The response of eragrostis curvula (schrad.) nees to fertilizers in the highland sourveld of natal*

The effects of five years of application of N, P and K fertilizers at three levels, and of agricultural lime at two levels, on the herbage yield of Eragrostis curvula are discussed. The experiment was carried out on leached soils under an average annual rainfall of 900mm. Significant responses in yield were obtained to N, P and K fertilizers but there was no response to lime.     

Disturbance and the frequency of root suckering in an invasive savanna shrub,Dichrostachys cinerea

The ecology of clonal species has rarely been studied in savannas. Dichrostachys cinerea, a common invasive shrub in southern African savannas, forms root suckers. This paper examines the effect of disturbance type and frequency on this form of clonal spread. Small plants were excavated (n = 370) at 11 sites exposed to different fire frequencies and grazing intensities and classified were as either seedlings or root suckers. Most of the plants (55%) were found to be root suckers. There was no significant effect of disturbance type and frequency on 'seedling' establishment from seeds versus root suckers. Even when burnt annually, D. cinerea continued to form root suckers. The combination of establishment from seeds and spread by root suckers makes this species a formidable native invasive woody shrub.     

The effect of prolonged heavy grazing pressure on the regrowth of two perennial grass species in a semi-arid communal rangeland

We tested the hypothesis that initial above-ground regrowth of defoliated grass tufts would be reduced in sites which have been exposed to prolonged heavy grazing. The regrowth of Themeda triandra and Urochloa mosambicensis tufts was compared between three heavily grazed sites close to a village and three relatively lightly grazed sites far from a village, in a semi-arid communal rangeland in the South African lowveld. A clipping experiment was done in the field using T. triandra and U. mosambicensis tufts. Regrowth was lower (P≤0.01) in the heavy grazing sites for both species. This was more a function of tiller production rate, in terms of numbers of tillers, than of tiller extension rate. Rate of regrowth was not strongly affected by tuft size.     

The effects of topo-edaphic variables and cultivation on the woody vegetation of Weenen Nature Reserve,KwaZulu-Natal

The soil types and woody vegetation of Weenen Nature Reserve (WNR), KwaZulu-Natal, were described. Mispah, overlying shale, and Shortlands, overlying dolerite were the most common of 18 the soil forms encountered. Six vegetation types were identified by TWINS PAN which differed in slope, aspect, land-use history, species richness and tree density. Vegetation types ranged from species-rich, dense 'Coddia rudis-Dombeya cymosa Closed Woodland' overlying dolerite and occurring on steep north-east facing slopes that had never been cultivated, to previously cultivated, species-poor 'Acacia sieberiana Open Woodland' on flat topography, overlying shale. Ordination analyses further described the main associated floristic-environmental gradient from steep slopes supporting a high diversity of broad leaved species through to species-poor, flatter areas with an abundance of microphyllous plants. A second main gradient described was from uncultivated sites on steep slopes of usually dolerite-derived soils through to flat, previously cultivated land on shallow soils overlying shale. Topo-edaphic variables and previous cultivation, which were confounded, were therefore the main determinants of floristic variation in WNR, whereas fire had no influence. Half of the dominant woody species exhibited a reverse-J size structure, indicating relatively constant population change. A number of species had a preponderance of individuals in the smallest (0.5–1.5m height) size class, owing possibly to recruitment during the exceptional wet season of 1995/6, and/or the inability of individuals to escape the 'fire-trap'. Several, mostly Acacia, species appear to have recruited intermittently. The vegetation changes of this system will have an affect on browse availability. The woody vegetation of WNR appears to be changing in response to successional processes and management influences.     

