Those crop estimates are quite high, I know my land its a lot lower.
My family of 4 uses about 1/4 of a cow per year. We eat out too much so we should probably be more like 1/2. My parents never raised anything else, my grandparents had pigs and chickens but it was before I started school that my grandmother had them, I can just barely remember walking out with her to the chicken coop and getting an egg for breakfast. I remember one year her burning the hairs off a whole chicken after they plucked it.
My father bought a corn picker and combine, we did 10 acres of corn and oats and ground it up for grain for the cattle for the winter. Had at most 3 dozen head of cattle.