植物黄酮在缓解奶牛热应激上的应用前景

奶牛是一种耐寒畏热的动物,当奶牛对环境温度的适应能力超过其阈值时就会产生热应激。热应激对奶牛的生产性能、抗氧化能力、免疫机制、内分泌和代谢产生不利影响,是阻碍奶牛业健康发展的一大问题。近年来,植物提取物作为一种兼具营养价值和保健价值的饲料添加剂被广泛应用。植物黄酮作为一种存在广泛的植物提取物,具有提高家畜生产性能和抗氧化能力、增强机体免疫力和抗炎能力、调节机体代谢等功效。因此,植物黄酮可以对症治疗奶牛热应激。本文将从热应激对奶牛生产性能、抗氧化能力、免疫机制、内分泌和代谢的影响以及近些年来将植物黄酮用于改善动物热应激的相关研究进行综述,以期为植物黄酮用于缓解奶牛热应激的深入研究提供理论支持。     

盐胁迫对星星草幼苗保护酶系统的影响

在盐胁迫下,星星草幼苗过氧化氢酶活性随着胁迫时间的延长而增强,并与盐浓度呈显著正相关。超氧化物歧化酶活性随着胁迫浓度的增强而增强,当超过一定浓度(3.0%Na₂CO₃)时则趋减弱,尔后随着胁迫时间的延长而增强。过氧化物酶活性的变化规律与超氧化物歧化酶活性相似,但变化幅度较小。丙二醛含量随着胁迫时间的延长和胁迫强度的增强而增加。     

低温胁迫对草地早熟禾抗性生理生化指标的影响

研究低温胁迫对草地早熟禾生理生化指标的影响。结果表明,在5℃下,超氧化物岐化酶(SOD)和过氧化氢酶(CAT)的活性随着胁迫时间的延长而增加,当4h时出现最大值,之后活性逐渐下降。当温度为0℃与-6℃时,两种酶的活性随着胁迫时间的延长而急剧下降,接近于零,温度越低,下降越快。叶绿素和类胡萝卜素含量随着肋迫时间的延长而下降,温度越低下降越快。5℃对脯氨酸含量无明显影响,在0℃与-6℃时,随着时间的延长,含量则明显增加。5℃和0℃低温胁迫对质膜相对透性无明显影响,-6℃时,质膜相对透性明显增大。供试指标对低温胁迫敏感性的顺序是:超氧化物岐化酶、过氧化氢酶>类胡萝卜素>脯氨酸>叶绿素>质膜相对透性。     

干旱预处理对一年生黑麦草耐盐性的影响

全球土壤盐渍化正在威胁着植物的生长发育,提高植物抗盐性已是当前亟待解决的问题。利用植物对逆境胁迫的交叉适应性是提高抗逆性的一种经济有效的方法,但关于干旱能否增强植物耐盐性的研究甚少。本试验以一年生黑麦草（Lolium multiflorum Lam.）为试验材料,对植物进行单一盐处理（NaCl）、经干旱预处理的盐处理（PEG-NaCl）,以及盐旱同时处理（PEG+NaCl）,比较相对含水量、叶绿素含量、丙二醛、钠离子及钾离子含量等生理指标。结果表明：盐胁迫使植物的钠离子含量显著增加,叶绿素含量及相对含水量降低;但经PEG处理后,相比于单一盐处理,叶绿素及钠离子分别有所增加及降低,其中,5% PEG的作用显著优于10% PEG处理;而盐旱同时发生则对植物造成了最大的伤害。因此,适宜强度的干旱预处理在一定程度上可减少盐胁迫对植物的伤害。     

