西班牙肉鸡企业的饲养模式

高蛋白原料的价格(像大豆)影响鸡肉价格。企业追求效益最大化就应该调整肉鸡日粮中的蛋白水平。Nutreco公司已经开发出一套灵活的方法来计算获得最大效益的最低日粮蛋白水平。     

A computer-based system for the management of the rust disease of French prunes1

Rust (Tranzscheliu discolor) is the most important disease of French prunes in New South Wales (NSW), Australia. Infection by this fungus occurs only when leaves are wet. The length of time for which the leaves are wet and the temperature during such periods are major determinants of whether infection occurs and its likely severity. The use by prune growers of new rust management strategies depends on knowledge of infection events and therefore requires ready access to environmental data from orchards. To satisfy this need, microprocessor-based device called a Prune Rust Infection Predictor (PRIP) was developed. The instrument measures air temperature, rainfall, and the presence or absence of free water tree canopies. Measurements are taken at 5-min intervals during wet periods. The instrument calculates whether or not conditions have been suitable for rust infection and potential severity of infection. The system has been operated by advisory staff of NSW Agriculture Fisheries since the 1988/1989 growing season. Potential infection period and related environmental data are collected by personal computers via permanently installed telephone lines from PRIPs located within prune orchards. Prune growers are then advised by recorded telephone messages and given appropriate disease mangement advice. Cumulative potential infection period values are used to provide a prognosis of current-season rust epidemic severity. An expert system is also being developed to assist growers in making decisions on specific rust management options.     

A bioassay method for formulation testing and residue studies of sulfonylurea and sulfonanylide herbicides

A bioassay method using the radicles of pea (Pisum sativum L.) and lupin (Lupinus angustifolius L.) was developed for the assessment of trials on herbicides of common use in the sulfonylurea class (chlorsulfuron, triasulfuron and metsulfuron-methyl) and in the sulfonanylide class (flumetsulam and metosulam). Soils within a range of pH 5.8–8.4 with textures from sand to clay were used in these experiments. The sensitivities of the species were similar in chlorsulfuron and flumetsulam trials and their response range varied with soil type and herbicide, e.g. between 0.75 and 6.0 ng triasulfuron g^?1 in the Wimmera grey clay and between 0.125 and 8.0 ng chlorsulfuron g^?1 soil in the Mallee sand. The method was demonstrated in a wide range of uses, encompassing tests of the initial bioactivity of formulations of chlorsulfuron and flumetsulam, monitoring the field leaching and persistence of triasulfuron and measuring relative potencies between the classes, using metsulfuron-methyl and metosulam. The bioassay response provided a high level of reproducibility and precision, which was measurable by the logistic curve-fitting procedure. In each case, R² values were >0.90 and lack-of-fit tests were clearly non-significant at the 0.05 level. Chi-square tests were used to measure differences between ED₅₀'s. The method does not require the pre-germination and selection of seedlings, daily watering or root-washing and results are obtained 7 days from sowing, providing favourable use for routine analyses and large-scale trials.     

The 1882 tilefish kill — a cold event in shelf waters off the north-eastern United States?

A mass mortality of `warm-water' tilefish in the Middle Atlantic Bight between April and August of 1882 suggests an episode of extreme cold in the shelf waters off the north-eastern United States. This cooling is hypothesized to be a consequence of enhanced equatorwards transport of cold water in the Labrador Current, coincident with a minimum in the North Atlantic Oscillation (NAO) index during the early 1880s.
Although there is little direct evidence for this historical event, an analogue for the 1880s cooling is found in the 1960s, at the most recent NAO-index minimum. Post-1945 observations in the Middle Atlantic Bight / Gulf of Maine region reveal changes in winter baroclinic circulation between cool and warm decades, with greater equatorward penetration of south-westwards flow along the shelf-edge during the cool 1960s. Over the period 1934–77, the NAO is found to account for 17% of the interannual variance in Labrador Current transport around the Grand Banks.
Proxy evidence for the cold episode of the early 1880s is sought. Records of bottom temperature in the Middle Atlantic Bight region are reconstructed using stable oxygen isotopic analysis on the annual bands of shells of a bivalve mollusc ( Arctica islandica ) and an empirical model of covariability with local air temperature. The result is confirmation of the presence of anomalously cold water during the early 1880s.     

A microcomputer program for stimulating effects of physical transport processes on fish larvae

A simple microcomputer program uses Lagrangian particle tracking to simulate the fates of individual larvae subject to wind- and tide-driven advection fields and diffusion. Space/time advection patterns are provided to the program as inputs; thus, the program can use results from various hydrodynamic models. The program can simultaneously track several groups of larvae that are assigned varying attributes, including (1) body size, to allow simulation of effects of variation in growth rates; (2) spawning locations and times; (3) vertical migration behavior; and (4) settlement strategy (duration of larval period, depth conditions for settlement). The model is intended as an exploratory tool to help identify alternative hypotheses that might explain observed life history patterns and causes of inter-annual variation in recruitment rate. For English sole in the Hecate Strait, B.C., the model leads us to hypothesize that observed spawning locations have resulted from a tradeoff between places that would provide the best feeding opportunities and places that would minimize risk of advective export to unfavorable rearing habitats.     