中国绿孔雀濒危现状及其保护

绿孔雀曾广布于中国南方多个省份,包括湖南、湖北、四川、广东、广西及云南等省区,现仅分布于云南局部地区,其种群数量不断减少,种群逐渐分散、衰退,根据最新调查结果显示,中国现存野生绿孔雀数量仅剩约235～280只,已被云南省列为极危(CR)物种。绿孔雀数量及分布区急剧缩减的原因主要包括人类的干扰和猎杀、栖息地侵占,破坏和斑块化等因素。科研人员及保护工作者在保护区的建设、绿孔雀人工繁育等方面保护绿孔雀野生种群,扩大人工种群。目前,涉及绿孔雀保护工作的保护区达十余个,已全面覆盖绿孔雀栖息地。本文概述了绿孔雀的形态、生态习性、繁殖行为、亚种分化及地理分布等生物学特征,分析绿孔雀濒危现状及致危因素,整合目前立法保护、就地保护、易地保护等保护措施,为将来的保护及科研工作提出了建议和展望。     

The performance of tropical pastures in the drier phase of the Highland sourveld of Natal

Abstract

Several tropical grasses (Acroceras macrum, Cenchrus ciliaris, Cyndon sp., Digitaria sp. and Pennisetum clandestinum) and legumes (Desmodium uncinatum and Lotononis bainesii) were evaluated at the Kokstad Research Station (Bioclimatic sub‐region 4f of Natal) over a period of seven years. The experiment was repeated on two soil types, a deep Doveton and a shallow Newport/Mispah transition. The yield data were subjected to a multiple regression analysis to assess the influence on yield of factors such as age of pasture, soil type, cutting frequency, N level, rainfall and temperature. The regression models are given and their implications discussed. Seasonal distribution curves using the Richard's function were developed for all species.     

The effect of defoliation and competition on the regrowth of Themeda triandra and Aristida junciformis subsp. junciformis

Abstract

The effects of a cutting trial, conducted to study the combined influence of defoliation and competition from surrounding vegetation on the vigour of Themeda triandra and Aristida junciformis, were evident after the single season of treatment implementation. Aristida junciformis was more sensitive to defoliation than T. triandra, whereas competition reduced yield to a greater extent in T. triandra than in A. junciformis. The two species differed in their ability to tolerate defoliation under competition. Defoliation reduced the yield of A. junciformis, at all levels of competition, to a greater extent than T. triandra. Aristida junciformis was particularly sensitive to a combination of severe defoliation and full competition. It is suggested that manipulation of grazing patterns may shift the competitive balance between palatable (e.g. T. triandra) and unpalatable (e.g. A. junciformis) components of the sward.     

The effects of continuous and rotational grazing of sourveld on the quality of herbage selected by Simmentaler heifers

A grazing trial was conducted at the Kokstad Agricultural Station to compare the dry matter digestibility (DMD) and crude protein content (CP) of diets selected by four fistulated cattle which were continuously and rotationally grazing sourveld. Two stocking rates of 1,0 and 2,3 animals/ha (0,5 and 1,2 LSU/ha) were applied under each grazing method. The mean DMD and CP values of diets selected in the continuous and rotational grazing treatments, respectively, were: DMD=64,3%, 62,3%; CP=6,63%, 6,88%. The effect of stocking rate on the quality of the diet selected varied between the two grazing methods. DMD and CP of diets selected under rotational grazing decreased with time during the week‐long period of stay in each paddock. On average, DMD and CP values on the first and sixth day respectively, were: DMD=66,6%, 60,5%; CP=8,37%, 6,01%. These differences were more pronounced at the higher than at the lower stocking rate. It was concluded that, although some of the treatment differences were small, grazing method differences in the DMD of diets might at least partially account for observed differences in livemass gains under the two grazing systems.     

Effect of continuous grazing in the dohne sourveld on species composition and basal cover

Abstract

In a grazing trial conducted at the Dohne Agricultural Research Station, natural grassland was grazed continuously for 36 years with cattle. In a second investigation conducted on similar grassland, paddocks were grazed or rested, in all combinations of the four seasons of the year, over a ten year period. Changes in botanical composition and cover of the sward were monitored at regular intervals. The results of these investigations indicate that under a regime of non‐selective grazing the composition of Dohne Sourveld is remarkably stable. After 36 years of continuous grazing the species composition of the sward was largely maintained. Floristically Dohne Sourveld is dominated by a small number of grass species of which Andropogon appendiculatus, Elionurus muticus, Heteropogon contortus, Sporobolus africanus, Themeda triandra and Tristachya leucothrix are the most important. These species react differently to under‐utilization or increasingly severe defoliation, enabling them to be classified into decreaser or increaser categories. Severe defoliation resulted in a marked decrease in basal cover but only small changes in relative species composition. As the intensity of defoliation increases, decrease in grass cover is associated with an increase of forbs, such as Senecio retrorsus.     

