高精料日粮饲喂诱导泌乳奶牛发生乳脂抑制的机制

高精料饲喂导致奶牛乳脂率降低的相关机制目前还不清楚.本研究通过探究高精料饲喂对肝脏内乳脂前体代谢的影响,揭示奶牛(Bos taurus)发生乳脂抑制的相关机制,将10头泌乳期(25+5)d荷斯坦奶牛随机分为2组,分别饲喂精粗比4∶6(对照组)和6∶4(实验组)日粮.饲喂20周后实施肝脏血管瘘手术,护理4周,进行如下实验:1)统计奶牛产奶量,每周测定乳成分;2)采集空腹进出肝脏血液,检测甘油三酯(triglyceride,TAG)和游离脂肪酸(free fatty acid,FFA)的含量;3)活体穿刺取肝脏组织,qRT-PCR检测肝脏中脂代谢相关基因的表达.结果表明,高精料饲喂6～l8周可提高产奶量,18周后乳脂率显著降低(P＜0.05).高精料组奶牛肝脏TAG和FFA的净输出含量显著(P＜0.05)或极显著降低(P＜0.01);肝脏中参与脂肪酸合成代谢的固醇调节元件结合蛋白-lc基因(sterol regulating element binding protein-1 c,SREBP-1c)、乙酰辅酶A羧化酶基因(acetyl-coa carboxylase,ACC)和脂肪酸合成酶基因(fatty acid synthetase,FAS)表达显著(P＜0.05)或极显著(P＜0.01)下调;参与脂肪酸分解代谢的过氧化物酶体增殖物激活受体α基因(peroxisome proliferators-activated receptor α,PPARα)和肉毒碱棕榈酰转移酶-1基因(carnitine palmitoyltransterase-1,CPT-1)表达显著上调(P＜0.05).高精料饲喂导致奶牛肝脏脂肪酸合成代谢减弱而分解代谢增强,肝脏内乳脂前体物发生重分配,乳脂前体物输出减少,影响了乳脂合成.本研究揭示了高精料饲喂导致奶牛乳脂率降低的机制,为改善奶牛乳脂率提供了理论基础.     

滇东南喀斯特地区植被覆盖变化及其影响因素

利用MODIS NDVI数据资料集、标准气象站点的气候数据及社会经济统计数据,辅以叠置分析、空间统计分析和相关分析等方法,探讨了滇东南喀斯特地区植被覆盖的时空变化特征及其与气候因子、人类活动的关系。结果表明:滇东南喀斯特地区植被4月上旬进入生长季而9月中旬结束,2001—2010年植被覆盖呈现出上升的趋势,NDVI增加速率为0.03/10 a;滇东南喀斯特地区植被覆盖呈增加和减少趋势的面积分别占总面积的70.03%和29.97%,植被NDVI减少最为突出的区域主要集中在人口聚集的城镇周围及河流沿线,而增加的区域主要集中在高海拔山区;气候影响因素中的水分类因素即平均相对湿度、最小相对湿度和降水是滇东南喀斯特地区植被NDVI年内变化主要的影响因素,其影响有2个月左右的滞后期,温度类气候因子的滞后期为3个月左右,其他类型的气候因子滞后期约为2个月;滇东南喀斯特地区实施的退耕还林工程,极大地提升了植被覆盖度,而城镇化过程则使得城镇周边的极低、低植被覆盖度区面积增加。     

不同开垦时间对喀斯特石漠化地区土壤养分的影响

[目的]为喀斯特生态系统的恢复重建、农业生产以及相关政策制定提供参考。[方法]采集贵州普定典型喀斯特山区3个不同开垦时间(1959、1968、1980年)的0~10、10~20、20~40 cm土层的土壤样品,进行室内理化分析。[结果]结果显示,普定县喀斯特山区随着农业用地开垦时间的增加,土壤养分变化总体表现为有机质、全氮、CEC下降;土壤pH值下降;全磷、全钾含量没有明显变化;碱解氮、有效磷、有效钾等有不同的变化规律。[结论]普定县喀斯特山区土壤养分随开垦时间的变化主要是受到施肥和微地形的影响。     

Microbial biomass and activity along a natural pH gradient in forest soils in a karst region of the upper Yangtze River,China

