Tickets
Sell the squares in advance. Have an image of the mapped-out field to hand out after a person purchases a square. People can mark the squares they bought, to keep track. Create a large poster board of the available squares for purchase. Write purchasers&' names in the squares they purchase. It is important to keep good records.
Rules
Designate line judges to keep an eye on the animal and the spectators during the contest. Have guidelines in place for how the organization will handle it if the cow deposits across two or more squares or on a line. For example, the winnings could be split between the people who purchased those squares.
Alternatives
Groups without access to a cow can use smaller animals, such as goats or dogs. Use a small penned-in area and be sure the animal is well-fed before starting the contest.
You can also conduct this fundraiser during a parade event. Raffle off sections of the parade route ahead of time. If one of the horses in the parade leaves a deposit on your section, you win. Solicit prizes for this version from businesses in the town.
Entertainment
Groups can tie this fundraiser in with a larger event, such as a music festival or carnival. Sell drinks or host a bake sale or craft show to keep people engaged while they wait to see if they are winners.
Prize
You have several prize options with this type of fundraiser. Give the winner a percentage of the total proceeds, or give away donated items from local businesses.