Effect of monensin on performance in growing ruminants reared under different environmental temperatures

To evaluate the effect of monensin on the performance of growing cattle under different environmental temperatures, 24 male calves (81.9 ± 7.7 kg mean weight and 100 days old) were distributed in a 2 × 2 factorial arrangement, contrasting 0 or 85 mg monensin/animal per day at 24.3 or 33.2 °C (environmental temperatures). Monensin supplementation increased weight gain (P=0.036), improved feed efficiency (P=0.040), increased ruminal concentrations of volatile fatty acids (VFA; P=0.003) and decreased the molar proportion of butyrate (P=0.034); all effects irrespective of environmental temperatures. A temperature-dependent monensin effect was detected on nitrogen retention (P=0.018) and N retained:N absorbed ratio (P=0.012). Animals fed monensin retained higher N amounts than those of the non-supplemented ones when the environmental temperature was 33.2 °C. Environmental temperature and monensin supplementation showed an interaction effect on urine N concentration (P=0.003). Temperature did not affect N excretion in monensin-fed animals, but increased N excretion in the non-supplemented ones. Monensin increased the crude protein (CP) digestibility (P=0.094) for animals at both temperatures. In conclusion, monensin changes the metabolism of the heat-stressed animals by increasing rumen VFA concentration, digestibility and protein retention, thus improving food use and weight gain.     

叶片淋洗对NaCl胁迫下玉米生长和矿质营养的影响

研究了叶片淋洗对NaCl胁迫下玉米生长和体内矿质营养含量的影响 .结果表明 ,无盐或低盐浓度下(0、5 0mmol·L-1) ,淋洗处理与对照的生物量没有差异 ,高盐浓度下 (10 0、2 0 0mmol·L-1) ,淋洗处理的生物量提高 ,pH3 .5淋洗液的淋洗效果好于 pH 7.0 .无盐胁迫时 ,淋洗处理的茎叶K含量高于对照 ,2 0 0mmol·L-1盐胁迫时则低于对照 ;在高盐胁迫时 ,淋洗处理的茎叶Na含量低于对照 ;无盐胁迫时 ,淋洗处理茎叶中Ca、Mg含量高于对照 .根系K、Na、Ca、Mg含量以及植株相对水分含量在淋洗和对照之间基本无明显差别 ,说明淋洗可以减轻中高度盐胁迫下玉米植株的受害程度 ,其原因与淋洗降低茎叶中Na含量有关 .     

Influence of varying sources of dietary electrolytes on the performance of broilers reared in a high temperature environment

Experiment using 297 broiler chicks, kept from 1 to 42 days under cyclic heat stress (minimum 29.3 °C and maximum 38 °C), was conducted to investigate the relative efficacies of three sodium (NaHCO₃, Na₂CO₃, Na₂SO₄), and potassium (KHCO₃, K₂CO₃, K₂SO₄) supplements at an identical dietary electrolyte balance (DEB) 250 mEq/kg and two chloride supplements (CaCl₂ and NH₄Cl) at DEB 50 mEq/kg. The desired levels of DEB were achieved by substitution of individual mineral supplement at the expense to builder's sand in the basal starter (DEB 185.6 mEq/kg) and finisher (DEB 174 mEq/kg) diet containing only salt as a source of Na and Cl. Each diet (one basal and eight experimental) was fed to three experimental units having 11 chicks each. The growth performances in K supplements, except KHCO₃, were poorer than those of Na supplements. The NaHCO₃, Na₂CO₃, Na₂SO₄ and NH₄Cl increased body weight gain, feed intake and improved feed to gain ratio than those of K₂CO₃ and K₂SO₄ after 42 days of age. These supplements also increased the water intake and resulted in lowered body temperature as well as reduced mortality. Very poor performance in CaCl₂ supplement was associated with disturbed calcium:phosphorus and very low blood pH (7.19). Better performance was noted with bicarbonate than that with carbonate and sulfate sources. The KHCO₃ accentuate the respiratory alkalosis by increasing blood HCO₃ contents (26.09 mmol/l) and gave poorer performance than NaHCO₃. Blood lymphocytes, hemoglobin, hematocrit and electrolyte balance in heat stressed broilers were better improved by NH₄Cl, NaHCO₃, Na₂CO₃, Na₂SO₄ and KHCO₃ than those of CaCl₂, K₂CO₃ and K₂SO₄ supplements. Present findings emphasized the importance of considering metabolisable anions supplemented in association with cations while balancing the dietary electrolyte equations. That is why DEB equation cannot be used to predict the relative benefits of different mineral supplements.     

