Production of recycled manure solids for use as bedding in Canadian dairy farms: II. Composting methods.

Recent technological advances in the dairy industry have enabled Canadian farms with liquid manure systems to use mechanical solid-liquid separation paired with composting of the separated solids for on-farm production of low-cost bedding material. However, because several approaches are available, it is difficult for farmers to select the appropriate one to achieve high quality recycled manure solids (RMS). Whereas 3 solid-liquid manure separators were compared in part I of the series (companion paper in this issue), the present study (part II) aims to assess the performance of 4 composting methods (static or turned windrow and drum composter for 24 or 72 h) under laboratory conditions. Parameters evaluated included temperature, physico-chemical characteristics, and bacterial composition of RMS, as well as airborne microorganisms, dust, and gases associated with composting RMS. Because each treatment attained the desired composting temperature range of 40 to 65°C (either in heaps or in the drum composter), reductions in bacteria were a better indicator of the sanitation efficiency. The treatment of fresh RMS in a drum composter for 24 h showed decreased bacterial counts, especially for Escherichia coli (from 1.0 × 105 to 2.0 × 101 cfu/g of dry matter) and Klebsiella spp. (from 3.2 × 104 to 4.0 × 102 cfu/g of dry matter). Increasing the time spent in the rotating vessel to 72 h did not result in further decreases of these pathogens. Composting in a static or turned windrow achieved similar E. coli and Klebsiella spp. reductions as the 24-h drum composting but in 5 or 10 d, and generally showed the lowest occupational exposure risk for dairy farmers regarding concentrations of airborne mesophilic bacteria, mesophilic and thermotolerant fungi, and total dust. Drum-composted RMS stored in piles exhibited intermediate to high risk. Composting approaches did not have a major influence on the physico-chemical characteristics of RMS and gas emissions. Drum composting for 24 h was the best compromise in terms of product quality, temperature reached, decreased bacterial numbers, and emitted airborne contaminants. However, because levels of pathogenic agents rapidly increase once composted RMS are spread in stalls, bacteriological characteristics of RMS along with milk quality and animal health and welfare features should be monitored in Canadian dairy barns applying recommended separation (part I) and composting (part II) systems to evaluate health risk and optimize management practices.

Production of recycled manure solids for bedding in Canadian dairy farms: I. Solid-liquid separation.

Canadian dairy producers have an increasing interest in recycled manure solids (RMS) as bedding material because of reduced availability of traditional bedding resources. Information regarding methods to obtain RMS and composition of RMS is very limited. Hence, a 2-part investigation was developed to compare the performances of 3 mechanical solid-liquid manure separators (part I) and 4 composting methods (part II; companion paper in this issue) for the production of high quality RMS. In this first study, a roller press, a screw press, and a decanter centrifuge were tested for the separation of slurry manure from a commercial dairy farm. During the experiment, the quantity of slurry manure processed and the volume and mass of the liquid and solid fractions were measured. The energy consumption of each separator was recorded, and samples of the slurry, liquid, and solid effluents were collected for analysis. The type of separator did not significantly influence the chemical and bacteriological composition of RMS produced. The choice of a separator for Canadian dairy producers should thus be based on the equipment cost and its capacity, targeted solids dry matter (DM) content and structure, and fertilizing quality of the separated liquid. The decanter centrifuge produced the solid phase with the highest DM and best separation efficiencies for DM, N, and P. However, its low production capacity (1.5 m3/h vs. 9.1-20.3 m3/h) combined with its high acquisition cost (Can$145,000 vs. Can$75,000) and energy consumption (4.99 kWh/m3 vs. 0.10-0.35 kWh/m3) reduce its technical and profitability values. Besides, the centrifuge produced fine structured RMS and a low-quality liquid fraction, not suitable as dairy cow bedding and fertilizer, respectively. Both presses reached acceptable production capacity at a minimal operation cost. However, the poor performance in terms of DM (25%) of the model of screw press used in this study produced RMS unsuitable for immediate use without further processing. The model of roller press used in this study had the advantages of almost reaching the recommended DM content in RMS (>34%), being flexible in terms of inputs, and producing fluffy RMS. Nevertheless, its compression process seemed to allow greater passage of solids into the liquid fraction compared with the screw press. Part II of this work explores different composting methods to reduce the health risks associated with screw-pressed RMS before their use as bedding.

Associations between HIV-related injection behaviour and distance to and patterns of utilisation of syringe-supply programmes.

