The performance of an efficient dairy system using a combination of nitrogen leaching mitigation strategies in a variable climate.

An efficient dairy system, that implemented a combination of nitrogen (N) leaching mitigation strategies including lower N fertilizer input, standing cows off pasture for part of the day in autumn and winter (stand-off), and importing limited amounts of low protein supplements was evaluated over four consecutive years of a farmlet study. This efficient system consistently demonstrated a lower measured annual N leaching of 40 to 50% compared with a baseline system representing current practice with no mitigations. To maximize return from this system fewer cows but of higher genetic merit were used resulting in an average decrease in milk production of 2% and operating profit by 5% compared with the baseline system. The magnitude of the N leaching reduction from mitigation strategies was predicted in pre-trial modelling. Using similar mechanistic models in a post-trial study, we were able to satisfactorily predict the trends in the observed N leaching data over the four years. This enabled us to use the calibrated models to explore the contributions of the different mitigation strategies to the overall leaching reduction in the efficient system. In one of the years half of the leaching reduction was achieved by the 'input' component of the strategy (less feed N flowing through the herd from lower fertilizer use, less grass grown, and low-protein supplement use), while the other half was achieved by the stand-off strategy. However, these contributions are determined by the weather of a particular year. We estimate that on average stand-off would contribute 60% and 'input' 40% to the reduction. The implication is that farmers facing nutrient loss limitations have some current and some future technologies available to them for meeting these limitations. A shift towards the mitigations described here can result in a downward trend in their own N-loss metrics. The challenge will be to negate any reductions in production and profit, and remain competitive.

The effect of cutting, mulching and applications of farmyard manure on nitrogen fixation in a red clover/grass sward.

In organic farming, maximising the amount of nitrogen (N) which is fixed and retained within the soil is of paramount importance for the yield of the following crop. The aim of this study was to establish the extent to which increased soil fertility, farmyard manure (FYM) applications and/or mulching, could adversely affect fixation. At two sites, situated in the South West (SW) and North East (NE) of England, N(2) fixation was estimated in 'organically' managed red clover/grass plots, both with and without green manure (i.e. surface mulched) and/or the addition of FYM. The FYM was incorporated into the seedbeds at both sites in autumn 2002 at the rate of 170 kg total Nha(-1), as either well-composted (SW site), or not actively-composted (NE site) manures. The same FYM application rate was repeated as top-dressings to both sites in autumn 2003. The plots were cut three or four times each year over two growing seasons. In the first harvest year (2003), incorporation of FYM had beneficial effects of increasing dry matter and N yields significantly at the first cut, but there were no significant differences in subsequent cuts. The same pattern was found in the second harvest year (2004) after the top dressings of FYM, suggesting that most of the N in both types of FYM was in recalcitrant forms. Over the two growing seasons, mulching did not affect red clover/grass dry matter or N yields, but did reduce the proportion of N(2) fixed, by up to 60 kg Nha(-1) when compared with plots from which the clover/grass herbage was cut and removed. Thus, the gain in N from FYM or green manure tended to be offset by a similar reduction in N(2) fixation. These results demonstrate the close association between the availability of soil N and the feed-back system which operates on N(2) fixation by red clover.

Effects of past sewage sludge additions on heavy metal availability in light textured soils: implications for crop yields and metal uptakes.

The effect of heavy metal additions in past sewage sludge applications on soil metal availability and the growth and yield of crops was evaluated at two sites in the UK. At Gleadthorpe, sewage sludges enriched with salts of zinc (Zn), copper (Cu) and nickel (Ni) had been applied to a loamy sand in 1982 and additionally naturally contaminated Zn and Cu sludge cakes in 1986. At Rosemaund, sewage sludges naturally contaminated with Zn, Cu, Ni and chromium (Cr) had been applied in 1968-1971 to a sandy loam. From 1994 to 1997, the yields of both cereals and legumes at Gleadthorpe were up to 3 t/ha lower than the no-sludge control where total topsoil Zn and Cu concentrations exceeded 200 and 120 mg/kg, respectively, but only when topsoil ammonium nitrate extractable metal levels also exceeded 40 mg/kg Zn and 0.9 mg/kg Cu. At Rosemaund, yields were only decreased where total topsoil Cu concentrations exceeded 220 mg/kg or 0.7 mg/kg ammonium nitrate extractable Cu. These results demonstrate the importance of measuring extractable as well as total heavy metal concentrations in topsoils when assessing likely effects on plant yields and metal uptakes, and setting soil quality criteria.

The prevalence and impact of dental pain in 8-year-old school children in Harrow, England.

