Herbicide leaching as affected by macropore flow and within-storm rainfall intensity variation: a RZWQM simulation

Within-event variability in rainfall intensity may affect pesticide leaching rates in soil, but most laboratory studies of pesticide leaching use a rainfall simulator operating at constant rainfall intensity, or cover the soil with ponded water. This is especially true in experiments where macropores are present--macroporous soils present experimental complexities enough without the added complexity of variable rainfall intensity. One way to get around this difficulty is to use a suitable pesticide transport model, calibrate it to describe accurately a fixed-intensity experiment, and then explore the affects of within-event rainfall intensity variation on pesticide leaching through macropores. We used the Root Zone Water Quality Model (RZWQM) to investigate the effect of variable rainfall intensity on alachlor and atrazine transport through macropores. Data were used from an experiment in which atrazine and alachlor were surface-applied to 30 x 30 x 30 cm undisturbed blocks of two macroporous silt loam soils from glacial till regions. One hour later the blocks were subjected to 30-mm simulated rain with constant intensity for 0.5 h. Percolate was collected and analyzed from 64 square cells at the base of the blocks. RZWQM was calibrated to describe accurately the atrazine and alachlor leaching data, and then a median Mid-west variable-intensity storm, in which the initial intensity was high, was simulated. The variable-intensity storm more than quadrupled alachlor losses and almost doubled atrazine losses in one soil over the constant-intensity storm of the same total depth. Also rainfall intensity may affect percolate-producing macroporosity and consequently pesticide transport through macropores. For example, under variable rainfall intensity RZWQM predicted the alachlor concentration to be 2.7 microg ml(-1) with an effective macroporosity of 2.2 E(-4) cm(3) cm(-3) and 1.4 microg ml(-1) with an effective macroporosity of 4.6 E(-4) cm(3) cm(-3). Percolate-producing macroporosity and herbicide leaching under different rainfall intensity patterns, however, are not well understood. Clearly, further investigation of rainfall intensity variation on pesticide leaching through macropores is needed.     

Bladder outlet obstruction in a 6-month-old alpaca secondary to pelvic displacement of the urinary bladder

A 6-month-old female alpaca was presented for stranguria. Based on the history, physical examination findings, and radiographic studies, the alpaca was diagnosed with bladder outlet obstruction, secondary to pelvic displacement of the bladder, a condition previously unreported in camelids. Cystopexy was performed and the alpaca recovered unremarkably.     

Test of the Root Zone Water Quality Model (RZWQM) for predicting runoff of atrazine, alachlor and fenamiphos species from conventional-tillage corn mesoplots

The Root Zone Water Quality Model (RZWQM) is a comprehensive, integrated physical, biological and chemical process model that simulates plant growth and movement of water, nutrients and pesticides in a representative area of an agricultural system. We tested the ability of RZWQM to predict surface runoff losses of atrazine, alachlor, fenamiphos and two fenamiphos oxidative degradates against results from a 2-year mesoplot rainfall simulation experiment. Model inputs included site-specific soil properties and weather, but default values were used for most other parameters, including pesticide properties. No attempts were made to calibrate the model except for soil crust/seal hydraulic conductivity and an adjustment of pesticide persistence in near-surface soil. Approximately 2.5 (+/- 0.9), 3.0 (+/- 0.8) and 0.3 (+/- 0.2)% of the applied alachlor, atrazine and fenamiphos were lost in surface water runoff, respectively. Runoff losses in the 'critical' events--those occurring 24 h after pesticide application--were respectively 91 (+/- 5), 86 (+/- 6) and 96 (+/- 3)% of total runoff losses for these pesticides. RZWQM adequately predicted runoff water volumes, giving a predicted/observed ratio of 1.2 (+/- 0.5) for all events. Predicted pesticide concentrations and loads from the 'critical' events were generally within a factor of 2, but atrazine losses from these events were underestimated, which was probably a formulation effect, and fenamiphos losses were overestimated due to rapid oxidation. The ratios of predicted to measured pesticide concentrations in all runoff events varied between 0.2 and 147, with an average of 7. Large over-predictions of pesticide runoff occurred in runoff events later in the season when both loads and concentrations were small. The normalized root mean square error for pesticide runoff concentration predictions varied between 42 and 122%, with an average of 84%. Pesticide runoff loads were predicted with a similar accuracy. These results indicate that the soil-water mixing model used in RZWQM is a robust predictor of pesticide entrainment and runoff.     

