Influence of level of nutrition during late pregnancy on reproductive productivity of red deer (2) Adult hinds gestating wapitixred deer crossbred calves

The present study aimed to relate feed intake of red deer hinds in the later stages of gestating wapitixred deer crossbred foetuses on dam body condition, gestation length, birth weight and calf growth. Multiparous hinds (N=18) conceiving at known dates to either wapiti (n=12) or red deer (n=6) sires were housed in individual pens from days 150-220 of pregnancy, during which time they were offered either ad libitum access to pelletised rations (n=6 crossbred-bearing hinds [HH] and n=6 red deer-bearing hinds [RH]) or a restricted offer (n=6 crossbred-bearing hinds [HL]) set at 70% of the average ad libitum intake of HH hind in the previous week. Hinds were returned to pasture at day 220 and calving was closely monitored. Liveweights, body condition score (BCS), and lactation score (LS) of hinds were recorded weekly from day 130 of pregnancy until calves were weaned at 12 weeks of age. Calves were tagged and weighed at birth, and subsequently weighed at 7 and 12 weeks of age. HH and RH hinds exhibited similar patterns and levels of MEI/kg0.75, which peaked at 7.8 MJME/kg0.75 at day 220. HL hinds peaked at approximately 5 MJME/kg0.75 and showed significantly lower rates of liveweight gain during pregnancy. Interestingly, both crossbred-bearing groups initiated mammary development in advance of the RH hinds. While there were significant effects of foetal genotype on mean gestation length (239 days versus 234 days for crossbred versus red deer) and mean birth weight (14.5 kg versus 10 kg), the nutritional contrast for gestation length of crossbred-bearing hinds (i.e. HH versus HL) was not significant but approached significance for birth weight (14.5 kg versus 11.9 kg; P=0.06). Regression analysis revealed weak relationships between changes in hind liveweight and gestation length (P>0.05) but a significant relationship with birth weight (P<0.05). However, change in hind BCS was significantly related to both gestation length and birth weight. Crossbred calves reared by HH hinds were 30% heavier at 7 and 12 weeks of age than the red deer calves. However, those reared by HL hinds were significantly lighter than their genotype contemporaries and only marginally heavier than the red deer calves. These results generally contrast with the previous studies on red deer hinds gestating red deer foetuses [Asher, G.W., Mulley, R.C., O'Neill, K.T., Scott, I.C., Jopson, N.B., Littlejohn, R. 2004. Influence of level of nutrition during late pregnancy on reproductive productivity of red deer, (1) Adult and primiparous hinds gestating red deer calves. Anim. Reprod. Sci., in press] and indicate that the genetically determined higher growth requirements of crossbred foetuses may override any mechanism of compensatory control of gestation length at the expense of calf birth weight. Furthermore, there were marked carryover effects of late gestational feeding on crossbred calf growth and their dam's BCS that highlight the high nutritional demands of lactation.     

Effects of meal timing on tumor progression in mice

Meal timing can reset circadian clocks in peripheral tissues. We investigated the effects of such non-photic entrainment on tumor growth rate. Two experiments involved a total of 61 male B6D2F(1) mice synchronized with an alternation of 12 h of light (L) and 12 h of darkness (D) (LD12:12). Mice were randomly allocated to have access to food ad libitum, or restricted to 4 or 6 h during L or D. Rest-activity and body temperature, two circadian outputs, were monitored with an intra-peritoneal sensor. Glasgow osteosarcoma was inoculated into both flanks of each mouse ten days after meal timing onset. Before tumor inoculation, meal timing during D amplified the 24-h rhythms in rest-activity and body temperature with minimal phase alteration as compared to ad libitum feeding. Conversely, meal timing during L induced dominant 12-h or 8-h rhythmic components in activity, nearly doubled the 24-h amplitude of body temperature and shifted its acrophase (time of maximum) from approximately mid-D to approximately mid-L. Thirteen days after tumor inoculation, mean tumor weight (+/- SEM, mg) was 1503 +/- 150 in ad libitum mice, 1077 +/- 157 in mice fed during D and 577 +/- 139 in mice fed during L (ANOVA, p < 0.0001). Overall survival was prolonged in the mice fed during L (median, 17.5 days, d) as compared with those fed during D (14.5 d) or ad libitum (14 d) (Log Rank, p = 0.0035). The internal desynchronization produced by meal timing during L slowed down tumor progression, an effect possibly resulting from improved host-mediated tumor control and/or altered tumor circadian clocks.     

