麦、瓜、棉、豆间作套种栽培技术

随着杂交棉花在我国长江流域的普及，早熟大豆品种的育成与推广，棉田套种大豆技术也在不断发展，大豆、棉花、西瓜和小麦四种作物间作套种，既能增加生产效益，也能使大豆增产。简要介绍这四种作物的间作套种技术及获得高产、高效的技术关键。     

蔬菜钵苗移栽机取苗臂凸轮机构的设计与试验

采用解析法对蔬菜钵苗移栽机取苗臂凸轮机构进行了详细设计,以解决目前机构推苗作业时间长、速度慢而影响推苗成功率的问题。根据移栽机取苗和推苗作业时取苗针的运动要求,以及取苗臂的结构尺寸,建立凸轮机构设计的数学模型,优化凸轮推程运动角,进而得到凸轮实际轮廓曲线,进行了机构的运动及压力角分析。建立取苗机构的三维实体模型,制造出其物理样机,采用ADAMS软件进行虚拟样机运动仿真,开展高速摄像运动试验。仿真结果和试验结果基本一致,表明改进设计是正确和合理的,同时比较改进设计结果和原设计结果可知,所设计的凸轮机构能够满足蔬菜钵苗移栽的要求,且试验推苗时间比原设计有效缩短了27.9%,有助于提高推苗成功率和蔬菜钵苗移栽机的工作性能。     

In situ ATR-FTIR study on the adhesion of Pseudomonas putida to Red soil colloids

Purpose

Bacterial adhesion to soil particles is fundamentally important in mineral weathering, organic matter degradation, heavy metal transformation, and fate of pollutants. However, the adhesion mechanism between bacteria and soil colloids under continuous flow systems in the natural environments remains unknown.

Materials and methods

The kinetics of Pseudomonas putida cellular adsorption and desorption on Red soil colloid films under controlled flow systems were examined using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Derjaguin–Landau–Verwey–Overbeek (DLVO) and non-DLVO interactions were employed to elucidate the cellular adsorption and desorption kinetics.

Results and discussion

In situ ATR-FTIR spectroscopy can be used effectively to investigate the kinetics of bacterial adhesion to a soil colloid deposit. Surface proteins may be involved in the bacterial adhesion to soil colloids. The adsorption followed pseudo-first-order kinetic equation. High adsorption rate constant and great saturation coverage of adsorbed bacteria were found at high ionic strengths in dynamic systems.

Conclusions

P. putida bacterial cellular adsorption on the soil colloid deposit was irreversible in a wide range of ionic strengths under controlled flow systems. The less reversible adhesion was probably attributed to the DLVO predicted deep secondary energy minima together with non-DLVO factors including polymer bridging, local charge heterogeneities, surface roughness, and Lewis acid–base interactions.     

Litter decomposition reduces either N2O or NO production in strongly acidic coniferous and broad-leaved forest soils under anaerobic conditions

Purpose

The beneficial effect to the environment of nitrate (NO₃ ^?) removal by denitrification depends on the partitioning of its end products into nitrous oxide (N₂O), nitric oxide (NO), and dinitrogen (N₂). However, in subtropical China, acidic forest mineral soils are characterized by negligible denitrification capacity and thus reactive forms of N could not be effectively converted to inert N₂, resulting in a negative environmental consequence. In this study, the influences of C input from litter decomposition on denitrification rate and its gaseous products under anoxic conditions in the acidic coniferous and broad-leaved forest soils in subtropical China were investigated using the acetylene (C₂H₂) blockage technique in the laboratory.

Materials and methods

The coniferous and broad-leaved forest soils with and without litter addition were incubated under anaerobic conditions for 244 h. There were three treatments for each forest soil including addition of 0.5 and 1% corresponding litter (gram of litter per gram of soil) and the control without addition of litter.

Results and discussion

The results showed that litter addition into the broad-leaved forest soil had no effect on average rates of denitrification (calculated as the sum of NO, N₂O, and N₂), whereas in the coniferous forest soil, the addition resulted in a significant increase in average denitrification rate. In the broad-leaved forest soil, both rates of litter addition decreased the production of NO but increased the production of N₂, and high rates of litter addition into the coniferous forest soil promoted the reduction of N₂O to N₂.

Conclusions

Increased decomposition of litter in the forest soils could effectively reduce N₂O and NO production through denitrification under anaerobic conditions.     

北京动物园圈养绿孔雀新城疫免疫实验研究

通过圈养绿孔雀新城疫免疫实验研究,对疫苗的安全性以及免疫效果进行了评估。单苗实验组结果：低毒活苗LASOTA可以使抗体水平在4LOG2以上的时间持续6个月;灭活油苗可以使抗体水平保持在4LOG2以上8个月。联苗实验组接种LASOTA疫苗同时肌肉注射灭活油苗后,抗体水平保持4LOG2以上15个月,表明圈养绿孔雀宜采用联合疫苗免疫方法。联合疫苗的应用不仅表现在较高抗体水平维持时间较长,低毒活疫苗还有产生黏膜免疫的重要意义。滴鼻或点眼接种LASOTA疫苗,要保证疫苗能够作用于哈氏腺,以激发动物机体产生黏膜免疫。此外免疫接种时机很重要,对该病的预防工作不应在动物机体较高抗体水平的时候进行免疫接种,也不应在动物机体已经失去保护力或隐性感染后盲目接种,应选择绿孔雀在健康无病情况下进行。同时为了有效地控制新城疫,必须加强禽群免疫监测。     

