EFFECT OF RANGELAND FIRE ON HEAVY METAL CONCENTRATIONS IN EDIBLE TISSUE OF GRAZING LAMB

Fire is becoming an increasing threat to human and livestock health, particularly in California. Over time, vegetation sequesters heavy metals from pollution and environmental stores; when that vegetation burns, accumulated metals are released into the ash. Mercury is of primary concern due to its known accumulation in plant biomass, as well as muscle tissue of contaminated animals. The risk of heavy metal accumulation in grazing animals exposed to these burned lands is currently unknown. On July 27, 2018, the River Fire burned approximately 2/3 of the lands at the Hopland Research and Extension Center, including multiple pastures used for grazing ewes and their lambs. This study will take advantage of this natural exposure by sampling muscle tissue from lambs that graze on fire re-growth pastures and are slaughtered in 2019. The heavy metal concentrations in these samples will be compared to that of tissue from last year's lamb crop, grazed on the same property prior to the fire, whose meat is currently in freezer storage. We hypothesize that lambs grazed on plots of land burned in the recent wildfire will have higher concentrations of heavy metals in their muscle tissue, particularly mercury, than lambs grazed on these plots the previous year. We plan to use the findings from this study to inform post fire grazing recommendations. Additionally, we intend to apply for further funding to extend investigations into the tissue distribution of contamination and the effect of heavy metal contamination on animal production traits, such as reproduction, in livestock following exposure to recently burned grazing lands.Hypotheses:1) The meat of lambs grazed on plots of land burned in the recent wildfire will contain higher concentrations of heavy metals, particularly mercury, than the meat of lambs grazed on the same facility 1 year prior to the fire.2) Heavy metal concentrations in wool from animals grazed on burned lands will correlate highly with those in meat.Objectives:1) Determine if there is a difference between heavy metal concentrations in meat from lambs grazed at the HREC sheep research station prior to the 2018 River Fire compared to the meat of lambs grazed at the same facility on fresh burn regrowth after the fire.2) Assess the utility of wool sampling as a tool for predicting food safety prior to animals entering slaughter by evaluation the correlation between meat and wool samples from sheep grazed on burned pastures.