The effect of feeding frequency on utilization of algal nutrients by the marine herbivore, the luderick, Girella tricuspidata (Quoy and Gaimard)

Utilization of whole algae, lipid, protein and total nitrogen and total carbon by the luderick, Girella tricuspidata , fed ad libitum were found to be comparable with published results obtained for other species. Periods of food deprivation were found to cause reduced efficiency of utilization for all nutrients measured, with a 4–day deprivation period having a greater effect than a 24–h deprivation period.
Only animals fed ad libitum were able to obtain a greater amount of lipid from their food than was defaecated. Utilization of protein and non–protein nitrogen is similar in fish fed ad libitum , but a greater reliance upon the non–protein nitrogen content of the food for nutrition is apparent when the fish are subjected to periods of food deprivation. Nitrogen utilization, relative to other nutrients, by fish subjected to periods of food deprivation is greatest immediately after a feeding bout. Total carbon utilization relative to other nutrients increases with increasing time of deprivation following a feeding bout.
It is suggested that these changes in nutrient utilization with time after feeding are the result of rapid utilization of the nitrogen–rich cell contents, followed later by utilization of the algal cell wall.     

Meal-feeding studies in mice: effects of diet on blood lipids and energy expenditure

To identify optimal study-design conditions to investigate lipid metabolism, male, C57BL/6J mice (age, 59 +/- 3 days) were allotted to eight groups, with six animals per group that were stratified by three factors: diet type (high fat [HF]: 60% of energy from fat versus that of a standard rodent diet, 14% fat, fed for 7 weeks), feeding regimen (ad libitum [ad lib] versus meal fed), and metabolic state (data collected in fasted or fed states). Serum free fatty acids (FFA) and triacylglycerols (TAG) concentrations, and energy expenditure (EE) were assessed. Mice gained 0.30 +/- 0.11 g of body weight/day when allowed ad lib access to HF diet, similar weight when meal-fed the HF or ad lib-fed the standard diet (0.10 +/- 0.03 g/day), and no weight when meal-fed the standard diet (0.01 +/- 0.02 g/day). Fed-state TAG concentration was 88 to 100% higher (P < 0.02) than that of the fasted state, except when animals were ad lib-fed the HF diet. When the standard diet was meal fed, FFA concentration was 30% higher in the fasted compared with the fed state (P = 0.003). Mice had 33% higher postprandial EE when either diet was meal fed (P = 0.01). Mice adapted to meal feeding developed transitions in metabolism consistent with known physiologic changes that occur from fasting to feeding. When fed the standard diet, a 6-h per day meal-feeding regimen was restrictive for normal growth. These data support use of a meal-feeding regimen when HF diets are used and research is focused on metabolic differences between fasted and fed states. This protocol allows study of the metabolic effects of an HF diet without the confounding effects of over-consumption of food and excess body weight gain.     

Development of body condition in hinds of Iberian red deer during gestation and its effects on calf birth weight and milk production

Reproductive effort affects body reserves and subsequent ability to reproduce. In fact, the energy costs of gestation and lactation in hinds of red deer have a marked effect on maternal condition. The objectives of this study were to examine the development of hind monthly body condition during gestation in relation to reproductive rest, age and age class, just as its effects on total milk yield and calf birth weight. Eighty hinds of Iberian red deer were used as subjects during 2 years of study. They had ad libitum access to food and water. Animals were weighed weekly, and body condition was individually assessed. Milking was carried out under anesthesia with a milking machine followed by hand milking to collect the remaining milk.Age and reproductive rest influenced body condition, improving with age (coefficient: 0.10+/-0.01; P<0.001) and reproductive rest (mean+/-SEM, 3.75+/-0.05 vs. 3.25+/-0.02, with and without rest respectively; P<0.001). Hind age correlated positively with her body condition (R=0.62, P<0.001), however, when age class was included in the model, age was not significant. The greater the age class (up to age class 4) the greater the body condition; however, hinds of age class 5 had a lower body condition, but no significant differences were observed. Development of the body condition during gestation was different to age class 1 with respect to the others, just as between hinds that rested the preceding year and those that did not.     