Partial replacement of dried Leucaena leucocephala (Lam.) de Wit leaves for noug (Guizotia abyssinica) (L.f.) Cass. seed cake in the diet of highland sheep fed on wheat straw

This study investigated the effect of replacing noug (Guizotia abyssinica) (L.f.) Cass. seed cake by dried Leucaena leucocephala (Lam.) de Wit leaves on feed intake, live weight gain, nutrient digestibility, and nitrogen balance of highland sheep in Tigray Region in northern Ethiopia. Twenty intact yearling male highland sheep weighing16.9?±?1.62 kg were used in a randomized complete block design and included the following four treatments: T1 (control, wheat straw ad libitum?+?200 g noug seed cake (NSC)?+?150 g wheat bran (WB)); T2 (wheat straw ad libitum?+?170 g NSC?+?44.3 g dried L. leucocephala (DLL)?+?150 g WB); T3 (wheat straw ad libitum?+?140 g NSC?+?87.3 g DLL?+?150 g WB); and T4 (wheat straw ad libitum?+?110 g NSC?+?130.2 g DLL?+?150 g WB). Sheep fed on T4 diet consumed higher total dry matter (658 g/head/day) and recorded the highest average daily weight gain (59 g/head/day). Sheep fed on T4 diet had higher dry matter (61 %), organic matter (63 %), and crude protein (75 %) digestibility values than the other treatments. Sheep fed on T3 diet demonstrated higher feed conversion ratio (11.93) than sheep kept on the other treatments. All sheep exhibited positive nitrogen balance, with the highest nitrogen retention being measured in T4 (12 g/head/day). It is concluded that partially replacing NSC by DLL can improve total dry matter intake, digestibility of nutrients, and body weight gain in highland sheep fed on wheat straw as the basal diet.     

The effect of 7, 8-methylenedioxylycoctonine-type diterpenoid alkaloids on the toxicity of tall larkspur (Delphinium spp.) in cattle

Delphinium spp. contain numerous norditerpenoid alkaloids which are structurally delineated as 7, 8-methylenedioxylycoctonine (MDL) and N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids. The toxicity of many tall larkspur species has been primarily attributed to their increased concentration of MSAL-type alkaloids, such as methyllycaconitine (MLA), which are typically 20 times more toxic than MDL-type alkaloids. However, the less toxic MDL-type alkaloids are often more abundant than MSAL-type alkaloids in most Delphinium barbeyi and Delphinium occidentale populations. Previous research demonstrated that MDL-type alkaloids increase the acute toxicity of MSAL-type alkaloids. In this study, we examined the role of MDL-type alkaloids on the overall toxicity of tall larkspur plants to cattle while controlling for the exact dose of MSAL-type alkaloids. Cattle were dosed with plant material from 2 different populations of tall larkspur containing either almost exclusively MDL- or MSAL-type alkaloids. These 2 plant populations were combined to create mixtures with ratios of 0.3:1, 1:1, 5:1, and 10:1 MDL- to MSAL-type alkaloids. The dose that elicited similar clinical signs of poisoning in mice and cattle was determined for each mixture on the basis of the MSAL-type alkaloid content. As the ratio of MDL- to MSAL-type alkaloids increased, the amount of MSAL-type alkaloids required to elicit clinical signs decreased. These results indicate that the less toxic MDL-type alkaloids in tall larkspur exacerbate the toxicity of the MSAL-type alkaloids. Consequently, both the amount of MSAL-type alkaloids and the amount of total alkaloids should be fully characterized to determine more accurately the relative toxicity of tall larkspur plant material.     

The effect on chick growth of a trypsin inhibitor isolate from the field bean (Vicia faba L.)

An extract rich in trypsin‐inhibiting activity was obtained from field beans (Vicia faba L.) and added to a diet containing autoclaved field bean meal. There was no significant effect on chick growth but pancreas size was significantly increased and food conversion efficiency was reduced.     

The effect of different food types and rations on the liver and muscle of cod (Gadus morhua L.)

