Digestive efficiency of indigenous and invasive avian species fed fruit of invasive alien plants in South Africa

Many highly invasive plant species produce fleshy fruit that are consumed and dispersed by frugivorous birds. However, little is known about assimilation efficiency of invasive fruit by indigenous and invasive avian species. We investigated whether indigenous Knysna (Tauraco corythaix) and Purple-crested (Gallirex porphyreolophus) Turacos and invasive alien Rose-ringed Parakeets (Psittacula krameri) met their energy demands when fed fruits of four fleshy- fruited invasive alien plant species: Solanum mauritianum, Cinnamomum camphora, Psidium guajava and Morus alba. Birds were fed single-fruit diets for two consecutive days and energetic parameters were calculated for all fruit diets. Our results showed that generally both invasive and indigenous avian species managed to gain their daily energy requirements from fruits of the four respective invasive plants, suggesting that they can meet their energetic demands by feeding on them only. The exception was P. krameri, which did not feed on S. mauritianum fruit. These findings may explain why fruits of invasive alien plants are attractive to most avian frugivores and highlight the role of avian frugivores in their dispersal.     

Plant‐frugivore interactions in an intact tropical forest in north‐east Thailand

Fleshy‐fruited plants in tropical forests largely rely on vertebrate frugivores to disperse their seeds. Although this plant–animal interaction is typically considered a diffuse mutualism, it is fundamental as it provides the template on which tropical forest communities are structured. We applied a mutualistic network approach to investigate the relationship between small‐fruited fleshy plant species and the fruit‐eating bird community in an intact evergreen forest in northeast Thailand. A minimum of 53 bird species consumed fruits of 136 plant species. Plant‐avian frugivore networks were highly asymmetrical, with observed networks filling 30% of all potential links. Whereas some of the missing links in the present study might be due to undersampling, forbidden links can be attributed to size constraints, accessibility and phenological uncoupling, and although the majority of missing links were unknown (58.2%), many were probably due to a given bird species being either rare or only a very occasional fruit eater. The most common frugivores were bulbuls, barbets and fairy‐bluebirds, which were responsible for the majority of fruit removal from small fleshy fruited species in our system. Migratory birds seemed to be a minor component of the plant‐frugivore networks, accounting for only 3% of feeding visits to fruiting trees; they filled 2% of the overall potential networks. The majority of interactions were generalized unspecific; however, Saurauia roxburghii Wall. appeared to be dependent on flowerpeckers for dispersal, while Thick‐billed Pigeons were only seen to eat figs.     

Inter‐specific and intra‐specific variability in fruit color preference in two species of Turdus

One of the main hypotheses proposed to explain the evolution of fruit color deals with a preference of avian frugivores for specific colors, mainly black and red, which are the most common fruit colors in many of the studied habitats. I analyzed fruit color preferences by wild birds belonging to 2 species of the highly frugivorous genus Turdus (Eurasian Blackbird Turdus merula Linnaeus, 1758 and Redwing Turdus iliacus Linnaeus, 1758) by means of captivity experiments with artificial fruits. Despite important within‐individual (i.e. temporal) and among‐individual variability, consistent patterns of species‐specific color preferences emerged. Eurasian Blackbirds tended to prefer red over blue, green and black, whereas Redwings seemed to prefer black over the rest. Green was systematically avoided by both species, suggesting that it might signal unripeness of fruits. Both preferred colors have been previously reported as the most common among fleshy‐fruited plants. The high variability, both within and between individuals, in preferences suggests that they can be subject to changes through experience and learning and, therefore, are not likely to drive the evolution of fruit color. The main differences between both species could be related to the most common fruit color they fed upon during the last months before capture.     

Dietary supplementation of Zingiber officinale and Zingiber zerumbet to heat‐stressed broiler chickens and its effect on heat shock protein 70 expression,blood parameters and body temperature