Alternative Feeding Strategies and Potential Disease Transmission in Wisconsin White-Tailed Deer

ABSTRACT We conducted experimental feeding using 3 feeding methods (pile, spread, trough) and 2 quantities (rationed, ad libitum) of shelled corn to compare deer activity and behavior with control sites and evaluate potential direct and indirect transmission of infectious disease in white-tailed deer (Odocoileus virginianus) in central Wisconsin, USA. Deer use was higher at 2 of the feeding sites than at natural feeding areas (P ≤ 0.02). Deer spent a higher proportion of time (P < 0.01) feeding at pile (49%) and spread (61%) treatments than at natural feeding areas (36%). We found higher deer use for rationed than ad libitum feeding quantities and feeding intensity was greatest at rationed piles and lowest at ad libitum spreads. We also observed closer pairwise distances (≤0.3 m) among deer when corn was provided in a trough relative to spread (P=0.03). Supplemental feeding poses risks for both direct and indirect disease transmission due to higher deer concentration and more intensive use relative to control areas. Concentrated feeding and contact among deer at feeding sites can also increase risk for disease transmission. Our results indicated that restrictions on feeding quantity would not mitigate the potential for disease transmission. None of the feeding strategies we evaluated substantially reduced the potential risk for disease transmission and banning supplemental feeding to reduce transmission is warranted.     

Isolating neural correlates of the pacemaker for food anticipation

Mice fed a single daily meal at intervals within the circadian range exhibit food anticipatory activity. Previous investigations strongly suggest that this behaviour is regulated by a circadian pacemaker entrained to the timing of fasting/refeeding. The neural correlate(s) of this pacemaker, the food entrainable oscillator (FEO), whether found in a neural network or a single locus, remain unknown. This study used a canonical property of circadian pacemakers, the ability to continue oscillating after removal of the entraining stimulus, to isolate activation within the neural correlates of food entrainable oscillator from all other mechanisms driving food anticipatory activity. It was hypothesized that continued anticipatory activation of central nuclei, after restricted feeding and a return to ad libitum feeding, would elucidate a neural representation of the signaling circuits responsible for the timekeeping component of the food entrainable oscillator. Animals were entrained to a temporally constrained meal then placed back on ad libitum feeding for several days until food anticipatory activity was abolished. Activation of nuclei throughout the brain was quantified using stereological analysis of c-FOS expressing cells and compared against both ad libitum fed and food entrained controls. Several hypothalamic and brainstem nuclei remained activated at the previous time of food anticipation, implicating them in the timekeeping mechanism necessary to track previous meal presentation. This study also provides a proof of concept for an experimental paradigm useful to further investigate the anatomical and molecular substrates of the FEO.     

Mating behavior is controlled by acute changes in metabolic fuels

Mild food restriction for 48 h inhibits mating behavior in female musk shrews (Suncus murinus). However, mating behavior is restored after a 90-min feeding bout. In this series of experiments, we examined the role of metabolic fuels in this behavioral restoration. First, drugs reported to block glycolysis or fatty acid oxidation were given 2 h before mating. Both treatments inhibited mating in food-restricted females that were refed after treatment. Blood glucose levels were assessed in females that were fed ad libitum, food restricted, or food restricted and refed for 90 min. Food restriction significantly lowered blood glucose compared with ad libitum feeding or food restriction in combination with 90 min of refeeding. However, neither glucose nor fat alone could substitute for food and promote mating behavior in food-restricted females. In addition, analysis of ketone bodies and body composition in females demonstrated low or undetectable levels of these energy substrates. Our data suggest that musk shrews have relatively little stored energy. Therefore, female musk shrews rely on continuous food intake and monitor multiple cues acutely, including glucose availability and fatty acid oxidation. This ensures that mating does not occur when adequate energy is unavailable.     