啤酒糟发酵产高蛋白饲料菌种的配伍

以啤酒糟为主要原料,采用多菌种混合固态发酵生产蛋白饲料,并通过菌种的配伍实验对发酵产蛋白饲料菌种的组合进行优化,试验结果表明:挑选的8株菌都能在以啤酒糟为唯一底物的平板上生长,并且菌种最佳组合为固氮菌、白地霉、绿色木霉、啤酒酵母、热带假丝酵母等5株菌,其发酵后的蛋白质含量为31.45%,粗蛋白为39.22%,无机氮转化率为56.42%。     

Effect of selection for residual feed intake on feeding behavior and daily feed intake patterns in Yorkshire swine

Residual feed intake (RFI) is a measure of feed efficiency defined as the difference between observed and predicted feed intake based on average requirements for growth and maintenance. The objective of this study was to evaluate the effect of selection for decreased RFI on feeding behavior traits and to estimate their relationships with RFI. Three data sets from the 4th and 5th generations of a selection experiment with a line selected for reduced RFI (LRFI) and a randomly selected control line (CTRL) were analyzed. Lines were mixed in pens of 16 and evaluated for feeding behavior traits obtained from a single-space electronic feeder over a growing period of ~3 mo before ~115 kg. The following traits were evaluated as averages over the entire test period and over the first and second half of the test period: number of visits per day and hour; occupation time per day, visit, and hour; feed intake (FI) per day, visit, and hour; and FI rate per visit. Models used included fixed effects of line and feeder, covariates of on-test age and FI per day, and random effects of pen, on-test group, sire, and litter. Repeated measures models were used to analyze feeding patterns during the day. The LRFI pigs had significantly less FI per day than CTRL pigs for all 3 data sets. With adjustment for FI per day, line differences of all traits were in the same direction for all 3 data sets but differed in significance and size. Feed intake per visit and hour and visits per day and hour did not differ between lines, but the trend was for LRFI pigs to have fewer visits, in particular during peak eating times. The LRFI pigs had a greater feeding rate and less occupation time per day, visit, and hour than CTRL pigs, but this was not significant for all data sets. Correlations of RFI with FI per day and visit and visits per day were positive. Average daily gain was positively correlated with FI per day and visit and occupation time per visit but negatively correlated with visits per day. Feed intake per day was positively correlated with backfat. In conclusion, feed efficiency may be affected by FI behavior because selection for decreased RFI has resulted in pigs that spend less time eating and eat faster.     

Immune responses in piglets infected with highly pathogenic porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) infection compromises the host's innate and adaptive immunity. The aim of this study was to investigate the immune responses of piglets infected with highly pathogenic (HP) PRRSV (HuN4 strain) with or without the immunization with CH-1R attenuated PRRSV vaccine. The response was evaluated for the clinical signs, pathological changes and virus load in immune organs, antibody responses and levels of serum IFN-γ, IL-4 and IL-10. The result showed that in comparison with the piglets received the immunization, the piglets infected with HP-PRRSV alone had the thymus atrophy, decreased serum levels of IL-4 and increased serum levels of IL-10 and INF-γ. These results suggest that elevated IL-10 levels at the early stage of the infection may enhance virus survival and delay the induction of protective immunity, while increased levels of IL-4 induce the effective immune responses and increase the animals' health status.     

Prevalence of Dirofilaria immitis infection in dogs from Dandong, China

The aim of the present study was to estimate the prevalence and risk factors of Dirofilaria immitis infection in dogs from Dandong, China. A total of 886 dogs were examined for D. immitis infection by microscopic examination and PCR, indicating that the prevalence was 16.6% (213/886) and 24.0% (147/886), respectively. The odds of infection were significantly higher in older dogs and dogs sheltered in outdoor, compared to the younger ones and ones sheltered in indoor. No significant difference of infection was observed in different genders, and between pure breed and cross-breed dogs in the same rearing conditions. These results indicated that the risk of exposure to D. immitis in dogs is high in Dandong, China, and prophylaxis against the parasite is advisable to decrease the incidence of canine dirofilariosis.     

Genetic characterization and evolutionary analysis of 4 Newcastle disease virus isolate full genomes from waterbirds in South China during 2003-2007

Complete genomes of four Newcastle disease virus (NDV) strains, isolated from ducks and wild birds in Guangdong province of China from 2003 to 2007, were sequenced and analyzed in this study. Pathogenicity tests in chicken embryos and chickens illustrate that D3 and R8 are lentogenic, and W4 and P4 are mesogenic strains. Phylogenetic analysis using all six genes provides a high resolution profile for genotype designation as genotype I for D3 and R8 strains and genotype VI for W4 and P4 strains. In addition, molecular dating based on different genes suggests that D3 and R8 diverged from their common ancestor at around 1998; W4 and P4 diverged from their common ancestor at around 1999. Subsequent selective pressure analysis displayed specific traits of genes evolution in all 4 strains since their divergence from the recent common ancestor. Furthermore, the geographic origins of 4 strains were deduced to be from Europe via two independent introduction events by phylogeographical analysis. This provides insights to the potential influence of waterfowl migration on NDV epidemiology.