Influence of concentrate composition and forage type on retail packaged beef quality

The objective of this study was to determine the effect of type of conserved forage and concentrate composition on the quality of beef held in overwrapped (aerobic) or modified atmosphere packaging under simulated retail display for 17 d. Friesian steers (n = 45) were assigned randomly to one of five dietary treatments: 1) extensively fermented grass silage plus silage concentrate (EFS); 2) restricted fermented grass silage plus silage concentrate (RFS); 3) starch-based concentrate plus wheat straw (SC); 4) nonstarch-based concentrate plus wheat straw (NSC); or 5) zero-grazed perennial ryegrass plus grass concentrate (RYE). Meat quality was determined by measuring color, lipid oxidation (TBARS), alpha-tocopherol concentrations, and fatty acid composition. In aerobically packaged beef, there was a display x diet interactive effect (P < 0.001) on Hunter a* values, with steaks from the EFS group having higher (P < 0.05) a* values than all other dietary groups from d 6 through d 17. Moreover, during the last 12 d of display, beef from the EFS group had the lowest (P < 0.01) proportion of metmyoglobin (display day x diet; P < 0.001). Under aerobic packaging, the SC and NSC groups produced steaks with higher (P < 0.05) TBARS values than RFS, EFS, and RYE groups, which did not differ from each other (display day x diet; P < 0.01). The SC and NSC groups had higher (P < 0.05) oxidation levels than RFS, EFS, and RYE groups, which did not differ from each other. Beef from the EFS group had (P < 0.05) higher concentrations of alpha-tocopherol than from the SC, NSC, and RYE groups. Beef from EFS-fed steers had a higher (P < 0.05) proportion of saturated fatty acids than the SC and NSC groups. It was concluded that the method of grass conservation influenced beef color, whereas concentrate composition did not. Color of aerobically packaged beef was improved by feeding animals silage that had undergone extensive fermentation. Conversely, oxidative stability was decreased by feeding animals starch- and nonstarch-based concentrate diets.     

Comparison of two atmospheric-dispersion models to assess farm-site exposure to sour-gas processing-plant emissions

We describe two approaches for exposure assessment that we used in a large-scale retrospective cattle study conducted in Alberta, Canada. Sulfur dioxide (SO(2)) was the surrogate measure of exposure to a complex mixture of combusted sour-gas emissions. Monthly air pollution dispersion modeling (1985-1994) (based on individual industrial source processing-plant engineering specifications, emission volumes, and meteorologic information) provided exposure isopleths of sulfur dioxide concentration from each of 231 sour-gas processing-plants across the province. In contrast, a simpler measure of proximity to source(s) of varying emission rates was applied in a geographical information system based on simplified pollution decay at increasing distances from each point source. Province-wide (663,000 km(2)) surface analysis (by exposure-level classification) produced a contingency coefficient of 0.68 between the two exposure estimates. Annual exposure estimates at the 1382 dairy and 5726 beef cow-calf farms studied were highly correlated over the 10-years period (r(spearman)=0.82 and 0.83, respectively), while monthly exposure estimates were somewhat less correlated (r(spearman)=0.80 and 0.82, respectively) for the two exposure assessment methods. Crude exposure estimates from each method were similar in both direction and magnitude.     

A PCR diagnostic assay for rapid detection of plant pathogenic pseudomonads

Molecular detection of phytopathogens is increasingly being applied to identify regulated organisms at the border in many parts of the world. However, even with molecular tests, complete phenotyping and identification of a strain is often time consuming and sometimes inconclusive. In this study, a leaf-based pathogenicity test was used to separate pseudomonads into two groups, Group A containing pathogens, and Group B containing saprotrophs. Comparative genomics of 56 pseudomonad genomes from different plant hosts (including 29 strains from kiwifruit) agreed with kiwifruit pathogenicity test results, placing pathogens into Group A and saprotrophs into Group B. Sixteen loci were found unique to Group A. A PCR assay was developed for amplification of one of these loci, the trehalose phosphatase gene. The generation of this 655 bp amplicon was associated with production of water-soaked lesions on inoculated kiwifruit leaves by pseudomonads in Group A. This test was validated for further strains from all seven pathogenic Pseudomonas phylogroups, non-pathogenic pseudomonads, and other bacterial genera. The sensitivity of the PCR was comparable to the limit of recovery of pseudomonads by culturing. This simple PCR assay could be used as part of a testing pipeline at the border and for general surveillance for screening plants with and without symptoms, offering the potential to detect uncharacterized pseudomonads that may pose a biosecurity risk. The method was shown to be able to rapidly identify pathogens cultured from plant material with symptoms, or, more importantly, to detect pathogens directly from plant tissue.     

