猪日粮中的蛋白质含量既要满足需要又要避免过量

满足猪对必需氨基酸的需要量而不向其饲喂过量的蛋白质,不但经济,而且在营养上更有益处,并且利于环境的保护. 猪日粮需要添加蛋白质,仅仅是因为它可以为猪提供所需要的氨基酸.然而,在日粮所含的全部氨基酸中,只有可消化氨基酸对动物具有生物学价值.     

Vergleichende untersuchungen zum umweltverträglichen und energieeffizienten anbau von energiepflanzen

Auf sandigem Boden wurden 10 für die Verbrennung geeignete Energiepflanzenarten über einen Zeitraum von 6 Jahren unter praxisnahen Bedingungen angebaut und dabei Ertrag, Energiegewinn und umweltrelevante Stoffe in Pflanze und Boden bestimmt. Die Düngung erfolgte in 4 Varianten von 0 bis 150 kg N/ha und mit Holz‐ und Strohasche. Auf Pflanzenschutzmittel wurde gänzlich verzichtet. Die Ergebnisse zeigen, daß mit Ausnahme von Topinamburkraut und Gehölzen mit Untersaat die Erträge im Bereích von 8,5 bis 11,8 t_TM/ha liegen und eine Verringung der Stickstoffgabe von 150 auf 75 kg N/ha nur geringfügige Ertragseinbußen zur Folge hat. Ohne Düngung fallen die Erträge nach 6 Jahren um 20 bis 40% ab, ausgenommen Pappel (ohne Untersaat), die mit 8,9 t_TM/ha ähnlich hohe Erträge wie mit Düngung erreicht. Die Gehalte der emissions‐ und feuerungstechnisch relevanten Pflanzennährstoffe, wie Stickstoff, Kalium, Schwefel und Chlor, sind bei Pappel und Weide deutlich geringer als bei Knaulgras, Roggen, Triticale und Hanf. Eine Stickstoffgabe von 150 kg N/ha bewirkt eine absolute Zunahme des Stickstoffgehaltes der Pflanzen um 0,1 bis 0,3%. Durch Düngemittel und energiebedingte Immissionen eingetragene Schwermetalle, wie Kadmium, Blei, Kupfer und Zink, werden in unterschiedlichem Maße absorbiert. Die Gehölze nehmen verstärkt Kadmium und Getreide verstärkt Kupfer auf. Hohe Energieerträge werden mit Hanf, Pappel und Winterroggen erzielt. Auch bei reduzierter Stickstoffdüngung und mit Pappel selbst bei Nulldüngung werden Nettoenergiegewinne von über 3.200 Liter Öläquivalent pro Hektar und Jahr erreicht.     

Impact of river regulation and hydropeaking on the growth,condition and field metabolism of Brook Trout (Salvelinus fontinalis)

Brook Trout (Salvelinus fontinalis) is an important fish species in Ontario, Canada, supporting recreational fisheries that contribute significantly to local economies. Hydroelectric dams disrupt the river continuum, altering downstream conditions and impacting riverine fish populations. Specifically, Brook Trout activity has been found to increase during hydropeaking periods, when dam operators rapidly increase river discharge to meet electricity demands. Higher energetic outputs driven by hydropeaking may decrease the energy available to allocate towards fish growth and condition, negatively impacting Brook Trout. We investigated the impact of two different hydropeaking regimes on resident Brook Trout populations downstream from a 15‐MW dam used for hydropeaking, compared to a population in a nearby naturally flowing river. Length‐at‐age as determined by otolith back‐calculations was higher in the regulated river relative to the naturally flowing river. Muscle tissue caloric content and weight–length relationships did not differ between rivers. Field metabolism, as inferred from fish otolith δ¹³C values, was higher in the regulated river relative to the naturally flowing river and was significantly positively related to time spent hydropeaking. Higher metabolic outputs in the regulated river were likely offset by an increased food supply, allowing for higher Brook Trout length‐at‐age. The opposing and complicated impacts of river regulation on Brook Trout highlight the need for studies to consider multiple indicators of fish health when characterising the response of fish populations to river regulation.     