The present study was conducted to assess the effects of dietary supplementation of Zingiber officinale and Zingiber zerumbet and to heat‐stressed broiler chickens on heat shock protein (HSP) 70 density, plasma corticosterone concentration (CORT), heterophil to lymphocyte ratio (HLR) and body temperature. Beginning from day 28, chicks were divided into five dietary groups: (i) basal diet (control), (ii) basal diet +1%Z. zerumbet powder (ZZ1%), (iii) basal diet +2%Z. zerumbet powder (ZZ2%), (iv) basal diet +1%Z. officinale powder (ZO1%) and (v) basal diet +2%Z. officinale powder (ZO2%). From day 35–42, heat stress was induced by exposing birds to 38 ± 1 °C and 80% RH for 2 h/day. Irrespective of diet, heat challenge elevated HSP70 expression, CORT and HLR on day 42. On day 42, following heat challenge, the ZZ1% birds showed lower body temperatures than those of control, ZO1% and ZO2%. Neither CORT nor HLR was significantly affected by diet. The ZO2% and ZZ2% diets enhanced HSP70 expression when compared to the control groups. We concluded that dietary supplementation of Z. officinale and Z. zerumbet powder may induce HSP70 reaction in broiler chickens exposed to heat stress.     

Testing whether adrenal steroids mediate phenotypic and physiologic effects of elevated salinity on larval tiger salamanders

Salinity (sodium chloride, NaCl) from anthropogenic sources is a persistent contaminant that negatively affects freshwater taxa. Amphibians can be susceptible to salinity, but some species are innately or adaptively tolerant. Physiological mechanisms mediating tolerance to salinity are still unclear, but changes in osmoregulatory hormones such as corticosterone (CORT) and aldosterone (ALDO) are prime candidates. We exposed larval barred tiger salamanders (Ambystoma mavortium) to environmentally relevant NaCl treatments (<32–4000 mg·L⁻¹) for 24 days to test effects on growth, survival, and waterborne CORT responses. Of those sampled, we also quantified waterborne ALDO from a subset. Using a glucocorticoid antagonist (RU486), we also experimentally suppressed CORT signaling of some larvae to determine if CORT mediates effects of salinity. There were no strong differences in survival among salinity treatments, but salinity reduced dry mass, snout–vent length, and body condition while increasing water content of larvae. High survival and sublethal effects demonstrated that salamanders were physiologically challenged but could tolerate the experimental concentrations. CORT signaling did not attenuate sublethal effects of salinity. Baseline and stress-induced (after an acute stressor, shaking) CORT were not influenced by salinity. ALDO was correlated with baseline CORT, suggesting it could be difficult to decouple the roles of CORT and ALDO. Future studies comparing ALDO and CORT responses of adaptively tolerant and previously unexposed populations could be beneficial to understand the roles of these hormones in tolerance to salinity. Nevertheless, our study enhances our understanding of the roles of corticosteroid hormones in mediating effects of a prominent anthropogenic stressor.     

皮质酮处理对产蛋鸡肝脏胆固醇代谢的影响

为研究慢性应激对产蛋鸡肝脏胆固醇代谢的影响,试验选用48只158日龄如皋黄鸡,随机分成2个处理组,每组8个重复,每个重复3只鸡。对照组注射等体积的生理盐水(含15%酒精),试验组注射4 mg/kg的皮质酮,连续注射7 d建立慢性应激模型。试验结束后对其血浆和肝脏中胆固醇含量以及肝脏中胆固醇代谢相关基因的mRNA和蛋白表达进行分析。结果显示:皮质酮处理显著促进了产蛋鸡肝脏重以及肝脏和血浆中总胆固醇含量(P<0.01),显著促进了产蛋鸡肝脏中胆固醇合成基因SREBP2和HMGCR的mRNA和蛋白表达水平(P<0.05),胆固醇降解基因CYP7A1的蛋白表达、CYP27A1和转运基因LDLR的mRNA和蛋白表达水平在皮质酮处理后亦显著上调(P<0.05)。研究表明,皮质酮通过上调肝脏中胆固醇合成基因SREBP2和HMGCR以及转运基因LDLR的mRNA和蛋白表达,进而造成产蛋鸡肝脏中胆固醇累积。     

NDV对雏鸵鸟HPA轴的影响

以45日龄雏鸵鸟为试验动物,分正常组和攻毒组,利用RIA技术和TUNEL技术,探讨新城疫病毒（NDV）对雏鸵鸟HPA轴的影响。结果表明,雏鸵鸟感染NDV,HPA轴内细胞凋亡数量在病毒感染期间明显高于对照组,提示NDV能诱导雏鸵鸟HPA轴系统发生细胞凋亡;在病毒接种后1d,肾上腺内可检测到大量凋亡细胞,接种5d后凋亡数量显著增加（P〈0.05）,之后凋亡呈下降趋势,肾上腺内细胞凋亡的动态变化反映了雏鸵鸟HPA轴对ND病变的适应和调节。雏鸵鸟感染NDV,血清ACTH水平于NDV接种后1d开始上升,至5d达到峰值（P〈0.01）,之后有所下降,渐趋于正常;血清Cor水平于病毒接种后1d开始下降,至7d有所回升,9d渐趋于正常水平,表明NDV接种后雏鸵鸟血清ACTH和Cor水平的变化与其HPA轴功能的损伤及恢复密切相关。     

