Urea in feeds for sea water farmed Atlantic salmon: effect on growth, carcass quality and outbreaks of winter ulcer

The main objective of the present study was to evaluate whether dietary supplementation of urea might reduce the incidence of winter ulcer in sea water-farmed Atlantic salmon. Salmon destined to be S0 smolt were fed with a urea-supplemented diet (0 or 20 g kg⁻¹ urea) over an 8-week period prior to sea water transfer and were then fed supplemented diet (0, 5, 10 or 20 g kg⁻¹ urea) during the first and second winters in the sea. During the first winter positive relationships between dietary urea and plasma urea and between plasma urea and plasma osmolality were observed. Further, plasma osmolality displayed a negative relationship to mortality. Of the salmon that died during the first winter in the sea 90% had one or more skin ulcers. Both during the first and second winter there were fewer salmon with ulcer among fish fed with the diets supplemented with urea. Salmon fed with 20 g kg⁻¹ urea tended to have higher percentage water in the muscle. Mortality and incidence of salmon with ulcer seemed to relate to plasma osmolality amongst fish fed on diets that differed in levels of urea supplementation, suggesting that an osmotic imbalance may contribute to the development of winter ulcer in farmed salmon. Salmon fed with 20 g kg⁻¹ urea showed significantly greater body weight during the second winter in sea. Fish killed without prior starvation had significantly higher level of muscle urea in the 20 g kg⁻¹ urea group compared with fish fed with the unsupplemented diet. However, a 13-day starvation period reduced urea content in the muscle to the level of the control. No effects of dietary urea supplementation on the sensory quality of market size Atlantic salmon were observed.     

我国肥料研究领域的新进展

近年来,我国肥料研究领域的研究工作取得了显著进展,特别是在缓(控)释肥料的研制、植物营养遗传特性研究、新型施肥理论建立、施肥信息化技术应用等方面取得了突出成果。     

氮源和水平对肉牛体外瘤胃发酵特性的影响

为研究氮源和水平对肉牛瘤胃发酵特性的影响,本试验利用体外培养法研究不同水平(0、50、100和200 mg/L)的尿素、亮氨酸、异亮氨酸和缬氨酸对培养液pH、氨态氮、微生物蛋白质、挥发性脂肪酸的影响.结果表明:在体外培养条件下,以亮氨酸和异亮氨酸为氮源,培养液pH和微生物蛋白质浓度分别显著低于和显著高于以尿素为氮源(P＜0.05),以支链氨基酸为氮源培养液氨态氮浓度显著低于以尿素为氮源(P＜0.05),以异亮氨酸为氮源培养液总挥发性脂肪酸、乙酸和丙酸浓度都显著高于其他氮源(P＜0.05);随着氮水平的提高,培养液pH以及氨态氮、微生物蛋白质和丙酸的浓度都显著的升高(P＜0.05);氮源和水平对各指标均存在显著的互作效应(P＜0.05).结果提示,亮氨酸作为氮源更有利于微生物蛋白质的合成;200 mg/L的氮水平有利于瘤胃微生物的发酵;氮源和水平对瘤胃发酵存在互作效应.     

包被纳米氧化锌对断奶仔猪生长性能、抗氧化酶活性及血清生化和免疫指标的影响

本试验旨在研究饲粮中添加不同水平的包被纳米氧化锌对断奶仔猪生长性能、抗氧化酶活性及血清生化和免疫指标的影响。试验选取21日龄平均体重为(5.29±0.02)kg的长×大二元杂交断奶仔猪180头,随机分为5组,每组6个重复,每个重复6头仔猪。对照组饲喂基础日粮,普通氧化锌组饲喂基础日粮+2 500 mg/kg普通氧化锌,包被纳米氧化锌组分别在基础日粮中添加250、500、750 mg/kg包被纳米氧化锌,正试期14 d。结果表明:与对照组相比,日粮中添加500 mg/kg包被纳米氧化锌能提高断奶仔猪的平均日增重和日采食量(P<0.05),降低耗料增重比(P<0.05),且与普通氧化锌效果相当;与对照组相比,500 mg/kg包被纳米氧化锌组血清锌水平、铜锌超氧化物歧化酶活性和免疫球蛋白G含量升高(P<0.05),尿素氮和丙二醛含量降低(P<0.05),且均与普通氧化锌组差异不显著。结果表示,日粮中添加包被纳米氧化锌可显著促进仔猪生长,提高饲粮中蛋白质和锌的利用率,并能有效改善血清抗氧化酶活性,提高仔猪免疫力,且以日粮中添加500 mg/kg包被纳米氧化锌效果最佳,具有替代高剂量普通氧化锌的潜力。     

The relevance of N fertilization for the amount of total greenhouse gas emissions in sugar beet cultivation

The agricultural sector is highly affected by climate change and it is a source of greenhouse gases. Therefore it is in charge to reduce emissions. For a development of reduction strategies, origins of emissions have to be known. On the example of sugar beet, this study identifies the main sources and gives an overview of the variety of production systems. With data from farm surveys, calculations of greenhouse gas (GHG) emissions in sugar beet cultivation in Germany are presented. Emissions due to the production and use of fertilizers and pesticides, emissions due to tillage as well as field emissions were taken into account. All emissions related to the growing of catch crops during fall before the cultivation of sugar beet were also included. The emissions are related to the yield to express intensity.The median of total GHG emissions of sugar beet cultivation in Germany for the years 2010–2012 amounted to 2626 equivalents of CO₂ (CO₂eq) kg ha⁻¹ year⁻¹ when applying mineral plus organic fertilizer and to 1782 kg ha⁻¹ when only organic fertilizer was applied. The CO₂eq emissions resulting from N fertilization exclusively were 2.5 times higher than those caused by diesel and further production factors. The absence of emissions for the production of organic fertilizers led to 12% less total CO₂eq emissions compared to the use of mineral fertilizer only. But by applying organic fertilizer only, there were more emissions via the use of diesel due to larger volumes transported (126 l diesel ha⁻¹ vs. 116 l ha⁻¹ by applying mineral fertilizer exclusively).As there exists no official agreement about calculating CO₂eq emissions in crop production yet, the authors conclude that there is still need for further research and development with the aim to improve crop cultivation and crop rotations concerning GHG emissions and the therewith related intensity.     

