Policy incentives for reducing nitrate leaching from intensive agriculture in desert oases of Alxa, Inner Mongolia, China

Excessive irrigation and nitrogen applications result in substantial nitrate leaching into groundwater in intensively cropped oases in desert areas of Alxa, Inner Mongolia. An integrated modelling approach was developed and applied to compare policy incentives to reduce nitrate leaching. The integrated model consists of a process-based biophysical model, a meta-model, a farm economic model and an assessment of policy incentives. The modelling results show that there are “win-win” opportunities for improving farm profitability and reducing nitrate leaching. We found that 4471 Yuan ha⁻¹ of farm gross margin could be obtained with a reduction in nitrate leaching of 373 kg ha⁻¹. Farmers’ lack of knowledge about water and nitrogen in soil, and on crop requirements for water and nitrogen could explain the differences, so that agricultural extension is an appropriate policy incentive for this area. When the economic optimum is obtained reductions in nitrate leaching are not achievable without profit penalties and there is a “trade-off” relationship between farm profitability and groundwater quality protection. The combination of low elasticity of nitrate leaching and large elasticity of farm gross margin against water price increases results in very high costs for reducing nitrate leaching (105.6 Yuan kg⁻¹). It is suggested that if the water price increases were coupled with subsidies for adopting nitrate leaching mitigation practices, environmental gains could come at a lower cost.     

晚播对豫北冬小麦叶片生理及产量性状的影响

以冬小麦品种周麦18为材料,设置4个播期,同时对应不同播量,研究了晚播对豫北地区冬小麦叶片叶绿素含量、硝酸还原酶活性、植株干物质积累量及产量的影响.结果表明,晚播对叶片硝酸还原酶活性的影响主要表现在前期,对叶片叶绿素含量的影响主要表现在中期,至生长发育后期,播期对叶片生理性状的影响减小,各处理之间差异不显著.晚播加大播...     

鸽I型副粘病毒病的研究进展

本文就鸽Ⅰ型副粘病毒病的国内外发生历史、流行特点、病原特性、临床症状、病理变化以及免疫防治等方面的研究进展进行了综合整理，以期对该病的深入研究和防制工作起推动作用。     

关于林价费用如何计算国内生产总值的探索

本文通过对实行林价和未实行林价制度的企业计算增加值和国内生产值的研究,探索了林业 企业关于林价如何计算国内生产总值的方法。     

A long term study of the health status and performance of sows on different feed allowances during late pregnancy. I. Clinical observations, with special reference to agalactia post partum

Thirty nine pairs of full sibs were investigated over 6 parities in a long term study on the effects of late pregnancy feed allowance on the occurrence of agalactia post partum and on the performance of sows and piglets. A careful examination of all sows with a rectal temperature exceeding 39.5 degrees C was performed by a veterinarian within the first 48 h after farrowing. Milk-samples were taken from sows with elevated rectal temperatures and showing clinical symptoms of agalactia. During the last 15 days of gestation the sows in the control group were fed 3.4 kg daily and the sows in the experimental group 1.0 kg daily of a commercial type of diet. In 26.6% of the farrowings in the control group the sows were agalactic whereas the corresponding figure in the experimental group was 14.4%. On clinical examination udder changes were observed in a majority of the diseased sows in both groups. However, the agalactic sows in the control group were generally more affected, with lower water and feed consumption than in the experimental group. No effects of age of the sow (parity number) or length of the gestation period on the incidence of agalactia were demonstrated. The rectal temperature of agalactic sows was significantly higher than in the healthy sows already 1 day before farrowing. The agalactic sows farrowed a larger number of stillborn piglets, which indicates an early establishment of the disease. The number of weaned piglets at 6 weeks did not differ between agalactic and healthy animals. The interval from weaning to first oestrus was not influenced by agalactia in the preceding lactation.     

Preliminary findings from an experimental study of caprine besnoitiosis in Kenya

Inoculation of cystozoites obtained from natural, chronic cases of caprine besnoitiosis produced clinical disease in goats but not in rabbits, mice, guinea pigs, hamsters, rats or cattle. Histological examination of tissue sections from the experimental animals showedBesnoitia cysts only in goats. This, together with field observations that cattle reared together with goats having besnoitiosis do not contract the disease, suggests that theBesnoitia species that infects goats in Kenya is host-specific and is notBesnoitia besnoiti. We suggest that the nameBesnoitia caprae be adopted for the caprine pathogen.     