Effects of ethanol on fruit selection by frugivorous birds

Ethanol is a natural by-product of the fermentation process of fruit sugars. Its production started with the advent of fleshy fruits, which suggests a long-term association between ethanol and frugivores. Consequently, one suggestion is that because frugivores could use its odour to locate fruiting plants, they should show a preference for fruit with high ethanol concentrations. The aim of this study was to test this hypothesis by determining whether frugivorous birds show a preference for fruit laden with alcohol at levels equivalent to those of overripe fruits. Three species of frugivorous bird species were used for this study: the Cape White-eye (Zosterops virens), Speckled Mousebird (Colius striatus) and Red-winged Starling (Onychognathus morio). Birds were provided with two artificial fruit diets in pairwise choice tests: an experimental diet containing 1% ethanol and a control diet with no ethanol. For all species, no significant differences were observed in the amount of artificial fruit consumed between the food types. Given that the concentration of ethanol used in the study is assumed to represent that of overripe fruit, these results, in conjunction with previous studies, suggest that birds do not show a preference for fruits with high ethanol concentrations.     

郁金散对大肠湿热证大鼠HPA轴的影响机制

基于分子对接并辅以生物学验证探讨郁金散治疗大肠湿热证HPA轴损伤的机制。采用高效液相色谱法(High Performance Liquid Chromatography,HPLC)检测郁金散的主要活性成份,用分子对接观察其活性成分与HPA轴相关激素、蛋白之间的结合力,通过网络药理学分析构建药物靶标网络,预测郁金散活性成分作用的主要靶标,并建立大肠湿热证大鼠模型,进行生物学验证。计算各组大鼠肾上腺指数,观察肾上腺组织变化特征,检测关键靶标及其下游激素的表达量。分子对接与网络分析可以推测CRH可能是调控HPA轴亢进的潜在蛋白,盐酸小檗碱、没食子酸、大黄素可能是郁金散调节HPA轴亢进的活性成分。生物学验证实验结果表明,与空白对照组相比,模型组和自愈组大鼠肾上腺指数及血清中CRH、ACTH、CORT的含量显著或极显著升高(P<0.05或P<0.01),模型组大鼠肾上腺出现一定的病理变化。经郁金散治疗后,以上各指标及病理变化均有所改善,其中以郁金散高剂量组治疗效果最佳,验证了分子对接的部分预测结果。研究证实郁金散可能是通过下调CRH的水平调节大肠湿热证大鼠HPA轴功能亢进,为进一步开展郁金散治疗HPA轴亢进的机制研究提供了新思路和新方法。     

Physiological but not morphological adjustments along latitudinal gradients in a human commensal species,the Eurasian tree sparrow

Human commensal species take advantage of anthropogenic conditions that are less likely to be challenged by the selective pressures of natural environments. Their morphological and physiological phenotypes can therefore dissociate from habitat characteristics. Understanding how these species adjust their morphological and physiological traits across latitudinal gradients is fundamental to uncovering the eco-physiological strategies underlying coping mechanisms. Here, we studied morphological traits in breeding Eurasian tree sparrows (ETSs; Passer montanus) among low-latitude (Yunnan and Hunan) and middle-latitude (Hebei) localities in China. We then compared body mass; lengths of bill, tarsometatarsus, wing, total body, and tail feather; and baseline and capture stress-induced levels of plasma corticosterone (CORT) and the metabolites including glucose (Glu), total triglyceride (TG), free fatty acid (FFA), total protein, and uric acid (UA). None of the measured morphological parameters varied with latitude except in the Hunan population, which demonstrated longer bills than those in other populations. Stress-induced CORT levels significantly exceeded baseline levels and decreased with increasing latitude, but total integrated CORT levels did not vary with latitude. Capture stress-induced significantly increased Glu levels and decreased TG levels, independent of site. However, the Hunan population had significantly higher baseline CORT, baseline and stress-induced FFA levels, but lower UA levels, which differed from other populations. Our results suggest that rather than morphological adjustments, physiological adjustments are mainly involved in coping mechanisms for middle-latitude adaptation in ETSs. It is worth investigating whether other avian species also exhibit such dissociation from external morphological designs while depending on physiological adjustments.     