Influence of rest and exercise at a simulated altitude of 4,000 m on appetite, energy intake, and plasma concentrations of acylated ghrelin and peptide YY

The reason for high altitude anorexia is unclear but could involve alterations in the appetite hormones ghrelin and peptide YY (PYY). This study examined the effect of resting and exercising in hypoxia (12.7% O(2); ～4,000 m) on appetite, energy intake, and plasma concentrations of acylated ghrelin and PYY. Ten healthy males completed four, 7-h trials in an environmental chamber in a random order. The four trials were control-normoxia, control-hypoxia, exercise-normoxia, and exercise-hypoxia. During exercise trials, participants ran for 60 min at 70% of altitude-specific maximal oxygen consumption (Vo(2max)) and then rested. Participants rested throughout control trials. A standardized meal was consumed at 2 h and an ad libitum buffet meal at 5.5 h. Area under the curve values for hunger (assessed using visual analog scales) tended to be lower during hypoxic trials than normoxic trials (repeated-measures ANOVA, P = 0.07). Ad libitum energy intake was lower (P = 0.001) in hypoxia (5,291 ± 2,189 kJ) than normoxia (7,718 ± 2,356 kJ; means ± SD). Mean plasma acylated ghrelin concentrations were lower in hypoxia than normoxia (82 ± 66 vs. 100 ± 69 pg/ml; P = 0.005) while PYY concentrations tended to be higher in normoxia (32 ± 4 vs. 30 ± 3 pmol/l; P = 0.059). Exercise suppressed hunger and acylated ghrelin and increased PYY but did not influence ad libitum energy intake. These findings confirm that hypoxia suppresses hunger and food intake. Further research is required to determine if decreased concentrations of acylated ghrelin orchestrate this suppression.     

Multiple exposure to activity anorexia in rats: effects on eating,weight loss,and wheel running

Animals were given five cycles of an activity anorexia (AA) procedure in order to determine the effect of additional experience on eating, running, and weight loss. Female Sprague-Dawley rats were given a 1h meal and allowed access to a running wheel for the remainder of each day. Upon reaching 75% of free-feeding body weight, each animal was denied wheel access and given ad libitum food until it regained the lost weight. Then, food was again restricted and wheel access provided. Sedentary control animals were placed on the restricted feeding schedule for the median number of days experimental animals required to reach weight loss criterion. Experimental animals showed adaptation by increasing food consumption and decreasing the rate of weight loss despite an increase in running across cycles. Additionally, the distribution of running shifted gradually so that during the later cycles, much of the running occurred in the hours just before feeding. The results support the hypothesis that running interferes with adaptation to the restricted feeding schedule and also that the marked increase in anticipatory behavior during the later cycles is primarily responsible for the maintenance of AA.     

Melatonin can induce year-round ovarian cyclicity in red deer (Cervus elaphus)

From 17 February 1987 (Day 1) to 5 June 1988 (Day 475), 6 red deer hinds which had been in natural daylength (NL/M) and 6 hinds which had been in continuous artificial light for the previous month (CL/M) were each given melatonin (5 mg in feed) daily at 15:00 h. Six controls (C) received unsupplemented feed. From Day 1 all hinds were in natural daylight and ovarian cyclicity was assessed from plasma progesterone concentrations. Group C first went into anoestrus on 15 March 1987 (Day 27 +/- 9.2 (s.e.m], recommenced cyclicity on 23 October (Day 249 +/- 2.3) and went into anoestrus again on 2 April 1988 (Day 411 +/- 8.7). Group CL/M first went into anoestrus 31 days earlier (P less than 0.05) on 12 February (Day -4 +/- 7.8), before the start of melatonin treatment; 4 hinds then recommenced ovarian cycles 132 days earlier (P less than 0.001) on 13 June (Day 117 +/- 5.8) and continued to cycle for a longer period than did controls. Group NL/M hinds were cyclic at the start of melatonin feeding and continued to cycle for 1 year or more (N = 6). Plasma prolactin concentrations remained suppressed (less than 20 ng/ml) for the duration of melatonin-feeding (Groups CL/M and NL/M) whereas control values (Group C) were elevated (20-120 ng/ml) between April and August (P less than 0.05). The ovarian response by hinds to melatonin therefore depends on initial reproductive status and recent photoperiodic history, and continued administration to cyclic hinds stimulates prolonged ovarian cyclicity irrespective of the time of year.     

