Even if feral cats seem like the zany and distant cousins of tame house cats, the reality is both types of felines are biologically the same. When it comes to weaning a wee feral kitten off her mama's milk, she will probably be ready to start around her fourth week.
Feral vs. Tame
In terms of temperament, feral and tame cats are like night and day. However, the cats are biologically the same, and therefore should be weaned around the same time. In terms of basic nutritional needs, a litter of kittens born to a feral queen is no different than one born to a domesticated house cat.
The ASPCA indicates that up until a kitten is about 1 month old, she has absolutely no dietary need for any sustenance other than mama's good old milk. Until a kitten reaches about 4 weeks old, all she needs in order to thrive and grow is provided in full through nursing.
The ASPCA states that the weaning process, which is typically initiated by the mother, generally starts around four weeks. The whole procedure is slow-moving, however, and a queen cat may continue to nurse casually until the kitten is about 2 months old -- often for soothing purposes. At this late stage, however, the kitten should be consuming mostly kitten-specific dry and wet food, rather than the mother cat's milk.
Socializing feral kittens is significantly easier than socializing feral adults. According to Alley Cat Allies, if a kitten is 8 weeks old or younger, the taming process is often very straightforward and quick. When a kitty is any older, the process, though often difficult, is indeed usually possible with some patience, determination and time. If you are rearing a kitten while her feral mother resides elsewhere, for example, you should consider either getting a "foster" mother cat to nurse the little one, or use a commercial kitten milk replacer, often known simply as "KMR." If you do feed the kitty using a KMR, do so until roughly four weeks -- the same time her mama cat would likely start weaning her. Around four weeks, slowly but surely begin feeding the newbie solid foods.