Effect of air and soil temperature on water balance of jojoba growing under controlled conditions

Jojoba [ Simmondsia chinensis (Link) Schneider] cuttings were grown in pots under constant light intensity and vapour pressure deficit at wir temperatures of 18 and 27°C in climate-controlled cabinets. Leaf conductance and transpiration rate decreased exponentially as the xylen water potential (Ψ_x) decreased concurrently with the drying out of the soil. At high Ψ_x'leaf conductance and transpiration rate were much higher at the higher air temperature, and as Ψ_x declined both parameters decreased more rapidly at 27°C than at 18°C. When soil temperatures were decreased from 27 to 13°C, leaf water potential was not affected at either air temperatures, but transpiration rate was reduced. A linear negative correlation was found between transpiration rates and soil temperatures. It is suggested that the low soil temperature may restrict reducion of water flux in turn reduces stomatal conductance and transpiration without affecting the water potential in the shoot. The releavance of the response to changes in soil or air temperature to the performance of the plant in its semi-arid habitat is discussed.     

Heat stress is associated with disruption of ion balance in the migratory locust,Locusta migratoria

Thermal tolerance is important in determining the spatial and temporal distributions of insects but the mechanisms which determine upper thermal limits remain poorly understood. In terrestrial insects heat tolerance is unlikely to be limited by oxygen supply but in some arthropods, heat stress has been shown to cause haemolymph hyperkalaemia which is known to have detrimental effects on neuromuscular excitability. It is however unresolved if heat-induced hyperkalemia is the cause or the result of cellular heat injury. To address the putative role of heat-induced hyperkalemia we quantified changes in ion and water balance in haemolymph and muscle tissue of the migratory locust during exposure to two static temperatures clustered around the CT_max (48 °C and 50 °C). We show that heat stress caused a loss of ion balance and severe haemolymph hyperkalaemia which coincided with the onset of heat stupor. Locusts were able to maintain their haemolymph volume throughout exposure, suggesting it is unlikely that osmoregulatory failure is responsible for haemolymph hyperkalaemia. When locusts were allowed to recover from heat stupor, they recovered ion balance quickly but were still unable to function optimally after 24 h. The results therefore indicate that both the haemolymph hyperkalaemia and associated depression of muscular function (heat stupor) are secondary results of cellular heat injury and that the cause of heat stupor most be sought elsewhere.     

Effects of nickel supplementation on nutrient utilization,mineral balance,haematology and antioxidant status of crossbred dairy calves

BackgroundNickel has been identified as an important newer trace mineral playing essential role in animals however, its precise mechanism of action in the body is yet to be determined. Interaction of Ni with other essential minerals is suggested in reports limited to lab animals and needs to be explored further in large animals.AimThis study was conducted to study the influence of Ni supplementation at different levels, on minerals and health status of crossbred dairy calves.MethodTwenty-four Karan Fries crossbred (Tharparkar × Holstein Friesian) male dairy calves were selected based on body weight (137.09 ± 5.68) and age (10.78 ± 0.61) and were divided into 4 treatment groups (n = 6) given basal diet supplemented with 0 (Ni0), 5 (Ni5), 7.5 (Ni7.5) and 10 (Ni10) ppm Ni/kg of DM. Nickel was supplemented in the form of nickel sulphate hexahydrate (NiSO₄.6 H₂O) solution. To ensure the intake of the required amount of nickel by each animal, the calculated quantity of solution was mixed with 250 g concentrate mixture and offered individually to the calves. The calves were fed total mixed ration (TMR) consisting of green fodder, wheat straw and concentrate mixture in the ratio of 40:20:40 and the nutritional requirements were met according to NRC (2001) guidelines. Growth performance was recorded at fortnightly interval whereas, plasma minerals, haematology, antioxidant and immunity parameters were studied at monthly interval during the 150-day experimental period. Nutrient utilization and mineral balances were estimated with the help of a metabolism trial conducted at the end of feeding trial.ResultsSupplementation of Ni exhibited no influence on dry matter intake (DMI), body weight, average daily gain (ADG) and nutrient digestibility of dairy calves. However, the absorption and balance of minerals such as Ni, Fe, Cu, Zn and their respective plasma concentration increased (P < 0.05) with Ni supplementation and highest values were observed in calves fed 10 mg Ni/kg DM. The red blood cell (RBC) count, haemoglobin (Hb) concentration, haematocrit (HCT) and activity of superoxide dismutase (SOD) and catalase antioxidant enzymes showed highest increase (P < 0.05) in calves supplemented with Ni at level of 10 mg/kg DM as compared to other treatment groups. However, white blood cell (WBC) count, glutathione peroxidase (GPx), total antioxidant status (TAS), total immunoglobulins and IgG plasma concentration remained unaltered with addition of different levels of Ni in the diet of calves.ConclusionsThe supplementation of Ni at level of 10 mg/kg DM shows a positive effect on status of trace minerals such as Fe, Cu, Zn and improves the physiological conditions and health status of crossbred dairy calves indicated by improved haematology and antioxidant parameters.     

