Interactions between leaf lifespan and defoliation frequency in temperate and tropical pastures: a review

In continuously stocked swards or pastures the frequency at which individual tillers and individual leaves are defoliated by ruminant livestock, relative to leaf lifespan of the grass species within the sward, determines the proportion of each leaf defoliated before senescence, and hence the efficiency of harvesting of herbage. In this paper, sets of data obtained in a range of climatic conditions and with a range of grass species are used in order to document this relationship. It is shown that the frequency of defoliation of individual tillers or individual leaves is closely linked to the average stocking density used within a period of time for maintaining a steady state sward or pasture height, herbage mass or leaf area index. Consequently, any decrease in herbage growth rate should lead to a decrease in the efficiency of harvesting of herbage and then to a more than proportional decrease in total herbage consumption by ruminant livestock. These effects will be more important for grass species having short leaf lifespan than for species with long lifespan. In rotational stocking, the link between herbage growth rate and frequency of defoliation of leaves can be broken by controlling the grazing interval, so any decrease in herbage growth would not be systematically associated with a decrease in efficiency of harvesting of herbage. Rotational stocking should be more efficient than continuous stocking in low herbage production conditions, while in high herbage production systems rotational and continuous stocking would have similar efficiency. The implications of these conclusions for the management of swards and pastures to meet different objectives are discussed briefly.     

Relationship of bite mass of cattle to sward structure of four temperate grasses in short‐term grazing sessions

The effect of sward structure of four temperate grass species on the bite mass of cattle was evaluated. Micro‐swards (79 cm × 47 cm; approximately the area of a feeding station) of orchardgrass (Dactylis glomerata L.), quackgrass [Elymus repens (L.) Gould], meadow fescue [Schedonorus pratensis (Huds.) P. Beauv] and reed canarygrass (Phalaris arundinacea L.) were offered to Holstein dairy cows in short‐term grazing sessions in 2006 and 2007 using a 4 × 4 Latin square design. Cows were allowed to take fifty bites in each session. Bite mass was calculated by dividing the adjusted change in weight of the micro‐sward by the number of bites. Sward surface height, bulk density and distribution of herbage dry matter (DM) in the canopy were measured pre‐ and post‐grazing. Sward structure differed among the grass species within years but bite mass (on a fresh or DM basis) was not affected. Higher surface heights and bulk densities in 2006 compared with 2007 (averaged across grass species) resulted in greater bite masses of DM in 2006. Values were 25·7 cm vs. 17·0 cm for surface height; 1219 g m^?3 vs. 926 g m^?3 for bulk density; and 1·05 g DM bite^?1 vs. 0·50 g DM bite^?1 for 2006 and 2007 respectively. Within the context of this study, differences between years in bite mass, associated with greater changes in sward structure, were more important than differences among grass species.     

Multi‐scale analysis of soil erosion dynamics in Kwazulu‐Natal,South Africa

For a case study area in the Okhombe catchment in the province of KwaZulu‐Natal, South Africa, a multi‐scale analysis of soil erosion dynamics was performed. At sub‐catchment level, the dynamics of erosional features were investigated by means of aerial photographs. At site level, the changes in soil physical and chemical properties were investigated by means of a fence‐line contrast study. Attention was paid to both surface and subsurface erosion phenomena. The number of erosional features in the study area in 2000 was not substantially different from the number of features in 1945. At sub‐catchment level, an increase in the number of gullies was observed from 1975 to 2000 but this followed a substantial inactivation of most erosional features from 1962 to 1975. Increases in erosional activity in 1962 compared to 1945 were mainly related to abandoned cultivated fields. At site level, a significant decrease in soil C/N ratio was observed within the fenced site within three years. For the same site, total carbon, saturated hydraulic conductivity and bulk density were not significantly different for the topsoil inside the fenced area compared with outside. Subsurface erosion phenomena mainly occur in the communal grazing areas and are mostly related to transitions between permeable and less permeable layers. The complex relationships between soil erosion, land use change and climate might further be understood by involving local people in the development, monitoring and evaluation of alternative types of land use, which is also likely to facilitate future steps in controlled grazing management. Copyright © 2005 John Wiley & Sons, Ltd.     

