首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 531 毫秒
1.
Abstract

The influence of soil pH and fertilization (N, P and Zn) on the dry matter (DM) production, chemical composition (crude protein, P, K, Ca, Mg and Zn content) and organic matter (OM) digestibility of Anthephora pubescens Nees was evaluated in pots. The highest Dm production was obtained in the neutral soil medium (pH 6,5 in H2O). Both the acid (pH 4,5 in H2O) and alkaline (pH 7,5 in H2O) soil mediums adversely affected DM yield, crude protein (CP), Zn content and OM digestibility of A. pubescens. Fertilization invariably increased DM production.  相似文献   

2.
Abstract

A number of grasses were ranked according to the order in which they wilted with diminishing moisture availability, and according to their ability to recover after water replenishment. Digitaria eriantha and Digitaria argyrograpta were the most sensitive to moisture stress, whereas Sporobolus fimbriatus and Panicum stapfianum were last to show signs of wilting. The latter two grass species were the first to recover from wilting during optimum soil water conditions. The leaf water potential and soil water content at which each grass species wilted were recorded.  相似文献   

3.
虎尾草是一种耐盐碱性很强的天然牧草,在吉林省长岭县盐碱化草地上随机选择45个虎尾草天然种群样点,测量每个样点的土壤电导率、pH、缓冲量3个因素作为反映土壤盐碱化程度的胁迫强度指标,在每个样点上测量虎尾草茎叶中有机酸含量作为反映植物生理响应的胁变指标,进行回归分析。结果表明:虎尾草茎叶大量积累柠檬酸、苹果酸、草酸以及总有机酸以响应强盐碱胁迫且与三胁迫因素呈显著正相关,仅积累量较低的琥珀酸相反。多元回归分析发现土壤电导率对除了琥珀酸之外的其他有机酸积累影响最大,电导率可以作为天然盐碱化土壤环境下考察虎尾草响应盐碱胁迫的主要胁迫因素。  相似文献   

4.
Abstract

The productivity of Trifolium repens L. cv. Ladino, under irrigation in the subtropical region of Gauteng, South Africa, is unknown. The performance of T. repens was determined over five years (1981/1982 to 1985/1986), at two defoliation frequencies, four levels of nitrogen (0, 400, 800 and 1 600 kg N ha?1 ‐ total applied over five years), and either the removal or recycling of harvested material. Frequent, compared to infrequent defoliation, resulted in higher dry matter (DM) yields from the second year onwards. Dry matter yields were positively affected by the recycling of material, compared to no recycling. A mean DM yield of 191 ha?1 in the first year and 12 t ha?1 in the final year, was obtained. The highest DM yields occurred during October for all years and lowest DM yields from January to March. The first and final year showed similar peaks (late October) and troughs (March till April). Crude protein (CP) content of the herbage was influenced more by frequency of defoliation than recycling of material, where the highest CP content in any year was obtained from frequent defoliation. Nitrogen fertiliser applied up to a total of 1 600 kg N ha?1 over five years had no effect on either DM yield or crude protein content. This study has shown that T. repens could be a productive pasture for at least five years in the subtropical region of Gauteng, South Africa. Productivity and quality of T. repens were enhanced by a defoliation interval of less than five weeks and when soil high fertility was maintained by recycled plant material.  相似文献   

5.
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.  相似文献   

6.
Abstract

Tree crowns in semi‐arid areas have often been found to create micro‐habitats of improved soil physical and nutrient status and reduced evapotranspiration. These encourage the growth of mesic, palatable and high yielding perennial grasses in otherwise arid environments. A two‐year study, in areas with a long history of light grazing, at Matopos Research Station sought to establish whether the soil nutrient status and micro‐climate under tree crowns are different from those in open areas, and whether the differences are affected by soil type and tree species. The study trees were Terminalia sericea and Acacia karroo. There were consistent patterns in soil nutrient status between understorey and open areas, although these patterns were largely not significant. There was also a consistent pattern in soil volumetric water content of open areas > T. sericea > A. karroo understorey areas. Tree crowns reduced solar radiation reaching understorey areas by an average of 88% and rainfall by an average of 15%. The findings on soil nutrient status are consistent with results from disturbed systems, and challenge the dogma, at least for soil nutrient status, that conservative stocking rates are beneficial.  相似文献   

7.
Abstract

The grazing value of the seven most prominent grass species in Tarchonanthus‐limeveld was investigated from 1977 to 1981.

