The answers are B and F.

Blank (i) focuses on the availability or quantity of livestock:
B. paucity: This word accurately conveys the idea of a scarcity or insufficiency of livestock. A "paucity" of livestock suggests that there isn't enough of them available for the farmers' needs.

Blank (ii) deals with the availability or quantity of corn:
F. surfeit: This term signifies an excess or abundance of something. In this context, a "surfeit" of corn implies that there's an excessive amount or surplus of corn available to the farmers.

This contrast between the scarcity of livestock and the surplus of corn leads the farmers to redirect their corn supply, prioritizing its use for biofuel production rather than as feed for the limited livestock available.

Therefore, considering these contextual factors, the words "paucity" and "surfeit" best fit the blanks in the sentence to convey the contrasting availability of livestock and corn, leading to the farmers' decision.