The Importance of Rhizosphere Interactions in the Biological Control of Plant Parasitic Nematodes—a Case Study using Verticillium chlamydosporium

Verticillium chlamydosporium has provided considerable control of root knot nematodes in a range of laboratory experiments and is one of the most promising natural enemies with potential as a biological control agent so far tested. From a detailed study of the biology and ecology of the fungus, it has been possible to identify the key factors which affect its efficacy and a strategy for its exploitation has been developed. The fungus survives in soil throughout a growing season and its concentration in soil may be increased by repeated applications. The rapid multiplication of root-knot nematodes on susceptible crops means that control must be extremely effective to prevent crop damage. If suitable methods of production and application can be developed, V. chlamydosporium, in conjunction with other methods such as the rotation of poor hosts, may provide adequate control, but the reliability of such approaches needs extensive testing. Although genetic manipulation offers the possibility of enhancing the ability of the fungus to kill nematodes, such an approach will require much research and, in the short term, the development of the fungus will rely on the exploitation of carefully selected wild types.     

Development of a new management strategy for the control of root-knot nematodes (Meloidogyne spp) in organic vegetable production

The nematophagous fungus, Pochonia chlamydosporia (Goddard) Zare & Gams, has been investigated as a potential biological control agent for use in integrated pest management strategies for Meloidogyne incognita (Kof & White) Chitwood in vegetable crops. The release of the fungus as a biological control agent requires a diagnostic method to monitor its spread in the environment and to gain knowledge of its ecology. Only molecular methods are sufficiently discriminating to enable the detection of specific isolates of fungi in soil. A method to extract DNA from soil was developed to increase the efficacy of PCR-based diagnostic tests that use specific primers. A selected isolate of P chlamydosporia var catenulata was applied at densities similar to those that occur naturally in nematode-suppressive soils. The fungus significantly reduced nematode infestations in soil following a tomato crop, in a strategy that combined the use of the fungus with crop rotation. The survival of the fungus in soil was also examined in controlled conditions in which it remained in soil in densities significantly greater than its original application rate for at least 5 months. Hence, it seems that populations of this fungus may be built up in soil and have significant effects on the regulation of root-knot nematode populations.     

Channels within soft wheat starch A- and B-type granules

The nature of channels within wheat starch granules was investigated using scanning electron and confocal laser scanning microscopy. A-type granules stained with 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde (CBQCA, protein-specific probe) revealed a network of radially oriented, channel-like protein structures similar to those previously reported. However, treatment of the same starch granules with methanolic merbromin (fluorescent dye) solution, which is used to highlight external granule surfaces (including those of channels) under non-swelling conditions, revealed few, if any, channels extending into the granule interior. This discrepancy suggested that channels within wheat starch granules were filled at least in part with protein. Removal of protein with protease facilitated greater access of methanolic merbromin to channels and/or cavities for both granule types. For A-type starch granules, relatively large channels were observed in the equatorial groove region, while finer channels originated from other regions of the granule. This work reports the first visualization of B-type granule channels, which most frequently occurred as less-defined voids (as opposed to the fine, discrete channels of A-type granules) extending to granule surfaces. Channels of A- and B-type starch granules appeared to facilitate transfer of chemical reagent into the granule matrix, though this effect was aided by granule swelling (hydration) and/or removal of channel-associated protein.     

The isolation of ovine lymphocytes and granulocytes from whole blood using hydroxyethylcellulose.

Sheep erythrocytes do not aggregate spontaneously but will sediment when mixed with a solution of hydroxyethylcellulose. The resulting leucocyte-rich supernatant can be used in the preparation of purified lymphocyte and granulocyte suspensions.     

Mars' south polar Ar enhancement: a tracer for south polar seasonal meridional mixing

The gamma ray spectrometer on the Mars Odyssey spacecraft measured an enhancement of atmospheric argon over southern high latitudes during autumn followed by dissipation during winter and spring. Argon does not freeze at temperatures normal for southern winter (approximately 145 kelvin) and is left in the atmosphere, enriched relative to carbon dioxide (CO2), as the southern seasonal cap of CO2 frost accumulates. Calculations of seasonal transport of argon into and out of southern high latitudes point to meridional (north-south) mixing throughout southern winter and spring.