江河源区退化草地鼠害的治理研究

针对江河源区草场退化、高原鼠兔危害严重的状况,采用了翻耕、耙耱、撒播、轻耙、镇压等一系列治理措施.结果表明,这种以生态工程为主的治理措施,不仅使草场植被在短期内得到恢复,而且害鼠种群数量也得到了有效控制;同时,为防止鼠兔数量回升、减少扩散、播种牧草幼苗免遭啃食和挖掘破坏,在不同处理区又采取了以药物防治为辅的控制措施.在现场药效试验和大面积灭鼠中,0.075%敌鼠钠盐、0.1%C型肉毒杀鼠素和0.1%D型肉毒杀鼠素毒饵对鼠兔均具有良好灭效,且不污染环境,无二次中毒,对保护天敌、发挥生物控制危害具有一定意义.因此,在退化草场鼠害治理中,综合分析各组分之间的相互关系,有针对性地进行治理,才能收到良好效果,从而达到综合治理的目的.     

Reproduction and Lactational Performance of Cattle in a Smallholder Dairy System in Zimbabwe

A study was conducted in two adjacent locations. Nharira (communal) and Lancashire (small-scale commercial) farming areas in Zimbabwe to characterize the breeds and evaluate the reproductive and lactation performance of dairy cattle under smallholder management. The types of cows identified were Friesian, Jersey and Red Dane, and an indigenous Sanga breed called the Mashona and its crossbreds. Both sectors used more exotic and crossbred cows than indigenous cows. The mean monthly weights of the dairy cows were higher in Lancashire than in Nharira and the calving intervals were longer in Nharira than in Lancashire. The mean age at first calving was higher and the mean total lactation yields were greater in Nharira than in Lancashire, but the mean 305-day lactation yields were not significantly different. The mean lactation lengths were longer for the cows from Nharira. It was concluded that the reproductive and lactation performances were low. The calving intervals were extended, probably owing to suboptimal nutrition and heat stress, particularly during the dry season, and to poor management practices, such as delayed mating due to the poor availability of bulls.     

Reproductive Performance of Crossbred Dairy Cows in Different Production Systems in the Central Highlands of Ethiopia

The study was conducted to examine the fertility status of crossbred dairy cows in mixed crop-livestock production (MCLP), market-oriented specialized dairy production (MSDP) and urban dairy production (UDP) systems, including the Holetta Agricultural Research Center (HARC). Data on general farm management variables and reproductive histories were collected from study farms by questionnaire and from individual cow records. Age at first service and age at first calving were 29.58 months (n = 424) and 40.6 months (n = 348), respectively. Cows managed under UDP were younger at first service and at first calving (p<0.05). The mean intervals from calving to first service and to conception were 141.98 days (n = 284) and 185.02 days (n = 219), respectively. The mean calving interval for cows was 551.82 days (n = 258). Cows in MCLP had longer intervals from calving to first service and to conception and longer calving intervals than those managed under MSDP, UDP and HARC. First service conception rate (43.42%), number of services per conception (1.75) and pregnancy rate (79.29%) did not differ significantly between production systems. Reproductive performance was best in UDP followed by HARC and MSDP. The difference between MCLP and the rest points to particular difficulties in that system. To improve reproductive performance and economic benefit, there should be conservative stocking rate, sensible year-round feeding, a herd health plan, and sustainable extension service.     

The Use of Faecal Progestin Measurements to Monitor Reproductive Activity in Mashona Cows in a Smallholder Farming Area of Zimbabwe