Control of introduced mammalian predators improves kaka Nestor meridionalis breeding success: reversing the decline of a threatened New Zealand parrot

The kaka (Nestor meridionalis) is a threatened, endemic New Zealand parrot that is declining primarily because of predation by introduced mammals. Numbers of female kaka surviving to sexual maturity more than compensated for adult female mortality at three sites with predator control but not at three unmanaged sites. Nesting success at the sites with predator control was significantly greater (?80%) than at unmanaged sites (?38%) while predation on adult females was significantly less (5% c.f. 65%). Predation was the most common cause of nesting failure at all sites. Stoats (Mustela erminea) appeared to be the main predator, although evidence of possum (Trichosurus vulpecula) predation on eggs, nestlings and nesting females was also found. These results suggest that control of stoats and possums can potentially reverse the decline of the kaka on the main islands of New Zealand.     

The role of essential trace elements in embryonic and fetal development in livestock

This review addresses the concept that essential trace minerals play a vital role in many enzymatic and metabolic pathways that are critical for conceptus development during pregnancy in livestock species. The conceptus relies entirely on the maternal system for a sufficient supply of trace minerals and other nutrients needed for normal development. If this supply is inadequate, growth and/or health of the conceptus can be affected adversely, and many of these effects carry over into the neonatal period. Information, accumulated in our laboratory and presented herein, indicates that zinc, copper and manganese are among the trace minerals that have the greatest impact on reproduction. For example, levels of zinc, copper and manganese were several fold greater in the conceptus than in other reproductive tissues, indicating that the conceptus preferentially accumulates these minerals, an action that may be important for conceptus development, growth and survival. Moreover, some recent results indicate that increasing the biological availability of zinc, copper and manganese, by attachment to short peptide chains (i.e., proteinated trace minerals) can enhance reproductive performance of swine. Mineral concentrations in conceptuses from female pigs consuming proteinated trace minerals were greater than those from females that consumed only inorganic mineral salts. Elucidating the mechanisms whereby conceptus development and survival are enhanced by essential trace minerals may lead to development of specific feeding programs to increase the number and health of offspring at parturition, thereby allowing for further improvements in production efficiency in animal agriculture.     

Software for pest-management science: computer models and databases from the United States Department of Agriculture-Agricultural Research Service

We present an overview of USDA Agricultural Research Service (ARS) computer models and databases related to pest-management science, emphasizing current developments in environmental risk assessment and management simulation models. The ARS has a unique national interdisciplinary team of researchers in surface and sub-surface hydrology, soil and plant science, systems analysis and pesticide science, who have networked to develop empirical and mechanistic computer models describing the behavior of pests, pest responses to controls and the environmental impact of pest-control methods. Historically, much of this work has been in support of production agriculture and in support of the conservation programs of our 'action agency' sister, the Natural Resources Conservation Service (formerly the Soil Conservation Service). Because we are a public agency, our software/database products are generally offered without cost, unless they are developed in cooperation with a private-sector cooperator. Because ARS is a basic and applied research organization, with development of new science as our highest priority, these products tend to be offered on an 'as-is' basis with limited user support except for cooperating R&D relationship with other scientists. However, rapid changes in the technology for information analysis and communication continually challenge our way of doing business.     

Habitat functional response mitigates reduced foraging opportunity: implications for animal fitness and space use

Context

Animals selectively use landscapes to meet their energetic needs, and trade-offs in habitat use may depend on availability and environmental conditions. For example, habitat selection at high temperatures may favor thermal cover at the cost of reduced foraging efficiency under consistently warm conditions.

