Restricted Food Availability Research Articles

Food-anticipatory activity and liver per1-luc activity in diabetic transgenic rats

The mammalian Per1 gene is an important component of the core cellular clock mechanism responsible for circadian rhythms. The rodent liver and other tissues rhythmically express Per1 in vitro but typically damp out within a few cycles. In the liver, the peak of this rhythm occurs in the late subjective night in an ad lib-fed rat, but will show a large phase advance in response to restricted availability of food during the day. The relationship between this shift in the liver clock and food-anticipatory activity (FAA), the circadian behavior entrained by daily feeding, is currently unknown. Insulin is released during feeding in mammals and could serve as an entraining signal to the liver. To test the role of insulin in the shift in liver Per1 expression and the generation of FAA, per-luciferase transgenic rats were made diabetic with a single injection of streptozotocine. Following 1 week of restricted feeding and locomotor activity monitoring, liver was collected for per-luc recording. In two separate experiments, FAA emerged and liver Per1 phase-shifted in response to daytime 8-h food restriction. The results rule out insulin as a necessary component of this system.

The development of intersucking in dairy calves around weaning

Intersucking, i.e. sub-adult or adult cattle sucking at the udder of herd-members, is a problem often reported in dairy herds that leads to udder health problems. The causes of intersucking are virtually unknown, and until now all available countermeasures treat only the symptoms of this behavioural problem. We examined (I) whether intersucking occurs prior to weaning and continues thereafter, and (II) whether its establishment is related to the feeding management during weaning. On 10 dairy farms, we observed the sucking and feeding behaviour of a group of dairy calves (2–5 animals per farm, 38 in total) 1 week before and 1, 5 and 9 weeks after weaning. Calves were weaned off milk at an average age of 21 weeks (S.D. 4.7). We analysed the calves’ food rations in order to estimate the adequacy of their energy density. Thirty-five (92%) of the 38 calves performed intersucking already before weaning, with the frequency being highly variable between individual calves ( x med=5.0 bouts/day, range 0–24.7). Calves with a high intersucking activity before weaning were likely to continue intersucking after weaning ( P<0.05). Before and after weaning intersucking could be observed at nearly every time of the day, but was most frequent around feeding. Calves with a long feeding duration ( x med=260 min, range 186–374) showed less frequent intersucking 1 week after weaning ( P<0.05). In addition, the frequency of intersucking increased with decreasing adequacy of their rations energy density ( r=−0.88, P<0.01), and the highest intersucking activity was recorded on farms with restricted availability of food. The results indicate that intersucking occurs already before weaning, and its establishment may be prevented by a ration and a feeding management that ensures an optimal transition from pre-ruminants to ruminants.

Is the copepod egg production in a highly turbid estuary (the Gironde, France) a function of the biochemical composition of seston?

The influence of the biochemical composition of particles originating from surface waters of the Gironde estuary on egg production rates of Eurytemora affinis zooplanktonic population was studied. In the high turbidity zone, suspended particulate matter had a low nutritional quality because the easily available organic fraction represented less than 15% of the overall particulate organic matter. In waters located seaward of the high turbidity zone, a slight increase in nutritional quality was observed. As a result, the sum of easily extractable organic macromolecules represented 15 to 33% of the overall particulate organic matter. The present study suggests that the low egg-production rate of Eurytemora affinis, occurring in the high turbidity zone, results from combined effects of temperature and bad feeding conditions in the area. Low copepod production can be explained by little phytoplankton growth due to light limitation and, therefore, restricted food availability, as well as difficulties in food selection, non-living particle may being dominant.