BACKGROUND: Studies indicate that needle-exchange programmes (NEPs) can reduce the incidence of HIV infection; however, a positive impact of syringe-supply programmes has not been consistently demonstrated. The associations between high-risk injection behaviour and distance to and patterns of utilisation of syringe-supply programmes in injection drug users (IDUs) were investigated. METHODS: Participants in a cohort of IDUs (n = 456) residing in Montreal were interviewed between 2004 and 2006. Behavioural questionnaires were administered by trained interviewers, and venous blood samples were drawn and tested for HIV antibodies. The distance from regular IDU dwelling places to nearest NEP or pharmacy was calculated using a Geographic Information System. Logistic regression was used to assess relations with high-risk injection behaviour. RESULTS: Associations between high-risk injection behaviour and distance to syringe-supply source were not linear. The odds of high-risk behaviour grew modestly as distance from the NEP site increased to 1600 m, followed by a flat trend to 3000 m, and thereafter decreased with distance beyond this point. The odds of high-risk behaviour dropped sharply for the relatively few IDUs residing 1 km or more from the nearest pharmacy but this measure was not strongly associated with the outcome. IDUs who exclusively acquired syringes at NEPs or pharmacies had less than half the odds of reporting high-risk injection behaviour than IDUs with inconsistent syringe-access patterns. CONCLUSIONS: The study confirms that Montreal NEPs were implemented where they are most needed. These results also suggest that sterile syringe acquisition patterns might influence high-risk injection behaviour.

Neighbourhood socioeconomic status, maternal education and adverse birth outcomes among mothers living near highways.

BACKGROUND: Residential proximity to highways is a potential proxy for exposure to traffic-related pollution that has been linked to adverse birth outcomes. We evaluated whether proximity to highway interacts with individual and neighbourhood socioeconomic status (SES) to influence birth outcomes. METHODS: The study population consisted of all live singleton births in Montréal, Canada, from 1997 to 2001 (n = 99,819). Proximity was defined as residing within 200 m of a highway. Neighbourhood SES was measured for census tracts as the proportion of families below the low-income threshold. Individual SES was represented by maternal education. Using multilevel logistic regression, the odds of preterm birth (PTB), low birthweight (LBW) and small-for-gestational-age (SGA) birth were calculated for mothers residing in proximity to highways, accounting for individual and neighbourhood SES. Effect modification between SES and proximity to highway was tested for each outcome. RESULTS: In wealthy neighbourhoods, proximity to highway was associated with an elevated odds of PTB (OR 1.58, 95% CI 1.23 to 2.04), LBW (OR 1.81, 95% CI 1.36 to 2.41) and SGA birth (OR 1.32, 95% CI 1.05 to 1.66). For highly educated mothers, proximity to highway was associated with PTB (OR 1.25, 95% CI 1.07 to 1.46) and LBW (OR 1.24, 95% CI 1.03 to 1.49), but the association was borderline for SGA birth (OR 1.15, 95% CI 1.00 to 1.32). Proximity to highway was not associated with birth outcomes in other maternal and neighbourhood SES categories. CONCLUSION: Counterintuitively, high SES mothers may be more likely than low SES mothers to experience adverse births associated with residential proximity to highway.

Evaluation of sorivudine (BV-araU) versus acyclovir in the treatment of acute localized herpes zoster in human immunodeficiency virus-infected adults. The Multinational Sorivudine Study Group.

The clinical efficacy and safety of sorivudine as treatment for acute cutaneous zoster in human immunodeficiency virus-infected adults was compared with that of acyclovir in a double-blinded randomized study. A total of 125 patients with laboratory-confirmed zoster rash present for < or =72 h were assigned treatment with either 40 mg of sorivudine once daily or 800 mg of acyclovir five times daily, both taken orally for 7 days. Patients were assessed daily until all lesions crusted and then monthly for 6 months for postherpetic neuralgia (PHN) and for 12 months for recurrent or new episodes of zoster. Sorivudine significantly shortened the median period of new vesicle formation from 3.0 to 4.0 days (log rank P = .0001). Sorivudine was effective regardless of duration of rash before treatment. Zoster recurrences and new episodes were experienced by fewer patients assigned sorivudine (11%) than acyclovir (26%, P = .037). No differences were seen in incidence, severity, or duration of either acute neuritis or PHN. Both treatments were well tolerated.