The effect of deprivation on the microstructure of feeding by the Tobacco hornworm caterpillar

An automated device was used to examine, in detail, feeding on disks of wheat germ medium by fifth-instar Manduca sextacaterpillars. Comparisons were made between some animals which had ad libitum access to food at all times and others which were deprived of food for 1–5 h before being tested. Feeding patterns of both groups indicated regulation of feeding both between and within meals. Deprived animals ate more during their first meal than did nondeprived animals chiefly by increasing (a) the number of chewing bouts (and thus the meal duration) and (b) the bite frequency. Calculations indicated that the deficit caused by deprivation was made up during the first meal. However, deprived animals continued to eat more than nondeprived ones in subsequent feeding also. Passage of food through the gut was examined by dissecting out the contents of each region of the gut at various times after a colored test meal. Food passed through the foregut directly into the anterior part of the midgut. It stayed in the middle third of the midgut longer than in the anterior and posterior thirds, and the first pellet resulting from the test meal appeared 4 h after the meal. The following mechanisms of feeding regulation are proposed: (a) volumetric feedback mediated by stretch receptors of the foregut and anterior third of the midgut which terminates meals; (b) the development and subsequent reduction of satietyspecific behaviors mediated either by stretch receptors or by some other means which, e.g., allow the next meal to begin; and (c) metabolites whose levels drop during deprivation, triggering a series of events which lead to the excess feeding observed.     

Effect of food synchronization on the circadian rhythm of bone marrow and thymus lipids in rats

Young male Wistar rats reared under standard laboratory conditions with a 12:12 h light:dark regimen were fed ad libitum or were allowed access to food for only 2 h in the first half of the light or the dark part of the day. In rats fed ad libitum, marked circadian oscillation of the bone marrow triacylglycerol and phospholipid concentration and oscillation of the same fractions in the thymus were found. The restricted feeding time raised the triacylglycerol concentration in the bone marrow, but did not noticeably affect the time course of the circadian curves. The mean lipid values in the thymus of animals with a shortened feeding time did not alter, but the acrophase of the two basic fractions shifted.     

Circadian rhythms in honeybees: entrainment by feeding cycles

ABSTRACT. Colonies of the South African honeybee race Apis mellifera capensis (Escholtz) were maintained under constant conditions of illumination (200 lux), temperature (25±lC) and relative humidity (65±3%). Activity was measured at the hive entrance. After ad libitum feeding for at least 5 days, food was presented for only 2 h/day either for 1 week (series 1) or for 2 weeks (series 2). In the last part of each experiment, food was again available all the time. Colonies which showed free-running circadian activity rhythms (with periods ranging from 22.6 to 24.8 h) during ad libitum feeding were submitted to feeding cycles with inter-feeding intervals (T) of 22, 23, 24 and 25 h. In most of these experiments the rhythms were synchronized by the feeding schedule, resulting in a stable phase-angle difference between onset of activity and onset of food availability. The duration of this anticipatory activity was positively correlated with T. When ad libitum feeding was resumed, the period of the rhythm induced by the feeding schedule persisted for a few days. Thereafter, the rhythm was free-running again with a period close to that observed in the first part of the experiment. The conclusion is drawn that, under the influence of periodic feeding, the activity of honeybee colonies has the characteristics of an entrained circadian system.     