Circadian rhythms of blood pressure and heart rate in conscious rats: Effects of light cycle shift and timed feeding

The aim of the present study was to evaluate the impact of a shift in the light cycle and of restricted food availability on circadian rhythms of blood pressure, heart rate, and behavioral activity in freely moving rats by radiotelemetry. In rats that were fed ad lib, a shift of the light cycle by 6 h (from lights on 0700–1900 h to lights on 1300 to 0100 h) induced an immediate, but from then on gradual, shift of the circadian rhythms of blood pressure, heart rate, and behavioral activity, which took 4–5 days to fully synchronize with the new light cycle. Rats on a normal light cycle receiving feeding for 1 h only during the light period rather than ad lib feeding, showed a suppressed circadian rhythm, with the dark period values reduced to values not significantly different from those observed in the light period. In addition, during the timed feeding blood pressure, heart rate, and behavioral activity peaked to levels that were normally seen during the dark period. These data show that environmental factors such as timed feeding or changes in the light cycle have a marked influence on the circadian rhythms of blood pressure and heart rate.

Cocaine self-administration under conditions of restricted and unrestricted food access.

Four rhesus monkeys (Macaca mulatta), maintained at reduced body weight and restricted food availability, had access to a 0.8-mg/ml cocaine solution and vehicle under a concurrent fixed-ratio (FR) 8 schedule. Over days, the cocaine concentration was reduced (0.57, 0.4, 0.2, 0.1, 0.05, 0.025) and then returned, gradually over days, to 0.8 mg/ml. The ratio value was then varied (to 16, 32, 64, 128, and 8). Food access was unrestricted, and the ratio and the concentration manipulations were then repeated. During food restriction cocaine served as a reinforcer for all monkeys, whereas during free feeding cocaine functioned as a reinforcer for 3 of 4 monkeys; with these monkeys, the dose-response curve obtained under free feeding was shifted to the right of that obtained under food restriction. There were no differences in FR response curves obtained during food restriction and unrestricted feeding. These data suggest that food restriction increases cocaine's reinforcing effects and that the higher the cocaine dose, the greater are the reinforcing effects. A demand curve analysis was completed, and data are discussed in terms of microeconomic principles.

ON THE VERTICAL DISTRIBUTION OF LIVING (ROSE BENGAL STAINED) BENTHIC FORAMINIFERS IN THE ARCTIC OCEAN

The vertical distribution of living (Rose Bengal stained) benthic foraminifers was determined in the upper 15 cm of sediment cores taken along transects extending from the continental shelf of Spitsbergen through the Eurasian Basin of the Arctic Ocean. Cores taken by a multiple corer were raised from 50 stations with water depths between 94 and 4427 m, from areas with moderate primary production values to areas that are among the least productive ones in the world. We believe, that in the Arctic Ocean the vertical distribution of living foraminifers is determined by the restricted availability of food. Live foraminiferal faunas are dominated by potentially infaunal species or epifaunal species. Species confined to the infaunal microhabitat are absent in Arctic sediments that we examined, and predominantly infaunal living species are nowhere dominant. In general, an infaunal mode of life is restricted to the seasonally ice-free areas and thus to areas with at least moderate primary production during the summer period. Under the permanent ice cover living species are usually restricted to the top centimeter of the sediment surface, even though some are able to dwell deeper in the sediment under ice-free conditions.

The Effects of Photoperiod and Food Intake on Reproductive Development in Male Deer Mice ( Peromyscus maniculatus)

Seasonal breeding is a tactic that has evolved in rodents that limits reproduction to specific times of the year to increase reproductive success. In order to time breeding accurately, many animals respond to changes in daily photoperiod. Short day lengths inhibit breeding in many nontropical rodent species. Restricted food availability can also inhibit reproductive function among some individuals in these so-called “photoperiodic” populations. Rodents born at the end of the breeding season typically delay sexual maturation until the following spring. Prepubertal rodents exposed to day lengths that are <12 h light/day will not undergo puberty for 4–7 months in the laboratory. Food restriction can also affect the timing of puberty onset. Reproductive function of food-restricted juvenile mice may remain inhibited until food availability improves. Alternatively, reproductive function of food-restricted juvenile mice might eventually develop despite restricted food intake. This study examined the effects of chronic food restriction and photoperiod on reproductive development in male deer mice ( Peromyscus maniculatus bairdii). Short-day mice fed ad lib delayed gonadal development for 5–7 months, but eventually achieved reproductive maturity. The reproductive function of short-day mice fed ad lib was indistinguishable from long-day control animals when assessed at week 32. Long-day food-restricted mice exhibited an intermediate level of gonadal development and function. Short-day food-restricted deer mice also inhibited reproductive growth, but failed to demonstrate reproductive maturity by week 32 of the study. Taken together, these results suggest that retardation of reproductive development by food restriction is only superficially similar to the delay in reproductive maturation imposed by short day exposure. It does not appear that male deer mice escape from the inhibitory effects of food restriction to attain sexual development.

