Royce E. Larsen

Water-quality benefits of having cattle manure deposited away from streams

Abstract A series of runoff and infiltration studies with bovine feces placed 0.0, 0.61, 1.37, or 2.13 m from a collection point were used to assess effectiveness of vegetative filter strips. Effectiveness was evaluated on the ability of the separation distance to reduce the number of fecal coliform (FC) bacteria being transported from the manure to the edge of the plots. Bacterial transport was evaluated under conditions of variable distance, soil permeability, and rainfall intensity. The FC bacteria yields were 40–115 million at the edge of the manure pile. This is only 17% of the FC in the manure. FC concentrations and yields were further reduced as the separation increased. The analysis of data did not indicate significant differences of bacteria transport in relation to rainfall intensities of 5 cm/h versus 10 cm/h at the 0.61, 1.37, or 2.13 m distances.

Cryptosporidium parvum transport from cattle fecal deposits on California rangelands.

Cryptosporidium parvum is a fecal borne protozoan parasite that can be carried by and cause gastrointestinal illness in humans, cattle, and wildlife. The illness, cryptosporidiosis, can be fatal to persons with compromised immune systems. At question is the potential for C. parvum in cattle fecal deposits on rangeland watersheds to contaminate surface water. First, C. parvum oocysts must be released from fecal deposits during rainfall, becoming available for transport. In 1996, we examined the transport of C. parvum oocysts in overland flow from fecal deposits under natural rainfall and rangeland conditions at the San Joaquin Experimental Range in Madera County, Calif. Our null hypothesis was that C. parvum oocysts are not released from fecal pats and transported 1 m downslope as overland flow with rainfall. Paired plots were located on 10, 20, and 30% slope sites. Each plot was loaded with four, 200 g fecal pats dosed with 10 5 oocysts g -1 . Pats were placed 1.0 m above the base of each plot. Composite runoff samples from each plot were analyzed for oocyst concentration following each of 4 storm events. Oocysts were transported during each storm. Slope was a significant fac tor in oocyst transport, with oocyst transport increasing with slope. Although not significant, there was an apparent flushing effect of oocysts across storms, with the majority transported in the first 2 storms. A pilot rainfall simulation experiment also revealed a flushing phenomenon from pats during individual rainfall events. C. parvum oocysts in fecal pats on rangeland can be transported from fecal deposits during rainfall events, becom ing available for transport to water-bodies. Future studies need to examine surface and subsurface transport of oocysts on range land hillslopes for distances greater than 1 m.

Viewpoint: livestock influences on riparian zones and fish habitat: literature classification.

A key was used to classify articles about livestock influences on riparian zones and fish habitat into 3 classes: papers that contained original data, those that were commentary, and reports about methodology such as classification systems, policies, and monitoring criteria. Four hundred and twenty-eight of the total articles were directly related to grazing impacts on riparian zones and fish habitat. Only 89 of these grazing impact articles were classified as experimental, where treatments were replicated and results were statistically valid. This analysis revealed several limitations of riparian grazing studies that included: (1) inadequate description of grazing management practices or treatments, (2) weak study designs, and (3) lack of pre-treatment data. More long-term, replicated treatment studies are needed in the future.

Cryptosporidium rubeyi n. sp. (Apicomplexa: Cryptosporidiidae) in multiple Spermophilus ground squirrel species

Previously we reported the unique Cryptosporidium sp. “c” genotype (e.g., Sbey03c, Sbey05c, Sbld05c, Sltl05c) from three species of Spermophilus ground squirrel (Spermophilus beecheyi, Spermophilus beldingi, Spermophilus lateralis) located throughout California, USA. This follow-up work characterizes the morphology and animal infectivity of this novel genotype as the final step in proposing it as a new species of Cryptosporidium. Analysis of sequences of 18S rRNA, actin, and HSP70 genes of additional Cryptosporidium isolates from recently sampled California ground squirrels (S. beecheyi) confirms the presence of the unique Sbey-c genotype in S. beecheyi. Phylogenetic and BLAST analysis indicates that the c-genotype in Spermophilus ground squirrels is distinct from Cryptosporidium species/genotypes from other host species currently available in GenBank. We propose to name this c-genotype found in Spermophilus ground squirrels as Cryptosporidium rubeyi n. sp. The mean size of C. rubeyi n. sp. oocysts is 4.67 (4.4–5.0) μm × 4.34 (4.0–5.0) μm, with a length/width index of 1.08 (n = 220). Oocysts of C. rubeyi n. sp. are not infectious to neonatal BALB/c mice and Holstein calves. GenBank accession numbers for C. rubeyi n. sp. are DQ295012, AY462233, and KM010224 for the 18S rRNA gene, KM010227 for the actin gene, and KM010229 for the HSP70 gene.