三种复合维生素添加剂对2龄鲤鱼饲养效果的比较

于同一湖中设置聚乙烯网箱(5m×5m×25m)10个,分为5组,每组2个网箱,放养2龄鲤鱼。第1、2、3组放养尾重153.58g,第4、5组放养尾重320.24g。第1、4组鱼给予本课题组配制的鲤鱼复合维生素添加剂,第2组给予VM-101复合维生素添加剂,第3、5组给予“鱼乐牌”鱼用复合维生素添加剂。饲养133 d。结果,第1组鱼增长率分别比第2、3组提高6.02%和18.12%;第4组鱼增长率比第5组提高14.28%。第1组鱼肥满度高于第3组,但与第2组相比无统计学差异。第1组鱼鲜肉粗蛋白含量高于第2、3组。第1～5组的饵料系数分别为3.02、3.27、4.20、3.07、和4.30。     

Ability of veterinary pathologists to diagnose classical swine fever from clinical signs and gross pathological findings

Clinical signs recorded in a classical swine fever (CSF)-suspect situation and the results of the subsequent post-mortem examination (PME) from swine submitted to post-mortem during the 1997–1998 CSF epidemic in the Netherlands, were presented in an experiment as anonymous cases (without knowledge of the actual infection status of the submission) to five veterinary pathologists for their judgment: CSF-suspect or non-suspect. It was presented to them in two hypothetical situations: country was free of CSF for 5 years and CSF was detected in the country 2 weeks ago. Subsequently, their judgment was compared to the gold standard (infection status of the submission on the basis of an immunofluoresence assay on tissue samples) and the sensitivity (Se) and specificity (Sp) of clinical diagnosis was estimated. Furthermore, intra- and inter-pathologist agreement on pathological diagnosis was measured. Adding information on clinical signs to information on PME resulted in a significant increase in median Se and a significant decrease in median Sp for a clinical judgment by pathologists. Also, median Se was significantly higher—and Sp significantly lower—for a clinical judgment by pathologists in a situation in which CSF was detected 2 weeks ago in the country compared to the situation in which the country had been free of CSF for 5 years. Apparently, the internal threshold of pathologists is severely adjusted depending on the actual disease situation in a country. Intra-rater agreement ranged from fair to almost perfect for a clinical diagnosis on the basis of PME. There was considerable variation between pathologists, especially if clinical diagnosis was based on the combined information on PME and clinical signs observed in the herd. Inter-rater agreement was substantial for the diagnosis based on information on PME. Inter-rater agreement was considerably lower for the diagnosis based on the combined information on PME and clinical signs observed in the herd.     

Infectious pancreatic necrosis in Atlantic salmon, Salmo salar L

A clinical and histopathological review was carried out of 21 outbreaks of acute infectious pancreatic necrosis (IPN) in Scottish Atlantic salmon, Salmo salar L., farms (13 marine and eight fresh water) during 1991-2004. A distinctive syndrome was evident in both post-smolts in sea water and fry in fresh water, where liver lesions, which had not previously been associated with IPN, became a consistent finding in addition to the more typical pancreatic and intestinal changes. Initial cases were described in post-smolts in Shetland, but by the end of the period of investigation this type of pathology had extended down the West coast of Scotland and into Ireland. Limited viral strain analysis suggested that similar strains were involved in both fresh water and sea water and that these differed from earlier isolates from rainbow trout, Oncorhynchus mykiss (Walbaum). In fresh water, recovered fish frequently developed a greatly distended intestine associated with accumulation of undigested food. In sea water, after the initial, often significant (50% or more), losses, there were many fish which failed to grow and became chronically emaciated and prone to sea louse infection. Although use of transfer diets containing immune enhancers and the selection of IPN resistant broodstock has reduced losses the disease remains a serious cause of economic loss.     

Promoting the use of home-mixed supplements as alternatives to commercial supplements in smallholder beef production systems in the subhumid region of Zimbabwe

The economic and performance effect of supplementing smallholder cattle by substituting commercial feed with iso-nitrogenous and iso-energetic diets based on alternative protein sources was investigated in two trials. In trial 1, three diets (commercial concentrate, commercial concentrate partially substituted with mucuna, and commercial concentrate partially substituted with lablab–cowpea) compared with veld grass were allocated to 12 cattle in a complete randomised block design. In trial 2, a double complete randomised block design with 40 cattle assigned to four forage legume-based diets, a poultry-based diet and a commercial beef concentrate was carried out. Diets were offered at 1.5% of body weight daily over 56 d. Average daily weight gain (ADWG) was measured weekly in trial 1 and fortnightly in trial 2. In trial 1, ADWG was significantly (p < 0.05) higher for animals on supplements compared with non-supplemented cattle. In trial 2, ADWG was significantly highest on the groundnut stover-based diet and least on the poultry litter diet. Supplementation had a positive effect on ADWG and economic performance of smallholder beef cattle. Substitution of commercial concentrates with alternative protein sources reduced diet costs and significantly improved gross margins.