Effects of serotonergic agents on food-restriction-induced hyperactivity

Rats that are fed for 90 min per day can stabilize their weight after an initial drop; however, if rats on this feeding schedule are also given access to a running wheel, they run excessively, eat less, lose weight, and often die. To investigate this phenomenon as a possible animal model of obsessive-compulsive disorder (OCD), rats were treated for 5 weeks with fluoxetine, an antidepressant that relieves OCD symptoms in humans (5 mg/kg, 2.5 mg/kg), or imipramine, an antidepressant that does not affect OCD symptoms (5 mg/kg), or saline prior to exposure to food restriction and the running wheel. In addition, because chronic fluoxetine treatment is thought to enhance serotonergic neurotransmission, for contrast an additional group of rats were treated with parachlorophenylalanine (PCPA), a tryptophan hydroxylase inhibitor that depletes serotonin. Rats treated with fluoxetine lost significantly less weight, ran significantly less, and increased food intake more rapidly during restriction of food availability than saline-treated rats. Rats treated with imipramine did not differ from those treated with saline on these parameters. Compared to saline-treated rats, rats treated with PCPA lost more weight, ate less food, and increased running more rapidly. These effects of pharmacological treatment indicate an inverse relationhip between central serotonergic activity and vulnerability to develop food-restriction-induced anorexia and compulsive running. In addition, like OCD in humans, this phenomenon in rats seems to be blocked by chronic treatment with a serotonin selective reuptake inhibitor but not a less selective monoamine reuptake inhibitor.

Manipulating melatonin in red deer (Cervus elaphus): Differences in the response to food restriction and lactation on the timing of the breeding season and prolactin‐dependent pelage changes

In this study, we investigated the influence of food availability and lactation upon seasonality in red deer. This was examined by testing the hypothesis that advancing the timing of breeding and autumn moult using the hormone melatonin will be prevented when the food availability of lactating hinds is severely restricted. This hypothesis was rejected. Implanting 1 g of melatonin between June 22 and November 30 resulted in advances in the timing of the onset of ovarian activity and winter coat growth of 18 and 35 days, respectively. Whilst the onset of ovarian activity was unaffected by lactation and restricted food availability, these factors significantly delayed the winter coat growth by 20 days. The date of onset of winter primary fibre growth was negatively correlated to plasma concentrations of the hormone prolactin in July. We suggest that seasonal changes in the growth of primary hair fibres are modified by two mechanisms: the increasing duration of melatonin secretion, as day lengths decline, which depresses prolactin secretion, and low nutrition, which elevates prolactin secretion in lactating deer. To conclude, we have demonstrated that the sensitivity of red deer to photoperiodic influences is preserved in lactating animals at low levels of nutrition, and that the timing of the onset of the breeding season and winter coat growth differ detectably in their sensitivity to nutrition and lactation.

Fetal alcohol and thymocyte phenotypes in offspring: response to food deprivation.

Restriction of food availability is a reliable stimulus that leads to significant hypothalamo-pituitary-adrenal (HPA) activation to which rats do not habituate. Based on our previous data that indicated that the HPA response to some, but not all, stressful stimuli is significantly greater in adult offspring of Sprague-Dawley dams exposed to 35% alcohol during the last 2 weeks of gestation than that of control rats and on the mounting neuroendocrine-immune literature that describes the role of pituitary-adrenal products in modulating cellular immunity, we hypothesized that the outcomes of food restriction would be significantly more marked in fetal alcohol-exposed (FAE) offspring, compared with control rats. Data we report herein show that--whereas food restriction at 30-35 days of age produced significant changes in body weight, thymus weight-to-body weight ratio, adrenal weight-to-body weight ratio, plasma corticosterone levels, and in thymocyte number, as well as in the percentage and absolute number of CD4+ and CD8+ thymocytes that express CD45RC-FAE and control rats were equally affected. We conclude that food restriction is another example of a stressful stimulus that fails to distinguish satisfactorily between FAE and control rats of prepubertal age.

