Cattle Temporal and Spatial Distribution in Midwestern Pastures Using Global Positioning (Three-year Progress Report)

Previous research has shown that grazing cattle tend to congregate in streamside zones of pastures to obtain water and shade for thermoregulation. However, problems associated with thermoregulation may be increased because of the presence of endophyte-infected tall fescue in pastures. Defining relationships between cattle distribution, such pasture characteristics as size, shape, shade distribution, botanical composition, and climatic factors related to heat stress, will provide the basis for the development and implementation of management practices that minimize nonpoint source pollution possibly associated with grazing cattle

Cattle Temporal & Spatial Distribution in Midwestern Pastures Using Global Positioning (A Three-Year Progress Report)

Eight pastures on five southern Iowa cow-calf farms were used to evaluate the effects of pasture characteristics and microclimatic conditions on cattle grazing cool-season grass pastures with streams and/or ponds. Pastures ranged from 19 to 309 acres and contained varying proportions of cool-season grasses, legumes, sedge, broadleaf weeds, brush, and bare ground. The percentages of pasture area that were shaded ranged from 19 to 73%. Cows were Angus and Angus-Cross on seven of the pastures, and Mexican Corriente on the remaining pasture. In spring, summer, and fall of 2007, 2008, and 2009, 2 to 3 cows per pasture were fitted with Global Positioning System (GPS) collars to record position at 10 minute intervals for periods of 5 to 14 days. Ambient temperature, black globe temperature, dew point, relative humidity, and wind speed and direction were collected with HOBO data loggers at ten minute intervals over the 2007, 2008, and 2009 grazing seasons on each farm. Streams, ponds, and fence lines were referenced on a geospatial map and used to establish zones in the pastures. Designated zones were: in the stream or pond, within 100 feet, or greater than 100 ft (uplands) from the stream or pond (water source). One hundred thirty-nine data sets were obtained throughout the three-year project. Mean proportions of observations when cattle were in the water source differed (P\u3c0.0001) between farms, but not between seasons (P=0.5824). Mean proportions of time cattle spent within 100, or greater 100 ft of the water source differed (P\u3c0.0001) among farms. The proportion of time cattle were within the streamside zone (defined as being in the water source or within 100 feet of the water source) increased with increasing ambient temperature, increasing the proportion of streamside zone within a pasture, increasing the proportion of total pasture shade within the streamside zone, and decreasing pasture size. Therefore, implementation of grazing management practices for the protection of pasture streams are more likely to be effective on small and/or narrow pastures in which cattle have less opportunity to locate in upland locations

Impact of Grazing Management on Cattle Distribution and Physical Characteristics of the Riparian Zones of Pastures

Grazing management practices that allow cattle to congregate near pasture streams may result in the loss of vegetative cover and accumulation of manure near pasture streams. These conditions may cause loading of the streams with sediment, phosphorus, and pathogens carried in surface runoff. The loss of vegetation and increased compaction associated with concentrated cattle traffic may promote stream bank erosion causing further impairment of stream water quality. The objectives of the current study were 1) to evaluate cattle distribution patterns, in relation to a pasture stream/pond and 2)to evaluate the effects of stocking rate and the botanical composition of the pastures’ riparian zone on the forage sward height and the proportions of bare and manure-covered ground along the banks of pasture streams

Grazing Management of Beef Cows to Limit Non-point Source Pollution of Streams in Midwestern Pastures

In 2006, the Iowa DNR identified 336 impaired water bodies in Iowa. The majority of these impairments are associated with elevated nutrient, sediment, or bacterial loads in streams and lakes. Poorly managed grazing of beef cattle in riparian areas may contribute to a reduction in quality of Midwest surface waters. However, research has shown that management practices that alter the timing, frequency, duration, and timing of grazing can reduce the impact of cattle on water sources

The WASp-like protein Scar regulates macropinocytosis, phagocytosis and endosomal membrane flow in Dictyostelium

