A. Donnison

Best management practices to mitigate faecal contamination by livestock of New Zealand waters

Abstract This paper summarises findings from the Pathogen Transmission Routes Research Program, describing pathogen pathways from farm animals to water bodies and measures that can reduce or prevent this transfer. Significant faecal contamination arises through the deposition of faeces by grazing animals directly into waterways in New Zealand. Bridging of streams intersected by farm raceways is an appropriate mitigation measure to prevent direct deposition during herd crossings, whilst fencing stream banks will prevent access from pasture into waterways by cattle that are characteristically attracted to water. Riparian buffer strips not only prevent cattle access to waterways, they also entrap microbes from cattle and other animals being washed down‐slope towards the stream in surface runoff. Microbial water quality improvements can be realised by fencing stock from ephemeral streams, wetlands, seeps, and riparian paddocks that are prone to saturation. Soil type is a key factor in the transfer of faecal microbes to waterways. The avoidance of, or a reduction in, grazing and irrigation upon poorly drained soils characterised by high bypass flow and/or the generation of surface runoff, are expected to improve microbial water quality. Dairyshed wastewater should be irrigated onto land only when the water storage capacity of the soil will not be exceeded. This “deferred irrigation” can markedly reduce pollutant transfer to waterways, particularly that via subsurface drains and groundwater. Advanced pond systems provide excellent effluent quality and have particular application where soil type and/or climate are unfavourable for irrigation. Research needs are indicated to reduce faecal contamination of waters by livestock.

Factors affecting microbial spoilage and shelf-life of chilled vacuum-packed lamb transported to distant markets: A review

Vacuum-packaging and stringent control of storage temperatures enable the export of meat to distant markets, supplying a chilled product that can favourably compete with local fresh meats. To save fuel and reduce emissions, the speed of ships travelling to international markets has decreased resulting in requirement for the shelf-life of chilled lamb to be extended beyond the recognised time of 60-70 days. Growth of microorganisms and ability to cause spoilage of vacuum-packed lamb are dependent on many factors, including the type and initial concentration of spoilage bacteria, meat pH, water activity, availability of substrates, oxygen availability and, most importantly, storage time and temperature of the packaged product. This paper reviews the existing knowledge of the spoilage bacteria affecting vacuum-packed lamb, discusses the impact of these bacteria on product quality, shelf-life and spoilage, and concludes that under specified conditions the shelf-life of chilled lamb can be extended to beyond 70 days.

Attenuation of effluent‐derived faecal microbes in grass buffer strips

Abstract A series of field experiments assessed the ability of sloping (8°) 5‐m‐long by 2‐m‐wide grass buffer strips to trap the faecal microbes Escherichia coli and Campylobacter. The microbes, applied within dairy‐farm effluent, were washed into the strips by surface runoff generated at rates of 4–13 litres/min using a water sprinkler system. The effluent and surface and subsurface outflows at the lower end of each plot were sampled for microbial analysis. Flow rate influenced the timing of peak microbial concentration in outflow and the recovery of both microbes. Under high flow, recovery rates varied from 15–100%, and hence entrapment was often minimal. Under the slowest rate of water application, entrapment was much greater (≥95%), at least over the 40 min of water application. During large runoff events, and where preferential flowpaths occur, buffer strips need to exceed 5 m in length in order to markedly reduce the delivery of faecal microbes to waterways. Of those microbes trapped in the grass strips under fast flow rates, some were remobilised and washed out following a subsequent runoff event, 5 days later. On occasion, a considerable volume of flow was observed to bypass beneath the subsurface collecting troughs, probably reducing the effectiveness of the buffer strips.

Campylobacter and farm dairy effluent irrigation

Abstract Campylobacter were studied at a mole‐tile drained farm over a 12‐month period. Farm dairy effluent was applied to the farm in January, October, and November. In January, herd 1 was on the farm and effluent that contained 103 campylobacter 100 ml−1 was sourced from a storage pond. In October and November herd 2 was on the farm and effluent that contained 105 and 106 campylobacter 100 ml−1 respectively was sourced from the dairy shed. In January and November, when irrigation caused preferential flow, concentrations in the drainage water were similar to those in the applied effluent, creating a potential for water contamination. C. jejuni was the predominant campylobacter species recovered. Only one subspecies type (i.e., one Penner serotype and one PFGE type) was observed in the effluent, drainage water, and soil samples collected after the January application. This recovery of a single subtype allowed tracing from effluent into drainage water and soil. In contrast, several subspecies types were observed after the October and November applications, and the study demonstrated that when there is a diversity of subtypes, typing was less effective as a means of tracking campylobacter. Penner serotyping of C. jejuni in these effluents revealed serotypes linked to the human illness, campylobacteriosis.

Survival and retention of Eschenchia coli O157:H7 and Campylobacter in contrasting soils from the Toenepi catchment

Abstract The effect of soil type on transfer of zoonotic bacteria to rural streams was investigated using intact cores and turfs of Topehaehae gley soil and Kereone sandy loam. Simulated farm dairy effluent, containing laboratory grown Escherichia coli O157:H7 and Campylobacter, was added to cores and turfs that were stored at 10°C. Bacterial survival was measured in cores over 28 days. Simulated rainfall was applied at 25 and 50 mm h‐1 to allow measurement of bacterial transfer to drainage (over 28 days) or surface runoff (at 7 days). Although both bacteria survived for 28 days, Campylobacter declined faster than E. coli O157:H7 with no differences identified for soil type. For Topehaehae soil there was little change in retention of E. coli O157:H7 over the 28 days for both rainfall rates, but there was an increase in retention over time for Kereone. In contrast there was an increase in retention of Campylobacter in both soils at either of the rainfall rates. When surface runoff was measured, less than 1% of each of the applied bacteria was recovered from either soil irrespective of rainfall rate. These findings suggest that rainfall will transfer faecal bacteria from gley soils bordering a stream to the water for at least 28 days after deposition.

