Symbiosis of Trifolium subterraneum with mycorrhizal fungi and Rhizobium trifolii as affected by ammonium sulphate and nitrification inhibitors

The symbioses between Trifolium subterraneum, mycorrhizal fungi and Rhizohium are affected by (NH₄)₂SO₄ and by the nitrification inhibitors 2-chloro-6 (trichloromethyl) pyridine (N-Serve) and 2-trichloromethyl pyridine (2TMP). At 50 μg · g^?1 soil N-Serve and 2TMP had toxic effects on plant growth, measured as leaf expansion, root length and dry weight. Lower concentrations of N-Serve also produced some toxic symptoms. The addition of (NH₄)₂SO₄ to the soil at 2 and 6 m-equiv NH⁺₄ per pot, resulted in reduced root length and nodulation. Shoot dry weight was reduced at 6 m-equiv NH⁺₄ per pot. In the presence of (NH₄)₂SO₄ the toxic effects of the nitrification inhibitors on plant growth were less.Both nitrification inhibitors reduced development of mycorrhizal entry-points and extent of root colonization (% infection). Percentage infection of the root system was also reduced by (NH₄)₂SO₄. Development of nodules on the lateral roots was increased in the presence of N-Serve at 5 and 15 μ · g^?1. This effect, however, was accompanied by a marked reduction in N₂ase activity. Smaller increases in nodulation were apparent with 2TMP and were associated with variable N₂ase activity.     

Detection of Salmonella in onion and garlic powders: collaborative study.

The relative efficiency of trypticase soy broth with added 0.5% K2SO3 and lactose broth as pre-enrichment media for recovering Salmonella from onion powder and garlic powder was collaboratively studied. For each spice, 13 collaborators each received 5 duplicate samples; 4 of the 5 replicate samples were inoculated with 1 of 4 levels of S. thompson ranging, at initiation of analysis, from greater than 3 to 93 organisms/g onion powder and greater than 3 to 43 organisms/g garlic powder. Salmonella growth was inhibited in each of these spices as evidenced by a rapid decline of most probable number values in samples determined immediately after and 7 days following inoculation. Collaborative results of cultural analyses demonstrated superiority of the modified tripticase soy broth for recovering Salmonella in each of the 2 spices. The improved method of detecting Salmonella in onion and garlic powders has been adopted as official first action.     

Limnology of Macrobrachium amazonicum grow‐out ponds subject to high inflow of nutrient‐rich water and different stocking and harvest management

We evaluated the water characteristics and particle sedimentation in Macrobrachium amazonicum (Heller 1862) grow‐out ponds supplied with a high inflow of nutrient‐rich water. Prawns were subject to different stocking and harvesting strategies: upper‐graded juveniles, lower‐graded juveniles, non‐graded juveniles+selective harvesting and traditional farming (non‐grading juveniles and total harvest only). Dissolved oxygen, afternoon N‐ammonia and N‐nitrate and soluble orthophosphate were lower in the ponds in comparison with inflow water through the rearing cycle. Ponds stocked with the upper population fraction of graded prawns showed higher turbidity, total suspended solids and total Kjeldahl nitrogen than the remaining treatments. An increase in the chemical oxygen demand:biochemical oxygen demand ratio from inlet (4.9) to pond (7.1–8.0) waters indicated a non‐readily biodegradable fraction enhancement in ponds. The sedimentation mean rate ranged from 0.08 to 0.16 mm day^?1 and sediment contained >80% of organic matter. The major factors affecting pond ecosystem dynamic were the organic load (due to primary production and feed addition) and bioturbation caused by stocking larger animals. Data suggest that M. amazonicum grow‐out in ponds subjected to a high inflow of nutrient‐rich water produce changes in the water properties, huge accumulation of organic sediment at the pond bottom and non‐readily biodegradable material in the water column. However, the water quality remains suitable for aquaculture purposes. Therefore, nutrient‐rich waters, when available, may represent a source of unpaid nutrients, which may be incorporated into economically valued biomass if managed properly.     

Variance estimation for population attributable risk in a complex cross-sectional animal health survey

Population attributable risk estimates offer a method of combining information on population exposure and disease risk factors into a single measure. Univariate and multivariable methods exist for calculating point estimates and variances under the assumption of equal sampling probabilities. National Animal Health Monitoring System national studies typically use a complex survey design (where selection probabilities vary by design strata), which makes use of these methods of calculating variance inappropriate. We suggest the use of a method called "delete-a-group" jackknife to estimate the variance of population attributable risk when a complex survey design has been implemented. We demonstrate the method using an example of Johne's disease. Advantages of the "delete-a-group" jackknife method include simplicity of implementation and flexibility to estimate variance for any point estimate of interest.     

Preparing the veterinary profession for corporate and trade issues in the Americas: proceedings of a conference on synergism and globalization, Santiago, Chile, May 6-8, 2001

The complex and rapid-paced development of international trade, coupled with increasing societal demands for the production not only of abundant and inexpensive food, but also of food that is safe and has been raised in a humane and environmentally friendly manner, demands immediate attention from the veterinary community. The new culture of global trade agreements, spurred by the development of the WTO, dictates massive changes and increasing integration of public and private sectors. This is a huge growth area for our profession and will require individuals with a skill set we do not yet provide in our educational framework. In North America, veterinary education is parochial and focused on specialization. This strong orientation toward companion animals fails to provide adequate training for those interested in acquiring the necessary skills for the emerging area of globalization and trade. In South America, curricula are less harmonized with one another and there is tremendous variation in degree programs, rendering it difficult to ascertain whether veterinarians are prepared to assume decision-making responsibilities regarding international transport of food. If we do not begin to prepare our graduates adequately for this emerging market demand, the positions will be filled by other professions. These other professions lack broad-based scientific knowledge about animal physiology and disease causation. Decisions made without adequate background could have devastating consequences for society, including incursions of unwelcome diseases, food safety problems, and public health issues. To prepare our new veterinary graduates for the future and this emerging market, it is important to nurture a global mindset within our academic communities and to promote communications, languages, and an interdependent team mentality. Areas of technical expertise that need a place, perhaps a parallel track, in the curriculum include production medicine, public health, food safety, and international veterinary medicine. The major trade corridors of the future regarding animal-based protein flow between North and South America. It is absolutely essential that we find areas of consensus and deficiencies so that we can harmonize our trade agreements and ensure adequate flow of safe food products from one continent to the other.     

Radiographic anatomy of the thoraco-abdominal cavity of the ostrich (Struthio camelus)

This study provides a reference for the radiographic anatomy of the thoraco-abdominal cavity of female ostriches as a representative of ratites. One ostrich cadaver, 2 adult and 2 growing ostriches were used. Right lateral radiographs produced by a 6-frame technique and 2 dorsoventral radiographs produced by an adapted 3-frame technique were selected and schematic illustrations of these were labelled to illustrate normal radiographic anatomy. Differences from other avian species and unique features of the ostrich are briefly discussed.