松嫩草地羊草种子发育进程、休眠特性及与盐碱耐性关系的研究

羊草(Leymus chinensis)是禾本科赖草属根茎型优质禾草,不但营养价值高、适口性好,而且具有较强的耐旱、耐寒和耐盐碱性。羊草既是东北松嫩平原的优势种,也是干旱与半干旱地区建植人工草地的优良草种。近年来,随着畜牧业的发展及生态环境治理力度的加大,人工羊草草地不断建植,为此,人们对羊草种子的需求量与品质的要求也越来越高。本文通过研究羊草种子的发育进程、休眠特性及与盐碱耐性的关系,一方面明确羊草种子的最适宜收获时间,为农业生产上收获高品质羊草种子提供科学依据,另一方面挖掘羊草种子的发芽潜能、深入解析抗逆机理,为提高其利用率及抗逆新品种的选育提供理论基础。主要研究结果与结论如下:(1)通过对羊草种子发育动态的研究结果表明,羊草种子在发育过程中,随着成熟度的不断提高,种子的颜色由绿色变为浅绿色,再变成黄色,最后变为棕黑色。种子千粒重不断增加,在盛花后33 d达到最大值,之后趋于恒定。含水量与种子浸出液电导率则呈下降趋势,含水量在盛花后36 d达到最小值,而2个试验年份电导率值有所差异,分别在盛花后27和30 d达到最小值。标准发芽试验结果显示,羊草种子在盛花后39 d发芽率最高,此时种子的开始发芽时间、50%种子发芽时间、发芽势等指标均为最优。尽管加速老化试验的发芽指标与标准发芽试验略有差异,但是盛花后39 d的种子同样具有最强的抗老化能力。上述试验结果表明,盛花后39 d羊草种子活力最高,品质最佳,是种子最适宜的收获时间。 (2)不同成熟度的羊草种子对土壤埋深与盐碱胁迫具有不同的响应方式。羊草种子出苗与其后的幼苗生长能力随着种埋深度的增加而降低,1 cm是最适宜的播种深度,此时的出苗率最高、出苗时间最短,并且叶片与根系长度与生物量最大;另外不同成熟度的羊草种子表现出不同的出土成苗能力,盛花后39 d的羊草种子活力最大,其上述各项幼苗生长指标均为最优。种子的成熟度与盐、碱胁迫及其交互作用显著影响羊草种子的发芽率与发芽势,盛花后39 d的羊草种子在胁迫下具有最高的发芽率与发芽势,特别是在高浓度(400 mM)盐胁迫下,尤为明显。复萌试验结果显示,盛花后39 d的羊草种子在盐碱胁迫(特别是高盐环境)解除后同样具有最高的发芽率。上述结果表明,尽管不同成熟度的羊草种子均具有发芽能力,但是盛花后39 d的羊草种子出苗及抵御盐碱胁迫伤害的能力最强,这也进一步支撑了39 d是羊草种子适宜收获时间这一结论。另外羊草适宜浅播,1 cm是其最适宜的播种深度。 (3)通过人工手段处理可以明显打破羊草种子的休眠特性。研究结果表明,除了热水浸种处理外,其余方法如浓硫酸、冷层积、PEG,GA₃,KNO₃及清水浸种均能一定程度上提高羊草种子的发芽率,发芽速率、开始发芽时间及50%种子发芽时间。但是在生产实际中,既要考虑高效性也要考虑经济耗费,结合本试验的研究结果,我们推荐在生产中采用低温浸种20 d的方法来打破羊草种子的休眠,提高其发芽率。 (4)稃是抑制羊草种子萌发的重要因素,但同时也一定程度提高了种子的抗盐性。