Effectiveness of nutrient supplement placement for changing beef cow distribution

Assessments of conservation effects are being conducted to determine the effectiveness of agricultural conservation practices. The practice of nutrient supplement placement to improve livestock distribution has not been designated a “best management practice” by the USDA Natural Resources Conservation Service (NRCS). Three studies in California visually and statistically document the effectiveness of nutrient supplement placement for changing livestock distribution. The initial study conducted in the Sierra Nevada foothills demonstrated that use of riparian patches could be reduced with strategic placement of dehydrated molasses supplement. A study on an adjacent ranch found that during the dry season, supplement placement effectively redistributed livestock by attracting them into a zone that extended out to about 600 m (1,980 ft) from the supplement. In a study on a coastal ranch in San Luis Obispo County, nutrient supplements were used to attract cows into an ungrazed forest adjacent to grazed grassland. The results of the studies reported here support the effectiveness of supplement placement for changing livestock distribution. Integration of supplement placement practices into best management practices and into NRCSs prescribed grazing standard is supported by this research.

Determining Drought on California’s Mediterranean-Type Rangelands, he Noninsured Crop Disaster Assistance Program

Determining Drought on California’s Mediterranean-Type Rangelands, he Noninsured Crop Disaster Assistance Program DOI:10.2458/azu_rangelands_v32i3_george

Coping with Drought on California Rangelands

On the Ground Rangeland livestock producers were among the first agricultural communities affected by Californias multiyear drought. Rancher surveys and in-person interviews have identified key strategies for coping with and adapting to drought. Increasing flexibility, resource valuation, and information sharing are important components of building adaptive capacity. Web-based communication systems have provided new tools for peer-to-peer learning, public education, and extending knowledge to larger audiences. Insights from managers experiences are important for adaptation planning to enhance resilience of rangeland social-ecological systems to climate stresses.

Risk factors for Escherichia coli O157 on beef cattle ranches located near a major produce production region.

Our goal was to identify climate variables and management practices associated with the presence of E. coli O157 in rangeland cow-calf operations located in a major leafy green production region in the California Central Coast. E. coli O157 was present in 2·6% (68/2654) of faecal, 1·5% (3/204) of water and 1·1% (1/93) of sediment samples collected on eight ranches over 2.5 years. Five (62·5%) ranches were positive at least once during the study. The odds of detecting E. coli O157 in faecal samples was higher during periods of higher maximum soil temperature, higher maximum relative humidity, and larger herd sizes, but decreased as wind speed increased. Molecular subtyping of isolates from cattle faeces and streams/sediments suggested minimal movement of strains between ranches. The findings suggest that E. coli O157 prevalence is relatively low on cow-calf ranches in this region, spatially constrained, but may vary by weather conditions and herd size.

Using Phenology to Optimize Timing of Mowing and Grazing Treatments for Medusahead (Taeniatherum caput-medusae)☆

ABSTRACT The invasive annual grass medusahead (Taeniatherum caput-medusae [L.] Nevski) poses a substantial threat to the health and function of rangelands across the western United States. On rangelands containing other desirable annual grasses, selective control of medusahead is difficult as this invasive species has traits similar to those of desired species. One key trait that differs between medusahead and other annual grasses is the rate and timing of phenological development. In this study we define management states for medusahead on the basis of the patterns of variation of forage palatability and susceptibility of seed production to defoliation over phenological stages. We integrate these management states with field observations to model the rates and timing of phenology-based management states to identify when targeted grazing or mowing treatments are most appropriate using Dirichlet regression and multistate modeling. While defoliation at any phenological stage from V3 (boot) to R8 (milk stage) was effective in reducing medusahead seed head production, clipping after anthesis almost eliminated seed production. However, the observed decline in crude protein at this point (11–8%) suggests that the transition from R4 (emergence of awns) to R5 (anthesis) is also the point at which medusahead becomes both unpalatable and not adequately nutritious to livestock. As a consequence there was a window of 10 to 15 days when 90% or more of medusahead reproductive tillers are susceptible to grazing but could also support nutritional needs of cattle and sheep to prevent avoidance in diet selection. In contrast, the window of opportunity for mowing, on average, extended for about 35 days. In a given year, the timing in which different medusahead populations entered each phenological stage varied at both the landscape and pasture scale, which creates both challenges and opportunities in using grazing animals and other defoliation mechanisms to control medusahead.

Southern Steelhead, Hard Woody Debris, and Temperature in a California Central Coast Watershed

Abstract We surveyed large wood volumes in relation to the distribution and density of rainbow trout Oncorhynchus mykiss and steelhead (anadromous rainbow trout) in 15 stream reaches in the upper Salinas River watershed, California, which represents the southern end of the species’ range. The main tree species contributing to large wood were hardwoods: coast live oak Quercus agrifolia, California sycamore Platanus racemosa, red willow Salix laevigata, and valley oak Q. lobata. Large wood jams were important in pool formation and typically had red willow as their key pieces. Temperatures were exceptionally warm during the study period. No steelhead were observed at sites where the mean water temperature exceeded 21.5°C or the maximum water temperature exceeded 26°C. The combined importance of high temperatures and large wood on the distribution and abundance of southern steelhead indicates that suitable habitat may be reduced if climate change continues on its present course of warming and the frequency of...