OBJECTIVE: To assess the prevalence, severity and impact of dental pain. DESIGN: Cross-sectional survey. SETTING: Schools in the London Borough of Harrow, England, in the summer term of 1995. SUBJECTS AND METHODS: The base population were all 2,300 8-year-old school children in Harrow. A cluster sampling of schools based on quotas from all postcode areas in Harrow was used. Data were collected through interviews with the children. MAIN OUTCOME MEASURES: Prevalence of previous toothache; prevalence of toothache in the previous 4 weeks; prevalence of toothache in the previous 4 weeks which resulted in a visit to the dentist, in stopping playing, eating, sleeping, going to school and taking painkillers. RESULTS: Of the 664 sample of children in the participating schools, 589 were interviewed (88.7%). The frequency of previous toothache was 47.5% (95% CI, 44-52) and dental pain caused crying in 17.7% (95% CI, 15-21) of children. 7.6% (95% CI, 5-11) of children had pain in the previous 4 weeks (45 children). Among these 45 children, this recent pain resulted in a visit to the dentist in 41.9% (19 children, i.e. 3.2% of all children), in stopping playing in 26.7% (12 children, i.e. 2.0% of all children), eating in 73.3% (33 children, i.e. 5.6% of all children), sleeping in 31.1% (14 children, i.e. 2.4% of all children) and in going to school in 11.1% (5 children, i.e. 0.8% of all children). CONCLUSION: Toothache in children is a sizeable problem in Harrow and had substantial consequences for children and their guardians. Freedom from disabling dental pain/discomfort is an outcome indicator of oral health and could be used as an explicit goal by dental systems. It is important to note however, that the present study did not assess the extent to which the dental pain was associated with avoidable dental problems as opposed to normal physiological processes. It is important that future work try and separate the prevalence of dental pain caused by physiological from avoidable pathological factors. In addition, future work is needed to assess how effectively and efficiently dental services are responding to people suffering with dental pain.

Family, culture, and health practices among migrant farmworkers.

Migrant farmworkers and their families have restricted access to health and human services because of their frequent relocation between states, language and cultural barriers, and limited economic and political resources. Living and working in substandard environments, these families are at greater risk for developing chronic and communicable disease. In an assessment of health patterns among 225 migrant workers and their families, using personal observations, unstructured interviews, and individual and state health records, children's immunizations were found to be current, but dental caries and head lice were epidemic. Among adults, almost one third tested positive for tuberculosis exposure. Urinary tract infections were the most common health problem among women. Primary and secondary prevention were almost nonexistent because funds for these services were not readily available. The patriarchal system contributes to these problems by limiting access to family-health and social service needs. Although providing comprehensive health care to migrant communities presents unique challenges, nurses can demonstrate their effectiveness in reducing morbidity through strategic interventions and alternative uses of health delivery systems.

The impact of disaster support work.

Limited available evidence suggests that disaster support work may have negative effects. This study attempts to examine the impact of disaster-related stress on helpers offering psychological support to victims of two major disasters, and to identify potential moderating factors. Sixty-seven social workers were surveyed, measures being taken of psychological symptomatology and wellbeing, personality variables, social support, life events, and various aspects of disaster support work. Comparison with normative data suggested that subjects were experiencing significant levels of stress. Two major sources of disaster-related stress were identified: role-related difficulties and contact with clients' distress. Approximately one third of the variance in helper response could be explained by variables reflecting coping style, prior life events and the aforementioned aspects of disaster support work. Follow-up data at 12 months demonstrated persisting high levels of stress.

Clinical pathology of Australian bluetongue virus serotype 16 infection in merino sheep.

Viraemic blood from an ox naturally infected with Australian bluetongue (BLU) virus serotype 16 was passaged twice in sheep. Twelve 2- to 4-years-old Merino ewes, negative in a bluetongue agar gel immunodiffusion test, were inoculated with viraemic blood from the second sheep passage. They were examined for 18 days and compared with a control group. Significant changes in haematological measurements, namely packed cell volume, total white cell count and lymphocyte count, and in plasma enzyme concentrations, namely aspartate transaminase and creatine kinase, occurred in the infected sheep. All infected sheep became sick. The antibody response, and clinical and necropsy findings were consistent with other reports of mild to moderate disease with Australian BLU serotypes.

The Zooxanthellal Tubular System in the Giant Clam.

Giant clams (family Tridacnidae) are special in that they contain large numbers of symbiotic dinoflagellates, Symbiodinium sp., commonly called zooxanthellae which live in the clam's siphonal mantle (hypertrophied siphonal tissues) (1) and are important in its nutrition (2, 3). In 1946, Mansour (4) partially described a tubular system arising from the clam stomach, extending into the mantle and containing zooxanthellae. However, the eminent scientist Sir Maurice Yonge (5, 6) disputed its existence. Subsequently, Yonge's views appear to have suppressed further investigations of Mansour's observations. The zooxanthellae have been universally regarded as living in the hemal spaces of the mantle (2, 5, 7, 8, 9). This study, however, has conhrmed the presence of the tubular system indicated by Mansour and has shown that the zooxanthellae live within a branched, tubular structure that has no direct connection with the hemolymph. The existence of this tubular system has important implications for our understanding of the symbiosis between tridacnids and their symbiotic algae.

Bluetongue virus serotype 20 infection in pregnant Merino sheep.

Eleven maiden Merino ewes, free of antibody to bluetongue virus serotype 20 (BTV-20) in agar gel immunodiffusion and serum neutralisation tests, were mated once with a ram. Ten ewes were inoculated with BTV-20 35 to 42 days after service, and one ewe was left as an uninoculated control. One of the inoculated ewes and the control ewe remained uninfected throughout the experiment. Eight of the remaining 9 ewes showed clinical signs ranging from mild to moderate, and the other showed no clinical signs of infection. BTV-20 viraemia was detected in ewes between days 3 and 11 post inoculation, and the serum antibody response was followed. The control ewe and 5 of the 9 infected ewes were pregnant when examined 90 to 97 days after service. Each of these animals produced a normal lamb. There was no evidence of abortion in the remaining 5 ewes, and no transplacental transfer of virus was detected in the lambs of the 5 infected ewes. At necropsy, 46 days after the birth of the last lamb, no gross or microscopic lesions were observed in either the ewes or lambs.