An everything farm is a farm which chooses diversification over specialization as an organizing principle for their production. Everything farms pursue economies of scope rather than economies of scale as the economic model for their success as a business enterprise.
Also called an "Old MacDonald Farm" because of the diversity of animals and crops found there, everything farms used to be the norm for farms everywhere before the era of agro-industrial specialization.
Because they are not specialized, everything farms do not rely on economies of scale for success and therefore to not need to be large to be productive, but they must rely on effective marketing in their local area to be economically viable. In developed countries, frequently everything farms are aimed toward self-sufficiency in some aspects of food production.
The various species and products of an everything farm can be thought of as "programs" within the overall activity of the farm and each must contribute value in some way to the success of the farm.