Paralysis and heart failure precede ion balance disruption in heat-stressed European green crabs

Acute exposure of ectotherms to critically high temperatures causes injury and death, and this mortality has been associated with a number of physiological perturbations including impaired oxygen transport, loss of ion and water homeostasis, and neuronal failure. It is difficult to discern which of these factors, if any, is the proximate cause of heat injury because, for example, loss of ion homeostasis can impair neuromuscular function (including cardiac function), and conversely impaired oxygen transport reduces ATP supply and can thus reduce ion transport capacity. In this study we investigated if heat stress causes a loss of ion homeostasis in marine crabs and examined if such loss is related to heart failure. We held crabs (Carcinus maenas) at temperatures just below their critical thermal maximum and measured extracellular (hemolymph) and intracellular (muscle) ion concentrations over time. Analysis of Arrhenius plots for heart rates during heating ramps revealed a breakpoint temperature below which heart rate increased with temperature, and above which heart rate declined until complete cardiac failure. As hypothesised, heat stress reduced the Nernst equilibrium potentials of both K⁺ and Na⁺, likely causing a depolarization of the membrane potential. To examine whether this loss of ion balance was likely to cause disruption of neuromuscular function, we exposed crabs to the same temperatures, but this time measured ion concentrations at the individual-specific times of complete paralysis (from which the crabs never recovered), and at the time of cardiac failure. Loss of ion balance was observed only after both paralysis and complete heart failure had occurred; indicating that the loss of neuromuscular function is not caused by a loss of ion homeostasis. Instead we suggest that the observed loss of ion balance may be linked to tissue damage related to heat death.     

不同温度下稻螟赤眼蜂在黏虫卵上的种群生命表

稻螟赤眼蜂Trichogramma japonicum Ashmead是水稻二化螟Chilo suppressalis(Walker)的优势卵寄生蜂。本文构建了以黏虫卵为中间寄主,稻螟赤眼蜂在20℃、25℃、30℃、33℃四个温度条件下的生命表。研究结果表明利用黏虫卵繁育稻螟赤眼蜂时,不同温度下其生长发育和繁殖均存在显著差异,雌蜂平均寿命随温度的升高呈下降趋势,在20℃条件下,雌蜂平均寿命为1.44 d,显著长于其它温度,当温度为30~33℃时,雌蜂寿命最短,平均为0.59 d。在温度为20℃和25℃时,稻螟赤眼蜂的羽化率显著高于温度较高的30℃和33℃,平均为94.73%。在25℃条件下,黏虫卵繁育的稻螟赤眼蜂的净生殖力(R 0)最大,达到31.9176,单雌寄生卵数最多,为32.88个,表现出最强的繁殖能力,而在30℃条件下,瞬时增长率r m和周限增长率λ达到最大值。综合生命表参数、单雌寄生黏虫卵数、寿命、羽化率等指标,利用黏虫卵工厂化繁殖稻螟赤眼蜂的最佳温度为25℃。本研究为利用黏虫卵大量繁殖稻螟赤眼蜂提供了有价值的参考。     

