Restricted Feeding Conditions Research Articles

Genomic selection for individual feed efficiency in the European seabass: Response to selection on efficiency, commercial traits and sex

Feed efficiency is a key factor in the sustainability of fish farming. Improving feed efficiency not only results in cost savings, but also helps to reduce the environmental footprint associated with feed production and to mitigate competition for feed resources. However, improving feed efficiency through genetic selection poses challenges, mainly due to the difficulty of accurately estimating it in a large population, especially under conventional rearing conditions. In a previous study, a methodology was developed to estimate the individual feed efficiency of sea bass in separate tanks under controlled feeding regimes during the juvenile phase. This approach allowed precise measurement of growth, feed intake and individual feed conversion ratio (iFCR) of each fish. Daily growth rate (iDGC) was found to be highly heritable (h2 = 0.75), and a reliable predictor of iFCR under restricted feeding conditions. In the present study, we aim to demonstrate the response to selection on feed efficiency, commercial traits and sex.From a cohort of 399 sea bass with known iDGC and genotyped for 1110 SNP markers, we selected 27 future efficient parents (Eff+), 35 intermediate parents (Eff0) and 29 inefficient parents (Eff-) by genomic selection (GBLUP). Three years later, 3 groups of offspring were produced from 9 Eff + parents, 13 Eff0 parents and 19 Eff- parents. Performances in individual aquaria (iDGC, iFCR) were assessed for 259 of them, as well as group feed efficiency (gFCR) from 142 g. At 240 g, the fish were slaughtered to assess processing traits.The results showed that the Eff + group had superior efficiency (iFCR and iDGC) and better adaptability to tank conditions compared to the other groups. In the group evaluation phase, significant differences in feed efficiency were observed between Eff- (gFCR = 1.83) and Eff + (gFCR = 1.61) (p < 0.001), with Eff0 being intermediate. In addition, Eff + fish were larger (266 g, 27.4 cm) and leaner with lower Fulton K values compared to Eff0 (234 g, 26.1 cm) and Eff- (223 g, 25.5 cm). Although there were no differences in fillet yield, Eff + had a slightly higher viscerosomatic index. There was also a higher proportion of females in the Eff- (57.1 %) and Eff0 (51.6 %) groups compared to Eff + (43.9 %).In conclusion, selection for feed efficiency in individual tanks is an effective strategy for improving the performance of sea bass, resulting in significant improvements with a marked effect on growth rates. Despite a slight increase in the viscerosomatic index, fillet yield was not significantly affected.

Photoperiod, food restriction and memory for objects and places in mice

The suprachiasmatic nucleus (SCN) contains a population of cell-autonomous circadian oscillators essential for entrainment to daily light–dark (LD) cycles. Synchrony among SCN oscillators is modified by photoperiod and determines functional properties of SCN clock cycling, including its amplitude, phase angle of entrainment, and free running periodicity (τ). For many species, encoding of daylength in SCN output is critical for seasonal regulation of metabolism and reproduction. C57BL/6 mice do not show seasonality in these functions, yet do show photoperiodic modulation of SCN clock output. The significance of this for brain systems and functions downstream from the SCN in these species is largely unexplored. C57BL/6 mice housed in a long-day photoperiod have been reported to perform better on tests of object, spatial and fear memory compared to mice in a standard 12 h photoperiod. We previously reported that encoding of photoperiod in SCN output, evident in τ in constant dark (DD), can be blocked by limiting food access to a 4 h mealtime in the light period. To determine whether this might also block the effect of long days on memory, mice entrained to 18 h:6 h (L18) or 6 h:18 h (L6) LD cycles were tested for 24 h object memory (novel object preference, NOP) and spatial working memory (Y-maze spontaneous alternation, SA), at 4 times of day, first with food available ad libitum and then during weeks 5–8 of daytime restricted feeding. Photoperiod modified τ as expected, but did not affect performance on the NOP and SA tests, either before or during restricted feeding. NOP performance did improve in the restricted feeding condition in both photoperiods, eliminating a weak time of day effect evident with food available ad-libitum. These results highlight benefits of restricted feeding on cognitive function, and suggest a dose–response relationship between photoperiod and memory, with no benefits at daylengths up to 18 h.