In a short time feeding experiment it was shown that the liver weight of cod was significantly reduced in prawn-fed cod compared to sand-eel-fed cod. The dry weight and the protein content of the muscle were not significantly reduced. It is concluded that short time energy deprivation of cod primarily affects the liver. The results futher support the view that the food type and ration of cod can produce anomalous effects in field studies of e.g. parasite induced liver weight decrease in cod.     

饲料中添加糖代谢调节因子对欧洲鳗鲡生长的影响

通过在欧洲鳗鲡(Anguilla anguilla L.)幼鱼饲料中添加糖代谢调节因子(喜福得),在室内循环水族箱中饲养初始体重为41.07±0.37g的欧洲鳗鲡56d,研究喜福得对其生长性能的影响。结果表明,饲料中添加0.1%的喜福得能促进欧洲鳗鲡的生长,试验组饲料的幼鳗增重率、饲料效率及蛋白效率与对照组相比分别提高了18.4%、11.2%和11.48%。     

白头翁根不同提取物体外抑菌试验研究

白头翁为毛莨科多年生白头翁属植物白头翁Pulsatilla chinensis Bunge Regel 的根茎.始载于<神农本草经>,列为下品,是常用中药,具有清热解毒、凉血止痢、燥湿杀虫的功效.传统主要用于治疗细菌性痢疾、阿米巴痢疾等.现代研究认为白头翁除了抗菌和抗病原作用外,还具有提高机体免疫力、抑制巨噬细胞分泌IL-6、抗癌、抗炎、抗毒、止泻、镇静、镇痛、杀灭滴虫和球虫、抑制肠运动、抗内毒素血症等作用[1].     

Developmental horizons in the pre‐natal development of the Greater cane rat (Thryonomys swinderianus)

The Greater cane rat (GCR, Thyronomys swinderianus) is a precocial rodent predominantly found within Africa. Economic and scientific interests have led to several research efforts towards the domestication and better understanding of the biology and development of this rodent. Despite these efforts, information on the pre‐natal development of this rodent is currently lacking. This study characterises distinct developmental milestones including skin pigmentation, emergence and distributions of hairs, calvarium consistency, teeth eruption, development of appendages, sensory organs and external genitalia in the pre‐natal GCR and assesses quantitative body parameters, that is body weight, body and crown–rump lengths across its entire gestation length (gestation days [GDs] 10‐140). Using these external features, we provide baseline reference ontogenetic scales for GCR embryos and fetuses, employable for stage, age and sex estimation of the pre‐natal GCR in future studies. We observed that the first evidence of an embryo was not seen before the end of the first trimester (GD50) and that the late second trimester (GD80‐GD100) marks the transition from embryogenesis to fetogenesis in the GCR. As both events occur at a much later developmental time point when compared to precocial non‐rodents including human, sheep and pig and slightly later when compared to other precocial rodents such as guinea pig, our data provide first indication that the pre‐natal GCR development might be associated with a reproductive delay. Together, this study expands our knowledge of the development and biology of the GCR, which will improve reproductive and breeding management, and native species conservation of this hystricomorph mammal.     

Temperature effect on muscle growth of the axial musculature of the sea bass (Dicentrarchus labrax L.)

In order to determine the temperature effect on the axial muscle growth of sea bass, a stock of larvae was subjected to the following incubation and cultivation temperatures, respectively: 15 degrees C/ambient, 15/17 degrees C, 17 degrees C/ambient and 17/17 degrees C. In all groups the cross-sectional area of white and red muscles and the number and average area of the white and red muscle fibres were quantified. Results showed that the embryonic period, pre-larval phase and the end of metamorphosis were accelerated at higher temperatures. During the endogenous feeding period, muscle growth took place by fibrillar hypertrophy, and was not influenced by the temperature. Thereafter (external feeding) muscular hyperplasia began, and growth of all the muscular parameters was favoured by the effect of high incubation and cultivation temperatures, with the latter having higher influence. High incubation temperature had an slight effect on muscle growth and body length, which was only observed from 15 days. Metamorphosis finished at 3 +/- 0.4 cm in all the larvae, but this length was earlier reached at higher temperatures. At 120 days, the largest growth was obtained in the larvae maintained at a higher temperature.