The frequency of utilization of Chrysopogon serrulatus was exceptionally high (93%), while Sporobolus fimbriatus, Themeda triandra and Digitaria seriata were intermediate (50–60%) followed by Cymbopogon plurinodis (34%). Eragrotis lehmanniana and Fingerhuthia africana were poorly grazed (12 to 16%). The utilization of species was influenced by stocking rate. Statistical differences between species indicated a relatively high biomass production (600 to 740 g DM/m2 per year) for E. lehmanniana, C. plurinodis and T. triandra, while F. africana, S. fimbriatus and D. seriata were intermediate (320 to 420 g DM/m2 per year). E. lehmanniana, C. plurinodis and T. triandra produced the highest above‐ground phytomass, but had a lower crude protein content (2,9 to 7,4%) and digestibility (46,1 to 61,3%) than the other four species (3,8 to 9,7% crude protein and 50,5 to 68,4% digestibility).  相似文献   

8.
Abstract

The long term effects of a 5N x 3P factorial fertilizer application trial on hay yields, botanical composition and soil properties of veld are presented. Significant increases in hay yields were recorded during most years. There was a strong correlation (r = 0,757) between mean (over all 15 treatment combinations) annual hay yields and annual rainfall.

N and N + P fertilizer lowered the percentage basal cover of the tribe Andropogoneae. A notable exception of this tribe was Heteropogon contortus which increased significantly at the lower fertilizer levels. The basal cover of the tribe Paniceae generally increased with N and P fertilizer application. The reaction of the basal cover of the tribe Eragrosteae showed little by way of definite tendencies.

Increasing N and P levels generally resulted in decreases in soil pH, Ca, Mg, K and an increase in compaction of the soil surface layer. However, higher levels of N x P resulted in higher water infiltration rates than occurred in control plots, although initial infiltration rates were greatest in control plots. Despite certain undesirable effects of fertilizers on basal cover and certain chemical and physical properties of the soil, the fertilized plots maintained a high level of production.  相似文献   

9.
Lactic acid bacteria were screened for potential probiotics for use as feed additives. We obtained 3,000 isolates from feces of: cattle, dogs, goats, and infants; milk; yogurt; cheese; fermented sausages; Kimchi; and Cheonggukjang and tested their antibacterial activity toward indicator pathogens, including Bacillus cereus, Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica Enteritidis. We further tested their tolerance to artificial gastric juice (1% [w/v] pepsin, pH 2.5) and bile acid (0.1% [w/v] oxgall, pH 6.8). Six isolates exhibited strong antibacterial activity against indicator pathogens. The PA40 isolate from Kimchi exhibited marked resistance to artificial gastric juice and bile acid. The antibacterial substances produced by PA40 were stable to heat, pH, and enzymes. Strain PA40 was identified as a Lactobacillus curvatus strain using chemical tests and 16S rDNA sequencing and produced 248.4 mmol/L lactic acid after 48 hr of fermentative growth. The L. curvatus PA40 strain was also highly tolerant of the artificial gastrointestinal model system. Our results indicate that L. curvatus PA40 could be used as a potential probiotic feed additive.  相似文献   

10.
Abstract

Satellite‐derived vegetation indices were used to identify a geochemical mound of higher active greenness in the Karoo National Park, Beaufort West, South Africa. We determined whether this mound was occupied by plants with higher CO2 assimilation rate. Plant cover on and off the mound was determined. Three woody species with high cover were selected for further investigation. Two deep‐rooted species, Rhigozum obovatum Burch. and Eriocephalus ericoides (L.f.) Druce, showed greater net CO2 assimilation rates on the mound. Net CO2 assimilation rates for the third species, Pentzia incana (Thunb.) Kuntze were similar both on and off the mound. In an attempt to find a mechanistic basis for the elevated CO2 assimilation rates, the relationships between soil factors, foliar nutrients and CO2 assimilation capacity were also examined. Our results suggest that the elevated net CO2 assimilation was not mediated via improved soil or plant water relations on the actively greening mound, nor through a difference in nitrogen levels in the soil or plant material, but possibly by way of the higher sub‐soil phosphorus levels measured from the geochemical mound. Genotype and cover cannot alone be used for rangeland condition assessment since localized elevated soil nutrient status (patchiness) contributes to greater photosynthetic carbon gain which may confer superior browsing responses to plants occurring on these mounds.  相似文献   

11.
Summary

A new chemotherapeutic agent, pipemidic acid, was used to treat 14 dogs and 2 cats with recurrent urinary tract infection caused by multiresistent strains of Escherichia coli and Proteus spp. Bacterial culture of the urine after treatment revealed disappearance of the microorganisms in all patients.

It is concluded that pipemidic acid is a promising chemotherapeutic agent for urinary tract infections caused by multiresistant E. coli and Proteus spp., with the condition that bacterial culture during the course of treatment is obligatory.