Circadian-driven tissue specificity is constrained under caloric restricted feeding conditions

Tissue specificity is a fundamental property of an organ that affects numerous biological processes, including aging and longevity, and is regulated by the circadian clock. However, the distinction between circadian-affected tissue specificity and other tissue specificities remains poorly understood. Here, using multi-omics data on circadian rhythms in mice, we discovered that approximately 35% of tissue-specific genes are directly affected by circadian regulation. These circadian-affected tissue-specific genes have higher expression levels and are associated with metabolism in hepatocytes. They also exhibit specific features in long-reads sequencing data. Notably, these genes are associated with aging and longevity at both the gene level and at the network module level. The expression of these genes oscillates in response to caloric restricted feeding regimens, which have been demonstrated to promote longevity. In addition, aging and longevity genes are disrupted in various circadian disorders. Our study indicates that the modulation of circadian-affected tissue specificity is essential for understanding the circadian mechanisms that regulate aging and longevity at the genomic level.

Transcriptome Analysis of Compensatory Growth and Meat Quality Alteration after Varied Restricted Feeding Conditions in Beef Cattle.

Compensatory growth (CG) is a physiological response that accelerates growth following a period of nutrient limitation, with the potential to improve growth efficiency and meat quality in cattle. However, the underlying molecular mechanisms remain poorly understood. In this study, 60 Huaxi cattle were divided into one ad libitum feeding (ALF) group and two restricted feeding groups (75% restricted, RF75; 50% restricted, RF50) undergoing a short-term restriction period followed by evaluation of CG. Detailed comparisons of growth performance during the experimental period, as well as carcass and meat quality traits, were conducted, complemented by a comprehensive transcriptome analysis of the longissimus dorsi muscle using differential expression analysis, gene set enrichment analysis (GSEA), gene set variation analysis (GSVA), and weighted correlation network analysis (WGCNA). The results showed that irrespective of the restriction degree, the restricted animals exhibited CG, achieving final body weights comparable to the ALF group. Compensating animals showed differences in meat quality traits, such as pH, cooking loss, and fat content, compared to the ALF group. Transcriptomic analysis revealed 57 genes and 31 pathways differentially regulated during CG, covering immune response, acid-lipid metabolism, and protein synthesis. Notably, complement-coagulation-fibrinolytic system synergy was identified as potentially responsible for meat quality optimization in RF75. This study provides novel and valuable genetic insights into the regulatory mechanisms of CG in beef cattle.

The effect of dietary supplementation of organic trace minerals on performance, mineral retention, lymphoid organs and antibody titres of broilers

Complete replacement of inorganic trace minerals (ITM) with proteinated organic trace minerals (PTM) at equal or lower inclusion rates was evaluated. One thousand and eight, one-d-old male chicks were divided into 24 pens containing 42 chicks, and randomly allocated to one of the following: T1: control group with ITM supplied at the standard commercial level in Ecuador; T2: PTM at 100% T1; T3: PTM at 66% TI; and T4: PTM at 33% T1. The 42-d experiment employed a three-phase feeding programme (1-14, 15-28 and 29-42 d). Restricted feeding was used to prevent the development of ascites associated with high altitude. At 21 and 42 d of age, Cu, Mn and Zn retention were measured in tibial bone, and Fe in whole blood. Lymphoid organ weights were at 21 and 42 d of age. Antibody titres were measured by ELISA at 42 d of age. Weight gain, feed consumption, feed conversion and mortality were similar among treatments, although were below breed expectations due to feed restriction practices. Blood Fe was not affected by treatment (P&lt;0.05). At both 21 and 42 d of age, minerals in tibia differed (P&lt;0.01), with Mn and Zn concentrations being significantly higher in all PTM groups, compared to ITM control at 42 d. However, at 21 d, Zn was higher for the ITM-fed birds. No differences in lymphoid organ (bursa, thymus, and spleen) weights were observed, or for Gumboro (infectious bursal disease), infections bronchitis virus and reovirus antibody titres. For Newcastle disease virus, T4 birds had significantly lower antibody titres compared to other treatment groups. In conclusion, replacement of inorganic minerals with a proteinated form organic minerals at lower inclusion rates had no negative impact on performance, lymphoid organ weight or antibody titres in broilers raised under commercial conditions of high altitude and restricted feeding.