长白山阔叶红松林生长季热量平衡变化特征

根据长白山阔叶红松林2001年5月下旬至10月上旬微气象梯度观测资料和辐射、土壤热通量资料,用波文比-能量平衡方法(BREB方法)计算了森林的显热通量和感热通量,并计算了森林大气和植被体的储热量,分析了阔叶红松林热量平衡各项的日变化和季节变化,结果发现,热量平衡(净辐射)与太阳总辐射呈线性关系;热量平衡各项都与净辐射有相同的日变化特征,为昼正夜负的曲线．各项的绝对值一般表现为净辐射>潜热通量>感热通量>储热变化．受日照时间的影响,6～10月各分量正值的日持续时间逐渐缩短．月平均结果,白天净辐射6月份最大,10月上旬最小,变化于0～527W·m^-2,夜间的净辐射在0～-121W·m^-2．潜热通量白天和夜间分别在0～441、0～-81W·m^-2,感热通量昼夜分别在0～80、0～-26W·m^-2．储热变化则为0～44、0～-26W·m^-2．白天潜热通量占净辐射的比例8～10月逐渐下降,而感热通量和储热变化的比例9～10月明显上升,特别在严霜后2～3d,出现潜热通量比例突减、感热通量比例突增的现象．文中还对通量观测仪器、方法进行了简要分析．     

Effects of copper source and concentration on copper status and immune function in growing and finishing steers

Forty-eight individually fed purebred Angus steers (7±1.1 mo of age, 218±9.1 kg BW) were used to determine the effects of copper (Cu) source and concentration on Cu status and immune function. Steers were stratified by weight and initial liver Cu concentration and randomly assigned to one of five treatments. Treatments were: (1) control (no supplemental Cu), (2) 10 mg Cu/kg dry matter (DM) from Cu sulfate (CuSO₄), (3) 10 mg Cu/kg DM from a Cu-amino acid complex (Availa Cu; Zinpro Corporation, Eden Prairie, MN, USA), (4) 20 mg Cu/kg DM from CuSO₄, and (5) 20 mg Cu/kg DM from Availa Cu. Steers were housed in individual pens and fed an alfalfa-corn based growing diet (7.1 mg Cu/kg DM) for 56 d then gradually switched to a high concentrate diet (6.1 mg Cu/kg DM) for 144 d. On d 56 of the growing phase and d 112 of the finishing phase, liver Cu concentrations were higher (P<0.01) in Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P<0.01) liver Cu concentrations than steers receiving 10 mg Cu/kg DM. On d 112 of the finishing phase, steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P<0.01) liver Cu concentrations than steers supplemented 20 mg Cu/kg DM from CuSO₄. Cell mediated immune response to phytohemagglutinin was higher (P<0.01) in steers supplemented with 20 mg Cu/kg DM compared to steers supplemented with 10 mg Cu/kg DM. Total immunoglobulin (Ig) and immunoglobulin G (IgG) concentrations specific to pig red blood cells (PRBC) were higher (P<0.01) in steers supplemented with 10 mg Cu/kg DM from CuSO₄ than steers supplemented with 10 mg Cu/kg DM from Availa Cu. During the finishing phase, IgG concentrations specific to PRBC were higher (P<0.03) and antibody titers specific to ovalbumin (OVA) were lower (P<0.05) in control steers relative to Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P<0.02) antibody titers specific to OVA than steers receiving 10 mg Cu/kg DM. Steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P<0.01) antibody titers specific to OVA than steers supplemented with 20 mg Cu/kg DM from CuSO₄. Results indicate that the immune response to an antigen varies depending on the type of antigen administered as well as the concentration and source of Cu supplemented.     

