牛磺胆酸对小鼠体内氧自由基的影响

为了研究牛磺胆酸(TCA)对小鼠体内氧自由基代谢的影响,采用黄嘌呤氧化酶法、二硫代二硝基苯甲酸法、紫外分光光度法、硫代巴比妥酸法和酶联免疫特异性测定法分别测定了给药后小鼠血浆、肝脏和脑组织中总超氧化物歧化酶(T-SOD)、谷胱甘肽过氧化物酶(GSH-PX)、过氧化氢酶(CAT)的活力、脂质过氧化产物丙二醛(MDA)的含量及血浆中一氧化氯合酶(NOS)的活力.结果显示,低剂量TCA能显著提高血浆、肝脏和脑组织中GSP-PX活力及肝脏和脑组织中CAT活力,显著降低血浆中GSH-PX活力和脑组织中GSH-PX活力.高剂量的TCA能显著提高血浆中GSH-PX、肝脏和脑组织中T-SOD、GSH-PX及肝脏中CAT活力.低、高剂量的TCA能显著降低血浆、肝脏和脑组织中MDA的含量,以及提高血浆中NOS活力.结果证明,TCA的抗氧自由基作用与其提高体内SOD、GSH-PX、CAT、NOS的活力和降低MDA含量有关.     

Effects of feeding and animal performance on nitrogen, phosphorus and potassium excretion by Holstein cows

Thirty‐four Holstein dry cows and 16 lactating cows were used in balance trials to identify the effects of feeding and animal performance on nitrogen (N), phosphorus (P) and potassium (K) excretion by dairy cows, and to develop prediction models for these excreta. Orchard grass silage, corn silage, alfalfa silage or timothy hay were offered to dry cows. Orchard grass silage or alfalfa silage, and concentrates were offered to lactating cows. In the statistical analysis, the independent variables were bodyweight (kg), dry matter (DM) intake (kg/day), milk yield (for lactating cows only, kg/day), water intake (free water plus water in feed, kg/day), intake (g/day) of N, P and K and dietary contents (% of DM) of crude protein, P and K. The dependent variables were N, P and K excretion (g/day) in feces and urine. In both dry and lactating cows, intake of N, P and K had large effects on corresponding excretion. The results indicated that a decrease in the intake of N, P and K could decrease the corresponding excretion. Further research by path analysis showed that K intake positively affected urinary N excretion in dry cows indirectly, through water intake and urine volume.     

The Content of Amino Acids in Pasture Vegetation and Their Apparent Digestibility in 2-year-old Horses

Ten samples of plant vegetation and 10 samples of fresh excrement were taken from the same pasture area. The excrement were collected from 10 2-year-old Old Kladruber horses that received the pasture vegetation daily. The apparent digestibility of nitrogen and amino acids in pasture vegetation was determined by using the acid-insoluble ash marker method. In comparison with excrement, the pasture vegetation contained higher levels of Ser, Ala, Leu, and His and higher levels of Pro (P ≤ .01), Met (P ≤ .01), and Arg (P ≤ .05). The mean level of Ile in pasture vegetation was lower than in excrement (P ≤ .05). The apparent digestibility of amino acids from pasture vegetation was high for Pro and Met (86.75 and 89.39%), moderate for Ser, Ala, Leu, His, and Arg (68.61%-76%), and low for Asp, Thr, Glu, Gly, Val, Leu, Tyr, Phe, and Lys (56.15%-66.03%). The digestibility of lysine and Ile was relatively low (56.39% and 56.15%, respectively). The total content of nitrogen per dry matter was 10.98 ± 2.46 g/kg for pasture vegetation and 12.12 ± 2.38 g/kg for excrement, whereas the content of protein nitrogen was 7.20 ± 0.25 g/kg and 6.89 ± 0.21 g/kg of dry matter in pasture vegetation and excrement, respectively. This means that only 65.55% and 56.90% of N is bound in proteins in pasture vegetation and excrement, respectively. Non-protein nitrogen accounts for 34.45% in pasture vegetation and for 43.10% in excrement.     

鱼类对饲料中糖的利用研究进展

糖类是鱼类饲料中廉价的能量源,然而,与陆生动物相比,鱼类对饲料中糖的利用能力较低。本文综述了这方面的最新研究进展,包括鱼类对饲料糖的利用能力与鱼饲料中糖的适宜含量、影响因素及鱼类的糖代谢机制。     

AMPK对动物营养代谢的调节作用

AMPK是一种能被腺苷一磷酸(AMP)激活的蛋白激酶。该酶的作用底物包括β—羟基—β甲基—戊二酸单酰CoA还原酶(HMGR) ,乙酰辅酶A羧化酶(ACC) ,激素敏感脂酶(HSL) ,糖原合成酶。当细胞能量被耗竭、腺苷一磷酸/腺苷三磷酸比(AMP/ATP)增加时 ,AMPK被活化 ,继而通过调节上述底物酶而改变脂类和碳水化合物代谢 ,使其朝着抑制ATP消耗过程、促进ATP生成反应的方向进行 ,从而使细胞能量得到迅速恢复。AMPK的这种“燃料开关“作用在动物抵御和适应环境应激的过程中起着重要作用。AMPK可能参与家畜应激营养代谢及营养代谢疾病的调节     