Thermoregulatory role of ghrelin in the induction of torpor under a restricted feeding condition

Ghrelin, a circulating orexigenic hormone secreted from the stomach, stimulates appetite and food intake by activating the hypothalamic arcuate nucleus. Administration of exogenous ghrelin exerts anabolic effects, causing weight gain, increased adiposity, and decreased metabolism. Body temperature (BT), which is determined by the balance of heat production and heat loss, must be strictly regulated to maintain proper cellular function and metabolism. However, the role of ghrelin in thermoregulation remains unclear. In this study, we found that ghrelin was essential for decreasing BT when mice are placed under calorie restriction. Elevated ghrelin concentrations induced by fasting correlated with significant decreases in BT, a hibernation-like state called torpor. Ghrelin-deficient (Ghrl−/−) animals could not enter torpor. The BT of Ghrl−/− mice also remained high under restricted feeding, but the animals gradually entered precipitous hypothermia, indicating thermoregulatory impairment. These effects of ghrelin on thermoregulation were the result of suppression of sympathetic nervous system activity input to brown adipose tissue; in the absence of ghrelin, it was not possible to suppress uncoupling protein 1 (ucp1) expression and decrease BT in low-energy states. Together, these findings demonstrate that ghrelin is an essential circulating hormone involved in lowering BT.

Continuous and non-invasive thermography of mouse skin accurately describes core body temperature patterns, but not absolute core temperature

Body temperature is an important physiological parameter in many studies of laboratory mice. Continuous assessment of body temperature has traditionally required surgical implantation of a telemeter, but this invasive procedure adversely impacts animal welfare. Near-infrared thermography provides a non-invasive alternative by continuously measuring the highest temperature on the outside of the body (Tskin), but the reliability of these recordings as a proxy for continuous core body temperature (Tcore) measurements has not been assessed. Here, Tcore (30 s resolution) and Tskin (1 s resolution) were continuously measured for three days in mice exposed to ad libitum and restricted feeding conditions. We subsequently developed an algorithm that optimised the reliability of a Tskin-derived estimate of Tcore. This identified the average of the maximum Tskin per minute over a 30-min interval as the optimal way to estimate Tcore. Subsequent validation analyses did however demonstrate that this Tskin-derived proxy did not provide a reliable estimate of the absolute Tcore due to the high between-animal variability in the relationship between Tskin and Tcore. Conversely, validation showed that Tskin-derived estimates of Tcore reliably describe temporal patterns in physiologically-relevant Tcore changes and provide an excellent measure to perform within-animal comparisons of relative changes in Tcore.

Effect of time-restricted feeding on 24-h rhythm in phototactic behavior of zebrafish

ABSTRACT Among all other repertoire of behaviors, phototactic behavior is one of the most vital behaviors. Our knowledge on the impact of time-restricted feeding on phototactic behavior of fish is critically limited. In this study, we examined the effect of time-restricted feeding schedule on 24-h rhythm in phototactic behavior of zebrafish (Danio rerio). We kept fish in the specially designed aquaria consisting of a photic and a non-photic zone under natural day length condition and fed once in a day, either randomly or at 1200 or 1600. We recorded the frequency of fish in the photic zone every day between 1000 and 1800 for six to nine consecutive days. Statistically significant 24-h rhythms in the frequency of fish were validated at the group level, irrespective of the feeding schedule. It is difficult to explain why the fish fed at 1200 only exhibited food anticipatory activity (FAA). The 24-h average decreased and acrophase delayed significantly in this group as compared with the others. The amplitude of the phototactic rhythm dampened under restricted feeding condition as compared with the fish on random feeding. Nonetheless, the present findings underscore the role of time-restricted feeding as a powerful modulator of the 24-h rhythm in phototactic behavior.

