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United States Department of Agriculture

Agricultural Research Service

Research Project: Developing An Understanding of Soil and Forage Selenium Concentrations and the Effect of Selenium Concentration on Feed Preference by Elk

Location: Poisonous Plant Research

Project Number: 2080-32630-012-04
Project Type: Trust

Start Date: Dec 01, 2013
End Date: Nov 30, 2015

Objective:
The objectives of these selenium studies are to: 1) develop a model that establishes the correlation between Se concentrations and forms in the soil and expected Se concentrations in the different plant species or groups (grasses, legumes, and forbs) as a base line, 2) determine if elk will discriminate between forages and feeds with different concentrations of Se, and the potential effects on feed intake.

Approach:
Experimental Design for Tansect Study: Transect Sites: Five historic mine sites to be identified in collaboration with members of the SIPMA Transect Methodology: Y-transects centered on seleniforous overburden sites, will be established on each site. Each transect arm will be 100 feet in length and offset by 120 degrees with each adjacent arm. Five soil samples will be collected at equal distances along each transect line. Furthermore, at each sample site along the transect, the following data will be collected: • Soil samples will be taken down to a depth of 12” and analyzed for total Se, bioavailable Se, pH, and salinity (16 soil samples per Y-transect). • Vegetation will be collected from a ½ by ½ meter on either side of the transect point and separated by species and identified by botanists. If biomass production is high enough for each species they will be analyzed separately for total Se and some samples will be selected for selenium speciation analysis by HPLC-ICP-MS. If there is not enough biomass at the transect point the forages will be grouped as grasses, legumes, and forbs for analysis. • Plant samples will be dried, ground and total Se concentration determined by ICP-MS as previously described. Selenium species in the plants will be determined by HPLC-ICP-MS, using protocols that are being developed. Statistical analysis will include least squares regression analysis and stepwise regression to correlate soil Se concentrations to plant species Se concentrations. Possible covariates to include soil pH, salinity, and annual precipitation may be used to eliminate variation due to uncontrolled environmental factors. Experimental Design for Elk Study: Ten elk will be housed individually in pens with free access to non Se-containing salt block and water. They will be adapted for 21 days to the pens and fed only control pellets (containing < 0.3 ppm Se) at a total of 3% of their body weight divided evenly in 5 different feed pans during the adaptation period. The pellets will be offered in 3 trials (15, 12, and 9 day trials with 5, 4, and 3 choices of pellets with different Se concentrations ranging from 1 to 150 ppm Se). At the beginning and end of each trial the elk will be bled using jugular venipuncture to collect serum and whole blood samples. Hair samples will also be collected at the same time. The samples will be analyzed for Se content by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The pellet trials will be designed as a Latin Square with positions, days, and pellets of various Se concentrations as factors, with each animal comprising its own square. Each pellet will be rotated to a new position within each pen each day of the trial. Each type of pellet will be offered in each feed box at 1.5% of the animal’s body weight for 8 hours each day. The intent is that the animals cannot reach satiety from eating just one choice. Refusals will be weighed at the end of the feeding period. The first pellet trial will use 5 pellets of varying Se concentrations, during subsequent trials, the pellet with the lowest Se concentration will be rmoved and the trials will re-run with 4 and 3 pellet choices, respectively.

Last Modified: 10/31/2014
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