Objective

Our objective was to examine habitat selection and space use in distinct populations of moose (Alces alces). Hypothesizing that endotherm fitness is constrained by heat dissipation efficiency, we predicted that southerly populations would exhibit greater selection for thermal cover and reduced selection for foraging habitat.

Methods

We estimated individual step selection functions with shrinkage for 134 adult female moose in Minnesota, USA, and 64 in Ontario, Canada, to assess habitat selection with variation in temperature, time of day, and habitat availability. We averaged model coefficients within each site to quantify selection strength for habitats differing in forage availability and thermal cover.

Results

Moose in Ontario favored deciduous and mixedwood forest, indicating selection for foraging habitat across both diel and temperature. Habitat selection patterns of moose in Minnesota were more dynamic and indicated time- and temperature-dependent trade-offs between use of foraging habitat and thermal cover.

Conclusions

We detected a scale-dependent functional response in habitat selection driven by the trade-off between selection for foraging habitat and thermal cover. Landscape composition and internal state interact to produce complex patterns of space use, and animals exposed to increasingly high temperatures may mitigate fitness losses from reduced foraging efficiency by increasing selection for foraging habitat in sub-prime foraging landscapes.

     

Effects of intestinal ischemia on in vitro activity of adjacent jejunum in samples obtained from ponies.

OBJECTIVE: To determine whether intestinal ischemia would alter activity of the jejunum in vitro or alter staining characteristics for certain types of enteric neurotransmitters. SAMPLE POPULATION: Jejunal samples obtained from 10 ponies. PROCEDURE: Jejunal samples were obtained from locations proximal and distal to an area of small intestine made ischemic for 60 minutes. A portion of each sample was stained to detect substance P-like immunoreactivity, cholinergic and adrenergic neurons, and nitric oxide synthase. Portions of the remaining samples were suspended in muscle baths. General activity patterns (frequency and amplitude of contraction), responses to neuronal depolarization induced by electrical field stimulation (EFS), and responses to 1 microM norepinephrine (NE) were compared with responses of a normal section of small intestine obtained prior to ischemic insult. RESULTS: Staining patterns were not altered. Proximal and distal sections had evidence of decreased contractility, compared with the normal section. Contraction frequency also was decreased, and distal sections had lower contraction frequency than proximal sections. Relaxation responses were decreased in distal sections. Responses to NE differed significantly for distal and proximal sections, compared with normal sections. CONCLUSIONS AND CLINICAL RELEVANCE: Short-term ischemia can significantly affect adjacent bowel. Contractile and relaxation responses are impaired. Discrepancies in intestinal motility patterns and alterations in response to NE for sections proximal and distal to ischemic intestine could lead to clinical ileus or slowed transit of ingesta.     

Altered homeostasis of extracellular matrix proteins in joints of standardbred trotters during a long-term training programme

This study evaluates how strenuous training, age and lameness influence the release of cartilage oligomeric matrix protein (sf-COMP), aggrecan and collagen type II into synovial fluid in 28 (19.5-40 months) Standardbred trotters (STB), during a long-term training programme (24 months). All the horses were trained by the same trainer and were healthy on entering the training programme. Synovial fluid (sf) from the left middle carpal joint in each subject was sampled every third month. Enzyme-linked immunosorbent assay was used to determine the concentrations of sf-COMP, sf-aggrecan and sf-collagen type II. Concentration of sf-COMP decreased with increasing age and total days of training. The concentration of sf-COMP was found similarly related to both age and total days of training, so they could not be differentiated. It was also shown that the concentration of collagen type II degradation products increased with total days of training. The study shows that extensive and long-term training programme induces metabolic changes in articular cartilage exemplified by reduced release and synthesis of COMP. This is most likely due to strenuous training leading to inappropriate load on the articular cartilage.