A microarray-based comparative analysis of gene expression profiles in thyroid glands in amphibian metamorphosis: differences in effects between chemical exposure and food restriction.

Tadpoles during metamorphosis are sensitive to chemical exposure as shown in the amphibian metamorphosis assay, which is a method to detect effects of chemicals on the functions of hypothalamus-pituitary-thyroid axis. The present study reports existence of different modes of action between pyriproxyfen (PYR) and 6-propyl-2-thiouracil (PTU) under different feeding conditions based on gene expression profiles (transcriptomics) in the thyroid glands of tadpoles of the African clawed frog, Xenopus laevis. PTU and PYR were exposed to the tadpoles during metamorphosis under normal (fed groups, both of PTU and PRY) and restricted feeding (fasted groups, PTU only) conditions; and effects were compared to control groups. Delayed development based on decreased Nieuwkoop and Faber developmental stage number without any histopathological changes was observed in the control of restricted feeding (control-fasted) group, and the PYR group with reduced food consumption. Clear developmental retardation with typical thyroid histopathological changes was observed in the PTU groups. To find clusters of all samples based on their similarity of expression patterns, hierarchical clustering analysis using selected gene probes was conducted. It revealed gene profiles from samples of the PYR group were quite similar to those of the control-fasted group, followed by the control group with normal feeding (control-fed). The results suggest that key events in the thyroid glands of tadpoles induced by PYR should be quite similar to those of control-fasted, and quite different from those of the PTU groups. Our findings demonstrated the usefulness of transcriptomics, which enabled recognition of the different modes of actions.

Mytilus galloprovincialis fast growing phenotypes under different restrictive feeding conditions: Fast feeders and energy savers

The present study aims to test if the environmental conditions prevailing during the growing period can determine the physiological profiles of specimens differentiated as fast (F) or slow (S) growers in the mussel Mytilus galloprovincialis. We reared mussel spats in the laboratory under two different conditions. In Treatment I (continuous feeding during discontinuous immersion), two mussel groups were submitted to a daily air exposure of 8 h and fed continuously during immersion-time, with either high-quality food dosed below the pseudofaeces threshold (BP group) or low organic content food dosed above the pseudofaeces threshold (AP group). In Treatment II (discontinuous feeding during continuous immersion), mussels were continuously immersed but fed only 1 day per week (RC group). Mussels were reared for 7 and 11 months (time required for size-differentiation) in Treatments I and II, respectively, and the smallest and largest individuals from each group were selected as S and F specimens.A series of feeding experiments (with different food quality, food ration and under continuous food supply) were performed to analyse the physiological performance of selected F and S mussels. In Treatment I, no significant differences were found in the metabolic rates between F and S mussels, and the faster growth rate of F-mussels resulted from their capacity to display higher clearance-ingestion rates and pre-ingestive selections. The physiological basis of growth rate differences between F and S mussels were found to be the same in mussels reared with diets below or above a pseudofaeces threshold (FBP, FAP, SBP and SAP). In contrast, the mussels from Treatment II had no significant differences in the feeding rates between FRC and SRC mussels. However, F individuals were found to have a 33% lower standard metabolic rate, indicating that fast growth under severe feeding restriction stemmed from a higher capacity of F-mussels to save energy during long periods of starvation. Despite the differences in the physiological basis explaining fast growth between the two treatments, F-mussels were found to possess significantly higher gill-surface area in both cases. It is thus concluded that endogenous factors affecting the gill-surface area play a major role in determining inter-individual growth rate differences in the mussel, Mytilus galloprovincialis.