克伦特罗对绵羊肝脏血流量和氮代谢的影响

在4头门静脉、肝静脉、肠系膜静脉和股动脉上安装血管导管的绵羊中研究了克伦特罗（CL,0.8 mg/kgBW,肠系膜静脉给药,每天2次,连续5 d）对其肝脏生长代谢的影响。结果表明:CL对肝脏血流量影响较小。而在CL作用下绵羊血浆中尿素氮水平明显下降,肝静脉和门静脉血液尿素氮流量分别减少16.86％（P<0.01）和15.51％（P<0.05）。肝静脉多肽流量在CL处理期也较对照期下降38.71％（P<0.01）,门静脉处多肽水平处理期则与对照期相当。克伦特罗还增加绵羊肝脏IGF-I的合成和分泌,门静脉和肝静脉中的增加幅度分别为38.84％（P<0.01）和33.18％（P<0.01）。提示CL可通过增强对绵羊肝脏氮的储留及肝脏IGF-I的合成和分泌从而促进机体的生长代谢。     

临界氮浓度稀释模型在牧草种子生产中的应用前景

氮素是影响牧草种子产量的关键因素,氮素对于植株分蘖、干物质生产、花序形成、产量组分动态变化等均具有影响.文章主要从临界氮浓度稀释模型的概念、构建方法、研究现状、应用等方面进行了综述,提出临界氮浓度稀释模型在实际生产中应用时存在的问题,并对其在牧草种子生产中的应用前景进行了展望.     

猪粪干、湿法厌氧发酵过程中碳、氮的流失

试验以新鲜猪粪为发酵原料,研究湿法和干法两种不同厌氧发酵过程的碳、氮排放量。湿发酵和干发酵组发酵料液的总固体(TS)含量分别为8%和20%,发酵液pH为6.8~7.4,发酵温度为35℃,体积为1.2 L,周期为21 d。试验期间每天测产气量,每4天取发酵样,测其全氮含量和TS降解率。结果表明,湿法和干法发酵组的CH4总产气量分别为9114 mL和12537 mL;CO2的总产气量分别为251.90 mmol和343.67 mmol;TS降解率分别为52.5%和29%。湿发酵的碳流失率和全氮流失率极显著高于干发酵(P<0.05)。     

尕海湿地区沼泽草甸退化对土壤氮转化酶活性的影响

为探讨高寒湿地退化对土壤氮转化酶活性的影响,以青藏高原东缘尕海湿地未退化（ND）、轻度退化（LD）、中度退化（MD）和重度退化（HD）4种不同退化程度0~40 cm土层沼泽草甸为研究对象,研究不同退化与土层中土壤氮转化酶（蛋白酶、脲酶、硝酸还原酶和亚硝酸还原酶）活性的变化特征及其与土壤理化性质之间的关系。结果表明：1）随沼泽草甸退化程度加剧,土壤含水量、全氮、铵态氮和微生物生物量氮含量均显著降低,土壤温度与硝态氮含量却显著增加。2）随退化程度加剧,各土层土壤脲酶活性增加、蛋白酶活性降低,且仅在20~40 cm土层存在显著差异;硝酸还原酶活性增加、亚硝酸还原酶活性降低,在0~20 cm土层存在显著差异。3）各退化程度中,土壤脲酶、蛋白酶、亚硝酸还原酶活性均随土层深度的增加而显著下降,硝酸还原酶活性仅在HD显著下降。4）退化程度和土层对4种土壤氮转化酶活性均存在显著影响,且对土壤硝酸酶和亚硝酸还原酶活性存在显著交互作用。5）冗余分析表明土壤含水量对土壤氮转化酶活性变化的贡献率高达67.1%,其是驱动尕海沼泽草甸退化演替过程中土壤氮转化酶活性变化的主导因素。研究结果可为高寒湿地生态系统退化中的土壤酶活性变化规律提供理论依据。     

双峰驼水代谢与血液中无机离子浓度的动态关系

对双峰驼禁水１５ｄ，于禁水前、后及暴饮后采血，测定其血液中多种无机离子的浓度变化。结果表明，全血碳酸氢盐含量在禁水期变化极显著，与禁水前相比，冬季试验升高２８．０９％，夏季试验升高２６．５９％；暴饮后快速下降，冬、夏季试验分别比禁水前低９．５％和７．８％，４ｄ后恢复正常。血清中Ｋ＋和Ｆｅ２＋含量未见统计学差异。血清中Ｎａ＋、Ｃｌ－、Ｃａ２＋、Ｍｇ２＋、和Ｐ３＋的含量于禁水期逐渐上升，暴饮后快速下降，其变化均有显著差异，其中Ｎａ＋的正常值显著高于其他反刍动物。结果表明，双峰驼在禁水期具有较高的血液渗透压和碱储量，其对保证缺水时血液酸碱平衡的调节，维持血容量，保证机体正常水代谢功能具有重要作用，是骆驼耐干渴的重要原因之一。