基于遥感指数的草原火后植被恢复研究

草原火是草原生态系统重要的干扰因子，严重影响着系统的结构与功能。基于遥感数据，以2015年“4·16”特大草原火灾为例，利用ENVI和ArcGIS等软件，分别对NDVI和GPP指数及火烧严重度下的植被恢复过程进行定量分析。结果表明，基于NDVI和GPP指数的火后植被恢复过程表现相似，不同年份植被恢复情况存在一定差异。火灾发生当年（2015年）火烧迹地植被恢复状况高于未发生火灾区域，而在火后第1年（2016年）却又稍低于未发生火灾区域，直到火后第2年（2017年），火烧迹地植被基本恢复到火前状态。同时，不同火烧严重度下的植被恢复过程在存在明显差异。草原火灾发生后当年（2015年），中强度火烧下植被恢复最好，其次是轻度，重度表现最差。草原火烧严重度对植被恢复的影响，主要表现在火后第1个植被生长季。在之后的年份里，由于草原更新能力强大，不同火烧严重度对草原植被的影响不明显。本研究可丰富草原火灾及火烧迹地植被恢复等相关研究成果，同时为草原火灾管理和草原生态系统的可持续发展提供科学依据。     

Infection process of Rhizoctonia solani on Solanum tuberosum and effects of granular nematicides

The infection process ofRhizoctonia solani AG-3 was studied on potato sprouts, cv. Bintje, in growth chamber trials at 15 °C. Initially hyphae ofR. solani grew predominantly in the longitudinal direction of the sprouts (runner hyphae). They tended to follow the junctions between epidermis cells as was observed by SEM. The hyphae formed side-branches mainly half-way of the subterranean parts of the sprouts. They branched several times with short swollen cells to form infection cushions. Lesions developed only underneath the infection cushions and were first observed five days after inoculation. The necrotic area was proportional to the area covered with infection cushions on the sprouts. Depth of the lesions could extend up to the vascular bundle. Sprouts were colonized only in healthy tissue in the epidermal layer underneath the infection cushion and in necrotic tissue. A few days after appearance of the lesions,R. solani formed brown, uninfective mycelium on and in the circumference of these lesions.Aldicarb did not influence any part of the infection process. Ethoprophos delayed the emergence of sprouts, but increased the number of sprouts per tuber. As soon as sprouts had emerged, growth was considerably promoted by ethoprophos. Ethoprophos delayed the appearance of lesions and reduced their size. Oxamyl showed the same effects to a smaller extent.As the size of lesions appears to be proportional to the size of the infection cushions, any agents that change the size of the infection cushions, such as pesticides or antagonists, may alter the severity of the disease.Samenvatting Het infectieproces vanRhizoctonia solani AG-3 werd bestudeerd op aardappelspruiten, cv. Bintje, in een klimaatcel bij 15C. Aanvankelijk groeide de schimmel met runnerhyfen voornamelijk in de lengterichting van de spruit. Via SEM kon waargenomen worden, dat de hyfen hierbij vooral over de begrenzingen van de epidermiscellen groeiden. Het mycelium vormde veel zijvertakkingen, bestaande uit iets gezwollen korte cellen, welke voornamelijk halverwege op het ondergrondse deel van de spruit gevormd werden. Een dichte massa van deze cellen vormde een infectiekussentje. Lesies, welke vanaf vijf dagen na inoculatie werden waargenomen, bevonden zich slechts onder spruitoppervlak bezet met infectiekussentjes. De lesiegrootte was recht evenredig met het spruitoppervlak dat bezet was met infectiekussentjes. De diepte van de lesies reikte tot aan de vaatbundels. De spruit werd alleen door de schimmel gekoloniseerd in gezond epidermisweefsel onder het infectiekussentje en in necrotisch weefsel. Enkele dagen na verschijning van lesies vormde R.solani bruin, niet infectieus, mycelium op en rondom de lesies.Aldicarb had geen effect op het infectieproces. Ethoprophos vertraagde de opkomst en verhoogde het aantal tot ontwikkeling gekomen spruiten per knol in gestoomd zand. Direct na opkomst had ethoprophos echter een sterk groeistimulerend effect. Ethoprophos vertraagde de lesievorming en reduceerde de lesiegrootte, vergeleken met onbehandelde planten. Oxamyl vertoonde deze effecten in geringere mate.Daar de lesiegrootte direct gecorreleerd blijkt met de grootte van het infectiekussentje, mag verwacht worden dat elke beïnvloeding van de ontwikkeling van het mycelium van R.solani, bijvoorbeeld door pesticiden of antagonisten, een verandering van de lesiegrootte ten gevolge heeft.     