An analysis of the indirect genetic effect on the body weight of Fenneropenaeus chinensis under restrictive feeding conditions

PDF HTML阅读 XML下载 导出引用 引用提醒 限制投喂环境下中国对虾体重的间接遗传效应分析 DOI: 作者: 作者单位: 1. 上海海洋大学水产与生命学院, 上海 201306;2. 中国水产科学研究院黄海水产研究所, 农业农村部海洋渔业资源可持续利用重点开放实验室, 山东 青岛 266071;3. 青岛海洋科学与技术国家实验室海洋渔业科学与食物产出过程功能实验室, 山东 青岛 266071 作者简介: 仲伟鹏(1992-),男,硕士研究生,主要从事水产动物遗传育种研究.E-mail:pingtanxue@163.com 通讯作者: 中图分类号: S917 基金项目: 国家自然科学基金面上项目（31572616）；泰山学者种业人才团队项目；现代农业产业技术体系专项（CARS-48）. An analysis of the indirect genetic effect on the body weight of Fenneropenaeus chinensis under restrictive feeding conditions Author: Affiliation: 1. College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China;2. Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Qingdao 266071, China;3. Qingdao National Laboratory of Marine Science and Technology, Functional Laboratory of Marine Fishery Science and Food Production Process, Qingdao 266071, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究竞争性环境下中国对虾（）体重性状的间接遗传效应，设计多家系多分组方案，对来源于中国对虾G11代育种群体的103个测试家系限制配合饲料投喂量（正常投喂量50%），利用经典动物模型和包含间接遗传效应的扩展动物模型估算收获体重的遗传参数。基于2种模型估计出的经典遗传力分别为0.581±0.071和0.616±0.074。似然比率检验表明，体重的间接遗传效应显著，对总遗传方差的贡献度高达75.03%。由于存在一个较大的负直接遗传效应与间接遗传效应协方差（-2.1982），导致总遗传方差与表型方差的比值仅为0.524±0.212，小于经典的遗传力估计值。基于协方差获得的直接遗传效应与间接遗传效应的遗传相关系数为-0.495±0.184，暗示测试个体间存在较强的竞争交互。本研究表明，在饲料投喂量受限制的竞争性环境下，对虾个体间较强的竞争交互行为，对中国对虾收获体重间接产生了可遗传的效应，减少了可利用的总遗传变异。今后在设计中国对虾育种方案时，应避免在资源受限的强竞争环境下开展性状测试和遗传评估。 Abstract:An additive effect is the main genetic determinant of the phenotypic value of a quantitative trait, but it is a direct genetic effect (DGE) of the trait itself, ignoring the genetic influence of social interaction among individuals in the same group. The expression of genes of an individual has an influence on the phenotypic values of others in the same group, which is an indirect genetic effect (IGE). IGE is generated by social interaction among individuals in the group. IGE has been widely reported in animals and plants. For aquatic animals, IGE has been determined in Nile tilapia, Atlantic cod, and the Pacific white shrimp. The Chinese shrimp () is one of the most representative aquaculture species in China. In , cannibalism and frequent attacks are common phenomena. Attacks among individuals under environmental stress and the fight for food may affect the growth of shrimps. In order to study the indirect genetic effects of body weight in under restrictive feeding conditions, 103 families of the eleventh generation of the breeding population were tested using a multi-family by multi-group design. They were reared for about three months with limited feed and harvest body weight was measured for each individual. Genetic parameters of harvest body weight were estimated using an extended animal model, including IGE. The results showed that the IGE of body weight was significant, with a contribution to the total genetic variance reaching up to 75.03%. There was a negative covariance (-2.1900) between DGE and IGE. Based on the model with IGE, the ratio of total genetic variance to phenotypic variance was 0.524±0.212, which was less than the traditional estimate of heritability (0.616±0.074). In addition, there was a negative genetic correlation between the direct and indirect genetic effects (-0.495), implying that the existence of competitive effects may be detrimental to selective responses. This study demonstrated strong social interaction (competition among individuals) exists in a population of under restrictive feeding conditions, which had a heritable effect on body weight. Considering that the indirect genetic effect under the competitive environment has a greater negative impact on selection, it is inadvisable to conduct breeding programs under a competitive environment. 参考文献 相似文献 引证文献