干旱胁迫条件下冷型小麦灌浆结实期的农田热量平衡

冷型小麦具有代谢功能较好、活力较旺盛、抗早衰能力较强的特征,因而,培育出越来越多的冷型小麦并将其推向生产对于小麦的高产、稳产十分重要。在干旱频繁出现的今天,小麦生产受到了极大的影响,因而研究干旱胁迫下冷型小麦的农田热量平衡,对明了冷型小麦农田小气候的形成机理、改善农田小气候环境具有重要意义。通过对相关气象要素和小麦生态指标的测定,研究了干旱胁迫条件下冷型小麦灌浆结实期的农田热量平衡,揭示了冷型小麦对干旱胁迫的适应机制。结果表明:①冷型小麦农田净辐射较暖型小麦偏低16.35-47.57W/m²,但经统计检验,两者差异未达显著水平。②活动层内0.2m-2/3株高和2/3株高-冠顶冷型小麦的潜热通量较暖型小麦分别偏高29.09-48.61W/m²和47.41-134.89W/m²,湍流热通量分别偏低12.48-62.57W/m²和29.37-85.81W/m²;活动层与大气之间的潜热通量,冷型小麦较暖型小麦偏高50.30-124.20W/m²,湍流热通量偏低30.50-102.40W/m²。③冷型小麦的土壤热通量比暖型小麦偏低24.60-65.19W/m²。④冷型小麦加热植株体的热量Q_A +Q_T较暖型小麦偏低43.70W/m²。在干旱胁迫条件下,冷型小麦田的能量分配创造出了冷湿的小气候环境,有利于小麦的生长发育和产量的提高。     

盐分胁迫对啤酒大麦幼苗生长、离子平衡和根际pH变化的影响

盐分胁迫不仅影响植物的生长,而且会影响植物根际微域环境。根际pH的改变对土壤养分的有效性和微生物群落组成的变化有重要影响。为了探究啤酒大麦幼苗对不同类型盐分胁迫的生理生态响应机制和根际pH变化影响的生理机制,采用水培法,通过不同类型盐分(对照、混合Na盐、混合Cl盐和NaCl)胁迫处理啤酒大麦幼苗,对其生长、离子平衡和根际pH变化进行了研究。结果表明,1)在3种不同类型盐分胁迫下,啤酒大麦幼苗地上部干重、含水量均有所降低,而根冠比增加,尤其在NaCl胁迫下啤酒大麦幼苗地上部干重较对照显著降低了17.88%,而根干重和根冠比则分别增加了19.12%和43.86%。不同类型盐分胁迫抑制了啤酒大麦幼苗根长的生长,尤其在混合Na盐胁迫下根长降低明显(P0.05),但促进了根表面积和根体积的增加,尤其在混合Cl盐胁迫下,根表面积和根体积分别增加了41.76%和84.38%。2)不同类型盐分胁迫下啤酒大麦幼苗地上部离子平衡发生改变,在混合Na盐和NaCl胁迫下啤酒大麦幼苗主要吸收Na~+,地上部K~+/Na~+、Ca~(2+)/Na~+和Mg~(2+)/Na~+显著降低;混合Cl盐和NaCl胁迫下则过量吸收Cl~-,抑制了H_2PO_4~-、NO_3~-和SO_4~(2-)的吸收。3)在混合Na盐、混合Cl盐和NaCl盐分胁迫下,啤酒大麦幼苗对阴离子的吸收总量高于对阳离子的吸收总量,离子平衡计算结果表明根际呈碱化现象,与原位显色结果一致,且在混合Cl盐胁迫下根际碱化程度最大。     

Adequacy of food rations in soldiers during exercise in hot, day-time conditions assessed by doubly labelled water and energy balance methods

The energy requirements of people doing physical work in hot climates are not clearly understood. In particular, we know little about the combined effects of heat stress and muscular work on energy requirements. During military exercises in the African bush soldiers are supplied with standard rations, the adequacy of which is unknown. We have now assessed the adequacy of these food and water rations in 12 male Zimbabwean soldiers during 12 days of strenuous, heat-stress exercise in the field. We used two methods to measure energy expenditure: the double-labelled water method (DLW) and the energy balance method (i.e. comparing dietary energy with changes, if any, in body energy stores). Two groups were studied: one group (eight subjects) carried out field exercises; the control group consisted of four soldiers doing normal work. Mean daily energy expenditure as assessed by the DLW method was [mean (SE)] 23 (1.5) MJ · day⁻¹ for the field group and 14 (0.5) MJ · day⁻¹ for the control group (P<0.001). By the energy balance method, daily energy expenditure was calculated to be 26 (0.7) MJ · day⁻¹ and 15.5 (0.4) MJ · day⁻¹ for the field group and control group, respectively. Body mass loss was 3 (0.1) kg [4.6 (0.3)% of body mass] for the field group, but the control group gained 1.1 (0.1) kg. Mean daily fluid intake was 11 (0.5) 1 · day⁻¹, suggesting that the standard ration supplied was inadequate. Body mass loss was caused by both the energy deficit and total body water loss. These results suggest strenuous work in hot, dry field conditions imposes extra energy requirements. Accepted: 21 January 1997     

