Browsing Rangeland Ecology & Management / Journal of Range Management by Authors
A method for estimating cattle fecal loading on rangeland watershedsTate, K. W.; Atwill, E. R.; McDougald, N. K.; George, M. R.; Witt, D. (Society for Range Management, 2000-09-01)Water quality contamination by pathogens and nutrients from cattle fecal deposits is a concern on rangeland watersheds. The temporal and spatial deposition of fecal material relative to storm events and water-bodies determines much of the risk a grazing scheme presents to water quality. The objective of this study was to develop and evaluate a comparative technique to estimate cattle fecal loading across a watershed through time. Once the method was developed, dry and wet season trials were conducted on a 138 ha experimental rangeland watershed at the San Joaquin Experimental Range in 1996-97. Fifty-four permanent 40 m2 belt transects were established across the watershed. Observers ocularly assigned a rank of 1 (smallest diameter) to 5 (largest diameter) to each fecal deposit within a transect. A regression relationship was developed to predict fecal deposit dry weight by rank. Load per transect was calculated as the total weight of all fecal deposits in a transect. All fecal deposits in transects were collected and actual fecal load determined. The comparative yield methodology was successfully adapted to estimate rangeland fecal loading. Regression relationships predicting fecal deposit dry weight by ranks were highly significant for all observers (p < 0.001). The R2 values ranged from 0.97 to 0.99 in the dry season and 0.89 to 0.94 in the wet season. There was no significant difference between the weighted fecal load estimate and the estimates of observers using the comparative method (P < 0.05). This method provides a rapid, simple method for estimating spatial and temporal livestock fecal loading on rangeland watersheds.
Cryptosporidium parvum transport from cattle fecal deposits on California rangelandsTate, K. W.; Atwill, E. R.; George, M. R.; McDougald, N. K.; Larsen, R. E. (Society for Range Management, 2000-05-01)Cryptosporidium parvumis 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. parvumin 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 foroocyst concentration following each of 4 storm events. Oocysts were transported during each storm. Slope was a significant factor 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, becoming available for transport to water-bodies. Future studies need to examine surface and subsurface transport of oocysts on rangeland hillslopes for distances greater than 1 m.
Spatial and temporal patterns of cattle feces deposition on rangelandTate, K. W.; Atwill, E. R.; McDougald, N. K.; George, M. R. (Society for Range Management, 2003-09-01)The objective of this study was to identify and model environmental and management factors associated with cattle feces deposition patterns across annual rangeland watersheds in the Sierra Nevada foothills. Daily cattle fecal load accumulation rates were calculated from seasonal fecal loads measured biannually on 40 m2 permanent transects distributed across a 150.5 ha pasture in Madera County, Calif. during the 4 year period from 1995 through 1998. Associations between daily fecal load per season, livestock management, and environmental factors measured for each transect were determined using a linear mixed effects model. Cattle feces distribution patterns were significantly associated with location of livestock attractants, slope percentage, slope aspect, hydrologic position, and season. Transects located in livestock concentration areas experienced a significantly higher daily fecal load compared to transects outside of these concentration areas (P < 0.001). Percent slope was negatively associated with daily fecal load, but this association had a significant interaction with slope aspect (P = 0.02). Daily fecal load was significantly lower during the wet season compared to the dry season (P = 0.002). Daily fecal loading rates across hydrologic positions were dependent upon season. Our results illustrate the opportunities to reduce the risk of water quality contamination by strategic placement of cattle attractants, and provide a means to predict cattle feces deposition based upon inherent watershed characteristics and management factors.