Wifezilla
Low-Carb Queen - RIP: 1963-2021
While they can be big enough at 4 months, they fill out a lot more 5-6 months. Butchering ducks has a lot to do with timing. You want to catch them when they aren't developing those pin feathers that are hard to get plucked out.i have it in my head that ducks should be butchered at 4 months...
From what I have read, your pin feather free windows are at 7, 12.5 and 18 weeks.
Now as for ducks with your other critters, it totally depends. I think climate should be your guide. If you are in a dry area, a ducks mess is easier to manage. I have actually been thinking about getting a few chickens to add to my flock of ducks so they can stir up the bedding in the run
Ducks are messy, but everything dries out pretty fast around here so no biggie.
If I lived in a humid area with lots of rain....oh heck no. We had a couple of weeks last year where it rained non stop. The ducks loved it but WOW. What a mess in the run. Any chickens would have been miserable.
As for disease, not sure. I know more about not putting ducks with quail because you might get the quail sick. Actually you aren't supposed to raise quail with chickens either and I think it is cocci. Chickens can live with it but the quail have no immunity and die horribly.