It is concluded that pipemidic acid is a promising chemotherapeutic agent for urinary tract infections caused by multiresistant E. coli and Proteus spp., with the condition that bacterial culture during the course of treatment is obligatory.  相似文献   

12.
Abstract

Tannic acid, propyl gallate, methyl gallate, and gallic acid were tested for their inhibitory effects on selected aquatic microorganisms by the well assay technique. Tannic acid, propyl gallate, and methyl gallate in deionized water inhibited the growth of Aeromonas hydrophila, A. sobria, Edwardsiella iclaluri, E. tarda, Pseudomonas fluorescens, and Escherichia coli, but gallic acid did not. When 500-μg/mL concentrations of these four compounds were tested in sterilized fish pond water at pH 7.0 and with a low bacterial inoculum of 103–104 colony-forming units (CFU) per milliliter, they inhibited the growth of P. fluorescens and (except for tannic acid) E. coli. Pseudomonas fluorescens inoculated at 103–104 CFU/mL in pond water was inhibited by methyl gallate, propyl gallate, and tannic acid concentrations as low as 50 μg/mL, but a gallic acid contration of 100 μg/mL was required for inhibition. Escherichia coli was inhibited by methyl gallate and propyl gallate at 250 μg/mL and by gallic acid at 500 μg/mL, but it was not inhibited by tannic acid at concentrations up to 500 μg/mL in water of pH 7.0. Tannic acid (500 μg/mL) did inhibit E. coli growth at pH 4.5.  相似文献   

13.
Abstract

Water was withheld from individual plants of Themeda triandra and Sporobolus fimbriatus growing in pots in a greenhouse. Leaf extension growth, followed by successive degrees of tiller desiccation, were monitored on a daily basis and related to diminishing moisture availability. Leaf extension growth ceased after about 40 % soil water depletion in both species on the sandy clay loam used in the trial. Thereafter, leaves and growing points senesced progressively with increasing evaporative demand, despite a relatively small drop in soil moisture content. The tentative conclusion is that active leaf growth in semi‐arid grassveld takes place in short sporadic spells subsequent to each effective rainfall event. It seems, for example, that after a rain of 50 mm in midsummer, the duration of active leaf growth could be no more than a week.  相似文献   

14.
Summary

Sows were made tolerant to Escherichia coli endotoxin by daily intravenous (IV) injection of the pyrogen. A refractory state was induced, characterised by a markedly decreased fever. In contrast, intramammary (IMM) infusion of only a quarter of the endotoxin dose to which the animals were made tolerant by IV injection produced a markedly increased fever. This finding suggests that inflammatory endogenous mediators were released in the mammary glands and that their subsequent absorption into the blood circulation, and not the absorption of endotoxin caused fever.  相似文献   

15.
Abstract

AIMS: To measure the development of Teladorsagia (=Ostertagia) circumcincta and Trichostrongylus colubriformis eggs to third-stage infective larvae (L3) at different times of the year. Also, to measure the spatial distribution of L3 across herbage, soil and faeces, in order to assess whether spatial issues could be important in larval dynamics on pasture.

METHODS: Field plots were contaminated with sheep faeces containing approximately 20,000 eggs of each of T. circumcincta and T. colubriformis on five separate occasions, viz 01 December 1996 (summer), 18 March 1998 (autumn), 17 June 1998 (winter), 15 October 1998 (spring), and 23 July 1999 (winter). Replicate plots (n=10) were harvested at intervals for up to 12 months after deposition of faeces, and the number and distribution of L3 were measured. Larvae were sampled from faeces (where these remained), herbage, and three soil zones to a depth of 145 mm.

RESULTS: There were large differences between contamination dates in the percentage of eggs that developed to L3. For both species the highest percentage development was for eggs deposited in December (7.8% and 25.9% for T. circumcincta and T. colubriformis, respectively) and the lowest for June (0.4% and 0.03% T. circumcincta and T. colubriformis, respectively). Development in winter was often delayed, and this was always associated with a low yield of larvae, probably due to compounding mortalities associated with long periods of exposure to low temperatures.

The relative distribution of L3 present on herbage, in faeces or in the soil varied between sampling times. However, overall the most L3 were recovered from soil (74% and 66% for T.circumcincta and T. colubriformis, respectively, averaged over all samples), and the lowest recoveries were from the herbage.

