ECOLOGY, TOXICOLOGY, AND MANAGEMENT OF MADAGASCAR FIREWEED (SENECIO MADAGASCARIENSIS POIRET) IN TROPICAL AND SUB-TROPICAL RANGELANDS
Project Number: 5428-32000-015-03
Start Date: Jul 10, 2012
End Date: Aug 31, 2013
The purpose of the studies proposed here are to investigate the impact of fireweed density on forage availability, consumption, and toxicity of fireweed in cattle, and to examine the possible role of CT in binding toxic plant compounds like pyrrolzidine alkaloids (PA). This project will address TSTAR goals 1, 2, 6, and 7. Specifically this project will investigate innovative and proactive management strategies for the control of an invasive weed, fireweed, in range and pasture lands of Hawaii (7). The information from this project will be used to develop decision-support materials for producers (6) that will provide environmentally sound management practices (2) that will enhance the overall productivity and sustainability of the livestock industry in the State. The specific objectives of this project are:
1) Determine the threshold density of fireweed within pastures and concomitant reductions in available forage that result in increased consumption by grazing cattle.
2) Determine the toxicity of fireweed to cattle; investigate the ability of CT to bind PAs in an in vitro system, and further determine the toxic effects of fireweed PAs in cattle with and without the potential ameliorating presence of CT.
3) Develop and disseminate a series of best-management practices for grazing cattle on fireweed infested range and pasture lands that will minimize PA poisoning and effectively control the spread of fireweed.
This research project will be carried out in cooperation with a producer on Maui utilizing small paddocks located in fireweed populations to investigate how plant density and available forage influence consumption rates in cattle. Blood serum levels of specific enzymes indicative of PA activity in the liver will be monitored and correlated to changes in plant density, forage availability, and animal performance to determine factors that affect the fate of PAs in the animal. Toxicology and grazing and in-vitro rumen digestion trials will be used to a) characterize the toxicological response of cattle to PAs in fireweed, and determine potential binding of CT and PAs in vitro; b) determine if the adverse effects of PAs are ameliorated by adding CT to animals’ diets; and c) through an additional grazing trial determine if cattle provided CT supplementation will willingly graze fireweed in a pasture environment. Again blood serum levels of indicator enzymes will be monitored to determine the relative toxicity level experienced by grazing animals. The information generated by these research trials will be compiled into a series of best-management practices and disseminated via presentations, and extension and journal publications to producers and the scientific community. All animal studies will be conducted under veterinary supervision, and protocols will be approved in advance by the IACUC at the University of Hawaii and Utah State University (for USDA-ARS, PPRL work).