Feeding motivation and stereotypies in pregnant sows fed increasing levels of fibre and/or food

Twenty-one multiparous sows were used in a Latin square design, from days 7 to 90 of gestation, to test the effect of fibre and food levels on feeding motivation and feeding-related stereotypies. Treatments were: VHF (very high-fibre, 29% ADF, 50% NDF, 4.5kg/day); HF (high-fibre, 23% ADF, 43% NDF, 3.5kg/day); C (control, 8% ADF, 20% NDF, 2.5kg/day); and control fed ad libitum (CAL). All diets except CAL provided a similar amount of major nutrients on a daily basis and were served in two meals. Each sow was subjected to each treatment for a 21-day period, at the end of which, behavioural observations were made. Two-hour observation periods starting at the afternoon food delivery revealed that sows spent more time eating on VHF and CAL (mean=21.2min) than on HF (13.2min) and C (7.6min) and more time on HF compared to C (p<0.01). When time spent eating was removed from total observation time, the percentage of remaining time spent in stereotypies was lower for VHF (median=17.9%) compared to C (median=49.8%), and lower for CAL (median=6.3%) compared to all other diets (p<0.01). During the period when lights were on (6.00-18.00h), 5min interval scans showed that VHF sows spent more time lying down and less time standing than C sows (p<0.05). Also, CAL sows spent more time lying down than sows on other treatments (p<0.01). During operant conditioning tests (OCT) performed before the afternoon meal and after the morning meal, less rewards were obtained by CAL sows (p<0.01), with no difference between other treatments. In conclusion, no reduction in feeding motivation of sows fed high-fibre diets could be measured by OCT, but very high levels of fibre were effective at reducing stereotypies and activity during the 2h post-feeding. However, these effects were not as marked as those observed with ad libitum feeding.     

Selection for weight gain in mice at two ages and under ad libitum and restricted feeding

Summary Direct and correlated responses in weight gain and body weights were assessed for nine generations of within-family selection. Four selection criteria were used: gain between 28 and 38 or 48 and 58 days of age, and under two feeding regimes, i.e. ad libitum consumption or 80% of the control line. Direct responses to selection and realized heritabilities in the ad libitum lines were greater in the first period. Weight gain under ad libitum feeding at later ages appeared to have a lower genetic variability. In the restricted lines the responses and realized heritabilities were higher in the second period. Selection under restricted feeding in both periods led to animals that had lower weight gains than the control line when compared under ad libitum feeding.     

Effects of feeding time constraints on body mass regulation and energy expenditure in wintering dunlin (Calidris alpina)

We examined the effects of time-restricted feeding on regulationof body mass and activity energy expenditure in captive winteringdunlin (Calidris alpina) held in outdoor aviaries at TomalesBay, California. In the first of two experiments, we comparedbirds under 24 h : 24 h (fasting : ad libitum feeding) foodrestriction with controls under continuous ad libitum feeding. In the second experiment, we compared birds under 24 h : 6 h: 12 h : 6 h (fasting : ad libitum : fasting : ad libitum)food restriction with birds under 24 h : 24 h food restriction.We estimated total energy expended on activities from dailymass balance using an additive model based on measures of grossenergy intake, thermoregulation, basal metabolism, and a sensitivity analysis of gross utilization efficiency and energy densityof reserve body tissue. Dunlin under 24 h : 24 h food restrictionovercompensated for body mass lost while fasting, increasingtheir body mass relative to controls fed ad libitum. Dunlinunder 24 h : 6 h : 12 h : 6 h food restriction were unable to recover body mass lost during the first fasting day. Whenallowed to feed, food-restricted birds reduced the amount ofenergy spent on being active and increased food intake andenergy storage relative to controls, but when forced to fast,they increased their activity energy expenditure. These patterns suggest winter body mass regulation consistent with the behaviorsof free-living dunlin in winter.     