麦麸促进平菇生长的初步研究

在棉籽壳培养基中辅加１０％麦麸或０．４ｌ％尿素均能促进平菇苗丝生长和呼吸消耗，提高于实体生长阶段ＣＭＣ酶、ＨＣ酶活性和绝对生物学效率，而在棉籽壳培养基中辅加微量的维生素Ｂ＿１，对平菇生长无促进作用。这表明：氮素对平菇的生长有重要影响，棉籽壳培养基中的麦麸对平菇生长的促进作用与麦麸中的氮素有关，而与麦麸中的维生素Ｂ＿１无关。     

Ammonia volatilization from nitrogen fertilizers with and without gypsum

Abstract. Ammonia volatilization with and without gypsum incorporation was measured in Gujranwala soil (Udic Haplustalf) in an incubation study using different nitrogen fertilizers e.g. urea, ammonium sulphate (AS), calcium ammonium nitrate (CAN), and urea nitrophos (UNP). Nitrogen from different fertilizers was applied at the rate of 200 mg N kg⁻¹ to two sets of soils in plastic bags (1.0 kg soil) and plastic jars (0.5 kg soil). Soil moisture was maintained at field capacity. Application of urea increased soil pH to 9, three hours after its addition. Ammonium sulphate and calcium ammonium nitrate had little effect on soil pH. Ammonium volatilization losses from fertilizers were related to the increase in soil pH caused by the fertilizers. Consequently maximum losses were recorded due to application of urea. Losses through ammonia volatilization were significantly lower with AS, CAN and UNP in descending order. Gypsum incorporation significantly reduced the losses. Therefore, application of gypsum to soil before urea may substantially improve N use efficiency for crop production by reducing N losses.     

The Influence of Fertilizer-based Seed Priming Treatments on Emergence and Seedling Growth of Sorghum bicolor and Pennisetum glaucum in Pot Trials under Greenhouse Conditions

The effect of priming sorghum and pearl millet seeds with fertilizers was investigated. Two experiments were conducted on M35–1 (sorghum) and ICMH 356 (pearl millet), and ICSV 745 (sorghum) and Barmer (pearl millet) seeds, respectively. Treatments included nitrogen, phosphorous and potassium-based treatments which showed that 7.5 g l⁻¹ of urea substantially enhanced the final germination percentage of seeds. The second experiment included 10 priming treatments with 7.5 g l⁻¹ urea mixed with other fertilizers. Results indicated that soaking seeds for 3 days in urea + one of several fertilizers including N, P or K-based nutrient compositions or micro elements significantly increased germination percentage and speed but did not affect seedling growth at 15 or 60 days after sowing. It is concluded that seed priming treatments with fertilizers may serve as an appropriate treatment for advancing germination of the species studied.     

Nitrate leaching and adsorption in a Kenyan Nitisol

Abstract. ¹⁵N labelled NH₄NO₃ (fertilizer N) was applied at a rate of 50 kg N ha^–1 to an Ando-Humic Nitisol and two maize crops grown on it. About 20 months later, soil cores were taken to a depth of 2.5 m. Leached fertilizer N was found between 1.4 m and 1.8 m deep and was delayed relative to net drainage by between 4.2 and 4.9 pore volumes. Anion exchange capacity (AEC) increased ten-fold down the profile, up to 2.9 cmol_ckg^–1. The delay to fertilizer N leaching was predicted to be between 4.1 and 5.3 pore volumes when calculated from the AEC and from an equation relating delay due to AEC in laboratory columns of repacked soil obtained by Wong et al. (1990b). It was concluded that the nitrate leaching delay equation was also valid in undisturbed field profiles. Two concentration maxima for mineral N were found, which did not usually coincide with the fertilizer N and were thought to result from mineralization of soil organic matter and plant residues at the end of each season. The delay equation overestimated their leaching delay but the results were considered close enough to support the hypothesis for their formation.     

The uptake of fenbendazole by cattle and buffalo following long-term low-level administration in urea-molasses blocks

Fenbendazole (Panacur bolus, Hoechst India Ltd) was incorporated at a rate of 0.5 g/kg into urea-molasses blocks made by two different processes. The concentration of the drug in blocks and its bioavailability were measured using plasma oxfendazole as marker. The recovery of the drug in blocks made by a warm process was 68% and the plasma oxfendazole concentration remained fairly stable at 0.2 and 0.12 µg/ml from day 6 of feeding in cattle and buffalo, respectively. The drug seemed to be inactivated in blocks made by a hot process, with reduced bioavailability. A low and sustained plasma concentration of the active metabolite of the drug could be maintained by self-medication using urea-molasses blocks as fenbendazole carrier.Abbreviations FBZ fenbendazole - HPLC high-performance liquid chromatography - MUMB medicated urea-molasses blocks - OFZ oxfendazole - UMB urea-molasses block