The Effect of Food Availability on Time and Energy Expenditures of Territorial and Non-Territorial Hummingbirds

We studied the time and energy allocations related to territorial behavior in male Blue-throated Hummingbirds (Lampornis clemenciae; about 8.3 g) under conditions of unlimited and restricted food availability. When food was unlimited. territorial males avoided inter-specific aggression, chasing only 11% of the inter-specific’intruders (Blackchinned Hummingbirds, Archilochus alexandri; about 3.5 g). Thus, when food was unlimited, inter-specific intruders were able to forage efficiently, meeting their estimated daily energy requirement with ease (27 Id/day). Conversely, 8 1% of intraspecific intruders were chased, and intra-specific intruders were able to feed at territorial feeders only when the territorial male was away. Chases of intra-specific intruders were longer and appeared to be more intense than chases of inter-specific intruders. When food was restricted territorial activity, including the total number of chases engaged in by the territory owner, was significantly reduced, although the basic characteristics of territorial behavior (e.g., chases and displays) did not change. Territory owners chased a higher proportion of inter-specific intruders when food was restricted (48%), suggesting an increase in inter-specific competition. A high proportion of intra-specific competitors continued to be chased (80%), although the total number of intra-specific intruders was lower. We believe that variations in the cost of territoriality are dependent primarily on the level of intra-specific competition. This is supported by the fact that when food was restricted to an amount that could support a maximum of 1.4 L. clemenciae(based on doubly labeled water measurements offield metabolic rate in a previous study), energy intake by the territory owner decreased from 114 kJ/day to 64 Id/day, with the primary difference being number of intra-specific chases. These data also suggest hat the exclusion of other hummingbird species might be based strictly on the amount of available food (energy). When food is restricted, inter-specific competition is more costly to the territory owner causing the exclusion of a higher proportion of inter-specific intruders. The high proportion of intra-specific intruders that are chased in either experimental condition suggests that territorial behavior in L. clemenciae might have functions other than resource protection per se, such as social functions related to their mating system.

Hoarding behavior in the pigeon (Columbia livia): performance under the restriction of food availability

The effect of restriction of food availability on food-earning behavior was investigated in two pigeons ( Columbia livia) in a closed economy paradigm. Experimental chambers that allowed them to store food were devised. They were exposed to two kinds of feeding conditions. One condition was a free-feeding condition in which the bird could earn food at any time of the day by pecking a key. The other was a restricted-feeding condition where the food availability was restricted only for a given time of day. Consequently, one bird overtly hoarded food. After the bird was exposed to the restricted-feeding condition, this bird learned to obtain extra food and left some food uneaten for later consumption. Moreover, this bird utilized the hoarded food and compensated for the reduction of the income. Thus, after an experience with the restriction of food availability, the bird learned to obtain extra food that was not consumed immediately and left it uneaten.However, in the condition where essential food but not extra food could be earned, the bird did not hoard food.

How do population density and food supply influence social behaviour in the snowshoe hare (Lepus americanus)?

The influence of population density and food on the social behaviour of the snowshoe hare (Lepus americanus) was studied in an outdoor enclosure. The year was divided into two periods: the nonbreeding season (October to March) and the breeding season (April to August). During each period, data on social interactions were recorded for groups of 4, 6, 8, and 10 animals, with three different sets of animals for each group size. Agonistic behaviour characterized social encounters between hares year-round. During the nonbreeding season, there was a significant correlation between agonistic behaviour and group size for females only. During the breeding season, the rate of interaction was lower and agonistic behaviour was significantly and negatively correlated with group size for males only. Two-way ANOVA of total agonistic behaviour revealed that group size and sex interacted significantly only during the nonbreeding season. The different categories of agonistic behaviour (aggression, threat, and taking the place of another animal) were also analysed separately. The distribution of aggression within each of the experimental groups indicated that the two top-ranking animals were generally males and that they initiated most of the aggressive encounters. Another experiment with restricted food availability was conducted to study the impact of limited resources on agonistic behaviour. Hares were significantly more aggressive when food was restricted than when food was available ad libitum. It thus appears that food availability has a stronger influence on social behaviour than does hare density.