The effect of sodium balance on sweat sodium secretion and plasma aldosterone concentration

The effect of manipulating sodium intake upon sweat sodium secretion was investigated during heat acclimation. Twenty-five male subjects were confined to an environmental chamber at a temperature of 25°C for 3 days, and then acclimated to heat by a further 5 days at 40°C. The subjects' daily sodium intake was controlled throughout as follows: high (HNa), 348.4 (0.8) mmol · day⁻¹, n = 7; moderate (MNa), 174.1 (0.6) mmol · day⁻¹, n = 9; or low (LNa), 66.3 mmol · day⁻¹, n = 9. Sodium losses were estimated from urinary, faecal and sweat collections using a whole-body washdown method. Plasma aldosterone concentration was also measured from venous blood sampled each morning. Measurements of body temperature and heart rate during the heat exposure phase indicated a degree of heat acclimation. During this heat phase there was a reduction (P < 0.01) in sweat sodium secretion for all three conditions which was greatest for the LNa condition, although this finding was not significant (P < 0.1). In the LNa condition, plasma aldosterone concentration increased (P < 0.05) prior to heat exposure, and the secretion of aldosterone was potentiated (P < 0.01) during the heat exposure in comparison with the MNa condition. In contrast, the HNa diet produced a fall (P < 0.05) in plasma aldosterone concentration prior to heat exposure and an attenuation of aldosterone secretion thereafter. These findings are inconsistent with the hypothesis that retention of sweat sodium is dependent upon a net body sodium deficit, but demonstrate that aldosterone secretion is potentiated under such conditions. Accepted: 22 May 1988     

Conidiation under illumination enhances conidial tolerance of insect-pathogenic fungi to environmental stresses

Light is an important signal for fungi in the environment and induces many genes with roles in stress and virulence responses. Conidia of the entomopathogenic fungi Aschersonia aleyrodis, Beauveria bassiana, Cordyceps fumosorosea, Lecanicillium aphanocladii, Metarhizium anisopliae, Metarhizium brunneum, Metarhizium robertsii, Simplicillium lanosoniveum, Tolypocladium cylindrosporum, and Tolypocladium inflatum were produced on potato dextrose agar (PDA) medium under continuous white light, on PDA medium in the dark, or under nutritional stress (= Czapek medium without sucrose = MM) in the dark. The conidial tolerance of these species produced under these different conditions were evaluated in relation to heat stress, oxidative stress (menadione), osmotic stress (KCl), UV radiation, and genotoxic stress caused by 4-nitroquinoline 1-oxide (4-NQO). Several fungal species demonstrated greater stress tolerance when conidia were produced under white light than in the dark; for instance white light induced higher tolerance of A. aleyrodis to KCl and 4-NQO; B. bassiana to KCl and 4-NQO; C. fumosorosea to UV radiation; M. anisopliae to heat and menadione; M. brunneum to menadione, KCl, UV radiation, and 4-NQO; M. robertsii to heat, menadione, KCl, and UV radiation; and T. cylindrosporum to menadione and KCl. However, conidia of L. aphanocladii, S. lanosoniveum, and T. inflatum produced under white light exhibited similar tolerance as conidia produced in the dark. When conidia were produced on MM, a much stronger stress tolerance was found for B. bassiana to menadione, KCl, UV radiation, and 4-NQO; C. fumosorosea to KCl and 4-NQO; Metarhizium species to heat, menadione, KCl, and UV radiation; T. cylindrosporum to menadione and UV radiation; and T. inflatum to heat and UV radiation. Again, conidia of L. aphanocladii and S. lanosoniveum produced on MM had similar tolerance to conidia produced on PDA medium in the dark. Therefore, white light is an important factor that induces higher stress tolerance in some insect-pathogenic fungi, but growth in nutritional stress always provides in conidia with stronger stress tolerance than conidia produced under white light.     