Scar, a member of the WASp protein family, was discovered in Dictyostelium discoideum during a genetic screen for second-site mutations that suppressed a developmental defect. Disruption of the scar gene reduced the levels of cellular F-actin by 50%. To investigate the role of Scar in endocytosis, phagocytosis and endocytic membrane trafficking, processes that depend on actin polymerization, we have analyzed a Dictyostelium cell line that is genetically null for Scar. Rates of fluid phase macropinocytosis and phagocytosis are significantly reduced in the scar- cell-line. In addition, exocytosis of fluid phase is delayed in these cells and movement of fluid phase from lysosomes to post-lysosomes is also delayed. Inhibition of actin polymerization with cytochalasin A resulted in similar phenotypes, suggesting that Scar-mediated polymerization of the actin cytoskeleton was important in the regulation of these processes. Supporting this conclusion, fluorescence microscopy revealed that some endo-lysosomes were ringed with F-actin in control cells but no F-actin was detected associated with endo-lysosomes in Scar null cells. Disruption of the two genes encoding the actin monomer sequestering protein profilin in wild-type cells causes defects in the rate of pinocytosis and fluid phase efflux. Consistent with a predicted physical interaction between Scar and profilin, disrupting the scar gene in the profilin null background results in greater decreases in the rate of fluid phase internalization and fluid phase release compared to either mutant alone. Taken together, these data support a model in which Scar and profilin functionally interact to regulate internalization of fluid and particles and later steps in the endosomal pathway, probably through regulation of actin cytoskeleton polymerization

Incidence of Bovine Enterovirus, Coronavirus, and Group A Rotavirus, and Concentration of Fecal Coliforms in Midwestern Pasture Streams

The occurrence of bovine enteric pathogens and fecal coliform contamination in streams of 13 Midwestern cow/calf pastures was studied during the 2007-2008 grazing seasons. Water samples (n=812) were collected biweekly at up- and downstream locations on each stream. Incidence of Bovine Enterovirus (BEV), Coronavirus (BCV), and group A Rotavirus (BRV), and concentration of fecal coliforms (FC) were evaluated. The mean incidence of BEV, BCV, and BRV in all samples were 5.42, 1.60, and 0.25%, respectively, over the two grazing seasons. There were farm differences for BEV (P=0.02) and BCV (P=0.01) incidences, but there were no differences (P\u3e0.05) for the incidences of the viruses between samples collected from up- or downstream locations. Cattle presence in the pasture on the day and three days prior to sampling were related (P=0.02, P=0.04), respectively, to BEV, but were not related (P\u3e0.05) to BCV or BRV. However, incidences of BEV, BCV or BRV were not related (P\u3e0.05) to cattle presence seven days prior to sampling. Mean FC were 930 and 938 colony-forming units (CFU)/100ml, respectively, for up- and downstream samples. Differences (P=0.01) were observed between farms for concentration of FC. Preliminary results indicate that the timing and management of grazing may be beneficial in decreasing the incidence of enteric viral pathogens and concentrations of FC in Midwestern pasture streams

Coronin 1B Antagonizes Cortactin and Remodels Arp2/3-Containing Actin Branches in Lamellipodia

The dendritic actin network generated by Arp2/3 complex in lamellipodia underlies formation of protrusions, directional sensing and migration. While the generation of this network is well studied, the mechanisms regulating network disassembly are poorly understood. We report that Coronin 1B disassembles Arp2/3-containing actin filament branches by inducing Arp2/3 dissociation. This activity is antagonized by Cortactin, a filament branch stabilizer. Consistent with this biochemical competition, depletion of both proteins partially rescues defects in lamellipodial dynamics observed upon depletion of either protein alone. Coronin 1B targets actin branches in a manner that is mutually exclusive with Arp2/3 complex and alters the branch angle. We conclude that Coronin 1B replaces Arp2/3 complex at actin filament branches as the dendritic network matures and drives the turnover of branched actin networks