用荧光染色法研究山羊瘤胃原虫对细菌吞噬速率的初报

 【目的】采用荧光染色标记细菌（fluorescence labeled bacteria,FLB）技术,研究山羊瘤胃中原虫对细菌的吞噬速率。【方法】利用4只装有永久性瘤胃瘘管的徐淮山羊,采集瘤胃液以获取瘤胃原虫和细菌。试验设置清洗原虫祛除瘤胃自由细菌的荧光全标组（WFLB）及未清洗原虫保留瘤胃自由细菌荧光标记组（FLB）。【结果】WFLB组和FLB组的吞噬速率分别为398.4 cells/(cell•h)和230.4 cells/(cell•h),换算为细菌N为：2.15 pg N/(cell•h)/和1.24 pg N/(cell•h)。【结论】每天每头羊由原虫在瘤胃内循环中带出的细菌N损失在WFLB组和FLB组分别估计为103.2 mg N/(d•头)、59.5 mg N/(d•头),或者细菌蛋白损失为0.645 g/(d•头)和0.372 g/(d•头)。结果同时表明,荧光染色标记技术可以应用于瘤胃原虫对细菌吞噬速率的研究。     

优良热带牧草在云南元谋干热河谷区域试验研究

对15个热带优良牧草在云南元谋干热河谷进行区域试验研究。结果表明：参试的15个种质生长正常,生长季节产量高,耐热耐旱,是适应本区种植的优良牧草;牧草生物产量排在前3位的品种为杂交臂形草、热研8号坚尼草和热引19号坚尼草,产量分别是20.172、18.587和16.962t/hm2;15个种质生产性能排在前5位的依次为：研8号坚尼草、9号坚尼草、热研11号黑籽雀稗、9610雀稗、FSP2雀稗和10号狗尾草,它们品质优良,可在云南干热河谷区推广应用。     

Ground-dwelling beetle community in beech forests of Sado Island,Japan: comparison with the mainland

Island ecosystems differ from mainland ecosystems in their long-term isolation. On Sado Island, Japan, cattle grazing in the past gradually changed forests into grasslands, thereby altering the diversity of indigenous insects. We compared ground-dwelling beetle diversity on Sado Island to that on the nearby mainland. Contrary to previous reports, the island isolation effect resulted in lower γ and β diversity than on the mainland, because of the low species richness of beetles with low dispersal abilities. Few flightless beetles could invade Sado Island, even when the beech forests on the island were relatively adjacent to those on the mainland. Such a history of ecosystem formation could be the general pattern for continental-island mountain forests that were never connected to those of the mainland. We did not observe low α diversity of ground-dwelling beetles, suggesting that the cattle grazing history of the island has not changed environmental conditions for ground-dwelling beetles enough to reduce their diversity. In addition, cattle grazing increases the abundance of merdivorous insects by increasing the abundance of their food resource. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

不同品种公犊放牧补饲生长发育的研究

研究纯种的新疆褐牛、西门塔尔、安格斯和荷斯坦5～6月龄公犊在放牧条件下平均每日补饲1.5 kg精料的生长发育情况.10月龄时四个品种犊牛的体重分别187.86±22.35,198.60±41.74,212.60±35.96和233.66±21.62 kg.平均日增重为0.78±0.18,0.79±0.21,0.81±0.14和0.75±0.11 kg.屠宰率、净肉率和眼肌面积分别为48.36;、53.23;、51.56;和52.35;;34.40;、37.55;、42.10;和37.89;;32.62、78.56、62.67和58.98 cm2.放牧犊牛的生长发育随牧草和季节变化呈现出波动性,出现两个生长高峰(6～7月和10月)和一个平缓期(8～9月).     

反刍家畜反刍行为的观测研究

１９９６￣１９９８年在内蒙古锡盟多伦县和巴盟乌拉特后旗的天然草场上,测定了蒙古羊、蒙古牛和阿拉善双峰驼的反刍行为。试验采用一年四季２４ｈ跟踪观察的方法。试验结果表明,３种反刍家畜的反刍行为具有一定的规律性和差异。它畜的反刍行为受草场状况,饲养管理及气候变化的影响。     

夏季休牧对高寒矮嵩草草甸温室气体排放的影响

以高寒矮嵩草草甸为研究对象,利用密闭箱－气相色谱法,对夏季休牧8a的围栏草地(休牧草地)和全年放牧的草地(放牧草地)的温室气体排放通量、土壤特性和生物量进行了对比研究。结果表明：与放牧草地相比,休牧草地植被盖度较之高41％,单位面积生物量较之高53％。同时,土壤特性也有较大不同;休牧草地的植被－土壤系统CO₂排放通量比放牧草地低20.7％,测定期间两者CO₂排放通量以每天每公顷排放C的质量计分别为30.7和38.7 kg·(hm²·d)^-1;试验期间高寒矮嵩草草甸植被－土壤系统是大气CH₄的弱汇,休牧后草地土壤对CH₄的吸收能力增强,休牧和放牧草地CH₄的平均吸收强度分别为28.1和21.9 g·(hm²·d)^-1;休牧草地土壤N₂O排放通量比放牧草地低,两者排放通量分别为4.5和7.6 g·(hm²·d)^-1。可见,夏季休牧措施降低了草地对大气中温室气体浓度增加的贡献。     

额济纳旗宜牧土地载畜量研究

本次研究选用莫斯模型法(Moss)对额济纳旗宜牧土地生产力进行了研究,在此基础上估算出载畜量,为该旗的牧业可持续发展和生态环境保护提供理论依据。