Larval lobster (Homarus americanus) distribution and drift in the vicinity of the Gulf of Maine offshore banks and their probable origins

Surveys for lobster larvae in offshore waters of the north‐eastern Gulf of Maine in 1983, 1987 and 1989 confirm that local hatching occurs mainly at depths <100 m over the banks, including Georges and Browns Banks. Detailed studies in the vicinity of Georges Bank in late July of both 1987 and 1989 indicate that the first and second moult stages were located primarily over the bank whereas stages III and IV lobster were collected both over and off the bank. At times stage IV lobster were more abundant off the bank than over it. The condition of stage III and IV lobster, as measured by a lipid index, was better off than over Georges Bank in 1988 and 1989 indicating a possible physiological advantage to being off the bank. In addition, the higher surface temperatures off Georges Bank would shorten larval development time to settlement. To determine the probable hatch sites of stage IV lobster collected off of Browns Bank in 1983 and off of Georges in 1987 and 1989, a 3‐D circulation model of the Gulf of Maine was used to simulate larval lobster drift backwards in time. In all cases, areas off Cape Cod, MA, and off Penobscot Bay, ME were suggested as the source of the larvae, although most of the larval trajectories never reached these near‐shore waters that are well‐known, larval hatching areas. The model‐projected larval release times match most closely the observed inshore hatch off Massachusetts but model uncertainties mean that coastal Maine cannot be ruled out as a source. Georges Bank is also a potential source because the present model does not take into account short‐term wind events, off‐bank eddy transport or the possibility of directed off‐bank larval swimming. Examination of weather records prior to and during our 1988 and 1989 sampling periods indicates that winds were not of sufficient intensity and duration to induce larval transport off Georges Bank. The shedding of eddies from the northern flank of Georges Bank into the Gulf of Maine are a relatively common phenomenon during summer but not enough is known about them to evaluate their contribution to possible cross‐bank transport of lobster larvae. Directed larval swimming is another possible source for the stage IV lobster found near Georges Bank. Plankton distributions across the northern frontal zone of Georges Bank in 1988 were used as proxies for the scarce larval lobsters. The more surface distribution of the microplankton, in particular, supports the possibility that wind and eddy events may be important in the transport of stage III and IV lobsters off of Georges Bank. Further studies are needed to evaluate these possible additional sources of advanced stage lobster larvae found off of the offshore banks.     

Reaction of somaclonal variants of wheat to the take-all fungus (Gaeumannomyces graminis var. tritici)

More than 20000 wheat plants, derived from callus culture of immature wheat embryos were assessed for reaction to the take-all fungus ( Gaeumannomyces graminis var. tritici ) using a test-tube assay. Lines with less root and shoot blackening and more remaining green tissue than parental lines were identified in the SC₃ generation. However these lines had more root and shoot blackening and less remaining green tissue in subsequent generations. The changes in reaction to the fungus may therefore have been epigenetic. The potential of this tissue culture derived material for breeding take-all resistant wheats is discussed.     

Variation in the distribution of ocean shrimp (Pandalus jordani) recruits: links with coastal upwelling and climate change

In this analysis, an atypical northward shift in the distribution of age‐1 ocean shrimp (Pandalus jordani) recruits off Oregon in 2000 and 2002–2004 was linked to anomolously strong coastal upwelling winds off southern Oregon (42°N latitude) in April–July of the year of larval release (t?1). This is the first clear evidence that strong upwelling winds can depress local recruitment of ocean shrimp. Regression analysis confirmed a long‐term negative correlation between log_e of ocean shrimp recruitment and April sea level height (SLH) at Crescent City, California, in the year of larval release, for both northern and southern Oregon waters. The regional pattern of ocean shrimp catches and seasonal upwelling winds showed that, although the timing of the spring transition as reflected in April SLH drives ocean shrimp recruitment success off Oregon generally, the strength and consistency of spring upwelling limits the distribution of large concentrations of ocean shrimp at the southern end of the northern California/Oregon/Washington area. A northward shift in 1999 and 2001–03 in the northern edge of this ‘zone of maximum upwelling’ is the likely cause of the weak southern Oregon recruitment and resulting atypical distribution of ocean shrimp observed off Oregon in 2000 and 2002–04, with a return to a more typical catch distribution as spring upwelling moderated in subsequent years. It is noted that a northward shift in the conditions that produce strong and steady spring upwelling winds is consistent with many predictions of global climate models under conditions of global warming.