Development of nitrogen and methane losses in the first eight weeks of lactation in Holstein cows subjected to deficiency of utilisable crude protein under restrictive feeding conditions

ABSTRACTLow-protein diets are increasingly being used in dairy cow nutrition to minimise noxious nitrogen (N) emissions. However, at parturition, the lower milk yield at that time may mask deficiency in dietary utilisable crude protein (uCP; equivalent to metabolisable protein). Under restrictive feeding conditions, farmers would limit the feed allowance to match the lower measured milk yield, thereby exacerbating the deficiency. The consequences for N emission intensity per kg milk yield and methane emissions are unknown. In this study, two diets were fed to nine Holstein cows each from parturition onwards. One diet was complete and the other was calculated as 20% deficient in uCP. Feed allowance was always oriented towards the measured milk yield. In each of the first eight lactation weeks, intake and excretion were measured for 5 d. On the last 2 d of this period, methane emission was measured in respiration chambers. The statistical model included treatment, week and interaction as effects. The real levels of uCP and energy supply across the 8 weeks were 33% and 15% below requirements, respectively, in the Deficient cows. In addition, the Deficient cows consumed 18% less dry matter (caused by substantial refusals in week 1, where energy supply was according to requirements) and produced 25% less milk (26 vs. 34 kg/d). Cows in both groups used dietary N with similar efficiency for milk protein synthesis and excreted similar proportions of the N ingested via urine and faeces. This resulted in both treatments having similar N emission intensities per kg milk N and similar urinary N as a proportion of total excreta N, suggesting a similar potential for gaseous N emissions from the manure per kg of milk. The Deficient cows emitted 22% less methane overall but had similar methane yield and emission intensity to the Controls. In conclusion, a reduction in crude protein intake immediately after parturition does not reduce N emission per unit of milk when associated with uCP deficiency.

Food regime modulates physiological processes underlying size differentiation in juvenile intertidal mussels Mytilus galloprovincialis

Feeding and growth experiments were conducted to test the hypothesis that physiological attributes responsible for size differentiation among bivalves likely vary with environmental conditions. Juvenile mussels (Mytilus galloprovincialis) were collected from an intertidal population in Biscay, Spain (43°24′42,462″N02°56′43,659″W), in January 2007 and 2009. These mussels were maintained in the laboratory under either restrictive or optimal feeding conditions until fast- and slow-growing individuals on each maintenance regime could be identified. After fast- and slow-growing individuals were identified, the components of energy balance responsible for such growth rate differences were measured. The analysis of physiological traits indicates that under optimal food supply conditions, the capacity to ingest and absorb food and associated costs of growth are the main factors underlying growth rate differences. The set of physiological differences changed when size differentiation took place under restrictive food conditions. Higher rates of absorption coupled with reduced rates of metabolism accounted for faster growth in this case, especially under low food rations.

Fatty acid composition of the ovine longissimus dorsi muscle: effect of feed restriction in three breeds of different origin.