The objectives of this study were to investigate the relationship between the concentrations of progesterone (P₄) in the peripheral circulation and progestins in the faeces of cows in a smallholder farming area and to monitor the ovarian activity of such cows. The study was carried out in Sanyati smallholder farming area, located 250 km southwest of Harare. Blood and faecal samples for P₄ and progestin determination, respectively, were obtained once a week from 35 Mashona type cows that belonged to farmers from three different villages. The cows were weighed once every month and all births were recorded. The concentrations of progestins in faeces and P₄ in plasma were positively correlated (r = 0.72, p<0.01). Most of the non-pregnant cows (65%) cycled during the rainy season. Most of those that were acyclic at this time were undergoing post-partum anoestrus. During the dry season, most cows (58%) became acyclic as forage became scarce and of poor quality. Thirty-two calves were born during the study period, mostly during the first or last two months of the year, when there was enough forage. The mean calving to first oestrus in 14 cows that recalved was 71±49 days. Eight of these 14 cows conceived again, the calving to conception interval being 173±94 days. The cows' liveweights were highest in April, at the end of the rainy season. By the end of the dry season, the cows had lost, on average, 15% of their peak weight.     

Changes in platelet life span in dogs with mitral valve regurgitation

Platelet life span was measured in dogs with experimentally-induced mitral regurgitation (MR) by using an in vitro whole-blood biotinylation technique to evaluate the effects of shear stress induced by MR. Mitral regurgitation was created in healthy dogs by ablation of the mitral valve chordae tendineae. Mitral regurgitation was identified by auscultation and postoperative color Doppler echocardiography. Platelets were biotinylated. and derivatized blood was reinfused into the dogs. Biotinylated platelet disappearance was measured over time to determine platelet life span. Pre- and postablation platelet life span was compared in each dog. Platelet life span was shorter in dogs with experimentally induced MR. Shear stress from MR was postulated to shorten platelet life span. Alternations in platelet function and life span may contribute to the progression of cardiovascular disease in dogs with MR. Further studies are required to determine if platelet dysfunction is related to disease progression in these patients.     

Quantitation of reticulated platelets in healthy dogs and in nonthrombocytopenic dogs with clinical disease

Background — Thrombocytopenia is a common disorder in dogs and development of an objective diagnostic assay to measure platelets newly released from bone marrow into the blood would provide a noninvasive way to predict megakaryocytopoiesis. Reticulated platelets are newly released platelets with increased concentrations of RNA that can be detected by flow cytometric analysis of blood stained with thiazole orange (TO).
Objectives — The goals of this study were to establish a reproducible method to quantitate reticulated platelets in dogs, to establish a reference interval for reticulated platelet percentages in healthy dogs, and to determine whether the percentage of reticulated platelets was nonspecifically increased in nonthrombocytopenic dogs with clinical disease.
Methods — Blood samples were obtained from healthy dogs and from nonthrombocytopenic dogs presented for a variety of disorders. An aliquot of whole blood was stained with TO and a phycoerythrin-labeled monoclonal antibody to platelet CD61, then analyzed by flow cytometry.
Results — The coefficients of variation were 7.8% to 15.6% (intra-assay precision) and 6.1% to 19.5% (interassay precision). Overnight storage for 18 to 26 hours, under variable conditions, resulted in an increase in the percentage of platelets staining with TO. The reference interval for reticulated platelets in the healthy control group was 0–4.3% (0–12,095/μL). No significant differences were found in the mean percentage of reticulated platelets or absolute concentration of reticulated platelets between control and affected dogs.
Conclusions — These studies demonstrate a reliable, noninvasive diagnostic assay for measurement of reticulated platelets in whole blood and provide a baseline for assessment of the clinical utility of the assay.     

天然白桦林的特点与经营

通过白桦林样地调查,对白桦林进行了径级分析、死亡木分析和经营分析。结果表明,白桦林是一个不稳定的次生林型。在大片次生林中的白桦林天然更新非常好。现在硬阔已进入演替层;死亡木用“一边竞争”的模型进行预测效果较好。根据分析提出对白桦林进行上层疏伐的经营方法。     

Isotype-specific antibodies in horses and dogs with immune-mediated hemolytic anemia