黄河小浪底人工混交林生长季能量平衡特征

利用涡度相关系统和小气候梯度观测系统,对黄河小浪底人工混交林2012年生长季(5—9月)各能量通量进行了连续观测,分析了该生态系统能量平衡各项的变化特征,讨论了能量闭合状况。结果表明:潜热通量、感热通量和土壤热通量均与净辐射有类似的日变化特征。各项的绝对值大小表现为净辐射潜热通量感热通量土壤热通量。受日照时数的影响,5—9月能量平衡各项正值的日持续时间逐渐缩短。生长季,净辐射、感热通量和土壤热通量在6月份最大,最大值分别为418.5、231.4和12.5 MJ m-2month-1);潜热通量在7月份达到最大,最大值为320.8 MJ m-2month-1)。潜热通量、感热通量和土壤热通量占净辐射的比例分别在0.48—0.62、0.15—0.55、0.02—0.05之间。人工混交林生长季的能量分配主要以潜热通量和感热通量为主,且潜热通量为感热通量的2倍。波文比呈单峰曲线:6月最大,8月最小。黄河小浪底人工混交林生长季全天能量闭合度为79%。其中,白天闭合程度较高(81%),夜晚较低(41%)。本研究站点存在21%的能量不闭合。其原因可能与通量源区面积不匹配、忽略冠层热储存、湍流能的相位差等有关。     

Using a clustering algorithm to identify patterns of valve-gaping behaviour in mussels reared under different environmental conditions

Physiological adaptations for inhabiting transitional environments with strongly variable abiotic conditions can sometimes be displayed as behavioural shifts. A striking example might be found in bivalve species that inhabit estuaries characterised by fluctuations in environment. The opening and closing of their valves, so called gaping activity, represents behaviour that is required for two key physiological functions: food intake and respiration. Linking valve-gaping behaviour to environmental drivers can greatly improve our understanding and modelling of bivalve bioenergetics. Nowadays large data sets on gaping activity can be collected with automated sensors, but interpretation is difficult due to the large amount of environmental drivers and the intra-individual variability. This study aims to understand whether an unsupervised machine learning method (k-means clustering) can be used to identify patterns in gaping activity.Two commercially important congener mussels, Mytilus galloprovincialis and Mytilus edulis inhabiting two transitional coastal areas, the Venice Lagoon and the Wadden Sea, were fitted with sensors to monitor valve-gaping, while a comprehensive set of environmental parameters was also monitored. Data were analysed by applying three times a k-mean algorithm to the gaping time series. In the 1st analyses, the algorithm was applied to the overall gaping time series, including daily variations. We identified at both sites three clusters that were characterised by different average daily gaping aperture. The algorithm was subsequently reapplied to relate daily means of gaping to environmental conditions, being temperatures, oxygen saturation and chlorophyll levels. This 2nd analyses revealed that mean gaping aperture was mainly linked to food availability. A 3rd follow-up analysis aimed at exploring daily patterns. This third analysis again revealed consistent patterns amongst the two sites, where two clusters emerged that showed different degrees of oscillatory behaviour. There was however no obvious relationship between this fine scale oscillatory behaviours and environmental variables, but in the Venice Lagoon there was a site effect. Overall, we show that clustering algorithms can disentangle behavioural patterns within complex series of big data. The latter offers new opportunities to improve site-specific bioenergetic bivalve models by rephrasing the clearance and respiration terms based on the mean gaping aperture, provided that further laboratory experimentations are conducted to extrapolate parameters linking aperture with energy inputs and outputs.     

Dietary enzymatically-treated Artemisia annua L. supplementation could alleviate oxidative injury and improve reproductive performance of sows reared under high ambient temperature