Control of gaseous emissions of ammonia and hydrogen sulphide from cow manure by use of natural materials

Abstract Winter management practices involving the use of stand‐off pads to reduce problems due to cows grazing on wet soils may require storage of cow manure for extended periods prior to field application. Gaseous losses of nitrogen (N) and sulphur (S) from stored cow manure can be considerable, and these gases are offensive and undesirable. Laboratory incubation studies were conducted to measure gaseous loss of ammonia (NH3) and hydrogen sulphide (H2S) from stored cow manure under aerobic and anaerobic conditions. The potential of adding a range of natural materials, including soil, untreated pine bark, sawdust and wood savings, to the manure to reduce these gaseous emissions was investigated. Aerobic incubation of manure resulted in a higher emission of NH3 than anaerobic incubation, while anaerobic incubation resulted in higher emissions of H2S. The effectiveness of natural materials in reducing losses of NH3 was investigated under anaerobic conditions, and pine bark was found to be the most effective. However, all materials reduced NH3 to some degree. Therefore, the addition of natural materials, such as pine bark and soil, as amendments to cow manure during storage offers potential for reducing emissions of NH3 and H2S.

Escherichia coli shedding by dairy cows

Abstract Eight non‐lactating Friesian cows participated in two metabolic balance trials in which they were fed pasture‐silage over 8 days and 6 days respectively. All daily faeces from each cow were collected and analysed for Escherichia coli. On two occasions E. coli was also measured in freshly voided faeces from 21 Friesian cows that grazed fresh pasture. The amount of faeces shed by the silage‐fed cows was relatively constant (average 25.8 kg cow‐1 day‐1 (wet weight); SD 4.86 kg) but E. coli concentrations were very variable and no E. coli were recovered from 14% of daily samples. Variation for a single cow was within 2 log10 but between cows it was up to 4 log10. The overall average concentration was 1.1 × 103 E. coli g‐1. The overall average shedding rate (wet weight) was 2.6 × 107 E. coli cow‐1 day‐1 and for individual cows it ranged from 5.0 × 105 to 3.9 × 109 E. coli cow‐1 day‐1. E. coli concentrations were also variable (by up to 3 log10) for the pasture‐fed cows, and their overall average was 2.9 × 104 E. coli g‐1 (no sample had <10 E. coli g‐1). These findings demonstrate that E. coli shedding by dairy cows is very variable and may be influenced by factors such as diet.

Sawdust and bark to treat nitrogen and faecal bacteria in winter stand‐off pads on a dairy farm

Abstract New Zealand farmers are increasingly using improved management systems including moving animals out of paddocks to protect wet soils from damage during winter. The cows can be held for up to 20 h a day on specially constructed unroofed outdoor stand‐off pads. Afield study was undertaken to investigate excreta nitrogen (N) transformations, N and faecal bacterial transport to drainage, and denitrification N losses when Pinus radiata bark or sawdust were used as filling materials in stand‐off pads. About 3 months after use only 4.0% of the N that was deposited on the bark or sawdust pad by cows had been transported to the drainage. Sim ilarly, after the 3 months of use only 9.8% of the Escherichia coli bacteria that were deposited on the bark pad had been transported to the drainage and with even less, 0.3%, leached from the sawdust pad. The sawdust pad tended to retain more Campylobacter than the bark pad. About 6 months after use, gaseous N losses due to denitrification from the sawdust or bark pad accounted for about 4.5 and 1.7% of the deposited excreta N, respectively. Denitrification activity was limited by the available nitrate in the pad materials, and decreased after cows were moved out of the pads.

Bacterial survival and dispersal in spray irrigation aerosols

Abstract New Zealand environmental authorities favour land‐based treatment for wastewaters of faecal origin. However, microbial aerosols from spray irrigation could be a health risk. This study investigated bacterial survival in irrigation aerosols in 105 field trials in spring and summer. Serratia entomophila and tracer spores of Bacillus subtilis var. niger were added to well water at about 105 ml−1 and sprayed onto a flat paddock through either a high‐pressure horticultural sprayer (1400 kPa) to maximise aerosol production or a low‐pressure hammer‐head rotary sprayer (300 kPa), commonly used for irrigation. Aerosol particles were collected in six‐stage Andersen air samplers. Recovery of viable B. subtilis spores decreased with increasing distance from the sprayers, due to dispersion. There was a greater decrease for S. entomophila. Assuming similar dispersion of both micro‐organisms, the relative decrease in S. entomophila was due to inactivation and this inactivation correlated with decreasing relative humidity. Under the prevailing meteorological conditions, viable S. entomophila were dispersed to at least 100 m from the low‐pressure sprayer and 200 m from the high‐pressure sprayer. Irrespective of sprayer type, sampling distance or micro‐organism, the majority of viable organisms were collected on those Andersen sampler stages corresponding to the respirable fraction of inhaled air.

Effect of using a stand-off pad on Campylobacter jejuni strain diversity in a herd of dairy cows

Aim:  To determine the effect of stand‐off pad (SOP) use on the prevalence and strain diversity of Campylobacter jejuni in a small herd of dairy cows.