gt; 0.05) affected by either dietary energy levels or number of meals. However, visceral fat content was significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. In experiment 2 (summer), weight gain and SGR were significantly (P &lt; 0.05) affected by number of meals, but not by dietary energy levels. Weight gain and SGR for fish fed the LE and HE diets in two daily meals were significantly (P &lt; 0.05) higher than those fed one daily meal. FER and PER were significantly (P &lt; 0.05) affected by number of meals, but not by dietary energy levels. The highest FER and PER were observed in fish fed two daily meals. EER was significantly (P &lt; 0.05) affected by both dietary energy levels and number of meals. Moisture and protein content of the whole fish were not significantly (P &gt; 0.05) affected by either dietary energy levels or number of meals. Lipid content was significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. Based on the results of these experiments, Nile tilapia should not be fed high‐energy diets to improve fish performance even under a limited feed allowance during winter or summer. Fish grew rapidly when fed two daily meals during summer, but number of meals had no effect on fish performance during winter.

Dysregulation of hypothalamic serotonin turnover in diet-induced obese rats

When outbred Sprague–Dawley rats are placed on a diet relatively high in fat and calories (HE diet), half develop diet-induced obesity (DIO), while the rest are diet-resistant (DR). When fed a low fat chow diet from weaning, DIO- and DR-prone rats weigh the same, but DIO-prone rats have a number of abnormalities of neural function, many of which are normalized when they become obese after chronic exposure to a HE diet. Because of its important role in the regulation of energy homeostasis in the hypothalamus, we examined the ratio of serotonin (5-HT) to its metabolite, 5-hydroxyindolacetic acid (5HIAA), as an index of transmitter turnover in micropunches from various brain areas in these rats. While still on chow, both DIO- and DR-prone rats showed lower 5-HT turnover in most brain areas sampled during the last hour of the light phase, when animals become active and begin foraging for food, as compared to the first hour of the light phase, when animals are generally quiescent and not eating. However, unlike DR-prone rats, DIO-prone rats did not show a significant time-dependent difference in 5-HT turnover in either the arcuate or paraventricular hypothalamic nuclei. When fasted for 48 h, both DIO- and DR-prone rats showed a generalized 16–46% decrease in 5-HT turnover in the dorsomedial nucleus, perifornical lateral hypothalamus, dentate gyrus and motor cortex as compared to their free-fed counterparts. However, fasted DIO-prone rats showed a 53% greater reduction in the ventromedial nucleus turnover than fasted DR-prone rats. Finally, when DIO rats became obese after 14 weeks on the HE diet, their abnormalities in hypothalamic 5-HT turnover at the end of the light phase were normalized. Thus, DIO-prone rats show abnormalities of diurnal and fasting-induced alterations in brain 5-HT turnover which may predispose them to become obese when dietary fat and caloric density are increased. Once obesity develops, these abnormalities, like those of several other hypothalamic transmitters and peptides, are normalized. This may contribute to the persistence of obesity once it develops.

Effect of dietary energy and protein on bovine follicular dynamics and embryo production in vitro: associations with the ovarian insulin-like growth factor system.

Heifers were assigned either low or high (HE) levels of energy intake and low or high concentrations of dietary crude protein. The effect of these diets on the plasma concentrations of insulin, insulin-like growth factor (IGF)-I, and urea on follicular growth and early embryo development is described. We propose that the observed dietary-induced changes in the ovarian IGF system increase bioavailability of intrafollicular IGF, thus increasing the sensitivity of follicles to FSH. These changes, in combination with increased peripheral concentrations of insulin and IGF-I in heifers offered the HE diet, contribute to the observed increase in growth rate of the dominant follicle. In contrast to follicular growth, increased nutrient supply decreased oocyte quality, due in part to increased plasma urea concentrations. Clearly a number of mechanisms are involved in mediating the effects of dietary energy and protein on ovarian function, and the formulation of diets designed to optimize cattle fertility must consider the divergent effects of nutrient supply on follicular growth and oocyte quality.

