Seroprevalence of Ornithobacterium rhinotracheale infection in commercial laying hens in the north central region of the United States.

This study was the first to examine the seroprevalence of Ornithobacterium rhinotracheale (ORT) within a commercial egg layer population. Serum samples collected from egg production companies were examined by serum plate agglutination test (SPAT) and outer membrane protein-based enzyme-linked immunosorbent assay (ELISA). Results show that 90% of layer flocks were positive by SPAT and 100% by ELISA. Of the pullet flocks examined, 43% and 52% were positive by SPAT and ELISA, respectively. Our study indicates that the prevalence of ORT antibody is high in the commercial layer population, suggesting that this respiratory pathogen can easily spread through multiple-age layer farms from older flocks to newly housed pullet flocks.     

Chironomid farming — A means of recycling farm manure and potentially reducing water pollution in Hong Kong

In Hong Kong, chironomid larvae are grown on chicken manure. The larvae are used in large quantities as live food for aquarium fish and carnivorous fish fry in fish culture. In this survey, the culture technique and yield of chironomid farming were studied. The technique is simple: at temperatures of 15–30°C the yield is about 140 kg in a 675 m² field per cycle of 50 days. Since a large quantity of chicken manure, about 1440 kg, is consumed in each cycle, and there is also the possibility of using other farm wastes to grow chironomid larvae, this highly profitable chironomid farming may be developed to reduce the problem of stream pollution due to the farm wastes.     

Sodium bicarbonate as an extractant for soil phosphate III. Effects of the buffering capacity of a soil for phosphate

An index of the buffering capacity for phosphate of a group of soils was obtained by measuring adsorption of phosphate from dilute solutions of calcium chloride. The effect of buffering capacity on the amount of phosphate initially displaced by solutions of sodium bicarbonate and on the amount of secondary adsorption from bicarbonate was then studied. These two effects were separated using a regression procedure in which the soil: solution ratio was the independent variable.As buffering capacity increased the amount of phosphorus initially displaced decreased and the amount of secondary adsorption increased. Both these changes resulted in a decrease in the amount of phosphate in the extract. The effect of buffering capacity was greater with the Olsen method (soil : solution ratio 1 : 20; 30 min) than with the Colwell method (soil : solution ratio 1 : 100; 16 h). The relation between phosphorus extracted and buffering capacity was of a similar shape to that between effectiveness of fertilizer and buffering capacity. However, the first relation depends on the conditions of extraction and the second on the kind of plant grown and on the conditions of growth. Hence the two relations do not necessarily coincide.The effect of buffering capacity on the proportion of added phosphate initially displaced from the soil became more marked as the period of incubation prior to extraction was increased. Bicarbonate soil tests would therefore indicate that, on soils of low buffering capacity, the decrease with time in availability of applied phosphate would be smaller than on soils of high buffering capacity. This effect differs from that observed with plants.     

THE SIMULATION OF ANIMAL RETURNS IN GRASSLAND EXPERIMENTATION

An experiment was carried out on a grass/white-clover sward at North Wyke to evaluate the use of mixtures of inorganic and organic nutrient sources to simulate the nutrient effect of animal excreta, both with and without overall PK fertilizer. Grazing with sheep and the return of excreta from caged sheep both increased herbage yields, as did artificial return treatments. Artificial return treatments giving 75% of the nutrient level returned by excreta gave yields comparable with grazing. The effect of the simulated return treatments was not influenced by PK application. Grazing gave a very different botanical composition to that from the treatments in wbich natural or simulated excreta were returned to cut swards. Mixtures simulating excreta may replace the nutrient effect of the grazing animal, but not its physical effect, in some forms of grassland experimentation. They are not recommended for fertilizer trials.     

FERTILIZER N AND THE YIELD OF CUT GRASS SWARDS IN EASTERN ENGLAND

Single spring dressings of N were compared with split applications over the first two growth periods of the year at ten sites in eastern England in the period 1964–67. None of the four spring periods was unusually dry and the single application of N in spring did not outyield a similar total N rate applied some before and some after the first cut. At nine out of ten sites split applications of N yielded considerably more in the second growth period than the single spring dressing. It is concluded that the split applications of N in the spring, already shown superior to single dressings under moist west country conditions, are correct for many seasons in the drier east of England.     