Mountain closure, considered an effective and economic measure for natural restoration of degraded forest ecosystems, has been widely carried out in the karst region of southwest China. The aim of this study was to evaluate microbial aspects of soil quality after mountain closure by analyzing soil microbial biomass, basal respiration, metabolic quotient, and relationships with basic chemical properties in Guizhou Province, a karst region of the upper Yangtze River. Soil quality was considered poor from the low levels of microbial biomass carbon (MBC), nitrogen (MBN), and microbial quotient (MBC/total C and MBN/total N), but high metabolic quotient (qCO₂). Soil pH, showing marked variation from 4.1 to 7.9 in this karst region, was proved to significantly affect soil microbial biomass and activity. Soil microbial biomass, microbial quotient, and soil basal respiration declined significantly with decreasing soil pH, while qCO₂ showed an apparently increasing, but not statistically significant, trend. The changes in microbial biomass and activity following the change in soil pH could possibly be because of a change in soil microbial composition, and more detailed research is necessary. Compared with soil pH, soil organic matter content was another, more important, factor that directly restricted microbial growth because of the serious loss as a result of disturbance. As a practical application based on microbial aspects, introduction of some N-fixing tree species may be an active and effective measure to improve soil fertility and thus to accelerate restoration of the forest ecosystem in the karst region.     

茂兰喀斯特漏斗森林群落结构研究

通过设样地调查,对茂兰喀斯特漏斗森林进行群落结构研究.森林群落内共有维管植物61科116属153种,其中蕨类植物7科10属11种.常绿树种占群落全部植物的50%~65.38%.乔木层中,乔木的个体/种水平均低,优势种不明显;小径级树木分布数量大,群落结构稳定.茂兰喀斯特漏斗森林在植物区系上表现出明显的热带性.     

文山州石漠化状况及成因分析

文山州石漠化面积10017．3km^2,占全州岩溶面积的59．65％,占国土面积的31．07％．目前石漠化已经成为制约文山州经济社会可持续发展最严重的生态地质环境问题,主要危害是：土地退化,环境污染日益严重;土地生态功能下降;加剧区域农民贫困．文山州石漠化的形成是由于岩溶地区地质环境脆弱,在不合理的人类活动和自然因素作用下,一些地区植被退化乃至消亡,导致水土严重流失,最终形成了连片分布的裸露石漠．     

Assessment of the reproductive system of Isatis tinctoria L.

Isatis tinctoria L. (woad) is a dye plant whose cultivation is increasing because of its adaptability to marginal conditions and increasing demand for natural products. Suitable breeding schemes need to be set up in order to obtain woad varieties for each proposed environment. Presently, no data about the reproductive system are available. The effects of selfing and crossing on setting and progeny vigour were assessed. Results showed the existence of an outcrossing system in I. tinctoria. Obligate self-pollinated plants produced fewer siliques (7.1 g per plant) with lower weight (6.0 mg) and lower seed germinability (8.2%) than outcrossing plants (44.1 g, 8.0 mg and 46.0% for each character, respectively). Self-pollinated progenies also generally showed lower vigour than outcrossing progenies.     

灌浆期谷子净光合速率日变化及相关影响因子的研究

运用美国LI-COR公司制造的LI-6400便携式光合测定系统,研究了谷子灌浆期的净光合速率(Pn)日变化。结果表明:叶片净光合速率(Pn)日变化呈双峰型,有明显的光合午睡现象。     

黎塘岩溶区铁锰结核背景下的土壤研究

对黎塘岩溶区铁锰结核背景下的土壤进行了分析。结果表明：研究区土壤以硅质土为主,土壤发育呈幼年性。土壤多呈中性,对土壤肥力的发挥及旱地作物的生长较为有利;有机质含量A层多为中等（Ⅲ级）或丰富（Ⅳ级）,B层为缺乏（Ⅱ级）;全N含量A层多为中等（Ⅲ级）,B层多为缺乏（Ⅱ级）,有效N含量A层多为丰富（Ⅳ级）或甚丰富（V级）,B层多为中等（Ⅲ级）或缺乏（Ⅱ级）,A、B层养分含量的差异说明农耕区土壤受表层耕作、施肥影响较为显著。土壤有效P整体表现为缺乏或甚缺乏,可能已成为旱地作物生长的主要限制因子,阳离子交换量多表现为保肥力中等。     

铜仁市农业生态环境的脆弱性及可持续发展

铜仁市地处喀斯特地貌山区,农业生态环境极为脆弱,给农业可持续发展带来很多不利影响。铜仁市农业生态环境脆弱性是喀斯特自然作用和人为活动作用的结果,据此阐述其环境整治和农业可持续发展的途径及相应的发展模式。