Effects of feeding frequency and dietary energy level on growth and body composition of juvenile flounder, Paralichthys olivaceus (Temminck &amp; Schlegel)

A two (dietary energy levels; low energy, LE and high energy, HE) × 4 (feeding frequency; one feeding in 2 days, one feeding daily, two times daily and three times daily) factorial experiment was performed to determine the effects of dietary energy level and/or feeding frequency on the growth and body composition of juvenile flounder Paralichthys olivaceus. The survival rate was not significantly different among treatments. Weight gain of fish fed the LE and HE diets significantly increased as feeding frequency increased. The weight gain of fish fed the LE diet was higher at each level of increasing feeding frequency. The weight gain of fish fed the HE diet was higher than that of fish fed the LE diet once in 2 days and once daily, but weight gain of fish fed the HE diet was lower than the LE diet three times daily. Daily feed intake was significantly influenced by feeding frequency, but not by dietary energy level. Feed efficiency of fish fed the HE diet once daily was significantly higher than that of fish fed the LE diet once in 2 days, but no significant difference in feed efficiency was observed among other groups of fish. The protein efficiency ratio of fish fed the LE diet once in 2 days was the lowest. Feeding frequency and dietary energy level had a significant effect on the body lipid content. A feeding frequency of two times or three times daily would be effective, depending on dietary energy level for maximum growth of juvenile flounder grown from 3.5 to 15 g.

Effect of feeding time on digestibility, growth performance and protein metabolism in the rainbow trout Oncorhynchus mykiss: interactions with dietary fat levels

The effect of feeding time was studied in rainbow trout fed different dietary levels of fat. Fish were fed either 1 h after light on in the morning or 1 h after light off in the evening with a low energy diet (LE, 6 % lipid) or a high energy diet (HE, 23 % lipid). Regardless of the diet, apparent digestibility and post-prandial protein synthesis were higher in fish fed in the morning than in those fed at the beginning of the night. In fish fed the LE diet in the morning, growth performance and nutrient retention efficiency tended to be higher than in those fed at the beginning of the night. In contrast, fish fed the HE diet in the morning had lower protein growth rate, protein content and protein retention efficiency than those fed in the evening. These results suggest that protein metabolism might be involved in the effect of feeding time on growth and that there is an interaction between the time of feeding and dietary level of fat on growth.

Arcuate NPY neurons and energy homeostasis in diet-induced obese and resistant rats.

The neuropeptide Y (NPY) neurons in the hypothalamic arcuate nucleus regulate and are regulated by short-term changes in energy homeostasis. Both outbred and inbred strains of rats that develop diet-induced obesity (DIO) or are diet resistant (DR) when fed a diet relatively high in energy, fat, and sucrose content (HE diet) were used to study arcuate NPY mRNA expression during long-term changes in energy balance. Outbred, chow-fed obesity-prone rats had 59% higher NPY levels than obesity-resistant rats. After 14 wk on HE diet, DIO rats had 17% lower NPY levels than DR rats made comparably obese on a highly palatable diet. When switched to chow, obese DR rats spontaneously reduced their intake and their body weights fell to control levels in association with a 10% decrease in NPY levels. DIO rats lost weight only with energy restriction associated with a 21% increase in their NPY levels. When again fed ad libitum, the weight and NPY levels in the rats returned to those of unrestricted DIO rats. Chow-fed, inbred DIO rats weigh more and are fatter than age-matched inbred DR rats. As with outbred DIO rats fed the HE diet, inbred DIO rats had 20% lower NPY levels than DR rats. Thus preobese, outbred DIO rats have high levels of NPY message that are not susceptible to metabolic regulation. When obesity develops in both inbred and outbred rats, the levels of NPY mRNA fall but become responsive to alterations in energy availability.

Defense of differing body weight set points in diet-induced obese and resistant rats.

Among outbred Sprague-Dawley rats, approximately one-half develop diet-induced obesity (DIO) and one-half are diet resistant (DR) on a diet relatively high in fat and energy content (HE diet). Here we examined the defense of body weight in these two phenotypes. After HE diet for 13 wk, followed by chow for 6 wk, DR rats gained weight comparably but their plasma leptin levels fell to 54% of chow-fed controls. When a palatable liquid diet (Ensure) was added for 13 wk, other DR rats became obese. But when switched to chow, their intakes fell by 60%, and body and retroperitoneal (RP) fat pad weights and plasma leptin and insulin levels all declined for 2 wk and then stabilized at control levels after 6 wk. In contrast, comparably obese DIO rats decreased their intake by only 20%, and their weights plateaued when they were switched to chow after 13 wk on HE diet. When a subgroup of these DIO rats was restricted to 60% of prior intake, their weights fell to chow-fed control levels over 2 wk. But their leptin and insulin levels both fell disproportionately to 30% of controls. When no longer restricted, their intake and feed efficiency rose immediately, and their body and RP pad weights and leptin and insulin levels rose to those of unrestricted DIO rats within 2 wk. Thus diet and genetic background interact to establish high (DIO) or low (DR) body weight set points, which are then defended against subsequent changes in diet composition and/or energy availability. If leptin affects energy homeostasis, it does so differentially in DIO vs. DR rats since comparably low and high levels were associated with differing patterns of weight change between the two phenotypes.