Determination of plasma lysosomal enzyme activity and its relationship to severity of injury following blunt vehicular trauma in dogs

Objective: To determine plasma β‐d ‐glucuronidase (βG) activity in the first 4 hours following injury in dogs struck by a motor vehicle, and to evaluate whether the degree of enzyme activity is correlated with the severity of injury. Design: A prospective clinical study. Setting: Veterinary Medical Teaching Hospital. Animals: Thirteen client‐owned dogs that were presented to the Veterinary Hospital of the University of Pennsylvania between June and August 1999 for blunt vehicular trauma. Ten healthy student and staff‐owned dogs served as controls. Interventions: None. Measurements: Plasma was analyzed for βG enzyme activity at the time of presentation (n=13), and 1 and 4 hours (n=7) following presentation to the Emergency Service for blunt vehicular trauma. The results were compared with enzyme activity from healthy controls evaluated serially over 4 hours. Fluorometric analysis using 96‐well microtiter plates was used to perform the enzyme assays. The relationships between presentation (n=13) and 4 hours (n=7) of enzyme activity and 3 indices of metabolic and physical disturbance (serum pH, serum lactate and Animal Trauma Triage (ATT) score) at the time of presentation were also investigated. Main results: Of the 13 dogs, 7 fulfilled the inclusion criteria for comparison of enzyme activity of the trauma over time. A statistically significant difference in βG activity was found in the trauma group (mean 75.6±10.4 U) at 4 hours following presentation compared with controls (mean 48.0±6.4 U). This difference was suggested by 1 hour following presentation (trauma group, mean 70.4±10.9 U; control group, mean 49.8±5.5 U), although it did not reach statistical significance. Thirteen dogs fulfilled the inclusion criteria for comparison of only presentation enzyme activity with trauma severity score, serum lactate, and serum pH. No statistically significant relationship was found between the βd ‐glucuronidase activity and the presenting ATT score, serum lactate concentration, or serum pH at either presentation or 4 hours, although the power of these analyses was low. Conclusions: These results demonstrate that the activity of βG, a lysosomal enzyme, increases significantly in the systemic circulation in dogs 4 hours following blunt trauma. Additional research to include more severely injured dogs, a larger number of dogs, and to follow the course of injury for a longer period of time would be beneficial to further characterize βG activity following blunt trauma.     

Reliably colonising broiler chickens with Campylobacter spp. using a litter-based method

ABSTRACT

1. Chicken-associated Campylobacter spp. are the cause of most food poisoning cases in Europe. In order to study the host–pathogen interactions, a reliable and reproducible method of colonising chickens with the bacteria is required.

2. This study aimed to identify a more appropriate and less invasive method of colonisation (cf. gavaging) by seeding bedding material (litter) that commercial chickens are kept on with a mixture of Campylobacter spp., broth and faeces.

3. The first phase of the study tested the longevity of Campylobacter spp. recovery in seeded litter over 24 h: significantly more Campylobacter spp. was recovered at 0 or 3 h post-seeding than at 6 and 24 h post-seeding, indicating that the pathogen can survive to detectable levels for at least 3 h in this environment.