通过测定稃对羊草种子吸水、脱水、不同温度条件下的发芽响应以及不同持续时间盐胁迫对种子发芽的影响,结果发现稃可以显著提高羊草种子的吸水量,并同时减缓种子在干旱环境下的脱水速率,使种子不会过度脱水而死亡。稃、不同温度处理及两者交互作用显著降低羊草种子的发芽率与发芽速率,表明稃对羊草种子萌发具有一定的抑制作用。在不同持续时间的盐胁迫处理下,未萌发的带稃种子复萌率均高于去稃种子,特别是在长时间及高盐胁迫下尤为明显,表明稃对羊草种子耐盐性起着重要的调节作用,一旦雨水、融雪等条件降低了土壤盐浓度,带稃种子就可以继续萌发出土。 (5)20~30℃是羊草种子最适宜的发芽温度,高温、低温均显著降低种子的发芽率与发芽速率,并且此温度可一定程度上减缓盐胁迫与碱胁迫对种子发芽的抑制效应。随着盐、碱胁迫浓度的增加,羊草种子发芽率与发芽速率均呈下降趋势,且在碱胁迫下的下降幅度更大。在盐胁迫下,当盐浓度<200 mM时,低温是影响种子萌发的主要因素,随着盐浓度的不断增加,高温则更加剧了盐胁迫对种子萌发的抑制作用;而在碱胁迫下,即使碱浓度较低,高温与其交互作用也大大加剧了对种子发芽的抑制。盐胁迫下未萌发的羊草种复萌率随盐浓度增加而增加,而在碱胁迫下则随着碱浓度增加呈先上升后下降的趋势,高浓度碱胁迫使羊草种子失去活力而死亡,并且碱胁迫下种子的复萌率低于盐胁迫,25~35℃同样不利于种子的复萌。幼苗生长对温度与盐碱胁迫交互作用的响应方式与发芽阶段相似,20~30℃同样是最适宜温度;另外,盐碱胁迫均对羊草幼苗根生长的抑制作用更强。基于以上研究结果,我们建议在初夏(7月上旬),高降雨过后,温度与土壤条件适宜的情况下进行播种,以提高羊草种子的发芽率,更好的达到恢复退化草地的效果。 (6)在混合盐碱胁迫下,羊草种子的发芽率与发芽速率均随着盐浓度的增加不断下降,且碱性盐比例越大下降越明显。在250 mM盐浓度下,无碱性盐的A组处理发芽率为6.5%,而其余5组处理发芽率均为0。羊草幼苗生长阶段同样受盐浓度、pH及2者交互作用影响,并且根系对胁迫伤害更敏感,所受抑制作用更强。逐级回归分析结果表明,在种子萌发阶段,盐浓度是羊草种子在混合盐碱胁迫下能否萌发的决定性因素,而一旦胚根突破种皮进入幼苗生长阶段,pH就转变为主导因素。上述研究表明,混合盐碱胁迫对羊草种子萌发与早期幼苗生长阶段的抑制机理有所不同,其中高盐浓度与高pH的交互作用对种子萌发与幼苗生长的抑制效应最强。 (7)盐胁迫与碱胁迫均显著降低羊草幼苗的长度、鲜重与含水量,且碱胁迫抑制作用更强。2种胁迫均造成羊草幼苗Na⁺浓度与Na⁺/K⁺升高,并且K⁺浓度下降,但是在碱胁迫下,Na⁺ 浓度、Na⁺/K⁺上升幅度与K⁺下降幅度均大于盐胁迫。另外,在盐胁迫下,羊草幼苗大量积累Cl^-,有机酸含量变化不大;而在碱胁迫下,Cl^-,NO₃^-与H₂PO₄^-均呈下降趋势,而有机酸则大量积累,其中苹果酸、柠檬酸是主要的有机酸组分,可溶性糖是羊草幼苗在两种胁迫下共同的渗透调节物质。上述结果表明,碱胁迫由于具有高pH,对羊草早期幼苗生长的抑制作用更强,Cl^-与有机酸积累特征的差异表明羊草早期幼苗在盐胁迫与碱胁迫下具有不同的适应策略。     

