We define the boundary of a livestock farm in terms of corn production as the percentage of homegrown corn in total corn required. A new theoretical model is proposed that explains how farm boundaries are shaped by the relative efficiency of two alternative transaction-facilitating mechanisms: market and hierarchy. Using tax filer data from swine farms in Ontario, this article analyzes the impact that mechanism efficiency has on farm boundaries. To identify the potential causal effect, the USD/CAD exchange rate is used as the instrumental variable for corn price in Ontario. The findings support the theoretical model: in-house corn production expands due to not only higher price but also higher price volatility. The potential causal relationship we identified flowing from mechanism efficiency to farm boundary may shed light on why swine and other livestock industries are shifting towards non-market arrangements.