The medicinal plant Artemisia annua L. is well known for its antimalarial compound artemisinin and the antioxidant capacity of its active ingredients. However, low bioavailability of Artemisia annua L. limits its therapeutic potential, fermentation of Artemisia annua L. can improve its bioavailability. This study was aimed to investigate the effects of dietary supplementation of enzymatically-treated Artemisia annua L. (EA) on reproductive performance, antioxidant status, milk composition of heat-stressed sows and intestinal barrier integrity of their preweaning offspring. 135 multiparous sows of average parity 4.65 (Landrace × large white) at day 85 of pregnancy were randomly distributed into 3 treatments. Sows in the control group were housed at control rooms (temperature: 27.12 ± 0.18 °C, temperature-humidity index (THI): 70.90 ± 0.80) and fed the basal diet. Sows in the HS, HS + EA groups were fed the basal diet supplemented with 0 or 1.0 g/kg EA respectively, and reared at heat stress rooms (temperature: 30.11 ± 0.16 °C, THI: 72.70 ± 0.60). Heat stress increased the malondialdehyde (MDA) content, reduced the activities of total antioxidant capacity (T-AOC) and total superoxide dismutase (T-SOD) of sows and piglets, and seriously compromised the antioxidant capacity of the sows and the intestinal integrity of their offspring. However, dietary supplementation of 1.0 g/kg EA reduced the MDA content, increased the activities of T-SOD and T-AOC in serum, colostrum, and milk of heat-stressed sows, and increased colostrum yield and 14-d milk fat content. EA supplementation also increased piglet weaning weight and the activities of T-SOD and T-AOC in serum. In addition, the abundances of intestinal tight junction proteins claudin-1 and occludin were up-regulated in piglets in EA-supplemented group. In conclusion, dietary EA supplementation at 1.0 g/kg can alleviate the oxidative stress in heat-stressed sows, improve the antioxidant capacity in both sows and their offspring, and promote the intestinal barrier integrity in their offspring. EA may be a potent dietary supplement that ameliorates oxidative stress in livestock production by improving the antioxidant capacity.     

Intrauterine growth restriction affects bone mineral density of the mandible and the condyle in growing rats

Objectives:To investigate in growing rats the effect of intrauterine growth restriction (IUGR) on the bone mineral density of the mandible and tibia, as well as the quality of the mandibular and condylar bone.Methods:Twelve male rats were born IUGR by mothers sustaining 50% food restriction during pregnancy. Twelve control male rats were born by mothers fed ad libitum. Dual-energy X-ray absorptiometry (DEXA) of the tibia, proximal tibial metaphysis and the mandible, biochemical markers, histology and histomorphometrical analysis on the mandibular and subchondral bone of the condyle were performed.Results:IUGR significantly affected bone mineral density (BMD) of both tibial and mandibular bones. IUGR rats had significantly lower osteocalcin values (p=0.021) and phosphorus (p=0.028), but not 25-OH vitamin D (p=0.352). Bone area percentage in the mandible was significantly lower (51.21±5.54) in IUGR compared to controls (66.00±15.49), and for subchondral bone of the condyle for IUGR (47.01±6.82) compared to controls (68.27±13.37). IUGR had a significant reduction in the fibrous layer, but not the proliferating layer, with the hypertrophic layer significantly increased.Conclusion:Maternal restricted nutrition during gestation can affect BMD of the mandible and the tibia of the offspring animals.     

Longitudinal gait development and variability of growing pigs reared on three different floor types

Biomechanical investigation into locomotor pathology in commercial pigs is lacking despite this being a major concern for the industry. Different floor types are used in modern, intensive pig production systems at different stages of the pigs’ production cycle. The general perception holds that slatted and/or hard solid concrete surfaces are inferior to soft straw-covered floors regarding healthy musculoskeletal development. Previous studies have compared pigs housed on different floor types using clinical, subjective assessment of leg weakness and lameness. However, reliability studies generally report a low repeatability of clinical lameness scoring. The objective of this study was to quantitatively assess the long-term effect of pen floors, reflected in the biomechanical gait characteristics and associated welfare of the pigs. A cohort of 24 pigs housed on one of three different floor types was followed from 37 to 90 kg average liveweight, with gait analysis (motion capture) starting at 63 kg. The three floor types were fully slatted concrete, partly slatted concrete and deep straw-bedded surfaces, all located within the same building. Pigs underwent five repeated camera-based motion captures, 7 to 10 days apart, during which 3D coordinate data of reflective skin markers attached to leg anatomical landmarks were collected. Pigs walked on the same solid concrete walkway during captures. One-way ANOVA and repeated measures ANOVA were used to analyse the gait data. Results revealed changes over time in the spatiotemporal gait pattern which were similar in magnitude and direction for the pigs from different floor types. Significant increases in elbow joint flexion with age were observed in all pigs (P⩽0.050; +6°). There were few differences between floor groups, except for the step-to-stride ratio in the hind legs being more irregular in pigs housed on partly slatted floors (P=0.012; 3.6 times higher s.d.) compared with those on 5 to 10 cm straw-bedding in all pen areas. As the level of clinical problems was generally low in this cohort, it may be that floors elicit problems only when there is a primary predisposing factor increasing weakness in susceptible tissues.