Salivary testosterone measurements in growing pigs: validation of an automated chemiluminescent immunoassay and its possible use as an acute stress marker

This study aimed to validate the use of an automated chemiluminescent immunoassay analyser for salivary testosterone measurements in growing pigs and study how circadian pattern during daytime and stress can influence its values. The test method had intra- and inter-assay coefficient of variation lower than 10%. The method showed good linearity and recovery, and detection limits were low enough to detect salivary testosterone levels. No significant differences were observed in testosterone concentrations at different sampling time, and age and gender did not influence circadian pattern. In addition, this assay was used to quantify testosterone in two models of acute stress and, in both cases, significant increases (P < 0.01) in salivary testosterone were detected. Therefore, the automated assay system tested for porcine testosterone determinations would be suitable for its use in saliva samples and, furthermore, salivary testosterone levels could be used as a possible marker of acute stress in pigs.     

Relationship of climatic conditions to fecal corticosterone levels of captive cheetahs reared in Japan

To assess the stress level of cheetahs reared in Japan and to identify the prime components of the climatic conditions that affect their thermal stress, fecal corticosterone was monitored for 8 months from May to the following January. A total of 203 fecal samples were gathered in the morning from seven adult cheetahs that were kept at a zoological garden in Wakayama, Japan. Cheetahs were on exhibit singly or together with a harmonious conspecific during the day, but housed singly at night. Although the monthly fluctuation in corticosterone concentrations was not significant, the concentrations were relatively low during the summer season. Individual differences among cheetahs and the interaction effect between individual and month on the corticosterone concentrations were significant. Whereas the corticosterone concentrations negatively correlated with air temperature, they were positively correlated with the amount of rainfall. The highest air temperature and the amount of rainfall were extracted as the prime factors affecting corticosterone concentrations. These results suggest that cheetahs reared in Japan are somewhat subjected to thermal stress, particularly on cooler and/or rainy days.     

The oxidant/antioxidant equilibrium in horses

Since "free radical research" started in 1954, understanding the role of oxidants and antioxidants in physiological and pathological conditions has increased continuously. Oxidants are essentially generated by metabolic enzymes, inflammatory cells and mitochondrial electron leakage; they are indispensable for the cellular redox regulation and may, under certain conditions, have a pro-inflammatory stimulatory role. Endogenous and exogenous antioxidants counterbalance the oxidative processes and so maintain the oxidant/antioxidant equilibrium. Excessive oxidant generation or antioxidant insufficiency can lead to oxidative stress. The aims of this review are: (1) to provide an insight into the concept of the oxidant/antioxidant equilibrium by briefly introducing the oxidant and the antioxidant systems; (2) to describe how the oxidant/antioxidant equilibrium or oxidative stress can be evaluated in horses, and (3) to summarise current knowledge about oxidative stress in equine medicine and equine exercise physiology.     

Research on the Antioxident Function of Sulforaphane on the Leydig Cells of Cadmium Exposured Mice

The study was aimed to explore the antioxident function of sulforaphane (SFN) on the leydig cells of cadmium (Cd) exposured mice.Cd and SFN were added to the cell culture medium of TM3 cell, half inhibitory concentration (IC₅₀) of Cd and SFN safe dose range were determined.The tested model was set up,and the relative survival rate of TM3 cells, lactate dehydrogenase (LDH) activity and cell antioxidant levels were determined to study the antioxident function of SFN to cadmium exposured mice.The results showed that:①With the increase of Cd concentration,the relative survival rate of TM3 cells was decreased,and the IC₅₀ of Cd was 51.4 μmol/L;Within a certain concentration range,SFN could increased the cells survive rate,but there was toxicity when the SFN concentration was more than the scope,and the greater the concentration,the greater the toxicity. At experimental condition,SFN safety concentration were 2.5,5 and 10 μmol/L.②Compared with the control group,the GSH content,the T-SOD and GSH-Px activities in Cd group were significantly or extremely significantly decreased (P < 0.05;P < 0.01),and the LDH activity,the MDA content were increased.Additionally,the LDH activity and MDA content of SFN groups were decreased,while others three indexes were increased. Compared with Cd group,the GSH content,the T-SOD and GSH-Px activities of Cd+SFN groups were significantly or extremely significantly increased (P < 0.05;P < 0.01),however,the LDH activity,MDA content were decreased. The result indicated that SFN had the antagonism effect on toxicity of Cd in TM3 cell.