Muscle fatty acid profile reflects the body condition of animals and has a noticeable effect on meat quality. Herein, longissimus dorsi muscle of three different sheep breeds, Damara (a fat-tailed breed), Dorper and Australian Merino sheep, was analysed for fatty acid composition. The three breeds were subjected to two distinctive feeding levels (ad libitum and restricted feeding) over 42 days. The Damara sheep revealed several differences compared to the other two breeds, namely a higher concentration of polyunsaturated fatty acids, which can be related to being a fat-tailed breed. Even in restricted feeding conditions, this breed revealed the highest levels compared to Merino and Dorper sheep respectively, of linoleic acid (+31% and +28%), linolenic acid (+97% and +51%), eicosapentaenoic acid (EPA) (+65% and +37%), docosapentanenoic acid (DPA) (+31% Merino) and dodosahexanenoic acid (DHA) (+63% and +77%). EPA, DPA and DHA are three omega-3 fatty acids, with described beneficial characteristics. With this work we show other qualities (higher levels of the omega-3 fatty acids, EPA, DPA and DHA) of Damara meat that might present this breed as an interesting alternative for animal production in semi-arid climates.

CH4 and N2O emissions from China’s beef feedlots with ad libitum and restricted feeding in fall and spring seasons

Accurately quantifying methane (CH4) and nitrous oxide (N2O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N2O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH4 from the beef feedlot with an ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N2O emissions between two feeding strategies was observed. The two-season average CH4 emission rates of the two intensive feedlots were 230 and 198gCH4animal−1d−1 and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH4 conversion factor at the feedlot level. However, the average N2O emission rates (21.2g N2Oanimal−1d−1) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N2O emission rate and conversion factor of 9.2g N2Oanimal−1d−1 and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N2O emissions from beef feedlots. In addition, comparison indicated that China’s beef and dairy cattle in feedlots appeared to have similar CH4 conversion factors.

Disruption of running activity rhythm following restricted feeding in female mice: Preventive effects of antidepressants

Biological rhythms are critical in the etiology of mood disorders; therefore, effective mood disorder treatments should address rhythm disturbances. Among the variables synchronized with the light–dark cycle, spontaneous activity in rodents is useful for investigating circadian rhythms. However, previous studies have focused only on the increase of wheel-running activity under restricted feeding conditions, while little information is available on circadian rhythm of running activity. In this study, chronometrical analysis was used to assess whether circadian rhythms during wheel-running are altered by restricted feeding and affected by antidepressant drugs. Wheel revolutions were automatically recorded and analyzed using cosinor-rhythmometry in 8-week old ICR albino mice. When feeding was restricted to 1 h per day (21:00–22:00), wheel-running rhythms were reliably disrupted. Female mice exhibited marked alterations in the pattern and extent of wheel-running beginning on day 1. Subchronic treatment with imipramine or paroxetine, as well as tandospirone and (−)-DOI, prevented wheel-running rhythm disruption. Thus, altering the circadian activity rhythms of female mice on a 1-h feeding schedule may be useful for investigating disturbances in biological rhythms.

Geometric analysis of nutrient balancing in the mealworm beetle, Tenebrio molitor L. (Coleoptera: Tenebrionidae)

Geometric analysis of the nutritional regulatory responses was performed on an omnivorous mealworm beetle, Tenebrio molitor L. (Coleoptera: Tenebrionidae) to test whether this beetle had the capacity to balance the intake of protein and carbohydrate. We also identified the pattern of ingestive trade-off employed when the insect was forced to balance the costs of over- and under-ingesting macronutrients. When allowed to mix their diet from two nutritionally imbalanced but complementary foods (protein-biased food: p35:c7 or p28:c5.6; carbohydrate-biased food: p7:c35 or p5.6:c28), beetles of both sexes actively regulated their intake of protein and carbohydrate to a ratio of 1:1. When confined to one of seven nutritionally imbalanced foods (p0:c42, p7:c35, p14:c28, p21:c21, p28:c14, p35:c7 or p42:c0), beetles over-ingested the excessive nutrient from these foods to such an extent that all the points of protein–carbohydrate intake aligned linearly in the nutrient space, a pattern that is characteristic of generalist feeders and omnivores. Under the restricted feeding conditions, males ate more nutrients but were less efficient at retaining their body lipids than females. Body lipid content was higher on carbohydrate-rich foods and was positively correlated with starvation resistance. Our results are consistent with the prediction based on the nutritional heterogeneity hypothesis, which links the nutritional regulatory responses of insects to their diet breadth and feeding ecology.