Effects of level of feeding and progesterone dose on plasma and faecal progesterone in ovariectomised cows

The effects of two levels of feeding and two doses of progesterone (P4) on plasma and faecal progesterone metabolites (FP4M) were studied using a total of 24 ovariectomised (OVX), non-lactating, Holstein-Friesian cows. Cows were grazed on improved ryegrass/white clover pastures and allowed ad libitum access to pasture or were restricted to grazing for a total of 4 h per day in two 2 h periods. Progesterone (P4) was administered as one or two, simultaneous, intravaginal progesterone devices (CIDR). The cows were adapted to their pasture supply for 2 weeks before the start of the progesterone treatments. The progesterone devices were administered for 11 days and the cows were dosed with slow release chromic oxide capsules during the P4 treatment to allow faecal output (FO) to be estimated. Daily blood samples for P4 assay and weekly samples for blood metabolite assay were collected. Faecal samples were collected per rectum daily and assayed for pregnanes containing a 20-oxo-, 20alpha- or a 20beta-OH group by enzyme immunoassay (EIA). Daily FO was higher (P < 0.001) for ad libitum than pasture restricted cows (6.3 vs 4.1 kg DM) but was similar for both doses of P4. The average mass of P4 released from a CIDR device over a 11-day period was higher for cows allowed ad libitum pasture compared with those on restricted pasture (0.64 vs 0.60 g; P = 0.04). Plasma P4 concentrations, however, were higher in restricted than ad libitum fed cows (1x CIDR: 1.81 vs 1.41 ng/ml; 2x CIDR: 4.10 vs 3.46 ng/ml). Increasing the progesterone dose significantly (P < 0.001) increased both the concentrations and daily totals of the faecal pregnanes assayed and total FP4M. Restricted pasture cows had higher (P < 0.001) pregnanes and FP4M concentrations than cows fed ad libitum. Daily total faecal pregnane and FP4M did not differ between feeding levels except for faecal 20alpha-pregnane which was highest for ad libitum fed cows (P < 0.05). These results showed that the plasma concentrations of P4 in CIDR-treated OVX cows were negatively associated with the level of feeding. Level of feeding and dose of P4 affected the concentrations of FP4M, but the daily excretion rate of FP4M was not positively influenced by the level of feeding.     

Effects of three-hour restricted food access during the light period on circadian rhythms of temperature, locomotor activity, and heart rate in rats

The effects of food on biological rhythms may influence the findings of chronopharmacological studies. The present study evaluated the influence of a restricted food access during the rest (light) span of nocturnally active Wistar rats on the 24 h time organization of biological functions in terms of the circadian rhythms of temperature (T), heart rate (HR), and locomotor activity (LA) in preparation for subsequent studies aimed at evaluating the influence of timed food access on the pharmacokinetics and pharmacodynamics of medications. Ten-wk-old male Wistar rats were housed under controlled 12:12 h light:dark (LD) environmental conditions. Food and water were available ad libitum, excepted during a 3 wk period of restriction. Radiotelemetry transmitters were implanted to record daily rhythms in T, HR, and LA. The study lasted 7 wk and began after a 21-d recovery span following surgery. Control baseline data were collected during the first wk (W1). The second span of 3 wk duration (W2 to W4) consisted of the restricted feeding regimen (only 3 h access to food between 11:00 and 14:00 h daily) during the L (rest span) under 12:12 h LD conditions. The third period of 3 wk duration (W5 to W7) consisted of the recovery span with ad libitium normal feeding. Weight loss in the amount of 5% of baseline was observed during W1 with stabilization of body weight thereafter during the remaining 2 wk of food restriction. The 3 h restricted food access during the L rest span induced a partial loss of circadian rhythmicity and the emergence of 12 h rhythms in T, HR, and LA. Return to ad libitum feeding conditions restored circadian rhythmicity in the manner evidenced during the baseline control span. Moreover, the MESORS and amplitudes of the T, HR, and LA 24 h patterns were significantly attenuated during food restriction (p < 0.001) and then returned to initial values during recovery. These changes may be interpreted as a masking effect, since T, HR, and LA are known to directly react to food intake. The consequences of such findings on the methods used to conduct chronokinetic studies, such as the fasting of animals the day before testing, are important since they may alter the temporal structure of the organism receiving the drug and thereby compromise findings.     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0%单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。