Would fencing be a part of eligible costs if it is included to protect the irrigation system from cattle/animals?

If this is for 1804, it’s about the irrigation system, and fencing isn’t part of the irrigation equipment. 0903 (dams) and 0904 (dugouts) include fencing as eligible costs due to safety issues, e.g., to prevent people/animals from falling into the dam/dugouts.

Fencing is generally part of building the dam/dugout (similar to building fencing around your house or building railings for your balcony. However, fencing is not required (and is unconventional) for irrigation systems (1804) or rainwater harvesting (0905).

If fencing is identified as an action item in your EFP plan, IAF recommends applying for funding under BMP codes 1003, 1005, or 2209.