4. In the second phase, three groups of 10 broiler chickens (negative for Campylobacter spp. prior to exposure) were exposed at 21 days of age to one of three different Campylobacter jejuni and C. coli mixes (A, B, C), using the method above. At 28 days of age, birds were euthanised by overdose of barbiturate or cervical dislocation, and livers and caeca removed for Campylobacter spp. assessment.

5. All liver and 28/30 caeca samples tested positive for Campylobacter spp., with mix A and C giving higher counts in the caeca than mix B. The method of euthanasia did not affect Campylobacter spp. counts.

6. In conclusion, a successful method for reliably colonising broiler chickens with Campylobacter spp. has been developed which negates the need for gavaging and is more representative of how contamination occurs in the field.     

中国荷斯坦牛部分乳房结构特性对泌乳性能的影响

本研究对规模化场奶牛乳房结构部分性状进行评价和测定,旨在分析其影响因素及其与泌乳性能的关系。现场评价和测定我国北方6个规模化奶牛场荷斯坦牛的乳房均衡(2 030条)、乳头长度(1 551条)和乳头位置评分(分前、后乳头,2 839条),使用SAS 9.2 GLM过程采用固定效应模型分析影响上述3个乳房性状的因素,同时分析3个单项性状对校正日产奶量和体细胞评分的影响。结果表明:场和胎次对3个乳房性状影响极显著(P0.01);前、后乳头位置和后乳头长度对校正日产奶量有显著影响(P0.05),校正日产奶量与前乳头位置评分值呈正比,与后乳头位置评分值呈反比;前乳头位置和长度对体细胞评分有显著影响(P0.05),体细胞评分随前乳头位置评分的增大而减小;5~5.5 cm的乳头长度对于校正日产奶量和体细胞评分都最佳。本研究结果为通过乳房性状选择、淘汰并提高奶牛的生产性能、乳房健康提供了参考。     

不同处理对百香果扦插繁殖的影响

对百香果进行扦插试验研究,明确影响百香果扦插效果的关键因素,优化扦插处理的最佳组合,为百香果的快速繁殖提供技术支持。采用3因素3水平正交试验设计,研究分析插穗茎段部位、NAA浓度、扦插基质3个因素对百香果扦插效果的影响,并采用排队评分和公式评分法对扦插成活效果进行综合分析,筛选优化出百香果扦插繁殖的最佳处理组合。插穗部位对百香果扦插成活率的影响最大,NAA浓度和扦插基质的影响相对较小。对根数、平均根粗的影响由大到小为插穗部位、扦插基质、NAA浓度,对平均根长、新生蔓长、新生叶片数的影响由大到小为插穗部位、NAA浓度、扦插基质。综合评分结果表明,插穗部位是影响百香果扦插效果的最主要因素,其次为扦插基质,而NAA浓度的影响最小。百香果扦插的最佳组合为A₂B₃C₃处理,即以中部半木质化茎段为插穗,用300 mg/L的NAA溶液浸泡20 min,选用泥炭混合基质（泥炭:黄壤=1:1）为扦插基质时,百香果的扦插效果最为理想。     

Effect Of Replacing Fish Meal With Blood Meal On Chemical Composition Of Supplement For Nile Tilapia (Oreochromis Niloticus)

The objective of the work was to evaluate the effect on the nutrient content of replacing fish meal (FM) with blood meal (BM) in fish supplement. Three isonitrogenous diets (35% crude protein) were formulated using FM as the main source of animal protein (BM0); 50% replacement of FM with blood meal (BM50); or 100% replacement of FM with BM (BM100). The chemical composition (ash, crude protein, crude fat and crude fibre) and amino acid composition were determined. Replacement of FM with BM did not affect the proximate composition of the diet apart from ash content which decreased with the level of substitution. Substituting fish meal with blood meal reduced the levels of methionine, lysine, isoleucine, leucine, proline, valine and increased the levels of arginine, phenylanine and alanine in the diet. Amino acid indices revealed that BM0 had more amino acids with the highest chemical scores followed by BM50 and BM100. In all the diets, methionine was the most limiting amino acid. The essential amino acid index of the diets reduced with the level of replacement of FM (0.94, 0.88 and 0.77). The study showed substitution of up to 50% FM with BM gave a useful protein diet and 100% gave almost a poor protein diet.     