Alterations in carbohydrate metabolism by exogenous dexamethasone and corticosterone in post-hatched White Leghorn chicks.

1. Alterations in carbohydrate metabolism in terms of tissue glycogen contents, phosphorylase (EC 2.4.1.1) activity, hepatic glucose-6-phosphatase (6-6-Pase: EC 3.1.3.9) activity and blood glucose have been evaluated in 30-d-old White Leghorn chicks under induced chronic hypocorticalism (by dexamethasone: DXM) and hypercorticalism (by corticosterone: CORT). 2. DXM treatment showed increased tissue glycogen contents and hypoglycaemia with decreased phosphorylase activity while CORT treatment produced a reverse set of changes. 3. Both steroid treatments increased hepatic G-6-Pase activity. These observations have been taken to indicate a definite role for glucocorticoids in regulating carbohydrate metabolism in neonatal chicks. 4. It is suggested that hypo- or hyper-corticalism could influence carbohydrate metabolism by affecting the secretory/activity ratio of pancreatic hormones.     

肉鸡神经内分泌免疫网络抗传染性法氏囊病病毒感染的机制

以Ａｖｉａｎ鸡为实验对象，研究了神经内分泌免疫网络在传染性法氏囊病病毒（ＩＢＤＶ）弱毒免疫和强毒感染时发生的调节机制。结果表明，ＩＢＤＶ弱毒免疫能获得高滴度的血清ＩＢ－ＤＶ抗体。未免疫肉鸡感染ＩＢＤＶ强毒后会引起免疫功能抑制。ＩＢＤＶ攻毒后，肉鸡血浆皮质酮、ｃＧＭＰ升高，Ｔ淋巴细胞转化率、白介素－２活性明显降低。ＩＢＤＶ弱毒免疫肉鸡遭受ＩＢＤＶ强毒感染后，血浆ｃＡＭＰ和ｃＧＭＰ同时升高并呈现高阈平衡。ＩＢＤＶ攻毒前后，肉鸡血浆ＡＣＴＨ、皮质酮和免疫功能指标间有显著的相关性，提示外来病原入侵后，肉鸡垂体－肾上腺轴可调节免疫功能，主要是抑制非特异性免疫反应而增强特异性免疫反应     

脂多糖刺激对断奶仔猪下丘脑-垂体-肾上腺轴PPARγ表达的影响

研究脂多糖(LPS)对断奶仔猪下丘脑-垂体-肾上腺(HPA)轴过氧化物酶体增殖物活化受体γ(PPARγ)表达的影响。对照组注射生理盐水,试验组注射LPS。注射后1.5 h和3 h采血,3 h采血后屠宰。结果表明:LPS刺激后1.5 h,中性粒细胞含量及其比例显著下降(P<0.05);LPS刺激后3 h,白细胞、淋巴细胞、中性粒细胞含量显著下降(P<0.05)。LPS刺激后1.5 h,血浆肿瘤坏死因子(TNF)-α、皮质醇和促肾上腺皮质激素释放素激素(CRH)含量显著上升(P<0.05);LPS刺激后3 h,血浆TNF-α、皮质醇和促肾上腺皮质激素(ACTH)含量显著上升(P<0.05);LPS刺激导致下丘脑、腺垂体、肾上腺皮质和髓质中PPARγ阳性细胞百分率显著升高(P<0.05)。这表明LPS导致免疫应激,激活HPA轴,诱导HPA轴PPARγ的表达。     

Hypothalamic-pituitary-adrenal axis responsiveness to insulin-induced hypoglycaemia is modified by trypanosome infection in Boran (Bos indicus) cattle.

Ten Boran (Bos indicus) cattle were used to study the stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis during trypanosome infection. Five cattle were infected with Trypanosoma congolense IL 1180 by tsetse challenge and five cattle served as controls. All infected animals developed acute trypanosomiasis. Insulin-induced hypoglycaemia (50 per cent of pre-insulin glucose concentration) was used as a stress factor. Acute hypoglycaemia was observed in three infected and three control animals after insulin challenge. Two animals from each group either did not respond or responded slowly. Hypoglycaemia in infected animals completely failed to induce an HPA axis response, while in control animals an HPA axis response was indicated by a significant increase in plasma adrenocorticotrophic hormone (ACTH) and cortisol concentrations (P less than 0.01). The results show that trypanosomiasis in Boran cattle can cause a decrease in the stress responsiveness of the HPA axis as indicated by a blunted ACTH/cortisol response to insulin-induced hypoglycaemia.     