A sensitivity analysis to guide research and management for Hector's dolphin

Hector's dolphin (Cephalorhynchus hectori) is an uncommon endemic of New Zealand which is suspected to be in decline due to entanglement mortality. However, uncertainty in available data has led to a dispute between the New Zealand Ministry of Fisheries and the New Zealand Department of Conservation over the status of this species. We use a density-dependent deterministic model to predict the future abundance and geographic distribution of Hector's dolphin under different scenarios of fisheries management. We then examine the sensitivity of this model to a number of parameters for which few or no data are available. We find that two populations of Hector's dolphins are predicted to decline in the future even when the most optimistic parameter estimates are used. The status of the third population is dependent upon the estimate of maximum annual population growth rate. Because of the dependence of final abundance estimates on the estimates of entanglement mortality rates and maximum population growth rate, research efforts should be concentrated on estimating these parameters.     

Concentrations of perfluorooctanesulfonamides in Canadian total diet study composite food samples collected between 1992 and 2004

Canadian Total Diet Study composite samples collected from 1992 to 2004 (n = 151) were analyzed for a series of perfluorooctanesulfonamides that are likely breakdown products or manufacturing residuals associated with perfluorooctylsulfonyl phosphate esters. These esters have been incorporated into coatings for paper and paperboard used in food packaging. N-Ethylperfluorooctanesulfonamide (N-EtPFOSA), perfluorooctanesulfonamide, N,N-diethylperfluorooctanesulfonamide, N-methylperfluorooctanesulfonamide, and N,N-dimethylperfluorooctanesulfonamide were extracted using solvent extraction and quantified by gas chromatography-mass spectrometry. Perfluorooctanesulfonamides were detected in the picograms per gram to low nanograms per gram of wet weight range in all food groups tested-baked goods and candy, dairy, eggs, fast food, fish, meat, and foods to be prepared in packaging. The highest concentrations of total perfluorooctanesulfonamides were observed in fast food composites (from less than the method detection limit to 27300 pg/g of wet weight). Concentrations of N-EtPFOSA appeared to decrease over the sampling period (1992-2004) in French fries and other fast food composites; no such trend was apparent in freshwater fish, marine fish, and shellfish composites. A basic estimate of dietary exposure to perfluorooctanesulfonamides suggests that Canadians (>12 years old) are exposed to approximately 73 ng/person/day from these foods.     

A major ecosystem shift in the northern Bering Sea

Until recently, northern Bering Sea ecosystems were characterized by extensive seasonal sea ice cover, high water column and sediment carbon production, and tight pelagic-benthic coupling of organic production. Here, we show that these ecosystems are shifting away from these characteristics. Changes in biological communities are contemporaneous with shifts in regional atmospheric and hydrographic forcing. In the past decade, geographic displacement of marine mammal population distributions has coincided with a reduction of benthic prey populations, an increase in pelagic fish, a reduction in sea ice, and an increase in air and ocean temperatures. These changes now observed on the shallow shelf of the northern Bering Sea should be expected to affect a much broader portion of the Pacific-influenced sector of the Arctic Ocean.     

Modelling pasture management practices for soil organic carbon gain in livestock systems

Our ability to develop strategies to mitigate climate change includes an understanding of, and our capacity to predict soil organic carbon (SOC) dynamics in livestock systems. Here we assess the capability of the Sustainable Grazing System (SGS) Pasture Model for predicting pasture growth (elongated wheatgrass, Thinopyrum ponticum) and SOC accumulation in different environments and under a range of pasture management practices in hydrohalomorphic soils located in South-eastern Buenos Aires Province, Argentina. After Model calibration, aerial net primary productivity (ANPP) and TSOC content under two grazing intensities (7.5 and 11 cm post-grazing target heights) and two N fertilization levels (0 and 100 kg N ha⁻¹ yr⁻¹) were simulated over a 10 year-period. The SGS Pasture Model predicted 87% of the observed ANPP, with observed and predicted ANPPs averaging 1.46 and 1.42 Mg ha⁻¹ yr⁻¹, respectively. There were differences in simulated ANPP between fertilized and unfertilized treatments both at high and low grazing intensities for the last year of the period. Total SOC contents from the modelling showed differences between high (83.7 to 84.2 Mg ha⁻¹) and low (86.8 to 87.5 Mg ha⁻¹) grazing intensities, with treatments receiving N also showing higher carbon stocks. The positive effect of reduced grazing intensity on soil carbon was explained by an increased input of aerial and subterranean dry matter into the soil. Sensitivity analysis showed that SGS is a robust model, capable of performing effectively under a variety of conditions. Hence, it can be used for exploring management practices to mitigate the impact of livestock systems on emissions and SOC stocks.