in winter i chuck a rabbit in with my four and refeed when its gone usually a day with dry i keep them topped up on the stuff in the summer then they allways have some food to go at but they can put weight on with it if they do then they are on there leads and marching the streets soon gets them fit and healthy lol.
as for fleas and ticks i treat as i find no point in spending money on stuff if not needed also dont like dosing the ferrets withs chems for the sake of it, so i dose when i need to also get yourself a good tick puller in advance the otom ones are the best and a doddle to use f