Classes of antibody bound to erythrocytes were determined using direct immunofluorescence (DIF) flow cytometry in 3 horses and 12 dogs with immune-mediated hemolytic anemia (IMHA). Background levels of antibody binding were determined in samples from 12 horses and 12 dogs that were free of clinical disease. The range of nonspecific binding of a fluorescein isothiocyanate (FITC)-conjugated goat anti-equine immunoglobulin G (IgG) was 19.9–36.7%, but was eliminated by the use of the F(ab)₂ fragment of FITC-conjugated goat anti-equine IgG. Background binding by other class-specific antibodies to equine and canine erythrocytes was negligible. The DIF results were compared to the direct antiglobulin (Coombs) test in 5 horses and 20 dogs with anemia. The former assay was more sensitive in dogs with IMHA than was the Coombs' test (100% versus 58%). In contrast, the Coombs' test had better specificity than the DIF assay (100% versus 87.5%, respectively). Using clinical parameters or response to therapy as the comparison, the positive and negative predictive values for the DIF test were 92% and 100% compared to the values of the Coombs' test of 100% and 62%. The DIF assay detected low levels of cells bound with antibody (<30%) in 5 dogs that were Coombs' test-negative. For both species, performance of the DIF test was independent of the prozone effect. Five dogs with IMHA had IgG and IgM on erythrocytes, 5 had IgG, and 2 had IgM. Three horses had surface-bound IgG, including a horse with suspected penicillin-induced IMHA, a foal with neonatal isoerythrolysis, and a foal with clostridial septicemia. The DIF method was valuable in monitoring the response to therapy in the foal with neonatal isoerythrolysis.     

The Effects of Agricultural Practices on Carabidae in Temperate Agroecosystems

Ground beetles (Coleoptera, Carabidae) occur in all temperate agroecosystems, and have been implicated as predators of many pests, including aphids, lepidopterous larvae, and slugs. Most are polyphagous, and some are primarily spermophagous. The species assemblage present in any particular crop is determined by multiple factors, but usually comprises a limited number of abundantly active species, which may be common to many crop types. Abiotic soil factors, especially soil type and moisture status are important in determining the species present. Crop type affects the carabid assemblage indirectly through cultivation practices and microclimatic changes. Any soil cultivation affects the carabid assemblage, but studies comparing ploughing with reduced tillage have shown varying results, according to local conditions. Pesticides, especially insecticides have a localised and short-term effect, as many carabids rapidly re-invade sprayed crops. The long-term effect of pesticide usage at a landscape scale is, however, more difficult to predict, and may have contributed to the observed decline in carabid diversity in the wider countryside. Whilst fertiliser application is generally beneficial to carabids, comparisons of conventional and organic farming systems suggest that localised short-term variations in species abundances are more important than the overall farming system used. Non-crop habitats are very important to Carabidae, as many use adjacent hedges and field margins for shelter, breeding or dispersal. But other features such as roads may act as barriers to dispersal. It is concluded that further measures need to be taken if Carabidae are to realise their potential in integrated pest management systems.     

Evolution of farm management, nitrogen efficiency and economic performance on Dutch dairy farms reducing external inputs

The implementation of the statutory Mineral Accounting System (MINAS) in the Netherlands in the period 1998–2003 required large reductions in nutrient inputs of dairy farms. Patterns in farm management adjustments throughout 6 years and their effectiveness in terms of nitrogen use efficiency (NUE) and economic performance were evaluated for 45 commercial farms participating in a regional nutrient management project.

Six groups of farms were identified that differed in initial NUE and the change therein. Three groups of farms that were able to rapidly reduce fertilizer N input and establish a consistent farm management strategy were most successful in improving NUE. These farms had a higher gross margin per 100 kg milk than farms without a consistent strategy. The three effective strategies were primarily characterized by (i) continuous, gradual adjustment of the integrated farm management combined with a slight reduction in milk production per ha (re-balancing) versus increasing productivity per animal, thereby reducing maintenance N requirements, while (ii) maintaining or (iii) increasing the production intensity per ha. It was concluded that different approaches to improve NUE can be successful, also in economic terms, although a direct relationship between NUE and gross margin was not observed. The probably implicit choice for adoption of a strategy may be governed by farm endowment and the farmer's skills and objectives.