Nonphotic entrainment of circadian activity rhythms in suprachiasmatic nuclei-ablated hamsters.

This study examined the role of the suprachiasmatic nuclei (SCN) in nonphotic entrainment. The wheel-running activity of SCN-ablated hamsters was recorded in constant dark (DD) and then under prolonged schedules of 2-hr daily cage changes, restricted food availability, and daily light-dark (LD) cycles. Some hamsters with very large lesions subsuming the SCN and surrounding areas exhibited significant, albeit unstable, circadian activity rhythms in DD. Some hamsters with similar ablations also showed entrained rhythms to daily cage change schedules. All hamsters showed robust rhythms entrained to a daily feeding schedule, but no hamsters showed entrainment to LD cycles. Competent circadian oscillators evidently exist outside the SCN, at least 0.5 mm or more away, and at least some are nonphotically entrainable. Weaker entrainment in animals with larger lesions suggests that nonphotically entrainable oscillators also exist within the SCN or its immediate vicinity.

Effects of aging on food-entrained circadian rhythms in the rat

Twenty-four hour schedules of restricted food availability entrain a component of the circadian activity rhythm in rats via a food-entrainable pacemaker separate from the light-entrainable pacemaker. The effect of aging on food-entrained circadian rhythms was examined in 6 rats maintained on a restricted diurnal feeding schedule from age 3–21 months and again from 24–25 months. Food-entrainment, measured as behavioral anticipation of a 1-hr daily mealtime during the middle of the light period and persistence of this anticipation rhythm during food deprivation, was apparent in the aged rats when recorded in wheel-running cages from 20–21 months of age. Despite the long duration of restricted diurnal food access, the aged rats, like young rats, rapidly reverted to nocturnal activity when transferred to ad lib feeding. When restricted diurnal feeding was reinstated at 24 months age, these rats, now recorded in food-bin monitoring cages, required more time for a food anticipation pattern to emerge and showed a lower amplitude food anticipation rhythm compared to a group of young adult rats. These age-related changes are similar to those that characterize photically entrained circadian rhythms and suggest that both components of the rat's multioscillatory circadian timekeeping system deteriorate in parallel over the life span.

Metabolism and Food Availability as Regulators of Production in Juvenile Cotton Rats

Recent studies have shown positive relationships between mass—specific rates of basal metabolism (BMR) and production rates for interspecific comparisons of mammals. This study investigated associations between BMR and production rates by determining whether simultaneous increases in BMR and production occur at the individual level. Growth, reproductive development, and food—processing rates of juvenile Sigmodon hispidus with naturally occurring or experimentally elevated levels of BMR and with ad libitum or restricted food availability were compared. When food was readily available, elevated BMR was associated with higher ingestion rates, faster and more efficient growth, and earlier sexual development. When food was restrived, elevated BMR was associated with severely reduced mass gains. These results suggest that basal metabolism, either directly or indirectly, contributes to mammalian rates of production.

Regulation of feeding behaviour in monosodium glutamate (MSG) treated mice

Regulation of food intake was studied in mice treated neonatally with MSG. A diurnal pattern of food intake with a significantly greater nocturnal intake was observed. In response to restricted food availability (4 hours/day). MSG mice increased intake progressively although less efficiently than control mice. The opioid kappa receptor agonist ketocyclazocine enhanced food intake. It is concluded that in MSG treated mice opioid kappa receptor mechanisms involved with regulation of food intake are basically intact.

Time of birth and daily activity mediated by feeding rhythms in the pregnant rat.