Identification of infrared absorption spectral characteristics of synovial fluid of horses with osteochondrosis of the tarsocrural joint

OBJECTIVE: To determine the feasibility of the use of Fourier-transform infrared (FTIR) spectroscopy within the midinfrared range to differentiate synovial fluid samples of joints with osteochondrosis from those of control samples. ANIMALS: 33 horses with osteochondrosis of the tarsocrural joint and 31 horses free of tarsocrural joint disease. PROCEDURES: FTIR spectroscopy of synovial fluid was used. Sixty-four synovial fluid samples from the tarsocrural joint were collected. Of these, 33 samples were from horses with radiographic evidence of osteochondrosis of the tarsocrural joint and 31 from control joints. Disease-associated features within infrared spectra of synovial fluid were statistically selected for spectral classification, and the variables identified were used in a classification model. Linear discriminant analysis and leave-one-out cross-validation were used to develop a classifier to identify joints with osteochondrosis. RESULTS: 12 significant subregions were identified that met the selection criteria. The stepwise discriminant procedure resulted in the final selection of 6 optimal regions that most contributed to the discriminatory power of the classification algorithm. Infrared spectra derived from synovial fluid of joints with osteochondrosis were differentiated from the control samples with accuracy of 77% (81% specificity and 73% sensitivity). CONCLUSIONS AND CLINICAL RELEVANCE: The disease-associated characteristics of infrared spectra of synovial fluid from joints with osteochondrosis may be exploited via appropriate feature selection and classification algorithms to differentiate joints with osteochondrosis from those of control joints. Further study with larger sample size including age-, breed-, and sex-matched control horses would further validate the clinical value of infrared spectroscopy for the diagnosis of osteochondrosis in horses.     

Prediction of leaching fraction from soil properties,irrigation water and rainfall

Summary Fine textured soils (> 40% clay) form a major proportion of irrigated soils in northeastern Australia. More than half these soils are irrigated with groundwater, some of which has high salinity (electrical conductivity > 2.9 mS cm^–1). A simple prediction of salt leaching was sought to aid in land management decisions.An empirical model of leaching fraction is presented based on rainfall and easily measured soil properties related to hydraulic conductivity. The model is based on data from 766 soils. To account for the complexity of interactions between soil properties, the data was stratified into groups based on clay content and mineralogy (expressed here as CEC/clay ratio). This allowed simple linear regressions using ESP and rainfall to be developed to predict leaching fraction.When applied to irrigated soils, a salinity correction term (EC_{rain+irrigation}/EC_rain) was used to account for the flocculation effects of the increased salinity of irrigation waters. The model gave good predictions of leaching fraction for two irrigation regions with widely differing soil properties (Fig. 4).     

Assessing the efficacy and impact of management of an invasive species in a protected area: Poa annua on sub‐Antarctic Macquarie Island

Plant eradication is difficult, particularly in remote, protected areas. The Southern Ocean Islands are very isolated and highly protected, but the flora contains many alien plants. Small restricted populations have been eradicated, but eradication of established species has proven difficult. A better understanding of the efficacy of control methods at sub‐Antarctic temperatures and their off‐target impacts may increase eradication success. With interest in controlling non‐native Poa annua in the region, we aimed to determine if physical and chemical methods can control P. annua (the sub‐Antarctic biotype) in sub‐Antarctic conditions and examined their impact on native plants. We quantified the effectiveness of physical control methods on P. annua in situ on sub‐Antarctic Macquarie Island through field‐based experiments and assessed their selectivity on P. annua compared with native grasses. We also quantified the effectiveness of several herbicides on P. annua at sub‐Antarctic temperatures and assessed their selectivity on native grasses. Of the four physical disturbance methods tested, none effectively reduced P. annua cover as one‐off treatments. Of the herbicide treatments, glyphosate and trifloxysulfuron sodium were effective and were less damaging to native grass species, indicating potential selectivity. Physical control was of limited effectiveness, but did not affect native species richness. An integrated weed management programme utilising the strategic use of selective herbicides with follow‐up chemical and physical intervention may balance control and biodiversity outcomes. This research highlights the importance of site‐specific testing of control methods and understanding off‐target impacts of control when managing alien plant species in protected areas.