Dysregulated metabolism and behaviors by disrupting gut microbiota in prenatal and neonatal mice

The live microbiota ecosystem in the intestine plays a critical role in maintaining the normal physiological and psychological functions in both animals and human beings. However, the chronic effect of microbiota disturbances during prenatal and neonatal developing periods on animal's health remains less studied. In the current study, pregnant ICR mice were fed with an antibiotic diet (7-g nebacitin [bacitracin-neomycin sulphate 2:1]/kg standard diet) from day 14 of conception, and their offspring were provided with the same diet till the termination of the experiments. Dams treated with antibiotics showed increased body weight along with enlarged gut. Antibiotic-treated offspring revealed decreased bodyweight, increased food, water, and sucrose intake. Administration of antibiotics affected corticosterone responsivity to acute 20 min restraint challenge in male pups. In behavior tests, female pups showed decreased movement in open field while male pups revealed decreased latency to open arms in elevated plus maze test and immobility time in tail suspension test. Together, these results suggested that early antibiotic exposure may impact on the food intake, body weight gain, and emotional behavior regulation in mice.     

Effect of intracerebroventricular injections of prolactin‐releasing peptide on prolactin release and stress‐related responses in steers

Some evidence suggests that there might be a species difference in the effect of intracerebroventricularly administered (ICV) prolactin‐releasing peptide (PrRP) between rodents and sheep. We compared the levels of cortisol (CORT) and prolactin (PRL), rectal temperature (RT) and behavioral responses to ICV bovine PrRP (bPrRP) in steers. ICV bPrRP (0.2, 2 and 20 nmol/200 µL) tended to evoke a dose‐related increase in CORT concentrations and 0.2 nmol of bPrRP induced transient increase in PRL concentrations. A significant time–treatment interaction was observed for the percent change of CORT (P < 0.05) and PRL (P < 0.05) from pre‐injection value. The time–treatment interaction for changes in RT was not significant (P = 0.50). There tended to be a difference among the four treatments in terms of maximum change in RT from the pre‐injection value between 0 and 90 min (P < 0.1). Stress‐related behavioral signs were not observed in the present experiment. These findings indicate that ICV bPrRP increased CORT and PRL levels, suggesting that central PrRP might participate in controlling the hypothalamo‐pituitary‐adrenal axis and PRL release in cattle, unlike sheep. In contrast, central PrRP is unlikely to be involved in controlling the behavior of this species because ICV bPrRP did not induce marked changes in their behavior.     

Selection of foods by broiler chickens following corticosterone administration

1. The effects of corticosterone (CORT) on diet selection of broiler chickens offered a choice of a high protein concentrate (381 g CP/kg, 17.5 MJ/kg ME) and whole wheat (113 g CP/kg, 15.9 MJ/kg ME) in relation to age were examined in two experiments.

2. Daily intramuscular injections of 2 and 4 mg/kg of CORT for a 5‐d period in both 2‐ and 5‐week‐old chickens resulted in increases in total food, protein and energy intakes. This led to a decrease in protein accretion in older but not younger chicks, an increase in total lipid contents of the carcase at both ages, and produced changes in internal organs.

3. CORT significantly reduced body weight gain of young but not old chickens, suggesting that mature birds respond better than young ones to the physiological changes caused by treatment, by making subsequent appropriate food choices.

4. Administration of CORT in young chicks increased wheat intake at 2 and 4 h after injection, while in older birds a similar increase was maintained up to 24 h after injection. Intake of HP food was decreased by both doses of CORT in young chicks but there was no significant effect in older chickens.

5. Changes in energy: protein ratio in the chosen diet appeared at 4 h after treatment in old chickens and at 24 h in younger chicks.

6. The results suggest that birds are able to detect metabolic changes caused by CORT administration and attempt to redress them by modifying their food pattern. The time course of the response of birds to these changes is age related. However, the food selection pattern did not completely compensate for the physiological defects.     