Effects of chemical stress and food limitation on the energy reserves and growth of turbot, Scophthalmus maximus.

The objective of the present study is to examine the growth and energetic performance of juvenile turbot after exposure to contaminated sediment and during the subsequent recovery period with or without food limitation. We designed a two-step experiment by first exposing juvenile turbot to harbour sediment for 26 days and then transferring them to clean sea water with different frequencies of feeding for 35 days. Without food limitation, fish previously exposed to contaminated sediment compensated for weight, length and lipid reserve losses; we did not record any differences in size, Fulton's K condition index and triacylglycerol/sterol (TAG/ST) ratio after the 35-day depuration period compared to the reference fish. This result could be related to the compensatory growth mechanism observed in a wide range of fish species following a period of growth depression. With food limitation during the 35-day depuration period, recovery growth was not sufficient to restore length and weight values similar to the reference fish. Moreover, turbot previously exposed to contaminated sediment and subsequently fed twice or once a week exhibited extremely low TAG/ST ratios, but the reference fish submitted to the same restrictive feeding conditions did not. This study indicates that juvenile fish affected by chemical pollution can improve their biological performance if pollution events are followed by a period of abundant food. However, if pollution events occur during periods of food scarcity, e.g. in winter, storage of energy reserves will be compromised.

Photoperiodic responses of depression-like behavior, the brain serotonergic system, and peripheral metabolism in laboratory mice

Seasonal affective disorder (SAD) is characterized by depression during specific seasons, generally winter. The pathophysiological mechanisms underlying SAD remain elusive due to a limited number of animal models with high availability and validity. Here we show that laboratory C57BL/6J mice display photoperiodic changes in depression-like behavior and brain serotonin content. C57BL/6J mice maintained under short-day conditions, as compared to those under long-day conditions, demonstrated prolonged immobility times in the forced swimming test with lower brain levels of serotonin and its precursor l-tryptophan. Furthermore, photoperiod altered multiple parameters reflective of peripheral metabolism, including the ratio of plasma l-tryptophan to the sum of other large neutral amino acids that compete for transport across the blood-brain barrier, responses of circulating glucose and insulin to glucose load, sucrose intake under restricted feeding condition, and sensitivity of the brain serotonergic system to peripherally administered glucose. These data suggest that the mechanisms underlying SAD involve the brain-peripheral tissue network, and C57BL/6J mice can serve as a powerful tool for investigating the link between seasons and mood.

Effects of food limitation on 9 metal concentrations in liver and polycyclic aromatic hydrocarbon metabolites in bile of juvenile turbot (Scophthalmus maximus) previously exposed to contaminated sediments

A 2-step experimental design was employed in the present study on juvenile turbot (Scophthalmus maximus): 1) juveniles were exposed for 26 d to 2 contaminated sediments and a reference one, and 2) they were transferred in clean seawater with clean sediment for 35 d, feeding fish once a day, twice a week, or once a week. Fish exposed to contaminated sediments presented a significant increase of hepatic Cd, Cu, and Pb concentrations compared with the reference condition after the 26-d exposure. Higher fluorescence signals of polycyclic aromatic hydrocarbon (PAH) metabolites were found in bile from turbot exposed to contaminated sediments for 26 d compared with reference. These signals returned to values similar to reference fish after depuration whatever the food quantity. The metal bioaccumulation of Cd, Cu, and Pb was no longer observed after 35-d depuration with once-a-day feeding but was still found with restricted feeding conditions. Results on reference fish also showed significantly higher concentrations of most metals analyzed in fish fed twice a week and once a week compared with fish fed once a day. These results could be related to a decrease of fish hepatosomatic index with food limitation and, thus, a dilution effect on metal concentrations. The present study clearly demonstrates that changes in feeding status have significant effects on metal concentrations in fish and no observed effect on PAH metabolites.