The temporal relationship between time of birth and daily physical activity has been studied in rats submitted to different feeding rhythms. Animals, put under 14 h of light and 10 h of darkness (lights on from 6 to 20 h), were isolated at mating (day 1 of gestation) and assigned from day 8 to one of five groups. Group C was fed ad libitum, and groups 2PF, 9PF, 14PF and 21PF had food available for three hours per day from 2, 9, 14 and 21 h, respectively. In groups 9PF and 14PF, births were clustered in one single period during the night between days 22 and 23 of gestation. In groups C, 2PF and 21PF, births were distributed into two periods, during the afternoon of day 22 before darkness and after dawn of day 23. The birth rates of these groups were 55.3, 74.2 and 27.6%, respectively, on day 22 and 44.7, 25.8 and 72.4% on day 23. No births occurred during the times that food was available; they were noted in all groups at times when the animals were least active according to records kept throughout gestation. Thus, restricting food availability to periods of normal inactivity (groups 9PF and 14PF vs group C) led to a major shift in the time of delivery as well as to a distortion of the normal activity patterns. These results confirm that feeding rhythms are potent entrainers of birth time in rats and that they interact with the light regime. Pregnant rats seem to be organized so that birth either precedes the main daily physical activity or follows it, depending upon the environmental conditions.

Energy Allocation during Lactation in Cotton Rats (Sigmodon hispidus) on a Restricted Diet

The effects of restricted food availability on lactating Sigmodon hispidus from Kansas (KSh) and Tennessee (TSh) populations were studied in the laboratory. Mothers received 75% of food intake required by nonreproductive females of similar body mass. KSh control and restricted females produced significantly larger litter sizes at birth (6.9 and 7.3) than TSh females (4.7 and 5.0). At weaning (12d), mean litter size of restricted KSh females (4.3) was similar to that of control (4.4) and restricted TSh females (4.5). Mean litter size for control KSh females (6.6) was significantly larger than for the other three groups. KSh females of smaller body mass suffered higher offspring mortality during lactation than did larger KSh females. Mean body mass of control KSh young (20.1 g) was significantly larger than of control TSh young (16.5 g) at age 12 d. Mean body masses of restricted KSh and TSh young (12.5 and 11.2 g) were not significantly different at 12 d of age, and young of both groups were smaller than controls. Smaller restricted KSh females produced young that grew more slowly than those of larger restricted KSh females. Variation in the growth of restricted TSh young, however, was dependent upon litter size, as was growth for both TSh and ksh controls. During lactation, restricted TSh and KSh females lost an average of 31% of parturition body mass; comparable values for control TSh and KSh were 13% (16 g) and 9% (17 g), respectively. In the nest, body temperature of young of restricted KSh and TSh females averaged °1°—2°C lower than body temperatures of control young. Development of the ability of pups to respond metabolically to cold, however, did not differ significantly between control and restriction treatments or between populations. Thus, under severe food restriction, females with larger litter size (KSh) lost young until litter sizes were similar to those for females with smaller original litters (TSh). Decreased growth and body temperatures of nestlings in food—restricted groups reduced the energy demands of lactation so that smaller litters could survive to weaning. Growth and survivorship of KSh young were largely determined by the body mass of the dam, indicating the potentially significant role of body size for small mammals that experienced periodic food shortages during lactation.

Melatonin and corticosterone regulation: Feeding time or the light:Dark cycle?

Under ad libitum feeding, male rats exhibit a marked rhythm of plasma and pineal melatonin; levels are low during the day and high at night. Restricting food availability to a 2 hour period during the light or dark does not markedly influence the melatonin rhythm, both groups having a crest in circulating melatonin during the dark. In contrast, plasma corticosterone levels are influenced by both the light-dark cycle and feeding. Animals fed early in the light period exhibit a biomodal corticosterone secretory pattern, with high steroid levels immediately prior to feeding and again just before lights-out, animals fed early in the dark have a single crest, just before food presentation. These data provide evidence for the dissociation of melatonin and corticosterone secretory patterns, providing support for the hypothesis that multiple regulators control neuroendocrine rhythmicity.