CONCLUSIONS: Although the data are limited, the results indicated that the highest percentage of eggs developed to infective larvae in summer and only minimal development occurred in winter. The data do not support the view that substantial contamination of pastures with sheep parasites occurs over winter. Large numbers of larvae were recovered from soil, which indicates that, assuming they can subsequently migrate onto herbage, soil is a potentially important reservoir ofinfective larvae in New Zealand. Therefore, the spatial distribution of L3 on pasture may affect both the dynamics and transmission of parasite populations. Further work on both these issues is warranted.  相似文献   

16.
Abstract

The study was conducted on smallholder dairy farmers in Tanzania. A number of forage species and feed supplements were collected and analysed. Panicum maximum and P. purpureum constituted the bulky forage in about 20 and 11 households, respectively. The crude protein (CP) content of P. maximum and P. purpureum ranged from 6.5 to 8.5% and 7.8 to 10.2% while in vitro dry matter digestibility ranged from 44 to 50 and 48 to 51%, respectively. The mineral content of these two grasses were adequate for Ca but 95% of the forages were deficient in Cu and Zn and 84% in P. The CP content of multipurpose tree leaf was 3–4 times higher than that of grasses. In conclusion, the study revealed that dairy farmers depended solely on natural grasses and crop residues, which are low in CP, digestibility and mineral content.  相似文献   

17.
Abstract

The influence of dietary amino acids on performance and carcass quality was studied in 192 organic indoor and outdoor pigs given diets with different amino acid levels (recommended amino acid level, 7% and 14% lower) ad libitum in a two-phase feeding system. During phase 2, daily consumption of lysine, methionine+cystine and threonine was higher for outdoor than indoor pigs independent of amino acid level (p=0.002, 0.004 and 0.006, respectively). The outdoor pigs grew faster during phase 2 than the indoor pigs (p=0.001), although feed conversion ratio did not differ (p=0.358). Dressing percentage was higher for outdoor than for indoor pigs (p=0.011) but lean meat content did not differ (p=0.904). The health status of the pigs was evaluated and showed that the incidence of pigs seropositive to erysipelas was higher outdoors. Ascaris suum was present in both production systems, whereas Eimeria sp. only was found among outdoor pigs. The results indicate a discrepancy between pigs housed in different production systems rather than between pigs directed to different dietary amino acid levels. This suggests that growing/finishing pigs fed ad libitum can compensate for dietary amino acid levels lower than the current Swedish recommendations without affecting production results.  相似文献   

18.
A number of Cynodon lines were evaluated at two centres in the Natal Tall Grassveld. On a red clay soil in a relatively moist area good performance was recorded from several star grasses (Cynodon aethiopicus and C. nlemfuensis) and Cynodon hybrids, but herbage production was less satisfactory on a grey‐brown loamy soil at a drier site. Local C. dactylon strains did not compare well with the introduced Cynodon spp. Quality of the Cynodon herbage was good, and no problems were encountered with prussic acid poisoning,  相似文献   

19.
In this study, a novel Lactococcus garvieae B301 was isolated from the intestinal tract of a healthy piglet. L. garvieae B301 was tolerant to acid pH, simulated gastric and small intestinal transit juices, indicating that it was capable of surviving in the gastrointestinal tract. L. garvieae B301 was safe and beneficial to broilers, as broiler chickens supplemented with L. garvieae B301 had lower diarrhoea incidence and mortality than the Control. Moreover, supplementation of broiler diets with L. garvieae B301 resulted in an increase in body weight and the number of caecum lactic acid bacteria and Bifidobacterium spp., and decrease in feed‐to‐gain ratio and the number of caecum coliforms. It also had a positive effect on the thymus index and bursa of Fabricius index and enhanced serum levels of immune globulins. All these results showed that L. garvieae B301 could enhance the growth performance of broiler chickens and improve their health. Thus, L. garvieae B301 could be a promising feed additive for broiler chickens.  相似文献   

20.
Abstract

Hierarchical classification based on proportional species composition of the grass layer was used to identify and classify semi‐arid rangeland into range types. The relation between range types produced by the classification and the environmental parameters measured were investigated using a two‐group, and a multi‐group stepwise linear discriminant function analysis. The first split of the TWINSPAN dendrogram separated savanna from open grassveld. The open grassveld was characterized by Themeda triandra, Microchloa caffra, Eragrostis capensis and E. plana and the savanna by Setaria neglecta, Sporobolus fimbri atus,Panicum stapfianum and Cymbopogon plurinodis. The two range types were best discriminated by rainfall, soil depth and altitude with sites in the grassveld corresponding to deep soils and receiving rainfall of more than 450 mm a‐1, and sites in savanna corresponding to shallow soils and receiving rainfall of 400–500 mm a‐1. Further divisions within these two range types were related to soil textural and chemical characteristics of the A‐horizon. Multi‐group discriminant function analysis identified eight environmental variables which best discriminate between range types at level 3 of the hierarchical dendrogram. Rainfall, soil depth and altitude were selected as the most important environmental variables discriminating between range types. Reclassification by discriminant analysis using the eight selected environmental factors resulted in a 67% concurrence with range types. It is proposed that the area be stratified on the basis of the current classification for monitoring and management purposes.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号