Effects of burning on soil macrofauna in a savanna-woodland under different experimental fuel load treatments

In West African savanna-woodland, the use of prescribed burning as a management tool has ecological implications for the soil biota. Yet, the effects of fire on soil inhabiting organisms are poorly understood. The aim of this study was to examine the responses of soil macro-invertebrates to early fires in a Sudanian savanna-woodland on a set of experimental plots subject to different fuel load treatments. The abundance of major macro-invertebrate taxa and functional groups, and taxon richness were quantified in soil cores collected from three different soil layers before and immediately after burning. The results indicated that, overall, there was substantial spatial and temporal variation in the composition of macro-invertebrate assemblages. The immediate effects of fire were to reduce total invertebrate numbers and numbers of many invertebrate groups dramatically. This is probably due to the fact that many of the surface-dwelling macrofauna perished as a result of less favorable microclimate due to fire, diminished resources, or migrate to safer environments. Fuel load treatment did not affect the community taxonomic richness or abundance of the soil-dwelling fauna. Furthermore, annual changes in community composition were more pronounced at the burnt site than in the control. This could be related to the inter-annual difference in precipitation pattern recorded during the two-year study period at our site. Since soil macrofauna population declines in fire-disturbed areas, increasing fire prevalence may jeopardize the long-term conservation of fire sensitive macrofauna groups. Special fire management attention is therefore recommended with due consideration to the type of burning and fuel properties to avoid the detrimental effects of intense fire affecting the resilience of savanna soil macrofauna species.     

Associations between postpartum diseases and milk yield and changes in body condition between drying off and parturition of dairy cows in Argentina

ABSTRACT

Aims: To assess the change in body condition score (BCS) during the early and late dry periods and its association with postpartum diseases and milk yield in grazing dairy cows from central Argentina.

Methods: BCS assessments during the dry period, and cow health and milk production records up to 90 days in milk (DIM), were collated for cows from 28 farms at monthly visits between 2007 and 2008. Cows were categorised into four groups; those in Group 1 (n=7,067) maintained or gained BCS during the early and late dry periods; Group 2 (n=2,615) maintained or gained BCS during the early dry period and lost BCS during the late dry period; Group 3 (n=1,989) lost BCS during the early dry period and maintained or gained BCS during the late dry period; and Group 4 (n=5,144) lost BCS during the early and late dry periods.

Results: Cows in Group 1 had reduced odds of having retained fetal membranes (RFM), metritis, and clinical mastitis up to 90 DIM than cows in Group 2 (p<0.001), but the odds of disease were similar to cows in Group 3. The odds of having RFM or clinical mastitis tended to be lower in cows in Group 1 than cows in Group 4 (p=0.08). The odds of cows being culled or dying during the first 90 DIM were lower for cows in Group 1 than for those in Groups 2, 3, and 4 (p≤0.05). Mean accumulated milk yield up to 90 DIM was higher in cows in Group 1 than Group 2 and Group 4 (p<0.001), but was similar to that of cows in Group 3 (p=0.28).

Conclusions and clinical relevance: Cows that lost BCS during the late dry period had increased odds of being diagnosed with several postpartum diseases and had decreased milk yield compared to cows that maintained or gained BCS during the entire dry period. Loss of BCS during any stage of the dry period was also associated with increased incidence of culling or death during the first 90 DIM. These results should raise awareness among dairy cattle producers of the importance of properly managing cow body condition during the dry period, especially during the late dry period.