Effects of corticosterone treatment in laying Japanese quail

1. The effects of exogenous corticosterone on plasma corticosterone concentrations, body weight, food intake, the percentage of birds that laid an egg each day and egg weight were measured in laying Japanese quail. Data were collected from birds in the week before corticosterone treatment began, during a 21-d treatment period, and in the 22 d after treatment ended.

2. Groups of quail were treated with corticosterone at three different concentrations in their drinking water. Corticosterone intakes were calculated for each bird and birds were then assigned to 4 intake groups. The groups were 0 (control group), 0·31–0·60, 0·61–0·90, 0·91–1·50 or >1·51 mg corticosterone/bird/d.

3. Plasma corticosterone concentrations in the 4 intake groups increased from around 1 ng/ml on the day before corticosterone treatment began to maximum mean concentrations of 13–18 ng/ml on day 14 of treatment. Mean corticosterone concentrations did not change between day 14 of treatment and the day after treatment ended, and had decreased in only one of 4 intake groups one week later.

4. Mean body weight in the highest intake group remained significantly lower than in controls 22 d after corticosterone treatment ended. Whilst there was no clear effect of corticosterone on food intake during treatment, mean food intake in the three highest corticosterone intake groups was significantly lower than in controls in the week after treatment ended. The percentage of birds that laid an egg each day and egg weight were both decreased by corticosterone, and the percentage of birds that laid an egg each day remained significantly lower in the highest corticosterone intake group compared with controls in the third week after treatment ended.

5. It is suggested that elevated plasma corticosterone concentrations in quail after treatment ended were maintained by a hyperactive hypothalamo–pituitary–adrenal axis for at least one week. Although none of the negative effects of corticosterone were evident in the group of quail with the lowest corticosterone intakes, the findings of the present study show that corticosterone treatment can affect birds for up to several weeks after corticosterone intake ends.     

Development of the chicken as a model for prenatal stress

Exposing a pregnant mammal to stressors causes behavioral and physiological alterations in her offspring ("prenatal stress"); however, elucidation of the underlying mechanism is hindered by an inability to control maternal compounds that may affect the fetus. We designed this experiment to determine if the autonomously developing chicken embryo could be developed as a model for prenatal stress. On d 16 of incubation, eggs were treated with: 1) 60 ng corticosterone (CORT), 2) elevated incubation temperature (40.6 degrees C) for 24 h (HEAT), or 3) no treatment (Control). Chicks from all three treatments hatched at similar weights; however, HEAT chicks weighed less by 100 d of age and remained lighter until the end of the study (P < 0.05). At 8 d post-beak trimming, adrenal gland weight was not different (P > 0.20) among treatments, basal plasma corticosterone concentrations tended (P < 0.06) to be greater for CORT chicks than either the Control or HEAT chicks, and CORT chicks were heavier than HEAT chicks (P < 0.005) but not Control chicks (P > 0.20). At 11-wk, HEAT birds had heavier adrenal glands than did Control birds (P < 0.01). At 16 wk of age, Control cocks performed more (P < 0.01) pecking aggression than either HEAT or CORT cocks, whereas CORT cocks were chased more often and chased another cock less often than either HEAT or Control cocks (P < 0.01). Treatments did not alter the behavior of the hens (P > 0.10). Administration of corticosterone during incubation replicated some, but not all, of the effects seen in prenatal stress in mammals.     

The regulation of food intake and correlated energy balance in mice.

In order to study the regulation of food intake and correlated body energy metabolism, the effect of restricted feeding during the light period in female IVCS mice was investigated. Access to food and water was restricted (RF group) for 3 weeks only from 10:00 hr to 17:00 hr, and that in the control group remained ad libitum. After starting food restriction (day 1), mean food intake decreased to 10% of the control value, then rose sharply, over the next 3 days, to reach 70% of the control value. Then, it decreased gradually to about 50% of the control value and remained at this low level thereafter. There was no significant difference between mean body weights for the two groups. Feed-efficiency was considered, therefore, to be higher in the RF than in the control group. RF-treatment increased plasma corticosterone levels and decreased locomotor activity. However, the diurnal patterns of plasma corticosterone levels and locomotor activity observed suggest that the circadian rhythm, synchronized with the light-dark cycle, persisted during RF-treatment. These findings suggest that restricted feeding during the naturally inactive phase (light period) induces a decrease in food intake. Animals seem to adapt to underfeeding, at least partly, by increasing feed-efficiency and plasma corticosterone levels and decreasing locomotor activity.