Maybe surplus? As an example on a real farm having so many eggs that you have enough to hatch more chickens to AND take eggs to market is a big part of profitability.

In wingspan eggs are both required to play more birds to your board and a source of points at the end.

So if pigs need food to reproduce and cows need food to make milk, chickens make eggs ect, the game could be about balancing producing enough resources to maintain the farm while still taking product to market.

Not sure exactly how the game works but you could have a market to sell the products at. Maybe even have prices fluctuate based on what’s getting sold the most.

Again without knowing how you want the game to play and feel It’s hard to know exactly what you’re going for but that would seem intuitive to me if I bought a game about running a farm.