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Effect of Medusahead on beef cattle gains

Principal Investigator: Jeremy James

Rangeland weed control is widely viewed and promoted as central to enhancing ranch profitability and sustainability. In most cases, this perspective is based on the untested assumption that reducing weeds will increase livestock gains. Because most rangelands in California are privately owned and management inputs are made by private decision makers, it is essential that we establish the direct economic impacts of weeds on profits.

The broad goal of this study is to determine if the most common and widely distributed rangeland weed in California (medusahead) negatively affects steer weight gains.

Over our first three project years, we experimentally manipulated vegetation in 13.5 acre paddocks to create a gradient in medusahead cover, resulting in pastures that now vary in medusahead cover between approximately 5% and 85%, with corresponding pasture production in March 2016 ranging between 556 to 1868 lbs per acre. Following these manipulations, we began our first year of grazing in spring 2016.

The goal with this project continuation is to repeat grazing over at least two more years to give us at least 39 experimental units (pastures) that vary in both forage production and forage composition.

This first grazing year is still ongoing, limiting the statistical statements we can make about year one.

Once the three grazing years are complete we will use a linear modeling approach to create a yield loss function, allowing us to assess the independent effects of these factors on steer gains. These functions will be converted into a user-friendly on-line calculator that will allow estimates of medusahead impacts on gain to be estimated for a particular pasture.

Collectively, this project will complement the rigorous work on medusahead control already completed by UC researchers and provide land managers the essential information needed to create cost/benefit estimates for these established control practices.

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