I think to compare a homestead-scale operation where you have a cow or two on less acreage than you'd prefer, one acre for two head rather than two acres for one head, is somewhat, if not misleading, certainly obfuscating; feed lots are terrible, but two cows on an acre, even with a calf each, isn't the same as a CAFO.
In that scenario, while the timing would be tight, and there would probably be need for a sacrificial paddock, there's more than enough room for a cow to exhibit a full range of cowish behaviour, especially if they don't get up to tonne-weight like some animals bred for meat.
I also think that the quality of the pasture needs to be taken into account. A healthy pasture growing in living soil will outcompete degraded pasture on poor soil. Theoretically, healthier pasture means fewer mouthfuls for the same nutrition, meaning less walking and chewing required, suggesting that healthier pasture will translate to more weight put on per mouthful.
Less ranging also means that it would take longer for them to graze a pasture, leaving more time for regenerating paddocks.
And let's not forget we're talking about dexters, here. These aren't South Devons, here, nor even Charolais.
One idea that could be looked into is the current state of affairs concerning mini-cattle. The last I checked (maybe a decade ago), there was a mini-dexter, or a mini half-dexter, bred down using traditional breeding and animal husbandry to produce a dual purpose meat and milker that would thrive at two head to an acre.
Personally, when I move out of the
city, while it definitely won't be the first thing I do, nor even the first dairy animals I purchase, I would love to have a couple of mini-Jerseys, just for the milk and cream. Apparently, the minis produce a greater amount of milk per pound of animal than the standard beasts, without a loss in milk quality.
And keep in mind that, properly managed, you will be improving your pasture by running cattle on it, meaning that the amount and/or quality of vegetation that pasture can sustain will increase.
But let us know how you do, and good luck.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein